[Index]
Monthly Global Tropical Cyclone Summary September 2007
[Summaries and Track Data] [Prepared by Gary Padgett]
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Monthly Global Tropical Cyclone Summary September 2007 [Summaries and Track Data] [Prepared by Gary Padgett] |
MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
SEPTEMBER, 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.)
*************************************************************************
SEPTEMBER HIGHLIGHTS
--> Destructive Category 5 hurricane strikes Nicaragua
--> Typhoons strike Korea and China
--> Eight Atlantic tropical storms in September ties record for month
*************************************************************************
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 !!!!!!!!!!!!!
SOUTHERN HEMISPHERE TROPICAL CYCLONE NAMES
2007 - 2008 SEASON
TROPICAL CYCLONE NAMES for the AUSTRALIAN REGION
The Australian Bureau of Meteorology maintains three Tropical
Cyclone Warning Centres (TCWC): Perth, Western Australia; Darwin,
Northern Territory; and Brisbane, Queensland. Each centre is allotted
a separate list of tropical cyclone names for tropical cyclones forming
within its area of responsibility (AOR). In addition a TCWC located at
Port Moresby, Papua New Guinea (PNG)--a former Australian territory--
maintains a list of native names to assign to the very rare tropical
cyclones which form within its AOR.
The AORs of the respective centres are:
(1) Perth - 125E westward to 90E and south of 10S. Currently, and for
at least the next few years, the Perth TCWC will issue warnings for
any systems north of 10S and south and west of the Indonesian
islands.
(2) Darwin - 125E eastward to 138E and extending northward to the
equator. There is a little irregularity with the eastern border
in the Gulf of Carpentaria. The Darwin TCWC issues High Seas
Warnings for the entire Gulf of Carpentaria, but Brisbane issues
Tropical Cyclone Advices and names cyclones in the eastern portion
of the Gulf. Also, currently, and for at least the next few years,
the Darwin TCWC will issue warnings for any systems west of 125E
and within the Indonesian archipelago in the Banda, Flores, and
Java Seas.
(3) Brisbane - 138E eastward to 160E and generally south of 10S. The
northern border with the Port Moresby AOR is somewhat irregular.
(4) Port Moresby, PNG - immediate vicinity of the island of New Guinea
and eastward to 160E generally north of 10S although the southern
border is somewhat irregular.
Names for the 2007-2008 season (** indicates name has already been
assigned):
Perth Darwin Brisbane Port Moresby
-----------------------------------------------------------------------
Lee ** Helen ** Rebecca Guba **
Melanie ** Ira Sebastian Hibu
Nicholas Jasmine Tania Ila
Ophelia Kim Vernon Kama
Pancho Laura Whitney Lobu
Rosie Matt Alfred
Selwyn Narelle Blanch
Tiffany Oswald Caleb
Victor Penny Denise
Zelia Russell Ernie
Alison Frances
Billy Greg
Cathy Hilda
Damien Ivan
Ellie Joyce
TROPICAL CYCLONE NAMES for the SOUTHWEST INDIAN OCEAN
and the SOUTH PACIFIC OCEAN
The Tropical Cyclone Warning Centre (TCWC) at Nadi, Fiji, has
tropical cyclone warning responsibility for the South Pacific east of
160E and from the equator to 25S. The Meteorological Service of New
Zealand at Wellington has warning responsibility for waters south of
25S, but almost all tropical cyclones in this basin form north of 25S.
When a rare cyclone forms in the Wellington area of responsibility
(AOR), it usually will be assigned a name from the Fiji list (such as
was done for Tropical Cyclone Gita in February, 1999.)
Tropical cyclone warning responsibility for South Indian waters west
of 90E are shared by several TCWCs. The Regional Specialty
Meteorological Centre (RSMC) for the region is the office of Meteo
France on the island of La Reunion. However, following a long-standing
practice, the Sub-regional Tropical Cyclone Advisory Centres at Mauritius
and Madagascar share the responsibility for actually naming tropical
storms with Mauritius naming systems east of 55E and Madagascar covering
the area west of 55E. RSMC La Reunion issues warnings for the basin
independently of Mauritius and Madagascar, but only advises regarding
when or when not to assign a name to a developing cyclone.
Names for the 2007-2008 season (** indicates name has already been
assigned):
Southwest Indian South Pacific
-----------------------------------------------------------------------
Ariel ** Nungu Daman ** Nisha
Bongwe ** Ofelia Elisa ** Oli
Celina ** Pulane Funa ** Pat
Dama ** Qoli Gene ** Rene
Elnus ** Rossana Hettie Sarah
Fame ** Sama Innis Tomas
Gula ** Tuma Joni Vania
Hondo ** Uzale Ken Wilma
Ivan ** Vongai Lin Yasi
Jokwe Warona Mick Zaka
Kamba Xina
Lola Yamba
Marabe Zefa
***********************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for September: 1 tropical depression
4 tropical storms
3 hurricanes **
1 intense hurricane
** - one of these was treated operationally as a strong tropical storm
but was upgraded to hurricane status during post-storm analysis
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 September
----------------------------------------
The month of September was paradoxical: it was very active, very
quiet, and average all at the same time--depending on which parameters
one considers. Over the period 1950-2000, the average number of named
storms in September is 3.4--in 2007 there were 8, tying the record set
in September, 2002. The average numbers of hurricanes and intense
hurricanes over the same period are 2.4 and 1.3, respectively. In
September, 2007, there were 4 hurricanes and 1 intense hurricane. So as
far as numbers of storms and hurricanes go, the month was quite active.
However, in terms of the longevity of the storms, the month was well
below normal. For the 1950-2000 period, the average numbers of NSD, HD,
and IHD are 21.7, 12.3, and 3.0, respectively. September of 2007
featured 16.3 NSD, 3.5 HD, and 2.0 IHD. Most of the storms were quite
short-lived with Humberto, Jerry, Lorenzo and Melissa existing as a NS
for less than two days, and Gabrielle and Ingrid were at tropical or
subtropical storm intensity for not much more than two days.
So in the numbers of storms department (NS, H, IH), September was
160% of the 1950-2000 average. But in terms of the longevity parameters
(NSD, HD, IHD), the month was only 57% of normal. According to figures
from Phil Klotzbach and the CSU seasonal forecasting team, the NTC for
September, 2007, was 47%--very near the long-term average of 48% for the
month.
The main event of the month was Hurricane Felix, which made landfall
in northeastern Nicaragua as a potentially catastrophic Category 5
hurricane. Hurricane Humberto gained considerable attention when it
intensified from a tropical disturbance to a strong Category 1 hurricane
in less than 24 hours just offshore from the Texas coast. Humberto
became the first landfalling U. S. hurricane since Hurricane Wilma in
October, 2005. Tropical Storm Gabrielle was the only other tropical
cyclone during the month to make a U. S. landfall when it passed over
the Outer Banks of North Carolina. Late in the month, Lorenzo
strengthened just about as quickly as Humberto had done and made landfall
along the Mexican coast very near the same point where Hurricane Dean
had struck about a month earlier.
Strong upper-level LOWs were more frequent than usual across the
tropical Atlantic during September, and were responsible for the early
demise of storms Ingrid, Karen and Melissa by inducing strong westerly
shear over the cyclones. The formation of these three storms over the
eastern and central tropical Atlantic was consistent with what often
happens in very active seasons, and had the upper-level LOWs been absent
and a strong subtropical ridge been present, things could have been very
different for the Antilles and possibly the southeastern U. S.
Official TPC/NHC reports for all the 2007 tropical cyclones except
for Hurricanes Dean, Felix and Noel and Tropical Storm Erin are now
available online at the following URL:
http://www.nhc.noaa.gov/2007atlan.shtml>
I have written a more full report on Hurricane Felix. For the other
storms I have written shorter reports but have included some discussion
on various topics which I hope will be interesting. Links to all the
Wikipedia reports are included in the write-up for each individual
cyclone.
!!!!!!!!!! ADDENDUM TO AUGUST SUMMARY !!!!!!!!!!
In the August summary I included a write-up about an interesting low-
pressure area southeast of the New England coast at the end of August
and into the early days of September. (See the August summary for more
details.) The question was raised as to whether this system might
qualify for inclusion as an unnamed tropical storm. I asked Eric Blake
if this system (identified at the time as Invest 96L) was being
considered as a potential after-the-fact tropical storm.
The answer is that it is not. Following is Eric's reply:
"Perhaps it was a weak TD, but it is not being seriously considered as a
TS. There is no evidence of TS-force winds (that QuikScat pass doesn't
show reliable TS winds--those wind vectors are not the correct solution
for a cyclonic storm!) in any data source. The system from last year
(i.e., the unnamed July, 2006, storm) was much more wound up."
HURRICANE FELIX
(TC-06)
31 August - 5 September
-------------------------------------------
A. Synoptic History
-------------------
Felix formed from a tropical wave that moved westward off the coast
of Africa on 24 August. Little convective activity was noted for several
days, but by the 28th the system began to show signs of organization.
This trend toward improving convective organization continued over the
next few days, and on the afternoon of 31 August an Air Force Reserves
reconnaissance plane found a closed surface circulation with FLWs of
36 kts, equating to about 30 kts at the surface. Hence, advisories
were initiated on Tropical Depression 06 at 2100 UTC. The center of
TD-06 was initially located about 155 nm east-southeast of the Windward
Islands, moving toward the west at 14 kts. The convection continued
to consolidate during the night as the system moved through the southern
Windwards, and Tropical Storm Felix was christened at 0900 UTC on
1 September with the center located about 25 nm northwest of the island
of Grenada.
The storm was moving westward at a pretty good clip (16 kts) as it was
steered by a ridge to the north. Felix intensified rapidly and was
upgraded to a hurricane at 02/0000 UTC while located about 235 nm east
of Aruba. A reconnaissance plane had found 77-kt winds at a flight level
of 2286 m, and the SFMR found surface winds of 65 kts. A CP of 993 mb
was measured within a 30-nm wide eye. Felix passed just north of the
ABC islands as it continued to intensify. Within 24 hours after
initially reaching hurricane intensity, the storm had become a very
intense Category 5 hurricane on the Saffir/Simpson scale while located
approximately 340 nm southeast of Kingston, Jamaica.
