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Monthly Global Tropical Cyclone Summary April 2002
[Summaries and Track Data] [Prepared by Gary Padgett]

                                 APRIL, 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.)


                             APRIL HIGHLIGHTS
  --> Quiet month--two cyclones in Southeast Indian Ocean


                 ***** Feature of the Month for April *****


     In July of 1999 I was contacted by Patrick Hoareau of Rennes, France,
  who had been reading my monthly tropical cyclone summaries and had col-
  lected many annual tropical cyclone reports from JTWC, Meteo France, and
  perhaps other warning centers.  Patrick had compiled some statistics on
  Southern Hemisphere tropical cyclones, and was interested in forming an
  e-mail group with other interested persons.   At the time I was already
  in contact with several tropical cyclone enthusiasts, including Matthew
  Saxby and Michael Bath in Australia, Michael Padua in the Philippines, 
  and John Wallace, Eric Blake and Michael Pitt here in the United States.
  So we formed an informal e-mail discussion group for the purpose of 
  sharing information, asking questions, exchanging satellite pictures, 
  etc.  The group has grown now to 21 members, including (in addition to
  myself and the ones named above) Carl Smith in Australia, Carl's brother
  Phil in Hong Kong, Jean Marc de Maroussem in Mauritius, Huang Chunliang
  in China, Bruno Benjamin on Guadeloupe, veteran storm chaser and photo-
  grapher Jim Leonard from the Florida Keys, Jim's friend and chase partner
  Mike Theiss, Jose Garcia in Puerto Rico, Karl Hoarau in Paris, Karl's 
  brother Jean Paul on Reunion Island, Jim Edds, another storm chaser and
  photographer from the Keys, and Rich Henning, a member of the USAF
  Reserves' 53rd Weather Reconnaissance Squadron--The Hurricane Hunters.
  Just added a couple days ago was Simon Clarke from Cleveland, Australia.

     When things start stirring in the tropics, e-mail traffic among group
  members picks up also.  Some members contribute only when their primary 
  basin of interest (usually where they live) is active while others 
  actively follow tropical cyclones around the globe.  Several of them
  are prime contributors of information for the summaries and track files
  I prepare each month, and I am very grateful to them for the material
  they send to me.  Most of the members have sent me information at one
  time or another which has found its way into the cyclone summaries, and
  I always try to acknowledge their contributions.  At various times in
  the past, Matthew Saxby and Patrick Hoareau sent me tracks for portions
  of the Southern Hemisphere basins, and Carl Smith undertook for awhile
  to write summaries of the eastern Australian cyclones, but their circum-
  stances changed such that it was not feasible for them to continue doing
  so.  Michael Padua and Huang Chunliang now regularly send me compiled
  tracks and intensities from the various Asian warning centers in the 
  Northwest Pacific basin.  I incorporate some of this information into
  the monthly cyclone track files, a feature which in my opinion adds
  value to the files.  Also, recently, Michael Bath has been assisting me 
  by proofreading some of the individual cyclone narratives.

     In addition to these fellows, many professional meteorologists around
  the world have contributed inputs into the summaries, and continue to do
  so:  Jeff Callaghan from Brisbane; Mark Kersemakers, Lori Chappel, Ross
  Evans, Geoffrey Garden and Peter Bate at Darwin--maybe others there;
  Steve Ready at Wellington; Alipate Waqaicelua at Nadi, Fiji; Philippe
  Caroff at La Reunion; Mark Lander and Roger Edson at the University of
  Guam; David Roth at HPC; Jack Beven and Eric Blake at TPC/NHC; Tony
  Cristaldi of the Melbourne NWS office; Pete Bowyer and Chris Fogarty of
  Environment Canada.  Alipate Waqaicelua, Chief Forecaster at Nadi, has 
  been especially helpful as he regularly writes summaries for internal use 
  of all the named tropical cyclones in Fiji's AOR.  Alipate sends these to 
  me with the permission to use them in my monthly summaries.  Also, over 
  the past year Karl Hoarau has become someone I can rely on to perform 
  special studies of systems which "fell through the warning crack" but 
  which warrant some documentation in the summaries.

