[Index]
Monthly Global Tropical Cyclone Summary October 2000
[Summaries and Track Data] [Prepared by Gary Padgett]
| Tropical
Cyclones
[Index] |
Monthly Global Tropical Cyclone Summary October 2000 [Summaries and Track Data] [Prepared by Gary Padgett] |
MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
OCTOBER, 2000
(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.)
***********************************************************************
OCTOBER HIGHLIGHTS
--> Western Atlantic subtropics very active
--> Significant typhoon rakes Philippines and Taiwan
--> First North Indian Ocean cyclones of year develop
***********************************************************************
***** Feature of the Month for October *****
ATLANTIC SUBTROPICAL SYSTEMS OF 2000
(Part 1)
------------------------------------
This is Part 1 of a three-part feature detailing cyclonic systems
of 2000 in the Atlantic which were either subtropical storms or
depressions or else exhibited some of the features of subtropical
cyclones. A few months back I asked David Roth if he would consider
putting together such an article and he agreed to do so. David is
a native of south Florida, a graduate of Florida State University, and
is currently employed as a meteorologist at the Hydrometeorological
Prediction Center in Maryland. David has a special interest in hybrid
and subtropical cyclones and has been spending a lot of time the past
few months poring over old weather maps and articles searching for
"subs" for possible inclusion in the Atlantic "best track" database
when the on-going re-analysis of the database reaches the latter part
of the 20th century.
Some explanations and a few words of caution are in order first,
however. There is no generally agreed-upon, widely accepted, specific
definition of exactly what constitutes a subtropical cyclone. The
definition of a subtropical cyclone in TPC/NHC's on-line glossary
reads: "a low-pressure system that develops over subtropical waters
that initially has a non-tropical circulation but in which some
elements of tropical cyclone cloud structure are present." The issue
of non-frontality is not addressed in that definition, but seems to be
a sort of "acid test" which is usually applied by NHC before officially
recognizing the existence of a subtropical cyclone (especially storm).
As I've already written in the discussion of Tropical Storm Leslie
below, NHC is extremely conservative about using the subtropical
classification operationally, and only a little less so in admitting
subtropical storms into the "best track" file after the fact.
On the other hand, David seems to employ a fairly liberal definition
of a subtropical cyclone, so there are some differences between David's
listing of subtropical systems and the ones that NHC has officially
recognized as subtropical depressions or storms for at least a portion
of their tracks. In this part I am going to include David's table of
subtropical systems with appropriate comments as to how NHC has
classified some of the systems in question. Also, I have included
David's write-ups for two October systems below in the section covering
Atlantic basin activity. Part 2 (November summary) will discuss the
named tropical cyclones which in David's opinion exhibited subtropical
cyclone characteristics for a portion of their lives--an opinion not
necessarily shared in every case by the NHC specialists. Part 3
(December summary) will include David's write-ups for the remaining
subtropical cyclones of 2000.
The introduction David wrote to his article follows:
The subtropical cyclone production in the Atlantic Basin this year
has been exceptional. Eleven cyclones have entered the subtropical
stage, nearly triple the long-term average of 3.7 per year. This is
up sharply from 1999, when only five developed, and makes it the most
productive year in the Atlantic since 1984 (when there were 9), and the
most active of the past 50 years. Persistent blockiness in the
Atlantic and eastern North America led to a high number of cutoff LOWS,
which in many cases ultimately became subtropical. Three formed from
tropical cyclones when either cool, dry air entered near the surface,
or they became coupled with upper-tropospheric LOWS. Two contained
hurricane force winds while still subtropical (Florence and Gordon).
Three of these systems made landfall in the United States: subtropical
cyclones III, VI (Gordon), and IX (Leslie). The table below lists
their duration (and designations) while subtropical. Roman numerals
were chosen similarly to the older, monthly cyclone discussions
published in _Monthly Weather Review_ from the 1870s into the 1950s.
(Numbers in parentheses following the storm designation refer to
explanatory notes below.)
I. Subtropical Depression May 19-25
II. Alberto (1) August 14-16
III. Subtropical Storm (2) August 28-30
IV. Subtropical Depression September 10-11
V. Florence (3) September 10-12
VI. Gordon (1) September 17-18
VII. Helene (1) September 24-25
VIII. Subtropical Storm (2) September 30-October 3
IX. Leslie (3) October 4-8
X. Michael (3) October 14-17
XI. Subtropical Storm (4) October 25-28
(1) The official NHC "best tracks" do not treat any portion of Alberto,
Gordon, or Helene as subtropical. In general, once a tropical
cyclone has been named, NHC treats it as a tropical system through-
out the remainder of its life--both operationally and in post-
analysis--even if at some point it exhibited some subtropical
features.
(2) According to Jack Beven, these two systems possibly could qualify
as subtropical storms pending a careful analysis of all the
available data. For the time being they should be regarded as
possible subtropical storms.
(3) Subtropical portions of the tracks of Florence, Leslie, and Michael
are designated in the "best tracks" for these cyclones. The dates
of their subtropical phases, however, might not necessarily agree
with those David has assigned above.
(4) This storm has already been officially recognized as a subtropical
storm by TPC/NHC.
***********************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for October: 2 tropical storms
1 hurricane
1 subtropical storm
1 hybrid (possibly subtropical) storm
NOTE: Much of the information presented below was obtained from the
TPC/NHC discussion bulletins issued with every regular advisory. All
references to sustained winds imply a 1-min averaging period unless
otherwise noted.
Atlantic Tropical Activity for October
--------------------------------------
An active October followed on the heels of a very active September
in the Atlantic basin. Three of the September tropical cyclones were
still active as the month opened: Hurricane Isaac was beginning to
transition into a vigorous extratropical cyclone in the North Atlantic,
former Hurricane Joyce was rapidly weakening as it moved through the
Windward Islands into the southeastern Caribbean Sea (where it
dissipated on 2 October), and major Hurricane Keith was reaching its
peak intensity in the northwestern Caribbean just off the southern
Yucatan Peninsula. Keith subsequently stalled just offshore of
northern Belize, weakened into a tropical storm and made landfall
in Belize, later emerging into the Bay of Campeche and regaining
hurricane intensity before making a final landfall in Mexico north of
Tampico on 5 October. See the September summary for the full reports
on these tropical cyclones.
The western Atlantic subtropics became a beehive of storm activity
during October. A gale center developed off the southeastern U. S.
coast during the opening days of the month and exhibited some features
of a subtropical cyclone. (Further discussion of this system can be
found below.) Also during the first week of the month, a system from
the Caribbean which dumped very heavy rainfall on portions of southern
Florida developed into a subtropical depression and eventually into
Tropical Storm Leslie just off the east coast of Florida. Around
mid-month another non-tropical LOW developed into a subtropical storm
and underwent a classic transformation into a warm-cored cyclone and
became Hurricane Michael. About ten days after Michael's development,
another subtropical storm developed just north of the Bahamas and made
a valiant attempt to become what would have been Tropical Storm Oscar,
but was unable to sustain persistent convection near the center. (A
write-up of this storm can be found below.)
Finally, as Hurricane Michael was racing toward Newfoundland, a
tropical wave interacted with an upper-level trough southeast of
Bermuda to produce the season's final tropical cyclone: Tropical
Storm Nadine. Nadine became a 50-kt tropical storm as it headed
northeastward into the central Atlantic ahead of a cold front.
The official TPC/NHC tropical cyclone reports prepared by the
Hurricane Specialists are now available for all of the 2000 Atlantic
basin tropical cyclones. The reports are very interesting and
informative, and links to them can be found at the following URL:
http://www.nhc.noaa.gov/2000.html> . Since I am running so far
behind schedule, and since I think it highly likely that just about
every person who reads these summaries has access to the internet, I
am going to trim down the amount of material I write about the
remaining Atlantic cyclones--primarily including a few items of
interest which are not mentioned in the official NHC reports.
The short summaries of the two subtropical systems following the
write-up of Tropical Storm Nadine were written by David Roth. A
special thanks to David for all the material he prepared on the
hybrid/subtropical systems.
