[Index]
Monthly Global Tropical Cyclone Summary October 2001
[Summaries and Track Data] [Prepared by Gary Padgett]
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Monthly Global Tropical Cyclone Summary October 2001 [Summaries and Track Data] [Prepared by Gary Padgett] |
MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
OCTOBER, 2001
(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
--> Atlantic active with devastating Central American hurricane
--> Both North Pacific basins also active with one super typhoon
--> First Southern Hemisphere cyclone of the 2001-2002 season forms
***********************************************************************
***** Feature of the Month for October *****
AN UNREPORTED SOUTHWEST INDIAN OCEAN CYCLONE
--------------------------------------------
Last year on 30 August I received a copy of an e-mail from Roger
Edson to Philippe Caroff at the La Reunion TCWC. The message contained
a letter sent to Roger by Tony Cristaldi, a forecaster and tropical
cyclone enthusiast at the NWS office in Melbourne, Florida. A few days
earlier Tony had been downloading some additional images of the by now
rather well-known midget cyclone which formed in the Mozambique Channel
last June and was at its peak intensity on 21 June when the moon's
shadow also crossed the Channel in the first total solar eclipse of
the new millennium. Tony indicated that he had pulled off about two
days worth of POES passes on the days leading up to 21 June so that he
could examine the structure of the cyclone during its formative stages.
To quote Tony's e-mail: "I came upon a problem--the system I was
looking at was NOT where it should have been. The times and positions
didn't match some data that I had already downloaded from the AFWIN and
NRL Monterrey sites. Instead, the cyclone remained SOUTH of the
Channel and NEVER got all that close to Mozambique. After scratching
my head for a few minutes, I took a second look at one of the images
in the HRPT reader. Lo and behold! I had typed in a FOUR instead of
a SIX for the month when I pulled the data from SAA! I was looking at
data from APRIL 19-21!!"
Tony further relates that upon discovering there was a midget
cyclone on the exact same days two months earlier, he dug up my global
summary for April, 2001, to read about it. But nothing was there, nor
in the monthly cyclone tracks file, since I knew nothing about the
cyclone's existence. Philippe's reply to Roger at least cleared up
the mystery surrounding the cyclone, i.e., why no warnings were issued.
Philippe indicates that he was certainly aware of the storm, but no
warnings were issued because it formed outside of La Reunion's area of
warning responsibility, the boundary being latitude 30 south. Reunion
did issue warnings on Tropical Cyclone Dera in March, 2001, until it
began extratropical transition near 35S, but this was considered sort
of "extra work". Philippe related that personally he would like to
see their AOR extended farther south, perhaps to 40S, and planned to
bring this matter up at an upcoming regional meeting.
Philippe's letter states that both the April and June cyclones were
similar in that both formed in baroclinic environments. The June
midget formed from a wave along a cold front which became cut-off and
migrated northward, whereas the precursor of the April cyclone exited
alone from southeastern Africa. Philippe indicates that he did not
check the SSTs in April around 33S to 34S, but thinks it likely they
were similar to the SSTs over which the June cyclone formed--around
24-25C. Both systems displayed some very similar cloud patterns when
mature, but the April system was much longer-lived, remaining at a
significant intensity for about four days, plus displaying some very
significant diurnal fluctuations.
A few weeks later Tony sent me a CD containing many satellite images
of both the April and June cyclones, plus a track for the April system,
both tabular and plotted. In the meantime I had informed Dr. Karl
Hoarau of Cergy-Pontoise University near Paris about the storm, so
Karl set about the task of downloading satellite imagery covering the
storm's history and deriving intensity estimates for the cyclone. The
track and intensities, based upon Tony's and Karl's inputs, follow
the narrative. Karl indicates that his 1-min avg MSW estimates repre-
sent values less than the normal Dvorak numbers would yield in order to
take into account the fact that the storm was not tropical all of the
time, the rapid changes seen in the convection, and the high latitude
of the track.
The storm formed about 140 nm southeast of Durban, South Africa.
At 1200 UTC on 17 April a ship located near 29.2S, 35.0E reported a
northerly sustained wind of 20 kts. At the same time Durban (29.9S,
30.8E) recorded a south-southwesterly wind of 15 kts. Convection began
to build during the morning of 18 April and a warm, elongated eye-like
feature had formed by 1740 UTC. However, convection was not all that
deep--east of the "eye" the cloud top temperatures were in the range
of -7 to -20 C. On the 17th, while still basically extratropical,
the system had moved slowly eastward, dropping a little to the south-
east. The center apparently made a small loop early on the 18th before
moving a little more quickly south-southeastward for several hours.
After around 1700 UTC the storm embarked on a very slow eastward track
until early on the 19th. Karl estimates that the cyclone reached its
peak intensity of 55-60 kts (1-min avg) around 1700 UTC on the 19th.
The Objective Dvorak T-number was 4.2 and the subjective T-number was
4.0. The CDO-feature appeared somewhat eroded but the "eye" was
faintly visible.
The storm jogged southward early on the 19th before resuming its
slow east-southeastward motion several hundred miles south-southwest
of southern Madagascar. The convection became ragged and appeared to
be northerly sheared early on 20 April but made a comeback later in
the day. Around 1200 UTC on 21 April the cyclone presented its
most "tropical" appearance so far in its history. (This being
Tony's assessment of the system's character). A large eye-feature was
evident, open to the south and southeast. The CDO extended well to the
south, then southeastward in a reverse comma shape. On the 21st the
storm took a jog to the north, then northwest, and later westward,
completing a loop which resembles a figure "8" lying on its side.
Karl's intensity log, which had decreased the MSW to 40 kts on the
evening of the 20th, shows an increase back to 45 kts on the morning
of the 21st to reflect this increased organization. (Karl, however,
prefers to classify the system as extratropical even though there was
an increase in convection.)
This increase in convection was temporary. By 22/0000 UTC the cold
cloud tops had warmed to the point that the cyclone was devoid of deep
convection and was only a low-level swirl. The storm was still moving
west-southwestward early on the 22nd, but during the day recurved to
the south-southeast and accelerated significantly. Early on the 23rd
the system crossed 40S and then underwent an extreme acceleration to
the southeast. By 0300 UTC on 24 April the cyclone was near 53.5S,
57.5E and was being absorbed by an extratropical LOW. Convection
began to make a comeback around 1200 UTC on the 22nd and by early on
the 23rd a ragged, banding-type eye had become visible. Both Tony and
Karl agree that at 23/1200 UTC, the cyclone's appearance was the most
tropical-looking of its entire life. Satellite imagery at 1126 UTC
revealed what appeared to be a small eye (-14.8C) in the center of the
CDO feature. Karl's log increases the MSW back to 50 kts at this
juncture. However, whether or not the cyclone should be classified as
a tropical cyclone is questionable. As Karl points out in his
discussion, the storm did present a tropical appearance around 1200 UTC
on 23 April, but it was located at a rather high latitude (41S to 44S)
and over SSTs of 16-18C. Shortly after this secondary (or actually
tertiary) peak in intensity, the storm encountered renewed shear and
quickly weakened as it raced southeastward.
I would like to extend a very special thanks to Tony Cristaldi,
Philippe Caroff, and Karl Hoarau for all the information they provided
regarding this interesting storm system.
Track of the Unnamed Southwest Indian Ocean Cyclone
17 - 24 April, 2001
---------------------------------------------------
Date Time Lat Lon MSW Comments
(GMT) 1-min
(kts)