     One member of my informal discussion group needs singling out for
  special mention.   John Wallace, a student at the University of Texas
  in San Antonio, has over the years seriously studied tropical cyclones 
  much as I did as a teenager, and has developed a special interest in 
  climatology and patterns of storm formation.  John also has a special
  interest in the storms of the Northeast Pacific basin and the North
  Indian Ocean and has written many of the narratives for cyclones in those
  basins for me since late 1999.  John's assistance was invaluable during
  the very active Northern Hemisphere seasons of 2000 and 2001, during
  which I got very much behind schedule.   Fortunately, John has agreed
  to continue covering the NEP and NIO cyclones this season as time
  permits.  Needless to say, I am very grateful to John for the assis-
  tance he has rendered in the past and for his willingness to continue
  in that capacity, so I have decided to accord him co-author status. 

     No doubt there are others who have contributed information for the
  summaries, or else have answered some of my questions, whose names I 
  can't recall at the moment.   To any such persons, as well as all those
  I've named above, I would like to extend a very special thanks.  And of
  course I'm very grateful to Chris Landsea for asking me to undertake the
  writing of the summaries in the first place.  It has been, and continues
  to be, a very rewarding experience.  Now that I am retired from my full-
  time job and have much more time on my hands, I plan to incorporate some
  new features and formats into the summaries and track files which I hope
  will be perceived as improvements.  But before I change anything I will
  announce it in advance and perhaps solicit some opinions regarding the
  impact of any proposed changes.

     Several of the members of my cyclone chat group have some very nice
  websites, and in next month's summary I plan to include a short descrip-
  tion of those.

                        *** Additional Feature ***

                           NOT QUITE "MED-CANES"

     Most tropical cyclone forecasters, researchers, and enthusiasts
  nowadays are familiar with the cyclonic storm systems which at rather
  infrequent intervals form over the Mediterranean Sea and exhibit satel-
  lite signatures which look very much like tropical cyclones, even to the
  extent of sometimes having very deep convection with cold cloud tops.
  Meteorologists are rather noted for coining names for phenomena which
  don't seem to quite fit the standard classification schemes--e.g.,
  landspout, gustnado, landphoon, neutercane--and some folks have gotten
  into the habit, for better or for worse, of referring to these rare
  Mediterranean cyclones as "med-canes".  Just as there is no officially
  agreed-upon terminology to identify these cyclones, there is no general
  consensus as to how they should be classified meteorologically.  Some
  persons feel that at least some of these storm systems are basically
  operating as tropical cyclones; others argue that they should be clas-
  sified as subtropical cyclones or some sort of hybrid; and there are
  those who feel that they are a warmer-climate cousin of the polar LOWs
  of the far North Atlantic.

     The purpose of this article, however, is not to discuss "med-canes"
  but rather to mention a couple of similar systems which were not located
  in the Mediterranean Sea, but were quite close, and to give some links
  where images of these and similar systems can be viewed.   Back in
  February Julian Heming of the UKMET office sent around an image of a
  small vortex which had formed off the coast of Morocco.  In Julian's
  opinion this was some sort of hybrid system, perhaps similar to the
  Mediterranean cyclones.  An image of this system can be viewed at the
  following website:>

  Paul McCrone, Chief Forecaster at the Headquarters of the Air Force
  Weather Agency (AFWA), also felt that the system was some sort of hybrid.
  Paul has some images of the cyclone archived at the following URL:>

  The system was located not a great distance southwest of the Strait of
  Gibraltar and exhibited a tight swirl of mainly low clouds with an
  eye-like "hole" in the center.  (The date and time of the image sent by
  Julian was 18 February 2002 at 1400 UTC.)

     Julian also sent me an image (no link available) of an interesting
  system he'd noted over the Black Sea on 21 March of this year.  For a
  period of about six hours it seemed to form an eye-like structure before
  filling in again.  Julian stated that the LOW seemed to have a frontal
  structure.  It seems likely to me that perhaps this particular system
  was somewhat analogous to the LOWs which often form over the Great Lakes
  in wintertime and have some characteristics in common with polar LOWs.