Tropical Storm Leslie (TC-16)
4 - 10 October
------------------------------
Tropical Storm Leslie was a weak storm of subtropical origin which
formed just east of the northeastern Florida coast and moved unevent-
fully northeastward across the Atlantic. Before being classified as
a tropical cyclone public advisories were issued on the system as
Subtropical Depression One. The official storm report on Leslie,
prepared by James Franklin and Daniel Brown, can be found at the
following URL: http://www.nhc.noaa.gov/2000leslie.html>. I
recommend that interested readers first connect to TPC/NHC's website
and read James' and Daniel's report, which contains a tabular listing
and plot of the analyzed "best track" as well as plots of
meteorological information.
One unusual facet of this tropical cyclone was the enormous damage
caused by heavy rains in southern Florida during the pre-depression
stage. A weak mid-level circulation associated with a tropical wave
moved northwestward out of the Caribbean Sea and interacted with a
stalled frontal boundary. Very heavy rains fell over portions of
Miami-Dade and Broward counties. Several locations had 48-hour storm
totals exceeding 380 mm and one spot in South Miami logged 445 mm.
Three deaths were indirectly attributed to the flooding, and the
estimated total damage figure was around $700 million of which $500
million were agricultural losses. It should be emphasized that the
rainfall which led to the flooding occurred before a well-defined
surface circulation had formed. No deaths or damage were caused by
the system after it had become Subtropical Depression One and Tropical
Storm Leslie.
The designation of the LOW on 4 October as a subtropical depression
marks the first time that public subtropical depression or subtropical
storm advisories have been issued by TPC/NHC since a subtropical storm
in April, 1992. However, several systems during the intervening years
have been classified as subtropical cyclones for at least a portion of
their tracks during post-storm analysis. In the spectrum of cyclone
classifications the boundary between extratropical and subtropical
cyclones is very broad and diffuse, and TPC/NHC prefers to be very
conservative with the use of the subtropical cyclone classification.
Many cyclones are "hybrids", i.e., they exhibit features of both
tropical and extratropical cyclones, but not all hybrids are considered
to be subtropical cyclones. TPC/NHC does not like to operationally
classify a system as subtropical--unless there is a very special reason
for doing so--in the interest of avoiding potential confusion among the
public and media. As for admitting subtropical storms into the "best
track" file after-the-fact (e.g., June, 1997, and October, 2000) the
NHC specialists like to carefully study the available data to insure
that a system was absolutely non-frontal--something which is often
difficult to accomplish in real-time.
The primary difference between the "best track" and the operational
track for Leslie is one of intensity. Operationally, Leslie's MSW
was never reported any higher than 35 kts, and the storm was downgraded
to a tropical depression at 06/1800 UTC. However, based on a more
thorough analysis of the available data, the "best track" shows the MSW
reaching 40 kts at 06/0600 UTC and remaining at this value until
extratropical transition at 1800 UTC on 7 October. After losing its
tropical characteristics the extratropical system moved rapidly across
the North Atlantic as a fairly weak gale until 10 October when it began
to intensify once more. The "best track" indicates that the cyclone
reached southwestern Ireland as a 60-kt storm around 10/1800 UTC.
It is perhaps arguable as to whether Leslie ever really was a
tropical cyclone. The system at best had only nominal tropical
characteristics--the deep convection never really moved over the center
and the strongest winds were located farther out from the center than
is typical of most tropical cyclones. James Franklin's comments in the
discussion bulletin at 1500 UTC on 5 October (when Leslie was named as
a tropical storm) are very interesting and give insight regarding the
issues which the forecaster is often confronted with: "Reconnaissance
observations this morning show that the wind field of the subtropical
depression has been contracting, with peak flight-level winds of 44 kts
reported within 75 nm of the center; whereas yesterday they were about
twice as far out, and there has also been more consistent convection
in the vicinity of the circulation. While this is by no means a
classic tropical cyclone, it has enough tropical characteristics, and
wind, to be considered a tropical storm. It is worth remembering that
nature produces a whole spectrum of different kinds of cyclones, and
that they do not always neatly fit into the small number of classi-
fications that we have available for use in our advisories."
Hurricane Michael (TC-17)
14 - 22 October
--------------------------
Hurricane Michael formed off the coast of northeastern Florida
from a subtropical storm and eventually raced northeastward and
briefly became a Category 2 hurricane on the Saffir/Simpson scale
before merging with a cold front just south of Newfoundland. The
official storm report on Michael, prepared by Stacy Stewart, can be
found at the following URL: http://www.nhc.noaa.gov/2000michael.html>.
I recommend that interested readers first connect to TPC/NHC's website
and read Stacy's report, which contains a tabular listing and plot of
the analyzed "best track" as well as plots of meteorological
information.
Michael's origins can be traced to an upper-level cold LOW which
dropped southward and interacted with a stationary frontal boundary
over the southeastern Bahamas. The LOW gradually acquired subtropical
characteristics and became a subtropical depression at 1200 UTC on
15 October. The "best track" indicates that the depression had
developed gale-force winds by 16/0000 UTC and hence had become a
subtropical storm. Convection gradually increased around the center
and the transition to a tropical storm is estimated to have occurred
by 17/0000 UTC. However, the system was not operationally classified
as a subtropical depression or storm; instead, it was treated as a
non-tropical LOW and gale warnings were included in the High Seas
Bulletins. The first advisory on Tropical Depression 17 was issued
at 17/0000 UTC and the system was upgraded to Tropical Storm Michael
six hours later.
Both the operational track and analyzed "best track" agree, however,
that Michael reached hurricane intensity at 1800 UTC on the 17th, and
the two are in close agreement from that point forward with regard to
intensity. The storm had intensified to 75 kts by 1800 UTC on the
18th, but then weakened to 65 kts at 19/0600 UTC. As Michael raced
toward Newfoundland a ship in the eastern eyewall reported sustained
winds of 80 kts and a SLP of 965.5 mb, so the MSW was upped to 85 kts,
making Michael a Category 2 hurricane. The highest flight-level wind
measured by any US-based reconnaissance flight was 95 kts from a height
of 450 m at 1755 UTC on 18 October. (A Canadian reconnaissance flight
a few hours prior to landfall on the 19th measured a wind of 136 kts
near the top of the boundary layer, but the cool (4 C to 10 C) and
very stable air would likely have prevented those winds from reaching
the surface.)
Michael reached its peak intensity as it neared Newfoundland, but
just a few hours before reaching the coast the storm merged with a
cold front so technically was not a tropical cyclone as it made
landfall. However, the storm still carried winds exceeding hurricane
force. Sagona Island along Newfoundland's south coast measured winds
to 69 kts with a peak gust of 93 kts and a pressure of 967.7 mb.
Most of the island experienced winds of 50 kts and pressures around
975 mb as the storm roared across. Newfoundland, however, frequently
experiences winds of that magnitude in association with North Atlantic
extratropical cyclones and damage was reportedly light across the
island.
Tropical Storm Nadine (TC-18)
19 - 23 October
------------------------------
The final tropical cyclone of the 2000 Atlantic hurricane season
formed over the open Atlantic southeast of Bermuda and moved rather
uneventfully northeastward, becoming extratropical after a couple
of days. The official storm report on Tropical Storm Nadine,
prepared by Lixion Avila, can be found at the following URL:
http://www.nhc.noaa.gov/2000nadine.html>. I recommend that
interested readers first connect to TPC/NHC's website and read
Lixion's report, which contains a tabular listing and plot of the
analyzed "best track" as well as plots of meteorological information.
As Lixion's report points out, the formation of Nadine was triggered
by the interaction of a tropical wave and an upper-level trough. The
tropical wave instrumental in the development of Nadine seems to have
been a wave first noted in the far eastern Atlantic around 5 October.
The wave made its way slowly across the tropical Atlantic, battling
shear and never showing any really serious signs of developing in the
deep tropics. Around mid-month it encountered the upper-level trough,
but several days were still required for the development of a surface
depression. Another system worth mentioning was a tropical wave to
the west of the precursor of Nadine. On 6 October a very well-defined
and tightly-wound low-level circulation center became visible in
association with this wave about 700 nm west of the Cape Verde Islands.
It was undergoing shear and there was very little convection near the
LLCC; hence, it was not classified as a tropical depression, but it
was nonetheless somewhat impressive looking in visible imagery.
