[Index]
Monthly Global Tropical Cyclone Summary August 2007
[Summaries and Track Data] [Prepared by Gary Padgett]
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Monthly Global Tropical Cyclone Summary August 2007 [Summaries and Track Data] [Prepared by Gary Padgett] |
MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
AUGUST, 2007
(For general comments about the nature of these summaries, as well as
information on how to download the tabular cyclone track files, see
the Author's Note at the end of this summary.)
*************************************************************************
AUGUST HIGHLIGHTS
--> Destructive hurricane strikes Windward Islands, Jamaica and Mexico
--> Weak tropical storm remnants re-intensify hundreds of miles inland
over Oklahoma
--> Major hurricane threatens Hawaii
--> Weak tropical storm brings flooding rains to Vietnam
--> Typhoon strikes Taiwan and Chinese mainland
--> Typhoon strikes Japan near Tokyo
*************************************************************************
WIKIPEDIA TROPICAL CYCLONE REPORTS
Short reports with satellite pictures and small-scale maps for all
tropical cyclones may be found at the following links:
http://en.wikipedia.org/wiki/2007_Atlantic_hurricane_season>
http://en.wikipedia.org/wiki/2007_Pacific_hurricane_season>
http://en.wikipedia.org/wiki/2007_Pacific_typhoon_season>
http://en.wikipedia.org/wiki/2007_North_Indian_cyclone_season>
http://en.wikipedia.org/wiki/2007-08_Southern_Hemisphere_tropical_cyclone_season>
For some storms more detailed reports have been prepared. In those cases
I will include the specific links in the reports for the applicable
tropical cyclones.
*************************************************************************
!!!!!!!!!!!! EXTRA FEATURE !!!!!!!!!!!!
HISTORY OF THE NAMING OF ATLANTIC TROPICAL CYCLONES
PART 2 - THE SENSATIONAL SIXTIES
A. Introduction
---------------
This is the second in a series of monthly features detailing the
history of the naming of tropical cyclones in the Atlantic basin. The
early history of hurricane naming as well as the complete sets of names
used during the decade of the 1950s may be found in the July summary.
This month's article describes the 1960s and includes the sets of names
for the period 1960-1970.
In 1960 forecasters opted to begin rotating names in a regular
fashion, and so four alphabetical sets were established to be repeated
every four years. These new sets followed the example of the Western
Pacific typhoon sets and excluded names beginning with the letters
Q, U, X, Y and Z. However, the six-letter, two-syllable restriction
was apparently lifted, as names like FLORENCE and FRANCES were placed
into the sets. These four sets were used in the Atlantic until being
replaced by a 10-year list in 1971. Names of destructive hurricanes
were retired and replaced with names of the same alphabetical rank.
Thus, DONNA from 1960 was replaced with DORA for 1964; CARLA, ESTHER,
and HATTIE were retired after 1961 and replaced with CAROL, ELENA, and
HOLLY for 1965; and although not particularly significant, DAISY from
1962 was replaced with DOROTHY for 1966.
Originally, the name HANNAH stood in the 1963 set, but at the last
minute was replaced with HELENA. This practice of last minute changes
to the sets became commonplace through the latter 1960s. I can
well remember that in almost every year from 1966 through 1969,
there were deviations from the advertised set. Part of this was due
to an attempt to remove all names which were duplicated in either the
Eastern or Western North Pacific lists. In the 1966 set FLOSSY
was replaced with FAITH, apparently not long before the season began.
The set for 1967 had originally been identical to the 1963 set except
that FLORA had been retired and replaced with FREDA, but as the season
progressed, what should have been CINDY, DEBRA, FREDA, GINNY and
HELENA instead turned out to be CHLOE, DORIA, FERN, GINGER and HEIDI.
Even more juggling of names occurred with the 1968 and 1969 sets.
In the 1968 set CANDY, DOLLY, HANNAH and ISABEL had been selected to
replace CLEO, DORA, HILDA and ISBELL from 1964. However, ISABEL was
removed to the 1970 list to replace INEZ (retired after the 1966 season),
and INGRID placed in the 1968 set. Also, ETHEL and FLORENCE were removed
and EDNA and FELICE substituted in. Then, apparently at the last
minute, FELICE was moved to the 1970 set to replace FAITH, and FRANCES
was moved from the 1969 set to the 1968 list with the unusual name
FRANCELIA being inserted into the 1969 set. I well remember being
totally surprised when the sixth storm of 1968 was named and it
turned out to be FRANCES instead of FELICE. And, even though not
likely at all to be called into use, WINNY was replaced with WESLEY in
the 1968 set, ostensibly since WINNIE was a typhoon name in use at the
time.
In the late spring of 1969 I wrote NHC and requested a copy of the
latest brochure which contained all the Atlantic and North Pacific
names. From it I learned that BETSY from 1965 had been replaced with
BLANCHE; ELENA had been replaced with EVE; and of course that the
sixth name was now FRANCELIA. However, the third name in the
printed list was CAROL, but it was scratched through and CAMILLE
penciled in. This was apparently a last minute change, but one which
proved to be very fortuitous in the annals of Atlantic hurricane
history. If this change had not been made, there would have been two
very famous and destructive hurricanes named CAROL to keep straight.
(Incidentally, the name CINDY was chosen to replace CAMILLE in the set
for 1973, but that set was never used again.)
B. Sources of Information
-------------------------
For the 1960s I actually didn't need to refer to any source.
Back in my teenage years I pretty much had a photographic memory, and
I memorized those sets of names so thoroughly that I can still today
quite confidently recall them. But back then the NWS had available
a little brochure called "The Naming of Hurricanes" which contained
all the Atlantic and North Pacific sets and was updated every couple
of years, and I would usually write and request a current copy every
2 or 3 years.
C. The Sets of Names
--------------------
ATLANTIC HURRICANE NAME SETS
1960 - 1970
(An asterisk follows names that were actually assigned to storms.
A number in parentheses following a name refers to a note following
the lists.)
1960 1961 1962 1963 1964 1965
---- ---- ---- ---- ---- ----
Abby * Anna * Alma * Arlene * Abby * Anna *
Brenda * Betsy * Becky * Beulah * Brenda * Betsy *
Cleo * Carla * Celia * Cindy * Cleo * Carol *
Donna * Debbie * Daisy * Debra * Dora * Debbie *
Ethel * Esther * Ella * Edith * Ethel * Elena *
Florence * Frances * Flossy Flora * Florence * Frances
Gladys Gerda * Greta Ginny * Gladys * Gerda
Hilda Hattie * Hallie Helena * Hilda * Holly
Isbell Inga * Inez Irene Isbell * Inga
Janet Jenny * Judith Janice Janet Jenny
Katy Kara Kendra Kristy Katy Kara
Lila Laurie Lois Laura Lila Laurie
Molly Martha Marsha Margo Molly Martha
Nita Netty Noreen Nona Nita Netty
Odette Orva Orpha Orchid Odette Orva
Paula Peggy Patty Portia Paula Peggy
Roxie Rhoda Rena Rachel Roxie Rhoda
Stella Sadie Sherry Sandra Stella Sadie
Trudy Tanya Thora Terese Trudy Tanya
Vesta Virgy Vicky Verna Vesta Virgy
Winny Wenda Wilna Wallis Winny Wenda
1966 1967 1968 1969 1970
---- ---- ---- ---- ----
Alma * Arlene * Abby * Anna * Alma *
Becky * Beulah * Brenda * Blanche * Becky *
Celia * Chloe * Candy * Camille * Celia *
Dorothy * Doria * Dolly * Debbie * Dorothy *
Ella * Edith * Edna * Eve * Ella *
Faith * Fern * Frances * Francelia * Felice *
Greta * Ginger * Gladys * Gerda * Greta *
Hallie * Heidi * Hannah Holly * Hallie
Inez * Irene Ingrid Inga * Isabel
Judith * Janice Janet Jenny * Judith
Kendra * (1) Kristy Katy Kara * Kendra
Lois * Laura Lila Laurie * Lois
Marsha Margo Molly Martha * Marsha
Noreen Nona Nita Netty Noreen
Orpha Orchid Odette Orva Orpha
Patty Portia Paula Peggy Patty
Rena Rachel Roxie Rhoda Rena
Sherry Sandra Stella Sadie Sherry
Thora Terese Trudy Tanya Thora
Vicky Verna Vesta Virgy Vicky
Wilna Wallis Wesley Wenda Wilna
Notes:
(1) During a post-season data analysis, it was determined that Tropical
Storm Kendra had not met the minimum requirements for a tropical
storm and currently is not included in the HURDAT database.
*************************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for August: 1 tropical depression **
2 tropical storms ++
1 intense hurricane
** - system became an intense hurricane in September
++ - one of these formed in July and became extratropical on 1 August
Sources of Information
----------------------
Most of the information presented below was obtained from the
various tropical cyclone products issued by the Tropical Prediction
Center/National Hurricane Center (TPC/NHC) in Miami, Florida:
discussions, public advisories, forecast/advisories, tropical weather
outlooks, special tropical disturbance statements, etc. Some
additional information may have been gleaned from the monthly
summaries prepared by the hurricane specialists and available on
TPC/NHC's website. All references to sustained winds imply a
1-minute averaging period unless otherwise noted.
Atlantic Tropical Activity for August
-------------------------------------
Over the period 1950-2006, the averages for August are 2.8 NS, 1.6 H,
and 0.6 IH. Based on numbers of storms, August, 2007, was slightly below
normal with 2 NS and 1 H. The hurricane, however, was an intense and
far-traveled Category 5 storm, so the average level of tropical cyclone
activity for August was near normal. As the month of August opened,
Tropical Storm Chantal, which had formed on the last day of July, was
transforming into an extratropical storm as it crossed Newfoundland's
Avalon Peninsula, bringing very heavy rainfall. (The report on Chantal
may be found in the July summary.) During the first week of August,
a westward-moving tropical wave began to show some signs of developing
as it neared the Windward Islands. The disturbance, designated as
Invest 99L by NRL, was investigated by a USAF reconnaissance plane on
the afternoon of 1 August, but the plane was unable to find a closed
surface circulation. The system was investigated again the next day
when it exhibited greater organization than on the previous day, but
still a closed circulation could not be found. The wave continued to
move rapidly across the Caribbean and by the 4th was moving inland into
Central America.
The two named storms of August both formed near mid-month. Hurricane
Dean formed in the eastern Atlantic, a true Cape Verde hurricane, and
sailed westward on a remarkably straight trajectory which carried it
through the Windward Islands, across the Caribbean passing just south
of Jamaica, into the southern Yucatan Peninsula, and finally into
the Gulf Coast of Mexico north of Veracruz. Dean had reached Category 2
levels by the time it squeezed into the eastern Caribbean between the
islands of Martinique and St. Lucia, and eventually became an intense
Category 5 hurricane just prior to striking the Yucatan Peninsula. The
906-mb CP measured just before landfall ranks Dean as the 9th most
intense Atlantic hurricane on record as measured by central pressure.
Also around mid-month, Tropical Storm Erin blossomed briefly in the
central Gulf of Mexico but never strengthened beyond minimal tropical
storm intensity. The storm weakened to a tropical depression as it
was making landfall in Texas, and the remnants wandered over central and
western Texas, dumping copious amounts of moisture while maintaining
a fairly well-defined circulation. During the early morning of the 19th,
as the system was moving over Oklahoma, it suddenly re-intensified to
sustained tropical storm intensity, producing gusts above hurricane
force and sporting a well-defined radar eye reminiscent of a hurricane.
Just how this surprise last hurrah of Erin will be treated in the Best
Track database remains to be seen. Reports follow on both Dean and Erin.
Also following is a short report on a system southeast of the New England
coast at the end of August which displayed some features suggesting that
it could possibly have been a short-lived tropical storm.
Another westward-moving tropical wave spawned a tropical depression
on the final day of August just east of the Windward Islands. This
system strengthened into Tropical Storm Felix on 1 September and within
two days was another intense Category 5 cyclone traversing the Caribbean
on its way to a Nicaraguan landfall. Felix will be covered in the
September summary.
