Tropical Cyclones [Index]

Monthly Global Tropical Cyclone Summary May 2000 [Summaries and Track Data] [Prepared by Gary Padgett]

                  MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY

                                MAY, 2000

  (For general comments about the nature of these summaries, as well as
  information on how to download the tabular cyclone track files, see
  the Author's Note at the end of this summary.)

  ***********************************************************************
                  
                             MAY HIGHLIGHTS

  --> Short-lived intense super typhoon churns Western Pacific waters
  --> First Eastern Pacific hurricane forms

  ***********************************************************************

                     NEW FEATURE - TOPIC OF THE MONTH

     I am planning to add a new feature to these monthly summaries, a
  sort of "topic of the month" article, discussing some interesting
  topic in the tropical cyclone arena.   I don't intend for this feature
  to be very lengthy--just a few paragraphs at most.  For some subjects
  I may be able to provide links and/or addresses where interested
  persons can look for more information.


                  ***** Topic of the Month for May *****

                   WHATEVER HAPPENED TO THE NEUTERCANE?

     As a result of some conversations I found myself involved in at the
  recent AMS 24th Conference on Hurricanes and Tropical Meteorology in
  Fort Lauderdale, Florida, I learned that there are quite a few younger
  meteorologists and graduate students (and some not quite so young)
  that have never heard the term "neutercane", or if they had, had no
  idea what it was or when it made its brief sojourn into the annals of
  North Atlantic weather history.  Simply put, the word was coined by
  former NHC Director Dr. Robert Simpson to describe a certain class of
  small, mesoscale subtropical cyclones that usually form in horizontal
  shear zones near dying cold fronts or else near the centers of old,
  occluded extratropical cyclones (what Paul Hebert termed a Type B
  subtropical cyclone).

     In 1972 NHC began issuing public subtropical cyclone bulletins and
  designated the storms with the phonetic alphabet.  In late May of that
  year a larger subtropical cyclone off the southeastern U. S. coast was
  dubbed Alpha but the term neutercane was not publicly used.  However,
  in late August a small subtropical cyclone formed in the western
  Atlantic and bulletins were issued for Neutercane Bravo.   (Bravo
  eventually developed full tropical characteristics and was redesignated
  Hurricane Betty west of the Azores.)      In late September another
  similar system was named Neutercane Charlie.

     However, Dr. Simpson retired in 1973 (I believe I'm correct here)
  with Dr. Neil Frank assuming the directorship of NHC, and the term was
  not publicly used again.   Subtropical cyclones were designated with
  the phonetic alphabet that year (with Subtropical Cyclone Bravo in
  October evolving into Hurricane Fran), but in 1974 that practice was
  dropped also.    Many years ago I read an article in the Bulletin of
  the AMS dealing with cyclone classification, and the neutercane was
  mentioned.  The writer of that article raised a couple of objections
  to the term:   (1) the use of "cane" as a syllable implies that
  hurricane is a compound word, which it is not; and (2) "neuter" has to
  do with gender, not an intermediate quality between two opposites or
  extremes (the proper term for that is "neutral").

     In spite of its official usage in only one hurricane season, the
  neutercane received a fair amount of publicity.   I have in an old
  scrapbook a newspaper clipping with the headline "Satellite Spots
  Sea-Going Storm That's Half Hurricane, Half Tornado"!   The World
  Almanac for 1973 had a short article describing the neutercane, and
  the word found its way into some dictionaries.   This apparently has
  been sufficient to keep the term alive to some degree, as I have seen
  it crop up in various places over the years, especially in some
  informal discussions and e-mails.

  Next Month:  A Source for State and Local Hurricane Histories

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                           ACTIVITY BY BASINS

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

  Activity for May:  1 subtropical depression


                        Atlantic Activity for May
                        -------------------------

     The month of May lies outside the nominal hurricane season in the
  Atlantic basin, although since 1886 twelve tropical storms, including
  three of hurricane intensity, have been tracked.    The last named
  tropical storm in the Atlantic basin was Tropical Storm Arlene in 1981
  which formed in the northwestern Caribbean on 5 May.   There have been
  several years since (1987, 1988, 1990, 1993) in which a tropical
  depression formed late in the month, but none of these were able to
  intensify to tropical storm intensity.   However, subtropical (hybrid)
  activity tends to be more frequent during the month and 2000 was no
  exception.

     Michael Pitt sent me some information on a LOW-pressure area on
  19-21 May which formed a few hundred miles southeast of Bermuda.  The
  Air Force Weather Association issued Dvorak satellite classifications
  on this LOW for about a day and a half, and TPC/NHC referred to it in
  their Tropical Weather Discussions as a complex system with an upper-
  level LOW with supporting fronts and an associated surface LOW.  A
  track for this system was included in the May cyclone tracks file.