     Julian has placed some images of several hybrid or otherwise unusual
  cyclonic systems at the following URL:>

  Included are another similar system off the Moroccan coast, a genuine
  "med-cane" in January, 1995, and the South Atlantic tropical storm (or
  strong depression) in April, 1991, the latter being the only tropical
  cyclone to date known to have formed in the South Atlantic Ocean.
                            ACTIVITY BY BASINS

  ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico

  Activity for April:  No tropical cyclones


  NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180

  Activity for April:  No tropical cyclones


  NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180

  Activity for April:  1 tropical depression

                       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 April

     No named tropical storms formed in the Northwest Pacific basin during
  the month of April.   One tropical depression formed and was tracked by
  JTWC and JMA, being designated as TD-04W by JTWC.   The depression began
  forming northwest of Pohnpei early in the month, and the first warning
  from JTWC at 1800 UTC on 5 April placed the center about 750 nm east of
  the southern Marianas Islands.  The rather large system had already been
  picked up by an approaching trough and was moving rather quickly to the
  north-northeast.  This north-northeastward motion continued, becoming
  more northeasterly and later easterly.   The depression was already in
  the process of extratropical transition by 0600 UTC on the 6th and JTWC
  issued their final warning on the system at 07/0000 UTC, placing the
  weakening center approximately 350 nm west-southwest of Wake Island.  JMA
  continued following the weak, residual LOW through 08/1200 UTC to a
  position near Wake Island.  During the formative stages of this large
  tropical depression, winds gusting to gale force were reported from the
  islands of Chuuk and Nukuoro.


  NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea

  Activity for April:  No tropical cyclones

              North Indian Ocean Tropical Activity for April

     April lies well within the spring transition season when tropical
  cyclones often form in the North Indian Ocean.  No tropical storms or
  well-organized depressions formed in April, 2002, but there was an
  interesting disturbance which warrants mention.   A weak LLCC with some
  associated cycling deep convection formed on 25 April at a very low
  latitude (3.5N) about 350 nm off the east coast of Somalia in the western
  Arabian Sea.   The system's organization continued to improve and at
  25/2200 UTC, JTWC issued a TCFA for the LOW.   Deep convection had con-
  tinued to build near the LLCC and the system presented a fairly well-
  organized appearance in visible satellite imagery.  JTWC estimated the
  maximum winds at 20-25 kts.  The disturbance, however, made landfall at
  approximately 26/1530 UTC in central Somalia just north of the city of
  Hobyo, so the TCFA was cancelled at 26/1900 UTC.


  SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E

  Activity for April:  1 tropical cyclone **

  ** - visitor from the Australian Region (Dianne-Jery)

             Southwest Indian Ocean Tropical Activity for April

     Following a rather active January through March period, no tropical
  storms or cyclones formed in the Southwest Indian Ocean during April.
  The only storm on the charts was Tropical Cyclone Jery, which had formed
  in the Australian Region where it was known as Dianne.   Dianne-Jery
  remained in the eastern extremity of the basin, later moving back east
  of longitude 90E into Perth's AOR once more.  The cyclone reached an
  estimated peak intensity of 80 kts (10-min avg MSW from MFR), falling
  10 kts shy of attaining intense tropical cyclone status.  JTWC, however,
  did estimate the peak intensity at 105 kts (1-min avg MSW) for one
  warning cycle.



  Activity for April:  1 tropical cyclone
                       1 severe tropical cyclone (hurricane)

                        Sources of Information

     The primary sources of tracking and intensity information for
  Northwest Australia/Southeast Indian Ocean tropical cyclones are 
  the warnings and advices issued by the Tropical Cyclone Warning
  Centres at Perth, Western Australia, and Darwin, Northern Territory. 
  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 the Australian centres' coor-
  dinates 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.

     A description of the Australian Cyclone Severity Scale can be found
  on the Australian Bureau of Meteorology's official website:>
     Click on the link 'Cyclone Severity Categories'

  or on Chris Landsea's FAQ on HRD's website:>

  or on Michael Bath's Australian Severe Weather site:>

                 Northwest Australia/Southeast Indian Ocean
                        Tropical Activity for April

     Tropical cyclone activity was non-existent in waters off Northwest
  Australia and in the Southeast Indian Ocean after the demise of Severe
  Tropical Cyclone Chris in early February through the end of March.  A
  tropical LOW formed during the first week of April south of Java and
  had intensified into Tropical Cyclone Dianne very near Cocos Island by
  the 7th.  Dianne moved west-southwestward and had strengthened into a
  severe tropical cyclone (hurricane) by the time it reached longitude 90E
  and moved out of the Australian Region.  Mauritius renamed the cyclone
  Jery, and it became a fairly strong cyclone as it moved southward just
  west of 90E.