TPC/NHC issued a special advisory at 03/0000 UTC. From the Discussion
Bulletin:
"Reports from a NOAA Hurricane Hunter aircraft indicate that Felix has
intensified and is now a Category 5 hurricane. The aircraft reported
peak flight-level winds of 152 kts, with peak SFMR winds of 142 kts in
the southwest quadrant. Higher SFMR winds were found in the northeast
quadrant, up to 163 kts, but these may have been contaminated by graupel.
A dropsonde released in the southwest quadrant landed in the northeast
quadrant, and this drop yielded a surface estimate of 139 kts based on
the lowest 150 m layer average. Based on these data, the peak surface
winds are estimated to be at least 145 kts. An eye sonde measured a
surface pressure of 936 mb with surface winds of 24 kts. Because of
the extreme turbulence and graupel that the aircraft experienced, the
mission is being aborted and the aircraft is returning to St. Croix."
Given that the drop which measured the 936 mb CP reported winds as
high as 24 kts, it was assumed that it missed the center of the eye.
The CP reported in the 0000 UTC special advisory was adjusted to 934 mb.
The MSW inferred from all the data is surprisingly high for a CP no lower
than 934 mb, and it seems likely there is a good chance the MSW could be
upped even higher during post-storm analysis and review. At its peak
Felix was a small cyclone, with hurricane-force winds extending outward
about 20 nm from the center and gales covering an area less than 200 nm
in diameter.
The pressure dropped as low as 929 mb at around 03/0900 UTC, but began
to rise thereafter as Felix underwent an eyewall replacement cycle. The
145-kt intensity was maintained for 18 hours, but the MSW began to drop
after 1200 UTC, falling to 115 kts by 04/0000 UTC. However, Felix
completed the eyewall cycle and began to steadily re-intensify as it
approached the Nicaraguan coast. At 04/0900 UTC the center of Felix was
only about 55 nm southeast of Cabo Gracias a Dios on the Nicaragua/
Honduras border. After having risen to 953 mb at 0000 UTC, the CP had
fallen to 939 mb and a reconnaissance plane had found a peak FLW of
148 kts, corresponding to 133 kts at the surface, and dropsonde data
analysis supported a surface wind of 132 kts. Based on these data, the
MSW was upped to 135 kts, and at 1200 UTC, shortly before landfall,
Felix was re-upgraded to Category 5 status with 140-kt winds. Aircraft
data supported 135 kts at 0700 UTC, and after that time the eye became
more distinct and the surrounding cloud tops cooled, resulting in an
increase in Objective T-numbers of 0.3.
Potentially-catastrophic Hurricane Felix made landfall around 1200 UTC
in extreme northeastern Nicaragua very near Punta Gorda, or about 15 km
north-northeast of Puerto Cabezas. Following landfall Felix began to
quickly weaken as it continued westward over the mountainous terrain
of northern Nicaragua. The storm had weakened to tropical storm status
by 05/0000 UTC, and the final NHC advisory was issued at 0900 UTC,
downgrading the system to a depression near Tegucigalpa, Honduras.
The official TPC/NHC report on Felix is not yet available online, but
the very detailed Wikipedia report on Hurricane Felix may be found at
the following link:
http://en.wikipedia.org/wiki/Hurricane_Felix_%282007%29>
B. Storm Impacts
----------------
Only minor damage from Felix was sustained in the southern Windward
Islands. The major impact from the hurricane was in Central America,
primarily in Nicaragua.
According to the Wikipedia report, damage was severe in Nicaragua and
Honduras. In Puerto Cabezas, Nicaragua, nearly every structure sustained
roof damage, and many buildings were destroyed. On the Miskito Cays,
which lie about 70 km off the coast of northeastern Nicaragua, every
house was completely destroyed. At least 133 persons are known to have
died, 130 of them in Nicaragua. Also, hundreds of others have been
reported missing. Over 9000 houses were destroyed, most in Puerto
Cabezas (also known as Bilwi). Inland flooding was also reported in
Honduras, particularly near Tegucigalpa and in the northwestern portion
of the nation.
C. Comparison with Hurricane Edith of 1971
------------------------------------------
It would be remiss not to call attention to the similarities between
Hurricane Felix and another intense Caribbean hurricane over a third of
a century earlier--Hurricane Edith of 1971. The two hurricanes
exhibited remarkable similarities in size, track, dates of occurrence,
and intensity. In fact, they could almost be called identical twins.
(1) Size - Like Felix, Edith was a very small tropical cyclone at its
peak. Reconnaissance crews likened the storm to a giant tornado
with a perfectly-formed eye only five miles in diameter.
(2) Track - Like Felix, Edith became a tropical depression just east
of the southern Windward Islands, passed very near Grenada and
later just north of the ABC islands, and eventually slammed into
northeastern Nicaragua slightly north of Felix' landfall point.
However, the similarity ends there. Instead of dissipating over
mountainous Central America, Edith veered to the west-northwest,
emerging into the Gulf of Honduras before making a second landfall
in extreme northern Belize. The storm then crossed the Bay of
Campeche, and for awhile it looked as if Edith would move into
northern Mexico as a minimal tropical storm and quietly dissipate.
However, when almost straddling the Mexican coastline, Edith veered
sharply to the north and later north-northeast, re-intensified, and
made landfall in western Louisiana as a Category 2 hurricane.
(3) Dates - Felix formed as a tropical depression on 31 August and made
landfall in Nicaragua on 4 September. Edith occurred only a few
days later by the calendar, forming on 6 September and making its
Nicaraguan landfall late on the 9th. Another slight difference
between the two storms is that Edith was not upgraded to tropical
storm status quite as far east as Felix. The earlier storm reached
tropical storm intensity while passing just north of the ABC islands
whereas Felix was reaching hurricane intensity in the same location.
(4) Intensity - The Atlantic Best Track file gives for Edith a peak MSW
of 140 kts with a minimum CP of 943 mb. Admittedly, 140 kts has
always seemed a bit too high for 943 mb. However, Felix' dimensions
of 934 mb and 145 kts makes Edith's peak parameters much more
believable. Operationally, Edith's peak MSW was reported at
150 kts at one point, but this was apparently reduced during post-
storm analysis, very possibly because of the rather high minimum
central pressure.
The meteorological service in British Honduras (now Belize) reported
that there were 100 fatalities and 7000 persons left homeless in the
Cape Gracias area as a result of Hurricane Edith, so the impact of the
two hurricanes in that region seems to also be similar. (Note: The
above information on Hurricane Edith is taken collectively from the
author's memory and from the preliminary report on the storm written
by John R. Hope, who was then a forecaster at NHC.)
(Report written by Gary Padgett)
SUBTROPICAL/TROPICAL STORM GABRIELLE
(TC-07)
4 - 12 September
--------------------------------------------------------
A. Synoptic History
-------------------
A non-tropical LOW formed off the southeastern U. S. coast on
3 September and for the next several days moved slowly eastward in the
general direction of Bermuda. The LOW became better defined late on the
7th and was upgraded to Subtropical Storm Gabrielle at 08/0000 UTC while
located about 360 nm southeast of Cape Hatteras. Gabrielle moved north-
westward and slowly acquired tropical characteristics and was classified
as a tropical storm at 2100 UTC that day. The cyclone strengthened
early on the 9th and reached a peak intensity of 50 kts while located
just south-southeast of Cape Lookout, North Carolina. A few hours later,
the center made landfall along the Cape Lookout National Seashore.
After making landfall, Gabrielle turned northeastward and weakened
due to land interaction and northerly wind shear. The storm moved back
out over the Atlantic early on 10 September near Kill Devil Hills, North
Carolina, and weakened to a tropical depression a few hours later. On
the 11th the circulation became ill-defined and the depression dissipated
about 260 nm south of Nova Scotia. Heavy rainfall associated with
Gabrielle was confined to a rather small area near Cape Lookout.
Overall, the impacts from Tropical Storm Gabrielle in eastern North
Carolina were minimal.
B. Discussion
-------------
Operationally, the highest winds reported for Gabrielle were 45 kts.
During post-storm analysis, it was determined that the storm reached a
peak MSW of 50 kts. This was based on a peak 925-mb FLW of 61 kts and
a later 850-mb FLW of 66 kts on the morning of 9 September. A dropsonde
around the same time reported a surface wind of 49 kts. Even though
Gabrielle's intensity is estimated at 50 kts around the time of landfall,
these strong winds never reached the coast due to northerly shear which
kept the strongest thunderstorm activity offshore for several hours.
The highest sustained wind measured in eastern North Carolina was 38 kts
at Frisco Pier. A gust to 46 kts was reported at Cape Hatteras, and a
gust to 53 kts was observed at Ocracoke. Four to eight inches of rain
fell across southern Craven and eastern Carteret Counties with a
maximum of 9.03 inches (229.4 mm) near Harlowe in Carteret County.
Rich Henning, a member of the 53rd Weather Reconnaissance Squadron,
was on the flight into Gabrielle which measured the 61-kt FLW early on
the 9th. In Rich's opinion, what caused the sudden intensification of
the storm was a mesoscale convective event which just happened to be
superimposed near the core of a tropical cyclone, but which did not
result in a sustained intensification of the "parent vortex". The
plane found an environment with lots of shear, dry air, and trough
interaction--bad things for a barotropic vortex but a trigger for
thunderstorm activity. Rich notes that a similar convective burst led
to the intensification of Tropical Storm Marco of 1996 to hurricane
intensity. As soon as the convective feature dissipated, Marco weakened
back to a fairly weak, sheared tropical storm.
During the several days when the parent LOW which spawned Gabrielle
was meandering around between the U. S. and Bermuda, there were some
reports circulating in the media that the LOW might spawn a Category 2
hurricane which would race up the coast toward New York. Whether or not
any of the numerical models were suggesting this, I do not know.
However, NHC never at any time forecast Gabrielle to reach hurricane
intensity nor to pose a significant threat to the U. S. coast.
The official TPC/NHC report on Tropical Storm Gabrielle, authored by
Daniel Brown, is now available online on NHC's website. Some of the
information above was taken from this report.