     Michael later sent me some excerpts from TPC/NHC Discussions which
  I forwarded to David Roth, a meteorologist at HPC.  David researched
  the system and sent me a GOES infrared image of the system taken at
  0015 UTC on 20 May.  In that picture the LOW appears as a typical
  subtropical-type system with a band of convection somewhat removed
  from the center extending from the northwest quadrant around to the
  eastern side of the LOW.   According to David the system entered the
  subtropical phase on 19 May when moisture and temperature gradients
  were disappearing.  In David's estimation peak winds around the system
  were 30 kts during the initial non-tropical phase and about 25 kts
  during the subtropical phase.  The system began to shear on the 21st
  and 22nd as it drifted eastward, and lost its closed circulation
  soon after 22/0600 UTC.  (A special thanks to Michael and David for
  the information they provided on this system.)

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

  Activity for May:  1 hurricane

  NOTE:  Much of the information presented below was obtained from the
  TPC/NHC discussion bulletins issued with every regular advisory (CPHC
  for locations west of 140W.)  All references to sustained winds imply
  a 1-min averaging period unless otherwise noted.  


                    Northeast Pacific Activity for May
                    ----------------------------------

     The Northeast Pacific tropical season got started a little earlier
  than normal in 2000.   Since 1966 (the year that is considered to have
  been the beginning of complete operational satellite coverage) the
  first Eastern Pacific tropical storm has appeared in May sixteen times
  (including 2000).  Of the 35 years from 1966 through 2000, in only
  seven seasons did the first tropical storm appear earlier in the month
  than this year's Hurricane Aletta.

     The write-up for Hurricane Aletta was prepared by John Wallace, a
  student at the University of Texas in San Antonio who has had a keen
  interest in tropical cyclones and climatology for several years.
  Although he didn't initially plan to, John tells me that now he is
  seriously considering majoring in meteorology.   John is interested
  in tropical climatology and patterns of storm formation, and has a
  special interest in the Northeast Pacific region.   Last year he wrote
  for me the narrative for Tropical Storm Irwin in October, the final
  storm of the 1999 season in the Northeast Pacific.  A special thanks
  to John for writing the Aletta summary--it helped me out enormously.
  (John has already sent me his write-ups for Bud and Carlotta in June,
  so hopefully I'll be able to get the June summary out a little earlier
  than usual.)


                      Hurricane Aletta  (TC-01E)
                             22 - 28 May
                      --------------------------

     Hurricane Aletta was the first May "named" storm since 1996.
  However, the 1996 storm was retroactively upgraded to storm status
  (i.e.,unnamed).  With this in mind, Aletta was the first May storm
  actually warned on as a tropical storm since 1991.  It was the first
  May hurricane since 1990, and the strongest May hurricane since 1983's
  Hurricane Adolph, which peaked at 95 kts--the current record-holder
  for intensity in May since the beginning of the era of complete
  satellite coverage in the late 1960s.

     A tropical LOW developed in the wake of an easterly wave late in
  the second week of May.  The LOW generated only sporadic convection
  through the 21st and remained nearly stationary during that time.
  Even so, by 0000 UTC on 20 May there was definite loose, spiral
  banding, while the convection fluctuated in an apparent diurnal
  bursting pattern.    The synoptic conditions were favorable for
  development, with light shear, modest ridging aloft, very warm SSTs,
  and no dry air intrusion at the mid- to upper-levels.    Though
  convection was strong on the 20th, it weakened greatly on the 21st,
  so much so that it looked for a moment like the LOW would not
  develop, though conditions became increasingly favorable.  Satellite
  presentation notwithstanding, the estimated CP of the LOW was stable
  at 1008 mb from the 20th through late on the 21st.

     There was a dramatic nocturnal increase in convection starting at
  0600 UTC on 22 May, concurrent with the development of a slow easterly
  track.  Between 0600 and 1400 UTC, the LOW deepened and changed from a
  broad spiral of low clouds to a robust, well-organized cyclone with a
  CDO nearly centered over the LLCC.  The LOW was upgraded to Tropical
  Depression One-E at 1500 UTC on 22 May when the center was located
  about 225 nm south-southeast of Acapulco.   Conditions were highly
  favorable for further development as an upper-level anticyclone
  centered itself over the depression.  The cyclone's west-northwesterly
  track was influenced by a mid-level ridge to its north, and this was
  forecast to keep it parallel to but safely offshore from Mexico until
  a strong trough to the northwest was expected to induce a more
  northerly motion.  The track on the whole was expected to conform
  closely to climatology.

