[Index]
Monthly Global Tropical Cyclone Summary June 2000
[Summaries and Track Data] [Prepared by Gary Padgett]
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Cyclones
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Monthly Global Tropical Cyclone Summary June 2000 [Summaries and Track Data] [Prepared by Gary Padgett] |
MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
JUNE, 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.)
***********************************************************************
JUNE HIGHLIGHTS
--> Very intense Eastern Pacific hurricane threatens Mexican coast
--> Rare June depression forms in Cape Verde region
--> Overnight midget cyclone strikes Hong Kong
***********************************************************************
NEW FEATURE - TOPIC OF THE MONTH
Last month I began adding 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 June *****
A SOURCE FOR STATE AND LOCAL HURRICANE HISTORIES
Back when I was a teenager in the mid-1960s, I began collecting
brochures and books on tropical cyclones as well as annual tracking
charts of the previous year's Atlantic storms. One publication I
ordered fairly early on was entitled "NORTH CAROLINA HURRICANES - A
Descriptive Listing of Tropical Cyclones Which Have Affected the
State" by Albert V. Hardy and Charles B. Carney. This little booklet
quickly became one of my favorites. So much historical hurricane
information was in the form of tables and maps, but here was something
refreshingly different: narrative descriptions of significant tropical
cyclones which had affected the state, taken from old newspapers and
other sources. Much information was given on damage and casualties,
measurements of wind velocity, marine disasters, general comments
about the known history of the storm, etc. I read and re-read the
booklet many times. A few years later, after beginning my employment
at Eglin AFB, Florida, I obtained a copy of a Hurricane Brochure which
had been published by the base Disaster Preparedness Office. This was
a similar sort of compilation of tropical cyclones which had affected
the western portion of the Florida Panhandle.
A few years ago I discovered a website where several such state and
local hurricane histories can be accessed, and I thought I would pass
along the information for the benefit of those persons who enjoy
reading descriptions of historical storms. These can be accessed
from Eric Blake's Atlantic Tropical Weather Center, for which the URL
is: http://www.atwc.org> . Click on the link "Other Hurricane Info"
(on the left). The line containing links to the various hurricane
histories appears about halfway down the screen. Several of these
were compiled and written by David Roth, a graduate of Florida State
University who worked for four years at the Lake Charles WFO and is
now employed at the Hydrometeorological Prediction Center in Maryland.
I had the pleasure of meeting David, along with Eric, at the recent
AMS tropical meteorology conference in Ft. Lauderdale. Another of the
histories is an expanded and updated version of the aforementioned
Northwest Florida storms brochure by Rich Henning, a member of the 53rd
Weather Reconnaissance Squadron (Hurricane Hunters) and a Staff
Meteorologist at Eglin AFB.
The North Carolina hurricane history by James D. Stevenson is an
expanded and updated work which incorporates much of the material from
the earlier publication by Hardy and Carney. The list also includes
a history of hurricanes in southeastern Texas by Joshua Lichter, one
for the Savannah, Georgia, area by Patrick Prokop, the histories for
Louisiana and Texas by David Roth, and one for the state of Virginia
co-authored by David Roth and Hugh Cobb from the WFO in Wakefield,
Virginia. Another item which may be of interest to many is a
re-analysis of the Great Gale of 1878, a hurricane which swept out of
the Caribbean in late October and up the U. S. Eastern Seaboard, and
which was rather deadly and destructive in Virginia. This study was
performed by David Roth and Hugh Cobb and was presented as a paper by
David at the recent Ft. Lauderdale conference. The URL for this
paper is:
http://www.hpc.ncep.noaa.gov/research/roth/galeof78.html>
Another interesting tropical cyclone historical paper I stumbled
across was a re-analysis of the intense Georgia hurricane of 1898
by Al Sandrik and Brian Jarvinen. Al, the Lead Forecaster at the
Jacksonville WFO, is another person whom I had the pleasure of meeting
at the AMS conference. The links, first to the full paper, and
secondly to a version submitted for publication, are:
http://www.nwsjax.noaa.gov/research/hurricanes/history/1898/>
http://www.nwsjax.noaa.gov/research/hurricanes/history/1898/
1898_ams_paper/>
At the recent conference Al presented a paper, authored by himself,
Brian Jarvinen, and Chris Landsea, discussing the major hurricane
which struck north Florida on 29 September 1896 and led to very high
winds inland. This study is still in progress and is currently not
available online, but when it is completed I shall report the address
of a URL where it can be accessed.
Next Month's Topic - Some Eastern North Pacific Statistics
***********************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for June: 2 tropical depressions
NOTE: Much of the information presented below was obtained from the
TPC/NHC discussion bulletins issued with every regular advisory. All
references to sustained winds imply a 1-min averaging period unless
otherwise noted.