Since Tropical Storm Nadine was a rather short-lived, uneventful
storm, and since the official storm report covers it rather well, there
isn't much else to write. The operational MSW estimates and the "best
track" MSW values are in perfect agreement for the tropical storm phase
of Nadine's life. At one point, when an eye-like feature became
apparent in infrared and microwave imagery, there was an outside chance
that Nadine might reach minimal hurricane intensity. This didn't
happen, but if it had, the three-year period 1998-2000 would have had
a total of 27 hurricanes--a new three-year record for hurricanes in the
Atlantic basin. As it was, the 26 hurricanes observed over the three
seasons tied the previous three-year record set in 1949-1951.
Possible Subtropical Storm
30 September - 3 October
--------------------------
As Joyce was recurving across the central Atlantic, and the major
Hurricane Keith was approaching Belize, a closed 500-mb LOW (with -9 C
air at that level) developed off the southeastern U. S. coast.
Thunderstorm activity increased tremendously in this region, and a
subtropical cyclone had developed over 31 C waters. A non-frontal LOW,
with a large dry slot, the system moved up the Gulf Stream, reaching
subtropical storm proportions overnight on the 30th/1st. The system
became well removed from its thunderstorm activity on the 2nd while
located between North Carolina and Bermuda. By the 3rd, the system
had developed a definite frontal structure, instantly occluding off
Nova Scotia. Based on ship reports, the peak winds during the possible
subtropical phase of this system are estimated at 40 kts.
NOTE: Jack Beven has indicated that all the available data for this
system will be reviewed to see if it qualifies for inclusion in the
"best track" database as a subtropical storm.
Subtropical Storm
25 - 28 October
-----------------
The final subtropical storm of the year formed from the end of an
old frontal boundary north of the Greater Antilles. It retrograded
westward to a position just northeast of the Bahamas and closed off a
low-level circulation. Convection was plentiful with the system, and
fronts became non-existent on the 25th. Right when it closed off, it
instantly became a subtropical storm as winds of 35 kt were already
present according to ship reports in its vicinity. The storm moved
northward, with a definite dry slot around its western side for the
next couple of days. It strengthened to a 55-kt cyclone early on the
28th as it was accelerating northeastward ahead of a cold front
approaching the center of the circulation. It quickly became frontal
by that evening, bombing to a 978-mb cyclone and occluding during its
extratropical stage.
NOTE: This storm has been officially classified as a subtropical
storm and entered into the Atlantic "best track" database. A report
on this system, authored by Jack Beven, is available at the following
URL: http://www.nhc.noaa.gov/2000subtropical.html> .
***********************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for October: 2 tropical storms
NOTE: Much of the information presented below was obtained from the
TPC/NHC discussion bulletins issued with every regular advisory (CPHC
for locations west of 140W.) All references to sustained winds imply
a 1-min averaging period unless otherwise noted.
Northeast Pacific Tropical Activity for October
-----------------------------------------------
The Northeast Pacific basin on the average sees two tropical storms
develop during the month of October with one reaching hurricane force.
This year there were two named storms in October but neither became
a hurricane. Tropical Storm Olivia formed early in the month south of
Manzanillo, Mexico, and moved slowly generally in a westward to west-
northwestward direction for about a week, reaching a peak intensity of
55 kts twice. Late in the month, minimal Tropical Storm Paul formed
far to the south of Baja California and followed a westward track for
four days at an unusually low latitude: the complete track remaining
south of 12N.
The write-ups for Tropical Storms Olivia and Paul were written by
John Wallace of San Antonio, Texas. A special thanks to John for
writing the summaries of these two cyclones.
Tropical Storm Olivia (TC-17E)
2 - 10 October
-------------------------------
Olivia was one of the few NEP storms of 2000 whose formation was
not tied to any tropical wave. Intermittent, strong convection off
the west coast of Central America flared up strongly on 29 September
and had consolidated into a tropical LOW by the 30th. The LOW
organized steadily as it tracked westward; its cloud signature
improved enough to warrant its upgrade to Tropical Depression
Seventeen-E at 1500 UTC on 2 October, a move that was supported by
ship reports. The depression's center at this time was located
roughly 250 nm south-southeast of Manzanillo, Mexico. The small
tropical cyclone tracked slowly west-northwestward in the easterly
flow south of a mid-level ridge in a largely favorable synoptic
environment.
The depression intensified steadily despite some shear, and its
organization improved enough to warrant its upgrade to Tropical Storm
Olivia at 0900 UTC on 3 October, albeit with some reluctance based on
limited data. Even with the moderate shear, Olivia intensified
quickly and reached its peak estimated MSW of 55 kts and CP of 994 mb
at 2100 UTC on the 3rd, a mere 12 hours after its upgrade. An SSM/I
overpass indicated the formation of a partial eyewall, an event which
was supported by satellite imagery suggesting an incipient eye.
Intensification to hurricane intensity was forecast. This did not
materialize, however, and Olivia leveled off at its peak intensity for
about two days. Olivia remained quasi-stationary for around 12-18
hours on the 4th about 225 nm south-southwest of Manzanillo while it
was at its peak intensity. Persistent, stiff easterly shear finally
took its toll on the 5th when a weakening trend began as the storm
turned to the west-southwest. By 0900 UTC on the 6th, Olivia had
weakened to minimal tropical storm strength with slow dissipation
forecast.
Tropical cyclones are nothing if not capricious, however, and Olivia
was no exception. Beginning at 1500 UTC on the 6th, there was a second
intensification trend as Olivia turned again to the west-northwest.
Satellite and model data suggested that Olivia's second wind, so to
speak, was due to weakened wind shear. Re-intensification was slow and
uneven though, as convection redeveloped over the center only to weaken
or get sheared off repeatedly. Conflicting satellite data added to
the forecasters' problems. Nevertheless, Olivia re-attained its peak
intensity of 55 kts and a 994 mb CP for a second time at 2100 UTC on
7 October when it was centered approximately 400 nm south-southwest of
Cabo San Lucas on the tip of the Baja California peninsula. It was an
ephemeral achievement; another weakening trend began immediately after
its second peak. Shear increased, and there were the first indications
of stable air entrainment. The storm's track turned slightly more to
the northwest as it reached the periphery of the ridge to its north.
Olivia weakened steadily through the 8th, and had dropped below
tropical storm strength by 0900 UTC on the 9th as it entered cooler
waters. A possible threat to the Baja peninsula was forecast as a
trough approached, but Olivia was not expected to survive long enough
to fulfill it. Such was the case, and the last advisory was issued on
the convection-free whorl at 0900 UTC on the 10th placing the
dissipating cyclone about 500 nm west-southwest of Cabo San Lucas.
A notable characteristic of Tropical Storm Olivia was its small
size. The radii of gale-force winds never exceeded 75 nm, and
throughout most of the storm's life they ranged from 50-60 nm. This
is a size range similar to that of 1999's Tropical Storm Emily in the
Atlantic.
There were no known casualties associated with Olivia. The very
weak remnant LOW eventually moved northeastward across the Baja
peninsula and portions of the American Southwest. Some localities
received up to 75 mm of rain which resulted in isolated flash flooding.
The official storm report on Tropical Storm Olivia, prepared by
Stacy Stewart, is available on TPC/NHC's website at the following
URL: http://www.nhc.noaa.gov/2000olivia.html> . One item in
Stacy's report which differs from John's account above concerns the
origin of Olivia. According to the NHC report, Olivia's development
was associated with a wave which left the coast of western Africa on
16 September. After entering the Eastern Pacific the wave was
hampered somewhat by major Hurricane Keith to its north and likely
was difficult to follow for a few days until Keith had weakened and
its influence declined. One minor difference was noted between the
operational warnings and "best track": operationally Olivia was
upgraded to a tropical storm at 03/0600 UTC--in post-analysis it was
determined that the system had reached tropical storm intensity six
hours earlier.
Tropical Storm Paul (TC-18E)
25 - 29 October
-----------------------------
Like Olivia before it, the formation of Tropical Storm Paul did not
appear to be related to a tropical wave. A disturbance in the ITCZ
west of Central America consolidated into a tropical LOW on 21 October.