-------------------------------------------------------------------------
01 APR 17 0400 32.0 S 33.7 E Extratropical LOW
01 APR 17 1200 31.7 S 33.2 E
01 APR 17 1800 31.3 S 34.3 E
01 APR 17 2230 31.8 S 35.0 E
01 APR 18 0000 31.9 S 35.4 E 25
01 APR 18 0500 31.7 S 35.7 E 25 XT Low/1st Cb burst south of cntr
01 APR 18 1200 33.0 S 36.3 E 30 XT or Hyb/central Cb-partial CDO
01 APR 18 1730 33.3 S 36.5 E 45 Eye-like feature/little more trop.
01 APR 18 2200 33.2 S 36.9 E 45 Well-def eye/like TC embedded in XT
01 APR 19 0000 33.1 S 37.5 E 40 Cb diminishing north side of "eye"
01 APR 19 0500 33.5 S 38.1 E 40 CDO trying to re-organize
01 APR 19 1200 34.0 S 37.9 E 45 CDO better/"eye" barely visible
01 APR 19 1700 34.1 S 38.1 E 60 CBO eroded N thru SE/"eye" faint
01 APR 19 2200 34.2 S 38.4 E 50 "Eye" open SW thru W/less tropical
01 APR 19 2330 34.3 S 38.8 E 50
01 APR 20 0430 34.5 S 39.8 E 45 Central Cb ragged/sheared from NW
01 APR 20 1200 34.6 S 40.7 E 45 CDO better, more central
01 APR 20 1700 34.7 S 41.1 E 40 Cb shearing to SSE of center some
01 APR 20 2300 34.2 S 41.8 E 40
01 APR 21 0400 34.9 S 41.5 E 40 CDO better, disp. to south of LLCC
01 APR 21 1200 34.4 S 40.6 E 45 More tropical-looking/large "eye"
01 APR 21 1630 34.7 S 40.0 E 45 Large "eye" open to south
01 APR 21 2300 35.1 S 38.8 E 30 System now void of deep Cb
01 APR 22 0400 35.2 S 38.5 E 25 Weak Cb east side
01 APR 22 1130 36.3 S 37.8 E 30 Central Cb re-dev. SE of center
01 APR 22 2300 39.2 S 39.2 E 30 Cb ragged, disp. to south of LLCC
01 APR 23 0330 40.2 S 39.6 E 25 Ragged central convection
01 APR 23 0500 41.2 S 40.3 E 30 Banded, ragged eye
01 APR 23 1130 43.7 S 42.8 E 50 Most "tropical" appearance of all,
01 APR 23 1730 46.6 S 46.4 E 40 true eye in center of CDO
01 APR 23 2230 49.0 S 50.3 E 35 Accelerating rapidly SE-ward
01 APR 23 2330 49.9 S 51.2 E 30 Eye has collapsed
01 APR 24 0300 53.5 S 57.7 E 25 Being absorbed by large XT LOW
***********************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for October: 3 tropical storms
2 hurricanes
NOTE: Some 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. Some information was also obtained from the monthly
summary for October prepared by the Hurricane Specialists which is
available on TPC/NHC's website.
Atlantic Tropical Activity for October
----------------------------------------
As will be obvious to most readers of these summaries, I am far
behind schedule, just as I was last year following active Atlantic
and North Pacific seasons. Happily, the official storm reports
prepared by the staff of TPC/NHC for the Atlantic and Eastern North
Pacific basins have now appeared on NHC's website. So, just as I
did last year, I am not going to write much about the October and
November cyclones in those basins in order to facilitate getting
caught up and back on schedule. While the reports may not contain
quite as much detail about certain aspects of the storms as I might
have included, there is no need for me to spend time re-creating what
others have already accomplished. I shall confine my remarks about
the cyclones for the latter two months of the season to pointing out
a few interesting features and tidbits that were not mentioned in the
NHC reports. The reports are very nicely done and highly informative
with several figures and tables, including charts and maps of the
official analyzed "best tracks". I will include links to the specific
reports below in the write-up for each storm. I highly recommend that
all readers go to NHC's website and read the reports.
Five tropical cyclones developed during the month and all reached
tropical storm intensity. Two of these, Iris and Karen, became
hurricanes with Iris reaching Category 4 intensity on the Saffir/
Simpson scale. The last system, Tropical Depression #15, was upgraded
to Tropical Storm Michelle right around 0000 UTC on 1 November and
will be covered in the November summary. All this activity represents
an above-normal October--the average numbers of tropical storms,
hurricanes, and intense hurricanes (1950-2000) forming in the month
of October are 1.6, 1.1, and 0.3, respectively.
Hurricane Iris (TC-11)
4 - 9 October
-----------------------
Hurricane Iris was a very small tropical cyclone which intensified
rapidly in the western Caribbean Sea into a severe Category 4 hurricane
on the Saffir/Simpson scale on 8 October. The core of Iris was very
small--at one point the eye was only 3 nm in diameter and the radius
of hurricane-force winds was only 10-15 nm--very small for a 120-kt
hurricane. During the morning of the 8th reconnaissance aircraft
found three concentric eyewalls with radii of 3, 9, and 18 nm. The
innermost one soon collapsed, resulting in a temporary weakening of
Iris, but with two others close in, the hurricane was soon intensifying
again. Iris reached an estimated peak intensity of 125 kts just before
making landfall in southern Belize. This was supported by a GPS drop
which measured surface winds of 127 kts and objective T-numbers of
T6.5 to T7.0 (127 to 140 kts) for about three hours. Another GPS drop
at 1900 UTC was reporting 132 kts when it failed at 46 m above the
surface.
Comparing the official "best track" (BT) with the operational track,
only minor adjustments were made. The BT starts the depression stage
at 04/1200 UTC--six hours before the first advisory was issued--and
also upgrades Iris to tropical storm intensity six hours before it was
upgraded operationally. A slight amount of confusion resulted when
it was announced that if Iris regenerated in the Pacific, the name Iris
would be retained, but when an Eastern Pacific storm did develop from
Iris' remnants, a new number (15E) and name (Manuel) were applied. I
asked James Franklin about this and he clarified the issue: NHC's
operational procedures were changed a few years ago to the effect that
if a tropical cyclone crossed Central America and warnings were issued
continuously, then the original number and name would be retained.
However, if the original storm's LLCC dissipated and warnings were
dropped, a new number and name would be applied if a cyclone developed
subsequently in the Pacific. (The same rules would apply for the much
more rarer Pacific-to-Gulf of Mexico crossing.) In the case of Iris,
the hurricane's inner core did dissipate over Mexico, although some of
the leftover convection from Iris was instrumental in the formation of
Tropical Storm Manuel in the Pacific.
Hurricane Iris was very destructive to southern Belize, but since
the storm was very small, the path of destruction was correspondingly
narrow. The government of Belize has reported a storm damage total of
$66.2 million. This figure comes from the official NHC report;
a report located by the author on the Relief Web's website indicates
that the damage to Belize was around $250 million. (This report, dated
4 January 2002, can be located at http://www.reliefweb.int. Click on
the Natural Disasters link, then the Hurricane Iris link.) The eye
of Hurricane Iris passed over Independence and Placencia, small towns
around 130 km south of Belize City. Eighty-five percent of the banana
plantations were damaged, and corn, rice, plantain, mango, and cacao
crops were also seriously affected. Shrimp farms were also adversely
impacted by Iris.
The best estimate of the number of deaths resulting from Hurricane
Iris stands at 31. Three persons were killed in the Dominican Republic
as the storm brushed that area, but the majority of the fatalities
occurred on the boat M/V Wave Dancer, which capsized with 28 persons on
board during the height of the storm while anchored at Big Creek. At
least 20 persons on board the boat are feared dead--all members of a
diving club based in Richmond, Virginia, who were on a diving vacation
off the coast of Belize. There was also an unconfirmed report that
another boat, The Vendera, had capsized with people on board. Finally,
there were reports that eight persons had perished in flash flooding
in Guatemala associated with Iris.
The official TPC/NHC storm report on Hurricane Iris, prepared by
Lixion Avila, can be found at the following URL:
http://www.nhc.noaa.gov/2001iris.html>
Tropical Storm Jerry (TC-12)
6 - 8 October
-----------------------------
Tropical Storm Jerry was a short-lived, rather poorly-organized
tropical cyclone which formed east of the Windward Islands and moved
into the eastern Caribbean Sea where it dissipated a couple of days
later. Interestingly, the dissipation of Jerry was not anticipated.
Most of the model guidance, as well as the NHC advisories, were calling
for Jerry to reach hurricane intensity in two or three days. Jerry's
center passed just south of Barbados and very near St. Vincent, and
gale-force winds were recorded on Martinique; however, there were no
reports of damage or casualties associated with this tropical cyclone.
The official TPC/NHC storm report on Tropical Storm Jerry, prepared
by Richard Pasch and Daniel Brown, can be found at the following URL:
http://www.nhc.noaa.gov/2001jerry.html>
Hurricane Karen (TC-13 / STS #1)
10 - 15 October
---------------------------------
Hurricane Karen began as a strong extratropical LOW which caused
wind gusts well above hurricane force on Bermuda. The initial extra-
tropical cyclone subsequently evolved into a subtropical storm and
later tropical cyclone which became a Category 1 hurricane on the
Saffir/Simpson scale. Operationally, the system was not classified as
a subtropical storm until 1800 UTC on 12 October, but in post-analysis
it was determined that the parent LOW had acquired sufficient warm-
core features to be classified as a subtropical storm by 12/0000 UTC
when the cyclone was near Bermuda. The NHC storm report on Karen
includes a very detailed and interesting discussion of the thermo-
dynamic and kinematic characteristics of the system during its
evolution from extratropical to subtropical to tropical cyclone. In
the lower levels the system resembled a tropical cyclone while the
upper levels were more typical of an extratropical cyclone. There are
presently no detailed, definitive criteria for classifying such systems
as extratropical, subtropical, or tropical, and frequently it is
impossible to make the best determination about a storm system's
character and energetics until a careful study of all available data
can be accomplished during post-storm analysis.
