Tropical Cyclones
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Monthly Global Tropical Cyclone Summary May 2001
[Summaries and Track Data] [Prepared by Gary Padgett]


                                MAY, 2001

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

  SPECIAL NOTE:  I have included the Glossary of Abbreviations and
                 Acronyms at the end of this summary.  New acronym
                 added:  TCFA - Tropical Cyclone Formation Alert


                              MAY HIGHLIGHTS
  --> Intense Arabian Sea cyclone threatens west coast of India
  --> Most intense May Eastern Pacific hurricane on record forms


                ***** Feature of the Month for May *****

     A few months ago I sent a little survey to several persons whom
  I either knew personally or else had corresponded much with over the
  past three years that I've been writing the global tropical cyclone
  summaries.  The following were the ones who responded, and to them
  I would like to extend a special thanks for taking the time to reply:
  Jeff Callaghan, Steve Ready, Matthew Saxby, Philippe Caroff, James
  Franklin, David Roth, Jack Beven, Chris Landsea, Julian Heming, and
  Rich Henning.

     The survey was a solicitation of opinions regarding certain issues
  relevant to the classification of tropical cyclones, especially
  focusing on borderline type systems which in some basins may be
  readily treated as tropical cyclones and not in others.  The questions
  that I asked in the survey were as follows (slightly reworded):

  (1) Regarding subtropical cyclones or otherwise hybrid systems:  How
      "tropical" should one be before being classified as a tropical

  (2) Regarding spatial distribution of gales:  In how many quadrants
      and how close in to the center should gales be occurring before
      a system is named as a tropical storm (or cyclone)?

  (3) Should monsoon depressions with gale-force winds be considered
      tropical storms (or cyclones)?

  (4) Should the (usually) small TUTT-generated systems of higher
      latitudes be considered tropical cyclones?

  (5) Regarding extremely small midget systems:  Should there be a
      size criterion for classification as a tropical cyclone?

     All the tropical cyclone warning agencies have official terminology
  and operational procedures which work well in their respective areas
  of responsibility, and issuing timely and accurate warnings in real
  time is certainly the primary goal of all warning centers.  But the
  study of tropical cyclones from a climatological and statistical
  perspective and with a global scope is also very important, even if
  secondary to the operational warning side of things.  And such study
  is quite often hampered because of inconsistencies in the manner in
  which the above types of systems are treated between the various
  warning centers (or sometimes even by a given center).

     My purpose was to try to get a little dialogue going regarding some
  of those issues which I have come to perceive as "sticking points" that
  need some sort of consensus if the goal of a reasonably consistent
  global definition of a tropical cyclone is ever to be attained.  I am
  concerned here with systems whose winds have reached gale intensity
  (34 kts or higher) and normally would be assigned names as tropical
  storms (tropical cyclones in WMO Region 5) by the responsible warning
  center (except of course in the North Indian Ocean).    These are the
  systems which are normally archived in databases by the various
  meteorological agencies and are, in a sense, the ones "remembered" by

     My plan is to utilize the responses I have received as material for
  my Feature of the Month articles for about three months.    However,
  if anyone else has an opinion they'd like to share on any of the
  above questions, I'd be happy to hear from them and will include their
  responses in with the others.     For this month I am limiting the
  discussion to the last question:  Should there be an arbitrary size
  criterion for classification as a tropical cyclone?

     Several of the respondents wondered why I'd even asked that
  question.  Admittedly, the size of a system is for the most part a
  non-issue.   But that question was raised many years ago in the
  excellent annual summary article for the Eastern Pacific hurricane
  season of 1971 written by William J. Denney, then of the NWS Forecast
  Office in San Francisco.  (The article was published in Monthly Weather
  Review, Volume 100, Number 4, April, 1972.)     In his discussion of
  Tropical Storm Katrina, which was a very small, tightly-wound tropical
  storm that in its early stages apparently had the magnitude of a meso-
  cyclone, Mr. Denney pointed out that some storms seen in the Eastern
  Pacific during the previous years since the advent of satellites had
  gale-wind areas as small as 15 nm in diameter.   He briefly discussed
  the issue of whether there should be an arbitrary size definition to
  distinguish the "ministorm" from the normal-sized tropical cyclone,
  mainly because of the difficulty of following such small storms as
  Katrina.   However, his conclusion was that, instead of instituting a
  size criterion for tropical cyclones, the problem might better be
  considered a challenge to the improving skill and technology of applied

     Australia has an outstanding example of what a midget tropical
  cyclone can do:  Cyclone Tracy, which practically obliterated the city
  of Darwin in December, 1974.  According to information received from
  Jeff Callaghan, Tracy's gale radius was only about 18 nm.  Other very
  small but intense tropical cyclones which have struck Australia were
  Kathy (1984) with a gale radius of 35 nm, and Ada (1970) with a gale
  radius of 30 nm.   And as Matthew Saxby pointed out, Tropical Cyclones
  Steve (2000) and Rona (1999), both of which caused significant damage,
  were midgets.