NOTE: The official TPC/NHC storm reports are already available online
for many of the 2007 Atlantic tropical cyclones, although not for
Dean and Erin. Links to the individual reports may be found at the
following URL:
http://www.nhc.noaa.gov/2007atlan.shtml>
HURRICANE DEAN
(TC-04)
13 - 23 August
----------------------------------
A. Introduction and Synoptic History
------------------------------------
Hurricane Dean was the first hurricane of the 2007 Atlantic season
and became the first landfalling Category 5 hurricane in the Atlantic
basin since Hurricane Andrew in August, 1992. Dean left a trail of
death and destruction across the Caribbean from the Windward Islands
to Mexico. The storm's minimum central pressure of 906 mb ranks it as
the ninth most intense Atlantic hurricane in history as measured by
central pressure.
A tropical wave which exited the western coast of Africa during the
second week of August immediately began to show signs of development.
A low-pressure area formed in association with the wave on 12 August and
by the next day had become organized sufficiently that advisories were
initiated on Tropical Depression 04, located a few hundred miles west-
southwest of the Cape Verde Islands. Tropical Storm Dean was
christened on the 14th while located about 1300 nm east of the Lesser
Antilles, and the cyclone continued to strengthen as it moved fairly
rapidly westward under the influence of a well-defined ridge to the
north. Easterly shear hampered the intensification process a little,
but did not prevent Dean from strengthening. Hurricane intensity was
reached on 16 August with the storm centered about 435 nm east of
Barbados. During the morning of 17 August the center of Hurricane Dean
passed between the islands of St. Lucia and Martinique with the northern
eyewall passing over Martinique with a MSW of 85 kts--a Category 2
hurricane on the Saffir/Simpson scale. Dean was the first tropical
cyclone to bring full hurricane-force winds to Martinique since Hurricane
David in 1979, and the first to bring hurricane winds to St. Lucia since
Hurricane Allen in 1980.
After passing through the Lesser Antilles Dean continued to move on a
slightly north-of-due-west track through the eastern Caribbean Sea.
Intensification continued, with Dean reaching Category 3 intensity by
early afternoon on the 17th and Category 4 status during the evening.
Winds reached 130 kts early on the 18th with Dean located about 600 nm
east-southeast of Jamaica. The center of the intense storm passed about
20 nm south of the southernmost point of Jamaica during the evening of
19 August with the MSW estimated at 125 kts. As Dean continued on its
remarkably constant heading across the deep warm waters of the north-
western Caribbean, the storm began to deepen once again and the cyclone
became a Category 5 hurricane very early on 21 August about 175 nm east
of Chetumal, Mexico. Intense Hurricane Dean reached its peak intensity
of 145 kts with an attendant CP of 906 mb just before making landfall
near Costa Maya on the Yucatan Peninsula, becoming the first Category 5
hurricane to strike the Yucatan since Hurricane Gilbert in 1988.
While crossing the Yucantan Peninsula, Dean weakened to a Category 1
hurricane and emerged into the Bay of Campeche late on 21 August. As
Dean moved west-northwestward across the southwestern Gulf of Mexico,
it began to re-organize and managed to reach Category 2 status with
winds of 85 kts just prior to making its final landfall about 65 km
south of Tuxpan, Mexico, around midday on 22 August. Once inland the
cyclone began to weaken quickly and the LLCC dissipated early on the
23rd over the mountainous terrain of central Mexico. A weak LOW later
reached the Eastern Pacific but did not show any signs of redevelopment.
The above synoptic history of Hurricane Dean is largely taken from
the monthly summary prepared by the Hurricane Specialists at TPC/NHC.
A very thorough and detailed report on the storm may be found at the
following link:
http://en.wikipedia.org/wiki/Hurricane_Dean_%282007%29>
B. Storm Impacts
----------------
The Wikipedia report on Dean has extensive information on the
impacts of this great hurricane across the Caribbean, so only a
brief synopsis gleaned from the Wikipedia report will be given here.
In the Lesser Antilles Dean caused moderate damage on the islands
of St. Lucia, Martinique and Dominica where roads were washed out and
houses damaged. There were six fatalities in this area, where the
agriculture-based economies of the three islands, as well as that of
Guadeloupe, were significantly affected. Between 80 and 100% of the
banana crops were destroyed. No dollar estimates are currently
available.
In the Dominican Republic no strong winds were experienced as the
center of Dean passed about 145 nm south of Santo Domingo. However,
there was some flooding from heavy rainfalls. There were six deaths
attributed to the hurricane, all due to drowning. A 16-year old boy
was swept out to sea by heavy surf near Santo Domingo, and five
fishermen drowned in the northern province of Santiago after their
boat capsized due to the effects of wind and torrential rain on an
inland lake.
In Haiti the outer fringes of Hurricane Dean brought heavy squalls
and torrential rains, resulting in power outages and landslides. Several
hundred homes were destroyed by the landslides, and there were eleven
fatalities attributed to the storm in Haiti.
Jamaica was much more adversely affected by Hurricane Dean as the
northern eyewall just missed the island while at Category 4 intensity.
Fortunately, only three lives were reported lost due to the storm.
Damage to agriculture was widespread with 40% of the sugarcane crop,
80-100% of the banana crop, 75% of coffee trees under three years old,
and 20% of the top layer of the cocoa crop were lost. Total damage
in Jamaica has been estimated at around US$4.9 billion.
In Mexico, the town of Majahual (population 200) near where the center
of Dean made landfall was reportedly "almost flattened" by the storm.
Storm surge and high winds severely damaged or destroyed hundreds of
buildings. A least fifteen deaths have been reported in Mexico due to
Hurricane Dean. Several of the deaths were due to mudslides triggered
by the heavy rains. Total storm damage in Mexico is estimated to be
at least US$800 million.
Some damage was reported from Belize, mainly to buildings and houses
in Corozal and Orange Walk. Also, the sugar and papaya industries were
affected. Some minor effects of the storm were felt in Cuba, and in
the Cayman Islands there were some rain-flooded roads and localized
power outages, but there were no deaths or serious injuries reported.
No land impacts of Dean were felt in the United States, but the storm
caused heavy surf and rip currents along Florida beaches, leading to
one drowning near Siesta Key. After reaching the Pacific, the remnants
of Dean eventually moved inland near Santa Barbara, California, bringing
heavy thunderstorms and localized flooding to coastal Southern California
on the morning of 26 August. The system crossed the Mojave Desert on the
morning of the 27th, with Las Vegas, Nevada, receiving a new daily
record rainfall of 14.7 mm, leading to some flash flooding and minor
damage.
C. Discussion of Dean's Peak Intensity
--------------------------------------
The 906-mb central pressure reading obtained by dropsonde shortly
before landfall on 21 August ranks as the ninth lowest minimum central
pressure measured in an Atlantic hurricane. The lower minimum central
pressures are:
905 mb - Camille (17 August 1969)
905 mb - Mitch (26 October 1998)
902 mb - Katrina (28 August 2005)
899 mb - Allen (7 August 1980)
895 mb - Rita (22 September 2005)
892 mb - Labor Day Hurricane (3 September 1935)
888 mb - Gilbert (14 September 1988)
882 mb - Wilma (19 October 2005)
Before focusing on Dean's peak intensity, it would be worthwhile to
look at the storm's first round of significant strengthening on 18 and
19 August. Between 18/0000 and 18/0600 UTC Dean's CP fell 16 mb from
946 mb to 930 mb with the MSW being raised from 115 kts to 130 kts.
The MSW of 130 kts was well-supported by a peak FLW of 145 kts at
18/1148 UTC. The CP leveled off at 930 mb for several hours, then began
to drop again during the evening. Interestingly, the storm showed signs
of slight weakening during this time due to structural changes in the
inner core. The NHC discussion for 19/0300 UTC noted that radar imagery
onboard the USAF reconnaissance aircraft depicted concentric eyewalls at
radii of about 10 and 20 nm with the outer eyewall becoming a little
better defined. Wind data at flight level, from the SFMR, and from
dropsondes directly supported an intensity of no more than about 115 kts.
However, the CP had continued to drop and a reading of 918 mb was taken
at 19/0105 UTC with a peak FLW of 123 kts in the northwest quadrant at
19/0111 UTC. It light of all this, the assumption was made that the
maximum wind had not been sampled and the MSW was lowered to 125 kts, but
the forecaster commented that this was perhaps generous.
Dean's MSW remained at 125 kts for a period of 24 hours. It was upped
back to 130 kts at 20/0600 UTC. The most recent observations from a
Hurricane Hunters reconnaissance aircraft indicated a concentric eyewall
structure with a peak FLW of 145 kts and a SFMR surface wind measurement
of 125 kts in the northeast quadrant. A GPS dropsonde measured a surface
wind of 133 kts in the same quadrant, but based on lower-layer averages
from the dropsonde, it was felt that the reading didn't quite correspond
to a 1-min avg surface wind. The storm's CP at this time had fallen to
926 mb after having risen to 930 mb during the morning of the 19th.
During the morning of 20 August microwave imagery revealed that Dean
had a single eyewall which had become better defined with colder cloud
tops. Communications problems prevented much of the data from the
early afternoon reconnaissance mission from being received, but a
20/1930 UTC vortex fix was received, reporting a CP of 918 mb with a
maximum FLW of 151 kts. Earlier in the flight a peak SFMR wind of
123 kts was observed, and Dvorak classifications from TAFB and SAB were
127 kts at 1800 UTC. Based on all this, the MSW was held at 130 kts.
A reconnaissance plane at 21/0000 UTC reported a CP of 914 mb with a
peak FLW of 162 kts, which would correspond to a surface MSW of 145 kts.
Due to continuing communications problems, much of the SFMR and drop-
sonde data was not being received in real time. The 21/0000 UTC
intermediate advisory upped the MSW to 135 kts, but based on the 0000
UTC reconnaissance report, an update was issued at 21/0035 UTC, raising
the MSW to 140 kts, making Dean a Category 5 hurricane on the Saffir/
Simpson scale.
Hurricane Dean made landfall on the east coast of the Yucatan
Peninsula near the cruise ship port of Costa Maya around 0830 UTC.
Observations from a USAF reconnaissance plane indicated that Dean was
intensifying right up to the moment of landfall. A peak FLW of 165 kts
was measured just north of the eye. The maximum SFMR wind was only
124 kts, but it was considered highly likely that the maximum surface
wind speed was not reported by the SFMR instrument. A GPS dropsonde
in the northern eyewall measured a wind speed of 178 kts averaged over
the lowest 150 meters of the sounding. Taking all of the wind data into
consideration, the peak MSW at landfall was estimated to be 145 kts.
The 906-mb CP reading was made by a dropsonde in the eye just prior to
landfall.
As noted above, Hurricane Dean represented the first Category 5
hurricane landfall in the Atlantic basin since Hurricane Andrew slammed
into southeastern Florida on 24 August 1992. Dean was the first
Category 5 hurricane to strike the Yucatan Peninsula since Hurricane
Gilbert made landfall on 14 September 1988 with a CP of 900 mb and an
estimated MSW of 140 kts.
(Report written by Gary Padgett)
TROPICAL STORM ERIN
(TC-04)
15 - 19 August
---------------------------------------
A. Synoptic History
-------------------
The origins of Tropical Storm Erin seem to lie with the interaction
between a tropical wave and an upper-level LOW which produced a large
area of thunderstorm activity over the western Caribbean Sea and
extending into the central Bahamas. Unfavorable upper-level winds
gradually lessened and by 13 August a broad area of low pressure
had formed near the northeastern Yucatan Peninsula. By the next day
the system had entered the southern Gulf of Mexico and was showing
increased organization. The area was investigated during the
afternoon by a reconnaissance flight, but at that point did not
yet have a well-defined circulation center and so was not classified as
a tropical depression. However, during the evening convection began to
increase in coverage so advisories were initiated on the season's 4th
tropical depression at 15/0300 UTC with the center located about 370 nm
east-southeast of Brownsville, Texas, moving northwestward at 8 kts with
the MSW estimated at 25 kts.
The depression was upgraded to Tropical Storm Erin in a special
advisory issued at 1530 UTC on the 15th, based on findings from a NOAA
Hurricane Hunter plane. At the time of its upgrade Erin was centered
about 175 nm east of Brownsville. Erin remained poorly-organized and
did not strengthen beyond 35 kts while over the Gulf. The center of
circulation made landfall near Lamar, Texas, on the morning of 16 August,
and by that time had weakened to a tropical depression with 30-kt winds.