     The depression intensified slowly through the 22nd and into the
  23rd; its forward speed decreased by almost half accordingly as
  steering currents weakened.     By 0900 UTC on 23 May Tropical
  Depression One-E was upgraded to Tropical Storm Aletta as the Dvorak
  T-number reached 2.5.   The newly-named tropical storm was located
  about 315 nm south-southeast of Manzanillo, Mexico.  The track,
  initially parallel to the Mexican coast, changed to a more westerly
  one as storm intensity was reached.    The last public advisory was
  issued since the storm now presented no significant threat to the
  mainland.  Conditions remained favorable for slow strengthening, though
  University of Wisconsin CIMSS data indicated seemingly more favorable
  conditions than NHC noted in its advisories.

     Convection intensified and overall organization increased markedly
  after the upgrade, though the center remained difficult to locate in
  the developing storm.  Aletta's central pressure fell a respectable
  15 mb in the 24 hours from 1500 UTC on 23 May to 1500 UTC on the
  24th, when the storm was upgraded to hurricane status about 300 nm
  south-southwest of Manzanillo.    A diffuse, cloud-filled eye was
  apparent in visible imagery by 1745 UTC on the 24th; a TRMM overpass
  at 1609 UTC confirmed a 30-nm diameter eye.  A SSM/I overpass at the
  same time showed a closed eyewall, though it disappeared on visible
  and infrared imagery soon after.

     Hurricane Aletta intensified quickly, reaching its peak 90-kt MSW
  and CP of 970 mb just 18 hours later, at 0900 UTC on 25 May, roughly
  275 nm southeast of Socorro Island.    It briefly sustained this
  intensity until 1500 UTC when a slow weakening trend began.   The
  intensification trend occurred even though synoptic conditions were
  less favorable than they had been earlier.     The upper-level
  anticyclone that fostered Aletta's initial development had weakened
  slightly and moved north over Mexico by 0000 UTC on the 24th, creating
  light easterly shear.  The SSTs were still warm, however, and there
  was no entrainment of stable air.    Soon after Aletta peaked in
  intensity, the CDO became less symmetric as convection was displaced
  west of the center by easterly shear, exposing the center and low-level
  banding in its eastern semicircle.  Strong low-level southwesterly flow
  exacerbated the easterly shear.  The beginning of the weakening trend
  coincided with an almost complete collapse of steering winds.  Aletta
  was already embedded in a broad col between a strong subtropical ridge
  over the Gulf of Mexico and Caribbean, and the Pacific subtropical
  ridge far to the west; a strong upper-level trough west of Baja
  California, well to the northwest, had eroded the mid-level ridge to
  the north that had provided most of Aletta's steering.  The stall was
  well-forecast by certain models, but caught the NHC official forecasts
  slightly by surprise.  Aletta became quasi-stationary by 0000 UTC on
  the 26th, and scarcely moved until the last advisory was issued.

     Aletta became increasingly ragged on the 26th as the shear became
  more northeasterly.  The upper-level anticyclone responsible for the
  shear had weakened since Aletta's peak, but was apparently strong
  enough to make life difficult for the weakening hurricane.  Aletta
  weakened very rapidly on the 27th, dropping below hurricane intensity
  by 0300 UTC, and to a depression by 1500 UTC when no deep convection
  remained.  The last advisory on the weak, low-level vortex was issued
  at 0300 UTC on 28 May, as it drifted northward to cooler waters.   An
  ill-defined, mid- to low-level vortex persisted in the same location
  until 1 Jun, after which the remnant circulation was unidentifiable in
  any satellite channel.
   
     Aletta's rapid weakening trend is a minor mystery.  Shear over the
  system was not strong, and by the time Aletta had dissipated was
  actually favorable.  Water vapor imagery from 1200 UTC on 26 May
  shows northeastward advection of moisture from Aletta's vicinity,
  but this jet apparently had little or no direct impact on the storm.
  There was no evidence of entrainment of more stable air--as evidenced
  in visible imagery by extensive stratiform clouds--if it was a culprit,
  it was subtle.  Nor was there any evidence of dry air entrainment in
  water vapor imagery.   However, water vapor imagery from 1200 UTC on
  27 May showed that the moisture content of the atmosphere over Aletta's
  rough position was slightly drier than that of its surroundings.  The
  import of this on Aletta's dissipation is unknown, or indeed if it was
  even a real feature.  If it was a real feature, though, it would indeed
  be unfavorable, perhaps indicating subsidence.  Imagery from 1215 UTC
  the following day suggests it was a real feature.   As for SSTs, they
  were not unfavorably cool, roughly 27 C; anomaly imagery shows little
  significant upwelling, a surprise given Aletta's stall.    A minor
  mystery, but enough to pique the curiosity.