By 0600 UTC on 13 October, temperature data from the Advanced Micro-
wave Sounding Unit (AMSU) indicated that Subtropical Storm One had
acquired enough warm-core characteristics to be classified as Tropical
Storm Karen. Karen was upgraded to a hurricane at 1800 UTC on the 13th
and reached its peak intensity of 70 kts at 14/0600 UTC based on an
objective Dvorak intensity estimate of 70 kts. Thereafter, the storm
weakened rapidly and made landfall in Nova Scotia as a 45-kt tropical
storm on 15 October.
Sustained winds to near hurricane force with gusts ranging from 78
to 85 kts were officially recorded on Bermuda. Additionally, the
cruise ship Nordic Empress reported a gust to 103 kts at 11/2317 UTC
while anchored on the west side of the island. Environmental pressures
near Bermuda were higher than normal when the pre-Karen LOW approached
and helped to create a very tight pressure gradient across the island.
The extreme gust reported by the Nordic Empress was possibly related
to strong downdrafts emanating from low-topped convection.
The strong winds caused considerable tree and powerline damage on
Bermuda. At one point 23,000 persons were without power. One cruise
ship was set adrift when its mooring line snapped, and a dozen or so
smaller boats broke loose from their moorings and either ran aground or
were sunk. Karen's rains were benefial to Nova Scotia and western
Newfoundland where a drought had been in progress, but up to 150 mm of
rain fell in twelve hours near Cape Race, resulting in the worst floods
in 100 years in St. John's. Wind gusts to 56 kts were reported in Nova
Scotia but caused only minor tree damage.
The official TPC/NHC storm report on Hurricane Karen, prepared by
Stacy Stewart, can be found at the following URL:
http://www.nhc.noaa.gov/2001karen.html>
NOTE: The official "best track" for Karen begins at 11/0600 UTC, but
gale warnings for the initial parent LOW were being issued on the 10th.
The preliminary track for Karen included in the author's cyclone tracks
file for October begins the track at 10/0000 UTC, based on information
gleaned from TPC's High Seas Forecasts.
Tropical Storm Lorenzo (TC-14)
25 - 31 October
-------------------------------
All things considered, Tropical Storm Lorenzo was the most
insignificant named storm of the 2001 Atlantic hurricane season. It
remained at sea far from any populated shores and was the only storm
not to intensify above minimal tropical storm intensity of 35 kts.
Like several of the late-season tropical cyclones, Lorenzo was not
tropical in origin--its roots lay in an upper-level trough over the
eastern Atlantic. The "best track" begins the tropical depression
stage at 1200 UTC on 27 October. In the cyclone tracks file for
October, I traced the weak parent surface LOW back to 1800 UTC on the
25th based on information contained in TPC's High Seas Forecasts. For
tropical cyclones originating from non-tropical systems, NHC normally
begins the track at the point the system began to show signs of
developing tropical characteristics, which makes sense for a tropical
cyclone database.
The official TPC/NHC storm report for Tropical Storm Lorenzo,
prepared by Miles Lawrence, can be found at the following URL:
http://www.nhc.noaa.gov/2001lorenzo.html>
***********************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for October: 1 tropical depression
2 tropical storms
2 hurricanes
Eastern North Pacific Tropical Activity for October
---------------------------------------------------
In terms of tropical storms, October, 2001, was fairly active
with four named storms (plus one non-developing tropical depression).
Two of these storms reached hurricane intensity. For the period
1971-2000, the average number of named storms and hurricanes for
October has been 1.9 and 1.1, respectively. The most active October
in terms of tropical storms was in 1992 when five developed. However,
October, 1983, stands as the most active month of October on record
in terms of net tropical cyclone activity. Three intense hurricanes
traversed Eastern Pacific waters during that month.
Since the official storm reports are now available on TPC/NHC's
website, and since the storms were rather insignificant and did not
affect land, I am not going to attempt to summarize them individually.
Tropical Storm Lorena formed in early October south of the Mexican
coast and at one point looked like it was going to make landfall, but
shear increased and the storm dissipated west of Manzanillo. Tropical
Depression 14E formed several hundred miles southwest of the Baja
California peninsula while Lorena was operating further east, but
dissipated within 30 hours after the first advisory was issued.
Tropical Storm Manuel formed from the remnants of Caribbean Hurricane
Iris and pursued a westerly and west-northwesterly track away from the
mainland. Manuel intensified to 45 kts, weakened to a depression,
then re-intensified, reaching a peak intensity of 50 kts on the 16th.
It should be noted that Manuel did not form from the core circulation
of Iris--that dissipated over Mexico--but rather developed in
association with some convection from Iris which had moved southward
over Pacific waters. Had the actual circulation of Iris reached the
Pacific intact and re-intensified, it would have retained the name
Iris. Hurricanes Narda and Octave were twins--both formed in the same
general area roughly 1000 nm southwest of Baja California, both reached
a peak intensity of 75 kts, and both lasted for only four or five days
as they pursued similar west-northwestward tracks.
In the table below I have included the links to the official NHC
reports for all the 2001 Eastern Pacific tropical cyclones as well
as the name of the author of each report. I highly recommend that
readers go to NHC's website and read the reports.
Cyclone Link Author(s)
------------------------------------------------------------------------
Adolph http://www.nhc.noaa.gov/2001adolph.html> Stacy Stewart
Barbara http://www.nhc.noaa.gov/2001barbara.html> Jack Beven
Cosme http://www.nhc.noaa.gov/2001cosme.html> James Franklin
Erick http://www.nhc.noaa.gov/2001erick.html> Lixion Avila
Dalila http://www.nhc.noaa.gov/2001dalila.html> Miles Lawrence
TD-06E http://www.nhc.noaa.gov/2001six-e.html> Richard Pasch
Flossie http://www.nhc.noaa.gov/2001flossie.html> Stacy Stewart
Gil http://www.nhc.noaa.gov/2001gil.html> Jack Beven
Henriette http://www.nhc.noaa.gov/2001henriette.html> Daniel Brown/
James Franklin
Ivo http://www.nhc.noaa.gov/2001ivo.html> Lixion Avila
Juliette http://www.nhc.noaa.gov/2001juliette.html> Miles Lawrence/
Michelle Mainelli
Kiko http://www.nhc.noaa.gov/2001kiko.html> Richard Pasch
Lorena http://www.nhc.noaa.gov/2001lorena.html> Stacy Stewart
TD-14E http://www.nhc.noaa.gov/2001fourteen-e.html> Jack Beven
Manuel http://www.nhc.noaa.gov/2001manuel.html> James Franklin
Narda http://www.nhc.noaa.gov/2001narda.html> Lixion Avila
Octave http://www.nhc.noaa.gov/2001octave.html> Miles Lawrence
Tropical cyclone activity was very minimal in the Central North
Pacific region during 2001. The Central Pacific Hurricane Center to
my knowledge has not prepared any storm reports such as those by
TPC/NHC, but a brief end-of-season summary can be found at the website
for the CPHC:
http://205.156.54.206/pr/hnl/cphc/pages/cphc.shtml>
Click on the link: Year End Summary
***********************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for October: 1 tropical depression **
2 typhoons
1 super typhoon
** - This system was treated as a tropical depression by JMA and
some of the other Asian TCWCs, but not by JTWC
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 some of the Asian warning centers 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. Also, a special thanks to
Huang Chunliang of Fuzhou City, China, for sending me tracks based on
warnings from the National Meteorological Center of China (NMCC), the
Hong Kong Observatory (HKO), and the Central Weather Bureau of
Taiwan (CWBT).
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
-----------------------------------------------
Tropical cyclone activity in the Northwest Pacific basin was down
some from the level seen during August and September, but was probably
about normal for the month. Three tropical cyclones were named, and
all three reached typhoon intensity. Typhoon Krosa formed near the
Marianas Islands, moved northwestward and executed a fairly smooth
recurvature south of Japan. Typhoon Haiyan formed in the Philippine
Sea and recurved about midway between northern Taiwan and Okinawa.