     The most intense hurricane known to strike the United States during
  the past century-and-a-half was also a very small tropical cyclone.
  The famous Labor Day Hurricane which struck the Florida Keys in 1935
  produced the lowest pressure ever recorded on land in the Western
  Hemisphere:  892 mb.  (The only lower measured pressure in an Atlantic
  hurricane was the 888 mb reading obtained from a dropsonde in the eye
  of Hurricane Gilbert in September, 1988.)   The 1935 hurricane caused
  incredible structural damage, especially to the trestles and bridges
  of Henry Flagler's railroad to Key West.  Engineers have estimated that
  winds from 175 to 220 kts would have been required to have caused some
  of the observed damage.  According to Rich Henning, the gale radius
  of that hurricane was on the order of 25-30 nm.      The eye passed
  through the middle Keys but neither Miami nor Key West reported gale
  force winds.  Over 400 persons died in the hurricane.     Many were
  literally sandblasted to death and found with no skin and no clothes
  except for belt and shoes.  (The last sentence found in Dunn & Miller's
  _Atlantic Hurricanes_.)

     None of the responses I received were in favor of an arbitrary size
  criterion.  David Roth wrote: "Midget phases of a tropical cyclone's
  life should be treated as just that--a phase they occasionally go
  through."  Chris Landsea and Jack Beven both suggested some criteria
  that might be applied to extremely small systems.  Chris suggested that
  a very small system should have some persistence, lasting at least a
  day or two.  If the system is (as Chris put it) "a flash-in-the-pan, it
  may be that it was more of a mid-tropospheric mesoscale convective
  vortex and not a true tropical cyclone."

     Jack was the only person who suggested any spatial dimensions that
  might be considered for defining a tropical cyclone.  He writes: "My
  view is that the smallest size of a tropical cyclone would be something
  somewhat larger than a mid-western supercell mesocyclone--roughly
  10-20 nm or so in diameter.  I think the tropical cyclone has to be
  large enough that the circulation is driven by multiple convective
  cells, as would be the case if an eyewall or spiral band is present."

     So, in summary, it appears that there is a consensus that size
  should not be a criterion in defining a tropical cyclone.  For the
  June Feature I'll try to tackle synopsizing the opinions I received
  on the subject of subtropical/hybrid cyclones, for which there does
  not exist a general consensus regarding how to classify such systems.

                           ACTIVITY BY BASINS

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

  Activity for May:  1 possible subtropical cyclone

                   Atlantic Tropical Activity for May

     No tropical cyclones formed in the month of May in the Atlantic
  basin, which is typical.  Since 1886 twelve tropical storms have been
  tracked in the Atlantic basin during May, three of which reached
  hurricane intensity.  The last May tropical storm was Arlene in 1981,
  and the last hurricane in May was Alma in 1970.  Several other years
  have seen tropical depressions or subtropical systems develop during
  May.      In May of 2001, a low-pressure area formed along an old
  stationary front on the 5th in the Bahamas, roughly 200 nm north of the
  extreme eastern tip of Cuba, and moved east-northeastward.  By late on
  the 5th convection had wrapped around the eastern and northern
  quadrants of the LOW.   By the morning of the 6th, the cyclone had an
  occluded appearance with sporadic convection just north and well to the
  east of the center due to dry air wrapping around its south side.
  Later on the 6th and into the 7th, the center became devoid of
  convection and the low-level swirl drifted southwestward as its 
  upper-level circulation warmed and weakened.

     Late on the 5th and throughout the 6th, this cyclone was not
  connected to any frontal cloudiness on satellite imagery.  That fact,
  plus the fact that convection was close to the center on the 5th and
  6th, led to the conclusion that the LOW was very possible subtropical
  in nature.

     Temperature gradient was minimal at best around the system, though
  it had a decent dewpoint contrast.  Most of the high winds were north
  and west of the center in the Bahamas and southwest Atlantic in a
  region of good pressure gradient between the LOW and a HIGH in the
  eastern U. S.   A cold front dropped in from the north late on the 7th
  and early on the 8th, spawning a new area of low pressure which swept
  this cyclone to the east, absorbing it during the morning on the 8th.

     A track for this system follows.  Since this was not a tropical
  cyclone, I am not going to add the track to the May tracks file and
  re-distribute that, but I will include it in the cyclone tracks file
  for June.   All the information and the track for this system was 
  supplied by David Roth of the Hydrometeorological Prediction Center in
  Maryland.  A special thanks to David for providing the information.


