[Index]
Monthly Global Tropical Cyclone Summary November 2002
[Summaries and Track Data] [Prepared by Gary Padgett]
| Tropical
Cyclones
[Index] |
Monthly Global Tropical Cyclone Summary November 2002 [Summaries and Track Data] [Prepared by Gary Padgett] |
MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
NOVEMBER, 2002
(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.)
SPECIAL NOTE: There has been a change in the address of one of the
archival sites where back issues of the monthly summaries and track
files are catalogued. Chris Landsea has moved the files he was
previously archiving on a computer at TPC/NHC to a machine at AOML/HRD.
The address is:
ftp://ftp.aoml.noaa.gov/hrd/pub/landsea/padgett/>
*************************************************************************
NOVEMBER HIGHLIGHTS
--> Northwest Pacific remains quiet--only one tropical cyclone
--> Southwest Indian Ocean season gets underway
--> Two tropical cyclones in Bay of Bengal--one deadly
*************************************************************************
***** Feature of the Month for November *****
ADVANCED OBJECTIVE DVORAK TECHNIQUE
This monthly feature is the third in a series highlighting some of the
papers presented at the recent AMS 25th Conference on Hurricanes and
Tropical Meteorology in San Diego, California. As previously explained,
three of the papers really excited me as they introduced new and
innovative solutions to some of the problematic issues and challenges
facing tropical cyclone forecasters today. The first of these I covered
in the July, 2002, summary--Track Forecasting with a Kilo-member
Ensemble, presented by Jonathan Vigh, a graduate research student at
Colorado State University. The August, 2002, summary featured the
Cyclone Phase Space technique developed by Bob Hart and Jenni Evans
of Pennsylvania State University.
The third and final feature in this series highlights the Advanced
Objective Dvorak Technique (AODT). A paper on this topic was presented
at the San Diego conference by Tim Olander of the University of
Wisconsin's Cooperative Institute for Meteorological Satellite Studies
(UW-CIMSS), and had been authored by Tim, Chris Velden, also of UW-CIMSS,
and Mike Turk of the NOAA/NESDIS Satellite Analysis Branch in Washington,
DC. This paper will look at the following topics:
. Introduction to Dvorak satellite analysis
. Operational usage and feedback
. Additions and improvements toward the development of the AODT
. Future plans
A. Introduction to Dvorak Satellite Analysis
--------------------------------------------
A method of utilizing satellite imagery for estimating tropical
cyclone intensity was first developed by Vern Dvorak in the early
1970s, and later expanded and refined in 1984. The Dvorak Technique
(DT) has been the mainstay of tropical cyclone forecasters and
researchers for estimating tropical cyclone intensity for many years.
The DT was more or less "calibrated" with aircraft reconnaissance
measurements of central pressure and estimates of MSW obtained from
missions flown into Atlantic tropical cyclones. As useful as it
is, the DT has some weaknesses also. First of all, as already noted,
it was based upon reconnaissance flights into storms in one basin only,
leaving questions about its validity for accurately estimating cyclone
intensity in other regions since tropical cyclones in each basin often
display unique features and characteristics.
Secondly, the technique depends somewhat upon human interpretation
of convective cloud patterns; hence, it is inherently subjective. For
instance, TPC/NHC routinely utilizes satellite estimates from three
independent agencies, and often all three do not agree on the final
T-number. And lastly, once a final Dvorak rating is assigned to a
cyclone, the matching intensity represents an average MSW for storms
having that particular T-number. For example, it's rather elementary
to even say so, but just because all analysts may agree that a Dvorak
rating of T7.0 best fits a given cyclone, that doesn't mean its MSW is
guaranteed to be exactly 140 kts.
To help ameliorate some of the subjectivity inherent with manual
Dvorak analysis, work was begun years ago to develop a more purely
objective technique. Ray Zehr of Colorado State University did some
work toward this end as far back as the 1980s, and during the 1990s the
current Objective Dvorak Technique (ODT) was developed by Chris Velden
and Tim Olander. More detailed information on the ODT and its develop-
ment can be found at the following URL:
http://cimss.ssec.wisc.edu/tropic/research/products/dvorak/odt.html>
The ODT utilizes many of the rules and guidelines described in the
original, subjective DT, and comparisons between ODT estimates of central
pressure with aircraft reconnaissance measurements have shown that the
ODT performance is commensurate with the operational intensity estimates
obtained using the manual DT methodology. However, there have been
isolated circumstances which have shown that further improvements are
needed to the existing ODT in order to improve its accuracy over a wider
variety of situations. This new-and-improved ODT--the Advanced ODT
(AODT)--is based upon significant feedback from the ODT user community
and ongoing advances in satellite remote sensing strategies.
B. Operational Usage and Feedback
---------------------------------
The ODT has been utilized as a guidance tool for several years at many
tropical cyclone warning centers worldwide, including SAB, JTWC, and TAFB
(at TPC). Based upon user feedback, at least two important areas of
concern have been identified. One concerns the accuracy of ODT intensity
estimates for storms outside the North Atlantic and Eastern North Pacific
regions. The ODT was developed and tuned primarily against aircraft
reconnaissance in situ measurements of Atlantic tropical cyclones. Some
calibration was also performed from Northwest Pacific reconnaissance
measurements prior to the mid-1980s, but the corresponding satellite
imagery during that period had inferior spatial and temporal resolution
compared with today's imagery and may not have been sufficient for
precise ODT calibration in that region. Current use and comparisons with
subjective DT estimates have generally shown that the ODT provides
slightly stronger MSW estimates in the Northwest Pacific, but without
aircraft reconnaissance in this region, it is difficult to verify whether
the ODT estimates are an improvement or not. The same situation is true
for other tropical cyclone basins.