     No casualties or damage are known from Aletta at this time.  The
  storm did briefly present the threat of heavy coastal rains to Mexico,
  but as the system was compact these apparently did not occur.

  NOTE from Gary:  I let John's next-to-last paragraph stand basically
  as he wrote it--exploring reasons why Aletta weakened so rapidly in
  the absence of any obvious hostile environmental factors.    I have
  since learned from Jack Beven that Richard Pasch, in his preliminary
  report on the storm, concluded that upwelling after all was likely the
  primary culprit contributing to the rapid weakening of Aletta on
  26 and 27 May.

  ***********************************************************************

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

  Activity for May:  2 tropical depressions
                     1 tropical storm
                     1 super typhoon

  NOTE: Most of the information on each cyclone's history presented in
  the narrative will be based upon JTWC's advisories, and references to
  winds should be understood as a 1-min avg MSW unless otherwise noted.
  However, in the accompanying tracking document I have made comparisons
  of coordinates with JMA (Japan) and the Philippines (PAGASA) when their
  positions differed from JTWC's by usually 40-50 nm or more.  A special
  thanks to Michael V. Padua, owner of the Typhoon 2000 website, for
  sending me the PAGASA and JMA tracks.

     In the title line for each storm I plan to reference all the cyclone
  names/numbers I have available:    JTWC's depression number, the
  JMA-assigned name (if any), JMA's tropical storm numeric designator,
  and PAGASA's name for systems forming in or passing through their area
  of responsibility.


                    Northwest Pacific Activity for May
                    ----------------------------------

     After lying quiet for the first four months of the year, the North-
  west Pacific suddenly became quite active, producing one of the most
  intense super typhoons ever noted during the month of May.  Three
  other tropical depressions formed, but only one of these attained
  tropical storm intensity.   Damrey and Longwang became the first storms
  to be named from the roster of Asian typhoon names.  (More information
  on these new names can be found in the global summary for December,
  1999.)

     Tropical Depression 03W (named Konsing by PAGASA) formed on 20 May
  about 300 nm southeast of Hong Kong (or roughly the same distance
  northwest of Manila).  This depression never generated winds higher
  than 30 kts as it moved east-northeastward through the Luzon Strait.
  The final warning (from PAGASA) at 22/0600 UTC placed the weakening
  center about 300 nm east-northeast of the southern tip of Taiwan.

     Tropical Depression 04W formed on 30 May in the South China Sea
  just off the coast of southern Vietnam about 200 nm south-southeast of
  Da Nang.  This weak system drifted generally north-northwestward,
  paralleling the Vietnamese coast.  Maximum winds were estimated at
  no more than 25 kts most of the time, briefly reaching 30 kts at
  1200 and 1800 UTC on the 31st.  The final JTWC warning at 1800 UTC
  on 1 Jun placed the dissipating center just off the coast in the Gulf
  of Tonkin about 175 nm south-southeast of Hanoi.  JTWC was the only
  warning agency to issue bulletins on this system.


             Super Typhoon Damrey  (TC-01W / TY 0001 / Asiang)
                               5 - 12 May
             -------------------------------------------------

     The waters of the Western North Pacific were quiet for the first
  four months of 2000, but then exploded with a bang.    The first
  tropical depression of the year became the first tropical storm,
  which then became the first typhoon, which in turn became the first
  super typhoon and the second strongest May typhoon on record (dating
  back to 1945).   Capt. Jim Parsons, a Typhoon Duty Officer at JTWC,
  checked the JTWC Best Track database and also the consolidated world-
  wide Tropical Cyclone database (maintained at the National
  Climatological Data Center in Asheville, North Carolina), and
  reported that the only May typhoon to have exceeded Damrey's peak
  intensity of 155 kts was Typhoon Phyllis in 1958 (160 kts).   Also,
  Typhoon Iris in May, 1951, reached a peak intensity of 150 kts.  But
  the opinion has often been expressed that many of the MSW estimates in
  earlier years were too high, so the possibility exists that Damrey
  was in fact the most intense May typhoon on record.  (A special thanks
  to Jim for looking this up for me.)