  Storm Name: None                  Cyclone Number: None    Basin: ATL
  (Possible subtropical storm--track supplied by David Roth.)
     Date   Time   Lat      Lon    Cent  MSW   MSW        Remarks
            (GMT)                 Press 1-min 10-min
                                   (mb) (kts) (kts)
  01 MAY 05 0600  23.0 N   74.0 W  1008   20
  01 MAY 05 1200  23.2 N   72.9 W  1007   25
  01 MAY 05 1800  23.8 N   72.2 W  1007   30
  01 MAY 06 0000  24.8 N   71.7 W  1007   30
  01 MAY 06 0600  25.2 N   71.0 W  1006   30
  01 MAY 06 1200  25.0 N   70.2 W  1005   30
  01 MAY 06 1800  24.5 N   70.1 W  1004   35
  01 MAY 07 0000  24.0 N   71.0 W  1004   40
  01 MAY 07 0600  24.0 N   69.8 W  1005   45
  01 MAY 07 1200  24.2 N   68.8 W  1005   45
  01 MAY 07 1800  24.5 N   67.9 W  1006   45
  01 MAY 08 0000  25.2 N   67.3 W  1006   45
  01 MAY 08 0600  26.0 N   67.0 W  1006   40

  Note:  The winds and pressures used were based on ship reports and
  analyses prepared by HPC and MPC.  Note that the maximum sustained
  winds held constant at gale force until dissipation due to the
  formation of another LOW to its north.  Errors on the center location
  should be between 30 and 60 nautical miles.


  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 Tropical Activity for May

     Over the thirty years from 1971-2000, the first tropical storm of
  the season in the Northeast Pacific basin has developed in May thirteen
  times, or in 43% of all seasons.   The first hurricane, however, has
  formed in May on only 7 occasions, or 23% of the time.   The first
  intense hurricane (i.e., reaching Category 3 or higher on the Saffir/
  Simpson scale) had never formed in May since the advent of satellites.
  The year 2001 changed that statistic:  Hurricane Adolph became the
  first Category 3 Eastern Pacific hurricane on record on 28 May when
  its MSW reached an estimated 105 kts--24 hours later Adolph had become
  the first May Category 4 hurricane on record in the North Pacific east
  of the Dateline.  Very fortunately for the Mexican coastline, Adolph
  remained at sea with only rainbands and heavy surf affecting the coast.

     The summary on Adolph following was written by John Wallace of San
  Antonio, Texas.  A very special thanks to John for his assistance.

                         Hurricane Adolph  (TC-01E)
                               25 May - 2 June

  A. Origins

     The tropical LOW that became Adolph formed along the axis of a
  tropical wave, one that lingered in the Pacific west of Central
  America for several days.  Indeed, the UKMET had forecast tropical
  storm development there as early as the 20th, long before there was
  any hint of cyclogenesis.  The progenitor disturbance organized
  slowly but surely, and the JTWC/NPMOC issued a TCFA for the LOW at
  0200 UTC on the 25th.     Visible satellite imagery, along with
  scatterometer data, supported the LOW's upgrade to Tropical Depression
  One-E at 2100 UTC on 25 May.     At this time it was located roughly
  200 nm south-southwest of Acapulco, Mexico.

     Though conditions were favorable for intensification, One-E was
  slow to strengthen; it did not become a tropical storm for a full day
  after the first advisory was issued.    The center was occasionally
  difficult to pinpoint, and the depression's organization waxed and
  waned.  Nevertheless, One-E was upgraded to Tropical Storm Adolph at 
  2100 UTC on 26 May, located roughly 175 nm south-southwest of Acapulco.
  It was then that Adolph's previously humble existence made a dramatic

  B. Track and Intensity History

     Adolph intensified swiftly after its upgrade, reaching hurricane
  strength only 24 hours later, at 2100 UTC on 27 May, some 185 nm
  south of Acapulco.   It attained a 105-kt MSW just six hours later.
  Adolph initially deepened at an impressive rate:  1.46 mb per hour,
  between its upgrade and 0300 UTC on the 28th.     Intensification
  continued until Adolph reached its peak MSW of 125 kts at 0300 UTC
  on 29 May with an estimated CP of 940 mb.    At this time it was 
  located roughly 200 nm south-southwest of Zihuatanejo, Mexico.  Adolph
  had a well-defined eye, and its cold CDO began to take on a so-called
  "buzzsaw" appearance characteristic of very strong hurricanes.
  According to the NHC, raw Objective Dvorak Numbers were as high as
  T7.0, which is equivalent to a MSW of 140 kts.     An SSMI pass at
  0416 UTC on the 29th clearly depicted a pair of concentric eyewalls.
  Adolph maintained its peak intensity for roughly eighteen hours.