The other weakness of the current ODT noted by users is the occasional
premature triggering of the "rapid intensification" flag. Built-in
constraints to the standard DT often break down when a tropical cyclone
is undergoing rapid intensification (RI), so a feature was incorporated
into the ODT to accommodate rapidly intensifying cyclones. The RI option
adjusted the time averaging scheme when rapid cyclone deepening was
suggested, and is triggered when two environmental eyewall temperature
threshold values are exceeded. These threshold values were determined
empirically from a limited set of satellite images during Atlantic
RI events. Due to inherent differences between Atlantic and Northwest
Pacific tropical cyclones and the small number of cases used to define
the eyewall cloud temperature thresholds, it is suspected that the RI
flag triggers too often in Pacific storms, leading to significant
intensity overestimation in certain cases.
C. Additions and Improvements Toward the Development of the AODT
----------------------------------------------------------------
One primary focus of current research is to expand the ODT to include
intensity estimates of storms of less than hurricane strength, i.e.,
tropical storms and depressions. The previous technique used temperature
values only to estimate intensity--the eye temperature being the warmest
value within 40 km of the center and the cloud region temperature the
coldest temperature on the warmest ring (28-132 km). The new AODT has
introduced a scene identification scheme similar to that defined in the
original DT in order to better estimate cyclone intensity and especially
that of weaker systems. Five eye classifications have been defined:
clear eye, pinhole eye, large eye ( > than approximately 60-70 km in
diameter), ragged eye, and obscured eye (as well as no eye). Five cloud
scene categories have also been introduced/redefined: uniform CDO,
embedded center, irregular CDO, curved band, and shear pattern. The
curved band and shear pattern identification routines allow for
estimation of intensity at and below tropical storm strength while the
irregular CDO pattern covers transition scenes between TD/TS and
hurricane intensities.
Some supplementary DT rules have been incorporated with the intro-
duction of the new scene type classifications. One such rule limits
the change of intensity estimates over various time periods: Rule 8
within the original Dvorak technique. This addition will reduce large,
unrealistic intensity changes observed with the AODT during certain
scene transitions, and will guide the AODT intensity estimates to those
observed with the traditional Dvorak technique estimates. Commensurate
with this change, the time averaging scheme is now a 6-hour weighted
average.
Additional statistical analyses of the eye and surrounding cloud
region temperature histograms have also been introduced to enhance the
existing Fourier Transform analysis. The eye region analysis and
surrounding cloud region analysis now focus on the spread and symmetry
of temperature measurements, i.e., mean temperatures, rather than simply
the "coldest-warmest" temperature values used in the previous version.
More emphasis is also being placed on the organization and coverage of
the convective cloud region in relation to the storm center. These
new scene classifications lead to improved scene identification
methodologies, which in turn should lead to more accurate intensity
estimates over a wider range of tropical cyclone strengths.
Several upgrades to the AODT have been incorporated in response to
user feedback. First, the curved band analysis routine has been adjusted
to examine different convective cloud features in order to obtain more
accurate intensity estimates. An enhancement to the curved band analysis
routine has also been added to determine the storm intensity at the user-
selected storm center, and to also search for the storm center location
where the maximum intensity estimate is found within the scene. Finally,
the ability of the AODT to run in a totally automated mode has been
requested to help alleviate the time constraints of forecasters when
operating the AODT, and to help further reduce/eliminate the subjectivity
inherent to tropical cyclone center location determination.
An important modification is the removal of the RI flag. This
removal was in response to user feedback and determination that the
new AODT code sufficiently handles the analysis of such storms due to
the addition/modification of various rules since the original ODT was
independently analyzed at the various operational tropical cyclone
forecasting centers.
An additional upgrade regarding the AODT algorithm involves the actual
programming code. This is being done to make the AODT available to users
beyond those with a McIDAS computing environment. This transition has
been successfully demonstrated operationally with the integration of the
new code into the Navy TeraScan system for use at JTWC, and with inte-
gration currently underway within the SIDAS at the Air Force Weather
Agency and the N-AWIPS at TAFB. Also, an X-Windows/Motif version of
the AODT is under development and will be available for UNIX and LINUX-
based systems. This feature of the AODT significantly increases the
size of the algorithm library, but allows for easier implementation of
a platform-independent version.
D. Future Plans
---------------
Some features planned for future versions of the AODT include:
(1) Exploration of additional infrared analysis techniques, such as
removal of diurnal cloud temperature oscillations
(2) Examination of additional geostationary satellite channels such as
the water vapor channel and visible and shortwave infrared imagery
(3) Integration of additional satellite information such as AMSU analysis
and microwave imagery (TRMM, SSM/I) from polar-orbiting satellites
The ultimate goal is to develop an advanced, expert system which
fuses together unique observations from several different satellite-based
platforms.
E. Acknowledgements
-------------------
I would like to thank Chris Velden for giving me permission to feature
the AODT, and also Tim Olander for sending me a copy of the Powerpoint
slides he used in his briefing in San Diego. The slides can be viewed
at the following URL:
http://cimss.ssec.wisc.edu/tropic/aodt/ams2002.ppt>
This feature was taken from the abstract included in the manual
distributed to attendees of the 25th AMS Conference on Hurricanes and
Tropical Meteorology along with more recent information obtained from
Tim Olander and Chris Velden. The entire paper was reviewed by Chris
and Tim, and portions of the text were added by them. Anyone who
wishes may contact Tim and Chris by e-mail at the following addresses:
Chris Velden: [email protected]
Tim Olander: [email protected]
*************************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for November: No tropical cyclones
Atlantic Tropical Activity for November
---------------------------------------
In contrast to November of 2001 when a record three hurricanes formed
in the Atlantic basin, the month of November, 2002, was devoid of any
tropical or subtropical cyclone activity. A broad, non-tropical low-
pressure system formed well over 1000 nm east-southeast of Bermuda on
11 November and moved west-northwestward for a couple of days, generating
gale-force winds mainly north of the center. The STWOs from TPC/NHC
on the 11th and 12th indicated that there was a possibility for some
slow development, but this never materialized. About a week later
another disturbance formed several hundred miles northeast of Puerto
Rico as the result of a broad surface trough interacting with an upper-
level LOW, but again, no tropical or subtropical cyclone development
occurred.