Atlantic Activity for June
--------------------------
Two tropical depressions formed in the month of June in the Atlantic
basin. The first development was in one of the favored cyclogenetical
areas for June--the southwestern Gulf of Mexico--but the second
depression formed very anomalously in the eastern Atlantic a few
hundred miles southwest of the Cape Verde Islands, becoming the
easternmost June tropical depression on record. Furthermore, the
system appeared quite well-organized and there were several
meteorologists who seemed to feel that the system may have actually
reached tropical storm intensity.
A tropical wave left the coast of Africa on 23 May and moved across
the Atlantic and Caribbean. By 6 Jun the wave was helping to generate
strong convection over the southwestern Gulf of Mexico and the Yucatan
Peninsula. A second tropical wave, first detected in the east-central
Atlantic on 28 May, followed closely on the heels of the first wave
and the two appeared to merge on 7 Jun as a 1009-mb LOW formed in the
Bay of Campeche. NHC classified the LOW as a tropical depression at
2100 UTC on 7 Jun and initiated advisories. At 1800 UTC the poorly-
defined center was located about 275 nm east-southeast of Tampico,
Mexico. An upper-level anticyclone to the south created unfavorable
westerly shear over the depression, thereby inhibiting further
intensification. The system moved very slowly and erratically toward
the west over the next 24 hours. A reconnaissance plane from the
53rd Weather Reconnaissance Squadron of the U. S. Air Force Reserves
investigated the depression around midday on 8 Jun and found that the
system had degenerated into a broad area of low pressure without a
definite center of circulation. A weak remnant area of low pressure
was forecast to drift slowly westward or west-northwestward over the
following 2 or 3 days. A ship (9VBL) located near 22.9N, 95.5W
reported winds to 33 kts at 1400 and 1500 UTC on 9 Jun. Moisture
advected northward from the remnants of the depression lead to several
days of heavy, tropical rain over south-central Texas. (The parent
wave which helped to spawn this depression subsequently moved into
the Eastern Pacific where it was instrumental in the formation of
Tropical Storm Bud.)
Tropical Depression (TD-02)
23 - 25 June
----------------------------
My reason for treating this depression in a separate section is
more to discuss some of the debate which ensued over the system's pre-
depression stage than to describe the meteorological history of the
disturbance. A 1012-mb LOW formed just off the west African coast on
22 Jun and began tracking westward. Although convection was generally
not all that deep, on 23 Jun the system presented a very well-organized
appearance in satellite imagery. However, the system was not upgraded
to a tropical depression at this time since the forecasters at TPC/NHC
were not convinced that a surface circulation existed. The first
advisory on TD-02 was issued at 1500 UTC on 24 Jun when the depression
was located about 500 nm southwest of the Cape Verde Islands. By this
time the system was looking less impressive in satellite imagery than
on the previous day, but the forecaster on duty was convinced that
a surface westerly wind existed south of the center. Some of the
models forecast intensification while others indicated that the
depression would soon dissipate. The latter scenario verified in
this case as visible imagery and cloud wind vectors from CIMSS the
next day indicated that the depression no longer had a closed
circulation. The final advisory was issued at 1800 UTC on 25 Jun
with the system located over 900 nm west-southwest of the Cape Verdes.
SSTs were marginal and the depression encountered more stable air
as it moved westward.
This depression, while short-lived and insignificant, is interesting
in that it is the easternmost tropical depression on record to form in
the month of June. June tropical cyclones are not unknown in the
tropical Atlantic between the Antilles and Cape Verdes--two tropical
storms formed there during the 20th century and others are known to
have formed in earlier centuries--but nonetheless they are very rare
and no June depression has been observed so far east since the advent
of satellites. However, it is very possible that tropical depressions/
tropical storms formed in this area during June in pre-satellite years
and remained undetected. In 1996 Hurricane Bertha formed in the same
general area on 5 July--less than two weeks later into the season.
Mark Lander of the University of Guam supplied a visible satellite
image taken at 23/1800 UTC which depicts a well-organized cloud system.
(This was the day before depression advisories were initiated.) In
Mark's opinion the system warranted a Dvorak rating of a strong T2.5
with winds likely 35-45 kts with a definite indication of westerlies
to the south of the center. A QuikScat image from Roger Edson taken
at 1500 UTC revealed a complete circulation with quite a few wind barbs
of 35-40 kts. (There were three at 50 kts, but the general consensus
was that these were likely too high.) Roger and Mark, along with some
of the researchers at HRD, expressed the opinion that this system was
a tropical storm on 23 Jun. This opinion was obviously not shared
by the forecasters at NHC, although James Franklin has indicated that
in post-storm review the depression stage will quite possibly be
extended back earlier in time.