The depression continued northwestward and inland during 16-17 August
and turned northward over western Texas on the 18th.
The circulation remained remarkably intact over land, and entered
southwestern Oklahoma very early on 19 August. While moving north-
eastward over Oklahoma that morning, the vortex underwent a most unusual
and unexpected intensification, producing sustained winds well in excess
of tropical storm intensity with gusts to hurricane force in isolated
locations. A post-analysis of this unusual event is ongoing to determine
the strength and status of Erin while over Oklahoma. The surface LLCC
of Erin dissipated later on the 19th over northeastern Oklahoma, but
remnant moisture continued northeastward into Missouri. Overall, Erin
and its remnants brought heavy rain to portions of Texas, Oklahoma and
Missouri. Storm-total rainfall amounts of 75-175 mm were common in
many of these areas with some locations receiving more than 250 mm.
The above synoptic history of Tropical Storm Erin was based largely
upon the monthly summary prepared by the Hurricane Specialists at NHC.
The Wikipedia report on Erin may be accessed at the following link:
http://en.wikipedia.org/wiki/Tropical_Storm_Erin_%282007%29>
B. Storm Impacts
----------------
The information in this section has been taken from the Wikipedia
report on Tropical Storm Erin.
(1) Texas
---------
Erin was weakening to a tropical depression as it made landfall in
Texas, so no strong winds were reported. The highest was an unofficial
report of a gust to 39 mph at Jamaica Beach. The system led to a minor
storm surge, peaking at 0.98 m at Pleasure Pier. Heavy rains fell near
and to the northeast of the path, reaching 280 mm at a station in
Lockwood. A total of eleven fatalities in Texas have been attributed
to Erin.
(2) Oklahoma
------------
The unexpected strengthening over Oklahoma led to widespread damage
with several communities in central Oklahoma being flooded due to heavy
rainfall. Winds in Watonga gusted as high as 71 kts, damaging numerous
trees and downing power lines and heavily damaging mobile homes. Six
deaths were attributed to Erin in Oklahoma with an additional fatality
in an automobile accident possibly being related to the storm.
(3) Missouri
------------
Although the surface circulation had dissipated before reaching
Missouri, the circulation aloft remained intact and led to a burst of
rainfall in Missouri early on 20 August. The 303.3 mm that fell at
Miller became the highest Missouri rainfall total associated with a
tropical cyclone or its remnants since at least 1976. One person in
the state died when he drove into flood waters which had swept away a
bridge he was attempting to cross.
The HPC report on Tropical Storm Erin with the associated rainfall
maps may be accessed at the following URL:
http://www.hpc.ncep.noaa.gov/tropical/rain/erin2007.html>
C. "Landphoon" Erin in Oklahoma
-------------------------------
The following discussion consists of three sections. First is the
description of a first-hand experience of Erin's re-intensification
by storm chaser Rocky Rascovich. Following this is an analysis of the
meteorological aspects of this most unexpected event by Roger Edwards,
a forecaster at NOAA's Storm Prediction Center in Norman, Oklahoma.
Finally, the third section looks at some political and meteorological
issues precipitated by Erin's very unusual and unexpected strengthening
several hundred miles inland three days after leaving the warm,
nourishing waters of the Gulf of Mexico. (A special thanks to Roger
and Rocky for permission to use their comments here.)
(1) Experiences of Rocky Rascovich
----------------------------------
�I think I may have witnessed one of the most unusual weather events
in recent times--right here at my farm in Piedmont, OK.
�The remnants of TS Erin (which if you remember was downgraded to
a depression last Wednesday morning just after it crossed the TX coast
near Corpus Christi, then spun itself through the hill country,
then on toward Childress yesterday, with the circulation still intact but
with winds generally 25 mph or less), decided, quite magically through
the ever mysterious processes of our atmosphere, to rapidly increase
in strength starting last evening. Several tornado reports came in from
SW Oklahoma, then around midnight, the wind gradually started picking up
here at the farm. Probably around 10-20 mph from the east. Lightning
was flickering frequently across the southern and western horizons. We
had a few bands of rain come through earlier, starting in the mid-
afternoon. In fact I saw one storm come over downtown OK City that had
exhibited some nice banding and inflow cloud spikes in the mid levels at
around 5pm.
�Cutting to the "chase", the real action got underway around 1:30am
with considerable cloud-to-ground lightning (cg) activity near the house
along with 15-30 mph winds that backed more from SE to E. At around 3am,
I was in bed and Dee alerted me that a TOR warning was issued for
Canadian County (my home county west of OKC). At that time, winds still
weren't that bad but were increasing and cg activity was ramping up
again.
�A short time later, maybe around 3:15am, I could hear the skylights
in my bathroom whistling and lots of commotion going on. I got up,
naturally, and lo and behold, it was mayhem happening, winds sustained
at least 50 mph, gusts over 60 right out of the east, and a profuse
amount of rain wildly whipping by. Lightning activity was still there
but was happening much less frequently.
�This continued unabated and actually increased as the minutes went
by. Between 4 and 4:45am was the peak of the storm. Winds were rarely
less than 40 mph, most of the time sustained at least around 50-55 mph,
peak gusts I estimated were around 65 mph with 70 mph not out of the
question. Wind direction for the most part was close to due east, maybe
a little ENE at times. Rain was coming down approximately 2-3" per hour.
�Starting around 4:45am, winds suddenly abated to around 20 mph or so
but a couple of times, a period of a minute or two, winds would suddenly
increase to around 40-45 mph out of the E/ESE. Interestingly, the gusts
were not accompanied by any increase of rain, when the sudden wind
surges hit, the rain at that time was generally light.
�At 5am, our winds came down to less than 15 mph, the rain temporarily
lessened to a drizzle, we were in the "eye" of this storm. I was glued
to KWTV Ch. 9 (other channels were not coming in), my satellite TV
was out and the internet went down, so I was only able to see the radar
through the TV. I soon afterward went back to bed, awoke briefly around
6:30am to strong S or SW winds and rain again, and a fair amount of
lightning. Conditions gradually improved after 7am.
�To me, this was a shock and awe moment, trying to figure out how this
storm could actually strengthen, close to 72 hours after landfall, way
up here in Oklahoma. My guess is that it tapped into a theta-E rich
low-level jet that was juxtaposed perfectly to feed into the remnant
centre of the storm, thus giving it that boost.
�Temps and dewpoints were already reminiscent of that of the tropics
to begin with, so it had that to feed off of, too.�
(2) Analysis by Roger Edwards
-----------------------------
�This is just an educated guess at the moment based on my experience
with tropical and mid-latitude systems, and most of all, preliminary
examination of satellite, surface, upper air and radar data so far. But
I have some thoughts on why this system acted the way it did on its
third night inland.
�First of all, Erin itself still was about as unquestionably warm
core as can be; the 500-mb analysis from 0000Z the previous evening
clearly shows a SSW-NNE thermal *ridge* of -2 to -4 C temps with an
axis directly atop the low to mid-level center at that time. Temps
cooled away from Erin toward the E, N and W at 500 mb. (The 1200Z 500-mb
map is more poorly-sampled because the Norman sounding -- nearest the
center -- was convectively contaminated.) It was drawing in some dry
air aloft from the W, as evident in moisture channel imagery. No
significant low, middle or upper-level baroclinicity was evident except
for the usual, very mild variety generated by differential convective
latent heat release with any inland tropical system. I have no qualms,
therefore, about calling it tropical over Oklahoma; and since it was a
closed cyclone with an eye that produced *sustained* TS-force winds for
several hours, that leaves no other equally justified option on
classification: it was, once again, Tropical Storm Erin.
�Though it was warm-core and still tropical, Erin was indirectly
�feeling� the influence of a baroclinic system located many hundreds of
miles to its NW. Mid and upper troughing across the northwestern U.S.,
and the resultant enhancement of gradient winds aloft across the central
and northern Rockies, enabled lee-side surface troughing, as is very
common.
�Associated low-level height/pressure falls quite often boost the
development of a low-level jet (LLJ) east of the lee trough, over the
southern and central Great Plains. The other factor in LLJ development
and enhancement is vertical, nocturnal decoupling of the boundary layer
through diabatic surface cooling (more on this later), focusing the
core of strongest LLJ flow a km or two above the surface. The LLJ can
and quite often does reach well south of the latitude of any baroclinic
zones, surface or aloft.
�In my opinion, as well as that of a few others with whom I've
conversed, the distant height/pressure falls and their influence on the
low-level winds helped to "channel" the flow through the eastern
semicircle of Erin, where the system's own gradient winds could enhance
(not partially negate, as on the W side) the LLJ effect.
�Why not the previous nights? I believe Oklahoma's Erin finally had
reached a high enough latitude to experience such an indirect influence
(unlike the prior nights). Yet Erin still was slow-moving, trapped
between the two upper HIGH cells over the southeast and southwest U.S.,
and hadn't been "sheared apart" yet. In other words, it was caught in
just the right regime of weak flow aloft, but lee-side enhancement in
low levels, to wind up as it did.
�And because the low levels were so moist (dew points in the 70s and
temperatures just a few degrees higher), with moisture transport from
the south (including the Gulf and heavily rained-on areas of TX)
continuing, nocturnal cooling couldn't proceed very far. The boundary
layer stayed at least marginally unstable for an effective lifted parcel
and also didn't *fully* decouple.
�These two factors allowed intense, surface based, sometimes severe,
thunderstorms to develop, and also allowed LLJ winds aloft to mix
consistently down to the surface in that favored channel spiraling
inward from the SE semicircle. Also, as often is the case with nocturnal
tropical MCSs, the vertical lapse rate probably improved in a subtle
manner through differential latent heat releases, and storm tops got
very high and cold (per IR imagery) -- colder even than Hurricane Dean
in the Caribbean at that particular time.
�The minimum MSLP I was able to *confidently* analyze was at 0730Z
when the center was along the Blaine/Dewey County line, just SW of
Watonga, Oklahoma: 1000 mb. This was based on subjective analysis of
mesonet data; however it is possible that the pressure dipped to 999 mb
between stations. Unfortunately, OK Mesonet meteorograms available
online display absolute sfc pressure, not PMSL. I got PMSL conversion
of planar (mapped) OK mesonet obs through our display systems at SPC.
Oklahoma Jim may be able to get higher temporal resolution mesonet data
from Watonga with MSL reduction in order to more firmly establish minimum
pressure.
�Those cold cloud tops warmed considerably after 1000Z, convection
diminished in intensity, and the central pressure filled. The eye lost
definition after 1200Z. Convection and associated latent heat releases
waned. The LLJ weakened, as it often does around dawn. Those factors
don't deeply or fully explain why the storm weakened as quickly as it
had re-intensified earlier, but may offer hints in the right direction.
�We've got so much left to learn about Erin and its wild ways! I
don't envy Jack's having to translate anything resembling the above
for "public" consumption, because I don't believe a simple explanation
for this exists!�
(NOTE: Roger used the term 'meteorogram'. According to Derrick Herndon,
this term is synonymous with the more commonly-used 'meteogram'.)
(3) Additional Discussion
-------------------------
At the time of Erin's inland re-intensification, HPC was issuing
advisories on the system, as is normal for the inland remnants of
tropical cyclones which are still producing rains with the potential
for flash flooding. Some mild criticism was leveled at the agency for
not re-upgrading Erin to tropical storm intensity on the morning of
19 August. David Roth of HPC addressed this. Such action was considered
during the night, but the current operational policy is for HPC to only
issue tropical depression advisories after NHC has downgraded a system
from tropical storm status. Back in 2001, when ex-Tropical Storm
Allison began to re-intensify inland over Louisiana and Mississippi, NHC
asked HPC to refer to the system as a "gale center" because they did not
want the tropical storm title used on an inland system. Also, David
points out that only the field offices (WFOs) normally would issue inland
tropical storm warnings. NHC's charter is to provide warnings of
expected tropical storm and hurricane conditions at the coast.