Also, the Wikipedia report on Gabrielle may be found at the following
link:
http://en.wikipedia.org/wiki/Tropical_Storm_Gabrielle_%282007%29>
(Report written by Gary Padgett)
HURRICANE HUMBERTO
(TC-09)
12 - 14 September
--------------------------------------
A. Synoptic History
-------------------
A frontal trough moved offshore of southern Florida on 5 September
with the western end moving slowly westward for the next several days,
occasionally producing disorganized thunderstorm activity. By the 11th
the system had reached the northwestern Gulf of Mexico. Early the next
day thunderstorms rapidly increased near the trough and a tropical
depression formed about 105 nm south of Galveston. The depression
became a tropical storm a few hours later as it moved slowly northward
and was named Humberto. The newly-christened cyclone turned slightly
to the north-northeast and continued to rapidly intensify, reaching
hurricane intensity early on 13 September while located about 25 nm
south of High Island, Texas. Hurricane Humberto made landfall just east
of High Island around 0700 UTC at its peak intensity of 80 kts. The
storm then moved over extreme southeastern Texas and southwestern
Louisiana and weakened to a tropical storm at 13/2100 UTC while located
about 120 km west-northwest of Lafayette, Louisiana. The cyclone soon
weakened to a tropical depression near Alexandria, Louisiana, and
dissipated over central Mississippi on the 14th. One fatality is
directly attributable to Humberto and U. S. damage is estimated at
about $50 million.
B. Discussion
-------------
Based on the analyzed Best Track in the official TPC/NHC storm report,
Humberto's MSW climbed from 25 to 80 kts in 24 hrs. This represents the
most rapid intensification on record for a system from below tropical
storm intensity to hurricane force while located so near a coastline.
With a hurricane making landfall when 24 hours earlier there was not
even a tropical depression, it was natural that some criticism would be
leveled at NHC by the media. But it has to be kept in mind that NHC is
chartered to issue warnings on tropical (and subtropical) cyclones, and
said warnings can not be issued when a tropical cyclone does not exist!
It is a fact of nature that sometimes tropical weather systems can form
and intensify with amazing (and frightening) rapidity.
Following is a survey of some Atlantic tropical cyclones which
intensified from below tropical storm intensity to hurricane status
within 24 hours or less. (Note: All the MSW values given below are taken
from the current official Atlantic Best Track file. Some of the values
for older cyclones are subject to be modified during the on-going
re-analysis.)
(1) Storm #3, 26 June 1936 - The first data point in the Best Track is
already of tropical storm intensity. However, assuming that 6 hrs
prior it would have been around 30 kts, this storm intensified from
30 to 65 kts in 12 hrs, and from 30 to 70 kts in 18 hrs. AND, this
late June system formed and strengthened right off the Texas coast
and quickly moved inland.
(2) Cindy, 16 September 1963 - Like the 1936 storm, Cindy developed and
quickly intensified right off the Texas coast and moved inland. The
first data point gives a MSW of 40 kts, but again, assuming 30 kts
for 6 hrs earlier, Cindy intensified from 30 to 70 kts in 18 hrs.
(3) Arlene, 1 August 1963 - Arlene's rapid intensification occurred in
the tropical Atlantic several hundred miles east of the Windward
Islands. This cyclone's MSW jumped from 30 to 70 kts in 18 hrs, and
from 30 to 90 kts in 24 hrs.
(4) Flora, 29 September, 1963 - The developing Flora's intensity rose
from 30 to 70 kts in 18 hrs, and from 30 to 85 kts in 24 hrs while
located a few hundred miles east of Trinidad.
(5) Blanche, 11 August 1969 - While located off the U. S. Eastern Sea-
board, Blanche's MSW jumped from 30 to 75 kts within 12 hrs.
(6) Alberto, 3 June 1982 - Moving from the northwestern Caribbean Sea
past western Cuba into the southeastern Gulf of Mexico, Alberto's
intensity climbed from 30 to 75 kts in 18 hrs, and from 25 to 75 kts
in 24 hrs.
(7) Lorenzo, 27 September 2007 - Coming only a couple weeks after
Humberto, Lorenzo became the second rapidly intensifying Gulf of
Mexico storm for the month of September. Lorenzo's intensity rose
from 30 to 70 kts in 18 hrs while located just off the Mexican
coastline.
(8) Celia, 1 August 1970 - Hurricane Celia, which later devastated the
city of Corpus Christi, Texas, is the poster child for how rapidly
a tropical depression can intensify. While located in the south-
central Gulf of Mexico, Celia's MSW spurted from 30 to 100 kts in
only 18 hrs! The 100-kt MSW at 0000 UTC 2 August was accompanied
by a CP of 965 mb, which matches well. Celia's CP fell from 1007 to
965 mb in 24 hrs, and from 990 to 965 mb in only 6 hrs.
The official TPC/NHC report on Hurricane Humberto, authored by Eric
Blake, is now available online on NHC's website. Some of the information
above was taken from this report.
Also, the Wikipedia report on Humberto may be found at the following
link:
http://en.wikipedia.org/wiki/Hurricane_Humberto_%282007%29>
(Report written by Gary Padgett)
TROPICAL STORM INGRID
(TC-08)
12 - 18 September
-----------------------------------------
A. Synoptic History
-------------------
A large tropical wave exited the western coast of Africa on
6 September but ran into strong easterly shear which inhibited
development for several days. On the 9th a broad area of low pressure
developed along the wave axis about midway between Africa and the Lesser
Antilles. Environmental conditions gradually became more favorable as
time wore on and convective activity became persistent near the LOW
center on 11 September. By the early morning of the 12th, when the
LLCC was centered about 975 nm east of the Lesser Antilles, the system
had acquired sufficient organization to be designated as a tropical
depression. The system moved on a general west-northwesterly track
within weak steering flow along the southern periphery of a mid-
tropospheric ridge. Despite moderate vertical wind shear, the
cyclone continued to show improved organization and was upgraded to
Tropical Storm Ingrid during the evening of 13 September while centered
a few hundred miles east of the Lesser Antilles. Ingrid reached its
estimated peak intensity of 40 kts early on the morning of the 14th.
Later that day, shear increased and Ingrid weakened back to depression
status at 1800 UTC 15 September. The strong shear persisted and Ingrid
degenerated to a broad remnant LOW early on the 17th about 140 nm east-
northeast of Antigua.
NOTE: The initial advisories on Tropical Depression 08 (pre-Ingrid) and
Tropical Depression 09 (pre-Humberto) were both issued at the same time:
at 1500 UTC on 12 September. The decision to initiate advisories on the
tropical Atlantic depression had been made early in the morning, and that
system had already been identified as TD-08 on NRL's website before it
was discovered that the Gulf of Mexico system had become a tropical
depression.
B. Discussion
-------------
The primary difference between the analyzed "best track" for Ingrid
and the operational track was the time that the system reached tropical
storm intensity. Operationally, Ingrid was upgraded to tropical storm
status at 14/0300 UTC, but the "best track" backs up the onset of
tropical storm-force winds to 13/0600 UTC. There was a hint in the
NHC discussion for 13/1500 UTC that TD-08 might have briefly been a
tropical storm earlier based on some unflagged 35-kt wind vectors from
QuikScat, but by the 1500 UTC advisory time the satellite signature had
degraded some, suggesting weakening.
The peak intensity for Ingrid in the "best track" has been left at
40 kts, which was the peak operational intensity. This is a little
surprising, given that at 14/1118 UTC the SFMR reported winds of 51 kts
in the southwest quadrant, and concurrent T-numbers from both TAFB and
SAB were T3.0 (45 kts).
Ingrid represented what was, climatologically speaking, the final
candidate of the 2007 hurricane season for an intense hurricane to
threaten populated areas or make landfall in the western portion of the
Atlantic basin. Karen and Melissa formed during the final week of
September, and again from a climatological perspective, had only a low
probability (especially Melissa) of moving all the way across the
Atlantic to threaten or strike the Caribbean islands or the U. S. coast.
The official TPC/NHC report on Tropical Storm Ingrid, authored by
Michelle Mainelli, is now available online on NHC's website.
Also, the Wikipedia report on Ingrid may be found at the following
link:
http://en.wikipedia.org/wiki/Tropical_Storm_Ingrid_%282007%29>
(Report written by Gary Padgett)
TROPICAL DEPRESSION
(TC-10)
18 - 22 September
---------------------------------------
A. Synoptic History
-------------------
A decaying frontal boundary became stationary off the southeastern
U. S. coast on 17 September. The next day, an upper-level LOW formed
over Florida and the eastern Gulf of Mexico with a westward-moving
tropical wave moving over the Bahamas. These features combined to
produce a weak area of low-pressure over the western Bahamas later
on the 18th. The system moved slowly westward over Florida and into
the eastern Gulf of Mexico during 19-20 September. On 21 September
convection increased near the surface LOW, and a subtropical depression
formed around 1200 UTC about 40 nm southwest of Apalachicola, Florida.
The depression gained tropical characteristics and was classified as
a tropical depression at 1800 UTC. The estimated MSW never exceeded
30 kts and the depression made landfall around 22/0000 UTC near Fort
Walton Beach, Florida, and dissipated a few hours later. Impacts in
the areas along the path of the depression were minimal.
B. Discussion
-------------
Again, as with Humberto, there was some criticism leveled at NHC for
its seeming slowness in declaring a depression and initiating advisories,
given how close to the coast the system was. At the time of the initial
advisory on Subtropical Depression 10, the center was only about 40 nm
southwest of Apalachicola, Florida, although it was moving away from that
reference point. Emergency Managers in the Florida Panhandle were faced
with a system very near the coast which was forecast to intensify into a
tropical storm and make landfall within 12 to 24 hours.
The issue here is the rather "fuzzy" and subjective definition of a
subtropical depression (or a tropical depression for that matter).
Whereas the tropical (and subtropical) storm category as well as the
hurricane are defined by a minimum wind speed criterion, there is no
such lower MSW bound for the depression category. Factors such as
the depth and amount of convection, organization of the convection,
"tightness" of the circulation, thermal properties, etc all come into
play in deciding whether to "start" a depression or continue to refer
to a system as a low-pressure area (either tropical or non-tropical).
And the process is inherently subjective because some of these criteria
cannot be easily quantified.