Most of the disagreement seems to center around the validity of
scatterometer data. Some tropical meteorologists tend to have quite
a great degree of confidence in data from the QuikScat satellite (with
researchers more prone to fall into this camp) while others are more
cautious in accepting the data as "ground truth". Two aspects of the
data seem to have been called into question: (1) whether or not the
existence of a surface circulation is always accurately portrayed, and
(2) whether the reported winds are correct or are subject to rain
contamination. Hopefully, these questions will be resolved in the
near future to everyone's satisfaction, and the day will maybe soon
come when remote sensors will be able to accurately determine the
intensity, physical structure, and thermal characteristics of all
tropical and subtropical cyclonic systems.
Some of the e-mail discussion about this system though brought up
another question: If, in the opinion of the responsible forecaster, a
system does meet all the criteria of a tropical storm, should it be
upgraded and named in all cases, or should a "wait and see" stance be
adopted to see if the system persists? In the specific instance of
eastern Atlantic systems, there have occasionally been monsoon
depressions which have rolled off Africa with well-developed
circulations, and perhaps in a few cases accompanied by gale-force
winds, but which have died as they moved westward out of the monsoon
trough into the tradewind environment--especially true for systems
earlier in the season. For such disturbances NHC has often adopted
the policy of waiting to see if the system maintains itself and shows
signs of strengthening as it moves farther west before upgrading the
system and initiating advisories.
As Mark Lander points out, to "call it like it is" certainly does
a service for shipping in the area, but the forecaster at NHC is ever
conscious of how the U.S. public and media will respond to disseminated
tropical cyclone information. And this is a point to be considered.
It may be difficult for persons outside the U. S. to believe this, but
a 35-kt tropical storm in the far eastern Atlantic can really grab the
attention of the media and public, at least in the eastern and southern
U. S. If a storm is named, and then downgraded only 6 or 12 hours
later, some forecasters feel that many in the media/public will believe
they "cried wolf" and their credibility may suffer. (This is not quite
as much of a problem in the western Atlantic where reconnaissance data,
as well as often radar and buoy data, are available.)
To do a bit of editorializing (which I rarely do)--in the author's
humble opinion, with the increasing public availability of all the
remote sensing data from satellite platforms, the best course of
action is to "call the shots as they are". I believe that it is not
impossible to educate the public and media, without resorting to
language that is too technical, to the point where they can understand
more about the nature of tropical cyclones and will not be surprised
once in awhile if a very brief tropical storm occurs; or will
understand why a future "Perfect Storm" that batters the New England
coastline might later be reclassified as a hurricane and assigned a
name even while it is moving away from the coastline.
***********************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for June: 1 tropical storm
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. The narratives for
Tropical Storm Bud and Hurricane Carlotta were written by John Wallace
of San Antonio, Texas, who also wrote the narrative for Hurricane
Aletta in last month's summary. (A big thanks to John for writing the
the reports and also for the special interest he has in this often
somewhat neglected tropical cyclone basin.)
Northeast Pacific Activity for June
-----------------------------------
Tropical cyclone activity in the Northeast Pacific basin during
June was near normal. Two tropical storms developed with one of
these, Carlotta, becoming a very intense Category 4 hurricane on
the Saffir/Simpson scale. In its early stages Carlotta passed close
enough to the coast of southern Mexico that some watches and warnings
were required for the coastline.
Tropical Storm Bud (TC-02E)
13 - 17 June
----------------------------
The origin of Bud seems to have been an African tropical wave that
tracked off the continent around 27 May. It tracked uneventfully
across the Atlantic for most of the next week, after which it became
tied up in strong convection in the western Caribbean and Bay of
Campeche. In fact, this wave was apparently the progenitor of
Tropical Depression One in the Atlantic. The wave entered the
Eastern Pacific by 8 Jun, where it slowly drifted westward. The
wave generated strong, but sporadic and disorganized, convection
until the 11th, when a tropical LOW developed along the wave axis.
The ragged disturbance slowly organized until a ship report and
satellite analysis warranted upgrading the LOW to Tropical Depression
Two-E at 1500 UTC on 13 Jun about 550 nm south of Mazatlan, Mexico.
The tropical depression tracked west-northwestward under the influence
of a deep-layer ridge to its north.