At the moment, Erin's re-intensification to tropical storm strength
so far inland seems unique in the annals of Atlantic tropical cyclone
history. There have been a few tropical systems in recent years which
have re-intensified to gale force while the centers were over land, but
in all cases they were near the ocean. One case was the above-mentioned
Allison of 2001. After drenching Houston, Allison, as a tropical
depression, moved eastward off the Louisiana coast, turning to the
east-northeast, moving inland over southeastern Louisiana, and undergoing
a modest re-intensification to gale force. As noted earlier, at the
time warnings handled Allison as a "gale center", but in post-analysis
the system was re-analyzed as a subtropical storm.
Danny of 1997, Helene of 2000, and Gaston of 2004 were all tropical
cyclones which had made landfall in the U. S. (Danny and Helene along
the Gulf Coast, and Gaston in South Carolina) and as depressions were
moving northeastward across North Carolina toward the Chesapeake Bay
area. As all three approached the Atlantic they re-intensified to
tropical storm strength before the center reached the coastline, and
the Best Tracks file now shows each as having intensified back to
tropical storm status while still inland.
In 1970 Tropical Storm Felice made landfall in eastern Texas, thence
recurving northward into Oklahoma. A study done many years ago indicated
that ex-Felice underwent some redevelopment over Oklahoma with a radar
eye being present, but there is no evidence that winds to gale force
occurred. Also, it appears that Felice was in close proximity to a
baroclinic zone as it passed over Oklahoma, which was not the case with
Erin, so that situation may not be analogous to Erin.
How will Erin's re-intensification over Oklahoma be handled by NHC in
the Best Track database? The answer to that very interesting question
remains to be seen, so to borrow an expression a friend of mine in Puerto
Rico always uses to close his e-mails or postings�STAY TUNED.
(Report written by Gary Padgett, with contributions by Roger Edwards,
Rocky Rascovich and David Roth)
A Candidate for an Unnamed Tropical Storm?
(Invest 96L)
30 August - 1 September
------------------------------------------
A system with some affinities to the officially-added unnamed tropical
storm of July, 2006, formed off the mid-Atlantic coast in late August.
An e-mail was posted to a discussion group very early on 1 September by
Zach Gruskin, an intern at HRD, which follows (very slightly edited):
A. Comments by Zach Gruskin
---------------------------
An interesting low-pressure system paralleled the eastern seaboard of
the United States over the past 2 days, and was particularly interesting
over the past day. This LOW maintained a well-defined surface
circulation with organized convection from part of Thursday (30 Aug) and
into part of Friday (31 Aug), as can be seen in these 2 visible
satellite images:
http://i44.photobucket.com/albums/f34/abunter/96-4.jpg>
http://i44.photobucket.com/albums/f34/abunter/96-5.jpg>
I couldn't find a QUIKSCAT pass during the peak of the system,
unfortunately, but a pass as the system was losing convection revealed
winds of 40 kts in the NE quadrant. I would suspect winds were higher
during the peak organization of the system, and solidly minimal/moderate
tropical storm force. Below are the QUIKSCAT pass and a visible
satellite image of the system decaying into a tight swirl:
http://i44.photobucket.com/albums/f34/abunter/96-3.png>
http://i44.photobucket.com/albums/f34/abunter/96-6.jpg>
Also of note, 96L passed near Buoy 44004 while it was a tight swirl
(well after the storm's peak), and a wind surge of up to 22 kts with a
pressure drop down to 1007 mb was observed:
http://i44.photobucket.com/albums/f34/abunter/96-1.png>
As for the thermodynamic structure of the system, here are some AMSU
and FSU phase analysis charts. It looks warm core to me:
AMSU:
http://i44.photobucket.com/albums/f34/abunter/96-11.gif>
http://i44.photobucket.com/albums/f34/abunter/96-10.gif>
FSU phase analysis:
http://i44.photobucket.com/albums/f34/abunter/96-8.png>
http://i44.photobucket.com/albums/f34/abunter/96-9.png>
Overall, a fairly intriguing system, one that should be considered for
an upgrade to a tropical storm after the season. It reminds me a lot of
the unnamed tropical storm last year:
http://www.nhc.noaa.gov/pdf/TCR-AL502006_Unnamed.pdf>
B. Comments by Chris Fogarty
----------------------------
However, Chris Fogarty of the Canadian Hurricane Centre was not quite
so enthusiastic about the system's chances of being included as an
after-the-fact tropical storm. Some comments from Chris follow:
I worked our forecast desk for this storm as support meteorologist.
My conclusion about this storm system--and I think NHC would concur--is
that although there were gale-force winds, the cloud/convective mass
never did get co-located with the low-level circulation center. The CDO
never quite became co-located with the center at the surface. Shear
eventually stripped the convection from the vicinity of the LOW center
and moved NE to give what was a good shot of rain to Nova Scotia (2-5").
I do not at this time see this as a candidate for post-season addition.
C. Further Discussion
---------------------
Dr. Fogarty prepared a brief report on the system, which brought heavy
rainfalls of 50-130 mm to Nova Scotia. Actually, two surface LOW centers
developed, with the northern one becoming frontal and helping to bring
the heavy rains to Nova Scotia. Some flooding and road washouts occurred
in the Cape Breton area.
Following are tracks for the two LOWs prepared by Chris:
(1) Initial LLCC (identified as Invest 96L)
-------------------------------------------
Date Time Lat (N) Lon (W) CP (mb)
--------------------------------------------
30 Aug 1800Z 36.0 70.0 1010
31 Aug 0000Z 37.0 70.5 1009
31 Aug 0600Z 38.0 71.0 1009
31 Aug 1200Z 38.2 70.3 1004
31 Aug 1800Z 38.0 70.0 1006
01 Sep 0000Z 38.8 68.2 1006
01 Sep 0600Z 39.0 66.8 1008
Degenerated
(2) Northern LLCC which brought heavy rain to Nova Scotia
---------------------------------------------------------
Date Time Lat (N) Lon (W) CP (mb)
--------------------------------------------
31 Aug 1800Z 40.8 66.9 1010
01 Sep 0000Z 41.9 65.0 1008
01 Sep 0600Z 43.5 63.0 1006
01 Sep 1200Z 46.3 59.5 1001
01 Sep 1800Z 48.2 56.0 999
02 Sep 0000Z 48.7 53.1 999
Absorbed into front
A special thanks to Zach and Chris for the information they supplied and
for permission to include it in this report.
*************************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for August: 2 tropical storms
1 hurricane
1 intense hurricane
Sources of Information
----------------------
Most of the information presented below was obtained from the
various tropical cyclone products issued by the Tropical Prediction
Center/National Hurricane Center (TPC/NHC) in Miami, Florida (or the
Central Pacific Hurricane Center (CPHC) in Honolulu, Hawaii, for
locations west of longitude 140W): discussions, public advisories,
forecast/advisories, tropical weather outlooks, special tropical
disturbance statements, etc. Some additional information may have
been gleaned from the monthly summaries prepared by the hurricane
specialists and available on TPC/NHC's website. All references to
sustained winds imply a 1-minute averaging period unless otherwise
noted.
Northeast Pacific Tropical Activity for August
----------------------------------------------
In terms of the number of storms, August tropical cyclone activity
was very close to normal. Over the 1971-2006 period of record, the
averages for August are 4.1 NS, 2.4 H, and 1.1 IH. August of 2007
produced 4 NS, 2 H, and 1 IH--about as close to average as one can get.
Erick and Gil were short-lived minimal tropical storms southwest of the
Baja at the beginning and ending of the month, respectively. Hurricane
Flossie, the only major hurricane of the 2007 season, formed fairly
far to the west of the primary genesis region for Eastern North Pacific
cyclones. Once it had formed, Flossie intensified rather rapidly into
a Category 4 hurricane around the time it crossed 140W into the Central
North Pacific. The storm posed a significant threat to Hawaii as it
trekked in the direction of the Aloha State for several days while
maintaining itself as an intense hurricane. However, as Flossie began
to draw near the Big Island, vertical shear increased significantly,
leading to a very rapid weakening. At the close of the month, Tropical
Storm Henriette formed rather close to the Mexican coast and brought
heavy rainfall to coastal regions as it moved slowly west-northwestward
parallel to the coastline. Henriette turned to the north and reached
hurricane intensity shortly before moving onshore on the tip of the Baja
California Peninsula just east of Cabo San Lucas. The storm continued
northward, moving back into the Gulf of California, and maintained
hurricane intensity until it made a second landfall on the Mexican
mainland. Short reports on all four named storms follow.
NOTE: The official TPC/NHC storm reports are already available online
for Tropical Storms Erick and Gil, and for all earlier cyclones this
season. Links to the individual reports may be found at the following
URL:
http://www.nhc.noaa.gov/2007epac.shtml>
TROPICAL STORM ERICK
(TC-08E)
31 July - 2 August
----------------------------------------
Short-lived Tropical Storm Erick formed from a tropical wave which
entered the Eastern North Pacific on 23 July. The wave gradually
became better organized, forming a broad surface LOW by the 28th.
Convective activity gradually consolidated and by late on 31 July the
system had attained sufficient organization that advisories were
initiated on Tropical Depression 08E at 2100 UTC, locating the center
approximately 960 nm southwest of Cabo San Lucas. Six hours later the
depression was upgraded to Tropical Storm Erick with 35-kt winds. This
proved to be Erick's peak intensity as the cyclone never intensified
beyond minimal tropical storm strength. Persistent vertical shear
led to weakening and Erick was downgraded back to depression status
at 1500 UTC on 2 August. Later on the 2nd the remnants of Erick had
degenerated into a tropical wave about 1200 nm west-southwest of the
southern tip of Baja California.
No damage or casualties are known to have resulted from Tropical
Stork Erick.
(Report written by Gary Padgett)
HURRICANE FLOSSIE
(TC-09E)
8 - 16 August
-------------------------------------
A. Synoptic History
-------------------
The Northeast Pacific's only major hurricane of the 2007 season had
its beginnings with an area of disturbed weather first noted about
525 nm south-southeast of Acapulco in early August. While environmental
conditions were basically favorable for development, interaction with
the ITCZ on 3 August hindered the process somewhat. Convective
organization fluctuated for several days, but by 8 August the system
had gained enough structure for advisories to be initiated on Tropical
Depression 09E, located at 08/1800 UTC about 1100 nm west-southwest of
the southern tip of Baja California while moving westward. TD-09E was
upgraded to Tropical Storm Flossie on the second advisory at 09/0000
UTC. Under favorable conditions of low vertical shear and warm SSTs,
the cyclone continued to strengthen and was upgraded to a hurricane at
1200 UTC on 10 August while located approximately 1200 nm east-southeast
of the Hawaiian Islands. After reaching hurricane intensity, Flossie
intensified rather rapidly and within 24 hours had become a 115-kt
Category 4 hurricane shortly before crossing 140W into the CPHC's area
of warning responsibility.
Flossie was a very impressive hurricane with a distinct eye embedded
within a solid eyewall and sporting a very impressive upper-level outflow
pattern as it entered the CPHC region. The hurricane maintained a MSW
of 115-120 kts for the next two days as it moved west-northwestward
toward the Hawaiian Islands. Flossie was a relatively small cyclone
with sustained winds of tropical storm force or greater extending out
only about 85 nm from the center in the northern semicircle during this
period. The storm was being steered toward the west-northwest at around
10 kts by a strong subtropical ridge as it approached the islands. A
Hurricane Watch and Tropical Storm Warning were issued for the Big Island
on the morning of 13 August due to the forecast close approach of the
storm to the island, plus the intensity forecast which maintained Flossie
as a hurricane when it was projected to arrive in the vicinity of the
southern end of the island. However, as Flossie approached the Big
Island a long-anticipated increase in vertical shear began to take its
toll on the storm on the 14th, and the hurricane weakened to a tropical
storm that evening after passing a little more than 85 nm to the south
of the southern tip of the Big Island. Very strong vertical shear led
to Flossie weakening to a tropical depression late on the 15th as it was
passing far to the south of the islands of Oahu and Kauai. The final
CPHC advisory was issued at 16/1500 UTC, placing a weak 25-kt center
about 350 nm southwest of Honolulu.