Both Krosa and Haiyan were typhoons of moderate intensity, but the
third typhoon of the month, Podul, became an intense and long-lived
super typhoon. Podul formed near Pohnpei, farther east than most of
the year's tropical cyclones, and followed a generally northward track
well-removed from any populated areas except for a brush with the
small island of Minami Tori Shima (Marcus Island). Podul also was
the first in a parade of tropical cyclones forming at very low
latitudes during the latter months of 2001.
One other system was classified as a tropical depression by JMA
during October. The initial disturbance can be traced back to an
area of convection that formed on 17 October east of Palau. During
succeeding days the system moved westward, crossing Mindanao on the
19th and 20th and emerging into the South China Sea. JTWC upgraded
the development potential to fair in a special STWO issued at 2100 UTC
on 20 October. A weak LLCC was present just west of Mindanao with
some convection organizing around the center. JMA classified the
system as a weak depression in their High Seas Summary at 21/0000 UTC
when the center was a couple hundred miles east of the Vietnamese
coast. JTWC issued a TCFA at 21/0300 UTC, noting that the disturbance
was embedded in a broad expanse of convection associated with the
monsoon trough. The LOW continued moving westward at around 15 kts
and had moved inland into Vietnam by 21/1800 UTC. With the LLCC
inland with no further chance of development, JTWC cancelled the TCFA
at 22/0200 UTC.
Even though the depression's winds were weak, it had precipitation
power. Torrential rains fell over portions of Vietnam's central
provinces, leading to flash floods and river flooding. A press report
sent to the author by Huang Chunliang indicated that since August,
floods and lightning had killed 361 people in Vietnam. Earlier
flooding in the Mekong Delta had claimed 322 lives, and 39 persons
had died recently in the nine central provinces, likely due to the
effects of the tropical depression. Three of these deaths were due
to lightning. Total flood damages were estimated to be $66.6 million.
Typhoon Krosa (TC-24W / TY 0120)
3 - 11 October
---------------------------------
Krosa: contributed by Cambodia, is the Cambodian word for crane (a
type of bird)
A. Storm Origins
----------------
A persistent area of convection developed in early October near the
Marianas Islands and on the 3rd was located just east of Guam.
Animated satellite imagery depicted unorganized convection associated
with a weak LLCC in the area. As the day progressed the disturbance
began to develop rather rapidly. JTWC issued a TCFA at 1600 UTC as
radar depicted a LLCC west of Rota on the southern edge of some deep
convection and synoptic data indicated falling pressures in the region.
A 200-mb analysis indicated that the system was located in an area of
weak vertical shear with good outflow aloft.
JTWC issued the first warning on Tropical Depression 24W at 1800 UTC
with the center located approximately 40 nm north-northwest of Guam or
about 30 nm west of Rota. (A post-storm track indicates that it is
likely the system had reached depression status by 03/1200 UTC.) Deep
convection continued to increase and JTWC upgraded the depression to
a tropical storm at 04/0000 UTC when the center was located about
100 nm northwest of Guam or a like distance west-southwest of Saipan.
JMA classified the system as a tropical depression at 0000 UTC, and at
0600 UTC upgraded the cyclone to Tropical Storm Krosa while at the
same time JTWC upped the MSW to 45 kts.
B. Track and Intensity History
------------------------------
Krosa tracked rather quickly northwestward away from the Marianas
on 4 October as it was steered by a mid-level subtropical ridge to its
northeast. The storm also continued to intensify steadily in a
favorable environment with water vapor imagery indicating the develop-
ment of a poleward outflow channel. By 1800 UTC JTWC had upped the
MSW to 60 kts based on CI estimates of 55 and 65 kts. JTWC upgraded
Krosa to a 65-kt typhoon at 05/0000 UTC when it was located roughly
400 nm west-northwest of Saipan. Between 0600 and 1200 UTC the cyclone
underwent rapid intensification, reaching its peak intensity of 105 kts
at 1200 UTC (per JTWC's analysis) when located about 380 nm southwest
of Iwo Jima. Enhanced infrared satellite imagery and a recent SSM/I
pass indicated that an intense convective ring had developed over the
previous few hours, and animation indicated that the eyewall had
contracted around a 14-nm diameter irregular eye. Water vapor imagery
revealed a pronounced poleward outflow channel extending from the
system. Gales extended outward about 180 nm from the center in the
northern semicircle and about 115 nm to the south. The radius of
storm-force winds was estimated to be 60 nm.
Typhoon Krosa tracked in an increasingly northward direction on the
6th as it moved around the western edge of the subtropical ridge and by
1800 UTC was moving north-northeastward. The storm reached the
westernmost point of its track at 06/0600 UTC when it was centered
approximately 385 nm west-southwest of Iwo Jima. The typhoon held its
own, although there were some signs that it had weakened slightly: the
eye became less defined and convection weakened some. JTWC reduced the
intensity to 100 kts at 0000 UTC where it remained for 24 hours.
Interestingly, the tracks from JMA and NMCC depict Krosa reaching its
peak intensity (10-min avg) of 80 kts and 90 kts, respectively, at
06/1200 UTC. On 7 October JTWC decreased the MSW to 95 kts at 0000 UTC
and to 90 kts at 0600 UTC where it remained through 1800 UTC. It
should be noted, however, that at least one CI estimate remained at
102 kts through 1200 UTC. By 1200 UTC both NMCC and JMA indicated
some weakening of the typhoon. At 07/0000 UTC Krosa was located about
300 nm west of Iwo Jima, moving northeastward at 10 kts. This fairly
slow northeastward motion continued throughout the 7th.
The storm continued to slowly weaken on the 8th with the intensity
dropping to 75 kts by 0600 UTC (although one CI estimate remained at
90 kts through 1200 UTC). Typhoon Krosa passed approximately 275 nm
north of Iwo Jima around 0900 UTC as it began to accelerate northeast-
ward. The cyclone's track gradually shifted more to the right, and by
1800 UTC Krosa was racing east-northeastward at 27 kts. The storm was
also showing signs of extratropical transition as it encountered shear
from the mid-latitude westerlies. JTWC issued their final warning on
Krosa at 09/0600 UTC, downgrading it to a 55-kt extratropical LOW
located about 575 nm east-southeast of Tokyo or about 650 nm south-
southeast of the Kuril Islands. The system was developing frontal
features as it moved further into a baroclinic zone. NMCC also dropped
the storm at 0600 UTC, but JMA carried it through two more warning
cycles before declaring Krosa extratropical at 1800 UTC. The potent
extratropical storm continued rapidly east-northeastward, crossing the
Dateline late on the 10th, and at 11/0000 UTC was still generating
60-kt winds well south of the Aleutian Islands.
C. Comparisons Between JTWC and Other Centers
---------------------------------------------
The MSW estimates from NMCC and JMA compared rather well with those
from JTWC (after adjusting for the different averaging times) for most
of Typhoon Krosa's history. NMCC's estimated peak intensity of 90 kts
compares very well with JTWC's peak MSW of 105 kts. JMA's peak of
80 kts is a little lower, but still in fairly good agreement. As noted
above, the interesting thing is that both the Asian TCWC's time of
peak intensity for Krosa was shifted later than JTWC's. JTWC's peak
of 105 kts was from 05/1200 through 06/0000 UTC, JMA's peak intensity
of 80 kts occurred from 06/1200 through 07/1200 UTC, and NMCC estimated
their peak of 90 kts from 06/1200 through 07/0600 UTC. The minimum
central pressure estimated by JMA was 950 mb from 06/1200 through
07/1200 UTC.
D. Damage and Casualties
------------------------
No reports of damage or casualties resulting from Typhoon Krosa have
been received.
Typhoon Haiyan (TC-25W / TY 0121 / Maring)
11 - 19 October
-------------------------------------------
Haiyan: contributed by China, is the name of a bird--the petrel
A. Storm Origins
----------------
On 7 October a persistent area of convection was noted deep in the
tropics far to the south-southwest of Guam. Animated satellite imagery
depicted organized convection associated with a weak LLCC. The system
remained quasi-stationary on the 8th, but by the 9th had moved north-
westward to a position about 100 nm southeast of Yap. Convection had
decreased some, but a 200-mb analysis indicated that the disturbance
lay beneath diffluent easterlies associated with a sub-equatorial
ridge. At 10/0600 UTC the system was relocated to a point about
275 nm northeast of Yap. Convection was scattered, but by 1400 UTC
deep convection was seen to be increasing so JTWC upgraded the develop-
ment potential to fair.