The LOW tracked steadily westward at a low latitude for several days
until its organization was sufficient to warrant its upgrade to
Tropical Depression Eighteen-E at 2100 UTC on 25 October when it was
approximately 750 nm south of Cabo San Lucas. It is worth noting that
the first advisory indicated the disturbance might have been a tropical
storm the night prior to its upgrade before shear took its toll; a
QuickScat pass at 1300 UTC on the 25th indicated 35-40 kt winds. The
primary steering factor for the depression was a low- to mid-level
ridge to the north which kept the system on a general westward track
throughout its lifetime.
Stiff north to northwesterly shear initially hindered the
depression. Even so, its organization increased enough overnight to
justify its upgrade to Tropical Storm Paul at 1500 UTC on 26 October
when it was located about 800 nm south-southwest of Cabo San Lucas.
Continued shear made life difficult for Paul as it tracked westward and
the cyclone never intensified beyond minimal tropical storm strength.
Paul maintained a 35-kt MSW for less than two days; the lowest CP of
1003 mb was reached at 0300 UTC on 27 October and was maintained for
12 hours. The storm took a brief west-northwest jog on the 27th as a
shortwave trough passed to the north, then turned back to the west
as the ridge to its north strengthened again. Throughout its life
as a tropical storm Paul remained in a sheared state; contrary to
forecasts, upper-level westerlies did not decrease over the system.
Paul weakened to a depression at 0900 UTC on the 28th. The tropical
cyclone quickly disintegrated, and at 0300 UTC on 29 October the last
advisory was issued on the poorly-defined system located roughly
1300 nm southwest of Cabo San Lucas.
There were no known casualties or other damage associated with Paul.
The official storm report on Tropical Storm Paul, prepared by
Miles Lawrance, is available on TPC/NHC's website at the following
URL: http://www.nhc.noaa.gov/2000paul.html> . There were two minor
differences noted between the operational warnings and "best track".
Advisories were begun on TD-18E at 25/1800 UTC--the "best track" begins
the depression stage twelve hours earlier at 0600 UTC. Also, the
highest MSW given in any advisory was 35 kts, but the "best track"
assigns a peak MSW of 40 kts at 26/1800 UTC.
***********************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for October: 2 tropical storms **
2 typhoons
** - one of these was treated as a tropical storm only by JTWC, and
another is included based upon Mark Lander's assessment that it
reached tropical storm intensity
NOTE: Most of the information on each cyclone's history presented in
the narrative will be based upon JTWC's advisories, and references to
winds should be understood as a 1-min avg MSW unless otherwise noted.
However, in the accompanying tracking document I have made comparisons
of coordinates with JMA (Japan) and the Philippines (PAGASA) when their
positions differed from JTWC's by usually 40-50 nm or more. A special
thanks to Michael V. Padua, owner of the Typhoon 2000 website, for
sending me the PAGASA and JMA tracks.
In the title line for each storm I plan to reference 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 responsibility.
Northwest Pacific Tropical Activity for October
-----------------------------------------------
In marked contrast to August and September, the Northwest Pacific
basin was much quieter in October, at least until the closing days of
the month when two typhoons formed. Typhoon Yagi threatened Taiwan
but ran into an unfavorable environment and dissipated between Taiwan
and Okinawa. (Note: JMA did not classify Yagi as a typhoon, but PAGASA
did upgrade the storm to typhoon status.) Whereas Yagi formed as a
small, TUTT cell-induced system in the northern edge of the tropics,
Typhoon Xangsane formed as a monsoon depression very deep in the
tropics east of Mindanao. Xangsane crossed Luzon and later brushed
Taiwan and was responsible for several fatalities and significant
damage in both countries.
In addition to the named cyclones there were two other systems which
are discussed below. Tropical Storm 28W was a weak tropical cyclone
which roamed the western South China Sea for over a week early in the
month. JMA classified this system as a tropical depression only, but
synoptic observations in the 35-40 kt range seem to support JTWC's
decision to upgrade the system to a tropical storm. Also, I have
included some information supplied by Mark Lander on another very
small TUTT cell-induced LOW which he considers to have been an unnamed,
unnumbered tropical storm. I have dubbed this cyclone with the Greek
letter "Xi" for identification purposes.
Finally, another tropical depression (31W) formed on the final day
of October east of Mindanao almost exactly where Typhoon Xangsane had
taken shape a few days earlier. This system developed into Typhoon
Bebinca and followed a track across the central Philippines almost
identical to that taken by the earlier storm. Bebinca will be covered
in the November summary.
Tropical Storm (TC-28W)
6 - 14 October
------------------------
Tropical Storm 28W was a relatively weak system which roamed the
western South China Sea for a week in early October. JTWC classified
the system as a tropical storm on 8 and 9 October and again very
briefly before it dissipated on the 13th, but JMA treated the LOW as
a tropical depression throughout its lifetime: hence, no name was
assigned. The cyclone also remained to the west of PAGASA's AOR so
never received a name from that agency. A persistent although
disorganized area of convection was located in the Sulu Sea early on
4 October. Vertical shear was weak and the area was located beneath
a ridge axis. As the day progressed convection developed farther to
the west--to the southwest of Palawan Island--with improving
organization. A LLCC was evident and JTWC assigned a Fair development
potential rating to the disturbance.
By early on 6 October the broad, poorly-defined LLCC was located
about 200 nm off the Vietnamese coast and, with moderate upper-level
easterlies over the area, appeared to be weakening, so the development
potential was downgraded to Poor. However, as the day progressed
animated satellite imagery indicated an increase in convective
organization and a ship in the area reported an observation of 30-kt
winds, so at 1800 UTC JTWC initiated warnings on TD-28W, located about
100 nm east-northeast of Cam Ranh Bay, Vietnam. The MSW was estimated
at 30 kts, and the depression was initially forecast to move westward
and inland without further strengthening. Visible pictures on the 7th,
however, revealed that the depression's center was farther east than
previously analyzed, resulting in a relocation of about 65 nm to the
east of the previous warning position.
The depression subsequently drifted slowly in a general eastward
direction, gradually curving to the north on the 8th. As early as
0600 UTC on the 7th some satellite intensity estimates were reaching
35 kts and by 08/0600 UTC had reached 45 kts. This, in conjunction
with a land observation of 35-kt winds (WMO 59995), led to JTWC's
upgrading the depression to a tropical storm at 0600 UTC. The cyclone
was still experiencing moderate easterly vertical shear, resulting in
a fully-exposed LLCC with deep convection sheared around 40 nm to the
west. (JMA had classified the system as a tropical depression at
1800 UTC on the 7th but never upgraded it to a tropical storm.) The
weak storm drifted slowly northward on the 8th, then began to turn
to the northwest on the 9th as a low- to mid-level ridge began to
build to the northeast. The MSW was increased to the peak value of
40 kts at 08/1800 UTC based upon satellite intensity estimates of
35 and 45 kts. An increase in convection had occurred near the
LLCC during the night.
The peak intensity of 40 kts was maintained for about 30 hours.
Moderate shear remained over the cyclone as it moved slowly northward
and northwestward, and the center was partially-exposed. A synoptic
ship report of 40-kt winds was received sometime before 09/0600 UTC,
confirming the MSW estimate. By 1800 UTC on 9 October the center of
the weak tropical storm was located about 215 nm east-southeast of
Da Nang, Vietman, and moving northwestward at 6 kts. Satellite current
intensity estimates were still ranging from 35 to 55 kts, but the
center had become exposed with the LLCC displaced about 75 nm to the
east of the deep convection. The majority of the convection associated
with the system had moved over the Vietnamese coast. A ship located
approximately 50 nm west-southwest of the center reported 35-kt winds
(10-min avg) from the west-northwest with an attendant SLP of 999.5 mb.
Again, on the 10th, the first visible pictures resulted in a relocation
of the center. The 10/0000 UTC position was about 90 nm southwest of
the previous warning position, and the storm was downgraded to a
tropical depression.