     On 3 May JTWC issued a STWO at 1400 UTC which indicated that an
  area of convection had developed south of Yap and had persisted for
  more than 18 hours.   A QuikScat pass indicated a broad, weak LLCC
  with good outflow.   A few hours later the center of action was
  determined to be farther west--about 125 nm southeast of Palau--with
  convection increasing in areal coverage.  The system's potential for
  development was upgraded to Fair.   The area of convection passed over
  Palau around 04/0600 UTC, and at 2330 UTC JTWC issued a Formation
  Alert.   The LLCC was partially exposed with most of the convection
  to the west of the center which was embedded in the monsoon trough.
  The disturbance continued to trek slowly northwestward on 5 May,
  gradually becoming better organized, and JTWC issued the first warning
  on Tropical Depression 01W at 1800 UTC with the center estimated to be
  located about 250 nm north-northwest of Palau.     PAGASA initiated
  warnings at 0000 UTC on 6 May (naming the depression Asiang), and
  JMA began issuing warnings at 0600 UTC.

     TD-01W continued to move slowly northwestward on 6 May.  By 1200 UTC
  animated imagery showed that the system was rapidly intensifying and
  JTWC upgraded the depression to a tropical storm with 40-kt winds,
  located about 325 nm north-northwest of Palau.   PAGASA upgraded the
  system to a 35-kt tropical storm (10-min avg winds) at 1800 UTC, and
  JMA followed suit at 07/0000 UTC, naming the storm Damrey.   JTWC had
  increased the MSW to 60 kts by this time, based upon satellite
  intensity estimates of 55 and 65 kts.  Animated imagery showed that
  Damrey was continuing to organize and had developed outflow channels
  to the north and south of the system.    JTWC upgraded Damrey to a
  typhoon at 07/0600 UTC when the center was located about 450 nm east
  of Catanduanes Island in the Philippines.  Damrey by this time had
  moved into a weakness in the subtropical ridge and was moving very
  slowly in a general northward direction.    The MSW estimate reached
  75 kts at 1800 UTC with the storm now drifting very slowly northeast-
  ward.  A TRMM pass at 1819 UTC suggested that a weak eye feature was
  beginning to form with a strong convective band to the north and west
  of the LLCC.

     JMA upgraded Damrey to a typhoon at 08/0000 UTC.  At 0600 UTC a
  banding eye was visible in animated satellite imagery as well as in
  SSM/I imagery.   The typhoon had reached the westernmost point in its
  track around 0000 UTC on 8 May when it was centered about 425 nm east
  of Catanduanes Island.   From this point onward Damrey's motion was
  always to the northeast or east-northeast.   By 1800 UTC a 17-nm
  diameter ragged eye was visible and the typhoon was beginning to
  rapidly intensify as it had moved underneath the upper-level ridge
  axis.   JTWC increased the MSW to 105 kts based upon Dvorak estimates
  of 102 and 115 kts.  (JMA's 10-min avg MSW estimate at this time was
  75 kts.)    Damrey continued to deepen and by 0600 UTC on the 9th
  had reached super typhoon intensity of 130 kts about 600 nm west of
  Saipan.   The storm had picked up some in forward speed and was
  moving northeastward at 13 kts.  Satellite imagery revealed a round,
  cloud-free eye approximately 8 nm in diameter with impressive outflow
  in all quadrants.   Based upon current intensity estimates of 140 and
  155 kts, JTWC further increased the MSW to 150 kts at 1200 UTC.  Damrey
  at this time displayed a 14-nm wide cloud-free eye with two convective
  bands approximately 200 nm and 320 nm east of the eye, respectively.

     Super Typhoon Damrey reached its estimated peak intensity of 155 kts
  at 1800 UTC on 9 May.  The storm at that time was centered roughly
  600 nm west-northwest of Guam or about 450 nm southwest of Iwo Jima,
  moving northeastward at 16 kts.  In terms of areal extent Damrey was a
  rather small typhoon.   At its peak gales extended outward 170 nm to
  the southeast and 135 nm elsewhere.    The radii of 50-kt winds were
  100 nm to the southeast and 65 nm elsewhere, and 100-kt winds were
  confined to within about 20 nm of the center.  The peak 10-min avg
  MSW assigned to the storm by JMA was 90 kts from 09/1200 UTC through
  10/0000 UTC, and the minimum CP (also from JMA) was 930 mb.  