The disturbance was relocated significantly to the northwest at
11/0600 UTC to a position approximately 510 nm northwest of Yap. The
system's organization was continuing to improve in a region of weak
vertical shear and good outflow. Also at 0600 UTC, PAGASA initiated
warnings on the system, naming it Tropical Depression Maring (a
Filipino nickname) with 30-kt winds. (Although JTWC did not issue the
first warning until 1200 UTC, a post-storm track begins Maring/25W as
a depression at 0600 UTC.) JTWC issued a TCFA at 0700 UTC, followed
at 1200 UTC by the first warning on Tropical Depression 25W, located
approximately 470 nm east of northern Luzon. The MSW was estimated
at 25 kts and the depression was moving west-northwestward at 16 kts.
Deep convection was erupting on the northern edge of the LLCC.
JMA classified the system as a 30-kt tropical depression at 1800
UTC. JTWC's MSW remained at 25 kts based on CI estimates of 25 and
35 kts plus synoptic reports. JTWC upped the intensity to 30 kts at
12/0000 UTC and to tropical storm status at 0600 UTC. Maring's
rather rapid west-northwestward motion had come to a halt--the cyclone
was by this time moving northwestward at only 3 kts. By 1800 UTC
the available CI estimates were all 35 kts so JMA upgraded Maring/25W
to Tropical Storm Haiyan with 35-kt winds (10-min avg). JTWC's 1-min
avg MSW was also still reported as 35 kts in the 1800 UTC warning.
B. Track and Intensity History
------------------------------
Tropical Storm Haiyan moved little on 13 October. The cyclone
remained quasi-stationary most of the day roughly 450 nm east of
the northeastern tip of Luzon as it slowly strengthened. JTWC upped
the MSW to 45 kts at 0000 UTC and to 50 kts at 1200 UTC as animated
visible satellite imagery depicted building deep convection over the
LLCC. By late in the day Haiyan was drifting northward at 3 kts in
a weakened ridge flow pattern of the subtropical ridge. A SSM/I pass
during the (local) morning resulted in a 40-nm southward adjustment in
the storm's position. JTWC upgraded Haiyan to typhoon status at
14/0000 UTC based on current intensity estimates of 45 and 55 kts and
synoptic reports. Satellite imagery indicated that the southwest
monsoonal flow out of the Philippine Sea was enhancing the banding
features and expanding the stronger winds over the eastern semicircle.
By 0600 UTC Haiyan had turned to a slightly faster north-northwestward
track about 500 nm east-southeast of Taipei. Satellite intensity
estimates had reached typhoon force by 1200 UTC and the MSW was bumped
up to 70 kts. A 14/0944 UTC TRMM pass had indicated that an eye was
forming under extensive deep convection. At 1800 UTC Haiyan's center
was located about 265 nm south of Okinawa, and the storm's heading had
turned to the west-northwest as the subtropical ridge strengthened
slightly following the passage of a shortwave trough to the north.
JTWC increased the MSW slightly to 75 kts, and NMCC and PAGASA both
upgraded Haiyan to typhoon status. (JMA did not upgrade the storm
for another 24 hours.)
During the 15th Typhoon Haiyan tracked initially westward and west-
northwestward, but by 1800 UTC the storm had turned to the northwest.
The mid-level ridge to the north was being weakened by the approach
of a mid-latitude trough from the west. JTWC gradually increased the
MSW to the peak for the storm of 90 kts at 1800 UTC. Satellite
intensity estimates had reached 90 kts by this time and a ragged eye
was visible. Haiyan was located at 1800 UTC about 200 nm southwest of
Okinawa, moving northwestward at 10 kts. Gales covered an area almost
400 nm in diameter, and 50-kt winds extended outward 80 nm from the
center. The forecast northward turn became reality on 16 October.
At 0600 UTC the typhoon was moving northward, and by 1800 UTC Haiyan
had passed north of the subtropical ridge axis and was trekking north-
eastward under the steering influence of the mid-level ridge to the
east. Although there were a couple of CI estimates of 102 kts (T5.5),
JTWC did not raise their MSW estimate above 90 kts. At 1800 UTC Haiyan
was located about 100 nm west of Okinawa and was beginning to show
signs of extratropical transition--the MSW had been lowered to 75 kts
by this time.
On the 17th Haiyan began to get caught up more and more in the mid-
latitude westerlies. At 17/0000 UTC the storm was located about 80 nm
northwest of Okinawa and moving northeastward at 11 kts. By 1800 UTC
the center was approximately 230 nm southeast of Sasebo, or 500 nm
southwest of Tokyo, and scooting east-northeastward at 23 kts. The
intensity continued to slowly decline as the day progressed, although
infrared imagery indicated some re-development of deep convection
during the (local) night. At 1800 UTC JTWC downgraded Haiyan to a
60-kt extratropical storm and issued their final warning. JMA carried
the cyclone as a tropical storm for another twelve hours, then declared
Haiyan to be extratropical at 18/1200 UTC. The remnant extratropical
gale continued moving eastward, and at 19/1800 UTC was still generating
35-kt winds about 950 nm east of Tokyo. However, I was unable to find
any further references to the system in JMA's High Seas Warnings, so
presumably it weakened thereafter or else was absorbed by another
system.
C. Comparisons Between JTWC and Other Centers
---------------------------------------------
Intensity estimates between JMA and JTWC, after allowing for the
different averaging periods, were in good agreement during the early
stages of Haiyan's life when the storm was intensifying, and again
during the rather rapid decaying phase. JMA's peak 10-min avg MSW
of 70 kts was a little low compared to JTWC's 90-kt peak MSW, but
not unusually so. NMCC's peak 10-min avg MSW estimate of 80 kts
was in excellent agreement with JTWC's peak intensity. PAGASA had
reached 70 kts when Haiyan exited its AOR after 16/0000 UTC; however,
this was during the time of the storm's peak per the other centers.
CWBT and HKO estimated the storm's intensity (10-min avg) at 70 and
75 kts, respectively, during the time that Haiyan was within their
AORs. The minimum central pressure estimated by JMA was 960 mb from
16/0000 through 16/1800 UTC.
D. Meteorological Observations
------------------------------
I received a few rainfall reports from Huang Chunliang which had
been sent to him by Chun-Chieh Wu of the National Taiwan University.
These represent storm totals for the period 14/1600 UTC through
16/1400 UTC for several stations on Taiwan:
Station Rainfall (mm)
-------------------------------------------------
Neo-Tsu, Hsinchu County 322
Anpu, Chutzhu 234
Tung-Hou, Taipei County 223
Ta-Chi, Taoyuan County 214
Kuang-Wu, Miaoli County 185
Da-Cho-C, Ilan County 160
E. Damage and Casualties
------------------------
No reports of damage or deaths resulting from Typhoon Haiyan/Maring
have been received.
Super Typhoon Podul (TC-26W / TY 0122)
18 - 29 October
---------------------------------------
Podul: contributed by DPR Korea (North Korea), is the Korean name for
the willow tree
A. Storm Origins
----------------
On 16 October a persistent area of convection was located deep in
the tropics near Pohnpei. Animated visible and infrared imagery
indicated disorganized convection associated with a weak LLCC. CIMSS
analysis indicated fair outflow and weak to moderate vertical shear.
Little change was noted on the 17th, except that the area of convection
shifted about 120 nm to the south. At 1200 UTC JTWC upgraded the
potential for development to fair. Deep convection was becoming better
organized and a CIMSS analysis indicated that outflow was improving and
shear was lessening over the region. JTWC issued a TCFA at 2200 UTC
after a considerable increase in the coverage of deep convection had
been observed. Also, a 17/1920 UTC QuikScat pass had indicated a LLCC
situated over a surface trough just south of Pohnpei.
JMA was the first warning agency to classify the developing cyclone
as a tropical depression. At 18/0000 UTC JMA located a 30-kt tropical
depression slightly over 100 nm southwest of Pohnpei. JTWC re-issued
the TCFA at 2200 UTC followed by the first warning on Tropical
Depression 26W at 19/0000 UTC. (A post-storm track retroactively
identifies the system as a depression at 18/1800 UTC.) The center of
TD-26W was located approximately 150 nm west-southwest of Pohnpei or
about 270 nm east-southeast of Chuuk. The warning intensity of 30 kts
was based on CI estimates of 25 and 30 kts. The partially-exposed LLCC
was decoupled to the east of the deep convection.