     A few days after the formation of Tropical Cyclone Dianne, another LOW
  northwest of Darwin began developing and had intensified into a tropical
  cyclone by the 10th.   The cyclone, named Bonnie by the Darwin TCWC,
  followed a westerly track at a rather low latitude and brushed the
  Indonesian islands of Timor and Sumba.   For several days forecasts
  consistently called for Bonnie to strengthen, but the cyclone never
  intensified above 50 kts and eventually weakened and dissipated southeast
  of Cocos Island.

                        TROPICAL CYCLONE DIANNE-JERY
                             (TC-21S / MFR 13)
                                5 - 13 April

  A. Storm Origins

     A persistent area of deep, unorganized convection developed on 4 April
  approximately 190 nm northeast of Cocos Island.  CIMSS upper-air products
  showed the disturbance to be located in a region of weak to moderate
  vertical shear with fair outflow aloft.   A QuikScat pass around 1800 UTC
  suggested that an associated weak LLCC was embedded in a near-equatorial
  trough situated along latitude 12S.  By 1800 UTC on 5 April the system
  was located about 250 nm northeast of Cocos Island, and animated satel-
  lite imagery depicted an increase in deep convection to the northeast of
  the broad LLCC.  A 05/1100 UTC QuikScat pass had indicated winds of 15 to
  20 kts and a 200-mb analysis revealed improved outflow over the distur-
  bance; therefore, JTWC upgraded the development potential to fair.

     JTWC issued a TCFA at 1100 UTC on the 6th--deep convection was con-
  tinuing to increase near the center and a convective band was developing
  in the southern quadrant.  A 200-mb analysis indicated that the system
  was beneath the subtropical ridge axis in a region of light shear, and a
  QuikScat pass revealed winds of 20-25 kts associated with the LOW.  A
  later QuikScat pass indicated winds had increased to 30 kts within the
  band to the south of the center.   JTWC issued their first warning on
  TC-21S at 07/0000 UTC.  The initial warning intensity (1-min avg) was
  estimated 35 kts, based on CI estimates of 35 kts.  There had been a
  recent significant development of deep convection over the LLCC.  The
  system was centered only about 75 nm east-southeast of Cocos Island and
  was moving west-southwestward at 6 kts.  A mid-level ridge extending from
  the west coast of Australia was expected to influence the track for the
  next few days.  At 0300 UTC the Perth TCWC issued a gale warning for the
  LOW, indicating the likelihood of tropical cyclone development during
  the next 12-18 hours.   Just two hours later another warning upgraded
  the system to Tropical Cyclone Dianne with maximum 10-min mean winds
  estimated at 45 kts.  Dianne's center was very near Cocos Island at the
  time it was named as a tropical cyclone, moving west-southwestward at
  14 kts.

  B. Track and Intensity History

     At 07/1200 UTC Tropical Cyclone Dianne was located about 90 nm south-
  west of Cocos Island, moving west-southwestward at 11 kts.  There had
  been a significant increase in deep convection over the LLCC with a
  recent TRMM pass revealing a developing low-level banding eye feature.
  JTWC upped the 1-min avg MSW estimate to 55 kts, and Perth also upped the
  intensity to 55 kts at 1600 UTC.  Dianne continued moving in a west-
  southwesterly direction, reaching a point about 260 nm southwest of Cocos
  Island by 0000 UTC on 8 April.  A 07/2300 UTC TRMM pass had revealed
  tightly-curved bands with a developing banding eye feature.  Based on
  this and CI estimates of 55 and 65 kts, JTWC upped the 1-min avg MSW to
  65 kts.  Perth increased the 10-min avg MSW estimate to a comparable
  60 kts at 0400 UTC.

     At 08/1200 UTC Tropical Cyclone Dianne was located approximately
  400 nm west-southwest of Cocos Island, still moving west-southwestward at
  12 kts as it was steered by a mid-level ridge to the southeast.  Earlier
  visible imagery had revealed a cloud-filled banding eye while animated
  water vapor imagery showed an improving single poleward outflow channel
  that was being enhanced by the approach of a shortwave trough.  Satellite
  intensity estimates were 77 and 90 kts, so JTWC upped the 1-min avg MSW
  to 80 kts.   In their next warning, at 1600 UTC, Perth increased the
  intensity to 75 kts, making Dianne a severe tropical cyclone (hurricane).
  Dianne at this time was located about 465 nm west-southwest of Cocos
  Island--just east of longitude 90E.  By 1800 UTC the storm had crossed
  into the Southwest Indian Ocean basin and had been renamed Jery by the
  Mauritius Meteorological Service.      The 1800 UTC warning from MFR,
  however, did not concur with Perth's last assigned intensity--the MSW
  was reported at only 60 kts.  This was increased to 80 kts six hours
  later, in good agreement with JTWC's estimated 1-min avg MSW of 90 kts.
  Dianne-Jery by this time was located roughly 500 nm west-southwest of
  Cocos Island and had turned to a south-southwesterly track at 9 kts.
  Satellite imagery revealed that a 15-nm diameter eye had developed.