     As is often the case with small tropical cyclones, Damrey weakened
  even more quickly than it had intensified.     Six hours after peak
  intensity was reached, JTWC lowered the MSW to 140 kts as the storm was
  beginning to show signs of weakening in an environment of increased
  vertical shear.  The eye had become ragged and cloud-filled.   By
  0600 UTC on 10 May animated visible imagery revealed that deep
  convection had decreased dramatically over the western half of the
  system.  Damrey had moved north of the upper-level anticyclone and
  moderate to strong southwesterlies overlay the storm.   The typhoon's
  center at this time was about 300 nm southwest of Iwo Jima and winds
  had dropped to 105 kts.  By 1800 UTC there was little deep convection
  associated with the LLCC, and by 11/0000 UTC, only 30 hours after
  reaching its peak intensity, Damrey had weakened back to tropical
  storm intensity of 60 kts.  (This is per JTWC's assessment.  During
  the decay phase JMA's 10-min avg MSW estimates were somewhat higher
  than JTWC's reported 1-min avg MSW values.  JMA maintained Damrey as
  a typhoon through 11/0600 UTC, and was still reporting 50 kts at
  12/0000 UTC when JTWC's MSW estimate was only 35 kts.)

     Caught up in southwesterly flow and in a hostile vertical shear
  environment, Damrey continued to gradually accelerate to the northeast
  as it weakened.   By 0000 UTC on the 11th the LLCC had become exposed
  with convection being sheared to the northeast.    Damrey passed about
  30 nm northwest of Iwo Jima at 0600 UTC with 45-kt winds, moving
  northeastward at 16 kts.     By 0000 UTC on 12 May the former super
  typhoon was a minimal tropical storm located about 300 nm northeast of
  Iwo Jima and moving to the east-northeast at 20 kts.  JTWC wrote its
  final warning at 0600 UTC, and (per JMA) Damrey was becoming extra-
  tropical at 1200 UTC about 525 nm east-northeast of Iwo Jima.

     Fortunately, this brief but very intense typhoon did not (to the
  author's knowledge) affect any populated areas.


             Tropical Storm Longwang (TC-02W / TS 0002 / Biring)
                                 18 - 20 May
             ---------------------------------------------------

     On 16 May a broad, weak LLCC was located in the northern South
  China Sea west of Luzon.   The disturbance was located in a monsoon
  trough extending across the northern South China Sea and was quasi-
  stationary.  Most of the convection associated with the system was
  well south of the LLCC under moderate to strong vertical shear.
  A STWO issued by JTWC at 0600 UTC on 17 May mentioned that deep
  convection appeared to be associated with linear convergence south
  of the LLCC.  A QuikScat pass showed that the stronger winds were
  located on the outer edge of the circulation.    A SSM/I pass at
  1247 UTC depicted improved organization with deep convection wrapping
  around the northern periphery of the LLCC.  Synoptic data and satellite
  imagery indicated that the center was located over land about 100 nm
  northwest of Manila.  CIMSS vertical shear charts and a 200-mb analysis
  indicated a favorable environment for strengthening, and JTWC upgraded
  the potential for development to Fair in a special STWO at 2000 UTC.
  (PAGASA initiated warnings on the developing system at 1800 UTC, naming
  it Tropical Depression Biring.)

     By 0600 UTC on the 18th the LLCC was located just off the north-
  eastern coast of Luzon.  JTWC issued a Formation Alert at 0700 UTC as
  animated visible imagery showed a continued increase in convective
  organization.     At this stage the disturbance displayed monsoon
  depression characteristics with the deepest convection and strongest
  winds on the periphery of the LLCC, which was helping to anchor a
  reverse monsoon trough pattern.  Later on 18 May the depression began
  to develop rapidly about 125 nm northeast of Port San Vincente in the
  Philippines with the LLCC located about 15 nm west of some deep
  convection.  JTWC wrote the first warning on TD-02W at this time with
  an initial intensity of 30 kts, based upon satellite CI numbers of
  30 and 35 kts.  JMA upgraded the depression to Tropical Storm Longwang
  at 19/0000 UTC with 40-kt winds (10-min avg) and centered about 225 nm
  northeast of the northeastern tip of Luzon.  JTWC upgraded the system
  to a tropical storm also at 0000 UTC.   Deep convection was wrapping
  around the northern quadrant of the LLCC but was inhibited along the
  western edge by westerly shear.   A SSM/I pass at 2153 UTC depicted
  a solid band of convection south through northeast of the center with
  weak convection in the other quadrants.

     Longwang reached its peak intensity of 40 kts (per JTWC analysis)
  at 0600 UTC when gales extended outward 45 nm to the southeast of the
  center and 35 nm elsewhere.  The storm was centered about 250 nm south-
  southwest of Okinawa and moving northeastward at 13 kts.  A 200-mb
  analysis indicated that the upper-level ridge was situated to the
  south of the system, near Luzon, with weak diffluence noted over the
  storm.  Six hours later Longwang was moving rather quickly (21 kts) to
  the northeast about 170 nm south-southeast of Okinawa.   The MSW was
  still estimated at 40 kts based upon CI estimates of 35 and 45 kts, but
  a 19/0908 UTC SSM/I pass depicted a weakened system with convection
  displaced almost 50 nm east of an exposed LLCC.  The western half of
  the system was virtually cloud-free.   At 1800 UTC JTWC dropped the
  MSW to 35 kts, but JMA's peak 10-min avg intensity of 45 kts was
  assigned at this time.  The JMA analyzed position for 1800 UTC was
  about one degree to the northeast of JTWC's position, and with the
  storm undergoing strong southwesterly shearing, it seems likely that
  the JMA analyst placed the LLCC underneath the convection.