In the regular Tropical Weather Outlooks the system was referred to
as a 'weak low-pressure system' on the 19th and 20th. During the
evening of 20 September, after a reconnaissance flight into the LOW,
it was referred to as a 'well-defined low-pressure system', thus
highlighting the increasing organization. Even early on the 21st, it
seems that the degree of convective organization had not yet progressed
to the point that the forecaster felt advisories were warranted.
However, if the system had been upgraded to a depression of either
variety sooner, there would have been more media hype; and given that
it essentially turned out to be a non-event, no doubt NHC would have
then been criticized for "crying wolf". In the author's opinion, NHC
handled this system very well.
The official TPC/NHC report on Tropical Depression 10, authored by
Jamie Rhome, is now available online on NHC's website.
Also, the Wikipedia report on TD-10 may be found at the following
link:
http://en.wikipedia.org/wiki/Tropical_Depression_Ten_%282007%29>
(Report written by Gary Padgett)
SUBTROPICAL/TROPICAL STORM JERRY
(TC-11)
20 - 25 September
----------------------------------------------------
A weak non-tropical LOW had formed in the central North Atlantic
roughly half-way between Bermuda and the Azores as early as 20 September.
Over the next few days the LOW drifted eastward. A Tropical Weather
Outlook on the 20th mentioned the system and that it was being monitored
for possible tropical or subtropical development. By the morning of the
22nd the system had become a little better organized, but environmental
conditions were only marginally favorable for development. Advisories
were initiated on Subtropical Depression 11 at 0900 UTC on 23 September,
and the system was upgraded to Subtropical Storm Jerry six hours later.
Jerry at the time was located approximately 925 nm west of the Azores.
The system was treated as a subtropical cyclone since it was well-
involved with an upper-level LOW. Moving slowly northward, Jerry
was reclassified as a tropical storm at 24/0300 UTC as thunderstorm
activity increased near the center. The cyclone never strengthened
above minimal tropical storm intensity of 35 kts, and weakened back
to a depression later on the 24th as it accelerated northeastward
ahead of an approaching cold front.
Tropical Depression Jerry dissipated late on the 24th when it lost
its closed circulation about 700 nm northwest of the Azores. However,
on the final advisory, issued at 25/0300 UTC, Jerry was operationally
re-upgraded to a tropical storm, although the Best Track does not
reflect this since the system no longer had a closed circulation. A
QuikScat pass at 24/2136 UTC had revealed that Jerry's circulation had
opened up into a sharp trough within southwesterly flow ahead of a
large, extratropical LOW. However, as Jerry accelerated during the
evening of the 24th, QuikScat data indicated that winds at the base of
the trough increased to about 40 kts. Presumably as a precaution to
any shipping interests, Jerry underwent an apparent upgrade back to
tropical storm intensity, but the NHC discussion made it plain that the
system was no longer a tropical cyclone. Just an interesting little
vicissitude in the life of what was probably the least-significant
tropical cyclone of 2007.
The official TPC/NHC report on Tropical Storm Jerry, authored by
Lixion Avila, is now available online on NHC's website.
Also, the Wikipedia report on Jerry may be found at the following
link:
http://en.wikipedia.org/wiki/Tropical_Storm_Jerry_%282007%29>
(Report written by Gary Padgett)
HURRICANE KAREN
(TC-12)
25 - 30 September
----------------------------------------
A tropical wave departed the west coast of Africa on 21 September
and spawned a large area of disturbed weather. The system gradually
increased in organization and advisories were initiated on Tropical
Depression 12 at 25/0300 UTC with the center located 1475 nm east of
the southern Windward Islands. Six hours later the depression was
upgraded to Tropical Storm Karen. Karen moved west-northwestward
across the tropical Atlantic and strengthened into a minimal hurricane
on the 26th while centered about 1050 nm east of the southern Windward
Islands. However, a little later that day southwesterly wind shear
associated with a sharp upper-level trough caused Karen to begin
weakening. As the shear increased over the next couple of days, the
cyclone continued to lose organization. Karen eventually weakened to
a tropical depression on the 29th and dissipated later that day about
425 nm east of the Leeward Islands. A remnant area of showers and
squalls lingered near and east of the Leewards for a few more days.
Operationally, Karen was treated as a strong tropical storm with a
peak MSW of 60 kts. A NOAA Hurricane Hunter plane investigating Karen
during the evening of the 26th found surface winds of 62 kts. Given
that the storm's satellite signature had degraded significantly from
earlier in the day, it was inferred that Karen had been of minimal
hurricane intensity on the morning of 26 September. A decision was
made during post-season analysis to posthumously upgrade Karen to a
hurricane, making a total of six hurricanes for the 2007 Atlantic
season.
From the beginning of regular operational naming of tropical cyclones
in the Atlantic in 1950 through the year 2002, only one named tropical
storm was upgraded to hurricane status posthumously--Floyd of 1993.
However, Karen is the fourth such hurricane to be upgraded after-the-fact
since 2003, the others being Erika of 2003, Gaston of 2004, and Cindy of
2005. (Note: There were two unnamed hurricanes added to the official
roster of tropical cyclones in 1954 and 1959, and of course there is the
famous unnamed hurricane of 1991 (Perfect Storm), which was deliberately
left unnamed and treated as a non-tropical system operationally in order
not to confuse the public.)
The official TPC/NHC report on Hurricane Karen, authored by Richard
Pasch, is now available online on NHC's website.
Also, the Wikipedia report on Karen may be found at the following
link:
http://en.wikipedia.org/wiki/Hurricane_Karen_%282007%29>
(Report written by Gary Padgett)
HURRICANE LORENZO
(TC-13)
25 - 28 September
-------------------------------------
A tropical wave which had crossed the Atlantic and Caribbean Sea
eventually made its way into the southwestern Gulf of Mexico by late
September, spawning a tropical depression on the 25th about 150 nm
east-northeast of Tuxpan, Mexico. Although initially forecast to
strengthen into a tropical storm fairly quickly, Tropical Depression 13
spent a couple of days meandering around the Bay of Campeche without
developing. However, a reconnaissance flight into the depression on
the late morning of 27 September found that the system had strengthened
into a 50-kt tropical storm, which was named Lorenzo. Lorenzo at the
time was located about 115 nm east-southeast of Tuxpan. The cyclone
quickly intensified, reaching hurricane status during the evening of
the 27th. Lorenzo peaked at 70 kts before weakening slightly just prior
to making landfall around 0500 UTC 28 September near Tecolutla--about
65 km southeast of Tuxpan. Once inland the cyclone quickly weakened
and dissipated later that day. The Mexican government reported that
six fatalities were attributable to Hurricane Lorenzo.
Based on the analyzed Best Track, Lorenzo's MSW increased from 30 kts
to 70 kts within an 18-hour period. Operationally, the winds jumped from
30 kts to 65 kts in 12 hours. (See the discussion above in the report
for Hurricane Humberto for further examples of rapidly intensifying
tropical cyclones.) Like Humberto, Lorenzo was very near the coastline
in the western Gulf of Mexico when it underwent rapid intensification
from a tropical depression to a Category 1 hurricane. Other than the
fact that one struck the U. S. while the other struck Mexico, the main
difference was that in the case of Lorenzo, a tropical depression had
been present for two days and had been consistently forecast to intensify
into a tropical storm, whereas in the case of Humberto, no tropical
depression, nor likely even a well-defined LOW, had existed 24 hours
prior to Humberto's landfall as a strong Category 1 hurricane.
The official TPC/NHC report on Hurricane Lorenzo, authored by James
Franklin, is now available online on NHC's website.
Also, the Wikipedia report on Lorenzo may be found at the following
link:
http://en.wikipedia.org/wiki/Hurricane_Lorenzo_%282007%29>
(Report written by Gary Padgett)
TROPICAL STORM MELISSA
(TC-14)
28 September - 2 October
--------------------------------------------
Tropical Storm Melissa was the final 2007 tropical cyclone to form
in the deep tropical Atlantic, and like its predecessors Ingrid and
Karen, was another senseless victim of vertical shear. The parent
tropical wave left the coast of Africa on the 26th with an area of low
pressure forming the next day near the Cape Verde Islands. Convection
increased abruptly early on the 28th and the system was classified as a
tropical depression at 28/1500 UTC, centered about 100 nm west-southwest
of the southernmost Cape Verdes. The depression strengthened slightly
while inching westward, and was upgraded to Tropical Storm Melissa at
29/0900 UTC. Melissa maintained tropical storm status for only about a
day, weakening to a depression on 30 September within an environment of
increasing westerly wind shear. The depression accelerated somewhat
toward the west-northwest as convection became intermittent, and later
on the 30th the depression degenerated to a remnant LOW about 475 nm
west of the Cape Verde Islands.
The remnant LOW continued to move west-northwestward for several days
into the central North Atlantic. Convection continued to flare up in
association with the LOW, and Dvorak numbers from SAB briefly increased
to T2.0/2.0 on 1 October. The final reference to the system in a High
Seas Forecast was at 04/0600 UTC, placing the weak LOW near 22N/50W.
However, the official analyzed Best Track for Melissa tracks the remnant
LOW to near 25N/54W at 05/1800 UTC. Operationally, Melissa was carried
as a tropical storm for 30 hours, peaking at 40 kts at 30/0000 UTC. But
in the Best Track, Melissa's tenure as a tropical storm is only 24 hours,
and the peak MSW has been reduced to 35 kts.
The official TPC/NHC report on Tropical Storm Melissa, authored by
Richard Knabb, is now available online on NHC's website.
Also, the Wikipedia report on Melissa may be found at the following
link:
http://en.wikipedia.org/wiki/Tropical_Storm_Melissa_%282007%29>
(Report written by Gary Padgett)
*************************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for September: 1 tropical depression
1 tropical storm
2 hurricanes **
** - one of these formed in August and was covered in the August summary
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 September
-------------------------------------------------
As the month of September began, Tropical Depression Gil was weakening
well to the southwest of Baja California, while Tropical Storm Henriette,
later to become a hurricane, was gathering strength just off the Mexican
coast. Henriette later struck the southern Baja Peninsula and mainland
Mexico as a Category 1 hurricane. The reports on Gil and Henriette can
be found in the August summary.