TD-28W was forecast to move inland and dissipate, but instead the
system began to track northeastward under the steering influence of
monsoon trough winds to its south. Over the next couple of days the
weak depression drifted slowly generally in a northeastward direction,
remaining a fully-exposed LLCC with little to no associated deep
convection. This made the center very difficult to follow in night-
time infrared imagery, and the track appears somewhat erratic. The
estimated MSW, which had been decreased to 25 kts at 1200 UTC on
10 October, was bumped up slightly to 30 kts at 12/0000 UTC as micro-
wave imagery revealed two cells of deep convection forming near the
center. Dvorak intensity estimates began to slowly increase on the
12th--by 1200 UTC a new area of convection had developed over the
estimated position of the LLCC.
The depression was once more upgraded to a tropical storm at 0000
UTC on 13 October when the location of the center was estimated to be
about 245 nm east-northeast of Da Nang. The exact location of the
LLCC, however, was difficult to pinpoint. Convection covered the
entire northern South China Sea and there was some evidence of multiple
circulation centers. Satellite intensity estimates were 35 kts, and
a strong band of convection had begun to organize to the north and
east of the estimated center. The rejuvenated tropical storm had
also turned toward the northwest and was forecast to make landfall
along the east coast of Hainan Island. However, six hours later
animated satellite imagery showed a decrease in the intensity of
the convection and the LLCC was difficult to locate. JTWC once more
downgraded the cyclone to a depression at 13/0600 UTC and issued
the final warning, placing the dissipating center about 175 nm east-
northeast of Da Nang. A secondary LLCC with some weak convection was
noted about 150 nm to the south of the primary center but no further
development was noted with this system.
Tropical Cyclone "Xi"
15 - 19 October
---------------------
The material presented on this system was gleaned from information
sent to the author by Dr. Mark Lander of the University of Guam and
from some STWO's issued by JTWC. The track prepared by Mark locates
a small, weak circulation center about 475 nm east-southeast of Iwo
Jima at 0000 UTC on 15 October. Over the next couple of days the
system moved generally west-northwestward, passing approximately 50 nm
south of Iwo Jima around 1200 UTC on the 16th. The area was first
mentioned by JTWC in a STWO issued at 16/0600 UTC and was described as
a fully-exposed LLCC with convection sheared southwest of the center
and embedded in an inverted trough. Mark's track depicts the LOW
reaching its point of recurvature about 50 nm west-northwest of Iwo
Jima around 17/0000 UTC and thereafter turning to the north and later
to the east. Mark's MSW estimate at this point is 30 kts, but the
17/0600 UTC STWO from JTWC indicates that the system had disspated.
In Mark's opinion the system reached tropical storm intensity around
1200 UTC on the 17th at a point about 100 nm north-northwest of Iwo
Jima and reached its peak intensity of 40 kts twelve hours later when
it was centered 200 nm north of the island. That the system appeared
better developed is evidenced by the issuance of a Formation Alert by
JTWC at 18/0200 UTC. The remarks indicated that a 17/2030 UTC Quik-
Scat pass showed 15-20 kt winds and troughing in the area, but also
noted that the circulation might be too small for the satellite to
resolve. The areal extent of the system was only about 100 nm and it
was located on the end of a shear line. The small cyclone moved off
to the east and had weakened to a depression (per Mark's track) by
1800 UTC on the 18th. JTWC cancelled the Formation Alert at 1400 UTC
and reported that the system had begun to move rapidly eastward and was
weakening under increasing vertical shear as it neared a cold front
moving off Japan. By 19/0000 UTC the LOW had apparently been absorbed
into the front about 300 nm northeast of Iwo Jima.
Mark Lander elaborated a bit on the subject of these small, TUTT
cell-induced tropical cyclones in the subtropics when he sent me the
track. I thought that his remarks might be of interest to some readers
so I am including them here verbatim:
"I think these small tropical cyclones that develop in the subtropics
in association with TUTT cells are important because of their very
delimited and easily followed genesis that is clearly related to the
forcing of the upper-level vortex on the distribution of convection,
stability and wind shear. These types of small TCs tend to form in the
northeast quadrant of the TUTT cell in pre-existing low-level easterly
flow, unlike the majority of WESTPAC TCs that form in the monsoon
trough.
"The subject tropical storm formed only a few days before the next
TUTT cell to move west across the WESTPAC basin produced another TC
that became Typhoon Yagi. Images of Yagi forming in its TUTT cell
environment look identical to images of the subject unnamed, unnumbered
tropical storm at the same point of development in its TUTT cell
environment.
"TUTT cell-induced TC genesis in the subtropics of the WESTPAC basin
is the closest thing that we have to what might be considered a 'wave
in the easterlies.' As the incipient TC develops from its parent
MCS, there is a brief stage where an inverted trough appears in the
easterly flow.
"Another rule of thumb that has emerged from a study of these small
TUTT cell-induced TCs: they tend to peak after recurvature. Some of
the more intense ones (like Yagi, which followed this guy by only a
few days, and Jelawat in early August) keep moving westward and peak
at typhoon (intensity) before recurvature.
"A more thorough examination of a satellite picture archive like that
of Jeff Hawkins at NRL Monterey might yield a more accurate best
track, so my purpose here is simply to point out the existence of an
unnumbered, unnamed tropical storm, and those really interested in
following up, or doing more research, on it can use my best track as
a reference for a more in-depth search." (Quote from personal e-mail
received from Mark Lander.)
Typhoon Yagi (TC-29W / STS 0019 / Paring)
21 - 28 October
------------------------------------------
Yagi: contributed by Japan, is the Japanese word for goat
Typhoon Yagi was a compact typhoon which formed in the upper tropics
about 200 nm southwest of Iwo Jima and traveled westward for several
days in the general direction of northern Taiwan. As Yagi approached
Taiwan it intensified rather quickly into a fairly intense typhoon
(based upon JTWC warnings) and was forecast to strike the island, but
it ran into an environment of vertical wind shear and drier air and
began to steadily weaken. The storm eventually made a clockwise loop
east of northern Taiwan as it dissipated. It should be pointed out
that JMA never upgraded Yagi to a typhoon. At the warning time when
JTWC's estimated MSW reached its peak value of 105 kts (24/1800 UTC),
JMA's maximum 10-min avg wind estimate was only 55 kts. JMA did
increase the 10-min avg wind to 60 kts at 25/0000 and 25/0600 UTC.
However, PAGASA (which called the storm Paring) did upgrade Yagi to a
65-kt typhoon (10-min avg) at 24/0600 UTC and maintained that intensity
until the storm moved out of their AOR after 25/0000 UTC.
Yagi's beginnings can be traced to an area of convection which had
developed by early on 20 October about 400 nm north-northeast of Guam.
A partially-exposed weak LLCC could be seen in animated satellite
imagery with persistent, isolated convection north of the center. The
disturbance was embedded within an inverted trough with convergent flow
displaced north and east of the center; vertical shear was light to
moderate. The development potential was upgraded to Fair later in the
day as convection increased in areal extent. A Formation Alert was
issued at 0800 UTC on the 21st when the LLCC was centered approximately
325 nm south-southeast of Iwo Jima. The system had been moving rather
rapidly westward under the steering influence of the subtropical ridge
to the north. The initial warning on TD-29W was issued at 1800 UTC on
21 October and placed the center about 225 nm south-southwest of Iwo
Jima or approximately 740 nm east-southeast of Okinawa. (JMA had
classified the system as a tropical depression beginning at 0000 UTC.)
TD-29W was moving rather quickly west-northwestward at 17 kts and was
already near tropical storm intensity.
JTWC upgraded the depression to a tropical storm on the second
warning (22/0000 UTC) when satellite intensity estimates had reached
35 kts, and JMA did so six hours later, naming the system Yagi. Based
upon JTWC warnings Yagi remained a minimal tropical storm for 24 hours
after being upgraded as it sailed rather quickly toward the west. (JMA
increased the maximum 10-min avg wind estimate to 40 kts at 1200 UTC.)
The 1200 UTC warning from JTWC, while indicating that convection had
consolidated around a small LLCC, also noted that a recent QuikScat
pass had not been able to resolve a circulation center beneath the
convection. JTWC increased the MSW to 45 kts at 23/0000 UTC with the
small cyclone centered about 360 nm southeast of Naha, Okinawa. Yagi's
forward motion had slowed to 9 kts by 1200 UTC and the MSW was upped
to 60 kts at 1800 UTC. Satellite intensity estimates were 45 and 55
kts, but infrared imagery showed possible eye development. A 23/1228
UTC SSM/I pass depicted tightly curved convective bands with the
deepest convection north of the system's center.