*************************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for November: 1 tropical depression
Sources of Information
----------------------
Most of the information presented below was obtained from the
various tropical cyclone products issued by the Tropical Prediction
Center/National Hurricane Center (TPC/NHC) in Miami, Florida (or the
Central Pacific Hurricane Center (CPHC) in Honolulu, Hawaii, for
locations west of longitude 140W): discussions, public advisories,
forecast/advisories, tropical weather outlooks, special tropical
disturbance statements, etc. Some additional information may have
been gleaned from the monthly summaries prepared by the hurricane
specialists and available on TPC/NHC's website. All references to
sustained winds imply a 1-minute averaging period unless otherwise
noted.
Northeast Pacific Tropical Activity for November
------------------------------------------------
No named tropical storms or hurricanes developed in the Northeast
Pacific basin during November. Hurricane Huko, which had formed late in
October in the Central Pacific, was active in the extreme western part of
the basin before crossing the International Dateline on 3 November to
become a typhoon. As the month opened a broad zone of disturbed weather
extended from the coast of Central America westward for several hundred
miles. A large tropical disturbance slowly took shape and posed a
potential for developing into a tropical depression, but the broad center
moved inland on the 3rd east of Manzanillo. However, heavy rainfall and
gusty winds affected portions of Mexico from the Gulf of Tehuantepec to
Cabo Corrientes and extending well inland.
Several days later another tropical disturbance appeared several
hundred miles southeast of Acapulco and migrated westward. By the 14th
convection had become sufficiently organized that advisories were begun
on Tropical Depression 16E. The depression was centered about 475 nm
south of Cabo San Lucas at 14/0000 UTC, and over the next couple of days
moved on a slow, generally westward track. Strong upper-level south-
westerlies created hostile shearing conditions over the depression, and
after reaching a peak intensity of 30 kts, the system began to weaken.
The final advisory on TD-16E was issued at 0000 UTC on 16 November and
placed the convection-free center about 600 nm south-southwest of Cabo
San Lucas. The discussion bulletin noted that shear over the LLCC was
on the order of 70-80 kts.
*************************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for November: 1 typhoon
Sources of Information
----------------------
Most of the information presented below is based upon tropical
cyclone warnings and significant tropical weather outlooks issued
by the Joint Typhoon Warning Center of the U. S. Air Force and
Navy (JTWC), located at Pearl Harbor, Hawaii. In the companion
tropical cyclone tracks file, I normally annotate track coordinates
from some of the various Asian warning centers when their center
positions differ from JTWC's by usually 40-50 nm or more. All
references to sustained winds imply a 1-minute averaging period
unless otherwise noted.
Michael V. Padua of Naga City in the Philippines, owner of the
Typhoon 2000 website, normally sends me cyclone tracks based upon
warnings issued by the Japanese Meteorological Agency (JMA) and the
Philippines' Atmospheric, Geophysical & Astronomical Services
Administration (PAGASA). Also, Huang Chunliang of Fuzhou City, China,
sends me each month tracks obtained from warnings issued by the
National Meteorological Center of China (NMCC), the Central Weather
Bureau of Taiwan (CWBT) and the Hong Kong Observatory (HKO). A very
special thanks to Michael and Chunliang for the assistance they so
reliably provide.
In the title line for each storm I have referenced all the cyclone
names/numbers I have available: JTWC's depression number, the
JMA-assigned name (if any), JMA's tropical storm numeric designator,
and PAGASA's name for systems forming in or passing through their
area of warning responsibility.
Northwest Pacific Tropical Activity for October
-----------------------------------------------
On 3 November Central Pacific Hurricane Huko crossed the International
Dateline, moving west-northwestward in the direction of Wake Island. The
typhoon subsequently passed just north of the island, later recurving on
a fairly smooth parabolic track and heading eastward back toward the
Dateline. The complete report on Hurricane/Typhoon Huko can be found in
the October summary.
The only other tropical system to be warned on by any of the Northwest
Pacific warning centers was Typhoon Haishen. This cyclone formed south-
east of Guam and moved westward, passing south of the island as it
reached tropical storm intensity. Haishen later strengthened into a
typhoon of moderate intensity and recurved several hundred miles west of
the Marianas Islands.
TYPHOON HAISHEN
(TC-30W / TY 0225)
20 - 27 November
--------------------------------------
Haishen: contributed by China, is the Chinese 'God of the Sea' to whom
sailors and fishermen would offer sacrifices for safe voyages
before they set sail or when they encountered stormy weather
A. Storm Origins
----------------
On 18 November an area of convection developed approximately 200 nm
southwest of Chuuk. Animated visible imagery indicated disorganized
cycling deep convection embedded in a monsoon trough. An 18/2144 UTC
SSM/I pass depicted scattered convection along the periphery of a broad
circulation with no central deep convection. A 200-mb analysis indicated
that the disturbance lay within a region of good diffluence and weak
vertical shear. By 19/0600 UTC the initial disturbance had dissipated
but a new area of convection had formed approximately 210 nm northeast
of Chuuk. Animated visible imagery suggested the presence of a large
mid-level circulation while a 200-mb analysis indicated that the system
was located beneath the axis of a near-equatorial ridge situated to its
east. Vertical shear was weak and upper-level divergence good with both
poleward and equatorward outflow channels.
At 19/2000 UTC the disturbance was located about 340 nm southeast of
Guam. There was some cycling deep convection associated with the LLCC,
so the development potential was upgraded to fair. A TCFA was issued
at 0200 UTC on the 20th due to increasing deep convection over the past
few hours. Visible satellite imagery suggested a broad circulation with
multiple LLCCs present; maximum winds were estimated at 20-25 kts.