     The cyclone, which had been previously meandering southeastward,
  began a turn to the north, then west-northwest, beginning late on
  the 27th.  A mid-level ridge to its north built eastward, finally
  providing a steady steering current and a moderate rate of motion.
  Adolph was at first a slow-mover; at 1500 UTC on the 28th, some three
  days after the first advisory, Adolph was only 51 nm from its first
  warning position.  That being said, the change in its track warranted
  the issuance of watches and warnings for the Mexican coast.  A tropical
  storm warning and a hurricane watch were issued for the coast at
  0300 UTC on the 28th, extending from Acapulco westward to Lazaro
  Cardenas.  The hurricane watch was dropped at 2100 UTC on the 28th,
  though Adolph continued to roughly parallel the coast.  The tropical
  storm warning was dropped on the next advisory, at 0300 UTC on the
  29th, as Adolph reached peak intensity.

     A slow weakening trend began at 2100 UTC on the 29th, though outflow
  remained good.      At first, the weakening was due to an eyewall
  replacement cycle; soon after that, though, cooler SSTs along the
  storm's track began to take their toll.   Adolph's cloud tops warmed,
  and convection decreased in areal extent; by 1500 UTC on the 30th the
  MSW had dropped below 100 kts.  Stable air-entrainment exacerbated the

     The cyclone assumed a more westward track on the 31st, and its
  deterioration accelerated.   The slight track change was no doubt due
  to the increasing influence of low-level winds from a ridge to its
  north.  The cyclone passed about 125 nm south of Socorro Island around
  1500 UTC on 31 May at minimal hurricane intensity, then, by 2100 UTC,
  Adolph had weakened to tropical storm strength and its forward motion
  had decreased.  Ship reports suggested that the storm's circulation was
  becoming distorted.  At 2100 UTC on 1 June the convection-free vortex
  was downgraded to a depression.     The last advisory on Tropical
  Depression Adolph was issued at 0300 UTC on 2 June when it was located
  500 nm west-southwest of Manzanillo.   A remnant swirl of low clouds
  persisted for a few days thereafter.

  C. Historical Tidbits

     Adolph was far and away the most intense May hurricane on record in
  the Northeast Pacific basin.    It is interesting to note that the
  previous recordholder for May was also a hurricane named Adolph back
  in 1983.  The earlier Adolph peaked at 95 kts.    And while on the
  subject of hurricanes named Adolph, the previous Hurricane Adolph, in
  1995, reached a peak intensity of 110 kts, but that storm occurred in
  mid-June.    This is also only the second time since 1971 that there
  have been two consecutive Northeast Pacific seasons with May hurricanes
  (2000-01, and 1983-84).

  D. Damage and Casualties

     Though rainbands from Adolph occasionally impinged on the Mexican
  coast--to say nothing of heavy surf--no casualties or damage are known
  to the author.


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

  Activity for May:  1 tropical depression **
                     1 tropical storm

  ** - No warnings were issued on this system by any warning center.
       The track and intensity estimates were provided by Roger Edson
       of the University of Guam, formerly a forecaster with JTWC.

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

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

               Northwest Pacific Tropical Activity for May

     The first named tropical storm of 2001 in the Northwest Pacific
  formed in mid-month in the South China Sea from a depression which had
  earlier trekked westward across the central Philippines from the
  Philippine Sea.   While Cimaron was the first tropical storm to form
  in the current year, it was not the first storm on the charts.  Back in
  early January Tropical Storm Soulik from late December, 2000, after
  weakening, suddenly flared up and became a rather intense, albeit
  brief, typhoon east of the Philippines.   A report on Tropical Storm
  Cimaron is given below; however, there were a couple of other systems
  that warrant mention.

     Roger Edson forwarded me a track he'd generated for a tropical
  depression east of the Philippines.  A very weak LOW was located far to
  the south of Yap on 16 May.     The system drifted generally north-
  northwestward over the next couple of days, reaching a point about
  100 nm north-northeast of Palau by 1200 UTC on 18 May.    The STWO
  issued by JTWC at 18/0600 UTC mentioned the disturbance, which,
  according to Roger's track, likely had maximum winds of about 20 kts
  at the time.  The STWO for 19 May upgraded the development potential
  to fair, and a Formation Alert was issued at 20/0100 UTC as convection
  was beginning to increase near the LLCC and a 200-mb analysis indicated
  diffluent flow aloft.  The system by this time was moving northward
  a few hundred miles east of the Philippines, passing about 350 nm east
  of Catanduanes Island around 0000 UTC on the 21st, when, according to
  Roger's track, the peak intensity of 30 kts was reached.  A second
  Formation Alert was issued by JTWC at 21/0100 UTC, but by 22/0000 UTC
  the system was weakening and becoming extratropical about 500 nm east
  of the northern tip of Luzon.  (Roger's track for this system was
  included in the cyclone tracks file for May.   A special thanks to
  Roger for sending me the information on this system.)