JTWC upgraded Yagi to a typhoon at 0000 UTC on 24 October when the
storm was located just under 200 nm south of Okinawa. Animated water
vapor imagery indicated that a new outflow channel had formed on the
north side of the system, thus supporting the increase in intensity.
(PAGASA upgraded Yagi/Paring to a 65-kt typhoon at 0600 UTC but the
storm was not considered a typhoon by JMA.) The storm continued to
rapidly intensify and reached its peak estimated MSW (per JTWC's
warnings) of 105 kts at 1800 UTC when it was centered approximately
215 nm east-southeast of Taipei and 20 nm south of Miyako Island.)
The warning intensity was based upon satellite intensity estimates of
102 and 115 kts. Miyako Island (WMO 47927) reported sustained 28-kt
winds, so Yagi was characterized by a very tight wind field. Satellite
imagery revealed a 20-nm cloud-filled eye with the radius of 50-kt
winds estimated to be only 25 nm. Gales covered an area less than
150 nm in diameter.
Interestingly, before reaching its peak intensity, Yagi had been
forecast to make landfall in Taiwan. But by the time the storm peaked,
landfall was no longer forecast and the typhoon was expected to
encounter vertical shear and begin to weaken quickly after about 24 to
36 hours. At 25/0000 UTC Miyako Island reported 10-min avg sustained
winds of 59 kts with gusts to 78 kts. Some shearing was already
beginning to affect Yagi and convection was weakening. The MSW
was lowered to 90 kts at 0600 UTC with the cyclone moving north-
northwestward at only 4 kts from a position 140 nm east of Taipei.
The forecast weakening trend continued: by 0000 UTC on 26 October
Yagi's winds were down to 75 kts, and JTWC downgraded the cyclone to
a tropical storm at 1200 UTC. At 26/0000 UTC Yagi was located about
140 nm west of Okinawa and was tracking slowly eastward. The storm
was located beneath 30-40 kt upper southwesterlies and cold, dry air
was being entrained into the system. The strong shear began to
decouple the convection from the LLCC, and the 1200 UTC warning noted
that the convection appeared to be rotating anti-cyclonically if at
all. Radar imagery also indicated a band of strong convection moving
eastward without any rotation evident.
The weakening Yagi approached to within about 40 nm of Naha before
turning back to the west-southwest. At 27/0000 UTC the MSW was
estimated at 45 kts by JTWC, but JMA downgraded Yagi to a dissipating
depression and issued their last tropical cyclone bulletin on the
system. Convection was sheared about 185 nm to the northeast of the
LLCC. A building ridge over the East China Sea forced the sheared
cyclone to the south and then back to the west as it dissipated,
describing a clockwise loop in the process. JTWC downgraded Yagi to
a tropical depression at 1200 UTC on the 27th when the LLCC was located
about 125 nm southwest of Okinawa. At 28/0000 UTC a ship located about
55 nm south-southwest of the depression's center reported north-
northwest winds of 26 kts. By this time there was no significant
convection associated with the system. The final warning on Yagi was
issued at 28/0600 UTC and placed the center with only 20-kt winds
about 90 nm east of Taipei, Taiwan. Animation of visible satellite
imagery revealed a vast stratocumulus deck with a convection-free,
fully-exposed low-level circulation center. The author has received
no reports of any casualties or damage associated with Typhoon Yagi.
Typhoon Xangsane (TC-30W / TY 0020 / Reming)
25 October - 2 November
---------------------------------------------
Xangsane: contributed by Lao People's Democratic Republic (Laos), is
the Laotian word for elephant
In contrast to Typhoon Yagi, which was a small, TUTT cell-induced
system forming in the upper tropics, Typhoon Xangsane developed in
the monsoon trough very deep in the tropics east of the southern
Philippines. Although the storm developed into a typhoon of only
moderate intensity (90 kts), it left a trail of death and destruction
in the Philippines and Taiwan. An area of convection had developed
by early on 24 October almost 300 nm southeast of Yap. A sudden burst
of convection had appeared in satellite imagery and synoptic data
indicated a weak LLCC embedded in the monsoon trough extending eastward
from Mindanao. The disturbance moved westward with slowly increasing
organization and pressure falls of 2 to 4 mb in the area. JTWC issued
a Formation Alert at 0500 UTC on the 25th when the center was located
about 75 nm south of Yap. Deep convection had begun to develop near
the LLCC and the development potential was rated as Good. PAGASA
classified the LOW as a tropical depression at 0200 UTC and initiated
warnings, naming the depression Reming.
JTWC issued the first warning on TD-30W at 25/1200 UTC with the
center estimated to be about 140 nm northeast of Palau. The system
was moving on a west-northwestward course from which it never
significantly deviated until after it had crossed Luzon and recurved
sharply to the north-northeast in the South China Sea. Deep convection
continued to develop near 30W/Reming's center but organization of the
convection proceeded somewhat slowly. PAGASA upgraded Reming to a
40-kt tropical storm at 0000 UTC on 26 October when the system was
centered approximately 175 nm northwest of Palau. Both JTWC and JMA
upgraded the system to a tropical storm at 0600 UTC with JMA assigning
the name Xangsane (the second "elephant" of the year: the name of the
first typhoon back in May--Damrey--is the Cambodian word for elephant).
Tropical Storm Xangsane steadily intensified as it marched toward the
central Philippines. Vertical shear was weak and the convection became
increasingly intense and organized around the circulation center.
MSW estimates had reached 55 kts from both JTWC and PAGASA by 1800 UTC,
and JTWC upgraded Xangsane to a typhoon at 27/0000 UTC with the center
located about 200 nm northeast of Surigao (on the extreme northern tip
of Mindanao). PAGASA's 10-min avg wind estimate was 60 kts, but JMA's
was somewhat lower at 50 kts.
Xangsane/Reming continued to increase in intensity until it made
landfall in extreme southeastern Luzon shortly before 1800 UTC. JTWC
estimated the MSW at 75 kts (based on satellite intensity estimates
of 65 and 77 kts), but PAGASA's and JMA's maximum 10-min avg wind
estimates were 60 kts, just shy of typhoon intensity. The center of
the cyclone passed just south of Catanduanes Island, up the Lagonoy
Gulf and into southeastern Luzon. At 1800 UTC the center of Xangsane/
Reming was located approximately 135 nm east of Manila. This location
is only 25 nm (45 km) northeast of Naga City where one of my "helpers",
Michael Padua, lives. Although convection had continued to organize
around the center, it weakened in the bands northwest of the eye as
they rotated over Luzon. A SSM/I pass at 27/1310 UTC revealed a 30-nm
round eye with excellent banding features. Also, animated water vapor
imagery depicted good outflow above the storm.
Michael Padua sent me a log of his personal observations as Reming
passed over Naga City (which was in the eye of the typhoon). The
maximum sustained wind Mike recorded was a north-northeast wind of
43 kts (80 kph) at 3:00 and 3:30 AM local time. This was before the
eye reached Naga City around 4:00 AM when the winds began to diminish
rapidly. The peak gust of 53 kts (98 kph) was recorded at 1:00 AM,
although a nearby PAGASA station recorded a gust of 59 kts (108 kph)
at 6:00 AM, after the eye had passed by. The minimum pressure recorded
by Mike in the eye was 977 mb at 4:30 AM. Mike's complete Observations
Log can be found at the following URL:
http://www.geocities.com/taifun00/xangsane_obs.htm>
By clicking on the "Show Graph" button one can view a very nice and
informative graphical representation of the time histories of the
pressure, sustained wind, and peak gusts which Mike recorded on his
instruments. By using colored bars for pressure and two different
colored lines for the two windspeed parameters, Mike has created a
very impressive-looking and easy-to-read chart of his observations.
Typhoon Xangsane/Reming crossed the southern portion of Luzon,
passing about 80 km south of Manila around 0600 UTC on 28 October.