     MFR continued to report the intensity at 80 kts through 0600 UTC but
  lowered it to 75 kts at 09/1200 UTC.  Interestingly, it was at 1200 UTC
  that JTWC estimated their peak 1-min avg MSW of 105 kts, based on CI
  estimates of 90 and 105 kts.  Animated enhanced infrared imagery indi-
  cated that the storm had had strong poleward outflow during the previous
  12 hours which had helped to intensify it some.  Based on JTWC's warnings
  the gale radii were: 150 nm to the northeast and southeast, 120 nm to the
  southwest, and 90 nm to the northwest.  MFR's warnings indicated gales
  extended outward 180 nm in the southern semicircle and less elsewhere.
  The radius of storm-force winds was on the order of 40-45 nm.  At 1800
  UTC MFR brought the MSW down to 70 kts, and at 10/0000 UTC JTWC lowered
  their 1-min avg MSW estimate to 95 kts.  Dianne-Jery was then located
  approximately 650 nm southwest of Cocos Island, moving southward at
  7 kts, and was experiencing shearing in the southwest quadrant.  

     MFR and JTWC lowered their intensity estimates to 60 and 65 kts,
  respectively, at 1200 UTC.  There was no longer any deep convection in
  the western semicircle and open-cell cumulus could be seen wrapping into
  the center.  The cirrus shield extended toward the southeast, and a
  recent TRMM pass revealed a partially-exposed center--extratropical
  transition was well underway.  By 0000 UTC on the 11th Dianne-Jery was
  located about 720 nm southwest of Cocos Island and had turned to the
  southeast.  MFR and JTWC had lowered their MSW estimates to 50 and
  60 kts, respectively, based on CI estimates of 55 and 65 kts.  A SSM/I
  pass at 11/0000 UTC indicated a completely-exposed LLCC with deep con-
  vection sheared to the southeast and a large band of dry air to the
  north beginning to wrap into the center.

     JTWC issued their final warning on Dianne-Jery at 11/1200 UTC, clas-
  sifying it as extratropical.  The system was located about 800 nm south-
  west of Cocos Island and moving south-southeastward at 9 kts.  The final
  warning intensity from JTWC was 35 kts.  MFR was reporting 40 kts, but
  had also classified the system as extratropical.  The remnant gale
  re-entered Perth's AOR at 12/0000 UTC.  The Perth TCWC issued gale warn-
  ings on the system until 13/1200 UTC when it was located approximately
  850 nm west of Perth.

  C. Comparisons Between JTWC and Other Centers

     Intensity estimates between JTWC and Perth during Dianne's early life
  were in close agreement, and after the storm had crossed 90E and become
  Dianne-Jery, JTWC's 1-min avg MSW and MFR's 10-min avg MSW estimates
  also agreed rather closely except at 09/1200 and 10/0000 UTC.  As noted
  above JTWC increased their MSW to 105 kts while MFR lowered the 10-min
  avg MSW to 75 kts, equivalent to a 1-min avg MSW of 85 kts.  Six hours
  later JTWC had reduced their estimate to 95 kts and MFR had lowered
  theirs to 70 kts, equivalent to an 80-kt 1-min avg MSW.  However, by
  1200 UTC the respective intensity estimates were back in very close

  D. Damage and Casualties

     No reports of damage or casualties resulting from Tropical Cyclone
  Dianne-Jery have been received.