     By 20/0000 UTC JTWC had downgraded Longwang to a tropical depression
  located about 355 nm east of Okinawa.  The system exhibited a small
  LLCC with the convection sheared to the northeast and was forecast to
  track rapidly east-northeastward in mid-latitude westerly flow.  Six
  hours later the depression was becoming extratropical and merging with
  a frontal boundary about 240 nm north-northwest of Iwo Jima as it raced
  to the east-northeast at 39 kts.

  ***********************************************************************

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

  Activity for May:  No tropical cyclones

  ***********************************************************************

  SOUTH INDIAN OCEAN (SIO) - South Indian Ocean West of Longitude 90E

  Activity for May:  No tropical cyclones

  ***********************************************************************

  AUSTRALIAN REGION (AUG) - From Longitude 90E Eastward to Longitude 160E

  Activity for May:  1 tropical LOW


                    Australian Region Activity for May
                    ----------------------------------

     A tropical disturbance formed on 20 May near Rennell Island in the
  Solomon group and was assigned a number (24F) by the Fiji TCWC at
  Nadi.  The system subsequently drifted westward for a few days into
  the Australian Region.   A tight pressure gradient with a HIGH to the
  south caused gales to be generated in the southern semicircle of the
  system and Brisbane issued gale warnings for a couple of days.  The
  LOW drifted slowly westward and the final gale warning at 23/0000 UTC
  placed the center only about 275 nm west of Rennell Island.  The
  highest Dvorak rating located by the author for this depression was
  only T1.5.

  ***********************************************************************

  SOUTHWEST PACIFIC (SWP) - South Pacific Ocean East of Longitude 160E

  Activity for May:  2 tropical depressions


                    Southwest Pacific Activity for May
                    ----------------------------------

     There were no named tropical cyclones in the South Pacific region
  during May, but there were a few depressions/disturbances which the
  Fiji TCWC assigned numbers to.  The first and longest-lived disturbance
  was Tropical Depression 22F which formed on 3 May about 350 nm south-
  east of American Samoa.    Six hours later the center seems to have
  reformed about 100 nm farther to the southeast.   Initially, the LOW
  was more extratropical in nature, lying under a 250-mb trough axis,
  and, while designated as a tropical LOW in warnings, did not receive
  a number until 5 May when there was an increase in convection fairly
  close to the center.   The depression remained quasi-stationary for
  several days before drifting slowly to the west-southwest and
  weakening.  The final warning received by the author, at 08/1800 UTC,
  placed the LOW's center about 500 nm south-southeast of American Samoa.
  Gale warnings were issued for winds up to 40 kts in the southern
  semicircle, but the highest Dvorak ratings assigned by JTWC and KGWC
  were only T1.5.  A track is included for this depression in the May
  tropical cyclone tracks file.

     Another disturbance between Fiji and Vanuatu was designated as
  Tropical Disturbance 23F on 6 May.  This system was briefly referred
  to as a tropical depression, but was sheared and did not develop
  further.  No track is given for this system in the tracks file.
  Finally, a third disturbance was designated as Tropical Disturbance
  24F on 20 May near Rennell Island in the Solomon group.  This location
  is near 160E (the boundary of Brisbane's AOR) and the disturbance
  subsequently drifted westward into the Australian Region where the
  Brisbane TCWC issued gale warnings for a couple of days.  More on this
  system can be found in the Australian Region portion of this 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, but since May was a
  relatively quiet month, I have included the Glossary at the end of
  this summary following the Author's Note.

  ***********************************************************************

  AUTHOR'S NOTE:  This summary should be considered a very preliminary 
  overview of the tropical cyclones that occur in each month. The cyclone
  tracks (provided separately) will generally be based upon operational
  warnings issued by the various tropical cyclone warning centers.  The
  information contained therein may differ somewhat from the tracking and
  intensity information obtained from a "best-track" file which is based
  on a detailed post-seasonal analysis of all available data. Information
  on where to find official "best-track" files from the various warning
  centers will be passed along from time to time.