The 28/0000 UTC observation from WMO 98440 indicated 40-kt sustained
winds (10-min avg) and a SLP of 990.4 mb. The MSW had decreased
to 55 kts by the time the center emerged into the South China Sea
(around 1800 UTC). While the storm was still over Luzon, at 0600 UTC,
a ship 75 nm to the northwest of the center reported sustained north-
erly winds of 45 kts. Deep convection persisted near the center while
the storm was over land. By 1800 UTC the center of Xangsane was over
the South China Sea about 85 nm northwest of Manila and moving north-
westward at 10 kts. The storm became quasi-stationary on the 29th
about 200 nm northwest of Manila. The MSW remained at 55 kts but
around 29/1200 UTC the convection had weakened due to some erosion
by dry air in the western semicircle. However, by 1800 UTC the storm
had re-intensified with a developing banding eye apparent, so Xangsane
was upgraded once more to typhoon status with 65-kt winds. (JMA's
maximum 10-min avg wind was 60 kts at this juncture, but both JMA and
PAGASA upgraded the storm to a typhoon at 30/0000 UTC.) A TRMM pass
at 29/1517 UTC depicted improving organization with a solid ring of
eyewall convection.
Xangsane reached its peak intensity of 90 kts (per JTWC) at 0000 UTC
on 30 October. The storm was still quasi-stationary about 200 nm from
Manila or about 360 nm south-southwest of the southern tip of Taiwan.
(JMA's maximum 10-min avg wind for the storm's history was 75 kts from
30/0600 to 31/1200 UTC.) A ragged eye 28-nm in diameter was visible,
and the typhoon exhibited excellent outflow in all quadrants.
Convection over the northeastern quadrant more or less disappeared due
to interaction with the west coast of Luzon, but a fulldisk infrared
image showed a large feeder band extending from Malaysia into the
center of Xangsane. By 1800 UTC on the 30th the storm was located
approximately 65 nm west of Laoag on northwestern Luzon and was moving
north-northeastward at 8 kts. An approaching upper-level trough caused
the typhoon to accelerate toward the north-northeast and also increased
the shear over the storm. At 31/1200 UTC the 30-nm diameter eye was
centered about 65 nm south of the southern tip of Taiwan and was moving
north-northeastward at 13 kts. By 1800 UTC on the 31st Xangsane was
brushing the southeastern coast of Taiwan and had accelerated to
19 kts. The MSW had dropped to 80 kts (70 kts from JMA) and the
typhoon was beginning to slowly transition into an extratropical storm.
Typhoon Xangsane continued to slowly weaken and lose its tropical
characteristics as it sped north-northeastward just off the east coast
of Taiwan. The storm passed about 65 nm east of Taipei around 0000
UTC on 1 November and by 0600 UTC was only a minimal 65-kt typhoon
located about 100 nm northeast of the city. (JMA at this point down-
graded Xangsane to a 50-kt tropical storm.) JTWC downgraded the system
to a tropical storm at 01/1200 UTC and issued their final warning at
1800 UTC. Xangsane was located about 100 nm southwest of the Japanese
island of Kyushu (or about 375 nm east of Shanghai, China) and was
racing northeastward at 37 kts. The rapidly weakening convection was
being sheared northeast of the center and satellite imagery indicated
significant entrainment of cooler, drier air with an extensive strato-
cumulus field from southwest to northwest of the system. The by-now
extratropical gale continued to move northeastward across southwestern
Japan. The final position available to the author (from JMA's High
Seas Bulletins) placed the LOW in the vicinity of Osaka at 0600 UTC
on 2 November.
A press report indicated that Typhoon Xangsane/Reming left at least
26 dead in the Philippines with 50 additional persons missing at the
time of the report, most of these fishermen missing at sea. The storm
caused 30,000 families to have to evacuate their homes and 100,000
persons were left homeless. Hundreds of homes were damaged due to
flooding in Manila and nearby provinces. Total damage to property and
crops was placed at 1.4 billion pesos, or $27.45 million. The Filipino
Department of Agriculture reported that 275,672 hectares of rice
paddies were flooded, resulting in an estimated loss of 112,211 tons
of unmilled rice.
In Taiwan Xangsane was reportedly the most destructive typhoon to
strike the island since Typhoon Herb in 1996. The death toll reached
at least 59 with 30 persons missing. In the northern port city of
Keelung, 21 persons were drowned after being caught in buildings that
flooded rapidly. Heavy rains triggered landslides near Taiwan, and
schools and government offices in several cities and counties closed
due to the storm. Flooding was reported to be the worst on Taiwan in
30 years. The Council of Agriculture estimated initial agricultural
losses at $62.5 million.
There was also an air disaster which was indirectly due to the
typhoon. A Boeing 747 owned by Singapore Airlines crashed on takeoff
from Taipei's Chang Kai Shek International Airport on 31 October with
the loss of 82 lives out of the 179 on board. At the time of the
crash Typhoon Xangsane was near the southern tip of the island and
moving quickly north-northeastward. Winds at the airport were 37 kts
from the north-northeast gusting to 56 kts, and visibility was 400 m in
heavy rain. A subsequent investigation of the accident revealed that
the flight crew mistakenly attempted takeoff on the wrong runway, one
which was closed for repairs. The airplane struck some of the
construction equipment while traveling at 140 kts, breaking the
fuselage into three parts and igniting a large post-crash fire. More
details on the accident can be found at the following website:
http://www.airdisaster.com>
***********************************************************************
NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea
Activity for October: 2 tropical cyclones of gale intensity
NOTE: The tracking and intensity information for North Indian Ocean
Basin tropical cyclones is based primarily upon operational warnings
from the Joint Typhoon Warning Center of the U. S. Air Force and Navy
(JTWC) 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
WMO's RSMC for the basin.
The MSW are based on a 1-min 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 region,
both 10-min and 3-min average winds are employed, but IMD makes no
attempt to modify the Dvorak scale for estimating tropical cyclone
intensity; hence, a 1-min avg MSW is implied. In the North Indian
basin JTWC usually does not initiate warnings until a system is
well-organized and likely to attain tropical storm status within
48 hours.
Tropical Cyclone (TC-01B)
15 - 18 October
--------------------------
On 12 October an area of convection developed in the east-central
Bay of Bengal roughly 500 nm south-southeast of Calcutta. Synoptic
data and microwave imagery indicated a possible LLCC associated with
the convection. By the 14th the disturbance had moved farther to the
west and lay over the central Bay. Satellite imagery revealed a fully-
exposed LLCC with persistent deep convection about 75 nm west-northwest
of the center. The MSW was estimated at 25 kts--a tropical depression
by NWP basin warning criteria. The Indian Meteorological Department
(IMD) did classify the developing system as a depression at 0600 UTC on
15 October when it was centered approximately 350 nm east-southeast of
Visakhapatnam, India. Also, at 15/0600 UTC JTWC issued a Formation
Alert for the disturbance. A 15/0117 UTC TRMM pass depicted improved
curvature and developing convective bands northwest of the LLCC. Water
vapor imagery also revealed good outflow over the system. By 1800 UTC
IMD had increased the intensity estimate to 30 kts--a deep depression
by their terminology. The depression had continued to move westward
and the center was located approximately 225 nm southeast of the city
of Visakhapatnam.
JTWC issued the first warning on TC-01B at 0000 UTC on 16 October.
The initial MSW was 35 kts and the center was located about 320 nm
east-southeast of Vijayavada, India, moving westward at 8 kts. The
current satellite intensity estimate was 30 kts, but QuikScat data
indicated that winds of 35 kts were occurring, primarily in the north-
western quadrant. The center was partially-exposed with the deep
convection situated to the west of the vortex. The cyclone was in
an environment of light to moderate vertical shear. The system's
forward progress had slowed to 3 kts by 1200 UTC and the center was
fully-exposed with the deep convection sheared about 50 nm west of
the LLCC.