By 1200 UTC CI estimates were 30 and 35 kts, so JTWC upgraded the
depression to tropical storm status, still pretty much in the same
location. A 19/0754 UTC SSM/I pass had revealed a partially-exposed
center to the northeast of the nearest deep convection. However, more
recent enhanced infrared imagery depicted deep convection building over
the LLCC. Organization had improved by 20/0000 UTC, and with CI
estimates of 35 and 45 kts, JTWC increased the MSW to 45 kts. At the
same time, JMA upgraded the cyclone to tropical storm status, assigning
the name Podul. Tropical Storm Podul was then located about 250 nm
east of Chuuk, moving northward at 4 kts.
B. Track and Intensity History
------------------------------
Podul's intensity remained pegged at 45 kts for about 18 hours on
20 October, but deep convection continued to increase and organize
near the system's center. JTWC upped the MSW to 55 kts at 1800 UTC
and to typhoon intensity at 21/0000 UTC when Podul was centered about
260 nm north-northwest of Pohnpei or roughly 700 nm east of Guam.
The typhoon continued to trek toward the north as a weakness in the
subtropical ridge allowed a near-equatorial ridge south and east of
the system to exert a steering influence on Podul. Intensification
of the cyclone proceeded at a rather slow rate. The MSW was increased
to 75 kts at 21/1200 UTC and remained there for 18 hours. NMCC and
JMA both upgraded Podul to typhoon status at 22/0000 UTC.
Typhoon Podul plodded northward on 22 October, shifting to a north-
northeastward track late in the day. The primary steering mechanism
remained a mid-level near-equatorial ridge southeast of the storm, but
a cutoff LOW to the northeast apparently was the factor causing the
northeastward jog in Podul's track. Podul continued its slow intensi-
fication with winds reaching 90 kts by 1200 UTC. A 22/1117 UTC SSM/I
pass indicated a developing banding eye feature, while animated water
vapor imagery revealed favorable conditions aloft with dual outflow
channels. The northeastward motion continued early on the 23rd, but
by 1200 UTC had become north-northwesterly as a major shortwave ridge
moving off Japan and a building mid-level peripheral ridge helped
to provide a more northwestward track while the cutoff LOW filled and
lifted out to the northeast. JTWC increased the MSW to 100 kts at
23/0000 UTC and steady intensification continued throughout the day.
Winds were upped to 115 kts at 0600 UTC as satellite imagery indicated
that the eyewall had contracted around a cloud-free eye. By 1800 UTC
Dvorak numbers had reached T7.0 from SAB, JTWC and KGWC, therefore,
Podul was upgraded to the season's second super typhoon with 135-kt
winds, located approximately 550 nm west-southwest of Wake Island.
The storm was then moving northwestward at 4 kts, but was forecast to
recurve to the north and northeast as a mid-latitude trough approached
from the northwest.
Super Typhoon Podul's slow northwestward trek continued on
24 October, becoming slightly west-northwestward as the day progressed.
The storm intensified further with the estimated MSW reaching 140 kts
at 0600 UTC. Satellite imagery revealed that Podul underwent a
concentric eyewall cycle on the 24th--by 0600 UTC the eye diameter had
expanded slightly to 24 nm. Gales extended outward 170 nm from the
center to the southwest and out 155 nm in the northern semicircle.
The radius of 50-kt winds was estimated to be around 50-60 nm. JTWC
lowered the intensity to 130 kts for a 12-hour period beginning at
25/0000 UTC but bumped it back up to 140 kts at 1200 UTC. The eye
diameter had increased to 30 nm by 25/0000 UTC and storm-force winds
extended outward 80 nm from the center. Podul maintained the 140-kt
intensity for 24 hours the second round. During this period JMA and
NMCC both estimated their peak intensities of 100 and 120 kts,
respectively, while JMA estimated a minimum CP of 925 mb for the
typhoon's history.
By 1800 UTC on the 25th Podul's motion had become northerly as
the mid-latitude trough east of Japan continued to deepen and weaken
the subtropical ridge. The cyclone at this time was located about
500 nm east of the northernmost Marianas Islands, and this represents
the westernmost point in Podul's track. Although satellite intensity
estimates were still 140 kts at 26/1200 UTC, JTWC lowered the MSW to
130 kts as the storm began to show signs of weakening. Enhanced
infrared imagery revealed cirrus streaming northeastward and a decrease
in convection in the southwestern quadrant. Even though still a super
typhoon, Podul was showing the first hints of extratropical transition.
By 1800 UTC Podul was located approximately 700 nm northwest of Wake
Island and was moving north-northeastward at 22 kts. JTWC decreased
the MSW to 120 kts, thus ending Podul's reign as a super typhoon.
Podul had maintained super typhoon intensity (MSW 130 kts or higher)
for 72 hours, making it the longest-lived super typhoon since Keith in
November of 1997 which was a super typhoon for 3.5 days. According to
Mark Lander, Super Typhoon Joan just a month earlier in October, 1997,
holds the record for the longest continuous period of 130+ kt winds.
Joan maintained super typhoon status for 4.5 days, peaking at 160 kts.
JTWC reduced the MSW to 100 kts at 27/0000 UTC, noting that animated
satellite imagery indicated dry air entrainment and cold air advection
in the southwestern quadrant. As the day progressed Podul continued
to accelerate north-northeastward and weaken. By 1800 UTC JTWC judged
the system to have completed extratropical transition and issued their
final warning, locating the center south of the Kamchatka Peninsula
approximately 1000 nm east of Japan and racing north-northeastward at
32 kts. Winds were still at typhoon strength, however, and JMA also
was still classifying Podul as a typhoon. JMA continued to issue
warnings on Podul as a tropical storm through 28/0600 UTC, declaring
the system extratropical at 1200 UTC. The remnant extratropical LOW
subsequently turned eastward and weakened--by 29/0600 UTC it was a
996-mb LOW well south of the Aleutians, just west of the Dateline.
C. Comparisons Between JTWC and Other Centers
---------------------------------------------
NMCC's peak 10-min avg MSW of 120 kts agrees very well with JTWC's
estimated 140-kt peak intensity. NMCC maintained an intensity of
110 kts from 24/0600 through 26/1800 UTC, closely matching JTWC's
period of super typhoon intensity for Podul. JMA's estimated peak
10-min avg MSW of 100 kts was reached briefly at 24/0000 UTC, and
again from 25/1200 through 26/0600 UTC. JMA's estimated 10-min avg
MSW remained at 90 kts or higher from 23/1200 through 26/1800 UTC.
The minimum central pressure estimated by JMA was 925 mb from 25/1200
through 26/0600 UTC.
D. Meteorological Observations
------------------------------
The only observations I have available came from the small island of
Minami Tori Shima (also known as Marcus Island). These were obtained
by Rich Henning. At first it appeared that the intense typhoon might
pass directly over the small island, but the center appeared to pass
just to the east. The lowest pressure reported was 967 mb at 1000 UTC
on 26 October while the peak sustained wind was 44 kts at 0900 UTC.
Winds exceeded gale force from 0300 through 1200 UTC, coming initially
from the east-northeast and veering around to the northwest as the
center passed by.
E. Damage and Casualties
------------------------
Even though Podul was a very intense typhoon, other than the brush
with Minami Tori Shima, it remained well away from any land areas. No
reports of damage or casualties have been received.
***********************************************************************
NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea
Activity for October: 2 tropical cyclones of gale intensity **
** - One of these was classified as a cyclonic storm by IMD only
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.
North Indian Ocean Tropical Activity for October
------------------------------------------------
Two weak tropical cyclonic systems were tracked in the North Indian
Ocean basin during October. The first one, in the Arabian Sea, was
designated as Tropical Cyclone 03A by JTWC and briefly reached minimal
tropical storm intensity. The second system developed in the Bay of
Bengal and moved westward into southeastern India. JTWC did not issue
warnings on this disturbance, but IMD classified it as a cyclonic storm
(i.e., a tropical storm).
Tropical Cyclone (TC-03A)
9 - 10 October
--------------------------
An area of convection developed on 7 October about 100 nm west-
southwest of Bombay. A weak LLCC which had tracked westward off the
coast of India was associated with the convection, which was increasing
in organization. JTWC upgraded the development potential to fair at
0500 UTC on the 8th, noting that convection was continuing to increase
and that the disturbance was located in an area of fairly weak vertical
shear with good outflow aloft. However, a 08/1625 SSM/I pass failed to
indicate any significant organization. A TCFA was issued at 0300 UTC
on the 9th. Early morning visible satellite imagery and a 09/0055 UTC
QuikScat pass indicated that a LLCC had developed beneath an intense
mid-tropospheric cyclone with deep convection and the strongest winds
in the northern quadrant. The first warning on TC-03A was issued at
09/0600 UTC with the initial intensity estimated at 30 kts. Visible
satellite imagery indicated the development of a banding cloud feature
in the western semicircle. A 200-mb analysis indicated diffluent flow
extending over the region.