B. Impacts
----------
Even though the center of Flossie passed about 85 nm due south of
South Point on the Big Island of Hawaii, it generated very large waves
along the southeast-facing shoreline of that island. Surf heights were
estimated to be nearly 6.1 m. Coincident with the passage of Flossie,
a 44-acre lava bench slipped into the ocean during the night of
13 August. It is possible this loss of shoreline was due to the large
surf from Flossie, or a 5.4 magnitude earthquake that occurred around
the same time. Rainfall amounts were not excessive, however, sustained
winds of at least 34 kts were reported at South Point as Flossie passed
by.
No significant damage or injuries were reported in association with
Hurricane Flossie.
The Wikipedia online report on Flossie may be found at the following
link:
http://en.wikipedia.org/wiki/Hurricane_Flossie_%282007%29>
(Report written by Gary Padgett)
TROPICAL STORM GIL
(TC-10E)
29 August - 2 September
-------------------------------------------
Tropical Storm Gil originated from a tropical wave that had entered
the Eastern North Pacific on 23 August. An area of low pressure
developed along the wave axis south of the Gulf of Tehuantepec on the
25th. The LOW moved slowly west-northwestward over the next several
days with convective activity gradually increasing in organization. By
the morning of 29 August the system had become well-organized enough
to warrant classification as Tropical Depression 10E with the initial
advisory being issued at 1200 UTC, locating the center about 220 nm
south of Cabo San Lucas. Despite moderate easterly shear, TD-10E
strengthened and was upgraded to Tropical Storm Gil just six hours
later. Strong high pressure anchored over the southwestern U. S.
steered Gil on a general westerly track for the next several days.
An environment of stable air and easterly shear hampered significant
intensification and Gil reached a peak intensity of 40 kts at 1800 UTC
on 30 August while centered about 330 nm southwest of the southern tip
of the Baja California Peninsula. After peaking on the 30th Gil began
to slowly weaken and was downgraded to a tropical depression at 0000 UTC
on 1 September while located about 575 nm west-southwest of Cabo San
Lucas. Tropical Depression Gil degenerated into a remnant LOW over
cooler waters on 2 September about 800 nm west-southwest of southern
Baja California and the final advisory was issued at 02/1500 UTC.
The Wikipedia report mentions a fatality which occurred on 29 August
near Culiacan in Sinaloa State. A 14-year old boy was swept away by
a flood-swollen river. The heavy rainfall which led to the flooding
could have possibly been associated with the early stages of Gil, but
this location is several hundred miles to the northeast of the location
where TD-10E was organizing at about that time.
(Report written by Gary Padgett)
HURRICANE HENRIETTE
(TC-11E)
30 August - 6 September
-------------------------------------------
A. Synoptic History
-------------------
Hurricane Henriette's origins lay with a tropical wave which moved
off the Central American coastline on 28 August and produced disorganized
showers and thunderstorms for the next day or so. By late on 29 August
a small area of low pressure had developed about 300 nm south-southeast
of Acapulco. Convective activity surrounding the LOW gradually improved
in organization and at 1800 UTC on 30 August the system was designated
as Tropical Depression 11E, located approximately 220 nm southeast of
Acapulco. TD-11E commenced tracking west-northwestward in response to
a weakness in the subtropical ridge over the western Gulf of Mexico.
The system's organization continued to improve as it moved parallel to
the southern Mexican coast, and it was upgraded to Tropical Storm
Henriette at 31/1200 UTC while centered only about 75 nm south of
Acapulco. As August turned into September, Tropical Storm Henriette
was slowly strengthening just off the Mexican coast and bringing
rainfall and tropical storm force winds to portions of the coastline.
Henriette remained just shy of hurricane strength for the next two
days as it moved slowly northwestward away from the coast. The storm
was consistently being forecast to soon reach hurricane intensity, but
probably its close proximity to land and perhaps some upwelling of
cooler waters brought about by the slow movement were inhibiting factors.
Finally, early on 4 September Henriette reached hurricane intensity as
it turned north-northwestward toward the Baja California Peninsula.
The cyclone reached its peak intensity of 75 kts around 04/1800 UTC while
centered about 75 nm south-southeast of Cabo San Lucas. Weakening
slightly, the center of Henriette made landfall that afternoon just east
of Cabo San Lucas with the MSW estimated at 70 kts. Continuing north-
northwestward, the storm emerged over the Gulf of California early on
5 September. The brief interaction with the Peninsula resulted in
slight weakening, but Henriette remained at hurricane intensity until
its final landfall very late on the 5th near Guaymas on the Mexican
mainland. Once inland Henriette weakened quickly over land and had
dissipated over the mountains of northwestern Mexico by the morning
of 6 September.
B. Impacts
----------
Media reports indicate that at least nine persons lost their lives
in Mexico due to Hurricane Henriette. Six of these occurred near
Acapulco due to mud slides induced by heavy rains while the center of
Henriette passed just offshore. Two fishermen were reported killed
off the coast of Sonara. According to the Wikipedia report, damage in
Mexico totaled about $25 million U. S. dollars.
The Wikipedia online report on Henriette may be accessed at the
following link:
http://en.wikipedia.org/wiki/Hurricane_Henriette_%282007%29>
(Report written by Gary Padgett)
*************************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for August: 7 tropical depressions **
2 tropical storms ++
3 typhoons ##
1 super typhoon
** - classified as tropical depressions by JMA only
++ - one of these classified as a tropical storm by JTWC only
## - one of these formed in July and continued operating into August
Sources of Information
----------------------
Most of the information presented below is based upon tropical
cyclone warnings and significant tropical weather outlooks issued
by the Joint Typhoon Warning Center of the U. S. Air Force and
Navy (JTWC), located at Pearl Harbor, Hawaii. In the companion
tropical cyclone tracks file, I normally annotate track coordinates
from some of the various Asian warning centers when their center
positions differ from JTWC's by usually 40-50 nm or more. All
references to sustained winds imply a 1-minute averaging period
unless otherwise noted.
Michael V. Padua of Naga City in the Philippines, owner of the
Typhoon 2000 website, normally sends me cyclone tracks based upon
warnings issued by the Japanese Meteorological Agency (JMA) and the
Philippines' Atmospheric, Geophysical & Astronomical Services
Administration (PAGASA). A very special thanks to Michael for the
assistance he so reliably provides.
In the title line for each storm I have referenced all the cyclone
names/numbers I have available: JTWC's depression number, the
JMA-assigned name (if any), JMA's tropical storm numeric designator,
and PAGASA's name for systems forming in or passing through their
area of warning responsibility.
Northwest Pacific Tropical Activity for August
----------------------------------------------
The month of August was quite active in the Northwest Pacific basin.
Five tropical storms formed with three reaching typhoon intensity. (One
of these was not named by JMA.) In addition, as the month began Typhoon
Usagi was prowling Western Pacific waters en route to a landfall in
Japan. The report on Usagi may be found in the July summary; however,
a couple of corrections to that report are given below.
Tropical Storm 06W was a fairly weak South China Sea tropical storm
which nonetheless was responsible for 60 or more deaths in Vietnam due
to flooding. JMA did not classify this system as a tropical storm, and
JTWC had it as a minimal tropical storm for only 12 hours, but QuikScat
data suggests that the cyclone may have been a little stronger than
reported by the warning agencies. Typhoon Pabuk sailed westward,
clipping the southern tip of Taiwan and brushing the southern Chinese
coastline early in the month, while at around the same time Tropical
Storm Wutip formed east of the Philippines and moved toward Taiwan.
The second week of August gave rise to mighty Super Typhoon Sepat which
ultimately made destructive strikes in Taiwan and in mainland China.
Late in the month, a reverse-oriented monsoon trough gave rise to Typhoon
Fitow, which continued operating into the second week of September and
made a significant strike on Honshu. Reports on all four named storms
plus the unnamed tropical storm follow.
In addition to the tropical storms and typhoons, no less than seven
systems were referenced as tropical depressions by JMA in their High Seas
bulletins. Brief synopses of these systems follow:
(1) TD of 10-12 August - The JMA High Seas Bulletin at 09/0600 UTC
referenced a weak tropical depression (1002 hPa) near 22N/126E,
moving west slowly, but the bulletins for the next two cycles
did not reference a tropical depression, nor even a low-pressure
area, in this vicinity. At 10/0000 UTC, a weak tropical depression
was placed near 25N/123E, moving slowly north. JTWC mentioned the
system in an interim STWO issued at 10/0100 UTC, locating an area
of convection about 65 nm southwest of Naha, Okinawa. QuikScat
data revealed a tight area of turning within the monsoon trough.
The depression commenced moving northward at an accelerating pace.
JTWC issued a TCFA at 10/2130 UTC for a LLCC located about 265 nm
west-northwest of Naha. Convection was concentrated in an area
of low-level convergence to the east of the tightest turning.
The small LLCC was located within a broader gyre-type circulation
with the strongest winds on the periphery of the larger circulation.
Early on the 11th the LLCC became more disorganized, and by 11/1300
UTC the LLCC, then located about 310 nm west of Sasebo, Japan, had
become fully-exposed west of a band of patchy convection. The system
was encountering a mid-latitude trough moving out of northeastern
China which was inducing increasing vertical shear and causing the
depression to accelerate northward. JTWC cancelled the TCFA at
11/1130 UTC, and JMA classified the system as extratropical at
12/0600 UTC in the Yellow Sea just west of Korea with the LOW
subsequently continuing northward, moving into northeastern China.
JMA estimated the peak MSW for this system at 30 kts. A track for
this tropical depression is included in the companion cyclone tracks
file.
(2) Weak TD of 11-12 August - The beginnings of this system can be traced
to an area of convection which persisted on 9 August approximately
740 nm east-northeast of Guam. Satellite imagery depicted a
developing LLCC with convection flaring on the periphery. The
disturbance over the next couple of days migrated west-northwestward
and by the 11th was located about 125 nm east of Iwo Jima. A fully-
closed LLCC had developed but convection was still not persisting
near the center; hence, JTWC's development potential remained 'poor'.
JMA first referenced the system as a weak tropical depression at
11/0000 UTC near 24N/143E. The system drifted slowly west-
northwestward on the 11th, but moved quickly (based on JMA's
bulletins) late on the 11th to near 27N/138E where it became quasi-
stationary. At 12/1200 UTC the depression was downgraded to a
low-pressure area.
(3) TD of 14-15 August - JMA tracked this system from near 26.2N/123.6E
(northeast of Taiwan) at 14/0000 UTC northward to near 38N/125E (in
the Yellow Sea just west of Korea) by 15/1200 UTC. No reference was
made to this disturbance in JTWC's STWOs, and given the latitude of
formation, it is highly likely that it was a non-tropical or hybrid
system. JMA estimated peak winds of 30 kts for this system. A track
for this tropical depression is included in the companion tropical
cyclone tracks file.
(4) Weak TD of 14-18 August - This system, treated as a weak tropical
depression by JMA, was first referenced at 14/1800 UTC when it was
located at 23N/115E, or on the south Chinese coast very near Hong
Kong. Based on JMA's positions, the system meandered very slowly
for several days over the northern South China Sea between Hong
Kong and Hainan Dao, being last mentioned at 18/0600 UTC near
21N/114E.
NOTE: I do not have available any STWOs issued by JTWC during this
period. Normally, I receive the outlooks via e-mail and store any
which contain a reference to any areas of disturbed weather. But
occasionally, due to some glitch in the system, the STWOs do not
arrive via e-mail, and I often forget to visit JTWC's website and
download them. However, I suspect that in this case, since the
system was so near the coast it was not considered a suspect area
for development by JTWC.
(5) TD of 21-25 August - This system was first referenced by JMA at
21/0000 UTC near 22N/136E, or well west of the northern Marianas.
The depression drifted slowly west-northwestward to near 25N/134E
at 22/0600 UTC. It then drifted very slowly west-southwestward for
the next two days to near 23N/127E by 24/0600 UTC. The next bulletin
at 24/1200 UTC relocated the center to 20N/128E (or else picked up
on a new LLCC). The final reference by JMA to this depression down-
graded it to a low-pressure area near 22N/127E at 25/0000 UTC.