As was the case with most months during the 2007 season, tropical
cyclone activity in the Northeast Pacific basin was below normal. The
September averages for the period 1971-2006 are 3.5 NS, 2.2 H, and
1.1 IH. September of 2007 produced two named storms with one of these
becoming a Category 1 hurricane. Both Hurricane Ivo and Tropical Storm
Juliette formed far to the south of the southern tip of Baja California
and moved northwestward. Ivo began the process of recurvature and at
one point was considered a potential threat to the Peninsula, but it
began to weaken and dissipated just west of Cabo San Lucas. Tropical
Storm Juliette moved north-northwestward to a position west of the
southern Baja Peninsula, but stalled and weakened with the remnant LOW
drifting southeastward.
One other tropical cyclone formed during the month, Tropical
Depression 13E. This depression originated from a tropical wave which
left the western coast of Africa on 27 August and reached the Eastern
North Pacific on 7 September. It continued to move westward with little
development until 18 September, when the associated thunderstorm activity
became better organized. A tropical depression formed on the 19th about
1040 nm west-southwest of Cabo San Lucas. The cyclone moved slowly
westward and weakened to a remnant LOW the next day about 1185 nm west-
southwest of Cabo San Lucas. The remnant LOW meandered around for
several days with occasional flare-ups of convection, but never became
re-organized enough to warrant the resumption of advisories. By early
on 25 September the remnant LOW had opened up into a trough from 14N to
21N along 130W.
The official TPC/NHC reports for all 2007 Northeast Pacific basin
tropical cyclones except for Hurricane Flossie are now available on
NHC's website at the following URL:
http://www.nhc.noaa.gov/2007epac.shtml>
HURRICANE IVO
(TC-12E)
18 - 24 September
-------------------------------------
Hurricane Ivo formed from disturbed weather associated with a tropical
wave which had left the coast of Africa on 1 September and eventually
moved into the Eastern North Pacific on the 15th. The system had
acquired sufficient convective organization that advisories were
initiated on Tropical Depression 12E at 1500 UTC on 18 September,
locating the center approximately 390 nm south-southwest of Manzanillo,
Mexico. The depression was upgraded to Tropical Storm Ivo on the
afternoon of 18 September as it moved west-northwestward. Ivo reached
hurricane intensity during the afternoon of 20 September while centered
approximately 450 nm south-southwest of Cabo San Lucas on the southern
tip of the Baja California Peninsula. Rounding the periphery of a mid-
level high pressure ridge, Ivo turned northwestward and then northward,
reaching its peak intensity of 70 kts around midday on the 20th while
located about 370 nm southwest of Cabo San Lucas.
Ivo subsequently turned north-northeastward on 21 September and began
to weaken under the influence of westerly shear. Ivo had weakened to a
tropical storm by 22/0000 UTC and continued moving slowly toward the
north-northeast for the next couple of days. The cyclone weakened into
a tropical depression early on the 23rd about 130 nm west-southwest of
Cabo San Lucas. Turning eastward Ivo continued to weaken and degenerated
into a remnant LOW later that day about 80 nm southwest of the southern
tip of Baja California. The remnant LOW continued to linger in the same
area for another day or so as it continued to weaken.
No damage or casualties are known to have resulted from Hurricane Ivo.
The official TPC/NHC report on Hurricane Ivo, authored by James
Franklin, is now available on NHC's website.
(Report written by Gary Padgett)
TROPICAL STORM JULIETTE
(TC-14E)
29 September - 2 October
--------------------------------------------
A tropical wave departed the west coast of Africa on 12 September,
trekked westward across the tropical Atlantic and Caribbean Sea, and
eventually entered the Eastern North Pacific on 23 September. Convective
organization gradually improved and an area of low pressure formed on
27 September approximately 300 nm southwest of Acapulco, Mexico. The
convection continued to become better organized and a depression is
estimated to have formed at 0000 UTC 29 September about 365 nm south-
west of Manzanillo, Mexico. (The first advisory on TD-14E was issued
at 0900 UTC on the 29th.) The depression intensified to a tropical
storm later that day and reached its peak intensity of 50 kts at
1200 UTC on 30 September. Operationally, the MSW at 30/1200 UTC was
estimated at 40 kts, and the peak operational MSW of 45 kts was reached
at 30/1800 UTC when Juliette was centered about 300 nm southwest of
Cabo San Lucas.
After reaching its peak, Tropical Storm Juliette turned more to the
north-northwest as strong vertical shear, cooler SSTs, and a more
stable air mass resulted in weakening. The final advisory on Juliette
was issued at 0300 UTC on 2 October with the center located about 330 nm
west of Cabo San Lucas. The remnant LOW remained quasi-stationary for
a day or so following issuance of the last advisory, then began drifting
toward the south or southeast. By the morning of 4 October it had become
quite weak and diffuse.
The official TPC/NHC report on Tropical Storm Juliette, authored by
Robert Berg and Jamie Rhome, is now available on NHC's website.
(Report written by Gary Padgett)
*************************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for September: 3 tropical depressions **
2 tropical storms
3 typhoons ++
1 super typhoon
** - two of these classified as tropical depressions by JMA only
++ - one of these formed in August and was covered in the August summary;
another was classified as a typhoon by JTWC only and reached typhoon
intensity in early October
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.
Also, in recent months Derrick Herndon of CIMSS has been sending me
increasingly detailed reports of surface observations, along with some
additional analysis. A special thanks to Derrick for his inputs.
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 September
-------------------------------------------------
September was an active month in the Northwest Pacific basin. As the
month opened Typhoon Fitow was drifting slowly westwards well to the
southeast of Japan. The storm later turned toward the northwest,
recurved, and made landfall on the Izu Peninsula as a minimal typhoon
late on the 6th, subsequently moving over the northernmost Japanese
island of Hokkaido. The report on Typhoon Fitow may be found in the
August summary.
Five named storms formed during September. Tropical Storm Danas
formed northwest of Wake Island on the 7th and became a strong tropical
storm as it recurved well to the east of Honshu. The extratropical
remnants of Danas moved all the way across the North Pacific and affected
the southeastern Alaskan coastline. Typhoon Nari formed on the 13th
between Taiwan and the northern Marianas and eventually made a
destructive strike on South Korea. Super Typhoon Wipha formed near
mid-month, passed just north of Taiwan, and made a destructive strike
in mainland China near the border between Fujian and Zhejiang Provinces.
Tropical Storm Francisco formed on 23 September in the northern South
China Sea and made landfall in northern Hainan Dao. The final cyclone
of September was somewhat unusual. A broad monsoon depression formed
in the Philippine Sea and was named Hanna by PAGASA. Hanna was upgraded
to a tropical storm by that agency prior to its striking Luzon. The
system weakened and its remnant circulation moved out into the South
China Sea where it began to redevelop. It was named Lekima by JMA early
on 30 September and continued westward, eventually making landfall in
Vietnam. JMA never upgraded Lekima to typhoon status, but JTWC did so,
estimating the peak MSW (1-min avg) at 70 kts on 2 October. Reports on
all these cyclones, written primarily by Kevin Boyle, follow.
In addition to the named tropical cyclones, three additional systems
were monitored as tropical depressions by one agency or another. The
first of these operated from 9-14 September as reported in High Seas
bulletins issued by JMA. The system was first reported as a weak
tropical depression at 09/0600 UTC when located about 265 nm west-
southwest of Okinawa. The LOW moved in the general direction of Okinawa
and the winds were upped to 30 kts at 10/1800 UTC when it was centered
only about 55 nm south-southwest of the island. The depression passed
only about 20 nm to the south around 11/0600 UTC and continued toward
the east-northeast, reaching a point about 100 nm east-northeast of
Okinawa by 11/1800 UTC. The system then came to a halt and turned back
to the west, passing around 75 nm north of Okinawa on the 12th. A
slow drift toward the west-northwest continued, and the depression began
to weaken on the 13th, being downgraded to weak depression (25 kts)
status at 13/1800 UTC when located about 260 nm northwest of Okinawa.
The final reference to the system was at 14/0600 UTC.
Although no warnings were issued on this depression by JTWC, the
system was carefully monitored by the agency and rather extensive remarks
included in the STWOs. Normally I don't include so much material for
non-developing systems, but this disturbance was rather interesting
and unusual. JTWC first referenced the system at 10/0600 UTC, assigning
a development potential of 'poor'. An elongated and poorly-organized
LLCC was near the southern end of an approaching mid-latitude baroclinic
trough. The potential for development was upped to 'fair' at 10/2200 UTC
when the LLCC had become better defined and a small area of deep
convection had formed east of the center. There was some interaction
with the trough and vertical shear was moderate to strong. By 11/0600
UTC the LLCC had become more elongated and the deep convection had taken
on a more frontal appearance, so the development potential was reduced
to 'poor'. By 11/2000 UTC drier subsident air in the mid-levels and
cold-air advection were noted to the west of the center. The LOW was
assessed as a shallow warm-core system in the process of transforming
into an extratropical LOW. By 12/0600 UTC the convection had dissipated
and the system was dropped as a suspect area from the STWOs.
However, at 12/2100 UTC the disturbance was added back as a suspect
area with a 'poor' development potential. Convective banding was
wrapping into a well-defined LLCC located just north of the subtropical
ridge axis in the presence of good poleward outflow. By 13/0000 UTC
deep convection had developed over the LLCC, which had separated from a
shear line to the northeast, and an upper-level analysis indicated that
the system was warm-core to 700 mb, although weak cold-air advection was
still present to the west. Therefore, a TCFA was issued and the
development potential raised to 'good'. By 13/1700 UTC, shear had
increased and the deep convection had become sheared to the northeast of
the LLCC, but there was still a potential for rapid development should
the shear relax, given the well-defined LLCC and abundant warm water.
However, by 2100 UTC deep convection had dissipated near the center,
which was rapidly weakening and elongating, so the TCFA was cancelled and
the disturbance deleted as a suspect area. The system at this time was
located only about 175 nm southeast of Shanghai, China.
The second depression was treated as a tropical depression by both
JMA and JTWC, the latter agency designating it as TD-14W. An area of
convection developed on 19 September about 60 nm south-southwest of Yap.