Earlier, at 20/0000 UTC, JMA had classified the system as a 25-kt (10-min
avg) tropical depression. JTWC issued their first warning on Tropical
Depression 30W at 0600 UTC. The center was located approximately 225 nm
southeast of Guam, moving westward at a rather rapid 22 kts. By 1200
UTC TD-30W was already passing about 135 nm due south of Guam, racing
westward at 25 kts. The MSW was upped to 30 kts based on CI estimates
of 25 kts and recent QuikScat data. At 1800 UTC the forward pace had
slowed a bit to 17 kts as JMA upgraded the depression to 35-kt Tropical
Storm Haishen. NMCC followed suit and upgraded Haishen to tropical
storm status at 0000 UTC on 21 November.
B. Track and Intensity History
------------------------------
JTWC upgraded Haishen to tropical storm status at 21/0600 UTC when
the center was located approximately 200 nm northeast of Yap. Haishen
was still moving west-northwestward rather quickly at 17 kts as it was
steered by a low to mid-level ridge to the north. This motion continued
throughout the 21st--by 1800 UTC Haishen was centered about 420 nm west
of Guam. Deep convection had continued to increase near the LLCC and
satellite CI estimates had reached 45 kts, which was JTWC's 1800 UTC
warning intensity. (JMA and NMCC were both estimating the 10-min avg
MSW at 50 kts at 1800 UTC.) JTWC increased the MSW to 55 kts at 0000
UTC on the 22nd and to 60 kts at 0600 UTC. Haishen continued to
consolidate, developing good poleward outflow and tightly-curved banding
features. JTWC upgraded the storm to typhoon status at 1200 UTC when
it was centered approximately 575 nm west-northwest of Guam, or about
620 nm south-southwest of Iwo Jima. A 60-nm diameter CDO had developed,
and enhanced infrared imagery around 1800 UTC depicted a banding eye
feature. Haishen's track had turned gradually toward the north as an
approaching mid-latitude trough created a weakness in the subtropical
ridge which had been guiding the storm.
Typhoon Haishen continued tracking northward during the 23rd, turning
toward the north-northeast by 1800 UTC. The storm continued to intensify
as it moved northward with outflow being aided somewhat by contact with
the westerlies. JMA and NMCC upgraded Haishen to typhoon status at 0600
UTC, and JMA upped the MSW (10-min avg) to their peak estimate of 75 kts
six hours later. JTWC estimated the peak MSW at 95 kts at 1800 UTC
and at 24/0000 UTC, based on CI estimates of 102 kts. SSM/I data
indicated that Haishen had a small 14-nm diameter eye. The minimum CP
estimated by JMA was 960 mb, and gales extended outward from the center
150 nm in most quadrants while the radius of storm-force winds was
estimated at 45 nm. At 23/1800 UTC the eye of Typhoon Haishen was
centered approximately 345 nm southwest of Iwo Jima, tracking north-
northeastward at 13 kts.
By 24/0000 UTC Haishen was beginning to show signs of impending extra-
tropical transition: the eyewall had begun to erode and vertical shear
was increasing. By 0600 UTC the eyewall had collapsed and JTWC and
JMA lowered their respective MSW estimates to 85 kts and 70 kts. NMCC,
interestingly, raised their 10-min avg MSW estimate to the peak of 70 kts
at 0600 UTC, possibly to account for the storm's rapid north-
northeastward motion at 30 kts. JTWC issued their final warning on
Typhoon Haishen at 24/1800 UTC with the storm located 265 nm north-
northeast of Iwo Jima and moving northeastward at 27 kts. Convection
had weakened and the LLCC had become involved with a cold front. JMA
classified Haishen as extratropical six hours later, and the system
continued to race off to the northeast, gradually turning eastward. By
27/0600 UTC Haishen's remnants consisted of a 40-kt gale located a few
hundred miles northeast of Midway Island.
C. Meteorological Observations
------------------------------
Roger Edson reported from Guam that he experienced wind gusts to
40 kts as a large outer rainband of Haishen rolled over the island.
Huang Chunliang sent me some observations from the island of Chichi
Jima (WMO 47971) which he'd gleaned from JMA's website. The station
recorded a peak sustained wind of 38 kts at 24/1200 UTC with the minimum
SLP of 970.8 mb measured at 1300 UTC. The station's peak gust of 70 kts
was recorded at 1150 UTC. Ships DEFA and WNRD recorded winds of 58 kts
and 38 kts, respectively, as they encountered Haishen's extratropical
remnants on the 26th.
D. Damage and Casualties
------------------------
No reports of damage or casualties resulting from Typhoon Haishen
have been received.
(Report written by Gary Padgett)
*************************************************************************
NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea
Activity for November: 1 tropical cyclone of gale intensity
1 tropical cyclone of storm intensity
** - not classified as a tropical depression by JTWC
Sources of Information
----------------------
Most of the information presented below is based upon tropical
cyclone warnings and significant tropical weather outlooks issued
by the Joint Typhoon Warning Center of the U. S. Air Force and
Navy (JTWC), located at Pearl Harbor, Hawaii. Occasionally some
information may be gleaned from the daily tropical weather outlooks
and other bulletins issued by the Indian Meteorological Department
(IMD), which is the World Meteorological Organization's Regional
Specialised Meteorological Centre (RSMC) for the basin.
The reported maximum sustained winds (MSW) are based on a 1-minute
averaging period, which is used by all U. S. civilian and military
weather services for tropical cyclone warnings. For synoptic
observations in the North Indian Ocean region, both 10-minute and
3-minute average winds are employed, but IMD makes no attempt to
modify the Dvorak scale for estimating tropical cyclone intensity;
hence, a 1-minute average MSW is implied. In the North Indian Ocean
basin JTWC usually does not initiate warnings until a system has
become well-organized and likely to attain tropical storm status
within 48 hours.