JTWC increased the MSW to 35 kts at 09/1200 UTC. The cyclone's
center was located approximately 250 nm west of Bombay or about 370 nm
south of Karachi, Pakistan, tracking west-northwestward at 7 kts as
it was steered by a mid-level ridge anchored over the northeastern
Arabian Sea. Some recent microwave images depicted convective bands
surrounding the LLCC and 37 GHz data from a 09/0913 UTC TRMM pass
indicated that the low-level convection was most intense on the
northern side in convergent flow. The intensification trend for
TC-03A, however, was quite brief. At 1800 UTC, even though Dvorak CI
estimates were still 35 kts, a QuikScat pass revealed peak winds of
30 kts and it was felt that the QuikScat winds were more representative
and in line with the current imagery trend. Also, deep convection had
dissipated over the LLCC, so the MSW was lowered back to 30 kts.
The cyclone continued to slowly weaken as it drifted to the west-
northwest across the Arabian Sea. Entrainment of dry air from the
north was another inhibiting factor in the system's demise. By 10/0600
UTC the LLCC had decoupled from the deep convection farther north and
the MSW was lowered to 25 kts. The final JTWC warning was issued at
1200 UTC with the exposed, convection-free LLCC located about 400 nm
south of Karachi, drifting slowly northward. Re-intensification was
not considered likely given the unfavorable upper-level conditions and
the dry air environment into which the system was moving. (NOTE: I
was unable to obtain any bulletins or outlooks from IMD on the 10th
and 11th, so I do not know if that agency ever classified TC-03A as
a cyclonic storm. IMD's Tropical Weather Outlook issued at 09/0711
UTC referred to the system as a depression.)
Bay of Bengal Cyclonic Storm
15 - 16 October
----------------------------
An area of convection developed in the Bay of Bengal about 325 nm
south-southwest of Cuttack, India, on 13 October. Synoptic data
revealed a broad LLCC beneath the convection, and a 200-mb analysis
indicated that the subtropical ridge extended over the region. The
system drifted westward on the 14th with little change in intensity.
Late on the 14th the LOW seemed to be getting better organized, so
JTWC upgraded the development potential to fair. Enhanced infrared
and early morning visible imagery on the 15th indicated a significant
improvement in the convective organization of the system, so JTWC
issued a TCFA at 15/0300 UTC. A 15/0003 UTC QuikScat pass indicated
a 25-30 kt LLCC. The system was centered approximately 115 nm north-
east of Madras at the time. In the meantime, IMD had classified the
LOW as a depression by early on the 15th.
By 0900 UTC IMD had upgraded the depression to a deep depression
(MSW of 30 kts), and at 1200 UTC it was further upgraded to a cyclonic
storm (MSW of 35 kts). The storm was then located about 75 nm east-
northeast of Madras or 90 nm east-southeast of Nellore. In the SWTO
issued at 1800 UTC, JTWC mentioned that a 15/1232 UTC QuikScat pass
had revealed a LLCC with 25-30 kt winds, therefore, JTWC did not
initiate warnings on the system. A second TCFA was issued at 16/0300
UTC, noting that the center was exposed with the convection sheared to
the west. However, a bulletin issued by IMD at the same time indicated
that the center of the cyclonic storm had crossed the south Andhra
Pradesh coast earlier in the morning near Nellore. With the center
inland, JTWC cancelled the TCFA at 1600 UTC. Bulletins from IMD
indicated that the system had weakened into a depression by 16/2100
UTC and was centered about 100 km northwest of Nellore. By 0300 UTC
on the 17th the system had moved northwestward and weakened further
over central Andhra Pradesh.
***********************************************************************
SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E
Activity for October: 1 tropical depression ++
1 severe tropical storm **
++ - Classified as a minimal tropical storm by JTWC
** - System originated east of 90E in the Australian Region
The primary sources of information upon which the narrative is based
are the warnings issued by the TCWC on La Reunion Island, part of Meteo
France, which is the RSMC for the Southwest Indian Ocean basin.
However, cyclones in this region are named by the sub-regional centres
on Mauritius and Madagascar with longitude 55E being the dividing line
between their respective areas. La Reunion only advises these centres
regarding the intensity of tropical systems. References to sustained
winds should be understood as implying a 10-min averaging period unless
otherwise stated. In the accompanying tracks file some position
comparisons have been made with JTWC's positions, and warnings from
JTWC were used as a source of 1-min avg MSW estimates.
Southwest Indian Ocean Tropical Activity for October
----------------------------------------------------
Not long after the sun had crossed the equator on its annual south-
ward journey, the first stirrings in the South Indian Ocean began
to be seen. A disturbance during the first week of October a few
hundred miles east of Diego Garcia became both JTWC's and RSMC La
Reunion's first numbered tropical system of the 2001-2002 Southern
Hemisphere season. The system remained weak, but since JTWC briefly
upgraded the winds to 35 kts, and since MFR archives 30-kt tropical
depressions in their Best Track database, I am including a short
summary of this depression below. Late in the month the Southwest
Indian basin saw more tropical cyclone activity in the form of a
visitor from the Australian Region. Tropical Cyclone Alex was named
by the Perth TCWC on 26 October and subsequently moved westward,
crossing longitude 90E the next day and receiving the name Andre from
the Mauritius Meteorological Service. Since Alex-Andre originated
in the Perth TCWC, it will be covered in the Northwest Australia/
Southeast Indian Ocean section of this summary.
Tropical Depression (TC-01S / MFR #01)
4 - 8 October
---------------------------------------
A STWO issued by JTWC at 0400 UTC on 2 October mentioned that an
area of convection had formed several hundred miles east of Diego
Garcia. Satellite imagery revealed disorganized convection in the
area and a QuikScat pass indicated the existence of a weak LLCC.
By the 3rd the system had moved to the southwest from its position
the previous day and seemed a bit better organized, so JTWC upgraded
the development potential to fair. Some deep convection was noted,
and a 200-mb analysis indicated that the disturbance lay beneath an
upper-level ridge axis under diffluent flow. Satellite imagery on
4 October revealed an exposed LLCC to the northeast of deep convection.
The LOW was located roughly 600 nm east-southeast of Diego Garcia, and
lay on the equatorward side of an upper-level ridge axis with moderate
northeasterlies aloft. The maximum winds were estimated to be 20 to
25 kts.
The system remained quasi-stationary on the 5th with little change
in appearance. MFR initiated warnings on the developing system at
05/0600 UTC with the center located roughly 650 nm east-southeast of
Diego Garcia. By late in the day animated satellite imagery depicted
an increase in deep convection over a partially-exposed LLCC, so JTWC
issued a TCFA at 2300 UTC. In the meantime MFR had upgraded the
disturbance to tropical depression status with 30-kt winds (10-min
mean) at 1800 UTC. The depression was still experiencing some vertical
shear, but had good outflow aloft. JTWC issued their first warning on
TC-01S at 06/0600 UTC, placing the center about 665 nm east-southeast
of Diego Garcia and moving southward at 7 kts. The initial warning
intensity was estimated at 35-kts (1-min avg), which was very much in
line with MFR's estimated 10-min avg wind of 30 kts. Satellite imagery
revealed an exposed LLCC approximately 30 nm east of the deep
convection. A 200-mb analysis indicated that the system lay under 20
to 30 kts of vertical shear.
MFR's intensity estimate remained at 30 kts, and on the second JTWC
warning at 06/1800 UTC, the MSW was lowered to 30 kts. The center
remained exposed and convection was weakening. Over the next couple
of days the system moved slowly southward and southwestward. The
center remained partially-exposed with cycling convection which
gradually weakened. MFR downgraded the depression to a tropical
disturbance at 0600 UTC on the 7th and issued their final bulletin at
07/1800 UTC. The final JTWC warning at 08/0600 UTC noted that
animated satellite imagery revealed very weak cycling convection with
no evidence of a LLCC. The dissipating system's final position was
approximately 720 nm southeast of Diego Garcia. No casualties or
damage are known to have resulted from this tropical depression.
***********************************************************************
NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E
Activity for October: 1 tropical cyclone of storm intensity **
** - System moved west of 90E into Southwest Indian Ocean basin
The primary sources of information for Northwest Australia/Southeast
Indian Ocean tropical cyclones are the warnings and bulletins issued by
the TCWC at Perth, Western Australia, and Darwin, Northern Territory.