The minimal tropical storm continued to move slowly in a general
westerly direction toward southeastern India on 17 and 18 October but
never made landfall. JTWC temporarily downgraded the system to a 30-kt
depression at 17/1200 UTC but IMD continued to refer to it as a
cyclonic storm in their bulletins. Satellite imagery revealed a
fully-exposed circulation with convection sheared 85 nm to the west
of the LLCC. By 18/0000 UTC, though, satellite intensity estimates
had jumped a little as the center had moved near the edge of the
convection, so JTWC re-upgraded TC-01B to a minimal tropical storm
located about 160 nm east-southeast of Masulipatnam, India. However,
twelve hours later the convection had weakened and moved well to the
west of the LLCC, which had become difficult to locate. JTWC down-
graded the cyclone once more to a depression and issued their last
warning, placing the center with 25-kt winds about 115 nm east-
southeast of Masulipatnam. (IMD, however, was still carrying the
system as a cyclonic storm at 1800 UTC but had downgraded it to a
low-pressure area by the following day.)
There were no reported human fatalities in India from this weak
tropical cyclone, but a press report indicated that gale-force winds
in the Srikakulam district killed at least 100 pelican chicks by
blowing them out of their nests.
Tropical Cyclone (TC-02B)
26 - 28 October
--------------------------
The second North Indian Ocean tropical cyclone of the month (and
also of the year) had its roots in an area of convection which
developed about 200 nm west-northwest of the Andaman Islands late on
24 October. Synoptic data indicated the presence of a weak cyclonic
circulation with good outflow aloft. JTWC upgraded the development
potential of the disturbance to Fair at 1800 UTC on the 25th. IMD
classified the system as a depression with 25-kt winds at 0600 UTC
on 26 October when it was located about 500 nm south-southeast of
Calcutta. By 1800 UTC the disturbance had moved farther west into
the central Bay of Bengal. Convection was intense at times but did
not sustain itself. JTWC estimated the winds at 20-30 kts and issued
a Formation Alert.
By 1200 UTC on 27 October the depression had moved northward toward
the head of the Bay. Since the system was moving into a region of
increased shear, and also since the majority of the associated deep
convection lay over land, JTWC cancelled the Formation Alert at 1500
UTC. A 27/1454 UTC SSM/I pass indicated a convective band east of the
system wrapping into the LLCC. The STWO issued by JTWC at 1800 UTC
estimated the MSW at 25-30 kts (a tropical depression by NWP warning
criteria) and downgraded the development potential to Fair. However,
shortly thereafter the first warning was issued on TC-02B based upon
satellite intensity estimates of 35 and 55 kts. Animated satellite
imagery depicted increased organization with the convective band noted
above wrapping into the LLCC. Convection was also re-developing over
the center and increasing in areal extent. The cyclone was centered
about 125 nm south-southwest of Calcutta and moving northward at 6 kts.
The MSW was estimated at 35 kts. IMD also upgraded the system to a
cyclonic storm, thereby implying winds of at least gale force.
The center of TC-02B crossed the northeastern coast of India about
85 km southeast of Calcutta at approximately 27/2300 UTC. By 0600 UTC
on the 28th the storm was a weakening depression centered about 65 km
southwest of Dhaka, Bangladesh, tracking northeastward at 15 kts.
Strong upper-level southwesterlies had pushed the convection to the
northern Bangladesh border.
There were media reports of casualties associated with this tropical
cyclone in Bangladesh. At least 30 persons were reported dead and
200 fishermen were missing. Winds reportedly reached 55 kts (likely
in gusts, although this is not certain) and caused damage to homes,
crops, trees and electrical lines.
***********************************************************************
SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E
Activity for October: No tropical cyclones
***********************************************************************
NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E
Activity for October: No tropical cyclones
***********************************************************************
NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E
Activity for October: 1 non-tropical (possibly hybrid) LOW
Northeast Australia/Coral Sea Tropical Activity for October
-----------------------------------------------------------
A small LOW developed just south of Mackay on the tropical east
coast of Queensland around 0000 UTC on 30 October. The system formed
east of a mid- to upper-level trough which was pivoting from a north-
west/southeast tilt to a southwest/northeast tilt over eastern
Australia. Strong warm-air advection was occurring through deep
layers between Rockhampton and Brisbane east of this trough on the
30th and heavy rain began falling over the region. The LOW rapidly
intensified and produced gale- to storm-force winds along and off the
south Queensland coast during 31 October as a tight pressure gradient
developed between the LOW and a HIGH over the Tasman Sea to the south.
The LOW developed over SSTs between 23 and 24 degrees Celsius. On
the 31st the LOW began to move southeastward away from Australia and
had moved across 160E into the Wellington AOR by 0600 UTC on the 1st
of November. (This LOW was not a tropical cyclone, but appeared to
have some hybrid or subtropical features.)
Many locations between Brisbane and Mackay registered rainfall
totals in excess of 100 mm for the 24 hours ending at 30/2300 UTC with
a couple of stations reporting more than 200 mm. However, a long-
running drought had preceded this event and the run-off from the heavy
rains was not excessive enough to produce any significant stream
flooding. Several coastal stations reported sustained winds to gale
force with gusts exceeding 50 kts, including Rundle Island AWS (41 kts
gusting to 51 kts between 30/1232 and 1250 UTC), Lady Elliot Island
(37 kts gusting to 50 kts between 30/0722 and 0845 UTC), and Double
Island Point AWS (43 kts gusting to 50 kts around 31/0338 UTC). The
highest winds were experienced at the Cape Moreton AWS where the
maximum 10-min avg wind reported was 45 kts and the peak gust was
55 kts. This station reported gales from 0200 UTC on the 30th through
1202 UTC on the 31st.
The wind brought down trees and power lines with power blackouts
in Brisbane suburbs and on the Sunshine Coast just north of Brisbane.
The wind and rain led to some traffic accidents, one causing two deaths
and another resulting in a serious injury. On the Sunshine and Gold
Coasts marine craft broke their moorings and were set adrift. There
was also serious beach erosion noted at Maroochydore and Noosa on the
Sunshine Coast.
(The information presented above was sent to me by Jeff Callaghan
of the Brisbane TCWC. A special thanks to Jeff for sending me the
report.)
***********************************************************************
SOUTH PACIFIC (SPA) - South Pacific Ocean East of Longitude 160E
Activity for October: No tropical cyclones
***********************************************************************
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 July, 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
in the following manner:
(a) FTP to: hrd-type42.nhc.noaa.gov [140.90.176.206]
(b) Login as: anonymous
(c) For a password use your e-mail address
(d) Go to "data" subdirectory (Type: cd data)
(e) Set file type to ASCII (Type: ascii)
(f) Transfer file (Type: get remote_file_name local_file_name )
(The files will be named with an obvious nomenclature--using
October as an example: oct00.tracks)
(g) To exit FTP, type: quit
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. If anyone wishes to retrieve any of the previous summaries,
they may be downloaded from the aforementioned FTP site at HRD. The
summary files are catalogued with the nomenclature: oct00.sum, for
example.
Back issues can also be obtained from the following websites
(courtesy of Michael Bath, Michael V. Padua, Tom Berg, Michael
Pitt, and Rich Henning):
http://australiasevereweather.com/cyclones/>
http://www.typhoon2000.com> OR http://www.geocities.com/taifun00/>
http://www.hurricanealley.net/>
http://www.qisfl.net/home/hurricanemike>
http://www.met.fsu.edu/gsc/Docs/Grads/henning/cyclones/>
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.met-office.gov.uk/sec2/sec2cyclone/sec2cyclone.html>
TROPICAL CYCLONE REPORTS AVAILABLE
I have discovered that JTWC now has available on its website the
complete Annual Tropical Cyclone Report (ATCR) for 1999 (1998-1999
season for the Southern Hemisphere). Also, ATCRs for earlier years
are available also.
The URL is: http://199.10.200.33/jtwc.html>
Also, TPC/NHC has available on its webpage nice "technicolor"
tracking charts for the 1999 Atlantic and Eastern North Pacific
tropical cyclones; also, preliminary storm reports for all the 1999
Atlantic and Eastern North Pacific cyclones are now available. In
addition storm reports are now available for the Atlantic and Eastern
Pacific tropical cyclones in 2000.
The URL is: http://www.nhc.noaa.gov>
Prepared by: Gary Padgett
E-mail: [email protected]
Phone: 334-222-5327 (nights & weekends) / 850-882-2594 (weekdays)
***********************************************************************
***********************************************************************
|
Document: summ0010.htm
Updated: 29th December 2006 |
[Australian Severe Weather index] [Copyright Notice] [Email Contacts] [Search This Site] |