                          TROPICAL CYCLONE BONNIE
                                9 - 15 April

  A. Storm Origins

     A STWO issued by JTWC at 1800 UTC on 7 April noted that an area of
  unorganized convection had developed approximately 325 nm northeast of
  Darwin in the Arafura Sea.   CIMSS products indicated weak to moderate
  vertical shear over the region with fair outflow aloft.  Twenty-four
  hours later the disturbance was centered about 270 nm north of Darwin.
  Animated satellite imagery depicted unorganized and scattered convection
  associated with a weak LLCC.  A 200-mb analysis indicated divergence
  aloft associated with an upper-level ridge extending along latitude 12S.
  The Darwin TCWC gave the LOW a high potential for tropical cyclone devel-
  opment within the next 72 hours.  JTWC issued a TCFA at 1730 UTC on the
  9th, noting the continuing increase in deep convection near the LLCC.
  The system was located approximately 300 nm northwest of Darwin, and at
  1800 UTC the Darwin TCWC issued a gale warning for the LOW in anticipa-
  tion of its developing into a tropical cyclone within the next 12-24
  hours.  At 0000 UTC on 10 April, Darwin upgraded the system to Tropical
  Cyclone Bonnie, located about 130 nm east of the island of Timor, moving
  west-southwestward at 11 kts.   At the same time JTWC issued their first
  warning on Bonnie, but with an initial intensity of only 30 kts.

  B. Track and Intensity History

     By 1200 UTC on 10 April, Bonnie had entered Perth's AOR and was
  located over south-central Timor, moving west-southwestward at 9 kts.
  The island was inhibiting development somewhat with a 10/1320 UTC SSM/I
  pass showing most of the deep convection confined to the southern semi-
  circle.  Bonnie was forecast to track west-southwestward under the
  steering influence of a mid-level ridge extending from Australia into
  the Timor Sea.  The cyclone was situated beneath diffluent flow with good
  outflow aloft.   By 0000 UTC on the 11th Bonnie's center had moved out
  over the Savu Sea.  Both Perth and JTWC increased their respective inten-
  sity estimates to 40 kts, based on CI estimates of 45 kts (1-min avg) and
  a synoptic report of 35 kts from ship ZCA07.  A 10/2214 UTC SSM/I pass
  had revealed that deep convection was beginning to wrap into the center
  from the north and east.  The estimated MSW had increased to 45 kts by
  11/1200 UTC (from both Perth and JTWC).  Bonnie for the time being was
  moving westward, a motion which carried it skimming over the southern
  portion of the Indonesian island of Sumba.    Convection once more
  decreased as the cyclone interacted with a landmass.

     By 12/0000 UTC the center of Tropical Cyclone Bonnie was once more
  over water, moving west at 12 kts.  JTWC increased their 1-min avg MSW
  estimate to 50 kts at this time, and Perth also upped the intensity to
  50 kts at 0400 UTC.  The storm was located about 700 nm north of Onslow,
  and recent TRMM and SSM/I imagery depicted a developing banding feature
  extending over the southwest quadrant.  A 12/1039 UTC SSM/I pass indi-
  cated that the deep convection lacked organization and was sheared to
  the west of the LLCC.  JTWC dropped their intensity to 45 kts at 1200
  UTC, but Perth's 10-min avg MSW estimate remained at 50 kts through
  13/0100 UTC.  Bonnie was located about 200 nm south of Java at 0000 UTC
  on the 13th, moving west-southwestward at 15 kts.  Perth decreased the
  intensity to 45 kts at 0400 UTC, and at 1200 UTC JTWC dropped their 1-min
  avg MSW estimate to 40 kts.  Animated visible and infrared imagery showed
  that development had been hindered by interaction with Java.  Deep con-
  vection had decreased earlier, although some had recently redeveloped,
  and the center had become partially-exposed.

     At 14/0000 UTC the cyclone was located some 300 nm south of Java,
  still trekking west-southwestward.  The intensity estimates from Perth
  and JTWC were 45 and 40 kts, respectively.  A SSM/I pass at 13/2315 UTC
  revealed that an increase in the deep convection and organization of
  the system had occurred over the past few hours.  This apparent inten-
  sification trend, however, was short-lived.  By 1200 UTC most of the deep
  convection had dissipated.  JTWC lowered their intensity estimate to
  35 kts, whereas Perth was still reporting the MSW at 45 kts.  Bonnie at
  this time was located approximately 200 nm south-southwest of Christmas
  Island.  Perth lowered the 10-min avg MSW to 40 kts at 1600 UTC, and at
  2300 UTC issued their final gale warning on Bonnie.