Information gleaned from JTWC's warnings was used as a supplement for
times when it was impossible to obtain Australian bulletins and for
comparison purposes. References to sustained winds should be under-
stood as being based on a 10-min averaging period unless otherwise
noted.
Northwest Australia/Southeast Indian Ocean
Tropical Activity for October
------------------------------------------
The first tropical cyclone of the 2001-2002 season in the Australian
Region formed during the last week of October a few hundred miles
northwest of Cocos Island. Named Alex by the Perth TCWC, the cyclone
moved westward across longitude 90E into the Southwest Indian Ocean
basin where it was renamed Andre by Mauritius. A little explanation
might be useful here regarding the use of the term "severe". Alex was
referred to as "Tropical Cyclone Alex" east of 90E, but became "Severe
Tropical Storm Andre" upon entering the Southwest Indian basin,
although the reported intensity remained about the same. In the
Australian Region, a "severe tropical cyclone" is one in which maximum
10-min mean winds exceed 64 kts, i.e., a cyclone of hurricane
intensity. But west of 90E a "severe tropical storm" is a system with
10-min average winds in the range of 48-63 kts. More information on
the particular terminology used by the various TCWCs can be found in
the summary for April, 2001 (Feature of the Month section).
Tropical Cyclone Alex-Andre (MFR #2 / TC-02S)
24 - 31 October
-----------------------------------------------
A. Storm Origins
----------------
At 1000 UTC on 24 October JTWC issued a STWO which mentioned that an
area of convection that had developed earlier was located in the South
Indian Ocean southwest of Sumatra or a few hundred miles north of Cocos
Island. Persistent deep convection was associated with a broad,
poorly-organized LLCC. A 200-mb analysis indicated that the region was
beneath weak northerly winds associated with an extension of an upper-
level ridge. At 1000 UTC on the 25th JTWC relocated the disturbance
farther to the west and upgraded the development potential to fair.
Animated infrared and visible satellite imagery revealed a well-defined
LLCC with increasing organization of deep convection. A SSM/I pass had
indicated that the primary convection was situated along the southern
periphery of the LLCC.
JTWC issued a TCFA at 25/1600 UTC, upgrading the potential for
development to good. Maximum winds were estimated at 20 to 30 kts.
At 0300 UTC on 26 October the Perth TCWC issued a gale warning for
the LOW in anticipation of further development. At 0600 UTC the system
was upgraded to Tropical Cyclone Alex, located about 300 nm northwest
of Cocos Island. Also at 0600 UTC, JTWC issued their first warning
on the system, estimating the MSW to be 35 kts. Perth's warning
estimated the peak winds to be 30-45 kts (10-min avg). Alex displayed
a well-developed LLCC with deep convection wrapping into the center of
the cloud system. The cyclone was situated in a weakness between a
mid-level HIGH to the northwest and a stronger ridge to the east-
southeast.
B. Track and Intensity History
------------------------------
After being upgraded to tropical cyclone status, Alex moved slowly
westward. Upper-level northeasterlies continued to shear the system,
hampering the intensification process. By 1800 UTC on 27 October deep
convection had become better organized with both JTWC and Perth
estimating the intensity at 50 kts. Alex continued to be steered west-
ward to west-southwestward by a mid-level ridge situated to the south-
east. At 27/1800 UTC the cyclone was located about 525 nm north-
west of Cocos Island and just east of the 90th meridian. By 0000 UTC
on the 28th Alex had entered the Southwest Indian Ocean basin and had
been renamed Andre by Mauritius. Alex-Andre was near its peak
intensity at this time with the MSW as reported by both JTWC and MFR
being 55 kts (1-min and 10-min averages, respectively). A 10-min avg
wind of 55 kts would equate to a 1-min avg of 65 kts, and the JTWC
warnings on 28 October noted that there were some CI estimates of
65 kts received. Severe Tropical Storm Andre (by MFR's terminology)
tracked slowly to the southwest on the 28th with some evidence of
shearing evident by 1800 UTC, the system being located in a region of
moderate northeastly shear equatorward of the subtropical ridge.
Andre's track became west-southwesterly and later westerly on
29 October. Convection seemed to increase early in the day, but by
1800 UTC the deep convection had been sheared to the west of the LLCC
and had decreased in coverage. MFR and JTWC lowered the MSW estimates
to 35 and 45 kts, respectively, at 1800 UTC. JTWC's 29/0600 UTC
warning had forecast slow intensification, but the 1800 UTC warning
called for no strengthening with weakening after 36 hours. The shear
continued unabated on 30 October and Andre continued to slowly weaken.
By 1800 UCT, MFR and JTWC had lowered their respective MSW estimates
to 30 and 35 kts. The storm at this time was located roughly 600 nm
east-northeast of Diego Garcia.
Andre's center was apparently quite difficult to pinpoint on 30 and
31 October as there were quite a bit of discrepancies between MFR's and
JTWC's coordinates. The best estimate is that the storm halted its
westward motion and jogged back to the east-northeast late on the 30th
before embarking on a southwesterly track once more early on the 31st.
The JTWC warning issued at 31/0000 UTC notes that the LLCC was embedded
in a larger, broad circulation and was difficult to locate. By 1800
UTC on 31 October, Andre's LLCC had broadened and become disorganized.
Therefore, both MFR and JTWC issued their final warnings on the system
at that hour, placing the dissipating center approximately 400 nm
east-southeast of Diego Garcia. A weak remnant LOW remained in the
area for a couple of days but showed no signs or regeneration.
C. Comparisons between Perth/MFR and JTWC
-----------------------------------------
Intensity estimates basically were in good agreement between the
official Southern Hemisphere warning centres and JTWC. Over the past
few years that I have been writing these summaries, I have noticed a
persistent upward bias in Perth's reported 10-min avg MSW estimates
as compared with JTWC's, and this was the case for Tropical Cyclone
Alex. However, for the time of peak intensity when the cyclone crossed
90E, the values from Perth and La Reunion were in excellent agreement.
JTWC's equivalent 1-min avg MSW was close, but represented a slightly
weaker storm than that estimated by the Southern Hemisphere centres.
But, as noted above, JTWC did receive some CI estimates of 65 kts but
chose to be slightly on the conservative end. During Andre's weakening
phase, the intensities reported by JTWC and MFR were in close agree-
ment.
D. Damage and Casualties
------------------------
No reports of damage or casualties resulting from Tropical Cyclone
Alex-Andre have been received.
***********************************************************************
NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E
Activity for October: 1 tropical LOW
Northeast Australia/Coral Sea
Tropical Activity for October
-----------------------------
There were no tropical cyclones or well-organized tropical LOWS in
the Gulf of Carpentaria or Coral Sea during October, but there was
one system which deserves a brief mention. The equatorial westerly
wind burst around mid-month which produced Super Typhoon Podul in the
North Pacific helped to spawn a weak "twin" south of the equator. This
system did not show any significant signs of development until the 25th
when a fairly well-defined LOW center formed near Bougainville. The
TCWC at Port Moresby, Papua New Guinea, issued a gale wind warning for
the 1005-mb LOW, which at 25/1030 UTC was located approximately 60 nm
southwest of Bougainville Island or about 145 nm northeast of Woodlark
Island. Gale-force winds and severe squalls of 34-45 kts were forecast
to occur and persist for the next 6 to 12 hours. The deep convection
associated with this LOW developed against the diurnal trend as an
upper-level trough was crossing Australia. However, the upper-level
trough also eventually brought detrimental vertical wind shear over the
system and it soon weakened. (A special thanks to Jeff Callaghan of
the Brisbane TCWC for forwarding me a copy of the Port Moresby warning
and for providing some information on this system.)
***********************************************************************
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: oct01.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: oct01.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.ph> OR http://66.40.4.61>
http://www.hurricanealley.net/>
http://www.qisfl.net/home/hurricanemike>
http://www.met.fsu.edu/gsc/Docs/Grads/henning/cyclones/>
NOTE: The URL for Michael V. Padua's Typhoon 2000 website has
changed.
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
JTWC now has available on its website the complete Annual Tropical
Cyclone Report (ATCR) for 2000 and a report on the 2000-2001 season in
the Southern Hemisphere. 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 2001 Atlantic and Eastern North Pacific
tropical cyclones; also, preliminary storm reports for all the 2001
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>
Prepared by: Gary Padgett
E-mail: [email protected]
Phone: 334-222-5327 (nights & weekends) / 850-882-2594 (weekdays)
***********************************************************************
***********************************************************************
|
Document: summ0110.htm
Updated: 27th December 2006 |
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