JTWC first mentioned this system in an interim SWTO issued at 0000
UTC on 21 August. Convection was flaring over the northeastern
quadrant of a developing LLCC. The environment was fairly favorable
for strengthening, so the development potential was assessed as
'fair'. A TCFA was issued at 22/0230 UTC as the system continued
to exhibit improved convective organization. However, as the 22nd
wore on, a mid-latitude trough deepened over the Sea of Japan,
increasing the vertical shear over the disturbance. By 2100 UTC the
LLCC, located about 220 nm east-southeast of Naha, had become fully-
exposed. JTWC cancelled the TCFA and downgraded the potential for
development to 'poor'. Also, a TUTT cell over Okinawa was
contributing to convergence over the system, helping to suppress
convection.
JMA estimated the peak MSW for this depression at 30 kts. A track
for this system is included in the companion tropical cyclone tracks
file.
(6) Weak TD of 24 August - This weak system was mentioned only once in
JMA's bulletins, at 24/0600 UTC, when it was located near 21N/131E.
JTWC's STWO issued at the same hour mentioned the disturbance, which
was located about 385 nm south-southeast of Okinawa. A LLCC appeared
to be developing with an increase in convection near the center.
However, by 25/0600 UTC the convection had dissipated and the system
was dropped from the STWOs.
(7) Weak TD of 31 August-01 September - JMA's final tropical depression
for August was a weak, short-lived system that was likely a hybrid
LOW. The first reference was at 31/1800 UTC near 33N/172E, or
several hundred miles west-northwest of Midway. The depression was
moving west-northwestward at 15 kts, and at 0000 UTC on 1 September
had moved to near 34N/171W. However, this was the final reference
to the system in JMA's bulletins. This system was not mentioned
in any of JTWC's STWOs and was likely not tropical in character.
MINOR CORRECTIONS TO TYPHOON USAGI REPORT
-----------------------------------------
In the report for Typhoon Usagi in the July summary, in Section B
(Observations), a couple of corrections need to be made based upon
revised information received from Derrick Herndon. A wind observation
from Nyutubaru AFB of 030@35G72 kts was listed for 0500 UTC. The time
actually was 0449 UTC. And the elevation for the Seto station is
134 meters instead of 143 meters as originally given.
TROPICAL STORM
(TC-06W)
2 - 7 August
----------------------------------
A. Synoptic History
-------------------
At 0400 UTC 2 August JTWC issued a TCFA on a disturbance located
approximately 185 nm east of Nha Tang, Vietnam. Multi-spectral imagery
indicated a consolidating system with deep convection developing over a
well-defined but partially-exposed LLCC. Upper-level analysis revealed
a weak to moderate wind shear environment with a broad upper-level trough
above the disturbance. The first warning on Tropical Depression 06W was
issued at 02/1800 UTC, locating the centre about 140 nm southeast of Hue,
Vietnam.
Embedded in a slack steering flow, Tropical Depression 06W drifted
slowly and erratically on 3 August while continuing to exhibit an exposed
LLCC. It was upgraded to a 35-kt tropical storm at 0000 UTC 4 August
when a strong convective burst occurred southwest of the centre.
However, the system soon became virtually devoid of convection and was
downgraded back to tropical depression status at 04/1200 UTC. The
easterly shear kept up, preventing the system from regaining tropical
storm intensity. Tracking westwards, TD-06W reached the coast of
Vietnam, then abruptly turned north on 5 August. The dying storm then
headed northwestward early on 6 August and into the Gulf of Tonkin before
dissipating over Vietnam the next day. JTWC issued the final warning at
07/0600 UTC. JMA classified this system as a 30-kt tropical depression
beginning at 02/0600 UTC, but never upgraded to tropical storm intensity;
hence, the system was not named. (TD-06W formed and remained west of
PAGASA's AOR, so no name was assigned by that agency.) JMA carried the
system as a tropical depression inland into Vietnam, last referencing the
LOW at 07/1800 UTC.
B. Meteorological Observations
------------------------------
The author received some information from Derrick Herndon at CIMSS
concerning ship and QuikScat observations made in association with
Tropical Storm 06W. Following are Derrick's comments, slightly edited:
"I found a ship observation from ship DCCN2 at 11.2N/110.5E at 03/0600
UTC which reported winds of 270/52 kts and a pressure of 1002 mb. I
initially questioned this wind; however, QuikScat indicated winds of
40-50 kts on the southwest side of the circulation. An upgraded version
of the QuikScat algorithm was received from Paul Chang which showed that
many of these wind vectors were not rain-flagged. I do not know the
height of the anemometer for this ship, but it would appear that the
observation may have been valid, suggesting winds around 45 kts. AMSU
intensity estimates from both our algorithms and CIRA's algorithm, along
with the AODT, all indicated a MSLP of 995-998 mb, in agreement with the
surrounding ship observations. Pressures in southern Vietnam at this
time were 1008-1009 mb, and if the MSLP was indeed 996 mb, then a decent
gradient would have existed just off the Vietnamese coast. The lowest
pressure I could find at landfall was from station 59981 which reported
999 mb on the 3rd."
And later information from Derrick:
"Several ships reported observations near TS-06W. Ship MGRH9 reported
1007.6 mb with winds 270/37 kts 70 nm SW of the center at 02/1200 UTC.
The ship was located in the active convective region and QuikScat data
supports the winds. Ship DCCN2 reported a pressure of 1002 mb with winds
270/52 kts at 03/0600 UTC 150 nm SW of the center. (This observation
described in above paragraph.) This report now appears to have been
outside the strongest winds and thus the wind is suspect (perhaps
26 kts). Again, QuikScat supported winds of 40-45 kts on the 3rd. The
surrounding observations suggest that the lowest MSLP was about 995 mb
around 1200-1800 UTC on the 3rd. There were no significant observations
from the landfall in Vietnam, which occurred after the system had
significantly weakened."
A very special thanks to Derrick for the observations and analysis.
From this information, it appears that Tropical Storm 06W was stronger
and at tropical storm intensity for a longer period than reported in
JTWC's warnings.
C. Damage and Casualties
------------------------
News sources indicate that 60-70 people died in Vietnam as a
result of the extensive flooding caused by Tropical Storm 06W. The
Wikipedia report states that some portions of Vietnam received over
24 inches (610 mm) of rainfall for a storm total in association with
TC-06W, and that Hainan Dao received a total of 231.6 mm.
(Section A written by Kevin Boyle; Sections B and C added by Gary Padgett
with much information supplied by Derrick Herndon)
TYPHOON PABUK
(TC-07W / TY 0706 / CHEDENG)
4 - 14 August
------------------------------------------------
Pabuk: contributed by Laos, is the name of a large freshwater fish
that lives in the Mekong River
A. Synoptic History
-------------------
The origins of Typhoon Pabuk can be traced back to a disturbance
located approximately 440 nm northwest of Guam. It was first alluded
to in JTWC's STWO at 0800 UTC 4 August when multi-spectral satellite
imagery revealed flaring convection near a developing LLCC. Upper-
level analysis indicated low vertical shear and moderate divergence
aloft. The system drifted west-northwestwards and quickly organized.
A TCFA was issued at 05/0300 UTC after an extensive CDO had formed over
the centre. The disturbance was upgraded to a 35-kt tropical storm on
the first warning issued by JTWC at 05/0600 UTC. At the same time JMA
raised their 10-min avg MSW to 35 kts and assigned the name Pabuk.
(JMA had first identified Pabuk as a tropical depression at 04/1800
UTC). Pabuk was known locally in the Philippines by the name Chedeng.
Pabuk moved smartly across the Northwest Pacific on a predominantly
westerly trajectory, a straight-runner, and remained south of the
subtropical ridge axis. For most of its life, the tropical cyclone was
located on the northern side of a monsoon depression which was to later
spawn Tropical Storm Wutip. Tropical Storm Pabuk gradually
strengthened on 5-6 August, and was upgraded to a minimal typhoon at
0000 UTC 7 August, located approximately 285 nm southeast of Taipei,
Taiwan. This was to be its maximum intensity. The storm was briefly
downgraded to a 60-kt tropical storm at 07/1200 UTC, but was upgraded
back to typhoon intensity at 07/1800 UTC based on the appearance of a
small eye as depicted in Taiwan radar imagery.
After passing over the southern tip of Taiwan, Pabuk was downgraded
back down to a tropical storm at 08/0000 UTC. Once across the Taiwan
Strait, Pabuk flirted with the southern Chinese coast and passed just
south of Hong Kong late on 8 August. The system began to track more
slowly southwestwards, and was lowered to tropical depression status at
09/0600 UTC on what was initially JTWC�s final warning. It was felt
that Pabuk was dissipating over land at this time. When infrared
imagery revealed that the centre had not moved inland, but in fact had
remained offshore and moved parallel to the Chinese coast, JTWC re-
issued a penultimate warning at 09/1200 UTC and relocated Pabuk further
to the south to a position 140 nm southwest of Hong Kong. The final
warning was issued at 09/1800 UTC.
The remnants of Pabuk drifted erratically over the next two days.
The system drifted slowly northwestward, passing very near Hong Kong
before meandering inland near Zhongshan, Guangdong Province, on 10
August. Abruptly turning northeastward, the 30-kt LOW crossed the
Pearl River Estuary, passing north of Hong Kong on 11 August. The
system accelerated east-northeastward over China before turning to the
northeast on 12 August, emerging into the East China Sea later that
same day. Pabuk�s remnants entered the Yellow Sea early on 14 August
and were last noted in JMA�s high seas bulletin at 0600 UTC on 14
August heading in a more northerly direction towards North Korea.
B. Observations
---------------
Following are some observations sent to the author by Derrick Herndon.
Again, a very special thanks to Derrick for sending the information.
"On the 7th Pabuk passed just south of Lan-yu located just east of the
southern tip of Taiwan. The station recorded a pressure of 979 mb at
1300 UTC while apparently in the northern eyewall, according to both
radar and microwave imagery. At 1600 UTC the station reported winds of
Force 8, gusting to Force 17, which equates to 37 kts gusting to 113 kts.
The station on the island is highly elevated at 325 meters. After
passing Lan-yu, the eye became quite small as the system intensified.
The very small eye (perhaps 7.5 nm) passed over southern Taiwan just
north of Henchun. Henchun reported 979 mb at 1700 UTC with west winds
of 41 kts (10-min avg) gusting to 57 kts. It appears that Henchun was
in the southern eyewall based on radar; however, the winds seem weak
even accounting for the station being on the weak side of the circu-
lation. The storm was moving at 15-20 kts, so that may account for some
of that discrepancy. The observation from Henchun suggests a MSLP of
964-970 mb. Taitung was located 44 nm north of the center and reported
999 mb at 1700 UTC. Using the 965 mb MSLP results in a gradient of
34 mb over 44 nm, from which I calculated a gradient wind of about
92 kts. The environmental pressure was about 1002 mb, so that 92-kt
MSW matches well with what would be expected for 965 mb. Since the
storm was moving at 15-20 kts and the RMW was quite small, I would
expect a slight upward deviation from the 92 kts to perhaps 100 kts.
This is a best guess based on the available data.
"After passing Taiwan Pabuk weakened significantly on the 8th. Ship
MLXD5, located 60 nm southeast of the center, reported 993.5 mb and
winds 260/37 kts at 08/1200 UTC. Buoy 22516 reported a MSLP of 998.1 mb
120 nm northeast of the center at 08/0300 UTC, and had earlier reported
a MSLP of 1000 mb while located about 60 nm south of the center at
06/1200 UTC."
C. Links and Comments
---------------------
A report on Typhoon Pabuk written by the Hong Kong Observatory can be
found at:
http://www.hko.gov.hk/informtc/pabuk/pabuk.htm>
D. Damage and Casualties
------------------------
Pabuk brought much needed rain to southern parts of China, alleviating
the long drought that the region had been suffering from for many months.
However, flooding destroyed around 3,000 homes in Guangdong Province.
The storm also affected the cities of Zhanjiang, Maorning and Meizhou,
causing $170 million in economic losses and destroying more than 3,500
homes. One person was killed in Hong Kong.
Taiwan reported no casualties as a result of Typhoon Pabuk. The
storm disrupted power supplies to 3,000 households, otherwise, damage
was minimal.
Monsoonal rains enhanced by Pabuk caused flooding in the Philippines,
triggering landslides which killed 11 person.