A fairly well-defined LLCC was present under an area of good upper-level
divergence, and 24-hour pressure falls of 2 to 3 mb were noted at Yap.
JMA first referenced the system as a weak tropical depression at 19/1200
UTC. The system continued to show increased organization, and JTWC
issued a TCFA at 19/2000 UTC with the center then located about 40 nm
west of Yap. The first warning on Tropical Depression 14W was issued
at 20/1200 UTC, placing the 30-kt center about 460 nm west of Guam,
or about 265 nm north-northwest of Yap, and moving north-northwestward
at 11 kts. Low-level cyclonic shear was favorable, but vertical shear
was moderate and was displacing the majority of the deep convection to
the south of the center. Dvorak estimates from both SAB and JTWC reached
T2.5/2.5 on the 20th, but shortly afterward began to decline. A narrow
upper-level trough to the north of the depression appeared to be
inhibiting further intensification. Vertical shear subsequently
increased and TD-14W began to weaken, and JTWC issued their final
warning at 21/1200 UTC, locating the center 655 nm southeast of Naha,
Okinawa. JMA's final reference to the system was six hours later. The
latter agency's 10-min avg MSW estimates for this depression never
exceeded 25 kts. Tracks for TD-14W and the 9-14 September depression
were included in the companion cyclone tracks file.
The third depression of September was referenced only as a weak
tropical depression by JMA. The system was first noted at 24/1200 UTC
in the Philippine Sea near 25N/130E, moving south-southwestward slowly.
Over the next 36 hours the system drifted generally in a southwestward
direction, being last mentioned at 26/0000 UTC near 22N/127E. JTWC did
not list this disturbance as a suspect area in their STWOs, and I did
not prepare a tabular track for the system.
TROPICAL STORM DANAS
(TC-11W / STS 0710)
6 - 17 September
----------------------------------------
Danas: contributed by the Philippines, is a Tagalog word meaning "to
feel" or "to experience"
A. Synoptic History
-------------------
Prior to the development of Tropical Storm Danas on 4 September, the
monsoon trough was quiet and convection rather sparse in the Northwest
Pacific while an isolated Typhoon Fitow was travelling steadily westwards
southeast of Japan. Scattered amounts of convection were being generated
by troughing over the eastern part of Micronesia. This extended north
into the Marshall Islands to a weak circulation, located approximately
180 nm north-northwest of Wake Island. This was first alluded to in
JTWC's STWO issued at 0600 UTC 4 September when convective banding was
seen developing along the southern and eastern peripheries of the LLCC.
Even though low-level westerlies to the south and easterlies to the
north were providing favourable cyclonic wind shear, upper-level
analysis revealed unfavourable northerly shear caused by an upper-level
LOW to the north. The system slowly developed over the next two days
and a TCFA was issued at 06/2200 UTC. Animated infrared imagery
indicated a partially-exposed LLCC with the strongest convection to the
northeast. QuikScat imagery showed winds of 20-25 kts near the centre
as the disturbance drifted towards the west-northwest at 10 kts. The
first warning was issued at 07/1800 UTC, placing Tropical Depression 11W
approximately 850 nm east of Iwo Jima. JMA had first classified the
system as a tropical depression at 06/0600 UTC.
Tracking northwestward along the southern periphery of a subtropical
ridge, TD-11W slowly consolidated and was upgraded to a 35-kt tropical
storm at 1200 UTC 7 September by both JTWC and JMA. Tropical Storm Danas
continued to slowly intensify as it moved northwestward, the system's
development being hampered by dry air intrusion and the limitation of
poleward and equatorial outflow. In addition, the storm passed over
SSTs cooled by Typhoon Fitow's passage a few days earlier and also into
a region of increasing westerly wind shear. Nevertheless, Tropical Storm
Danas kept itself together and intensified a little more late on
9 September as it turned northward over the warm waters (25-26 deg C) of
the Kuroshio Current, reaching a peak intensity of 60 kts at 10/0600 UTC
at quite a high latitude (38N). (JMA's peak 10-min avg MSW for Danas
was 50 kts.) At this time, the cyclone was centred 435 nm southeast of
Misawa, Japan. The system then recurved and accelerated northeastwards
on 10 September into the mid-latitude westerlies and began extratropical
transition. JTWC issued the final warning at 11/0000 UTC, and JMA
followed suit 18 hours later.
The extratropical stage of ex-Danas lasted almost another week as it
crossed the North Pacific. The system had weakened to 35 kts as it
crossed the Dateline late on the 12th, but then began to re-intensify,
reaching 50 kts by 15/0000 UTC (based on OPC warnings). The system moved
into the Gulf of Alaska and was centered just off the southeastern coast
of Alaska later on the 15th. The LOW began slowly weakening as it
drifted eastward along the Alaskan coastline. Winds had fallen below
gale-force by 16/1200 UTC, and the system was last referenced near
Juneau, Alaska, as a 30-kt LOW at 17/0000 UTC.
B. Meteorological Observations
------------------------------
A ship located about 60 nm southeast of Danas' center at 11/1200 UTC
reported a pressure of 993.5 mb and winds 260@28 kts (10-min avg). This
was after JTWC had declared Danas extratropical, but JMA was still
carrying the system as a tropical storm. (This information sent by
Derrick Herndon.)
C. Damage and Casualties
------------------------
There were no reports of damage or casualties associated with Tropical
Storm Danas.
(Report written by Kevin Boyle)
TYPHOON NARI
(TC-12W / TY 0711 / FALCON)
11 - 18 September
-----------------------------------------------
Nari: contributed by South Korea, is the lily, a kind of plant which
grows from a bulb, with large white or coloured flowers, commonly
found in Korea in summer
A. Synoptic History
-------------------
The origins of Typhoon Nari lay within an area of convection over a
developing LLCC, noted on 10 September approximately 390 nm northwest of
Guam. It was initially mentioned in JTWC's STWO at 2230 UTC and assessed
to have a 'poor' potential for development. A 10/1214 UTC ASCAT image
indicated 10-15 kt unflagged winds associated with the weak LLCC. Upper-
level analysis indicated a low wind shear environment and good outflow,
although a weak TUTT to the north was inhibiting outflow over the north-
west quadrant. The potential was raised to 'fair' at 11/2000 UTC. JMA
first classified this system as a tropical depression at 11/1200 UTC.
Moving west-northwestwards, the system continued to develop and a TCFA
was issued at 12/1630 UTC. The first JTWC warning on Tropical
Depression 12W was issued at 12/1800 UTC, locating the centre
approximately 475 nm southeast of Naha, Okinawa. Situated southwest
of a subtropical ridge, TD-12W tracked towards the northwest at 11 kts,
and was upgraded to a 45-kt tropical storm at 13/0600 UTC.
Simultaneously, JMA raised their 10-min avg MSW to 35 kts and assigned
the name Nari. Crossing into PAGASA's AOR early on 13 September, the
storm became known in the Philippines as Tropical Storm Falcon. Only
five warnings were issued by this agency before the storm exited PAGASA's
AOR.
After reaching tropical storm intensity, Nari continued to strengthen
and became a 65-kt typhoon at 13/1800 UTC while drifting on a west-
northwesterly heading. Turning northwestward, the system intensified
rapidly on 14 September, acquiring a 14-nm diameter eye by 14/1200 UTC
while passing just west of Okinawa. Aided by a strong polar outflow
induced by an approaching mid-latitude trough, Nari reached a peak
intensity of 120 kts at 14/1800 UTC while located 80 nm west-northwest
of Naha, Okinawa. On 15 September the typhoon veered northward and began
to slowly weaken. Travelling north to north-northeast, Nari continued to
gradually wind down. The tropical cyclone passed near Cheju Do at
16/0600 UTC before coming ashore over South Korea six hours later. The
MSW was estimated at 70-75 kts at landfall. JTWC issued the final
warning at 16/1200 UTC, downgrading the system to a tropical storm. At
the same JMA lowered their MSW to 55 kts (10-min avg). Nari turned
towards the northeast late 16 September as it weakened to 35 kts
and was declared a developing LOW in JMA's final tropical cyclone
warning at 17/0000 UTC. The system became quasi-stationary in the Sea
of Japan and had weakened to a 20-kt LOW near 40N/137E by 18/1800 UTC.
At its peak Typhoon Nari was a tidy, compact system of small size
with the radius of 64-kt winds extending 20 nm around the eye. The
peak 10-min avg MSW assigned by JMA was 95 kts with an estimated
minimum CP of 940 hPa.
B. Meteorological Observations
------------------------------
The following information was sent by Derrick Herndon of CIMSS. (All
winds are 10-min avg unless otherwise stated, and the date in the
description of Nari's passage over Kumejima and Okinawa is 14 September.)
Nari passed directly over Kumejima Island. At 1500 UTC the station
reported sustained winds ENE@58 kts and a pressure of 949.6 mb, then at
1600 UTC winds SSE@48 kts and a pressure of 948.4 mb. It appears from
the radar imagery that both of these observations occurred just inside
the eyewall. Based on the observations, I would put the MSLP at about
934 mb. The core of Nari was quite small and Naha, Okinawa, only
recorded winds 150@35G68 kts at 1348 UTC with a pressure of 994 mb. The
MSLP would support 1-min avg winds of about 118 kts. The pressure
gradient between Kumejima and Okinawa would also support that value.
There is also a news report which indicated winds to about 140 mph. I
would assume this was a gust but can not confirm. Here is the quote:
"Packing the strongest winds ever recorded, Typhoon Nari pounded
Kumejima late Friday night and early Saturday before moving across
Okinawa's main island, wreaking even more havoc. Kumejima Town
registered wind speeds of 52.4 meters per second (118 mph), beginning
at 11:00 pm, then the storm buffeted the island with record-breaking
speeds of 62.8 m/s (140 mph) about 1:30 am. Landslide and flood warnings
were issued for the Kerama Archipelago after 45.5 mm (1.8") of rain fell
in an hour. Forecasters predicted 250 mm (9.8") of rain for Okinawa by
the time Typhoon Nari had passed by."