Two-E was slow to intensify; it was initially under moderate north-
easterly shear from a strong upper-level anticyclone to its north which
kept the mid- and low-level circulations from aligning. The situation
was reminiscent of Aletta's the month before. A ship report from
vessel KAOU of 40-kt winds with a 1001-mb SLP 120 nm northeast of the
center, Dvorak estimates of storm strength from the TAFB and KGWC, and
scatterometer data warranted its upgrade to Tropical Storm Bud by
0300 UTC on the 14th when the center was located roughly 500 nm south-
southeast of Cabo San Lucas on the tip of Baja California. The anti-
cyclone weakened and moved eastward relative to Bud by late on the
14th, lessening the shear. The sheared cloud pattern in fact misled
forecasters; the morning of the 14th showed the tropical cyclone to be
on more of a northwesterly track than originally believed, as the LLCC
was northeast of Bud's strongest convection. The center remained
difficult to pinpoint even in visible imagery, and the track was
adjusted eastward throughout the day on the 14th as the LLCC became
more co-located with the mid-level center. The storm intensified
slightly to 45 kts with a CP of 1000 mb by 1500 UTC on 14 Jun. This
was to be Bud's peak wind intensity, and it was maintained until
2100 UTC on the 15th. However, the pressure was adjusted downward
twice based on synoptic data, and the first time the CP was estimated
to be 995 mb, the lowest value in Bud's lifetime. Bud was a large
storm; storm-force winds and 12-foot seas extended 120 to 150 nm from
the center through most of its time as a storm. Before it was
downgraded, the 12-foot seas radii had expanded to 200 nm while
the wind radii contracted during the onset of the weakening trend.
The cyclone remained relatively unimpressive in terms of
organization as it tracked to the north-northwest. Though upper-level
conditions became more favorable, this positive factor was cancelled
out by Bud's entry into cooler waters. There was conflicting output
about its possible track, and some models suggested that Bud posed a
threat to the Mexican coast--specifically Baja California. The storm
tracked very near Socorro Island at 0900 UTC on 15 Jun; unfortunately,
as with Linda three years earlier, there were no surface data collected
at closest approach, though an upper-air observation taken at 0000 UTC
helped to better determine its intensity. By this time, however, its
convection had already begun a weakening trend. The entrainment of
cooler, more stable air and its track into ever-cooler waters eroded
the tropical storm. The favorable upper-level environment gave Bud a
reprieve, however, and the cyclone's large circulation was slow to spin
down.
Bud was downgraded to a tropical depression at 0900 UTC on 16 Jun
as it became quasi-stationary north of Socorro Island, or about 200 nm
south-southwest of Cabo San Lucas, again reminiscent of Aletta. By
1500 UTC on the 16th, Bud's LLCC was completely exposed--the system
was devoid of deep convection within 60 nm of the center. By 2100 UTC
the cyclone was almost invisible in infrared imagery, although visible
images still showed a well-defined low-level vortex. The final
advisory on Bud, placing the weakening center about 175 nm south-
southwest of Cabo San Lucas, was issued at 1500 UTC on 17 Jun, though
a residual whorl of clouds persisted for several days thereafter.
Moderate, peripheral rains reached the southern Mexican coast, but
whether they were directly related to the storm is debatable. The
rains occurred well outside the radius of tropical storm-force winds,
and most of Bud's convection was displaced west of the center, away
from the coast. The rain may have been as much a result of offshore
convergence, orographic lifting and daytime heating as of Bud's
presence, although the storm's large circulation must be taken into
account. North of Puerto Vallarta the effects were less ambiguous,
and it's certain that rains from Bud affected Cabo San Lucas and the
mainland. Residual moisture advected northeastward from Bud generated
precipitation in Mexico and the American Southwest. No casualties or
damages are known from either rain or surf.
Hurricane Carlotta (TC-03E)
18 - 25 June
----------------------------
Carlotta seems to have originated from a tropical wave that left the
African coast on 8 Jun. However, the wave apparently dissipated as it
crossed Central America well east of where the incipient tropical LOW
that became Carlotta developed. Admittedly though, the data have a
coarse temporal resolution. Another possibility is that Carlotta
developed directly from a convective disturbance on the Pacific ITCZ.
In either case, a tropical LOW formed just east of Central America on
the 16th and tracked slowly west-northwestward. The LOW had a good
cyclonic signature and strong convection from the start, and steadily
organized. A CDO developed on the 18th; this along with ship reports
(and one doubtful report of storm-force winds 50 nm south of the
center) justified its upgrade to Tropical Depression Three-E at
2100 UTC on 18 Jun when it was roughly 255 nm south of Salina Cruz,
Mexico. Its immediate track was northwestward, parallel to the coast.
Three-E's proximity to the coast warranted the issuance of a
tropical storm warning for the Mexican coast from Salina Cruz to
Acapulco. The issuance seemed prudent, as the depression was upgraded
to Tropical Storm Carlotta only three hours after the first advisory,
at 0000 UTC on the 19th, roughly 235 nm south of Salina Cruz. The
upgrade was based on surface and satellite data; the latter showed a
robust tropical cyclone with strong convection. Although light
easterly shear (and perhaps interaction with land) prevented the CDO
from being symmetrical at first, the strongest convection remained
centered over the circulation center, and became more consolidated by
the time of the upgrade. Once upgraded, Carlotta began a relentless
intensification trend with its central pressure falling an average of
0.6 mb per hour for the next 24 hours. A hurricane watch was issued
for the Mexican coast at 0900 UTC on the 19th from Puerto Angel to
Zihuatanejo, while a tropical storm warning remained in effect east of
Puerto Angel to Salina Cruz. Nevertheless, the radii of tropical
storm-force winds remained just offshore; even the impact of rain from
Carlotta's spiral bands was modest with much of the rain that did occur
being unrelated to its presence. Carlotta's track turned slightly
more to the west through the 19th and into the 20th, a development that
was well-forecast as the storm was influenced by a strong mid- to
upper-level ridge to its north. Though the turn lessened the threat
to Mexico, Carlotta remained too close for comfort as it paralleled
the coast.