     JTWC issued two more warnings on the system.  The 15/0000 UTC warning
  placed Bonnie's center about 340 nm southeast of Cocos Island, moving
  west-southwestward at 16 kts.  The MSW (1-min avg) was estimated at
  35 kts, based on CI estimates of 30 and 35 kts.  Convection had increased
  once again during the past six hours but remained disorganized.  Bonnie
  was forecast to weaken as it encountered increasing vertical shear.  The
  final JTWC warning at 1200 UTC placed the center about 250 nm south-
  southeast of Cocos Island, moving west at 16 kts.  The intensity was
  dropped to 30 kts.  Animated infrared imagery indicated that convection
  had dissipated near the LLCC and only scattered deep convection remained
  northwest of the center.  Multi-spectral imagery depicted a rapidly
  weakening LLCC.

  C. Comparisons Between JTWC and Other Centers

     Intensity estimates from JTWC compared reasonably well with those from
  the Darwin and Perth TCWCs after conversion to the same time averaging
  period.  In general JTWC's reported intensities ran a little lower than
  those from the Australian warning centers.

  D. Damage and Casualties

     Although the center of Tropical Cyclone Bonnie traversed two of the
  islands of Indonesia, no damage or casualties are known to have resulted.


  Activity for April:  No tropical cyclones


  SOUTH PACIFIC (SPA) - South Pacific Ocean East of Longitude 160E

  Activity for April:  2 tropical depressions
                       1 possible subtropical cyclone

                        Sources of Information

     The primary sources of tracking and intensity information for
  South Pacific tropical cyclones are the warnings and advisories
  issued by the Tropical Cyclone Warning Centres at Nadi, Fiji (for
  waters north of latitude 25S), and Wellington, New Zealand (for
  waters south of latitude 25S).  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 the Southern Hemisphere
  centres' 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

                  South Pacific Tropical Activity for April

     A fourth consecutive month passed without any tropical cyclones devel-
  oping in the South Pacific east of longitude 160E.  Fiji classified two
  systems as tropical depressions--numbered 15F and 16F.  Tropical Depres-
  sion 15F was a weak, short-lived system on the first two days of the
  month.  At 0300 UTC on the 1st, the system was centered roughly 400 nm
  northwest of Noumea, New Caledonia.  The depression drifted generally
  east-southeastward and was located about 250 nm northwest of Noumea when
  it was last mentioned at 02/0600 UTC.  Tropical Depression 16F was first
  noted about 320 nm north-northeast of Port Vila, Vanuatu, on the 17th.
  However, at 18/0600 UTC, the center was significantly relocated 275 nm
  southward to a point about 100 nm east-northeast of Port Vila.  Over the
  next few days the depression meandered around in the same area, perhaps
  drifting back to the north some, and was located north of Vanuatu when
  it was last referenced at 0600 UTC on the 23rd.    No gale warnings
  were issued by Nadi in association with this depression, but Tropical
  Disturbance Summaries issued by that office did note that fairly strong
  winds were occurring on the southern flank of the system from the 18th
  through the 21st due to the gradient with a strong HIGH centered near New
  Zealand.   By the 22nd the HIGH had moved eastward and the winds abated.

     Another low-pressure system which caught the attention of quite a few
  tropical weather observers formed in the Southeast Pacific near latitude
  30S well east of the Dateline during the first few days of April.  This
  system was handled as a non-tropical gale in warnings issued by the
  Wellington office, but did have some organized convection and some
  characteristics of tropical and subtropical cyclones, even sporting an
  eye-like feature at one point.   Dr. Karl Hoarau of Cergy-Pontoise
  University in France has agreed to study this system and if possible,
  generate a track for it.  When Karl has completed his analysis, I will
  include the results as a Feature of the Month in a subsequent 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
  in the following manner:

       (a) FTP to: []
       (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
           April as an example:   apr02.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:  apr02.sum, for

    Back issues can also be obtained from the following websites
  (courtesy of Michael Bath, Michael V. Padua and Michael Pitt):>> OR>>

     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:>


     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.

     The URL is:>

     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:>

     A special thanks to Michael Bath of Wollongbar, New South Wales,
  Australia, for assisting me with proofreading the summaries.

  Prepared by: Gary Padgett
  E-mail:  [email protected]
  Phone:  334-222-5327


Document: summ0204.htm
Updated: 27th December 2006

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