(Sections A, C and D written by Kevin Boyle; Section B added by Gary
Padgett based on information supplied by Derrick Herndon)
TROPICAL STORM WUTIP
(TC-08W / TS 0707 / DODONG)
6 - 9 August
-----------------------------------------------
Wutip: contributed by Macau, is the Macanese word for butterfly
A. Synoptic History
-------------------
The tropical disturbance that spawned Wutip developed on the southern
flank of a monsoon depression which also included Typhoon Pabuk on its
northern periphery. It was first mentioned in JTWC's STWO at 2230 UTC
6 August when infrared satellite imagery indicated persistent deep
convection near a developing LLCC approximately 450 nm east of Manila,
Philippines. Upper-level analysis indicated a moderate wind shear
environment due to outflow from Typhoon Pabuk, but favourable diffluence
aloft, aided by strong low-level cyclonic shear, allowed the system
to organize. A TCFA was issued at 07/1000 UTC, and two hours later,
the first warning on Tropical Depression 08W was released with the
system drifting west-northwestward at 15 kts. The centre was located
approximately 330 nm east-northeast of Manila, or near 17.2N/126.1E.
JMA had first classified the system as a tropical depression near
14N/128E at 1800 UTC 6 August.
Drifting northwestward, Tropical Depression 08W was named Wutip at
0000 UTC 8 August when JMA raised their 10-min avg MSW to 35 kts. At
the same time, the cyclone was also dubbed Dodeng by PAGASA when the
storm had crossed into their AOR. JTWC upgraded Wutip to a 35-kt
tropical storm at 08/0600 UTC. Under the influence of subtropical
ridging that lay across the Northwest Pacific, Tropical Storm Wutip
tracked smartly northwestwards, reaching a peak intensity of 40 kts at
08/1800 UTC. Thereafter, strong upper-level shear, convergence aloft,
and interaction with Taiwan led to the system's rapid demise. The LLCC
was barely discernible when it reached the eastern coast of Taiwan early
on 9 August. (The JTWC position at 09/0600 UTC puts the center of Wutip
right over central Taiwan. However, the concurrent JMA position places
the center in the Pacific well off the east coast of the island.) On
9 August Wutip's very weak LLCC crossed Taiwan and was downgraded to a
tropical depression at 09/0600 UTC. The final warning was issued at
09/1800 UTC, locating the centre in the Taiwan Strait about 135 nm
west-southwest of Taipei.
B. Meteorological Observations
------------------------------
A ship (ID unknown) reported a MSLP of 1001.9 mb and winds 140/28 kts
at 07/0900 UTC, then 1004.4 mb and 110/33 kts at 07/1200 UTC while
passing southeast and east, respectively, of the developing center.
Stations ROIG and ROYN, located 120-150 nm northeast of the center,
reported winds sustained at 29-33 kts at 1200 UTC on 8 August. At
08/1700 UTC Taitung, Taiwan, reported a MSLP of 993 mb, and Pengjiayu
recorded sustained winds of 37 kts. (The above information sent by
Derrick Herndon.)
C. Damage and Casualties
------------------------
Tropical Storm Wutip brought torrential rainfall to the northern
Philippines which, added to the rains from Typhoon Pabuk, ended the
three-month drought there. This led to flash flooding and mudslides
which claimed three lives and injured 17 others. Over 10,000 people
were left homeless.
(Sections A and C written by Kevin Boyle; Section B added by Gary
Padgett based on information received from Derrick Herndon)
SUPER TYPHOON SEPAT
(TC-09W / TY 0708 / EGAY)
11 - 22 August
--------------------------------------------
Sepat: contributed by Malaysia, is the name of a freshwater fish
often found in rivers and swampy areas with lots of weeds,
and also in paddy fields
A. Synoptic History
-------------------
Super Typhoon Sepat originated as a disturbance in the monsoon
trough and was first mentioned in JTWC�s STWO at 0600 UTC 11 August
when deep convection persisted northwest of a developing LLCC, located
approximately 695 nm southeast of Naha, Okinawa. (At the same time,
JMA identified the system as a tropical depression in their High Seas
Forecast.) Upper-level analysis revealed favourable divergence aloft
but moderate wind shear over the system. Further developments led to
the issuance of a TCFA at 11/2000 UTC, and the first warning was issued
at 12/0600 UTC, placing the centre of Tropical Depression 09W about 685
southeast of Okinawa and quasi-stationary. The slow-moving tropical
cyclone intensified, and was upgraded to a 40-kt tropical storm at
12/1200 UTC despite the hindering effects of the northerly shear and a
temporary loss of some of its deep convection. JMA upgraded the system
to tropical storm status at 12/1800 UTC, raising their 10-min avg MSW
to 35 kts and assigning the name Sepat. (Locally, in the Philippines,
the storm was known as Egay.)
Tropical Storm Sepat steadily intensified on 13 August while
tracking in a more westerly direction along the southern perimeter of
the subtropical ridge, and was upgraded to an 80-kt typhoon at 0000 UTC
14 August approximately 620 nm south-southeast of Naha, Okinawa. (JMA
also upgraded Sepat to typhoon status at the same time.) After
acquiring a 12-nm diameter eye late on 14 August, Sepat strengthened more
rapidly and was upped to super typhoon status at 15/0000 UTC before
reaching its maximum intensity of 140 kts eighteen hours later. At
this time Super Typhoon Sepat was located about 530 nm southeast of
Kaoshiung, Taiwan. Typhoon-force winds extended outward 55 nm from the
centre in all quadrants, and gales extended outward from 130-140 nm.
JMA estimated the minimum CP at 910 mb.
Moving on a north to north-northwesterly track, Sepat remained a
super typhoon for 30 hours, undergoing an eyewall replacement cycle
late on 16 August. Weakening began on 17 August as the storm continued
northwestward. Typhoon Sepat made landfall over Taiwan with a MSW of
105 kts at around 17/2100 UTC, then proceeded from there into
southeastern mainland China, making landfall roughly 550 km northeast
of Hong Kong 24 hours later. Sepat continued to weaken as it tracked
further inland. The former super typhoon was downgraded to a tropical
storm on JTWC�s final warning at 19/0000 UTC. JMA downgraded Sepat to
a tropical depression at 20/0000 UTC, but continued to follow the
remnants as a depression through 22/1200 UTC when the weak LOW center
was located well-inland near 28N/112E.
B. Meteorological Observations
------------------------------
The following was received from Derrick Herndon:
"As Sepat passed NE of Lyudao, the station reported 10-min avg winds
of 47 kts, gusting to 70 kts, at 2000 UTC on the 17th. There was a
secondary peak in the wind 3 hours prior, possibly indicating a residual
double-eye structure. Chengong, Taiwan, experienced a direct hit by
Sepat. The station reported a pressure of 952 mb with winds 320/46 kts
(10-min avg) at 2100 UTC on the 17th. The winds then dropped off to
25 kts at 2200 UTC, then rose to sustained 57 kts at 2300 UTC as the
second eyewall passed. The system was weakening rapidly, thus the lowest
pressure reported by the station was when the center made landfall to the
north. While Sepat exhibited concentric eyewalls as it approached the
island, Taiwan radar indicated a single large eyewall at the time of
landfall. It appears the station was in the southern eyewall at this
time, so an estimate of the MSLP can be made. I would put the MSLP at
landfall around 933 mb.
"The buoy offshore Chengong also reported a maximum wave height of
6.9 meters and a storm surge of 3.5 meters. After crossing Taiwan, the
lowest pressure observed was from Penghu, which was 985 mb at 1200 UTC
on the 18th, supporting a central pressure at this time of 978 mb."
C. Links and Comments
---------------------
A detailed Wikipedia report available for Super Typhoon Sepat may be
accessed at the following URL:
http://en.wikipedia.org/wiki/Typhoon_Sepat_%282007%29>
The following three microwave and AMSU images depict the eyewall
replacement cycle (ERC) which Sepat underwent on 16 August:
http://www.nrlmry.navy.mil/TC/tc07/WPAC/09W.SEPAT/ssmi/85h/1degreeticks/20070816.0937.f13.x.85h_1deg.09WSEPAT.140kts-918mb-179N-1261E.67pc.jpg>
http://www.nrlmry.navy.mil/TC/tc07/WPAC/09W.SEPAT/tc_ssmis/91h/1degreeticks/20070816.1151.f16.x.91h_1deg.09WSEPAT.140kts-918mb-179N-1261E.63pc.jpg>
http://www.nrlmry.navy.mil/TC/tc07/WPAC/09W.SEPAT/amsub/color/2degreeticks/20070816.1235.metopa.x.color_89_150.09WSEPAT.135kts-922mb-187N-1256E.82pc.jpg>
The link below is a wonderful animation which vividly reveals the
details of the ERC. The typhoon remains stationary at the center of the
image while the islands of Luzon and Taiwan slowly migrate toward the
south-southeast. Watch how the small, intense eyewall slowly begins to
erode as a spiral band begins to grow and transform into the new eyewall.
http://cimss.ssec.wisc.edu/tropic/real-time/marti/2007_09W/webManager/displayGifsBy12hr_08.html>
D. Damage and Casualties
------------------------
According to the online Wikipedia report, Typhoon Sepat brought high
winds and torrential rain to Taiwan, resulting in numerous mudslides.
The storm caused an estimated US$34.5 million damage to agriculture,
and left 70,000 homes without electricity. The Suao-Hualien Highway
was closed due to landslides, and one person was reported dead.
According to Wikipedia�s report, Sepat's winds felled billboards and
ripped roofs off houses in Fujian Province, killing two people. Also,
Sepat caused landslides in Fujian, leaving 12 people missing. In
Zhejiang a tornado killed 13 people and injured 60 others. Damage was
also reported in Jiangxi and Hunan, and damage in the four provinces
was estimated at 5 billion yuan (US$658 million). The overall death
toll was 39.
Floods caused by heavy monsoonal rains associated with Sepat caused
chaos in Metro Manila with at least three people reported dead.
(Sections A, C and D written by Kevin Boyle; Section B added by Gary
Padgett based on information received from Derrick Herndon)
TYPHOON FITOW
(TC-10W / TY 0709)
26 August � 9 September
-------------------------------------------
Fitow: contributed by the Federated States of Micronesia, is the
Yapese name for a beautiful fragrant flower
A. Synoptic History
-------------------
Typhoon Fitow stemmed from a disturbance located at the eastern end of
a reverse-oriented monsoon trough. JMA identified a weak tropical
depression at 26/0600 UTC several hundred miles east of the Marianas,
near 15N/151E. The system was referenced in JTWC's TCFA at 1630 UTC
28 August, located approximately 560 nm east-northeast of Saipan.
Remarks on this statement included: "Animated enhanced infrared satellite
imagery indicates deep convection banding into a LLCC with additional
convection forming near the center. The previous two Quikscat passes
have also depicted this LLCC with 15-20 kts of unflagged winds. Upper-
level analysis indicates weak vertical shear aloft. Poleward outflow
is being enhanced by TUTT cells to the north and northwest of the LLCC.
In addition to good poleward outflow, a ridge south of the LLCC is
enhancing equatorward outflow." The first warning on Tropical
Depression 10W was issued at 28/1800 UTC, the system moving
northeastward at 13 kts. JTWC upgraded TD-10W to a 35-kt tropical
storm at 29/0000 UTC with the centre located 675 nm northeast of
Saipan, moving northeastward at 14 kts. Six hours later, JMA raised
their 10-min avg MSW to 35 kts and named the system Fitow.
After its upgrade, the storm moved northeastward on 29 August before
turning northwards by early 30 August. Intensifying, the system was
upgraded to a 65-kt typhoon at 1800 UTC 29 August while located
approximately 860 nm east of Iwo Jima. At 31/0000 UTC Fitow slowed and
backed sharply onto a west-northwesterly heading, attaining an
intensity of 80 kts. The tropical cyclone weakened as it continued
slowly west-northwestwards due to the entrainment of drier air and the
MSW fell back to 70 kts on 31 August. Typhoon Fitow maintained 70-75 kt
winds for the next two days while meandering slowly westwards. After
breaking away from the monsoon cloud band on 1 September, the cyclone
began to re-intensify on 2 September and reached a peak intensity of
85 kts at 03/0600 UTC. A weakening trend began late on 3 September but
leveled out at 70 kts as Fitow passed close to Chichijima early on
4 September.
Typhoon Fitow gradually re-strengthened as it drifted west-
northwestwards on 4 September and onto a northwesterly heading the next
day. On 6 September the storm began to accelerate northwards under the
influence of a mid-level trough over Korea, and reached its peak
intensity of 85 kts for the second time at 0600 UTC 6 September while
located approximately 175 nm south-southwest of Tokyo, Japan.