Carlotta was upgraded to hurricane status at 0000 UTC on 20 Jun,
merely a day after being christened a tropical storm, while 205 nm
west-southwest of Puerto Angel or about 175 nm south-southeast of
Acapulco. A hurricane watch and tropical storm warning were in
effect for the Mexican coast from Puerto Angel to Zihuatanejo, while
warnings east of Puerto Angel were discontinued by 2100 UTC on the
19th. The upgrade was warranted based on the first appearance of a
ragged eye in visible imagery late on the 19th and a classification of
65 kts from KGWC at 2215 UTC that same day. An increase in the area
of deep convection, a persistent warm spot in infrared imagery, and a
consensus among satellite analyses of 65-kt intensity were also taken
into account. Outflow was excellent through most of its southern
semicircle, but restricted elsewhere. Carlotta's intensification
trend, though impressive, was downplayed as its convection weakened
slightly early on the 20th. By 0900 UTC the threat to the Mexican
coast had decreased to the point where the hurricane watch was
discontinued; the tropical storm warning was dropped by 1500 UTC the
same day. Carlotta continued to intensify in the meantime--the
estimated MSW was upped to 75 kts by 0900 UTC and to 90 kts by 1500 UTC
on the 20th. Radar from Acapulco at 0900 UTC showed only a partial
eyewall, but the hurricane had developed a definite 7-nm diameter
eye by 1500 UTC which became increasingly well-defined through the day.
The most interesting developments in Carlotta's life occured late
on the 20th when a rare Eastern Pacific reconnaissance mission
investigated the storm. The Hurricane Hunters found a central pressure
of 977 mb and maximum flight-level winds of 87 kts at 1856 UTC on the
inbound leg of the flight in the northeast quadrant. A GPS dropsonde
deployed later when the plane had reached the west quadrant found mean
boundary layer winds of 106 kts about 200 m above the water and surface
winds of 91 kts a few seconds later. The NHC adjusted the MSW estimate
downward accordingly to 85 kts in the 2100 UTC advisory, a 20-kt under-
shot from satellite estimates. This perhaps wasn't too surprising,
given the great eye presentation and spiral structure apparent on
visible imagery at the time. This discrepancy would become a hot topic
of discussion among certain members of the meteorological community,
a topic which will be discussed in more detail later in the summary.
At the time of the reconnaissance observation, the outflow remained
excellent in the southern semicircle as it improved to the north. Even
as the Hurricane Hunters reported data back to the NHC, Carlotta had
begun a dramatic intensification trend. The central pressure dropped
7 mb in less than three hours between the first and last center fixes
while the winds increased to 96 kts at the surface. Carlotta exploded
in intensity after 2100 UTC, its central pressure dropping 42 mb in
12 hours for a rate of 3.5 mb per hour. In contrast, the minimum
deepening rate required to be considered "explosive" is 2.5 mb per hour
for 12 hours. Carlotta reached its peak intensity at 0900 UTC on
21 Jun; estimated MSW were 130 kts with a CP of 935 mb. The hurricane
was centered about 250 nm south of Manzanillo, Mexico, at this time.
This intensity was maintained until 1500 UTC when a weakening trend
began. During Carlotta's peak, the hurricane's CDO had the classic
"buzzsaw" appearance characteristic of many of the most intense
hurricanes, and a 17-nm diameter eye. The "buzzsaw" is typified by a
sharp-edged and symmetrical CDO with a pinpoint eye and uniform intense
convection. According to an associate, Patrick Hoareau, Carlotta's
130-kt peak makes it the second most intense June Eastern Pacific
hurricane on record, after 1973's Hurricane Ava. (Note: According
to TPC/NHC's monthly summary on their website, the peak MSW for
Carlotta has been increased to 135 kts on 21 Jun, making Carlotta
a very strong Category 4 hurricane on the Saffir/Simpson scale,
almost a Category 5.)