     The other disturbance formed in the South China Sea off the coast of
  Vietnam on 14 May.  By 0600 UTC on the 15th a broad, fully-exposed LLCC
  was located about 170 nm southeast of Da Nang with convection sheared
  away toward the west.  The system moved north-northwestward, roughly
  parallelling the Vietnamese coast.  JTWC issued a Formation Alert at
  1130 UTC on 16 May when the center was estimated to be about 140 nm
  northwest of Da Nang.  Convection was increasing near the LLCC and the
  LOW was located in an environment of weak vertical shear with good
  outflow aloft.  However, by 17/0530 UTC the system had moved onshore
  just east of Nam Dinh, Vietnam, so the Formation Alert was cancelled.
  The Central Weather Bureau of Taiwan did refer to this disturbance
  as a tropical depression in one of their bulletins--none of the other
  agencies classified it as a depression.  (No track for this system was
  included in the cyclone tracks file for May.    Huang Chunliang of
  Fuzhou, China, informed me that the Central Weather Bureau had
  classified this system briefly as a depression--thanks to Chunliang
  for alerting me to this fact.)

           Tropical Storm Cimaron  (TC-03W / STS 0101 / Crising)
                                7 - 21 May

  Cimaron: contributed by the Philippines, is the name of a Philippine
           wild ox

  A. Origins

     A STWO issued by JTWC at 1430 UTC on 4 May mentioned that a weak
  LLCC had developed in the monsoon trough about 40 nm south of Koror.
  A 200-mb analysis showed diffluent, moderate easterlies over the area.
  By the next day the disturbance had migrated (or re-formed) farther to
  the west to a position approximately 160 nm southeast of the Philippine
  island of Mindanao.  A SSM/I pass revealed deep convection but a broad,
  weak LLCC; by 6 May the area was centered on the southern coast of
  Mindanao.   JTWC issued a Formation Alert at 1200 UTC, relocating the
  center farther northward along the east coast of Mindanao.  The LLCC
  was accompanied by persistent convection which was displaced to the
  north, and the system lay under weak to moderate upper-level easterlies
  on the equatorward side of a ridge of high pressure.

     JTWC issued the first warning on TD-03W at 07/0000 UTC, locating
  the ill-defined center about 75 nm east of the northern tip of
  Mindanao.  The MSW was estimated at only 20 kts, based on satellite
  CI estimates of 25 kts, coastal synoptic reports of 10 kts, and a
  ship report of 20 kts.  By 1800 UTC the depression was centered in the
  Leyte Gulf region, and over the next couple of days tracked west-
  northwestward across the central Philippines.    At 08/1800 UTC, based
  on a synoptic analysis, the center was relocated about 73 nm south-
  southwest of the previous warning position to a point 160 nm southeast
  of San Pablo.  At 0000 UTC on 9 May the depression's center was in the
  Sulu Sea, and by 1200 UTC had emerged into the South China Sea proper.
  During its trek across the Philippines the MSW remained set at 25 kts,
  though on an occasion or two CI estimates of 30 kts were received.

     The winds were upped to 30 kts at 09/0600 UTC when TD-03W's center
  was emerging into the South China Sea about 170 nm south-southwest of
  Manila.  After moving out into the South China Sea, the system turned
  northward off the west coast of Luzon.  CI estimates had reached 35 kts
  at 1800 UTC, but the MSW remained at 30 kts for that warning.  However,
  at 0000 UTC on the 10th, JTWC upgraded TD-03W to a tropical storm with
  35-kt winds (based on CIs of 35 and 45 kts) located 125 nm west-
  southwest of Manila.   Also at 10/0600 UTC, PAGASA issued their first
  warning on the system as a tropical depression, naming it Crising (a
  Filipino nickname).  It is very interesting that PAGASA didn't initiate
  warnings on 03W/Crising until it had reached tropical storm intensity
  per JTWC analysis, especially considering that it had trekked across
  the central part of the archipelago.    Normally, with systems in the
  vicinity of the Philippines, PAGASA is the first agency to issue
  bulletins.     JMA upgraded 03W/Crising to a tropical depression at
  10/0600 UTC.

  B. Track and Intensity History

     JTWC increased the MSW to 40 kts at 10/1200 UTC, but the intensity
  held steady at that level for 24 hours.  Tropical Storm 03W/Crising
  moved slowly northward roughly 100 nm off the west coast of Luzon
  for about 36 hours until it turned more to the north-northeast at
  11/1200 UTC.   PAGASA and JMA upgraded the system to a tropical storm
  at 11/0000 UTC with JMA assigning the name Cimaron.  The newly-named
  storm was then located about 70 nm west of Lingayen.  Satellite-derived
  CI estimates had reached 45 kts, but based on synoptic reports, JTWC
  held the MSW to 40 kts; JMA and PAGASA were estimating 35-kt 10-min
  avg winds.   At 1200 UTC on the 11th JTWC increased the MSW estimate
  to 45 kts; at 1800 UTC the center was relocated slightly to the south
  of the 1200 UTC position and was moving slowly north-northeastward.