The reports on Tropical Cyclones 03B and 04B were written by John
Wallace--a special thanks to John for his assistance.
North Indian Ocean Tropical Activity for November
-------------------------------------------------
Two tropical cyclones formed in the Bay of Bengal during November.
One did not intensify very much above minimal gale force and remained
well out in the Bay. The other one, however, after loitering off the
East Coast of India as a weak cyclone, suddenly intensified and
spurted northeastward, making landfall in India's West Bengal State
near Calcutta before sweeping on into Bangladesh. Several dozen
fishermen were known to have drowned as the storm caught them unawares,
and several hundred more were reported missing. The cyclone also
caused significant onshore damage in Bangladesh.
TROPICAL CYCLONE
(TC-03B)
10 - 12 November
------------------------------------
Tropical Cyclone 03B was first noted in an IMD bulletin at 0600 UTC
on 10 November when it was located 145 nm east-southeast of Chennai
(Madras), India. The depression tracked steadily northeastward and
intensified to gale force at 1200 UTC on 11 November when it was
centered approximately 465 nm south-southwest of Calcutta. It was at
this time that the JTWC issued their first warning on TC-03B.
The cyclone's intensity changed little until the 12th, when it
accelerated to the northeast, reaching its estimated peak 1-min avg MSW
of 55 kts at 0600 UTC when located 120 nm south-southwest of Calcutta.
Use of the JTWC's MSW/CP relationship for NWP storms, first developed
by Atkinson and Holliday (1977) yields an equivalent CP of 984 mb for
a 55-kt system. (For better or worse, the JTWC has generally applied
the same Atkinson and Holliday estimates to both NIO and NWP storms.)
Warnings from the RMC Calcutta at 0530 UTC, however, indicated lower
winds of about 30-40 kts, with a central pressure of 990 mb. It is
not known if the discrepancy is due to different averaging periods
or to different data sources; therefore, TC-03B's true peak intensity
remains uncertain. (Editor's Note: At its peak this system was
classified as a "severe cyclonic storm" by IMD, implying peak winds
in the 48-63 kt range.)
Tropical Cyclone 03B made landfall near Sagar Island soon after its
peak, at 0900 UTC on 12 November. It weakened quickly once inland, and
the final warning was issued on the remnant depression at 1200 UTC on
the 12th when it was centered about 110 km northeast of Calcutta.
Press reports indicate significant loss of life occurred with this
cyclone, mostly fishermen lost at sea. At least 49 fishermen were
drowned, and various reports listed anywhere from 111 to 560 missing.
According to one source, the number of persons missing is difficult
to assess since sometimes people return alive from the sea three to
four weeks after a cyclone's passage. The Fisheries Minister for
West Bengal State reported that nine trawlers sank off the Digha coast
and only 66 fishermen survived. A report dated 15 November indicated
that at least 47 fishing vessels were unaccounted for.
In Bangladesh 170 fishermen were missing after the cyclone lashed
that country's southern coast, destroying fishing villages and rice
farms. Winds smashed bamboo huts, uprooted trees, and disrupted road
travel between towns and villages along the Bay of Bengal coast. The
capital city of Dhaka was inundated with heavy rains which flooded
city streets, shutting down electrical power and forcing public
transportation to cease operation. The heavy rains also wiped out
winter rice and vegetable crops.
More information about this cyclone's effects can be found at the
following website:
http://www.reliefweb.int/w/rwb.nsf/vLND
(Report written by John Wallace with additions by Gary Padgett)
TROPICAL CYCLONE
(TC-04B)
23 - 28 November
------------------------------------
The LOW that became Tropical Cyclone 04B was first noted in an IMD
bulletin at 0300 UTC on 23 November when it was located about 440 nm
east-southeast of Chennai (Madras), India. The JTWC issued its first
warning on TC-04B at 1200 UTC on the 23rd, placing the center about
510 nm east of Chennai and tracking slowly northward.
Tropical Cyclone 04B peaked at 1800 UTC on 23 November with a MSW of
45 kts and an estimated CP of 991 mb when it was centered 500 nm east
of Chennai. The cyclone weakened on the 24th as it tracked to the
north, and thereafter maintained only minimal tropical storm strength.
Late on the 24th, TC-04B turned northwestward, and was relocated to the
south on the 25th as the poorly-organized system became more difficult
to track. By now its slow track was roughly westward, and the JTWC
issued their final warning on TC-04B at 1200 UTC on the 25th, even
though the cyclone was still generating significant convection. The
likely reason for the pre-emptive move was an expectation that the
cyclone would soon dissipate. The IMD continued issuing warnings,
however, as the minimal storm turned northward again late on the 25th,
then due east on the 26th. Tropical Cyclone 04B weakened to depression
strength on the 27th, and its eastward track faltered to a near stall.
The final advisory on the dissipating system was issued by the IMD at
0300 UTC on 28 November when it was located about 270 nm west of Yangon
(Rangoon), Myanmar.
No casualties or damages are known to have resulted from TC-04B.
(Note: The CP estimate was based on the Atkinson and Holliday (1977)
table. See report on TC-03B for more information.)
(Report written by John Wallace)
*************************************************************************
SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E
Activity for November: 1 moderate tropical storm **
1 tropical cyclone (hurricane)
** - system was not operationally classified as a tropical storm by MFR
(although it was by JTWC)
Sources of Information
----------------------
The primary sources of tracking and intensity information for
Southwest Indian Ocean tropical cyclones are the warnings issued by
the Tropical Cyclone Warning Centre on La Reunion Island, part of
Meteo France (MFR), and the Regional Specialised Meteorological Centre
for the basin. However, tropical cyclones in this region are named
by the sub-regional warning centres on Mauritius and Madagascar with
longitude 55E being the demarcation line between their respective
areas of warning responsibility. The La Reunion centre only advises
these agencies regarding the intensity of tropical systems. References
to sustained winds imply a 10-minute averaging period unless otherwise
stated.