Carlotta slowly weakened through the 21st as it turned slightly
more to the northwest around the periphery of a ridge to its north
and entered cooler waters. Northeasterly shear also began to impinge
on the system, and Carlotta's superb structure and strong convection
deteriorated steadily, as did its eye. The cyclone fluctuated in
intensity on the 22nd; it weakened below major hurricane status (100 kt
or greater winds) at 0900 UTC, re-attained 100 kts at 1500 UTC, and
weakened again to 95 kts by 2100 UTC. Carlotta's forward motion
increased slightly beginning on the 23rd, a day in which various model
outputs suggested the system could pose a threat to Baja California,
though the weakening trend and its small size argued against it. A
trough extending southward from a 500-mb LOW off California was
expected to maintain Carlotta's northwesterly track. Though Carlotta
was on its way out, it maintained hurricane status through the 23rd and
into the 24th. Even in its weakening stage, Carlotta remained
remarkably well-organized, with a persistent, compact CDO that seemed
atypical of a decaying hurricane.
A tropical storm watch was issued for Baja California south of Cabo
San Lazaro at 0900 UTC on the 23rd; Carlotta was 250 nm south of Cabo
San Lazaro at the time with a MSW of 95 kts. The watch proved
unnecessary and was dropped later that day at 2100 UTC, at which time
Carlotta was only a minimal hurricane located about 200 nm south-
southwest of Cabo San Lucas; the system showed no direct indication of
being a threat to the peninsula. Indeed, a 500-mb LOW off southern
California threatened to deflect the cyclone to the east, but it was
considered unlikely that Carlotta would survive long enough for that
to happen.
Carlotta was downgraded to a tropical storm at 0900 UTC on the 24th
as it began a rapid weakening trend over unfavorably cool waters.
Its forward motion decelerated accordingly. By 1500 UTC on the 24th,
all of Carlotta's deep convection was gone, and only the Dvorak
constraints maintained the system. Hints of convective activity early
on the 25th also kept it at tropical storm strength longer than it
might have otherwise been. The LLCC became completely exposed,
resulting in Carlotta's being downgraded to depression status at
0900 UTC on 25 Jun; the final advisory was issued at 1500 UTC the same
day with the center about 450 nm west of Cabo San Lucas. The remnant
low-level vortex slowly drifted westward in the low-level flow for
several days thereafter.
No casualties are known by the author at the present time. Heavy
rains over Mexico on the 18th were apparently unrelated to Carlotta.
Through much of Carlotta's life though, strong ITCZ convection was
advected northeastward into Mexico along its southwest flank. The
impact of these rains is unknown, as is that of the undoubtedly
dangerous seas. Tropical storm-force winds remained offshore
throughout the storm's lifetime. In Acapulco 100 families were moved
out of high-risk areas when Carlotta reached hurricane strength.
Carlotta will be most remembered for the data the reconnaissance
mission collected on the 20th. These highlighted a major discrepancy
between the Dvorak intensity estimates and the in situ measurements by
the Hurricane Hunters. That the Hurricane Hunters caught Carlotta at
the beginning of an explosive deepening trend is not disputed, but
rather, why the two estimates were so at odds. At the time of the
2100 UTC advisory, when the winds were adjusted downward to 85 kts,
satellite intensity estimates were near 100 kts. Less than 30 minutes
after the reconnaissance recorded surface winds of 96 kts, satellite
estimates from KGWC were 115 kts while the University of Wisconsin's
Objective Dvorak Technique (ODT) gave estimates of roughly 135 kts.
At Carlotta's peak satellite intensity estimates were near 140 kts, but
were adjusted downward because of the earlier discrepancy. In fact,
it's possible that Carlotta was much weaker at its perceived peak. The
author considers this unlikely, but the lack of flight data means it
can't be ruled out. There has been speculation that the Dvorak
estimates merely led the actual intensity, and that the reconnaissance
missed the convergence between the two estimates; i.e., the winds
"caught up" with the Dvorak estimates. Another view is that the
satellite estimates were on the money, while another is that neither
the Dvorak estimates nor the flight measurements can be fully trusted
and that the final estimate will be the result of a reasonably
justified judgement call. Carlotta's difficult case also highlights
the "if a tree falls in the forest..." paradox that a lack of flight
and other in situ data causes with respect to storm strength. The
debate is fundamentally about the validity of Dvorak estimates versus
reconnaissance data, a topic which has been a problem for tropical
meteorologists since the technique was devised. Dvorak estimates are
usually in the ball park; such a large deviation is unusual. When
compiled, the official Best Track data will show which side the NHC
falls on.
Note: The monthly summary prepared by TPC/NHC mentions that the
Lithuanian freighter LINKUVA, which lost engine power and was caught
in the hurricane, remained missing at the time the report was prepared
and the crew of 18 are presumed lost.
***********************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for June: 1 short-lived tropical cyclone
Northwest Pacific Activity for June
-----------------------------------
No tropical depressions, tropical storms, or typhoons entered
warning status in the Northwest Pacific basin during June. While it
is not common for June to be completely stormless, a quiet June does
happen every now and then, the last such occurrence being in 1996.