Nari then made a direct hit on Jeju Island, passing over the eastern
part of the island. Jeju airport (24 meters elevation) on the north part
of the island and NW of the center reported winds of 010@52G71 kts and a
pressure of 985 mb at 0400 UTC on the 16th. The Jeju radar site located
a little higher at 73 meters recorded winds of 340@81 kts at 0300 UTC on
the 16th. Seogwipo, located on the southern part of the island and
closer to where the center made landfall, reported winds 140@29 kts and a
pressure of 973.1 mb at 0300 UTC on the 16th. The obs put the MSLP at
0300 UTC around 968 mb. The wind at the Jeju radar site would suggest
max 1-min avg winds of about 85 kts. The MSLP would suggest something
closer to 80 kts; however, the storm's forward motion of 17 kts along
with the well-defined eyewall structure in radar could support a slight
upward bump to 85 kts.
C. Links and Comments
---------------------
Images of the Typhoon Nari, as well as a radar animation of its
passage across Okinawa, may be found at the following link:
http://cimss.ssec.wisc.edu/tropic/archive/2007/storms/12W_Nari/12W_Nari.html>
D. Damage and Casualties
------------------------
According to the online Wikipedia report, twenty people were killed or
missing in South Korea due to massive flooding. Rainfall totals reached
a record 590 mm in Jeju, South Korea.
(Report written by Kevin Boyle, with Section B contributed by Derrick
Herndon)
SUPER TYPHOON WIPHA
(TC-13W / TY 0712 / GORING)
15 � 21 September
-----------------------------------------------
Wipha: contributed by Thailand, is a woman�s name
A. Synoptic History
---------------
Super Typhoon Wipha formed in the Philippine Sea in an active
monsoon trough which extended to around 145E. It was first mentioned
in JTWC's STWO at 1730 UTC 13 September when convective banding was
forming around a consolidating LLCC located approximately 775 nm west
of Guam. Both a 13/0943 UTC QuikScat image and synoptic data indicated
strong convergent 20-25 kt westerlies south of this LLCC with 10-15 kt
easterlies to the north. Upper-level analysis revealed weak to
moderate vertical wind shear, a developing anticyclone northeast of the
centre, and favourable outflow aloft. The potential for development
was assessed as 'fair'. This was increased to 'good' at 14/2200 UTC
and a TCFA issued. The first warning on Tropical Depression 13W was
issued at 15/0600 UTC with the system tracking towards the northwest at
around 6 kts. (JMA had identified the developing LLCC as a tropical
depression six hours earlier.)
Moving more to the west, Tropical Depression 13W intensified slowly
on 15 September as a small TUTT cell to the north inhibited convection
over the LLCC and suppressed poleward outflow. The hindering effects
of this TUTT subsequently decreased, allowing more rapid
intensification. TD-13W was upgraded to a 35-kt tropical storm at 0000
UTC 16 September, and then to a 65-kt typhoon at 16/1200 UTC, at which
time it was located 320 nm south-southeast of Naha, Okinawa. JMA also
raised their 10-min avg MSW to 35 kts at 16/0000 UTC and dubbed the
tropical cyclone Wipha. (The cyclone was known locally as Goring in
the Philippines.)
Typhoon Wipha continued to strengthen on 17 September as it tracked
west-northwestward along the periphery of a subtropical ridge which was
extending across the subtropical Northwest Pacific. It became a super
typhoon at 17/1800 UTC before reaching its peak intensity of 135 kts at
18/0000 UTC. Gradual weakening began on 18 September, the storm
passing 70 nm north of Taipei, Taiwan, at 18/1200 UTC. Typhoon Wipha
made landfall over China with a MSW of 100 kts at 18/1800 UTC
approximately 50 nm south of Wenzhou. Once inland, it continued to
weaken and was downgraded to a 50-kt tropical storm on JTWC�s final
warning at 19/0600 UTC. JMA also lowered Wipha to tropical storm
status at this time. The extratropical Wipha changed to a more
northerly heading on 19 September and tracked across eastern China
before emerging into the Yellow Sea the next day. The system continued
to weaken and was only a 25-kt LOW near 39N/128E by 21/0000 UTC.
B. Meteorological Observations
------------------------------
The following information was sent by Derrick Herndon of CIMSS. (All
winds are 10-min avg unless otherwise stated.)
A number of ships were located in the northern portion of the
circulation of Wipha on the 15th and 16th. At 1800 UTC on the 15th a
ship located 130 nm NE of the center reported winds 140@36 kts and a
pressure of 999.9 mb. Another ship 105 nm NW of the center at the same
time reported winds 340@31 kts and a pressure of 996.2 mb. Neither
ship was located in the deeper convection which at the time was located
in the eastern and southern portions of the tropical cyclone. During
this time both the CIRA and CIMSS AMSU methods indicated a 1-min avg
MSW of 50-55 kts while the AODT indicated 39 kts. The Satellite
Consensus (SATCON) suggested a MSLP of 991 mb and a 1-min avg MSW of
47 kts. Given the ship observations the MSLP was at least 995 mb, which
would support a MSW of more than 35 kts. A 2100 UTC QuikScat pass
indicated several unflagged 35-kt wind vectors; however, the center of
the cyclone was near the eastern edge of the swath.
Wipha passed directly over Iriomote Island on the 18th at 0000 UTC.
The pressure at the station fell from 987 mb at 17/1600 UTC to 928 mb
at 18/0000 UTC when the winds dropped to 19 kts. The strongest sustained
winds I saw from the station were NE@72 kts at 17/2300 UTC while the
pressure was 929 mb, only 1 mb higher than the minimum one hour later.
I think the MSLP at 18/0000 UTC can pretty confidently be put at 926 mb.
Karl Hoarau provided some additional information indicating the gusts at
this station reached 128 kts. Eleven miles NE of the center and just on
the outer edge of the eyewall Ishigaki Island recorded a pressure of
953 mb with winds 070@64G88 kts. Karl indicated that this station
recorded a peak gust of 115 kts. Another station, Ohara, located south
of Iriomote and on the southern edge of the eyewall, reported winds of
SSW@76 kts at 18/0000 UTC.
Wipha passed 18 nm north of Pengjia Yu (north of Taiwan) at 0800 UTC
on the 18th when the station reported winds of 240@74 kts and a pressure
of 958.6 mb. The station was south of the eyewall at that time.
C. Links and Comments
---------------------
Radar animations of Wipha may be found at the following link:
http://cimss.ssec.wisc.edu/tropic/archive/2007/storms/13W_Wipha/13W_Wipha.html>
D. Damage and Casualties
------------------------
According to the online Wikipedia report, the total damage
attributable to Super Typhoon Wipha was estimated at over $880 million
and the overall death toll was nine. Nearly 2 million people were
evacuated from the Shanghai and Fujian-Zhejiang areas in what is
considered to be the most extensive evacuation in over a half a
century. Typhoon Wipha caused widespread severe flooding in Shanghai
where at least 80 streets were flooded. At least twenty flights were
cancelled and fifty postponed at both Shanghai airports. The storm
forced FIFA to reschedule four matches in the Women�s Soccer World Cup
hosted by China.
There was a report of a casualty in the Ryukyu Islands. The storm
left more than 7,500 travellers stranded as the two airports between
Ishigaki and Miyakojima closed down and ferries remained at port. On
Iriomote Island, some 10,600 homes were left without power, and
telephone communications cut to 1,200 homes. Half the homes were left
without electricity on Ishigaki.
(Report written by Kevin Boyle, with Section B contributed by Derrick
Herndon)
TROPICAL STORM FRANCISCO
(TC-15W / TS 0713)
23 - 26 September
--------------------------------------------
Francisco: contributed by the United States, is a Chamorro man's name
(Spanish form of Francis)
A. Track History
----------------
Tropical Storm Francisco originated as part of a large monsoon
depression and was first mentioned in JTWC's STWO at 1800 UTC
21 September, located approximately 280 nm north-northeast of Manila,
Philippines. Both multi-spectral and infrared imagery showed a
consolidating LLCC on the periphery of the monsoon depression while a
21/1553 UTC TRMM microwave pass revealed convective banding wrapping
into the LLCC from the south. The disturbance tracked slowly westwards,
crossing northern Luzon into the South China Sea on 22 September.
Strong southwesterly flow, low vertical wind shear, and good divergence
aloft all aided in development, and a TCFA was issued at 22/1500 UTC.
The first warning on Tropical Depression 15W was released at 23/0000 UTC,
the system being then located approximately 190 nm south-southeast
of Hong Kong, China. (JMA had first referenced the system as a tropical
depression at 21/1800 UTC.)
Tracking west-southwestwards, Tropical Depression 15W was upgraded to
a 35-kt tropical storm at 23/1200 UTC by both JTWC and JMA, the latter
agency assigning the name Francisco. After passing south of Hong Kong,
Francisco continued to strengthen and reached its peak intensity of
45 kts at 24/0000 UTC near the northeastern corner of Hainan. Francisco
began to weaken as it tracked across northern Hainan into a region of
unfavourable wind shear. It was downgraded to a tropical depression at
24/1800 UTC before JTWC issued its final warning at 25/0000 UTC. JMA
issued their final bulletin six hours later. The poorly-defined centre
of Francisco continued westwards across the Gulf of Tonkin on
25 September before dissipating over northern Vietnam on the 26th.
B. Meteorological Observations
------------------------------
The following information was sent by Derrick Herndon of CIMSS. (All
winds are 10-min avg unless otherwise stated.)
Dongsha Dao (WMO 59791, 20.67N/116.72E) was located 40 nm north of
the center at 1800 UTC on the 22nd when the station recorded a pressure
of 994.5 mb and winds 020@23 kts. This would put the MSLP at about
992 mb. For the landfall on Hainan, Meilan (ZKHK), located on the
northern part of the island, recorded winds of 350@31G45 kts and a
pressure of 994 mb at 0400 UTC on the 24th. The pressure continued to
fall at the station, reaching a low of 988 mb two hours later at 0600
UTC with winds of 040@23 kts. Winds continued to veer to the east over
the next few hours, suggesting the center passed south of the station.
C. Damage and Casualties
------------------------
There were no reports of damage or casualties in association with
Tropical Storm Francisco.