Recurving north-northeastwards, Fitow made landfall over Japan as a
minimal typhoon late on 6 September. It was downgraded to a tropical
storm by both JTWC and JMA at 07/0000 UTC as it continued to race
north-northeastward over northern Honshu. JTWC issued their last
warning at 07/0600 UTC. Fitow crossed over the northernmost Japanese
island of Hokkaido later on the 7th and subsequently moved into the
North Pacific. JMA declared Fitow extratropical and issued their final
tropical cyclone warning at 08/0600 UTC. The extratropical remnants
of Fitow continued to diminish and had weakened into a 25-kt LOW near
46N/148E by 09/0000 UTC.
B. Meteorological Observations
------------------------------
Following are some observations and analysis from Derrick Herndon of
CIMSS (as always, a special thanks to Derrick for the information):
(Note: All winds are 10-minute average winds unless specified otherwise.)
Fitow passed about 50 miles north of Chichijima (RJAO) around 0800 UTC
on the 4th. This station only reports 3-hourly observations. At 0600
UTC the station reported 976 mb with winds 220@34G64 kts. At 0900 UTC
the pressure had only risen to 979 mb and winds decreased some to
250@33G58 kts. By 1200 UTC the pressure continued to rise to 985 mb and
winds also increased, apparently due to a stronger rainband with winds
220@44G66 kts. The station is located at 8 meters elevation. A
September 3rd 1549 UTC 37 GHz Aqua image strongly suggested a double
eyewall structure; however, this feature appeared to weaken with time
over the next 12-18 hours, leaving a larger eye and associated larger
radius of maximum winds while passing Chichijima. The station was on
the southern edge of the eyewall. Based on the station's pressure and
winds, the MSLP around 0600 UTC on the 3rd was likely below 968 mb and
probably close to 962 mb.
The center of Fitow made landfall in Honshu on the 6th near Irozaki
(47666). The station recorded sustained winds of 63 knots at 0900 UTC
with winds remaining at 56-58 knots sustained until 1200 UTC while the
station was within the northern eyewall of the large eye. Irozaki is
located at the southern tip of the Izu Peninsula, and the station is at
an elevation of 56 meters. A minimum pressure of 966.9 mb was recorded
at 1300 UTC with winds 080@27 kts, putting the MSLP at landfall around
964 mb. A 10-minute avg wind of 63 knots corresponds to a 1-minute avg
wind of about 69 knots. Stronger winds may have occurred to the east of
the center, thus I estimate the MSW at the time of landfall around
75 knots based on the observations.
Other observations from Fitow are listed below:
Hachijo-Jima (RJTH 95 meters): 0800 UTC - winds 18046G68 kts with a
pressure of 980 mb
Kozushima Airport (138 meters): 1100 UTC - winds 120@58 kts
Yokosuka (RJTX 53 meters): 1644 UTC - winds 160@54G73 kts with
a peak wind of 74 kts
One interesting aspect of this storm was the large spread in the
current intensity estimates with the AMSU-based estimates on the high
side and the ADT rather weak owing to the poor IR presentation and lack
of an eye in the IR. See the following link:
http://cimss.ssec.wisc.edu/tropic/satcon/10W.html>
C. Links and Comments
---------------------
Typhoon Fitow followed an unusual S-shaped track typically associated
with a reverse monsoon trough. A paper describing unusual tropical
cyclone tracks, in particular the S-shaped track, written by Dr. Mark
Lander, can be found at this link:
http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F1520-0434(1996)011%3C0170:STCTTA%3E2.0.CO%3B2>
There is not a special, detailed Wikipedia report available for
Typhoon Fitow. However, the regular report (with additional links) may
be accessed at the following URL:
http://en.wikipedia.org/wiki/Typhoon_Fitow_%282007%29>
D. Damage and Casualties
------------------------
According to the Wikipedia report, in Japan seven people were
killed, and at least 50 were injured as Fitow brought strong winds and
heavy rains. Over 80,000 houses experienced a power outage. Transport
in and around Tokyo was also affected, with nearly 200 flights cancelled
and many commuter trains suspended. In the Tama area west of central
Tokyo, flood warnings were issued for the Tama River, and many homeless
people who lived along its banks were swept away.
(Report written by Kevin Boyle with considerable information supplied by
Derrick Herndon)
*************************************************************************
NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea
Activity for August: 1 deep depression **
** - no warnings issued on this system by JTWC
North Indian Ocean Tropical Activity for August
-----------------------------------------------
An area of convection developed and persisted on 4 August about
175 nm south of Calcutta, India. Satellite imagery indicated a broad,
partially-exposed LLCC lying within the monsoon trough over the northern
Bay of Bengal. With stronger winds along the southern periphery in
monsoonal flow and lighter winds near the core, the LOW was exhibiting
characteristics of a monsoon depression. At 0000 UTC 5 August, the IMD
classified the system as a depression. A SSMI microwave pass at 05/0130
UTC indicated convective banding wrapping south of the center from the
northwest with moderate vertical shear over the system. JTWC upped the
potential for development to 'fair' at 05/0600 UTC. A series of ASCAT
passes on the 5th indicated winds of 20-25 kts on the northern edge of
the LLCC with 30-kt winds on the southern periphery. IMD upgraded the
system to 'deep depression' status at 05/1800 UTC, implying 30-kt winds.
However, the depression moved westward and crossed the coast of India
during the morning of the 6th and subsequently began to weaken. A track
for this depression is included in the companion cyclone tracks file.
*************************************************************************
SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E
Activity for August: No tropical cyclones
*************************************************************************
NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E
Activity for August: No tropical cyclones
*************************************************************************
NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E
Activity for August: No tropical cyclones
*************************************************************************
SOUTH PACIFIC (SPA) - South Pacific Ocean East of Longitude 160E
Activity for August: No tropical cyclones
*************************************************************************
SPECIAL FEATURE - SOURCES OF TROPICAL CYCLONE INFORMATION
The purpose of this section is to list some websites where many and
varied types of tropical cyclone information are archived. Many readers
will know about these already, but for the benefit of those who don't,
I wanted to include them.
(1) Aircraft Reconnaissance Information
---------------------------------------
Various types of messages from reconnaissance aircraft may be
retrieved from the following FTP site:
ftp://ftp.nhc.noaa.gov/pub/products/nhc/recon/>
Information regarding how to interpret the coded reconnaissance
messages may be found at the following URL:
http://www.nhc.noaa.gov/reconlist.shtml>
Links are also included to websites with further information about the
U. S. Air Force 53rd Weather Reconnaissance Squadron and the NOAA Air-
craft Operations Center.
(2) Archived Advisories
-----------------------
All the advisory products (public advisories, forecast/advisories,
strike probabilities, discussions, various graphics) issued by TPC/NHC
are archived on TPC's website. For the current year (using 2004 as an
example), the archived products can be found at:
http://www.nhc.noaa.gov/archive/2004/index.shtml>
Links to tropical products archives for earlier years are available at
the following URL:
http://www.nhc.noaa.gov/pastall.shtml>
JTWC warnings for past storms are archived on the NRL Monterrey website:
http://www.nrlmry.navy.mil/tc_pages/tc_home.html>
On the NRL site, the link to past years can be found in the upper left
corner of the screen.
I am not aware at the moment of any other TCWC which archives all
its tropical cyclone warning/advisory products for public access, but
if I learn of any, I will add them to this list.
(3) Satellite Imagery
---------------------
Satellite images of tropical cyclones in various sensor bands are
available on the NRL Monterrey and University of Wisconsin websites,
courtesy of Jeff Hawkins and Chris Velden and their associates. The
links are:
http://www.nrlmry.navy.mil/tc_pages/tc_home.html>
http://cimss.ssec.wisc.edu/tropic/tropic.html>
On the NRL site, the link to past years can be found in the upper left
corner of the screen. For the CIMSS site, a link to data archives is
located in the lower left portion of the screen.
Additional tropical satellite imagery, along with looping ability for
composite microwave imagery for the Western Hemisphere north of the
equator, can be found at:
(1) For the Eastern North Pacific:
http://www.ssd.noaa.gov/PS/TROP/trop-epac.html>
(2) For the Atlantic, Gulf of Mexico and Caribbean Sea:
http://www.ssd.noaa.gov/PS/TROP/trop-atl.html>
(4) Cyclone Tracking Information
--------------------------------
There is a U. S. Navy site that tracks tropical cyclones at 6-hourly
intervals which often includes pre and post-advisory positions. The
link to the site is:
http://www.nrlmry.navy.mil/atcf_web/doc_archives/>
Steve Young has compiled many of these tracks onto a single webpage
which is very user-friendly:
http://home.earthlink.net/~shy9/tc1.htm>
I'm sure there are other sites with available imagery available, and
as I learn of them, I will add the links to this list.
*************************************************************************
EXTRA FEATURE
In order to shorten the amount of typing in preparing the narrative
material, I have been in the habit of freely using abbreviations and
acronyms. I have tried to define most of these with the first usage
in a given summary, but I may have missed one now and then. Most of
these are probably understood by a majority of readers but perhaps a
few aren't clear to some. To remedy this I developed a Glossary of
Abbreviations and Acronyms which I first included in the August, 1998
summary. I don't normally include the Glossary in most months in
order to help keep them from being too long. If anyone would like to
receive a copy of the Glossary, please e-mail me and I'll be happy
to send them a copy.
*************************************************************************
AUTHOR'S NOTE: This summary should be considered a very preliminary
overview of the tropical cyclones that occur in each month. The cyclone
tracks (provided separately) will generally be based upon operational
warnings issued by the various tropical cyclone warning centers. The
information contained therein may differ somewhat from the tracking and
intensity information obtained from a "best-track" file which is based
on a detailed post-seasonal analysis of all available data. Information
on where to find official "best-track" files from the various warning
centers will be passed along from time to time.
The track files are not being sent via e-mail. They can be retrieved
from the archive sites listed below. (Note: I do have a limited e-mail
distribution list for the track files. If anyone wishes to receive
these via e-mail, please send me a message.)
Both the summaries and the track files are standard text files
created in DOS editor. Download to disk and use a viewer such as
Notepad or DOS editor to view the files.
The first summary in this series covered the month of October,
1997. Back issues can be obtained from the following websites
(courtesy of Michael Bath, Michael V. Padua, Michael Pitt, Chris
Landsea, and John Diebolt):
http://australiasevereweather.com/cyclones/>
http://www.typhoon2000.ph>
http://mpittweather.com>
ftp://ftp.aoml.noaa.gov/hrd/pub/landsea/padgett/>
http://www.tropicalcyclone2005.com/>
Another website where much information about tropical cyclones may
be found is the website for the UK Meteorological Office. Their site
contains a lot of statistical information about tropical cyclones
globally on a monthly basis. The URL is:
http://www.metoffice.gov.uk/weather/tropicalcyclone>
TROPICAL CYCLONE REPORTS AVAILABLE
JTWC now has available on its website the Annual Tropical Cyclone
Report (ATCR) for 2005 (2004-2005 season for the Southern Hemisphere).
ATCRs for earlier years are available also.
The URL is: http://metocph.nmci.navy.mil/jtwc.php>
Also, TPC/NHC has available on its webpage nice "technicolor"
tracking charts for the 2006 Atlantic and Eastern North Pacific
tropical cyclones; also, storm reports for all the 2006 Atlantic
and Eastern North Pacific cyclones are now available, as well as
track charts and reports on storms from earlier years.
The URL is: http://www.nhc.noaa.gov>
A special thanks to Michael Bath of McLeans Ridges, New South Wales,
Australia, for assisting me with proofreading the summaries.
PREPARED BY
Gary Padgett
E-mail: [email protected]
Phone: 334-222-5327
Kevin Boyle (Northwest Pacific)
E-mail: [email protected]
Simon Clarke (Northeast Australia/Coral Sea, South Pacific)
E-mail: [email protected]
*************************************************************************
*************************************************************************
|
Document: summ0708.htm
Updated: 30th November 2007 |
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