In the companion tropical cyclone tracks file, I occasionally
annotate positions from warnings issued by the Joint Typhoon Warning
Center (JTWC) of the U. S. Air Force and Navy, located at Pearl
Harbor, Hawaii, when they differ from MFR's coordinates by usually
40-50 nm or more. The JTWC warnings are also the source of the
1-minute average maximum sustained wind values included in the
tracks file. Additionally, information describing details of
satellite imagery and atmospheric circulation features included in
the narratives is often gleaned from the JTWC warnings.
Southwest Indian Ocean Tropical Activity for November
-----------------------------------------------------
Two tropical systems were named in the Southwest Indian basin during
November. Atang was never classified as a tropical storm by MFR or
Mauritius (although it was by JTWC), but was named by Mauritius none-
theless since it posed a threat to the island of Agalega. Atang was
a very tenacious system--twice JTWC dropped warnings but had to revive
them as the system re-intensified. Atang eventually crossed the northern
tip of Madagascar and made landfall in southern Tanzania. There was
an unofficial report of 40-kt winds in Tanzania which suggests that the
system was possibly a tropical storm when it made landfall.
The second storm, Boura, formed east-southeast of Diego Garcia and
moved west-southwestward across the Southwest Indian for several days.
Boura reached minimal tropical cyclone (i.e., hurricane) intensity on
18 November. JTWC, however, estimated Boura's winds at hurricane
intensity (1-min avg) for three days from the 17th to the 20th.
TROPICAL STORM ATANG
(MFR-02 / TC-02S)
4 - 13 November
----------------------------------------
Atang: contributed by Botswana
A. Storm Origins
----------------
A STWO issued by JTWC on 3 November noted that an area of convection
about 90 nm west-northwest of Diego Garcia had persisted for at least
twelve hours. Animated multi-spectral and microwave imagery revealed
the presence of cycling deep convection over a broad LLCC while a 200-mb
analysis indicated weak vertical shear and moderate diffluence over the
region. The development potential was upgraded to fair at 1800 UTC as
convection continued to organize near the center. The system continued
moving westward--by 2100 UTC it was located about 290 nm west of Diego
Garcia. A 03/1722 UTC SSM/I image had indicated increased organization
in the mid-levels with an improved banding feature wrapping around the
LLCC. The disturbance was located in a favorable environment beneath
a ridge axis, so a TCFA was issued by JTWC. The MSW (1-min avg) was
estimated at 25-30 kts.
MFR initiated tropical disturbance bulletins at 04/1200 UTC, numbering
it as Tropical Disturbance 02. The center was then located approximately
400 nm north-northeast of Agalega. The LLCC appeared to be slightly
weaker on the 4th, although there was still organized deep convection.
JTWC issued a second TCFA at 2100 UTC as the system continued moving
westward at 13 kts. By 1800 UTC on the 5th the disturbance had reached
a point approximately 700 nm east-northeast of Madagascar. Little change
in structure had been noted, but vertical shear remained weak.
At 06/0000 UTC, MFR upgraded the disturbance to tropical depression
status, i.e., a MSW of 30 kts, and at 0600 UTC, JTWC issued their first
warning on TC-02S, estimating the 1-min avg MSW at 35 kts. The system
was moving southwestward at 4 kts, and animated visible imagery indicated
improving outflow aloft. By 1200 UTC the depression had reached a point
approximately 105 nm north-northeast of Agalega. Even though it was not
considered a tropical storm by the Southern Hemisphere warning centres at
this juncture, the Meteorological Service of Mauritius named it Atang in
order to stress the potential threat it posed to the island of Agalega.
B. Track and Intensity History
------------------------------
JTWC upped the MSW (1-min avg) to 45 kts at 1800 UTC based on CI
estimates of 45 and 55 kts. MFR and Mauritius, however, never estimated
the MSW (10-min avg) any higher than 30 kts. Atang at this time still
remained underneath an upper-level ridge axis and appeared to be slowly
intensifying. However, by 17/0600 UTC the system appeared to be weaker.
Animated satellite imagery indicated considerable weakening of the
convection and low-level cloud lines appeared diffuse and weak. Dvorak
numbers were also decreasing, so JTWC lowered the 1-min MSW to 35 kts.
MFR reduced the intensity to 25 kts at 1200 UTC, and at 1800 UTC JTWC
issued the first of three "final" warnings on Atang. The system was then
located approximately 380 nm northeast of Madagascar or about 165 nm
south-southwest of the Seychelles. Microwave imagery revealed that the
LLCC was embedded in a broad trough with multiple circulations.
Even though Atang's surface circulation weakened, the mid-level
circulation remained intact. In a STWO issued at 1800 UTC on 8 November,
JTWC upgraded the potential for redevelopment to fair. Warnings on
Atang were re-initiated at 0600 UTC on the 9th. The center was placed
about 375 nm north-northwest of Tromelin Island with the MSW (1-min avg)
estimated at 35 kts. A short-lived upper-level LOW had formed northwest
of Madagascar, improving outflow over the depression. MFR had also
discontinued bulletins at 07/1800 UTC, but resumed issuing them at
09/1200 UTC. JTWC maintained the MSW at 35 kts through the 10/0600 UTC
warning. Satellite intensity estimates during this interim period were
in the 25-30 kt range, but QuikScat data indicated 35-kt winds in the
circulation. Atang had moved southwestward, and at 0600 UTC on the 10th
was located just northeast of the coast of Madagascar. Animated visible
imagery indicated that two possible LLCCs had formed as the system
approached land. The next warning at 10/1800 UTC placed Atang's center
approximately 50 nm north of the northern tip of Madagascar, tracking
west-northwestward. The MSW (1-min avg) was lowered to 20 kts and
warnings were discontinued for the second time.