     By 12/0000 UTC Tropical Storm Cimaron/Crising was located about
  85 nm north-northwest of Port San Esteban and moving to the northeast
  at 4 kts.  The storm appeared to have weakened some over the previous
  twelve hours due to increased vertical shear.  Water vapor imagery
  showed the system to be interacting with a frontal boundary, and the
  cyclone was located poleward of an upper-level ridge axis in a region
  of moderate to strong vertical shear.   At 0600 UTC JTWC decreased the
  MSW to 40 kts, based on CIs of 30 and 45 kts.  By 1200 UTC the storm's
  center was about 105 nm north-northwest of Port San Vicente and moving
  northeastward at a slightly faster pace (12 kts).    The weakening
  trend noted earlier proved to be temporary and at 1800 UTC the winds
  were increased once more to 45 kts with the storm in the Bashi Channel
  about 30 nm west of Itbayat Island.    However, Cimaron was already
  beginning to show the first hints of what turned out to be a slow,
  prolonged transition into an extratropical cyclone.

     As Cimaron continued to slowly accelerate northeastward, passing
  a short distance southeast of the southern tip of Taiwan and into the
  southern Ryukyus, it continued to increase in intensity, reaching a
  peak of 60 kts at 1800 UTC on 13 May when it was centered about 25 nm
  south-southwest of Miyakojima Island.   Vertical shear had weakened
  slightly and an upper-level jet stream to the north of the cyclone had
  helped to create an outflow channel to the northeast of the center.
  Cimaron was being steered northeastward by a low- to mid-level ridge
  to the southeast, and its forward motion gradually accelerated with
  the approach of a mid-latitude trough from the northwest.

     The cyclone was located about 80 nm southwest of Naha, Okinawa, at
  0000 UTC on 14 May, moving northeastward at 17 kts.  The estimated MSW
  was down slightly to 55 kts (based on CIs of 55 and 65 kts), and the
  convection was beginning to decouple from the LLCC with a partially-
  exposed center evident about 15 nm southwest of the deepest convection.
  The center of Cimaron passed over Okinawa around 14/0600 UTC with peak
  winds estimated at 45 kts, and by 1200 UTC the storm had become extra-
  tropical about 115 nm northeast of the island.   The remnants of former
  Tropical Storm Cimaron continued as an extratropical gale for another
  week, initially moving east-northeastward through 17 May, then curving
  more to the northeast, reaching the vicinity of 160E by 19/0000 UTC.
  Thereafter, the LOW turned generally northward and moved slowly up
  the 160th meridian, being last mentioned (in JMA High Seas bulletins)
  as a separate entity at 21/0000 UTC near 45N, 158E.

  C. Meteorological Aspects

     As stated in the discussion above, JTWC intensity estimates were
  frequently based in part on synoptic reports from the Philippines and
  ships, but the details of those were not given.  At the time Cimaron
  reached its peak intensity of 60 kts, Miyakojima Island (WMO 47927),
  located about 25 nm to the northeast of the center, reported a 1-min
  avg sustained wind of 39 kts.    As the cyclone crossed Okinawa, Naha
  Airport (WMO 47936) reported a maximum 10-min mean wind of 30 kts.
  (The MSW at that time was estimated at 45 kts by both JTWC and JMA.)

     As Tropical Storm Cimaron/Crising passed near northwestern Luzon,
  Basco recorded 305 mm of rain in 48 hours (the monthly average is
  129 mm).    Also, Lan Yu, a small island located off Taiwan's south-
  eastern coast, recorded 262 mm of rain in 48 hours. (At 13/0000 UTC
  Cimaron's center was about 36 nm south-southeast of Lan Yu.)  These
  rainfall observations were forwarded to the author by Patrick Hoareau;
  a special thanks to Patrick for sending them.  Unfortunately, the
  exact dates/times of the relevant 48-hour periods are not available.

  D. Comparisons between JTWC and Other Centers

     As noted above, Cimaron was one of the rare cases where JTWC "jumped
  the gun" on PAGASA as far as initiating tropical depression warnings 
  was concerned.      However, after PAGASA and JMA had begun issuing
  warnings on the system, the estimated intensities by those agencies
  compared rather well with JTWC's MSW.  JMA's bulletins did not reflect
  the slight weakening reported by JTWC on 12 May, but the peak winds
  reported by the two centers--60 kts from JTWC and 50 kts (10-min avg)
  from JMA--were in excellent agreement.   During the system's early
  stages as a tropical storm, there were some differences in center
  position estimates between the various agencies' warnings, but from
  11/1200 UTC onward the coordinates were in remarkably good agreement.

  E. Damage and Casualties

     In spite of the heavy rainfall (and likely associated flooding)
  reported on northern Luzon, the author has been unable to locate any
  reports of significant damage or fatalities resulting from Tropical
  Storm Cimaron/Crising.