(Report written by Kevin Boyle, with Section B contributed by Derrick
Herndon)
TROPICAL STORM HANNA - TYPHOON LEKIMA
(TC-16W / STS 0714 / HANNA)
27 September - 4 October
---------------------------------------------------------
Lekima: contributed by Vietnam, is the name of a tree whose fruit has
only one seed surrounded by a yellow pulp which resembles an egg
yolk
A. Synoptic History
-------------------
Typhoon Lekima originated from a broad, monsoon depression in the
Philippine Sea. It was first classified as a tropical depression by JMA
at 0000 UTC 27 September. Six hours later, PAGASA initiated warnings,
assigning the name Hanna. Hanna drifted westwards and was upgraded to a
tropical storm by PAGASA at 0600 UTC 28 September. Hanna moved inland
in Luzon on the 29th and was downgraded to a tropical depression. A
QuikScat pass about six hours prior to landfall depicted some good
30-35 kt wind vectors, so it appears that PAGASA did the right thing
in upgrading Hanna to tropical storm status. By late 29 September the
centre of Hanna was located well out over the South China Sea and
drifting towards the west-southwest. (Prior to landfall in Luzon, JMA
had carried the system as a 30-kt depression on 27 and 28 September, but
downgraded it to below 30 kts at 28/0600 UTC--the same time that PAGASA
upgraded it to Tropical Storm Hanna. Prior to the system's crossing of
Luzon, JTWC issued no warnings. A TCFA was issued on the 27th, but
cancelled on the 28th. It seems that the primary reason for JTWC's
dropping the system was that it was assessed to be more of a monsoon
depression than a formative tropical cyclone.)
JTWC first mentioned Hanna as a disturbance in a TCFA at 0900 UTC
29 September. Remarks in this statement: "Recent animated multi-
spectral satellite imagery indicates a well-defined mid-level
circulation has moved over Luzon and into the South China Sea.
A 29/0117 UTC Ascat pass and recent ship observations indicate a LLCC
may be developing beneath the mid-level circulation, although this
cannot be confirmed in satellite imagery due to contamination. The
ship observations and Ascat indicate winds between 20 and 25 kts. A
200-mb anticyclone over Luzon is contributing to excellent diffluence
aloft along with dual outflow channels. Deep convection has decreased
slightly near the center of the circulation, most likely due to
interaction with land over the past six hours. Deep convective banding
is developing in the northeastern and southwestern quadrants of the
disturbance."
The JTWC's first warning on Tropical Depression 16W was issued at
30/0000 UTC with the center located approximately 460 nm east-northeast
of Nha Trang, Vietnam. However, at the same hour JMA upgraded the
depression to Tropical Storm Lekima with 10-min avg winds estimated at
35 kts. Six hours later, JTWC also upgraded Lekima to tropical storm
status while JMA raised their 10-min avg MSW estimate to 40 kts.
Tracking west-southwestward, Lekima intensified slowly over the next
two days due to the hindering effects of an upper-level LOW. This
synoptic feature suppressed deep convection over the northern
semicircle. Late on 30 September the storm entered a weak steering
flow which caused it to slow and turn abruptly more northwards.
Accelerating onto a west-northwest to northwesterly heading, Lekima
maintained a MSW of 55 kts through 1 October. The tropical cyclone
intensified early the following day and was upgraded to a 70-kt typhoon
by JTWC at 02/0600 UTC. This was to be its peak intensity. Typhoon
Lekima passed just south of Hainan Dao late on 2 October while
maintaining 70-kt winds. Tracking more westwards, Lekima then crossed
the Gulf of Tonkin on 3 October before making landfall over Vietnam at
around 03/1200 UTC with a MSW of 65 kts. The cyclone was downgraded to
a tropical storm on JTWC's last warning at 03/1800 UTC. After coming
ashore over Vietnam, JMA carried the weakening Lekima via their
bulletins for a further twelve hours. JTWC's last satellite fix on
Lekima's remnants was at 04/1800 UTC, placing the center near
16.9N/100.6E, or over north-central Thailand, headed for the northern
end of the Bay of Bengal.
Around the same time NRL opened an invest (95B) for a feature at the
head of the Bay of Bengal. This system was referenced briefly as a
depression by IMD. According to Julian Heming, the remnants of Lekima
were at least partly responsible for this depression over Bangladesh.
Julian traced back through satellite images and model analyses, and
concluded that the separate feature at the head of the Bay (Invest 95B)
was likely energized by the ex-Lekima system as it crossed Myanmar and
reached Bangladesh.
B. Meteorological Observations
------------------------------
The following information was sent by Derrick Herndon.
On October 01 at 0000 UTC a ship located 115 nm SE of the center
reported 60 kts with a pressure of 992 mb. The same ship reported
52 kts and a pressure 997 mb six hours later; however, another ship
nearby only indicated 35 kts, and that latter value is supported by
QuikScat. Therefore, the winds of 50-60 kts east and south of the
center seem too high. However, winds of this strength do seem to have
occurred south and west of the center. A ship 160 nm SW of the center
at 0600 UCT on October 01 reported winds from the west at 60 kts and a
pressure of 995 mb while another ship 180 nm west of the center
indicated winds W at 50 kts and 1003 mb. Based on these observations
and obs from Sanhu Dao (WMO 59985), the MSLP of Lekima was likely below
985 mb. Both of the ships indicating winds > 50 kts to the SW of the
center were located within the strongest gradient and near the active
convective band. At 2100 UTC on October 1 the center passed close to
Xisha Dao (WMO 59981) when the station recorded a pressure of 981.5 mb
with winds dropping to 160@8 kts. At the same time Sanhu Dao 40 nm to
the east had 982 mb, suggesting a broad center. Several hours later
at 0300 UTC on October 02 the strongest winds impacted Xisha Dao with
sustained 1-minute winds of 60 kts (station elevation is 5 meters). It
was about three hours after this that an eye feature became evident in
the microwave imagery. The eye feature was about 30 nm in diameter,
suggesting a possible tightening of the wind field during this time.
At 1400 UTC the center passed about 45 nm south of Phoenix (ZJSY) on
Hainan. The station reported a pressure of 988 mb and winds
070@33G50 kts. It appears the station was outside of the apparent
eyewall. For the landfall in Vietnam Dong Hoi (WMO 48848) was about
45 nm south of the center at 0900 UTC and reported 989 mb; however,
that was the last observation I saw from the station and CPA occurred a
few hours later.
C. Damage and Casualties
------------------------
According to the online Wikipedia report, Typhoon Lekima brought
torrential rains to Luzon which caused a landslide that killed eight
people, including three children. In addition, one person was found
dead in Quezon City. There were no further reports of casualties in the
Philippines.
Over 100,000 people were evacuated in southern China as the storm
approached, and more than 20,000 fishing boats were recalled back to
the harbors. There are no reports of casualties.
At least 42 people were reported dead or missing in Vietnam where
Lekima caused extensive damage, destroying about 100,000 houses.
(Report written by Kevin Boyle and Gary Padgett, with Section B
contributed by Derrick Herndon)
*************************************************************************
NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea
Activity for September: 1 depression **
** - no warnings issued on this system by JTWC
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. Occasionally some
information may be gleaned from the daily tropical weather outlooks
and other bulletins issued by the Indian Meteorological Department
(IMD), which is the World Meteorological Organization's Regional
Specialised Meteorological Centre (RSMC) for the basin.
The reported maximum sustained winds (MSW) are based on a 1-minute
averaging period, which is used by all U. S. civilian and military
weather services for tropical cyclone warnings. For synoptic
observations in the North Indian Ocean region, both 10-minute and
3-minute average winds are employed, but IMD makes no attempt to
modify the Dvorak scale for estimating tropical cyclone intensity;
hence, a 1-minute average MSW is implied. In the North Indian Ocean
basin JTWC usually does not initiate warnings until a system has
become well-organized and likely to attain tropical storm status
within 48 hours.
North Indian Ocean Tropical Activity for September
--------------------------------------------------
A disturbance in the Bay of Bengal in late September was designated
a depression by the IMD, but no warnings were issued on the system by
JTWC. An area of convection persisted on 21 September approximately
180 nm east of Visakhapatnam, India. Multi-spectral satellite imagery
revealed a broad area of turning with monsoon depression characteristics.
A 21/1512 UTC AMSU pass showed a developing LLCC in the western portion
of the larger area. Convective banding was wrapping into the center
from the northern and western quadrants. An upper-level anticyclone
was near the developing disturbance, and with low to moderate vertical
shear and good diffluence aloft, JTWC assessed the development potential
as 'fair'. The IMD classified the system as a depression (implying winds
around 25 kts), and by the morning of the 22nd it lay centered about
25 nm southeast of Puri at 0600 UTC. By 0900 UTC the depression was
crossing the coastline near Puri with the potential for heavy rainfalls
of up to 250 mm forecast for some locations. Early on the 23rd the
system was located over interior Orissa near Angul and gradually
weakening. Twenty-four hours later the system was still moving
northwestward and farther inland over north Chhattisgarh near Ambikapur.
Some notable 24-hour rainfall amounts are as follows:
(1) 24 hours ending at 23/0300 UTC:
-----------------------------------
Canning 160 mm
Balasore 140 mm
Kolkata 130 mm
Cuttack 100 mm
(2) 24 hours ending at 24/0300 UTC:
-----------------------------------
Canning 190 mm
Sambalpur 180 mm
Kolkata 160 mm
Hirakud 150 mm
Ranch 100 mm
During the final days of September another tropical disturbance formed
in the eastern Arabian Sea off the west coast of India. This system was
not classified as a depression by IMD, but based on SAB satellite fix
bulletins, could have possibly been a weak depression. The system formed
just off the northwest coastline of India and eventually moved northward
over the Kathiawar Peninsula. On 23 and 24 September, SAB's Dvorak
ratings reached T2.0/2.0 for the system, which was identified on NRL's
website as Invest 94A.
*************************************************************************
SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E
Activity for September: No tropical cyclones
*************************************************************************
NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E
Activity for September: No tropical cyclones
*************************************************************************
NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E
Activity for September: No tropical cyclones
*************************************************************************
SOUTH PACIFIC (SPA) - South Pacific Ocean East of Longitude 160E
Activity for September: 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: summ0709.htm
Updated: 13th February 2008 |
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