MFR continued to issue sporadic bulletins on Atang but kept the
system at tropical disturbance status, i.e., winds 25 kts or less. A
STWO from JTWC at 0700 UTC on 11 November indicated that the disturbance
once more had a fair potential for redevelopment. Warnings were
started for the third time on this tenacious system at 11/1200 UTC. The
revived Atang was located over the warm waters of the Mozambique Channel
about 250 nm west-northwest of the northern tip of Madagascar. The
system was moving west-southwestward at 12 kts with the MSW (1-min avg)
once more estimated at 35 kts, based on CI estimates of 25, 30 and 35 kts
and an 11/0236 UTC QuikScat pass. Convection had increased near the
LLCC during the previous twelve hours.
A low to mid-level subtropical ridge to the south guided Atang on a
westerly track toward the African coast. The 12/0000 UTC warning noted
that the center was partially-exposed to the east of the deep convection.
The warning intensity was maintained at 35 kts based on CI estimates of
30 and 35 kts and synoptic data. As it neared the coast, Atang took a
northwestward jog toward Tanzania, being located at 1200 UTC about 70 nm
east of the southern Tanzanian coast. The center moved inland around
1800 UTC and by 13/0000 UTC was dissipating about 50 nm inland. The
LLCC had weakened and become decoupled from the remaining mid-level
circulation. The 13/0000 UTC warning from JTWC was the final "final"
warning on Atang.
C. Meteorological Observations
------------------------------
In late November I received an e-mail from Julian Heming of the
UK Meteorological Office. Julian related that a colleague of his had
just returned from Tanzania where he had assisted with the installation
of a forecaster display package for the Tanzanian Meteorological Service.
During the time Julian's colleague was in Tanzania, the remnants of Atang
came ashore over the southern portion of the country. There were reports
of much loss of life (mainly fishermen), extremely heavy rainfall, and a
report from a coastal station of sustained winds of 40 kts, gusting to
80 kts. A visible Meteosat 5 image taken at 0850 UTC on 12 November,
sent to me by Karl Hoarau, depicts a partially-exposed center on the
eastern side the CDO, so an intensity of 35-45 kts isn't out of the
question, based on that image. However, if the 80-kt gust measurement
is accurate, it probably occurred in a big thunderstorm. It should be
noted that this report is unofficial and currently hasn't been verified,
but if it is true, would strongly suggest that Atang was a tropical
storm (10-min avg) at landfall. If any further details are received
regarding this observation, they will be included in a future summary.
D. Damage and Casualties
------------------------
Other than the reference to loss of life in the above paragraph,
I have been unable to locate any further information concerning
damage and/or casualties resulting from Atang.
(Report written by Gary Padgett)
TROPICAL CYCLONE BOURA
(MFR-03 / TC 03S)
15 - 23 November
------------------------------------------
Boura: contributed by the Comoros Islands
A. Storm Origins
----------------
A STWO issued by JTWC at 1800 UTC on 14 November noted that an area of
convection had developed approximately 350 nm east-northeast of Diego
Garcia. Animated visible imagery indicated that a strong westerly wind
burst was moving through the area. A 14/1220 UTC QuikScat pass indicated
troughing along latitude 5S with 20-30 kt winds on both the equatorward
and poleward sides of the trough. A 14/1502 UTC SSM/I pass failed to
show any organization of the deep convection, but an upper-level analysis
indicated excellent divergence with two outflow channels. An interim
STWO was issued at 2300 UTC upgrading the development potential to fair.
The disturbance had moved southward and was then located approximately
315 nm east of Diego Garcia. A mid-level circulation was present and
deep convection was consolidating, and a 14/1809 UTC TRMM pass had
suggested a turning in the lower levels.
B. Track and Intensity History
------------------------------
The first bulletin issued by MFR at 0600 UTC on 15 November directly
upgraded the system to Tropical Storm Boura. Boura was centered about
250 nm east-southeast of Diego Garcia, and MFR estimated the MSW to be
35 kts. JTWC issued a TCFA at 0800 UTC, followed by the first warning
on TC-03S with 35-kt winds at 1200 UTC. Once having upgraded Boura
to tropical storm status, MFR's intensity estimate remained pegged at
35 kts for 48 hours whereas JTWC upped the 1-min avg MSW to 40 kts at
1800 UTC and to 45 kts at 16/1200 UTC. Boura was then located 200 nm
due south of Diego Garcia and moving west-southwestward at 11 kts, being
guided by a low to mid-level ridge to the south-southeast. Some
easterly shearing was still affecting the system and it intensified
slowly on the 16th.
However, by early on 17 November Boura was showing signs of getting
stronger. By 0600 UTC Dvorak estimates were T4.0, and early visible
imagery indicated that the vortex had moved beneath the center of the
deep convection and had developed a CDO. Also, a banding feature was
developing over the southeast quadrant. MFR and JTWC upped the 0600 UTC
intensity estimates to 60 (10-min avg) and 65 (1-min avg) kts,
respectively. An eye appeared to be forming around 17/0600 UTC, but
six hours later had returned to a tightly-curved band feature. A passing
baroclinic disturbance to the south had induced a slightly more south-
westward motion for Boura, and the forward speed had decreased slightly
also. Nonetheless, the storm appeared slightly stronger with CI
estimates reaching 77 kts, so JTWC upped the 1-min avg MSW to 75 kts
at 1800 UTC, and MFR upped the 10-min avg intensity to 65 kts--cyclone
strength--at 18/0000 UTC.