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

  Activity for May:  1 tropical cyclone of hurricane intensity

  NOTE:  The tracking and intensity information for North Indian Ocean
  Basin tropical cyclones is based primarily upon operational warnings
  from the Joint Typhoon Warning Center of the U. S. Air Force and Navy
  (JTWC) at Pearl Harbor, Hawaii.  Occasionally some information may
  be gleaned from the daily Tropical Weather Outlooks and other bulletins
  issued by the Indian Meteorological Department (IMD), which is the 
  WMO's RSMC for the basin.
     The MSW are based on a 1-min averaging period, which is used by
  all U. S. civilian and military weather services for tropical cyclone
  warnings.  For synoptic observations in the North Indian region,
  both 10-min and 3-min average winds are employed, but IMD makes no
  attempt to modify the Dvorak scale for estimating tropical cyclone
  intensity; hence, a 1-min avg MSW is implied.  In the North Indian
  basin JTWC usually does not initiate warnings until a system is
  well-organized and likely to attain tropical storm status within
  48 hours.

               North Indian Ocean Tropical Activity for May

     The first officially-declared tropical cyclone of 2001 in the North
  Indian Ocean basin developed in May in the Arabian Sea off the west
  coast of India and became one of the most, if not the most, intense
  cyclones on record in that region.  Fortunately, the cyclone remained
  at sea and eventually weakened, sparing India what could have been a
  great disaster.   In addition to writing the summary for Hurricane
  Adolph, John Wallace also wrote the summary for Tropical Cyclone 01A,
  and again, a big thanks to John for his help.  (See the March and April
  summaries for discussions of two weaker systems which Roger Edson feels
  qualified as tropical storms in the eastern Bay of Bengal.)

                        Tropical Cyclone  (TC-01A)
                                21 - 28 May

  A. Origins

     The origin of TC-O1A can be traced back to a disturbance in the 
  western Arabian Sea that was apparently first noticed on 18 May.
  A Tropical Weather Advisory issued at 1800 UTC on 19 May centered the
  disturbance east of the Yemeni island of Socotra and mentioned that
  it was quasi-stationary.  Though it generated strong convection, the
  disturbance was amorphous with no closed circulation.  There seemed
  to be no reason to suspect that it had anything other than meager 
  prospects for development.

     On the 20th the situation improved for the disturbance, initially 
  situated southwest of an upper-level trough, as an upper-level
  anticyclone developed over the system, providing good outflow.  Though
  there was still no synoptic evidence of a closed circulation, there
  were the first definite hints of cyclonic structure in satellite
  imagery.  The disturbance began a slow eastward track.

     By 1800 UTC on the 21st, the JTWC Tropical Weather Advisory
  indicated that a closed mid-level circulation had developed as the
  disturbance turned slightly north of east.  Convection remained strong,
  and the disturbance's satellite presentation continued to improve.
  A surface circulation began to develop, and the JTWC issued a Formation
  Alert for the LOW at 0730 UTC on 21 May; the IMD first took notice of
  the disturbance at roughly the same time.   The JTWC issued the first
  warning on Tropical Cyclone 01A at 1800 UTC on 21 May when it was
  located about 350 nm south-southwest of Mumbai (Bombay).  Convective
  banding was developing in the cyclone's western semicircle and the
  system's organization was impressive.  Located in a highly favorable
  environment, the stage seemed set for significant strengthening.  Such
  was the case.

  B. Track and Intensity History

     Intensification was initially rapid; TC-01A reached an intensity of
  65-kts (1-min avg) at 1200 UTC on 22 May, just 18 hours after its
  upgrade, while located roughly 280 nm south-southwest of Mumbai.  An
  incipient 12-nm eye was apparent in satellite imagery as early as 
  0600 UTC on the 22nd, twelve hours after its upgrade.   Once the MSW
  reached 65 kts, the intensification rate slowed considerably, though
  it remained steady.  This development coincided with the establishment
  of a ridge over southern India, which provided a southerly steering 
  current.  The northward turn was much more abrupt than forecast,
  sparing west India from a potential disaster.   Storm force winds 
  remained offshore as TC-01A briefly paralleled the coast.  At 0000 UTC
  on the 23rd, the cyclone began a northwestward turn under the influence
  of another mid-level ridge centered over the northern Arabian Sea.  By
  this time TC-01A had developed impressive outflow and intensification

     The MSW reached an estimated 100 kts at 0000 UTC on 24 May, making
  TC-01A only the fourth Arabian Sea cyclone to reach that strength since
  1975.  It is worth noting that three of these four cyclones have formed
  since 1998.  Tropical Cyclone 01A attained a peak MSW of 115 kts at
  0600 UTC on 24 May while centered roughly 250 nm west-southwest of
  Mumbai.  This makes TC-01A the strongest Arabian Sea cyclone since at
  least 1975.  (NOTE:  It's possible that the peak estimated MSW will be
  decreased to 110 kts in the JTWC's final best track, which would only
  tie the previous records.)  The JTWC has traditionally applied the same
  scale used for Northwest Pacific tropical cyclones to North Indian
  Ocean cyclones; using this same wind-pressure relationship results in 
  an estimated CP of 916 mb for TC-01A at peak intensity.  However, this
  is pure conjecture; it's clear that the MSW is of primary importance
  in Dvorak analysis.