However, it appears that there was a very short-lived small system
which reached tropical depression status and perhaps even minimal
tropical storm strength. This interesting "micro-midget" system
which affected Hong Kong on the night of 18-19 June is described
below.
ADDENDUM TO MAY TROPICAL CYCLONE SUMMARY
----------------------------------------
When I first received a copy of the list of new Asian typhoon names
in late 1998, I decided that whenever the names began to be utilized I
would report the contributing country or territory for each name and
give the basic meaning of the name. I forgot to do this for the
first two NWP systems to be assigned names from the new list. The
name "Damrey" is the Cambodian word for elephant; and "Longwang" was
contributed by China, being the name of the Dragon King who was the
god of rain in Chinese mythology. In ancient times people would offer
sacrifices to the Dragon King, praying for timely rainfall and abundant
harvests.
Hong Kong Midget Tropical Cyclone
18 - 19 June
---------------------------------
On 19 Jun I received an e-mail from Phil Smith, an Australian who
lives in Hong Kong and works as a computer salesman and consultant, and
who is also a dedicated tropical cyclone enthusiast. Phil related
how that on the night before, a very small tropical cyclone had formed,
rapidly intensified and moved inland right over Hong Kong--all during
the night while he slept! According to a report from the Hong Kong
Observatory, Tropical Cyclone Warnings were hoisted for only 4 hrs,
30 min--a record short duration, the previous shortest being in
association with a tropical depression in Sep, 1958 (9 hrs, 35 min).
As early as 14 Jun JTWC had mentioned an area of convection that
had formed in the South China Sea with a LLCC located along the tail
end of a shear line. The disturbed area remained quasi-stationary
for several days with a little increase in convective organization
becoming apparent by the 16th. By 18/0600 UTC the STWO indicated that
over the previous 24 hours satellite imagery had revealed an increased
organization of convection around a small LLCC located about 150 nm
southwest of Hong Kong and the potential for development was upgraded
to Fair. At 2300 UTC a special STWO was issued reporting that the
system was now inland about 50 nm north of Hong Kong with convection
persisting about a tightly-wrapped LLCC. By 19/0600 UTC the area
was centered about 250 nm north-northeast of Hong Kong, and at 2100 UTC
had moved out over the East China Sea and was extratropical.
According to the HKO report, the tiny tropical depression formed
only about 20 nm from the Observatory. When the depression was closest
to Hong Kong, Waglan Island and Tsing Yi reported 10-min avg wind
speeds of 29 kts and 22 kts, respectively. The lowest pressure
recorded at the Observatory was around 1000 mb.
Phil's report indicates that at Shatin (where he lives), winds
peaked at 15 kts from 2200 to 2300 local time with a minimum pressure
of 999 mb at 2200 Local. At Sai Kung (a few km east of Shatin) the
wind peaked at 38 kts (10-min avg) at 2200 Local and had abated to
33 kts an hour later. No pressure reports were available from Sai
Kung. (Since Phil indicates all the action occurred whilst he slept,
and the HKO report makes it clear the event happened during the
evening, I am assuming the times given are local times. Hong Kong
time exceeds UTC by 8 hours.)
According to Phil's e-mail the storm didn't begin to form until
about 2100 Local, although the Hong Kong area had been under the
spiralling rain bands of a low-pressure area for the previous couple
of days. It appears that the system was no more than 30 nm in
diameter. The HKO report refers to the system as a tropical
depression. Phil indicates that the wind speeds in his write-up are
10-min averages. If the 38-kt report from Sai Kung is verified, this
would indicate that the system may have been a brief tropical storm.
If more information comes to light on this very interesting little
storm it will be reported in a future summary.
***********************************************************************
NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea
Activity for June: No tropical cyclones
***********************************************************************
SOUTH INDIAN OCEAN (SIO) - South Indian Ocean West of Longitude 90E
Activity for June: No tropical cyclones
***********************************************************************
AUSTRALIAN REGION (AUG) - From Longitude 90E Eastward to Longitude 160E
Activity for June: No tropical cyclones
Australian Region Activity for June
-----------------------------------
No tropical cyclones or LOWs developed in the Australian Region
during June, but there was a system which formed east of Queensland
around mid-month which, while not a true tropical development, did
produce gale-force winds over a wide area. Since the warnings from
Brisbane did not classify the system as a tropical LOW, and since to
me it did not remotely resemble a tropical cyclone in the satellite
imagery which I looked at, I did not save any warnings for the LOW
from which a track might have been constructed. However, Jeff
Callaghan of BoM Brisbane sent me a summary of the system, so I am
including a synopsis of Jeff's write-up below.