    The track files are not being sent via e-mail.  They can be retrieved
  in the following manner:

       (a) FTP to:  hrd-type42.nhc.noaa.gov [140.90.176.206]
       (b) Login as: anonymous
       (c) For a password use your e-mail address
       (d) Go to "data" subdirectory (Type: cd data)
       (e) Set file type to ASCII (Type: ascii)
       (f) Transfer file (Type: get remote_file_name local_file_name )
           (The files will be named with an obvious nomenclature--using
           May as an example:   may00.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:  may00.sum, for
  example.

    Back issues can also be obtained from the following websites
  (courtesy of Michael Bath, Michael V. Padua, Tom Berg, Michael
  Pitt, and Rich Henning):

    http://australiansevereweather.com/cyclones/>
    http://www.geocities.com/capecanaveral/6825>
    http://www.hurricanealley.net/>
    http://www.qisfl.net/home/hurricanemike>
    http://www.met.fsu.edu/gsc/Docs/Grads/henning/cyclones/>

     Another website where much information about tropical cyclones may
  be found is the website for the UK Meteorological Office.  Their site
  contains a lot of statistical information about tropical cyclones
  globally on a monthly basis.  The URL is:

    http://www.met-office.gov.uk/sec2/sec2cyclone/sec2cyclone.html>


                   TROPICAL CYCLONE REPORTS AVAILABLE

     I have discovered that JTWC now has available on its website the
  complete Annual Tropical Cyclone Report (ATCR) for 1999 (1998-1999
  season for the Southern Hemisphere).  Also, ATCRs for earlier years
  are available also.

     The URL is:  http://199.10.200.33/jtwc.html>

     Also, TPC/NHC has available on its webpage nice "technicolor"
  tracking charts for the 1999 Atlantic and Eastern North Pacific
  tropical cyclones; also, preliminary storm reports for all the 1999
  Atlantic and Eastern North Pacific cyclones are now available.

     The URL is:  http://www.nhc.noaa.gov>

  Prepared by: Gary Padgett
  E-mail:  [email protected]
  Phone:  334-222-5327 (nights & weekends) / 850-882-2594 (weekdays)

  ***********************************************************************
  ***********************************************************************

                 GLOSSARY of ABBREVIATIONS and ACRONYMS

  AOML/HRD - Atlantic Oceanographic and Meteorological Laboratory/
             Hurricane Research Division, located on Virginia Key, Miami,
             Florida, U.S.A.

  AOR -     area of responsibility

  CDO -     central dense overcast

  CI -      current intensity

  CIMSS -   Cooperative Institute for Meteorological Satellite Studies
            (University of Wisconsin-Madison)

  CP -      central pressure

  CPHC -    Central Pacific Hurricane Center, Honolulu, Hawaii, U.S.A.

  FLW -     flight level wind (or winds)

  FTP -     file transfer protocol

  HPC -     Hydrometeorological Prediction Center, Camp Springs,
            Maryland

  IMD -     India Meteorological Department (RSMC New Delhi, India)

  JMA -     Japanese Meteorological Agency (RSMC Tokyo, Japan)

  JTWC -    Joint Typhoon Warning Center, formerly on Guam, now at
            Pearl Harbor, Hawaii

  kt -      knot = 1 nautical mile per hour

  LLCC -    low-level circulation center
         
  m -       meter, or metre

  mb -      millibar, numerically equivalent to hectopascal (hPa)

  MFR -     Meteo France on Reunion Island

  mm -      millimeter

  MSW -     maximum sustained wind(s) (either 1-min avg or 10-min avg)

  nm -      nautical mile = 6076.12 feet or 1852.0 meters

  NPMOC -   Naval Pacific Meteorological and Oceanographic Center, Pearl
            Harbor, Hawaii, U.S.A.

  PAGASA -  Philippines' Atmospheric, Geophysical & Astronomical Services
            Administration

  RSMC -    Regional Specialized Meteorological Centre

  SST -     sea surface temperature

  STS -     severe tropical storm (MSW greater than 47 kts)

  STWO -    Significant Tropical Weather Outlook - bulletin issued
            daily by JTWC giving information about various areas of
            disturbed weather and the potential for tropical cyclone
            development

  TC -      tropical cyclone

  TCWC -    Tropical Cyclone Warning Centre (generic term)

  TD -      tropical depression

  TPC/NHC - Tropical Prediction Center/National Hurricane Center, Miami,
            Florida, U.S.A.

  TS -      tropical storm

  WMO -     World Meteorological Organization, headquartered at Geneva,
            Switzerland

  UTC -     Universal Time Coordinated, equivalent to Greenwich Mean Time
            or Zulu (Z)