     The cyclone maintained its peak MSW for 18 hours; during this time
  the system presented a formidable satellite appearance, with an eye
  that was initially well-defined.      However, the eye soon became 
  indistinct as conditions became suddenly hostile.  Easterly winds south
  of the upper-level ridge axis, in conflict with low- to mid-level
  westerlies, created substantial shear which began to rend the cyclone
  apart; its circulation was distorted and its convection weakened.  This
  set the pattern that would continue for the rest of TC-01A's duration.
  Its forward speed decreased, and the cyclone became quasi-stationary on
  the 25th; a slow northward track commenced at roughly 1200 UTC on
  26 May under the influence of a low- to mid-level ridge over India.

     Tropical Cyclone 01A weakened rapidly beginning at 0000 UTC on the
  25th with the MSW dropping below 100 kts at 0600 UTC.  At 0600 UTC on
  26 May, just 24 hours later, it weakened to tropical storm strength
  while located about 300 nm west-southwest of Mumbai or 475 nm south-
  southeast of Karachi, Pakistan.  The weakening trend slowed thereafter
  but did not stop.    The final advisory on the cyclone was issued at
  1800 UTC on 28 May with the center located some 175 nm west-northwest
  of Veraval.  By this time TC-01A was a spiral of low clouds, devoid of
  deep convection.  The cyclone's remnants made landfall in Gujarat on
  the 29th; unfortunately, no weather observations from the area were
  available to the author.

  C. Damage and Casualties

     The weakening and dissipation of Tropical Cyclone 01A came as a
  godsend to the province of Gujarat, still reeling from a deadly earth-
  quake in January.  On top of that, local news agencies indicated that
  some communities were still living in the shadow of damage from 1998's
  TC-03A.  That being said, the national and local governments mounted
  extensive and swift preparations for TC-01A's possible landfall.
  Kandla Port, one of the busiest in India, was closed for about four
  days.  As many as 118,000 people were evacuated from coastal regions
  in India while another 50,000 were evacuated from high-risk areas of

     Casualty and damage information for the cyclone is either sparse
  or vague.  Two hundred houses were washed away in two coastal villages
  on the 24th at Kosamba in the Valsad district.  This is the only known
  damage on land.  As for casualties, anywhere from 120 to as many as
  900 fishermen were declared missing on the 24th according to local
  news reports.


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

  Activity for May:  No tropical cyclones



  Activity for May:  No tropical cyclones


  Activity for May:  No tropical cyclones


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

  Activity for May:  2 tropical depressions **

  ** - Both systems were hybrid, cold-cored systems rather than true
       tropical depressions.

     Most of the information presented below was taken from the
  operational warnings and advisories issued by the Fiji TCWC at Nadi.  
  References to sustained winds imply a 10-minute averaging period
  unless otherwise noted. 

                  South Pacific Tropical Activity for May

     No named tropical cyclones formed in the South Pacific during May,
  but gale warnings were issued on two depressions, neither of which were
  tropical in nature, but rather were cold-cored, hybrid-type systems
  forming under strong shear aloft.  The forecast gales were expected
  to develop in the systems' southern semicircles due to gradient
  compression as the LOWs moved into a strong ridge to the south.  The
  first depression (14F) formed on 1 May about 225 nm west-northwest of
  Rarotonga, initially moved eastward, passing about 50 nm north of the
  island around 01/1800 UTC, and later accelerated off to the southeast.
  The final warning available to the author, issued by Wellington at
  03/1200 UTC, placed the center about 550 nm southeast of Tahiti.  The
  second depression (15F) formed on 7 May about 250 nm west-southwest of
  Tahiti, moved initially southward, then southeastward with the final
  warning issued by Fiji, at 09/1200 UTC, placing the center roughly
  400 nm south-southwest of Tahiti.

                              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 the May, 2001
  summary is shorter than average, I've appended the Glossary to the
  end 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: []
       (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:   may01.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:  may01.sum, for

    Back issues can also be obtained from the following websites
  (courtesy of Michael Bath, Michael V. Padua, Tom Berg, Michael
  Pitt, and Rich Henning):>> 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 2000 (1999-2000 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 2000 Atlantic and Eastern North Pacific
  tropical cyclones; also, preliminary storm reports for all the 2000
  Atlantic and Eastern North Pacific cyclones are now available, as
  well as track charts and reports on storms from earlier years.

     The URL is:>

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



  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,

  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

  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

  TC -      tropical cyclone

  TCFA -    Tropical Cyclone Formation Alert - issued by JTWC when a
            tropical cyclone is expected to develop within the next
            24 hours

  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,

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

Document: summ0105.htm
Updated: 29th December 2006

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