Tropical Cyclone Boura was at its peak intensity of 65 kts (75 kts
from JTWC) early on 18 November when located approximately 500 nm east-
northeast of St. Brandon Island. The minimum CP estimated by MFR was
968 mb. However, as the day wore on, there was evidence of drier
air affecting the eastern section of the cyclone, and some upper-level
northeasterlies also began to impinge on the system. MFR downgraded
Boura to a 60-kt severe tropical storm at 1800 UTC, but JTWC maintained
the 1-min avg MSW at 75 kts through early on the 20th. By 1800 UTC
the slowly-weakening Boura was located about 260 nm northeast of
Mauritius, moving westward at 8 kts. The cyclone apparently made a
slight comeback on the 19th--at least one CI estimate reached 90 kts,
so JTWC left the 1-min avg MSW at 75 kts. MFR, however, did not agree
with this assessment and reduced the 10-min avg MSW to 55 kts at 0600
UTC. The 19/0000 UTC JTWC warning noted that enhanced infrared imagery
indicated increased outflow in the northern semi-circle.
Outflow remained good on 20 November, but CI numbers began to slowly
decrease. JTWC reduced the 1-min avg MSW estimate to 65 kts at 20/1200
UTC with the storm centered about 260 nm north of Mauritius, moving
west-southwestward at 9 kts. MFR lowered the intensity to 50 kts at
1800 UTC as the system continued slowly weakening. Although CI estimates
continued to decrease, JTWC kept Boura at 65 kts on the 21/0000 UTC
warning, but this was reduced to 45 kts at 1200 UTC--MFR was also
reporting 45 kts for the 10-min avg MSW. The storm had weakened
considerably during the previous twelve hours with the center partially-
exposed to the northwest of the remaining deep convection. A low to mid-
level subtropical ridge to the south had caused the weakening Boura to
take a west-northwesterly track. MFR downgraded Boura to tropical
depression status at 22/0000 UTC when the fully-exposed LLCC was located
approximately 165 nm north of Tromelin. Also at 0000 UTC JTWC lowered
the MSW to 35 kts and issued their final warning. Boura continued to
drift west-northwestward as it weakened. MFR issued the final bulletin
on the dissipating system at 1200 UTC on the 23rd, locating the center
about 150 nm east-northeast of the northern tip of Madagascar.
The remnants of Boura did not die easily. On 25 November satellite
imagery revealed a partially-exposed LLCC under the eastern side of a
small CDO one degree in diameter. The remains of Boura had continued
traveling northwestward and were located deep in the tropics several
hundred miles north of Madagascar. Earlier QuikScat data had revealed
winds of 25-30 kts south of the center. No warning center re-initiated
warnings, however, and the LOW gradually weakened. By the 27th the
LLCC was completely-exposed about one degree east of the CDO--still
warranting a Dvorak classification of T1.0/1.5 (this assessment from
Karl Hoarau).
C. Meteorological Observations
------------------------------
Patrick Hoareau made a survey of the JTWC Best Track database for the
Southern Hemisphere (1980-2002) and could find no other cyclone which
reached an intensity of 75 kts (1-min avg MSW) west of longitude 65E
for so early in the season. Tropical Cyclone Boura passed about 70 nm
north-northwest of St. Brandon. A 24-hour rainfall total of 54.5 mm
was measured and the peak gust reached 57 kts. Since a strong gradient
existed between the cyclone and a strong anticyclone to the south,
strong wind gusts were recorded in Mauritius and Reunion Island. In
Mauritius, Le Morne recorded a peak gust of 64 kts while Bain Boeuf
recorded a gust of 51 kts. On Reunion Island, Etang Sale recorded a
top gust of 60 kts. (A thanks to Patrick for passing along this
information.)
D. Damage and Casualties
------------------------
No reports of damage or casualties resulting from Tropical Cyclone
Boura have been received by the author, although wind gusts of the
magnitudes mentioned in the above paragraph would likely have caused
some scattered, minor damage to vegetation and weaker structures.
(Report written by Gary Padgett)
*************************************************************************
NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E
Activity for November: No tropical cyclones
*************************************************************************
NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E
Activity for November: No tropical cyclones
*************************************************************************
SOUTH PACIFIC (SPA) - South Pacific Ocean East of Longitude 160E
Activity for November: 1 tropical depression **
** - system formed at end of month and became minimal tropical cyclone in
early December and will be covered in the December summary
South Pacific Tropical Activity for November
--------------------------------------------
A tropical depression formed north of Fiji late in the month and
moved generally southeastward for the next several days. The system
was well east of the Dateline on 4 December when it strengthened
slightly and became ephemeral Tropical Cyclone Yolande. The report
on Yolande will be included in the December summary.
*************************************************************************
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
from the archive sites listed below. (Note: I do have a limited e-mail
distribution list for the track files. If anyone wishes to receive
these via e-mail, please send me a message.)
Both the summaries and the track files are standard text files
created in DOS editor. Download to disk and use a viewer such as
Notepad or DOS editor to view the files.
The first summary in this series covered the month of October,
1997. Back issues can be obtained from the following websites
(courtesy of Michael Bath, Michael V. Padua, Michael Pitt, and
Chris Landsea):
http://australiasevereweather.com/cyclones/>
http://www.typhoon2000.ph> OR http://64.235.42.210>
http://mpittweather.com>
ftp://ftp.aoml.noaa.gov/hrd/pub/landsea/padgett/>
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 2001 (2000-2001 season for the Southern
Hemisphere). ATCRs for earlier years are available also. Recently
added was the report for the Southern Hemisphere 2001-2002 season.
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>
A special thanks to Michael Bath of McLeans Ridges, New South Wales,
Australia, for assisting me with proofreading the summaries.
PREPARED BY
Gary Padgett
E-mail: [email protected]
Phone: 334-222-5327
John Wallace (Eastern North Pacific, North Indian Ocean, Western
Gulf of Mexico)
E-mail: [email protected]
Kevin Boyle (Eastern Atlantic, Western Northwest Pacific, South
China Sea)
E-mail: [email protected]
Simon Clarke (Northeast Australia/Coral Sea, South Pacific)
E-mail: [email protected]
*************************************************************************
*************************************************************************
|
Document: summ0211.htm
Updated: 27th December 2006 |
[Australian Severe Weather index] [Copyright Notice] [Email Contacts] [Search This Site] |