A very strong upper-level jet stream was located in the southern
Coral/northern Tasman Seas on 9 Jun (maximum winds greater than
150 kts) with an upper-trough entering eastern Australia. On the
surface a trough was developing and extending southeastwards from the
northwest corner of the Coral Sea. During 10 Jun a LOW developed to
the west of Ile Loop (WMO 91574) and the maximum 10-min avg wind and
lowest SLP at that AWS were 040/32 kts and 1004.0 mb at 10/0900 UTC.
The LOW moved southeastward between Ile Loop and Cato Island (WMO
94394) and the maximum 10-min avg wind and lowest SLP at that AWS
were 130/38 kts and 1010.8 mb at 10/0600 UTC. The LOW then continued
moving rapidly southeastward and by 1200 UTC on the 11th was located
approximately midway between Noumea and Norfolk Island.
The strongest 10-min mean wind reports on the east coast of
Australia were at Cape Moreton AWS (WMO 94594): 140/42 kts at 1504 UTC
on the 11th and 120/41 kts at 0521 UTC on the 10th; and 160/43 kts
at 11/0208 UTC from Double Island Point AWS (WMO 94584). Little
impact was felt on the Queensland coast. Due to the rapid movement
of the LOW and the tendency for the strongest winds to be oriented
parallel with respect to the coast, the seas were not exceptionally
large. The largest peak wave height on the wave rider buoy east of
Brisbane was 6 metres. The Byron Bay buoy peaked at just over
7 metres, being a little more open to the southerly swell generated
deep in the Tasman Sea. (A thanks to Jeff for sending me this
information.)
***********************************************************************
SOUTHWEST PACIFIC (SWP) - South Pacific Ocean East of Longitude 160E
Activity for June: No tropical cyclones
***********************************************************************
A SLIGHT CHANGE TO SOUTHERN HEMISPHERE REPORTING BASINS
-------------------------------------------------------
For the upcoming Southern Hemisphere tropical cyclone season I am
planning to implement a slight change to the manner in which I group
and report Southern Hemisphere cyclones. As noted in the recent
Southern Hemisphere seasonal review for 1999-2000, the basins will be
defined as follows:
SWI - Southwest Indian Ocean - West of 90E
AUW - Northwest Australia/Southeast Indian Ocean - 90E to 135E
AUE - Northeast Australia/Coral Sea - 135E to 160E
SPA - South Pacific Ocean - East of 160E
Note that I have made a slight change to the identifiers for the
Southwest Indian and South Pacific Oceans to better reflect the
most commonly-used terminology for those regions: SWI and SPA
instead of SIO and SWP.
The tropical cyclogenetical regions of the Northern Hemisphere are
rather neatly divided into distinct basins by landmasses or, in one
instance, by a stretch of thousands of miles of the North Pacific where
tropical cyclone formation is very rare. But the Southern Hemisphere
is not thusly divided. Tropical cyclones form in a continuous band
beginning in the Mozambique Channel and continuing eastward across the
vast South Indian Ocean, through the seas and gulfs off northern
Australia, across the Coral Sea and into the South Pacific proper to
well east of the Dateline, and in certain years extending even further
eastward into the region of French Polynesia. The Southern Hemisphere
cyclogenetical zone spans nearly 200 degress of longitude, and it is
neither practical nor desirable to consider it as a single basin for
cyclone reporting or statistical studies.
Several different schemes for divvying up the Southern Hemisphere
into tropical cyclone basins have been followed, including:
A. JTWC's Operational Plan
1. South Indian Ocean - West of 135E
2. South Pacific Ocean - East of 135E
B. JTWC's Statistical Plan in their Annual Tropical Cyclone Reports
1. South Indian Ocean - West of 105E
2. Australian Region - 105E to 165E
3. South Pacific Ocean - East of 165E
C. Plan followed by Charlie Neumann in the "Global Guide to Tropical
Cyclone Forecasting"
1. South Indian Ocean - West of 100E
2. Southeast Indian and Northern Australia - 100E to 142E
3. Northeastern Australia and South Pacific - East of 142E
(Note: 142E lies essentially along the Cape York Peninsula.)
D. Current Boundaries of Various Warning Centre's AORs
1. Southwest Indian - West of 90E
2. Australian Region - 90E to 160E
3. South Pacific - East of 160E
(Note: The western boundary of Perth's AOR was originally 75E
prior to around 1970, then 80E for the 1970s and 1980s until
being set at 90E in the early 1990s.)
When I began writing the global tropical cyclone summaries in late
1997, I opted to follow Plan D in order to keep the cyclones grouped
together that were warned on by particular national meteorological
services. I could see some merit to each of the other plans, but this
one seemed simplest and was adequate for my purposes. The only change
I'm making is to divide the Australian Region into two sub-regions
along 135E. When reporting the cyclones for a given month within
the Australian Region, this will prevent the "leapfrogging" back and
forth that often occurs when reporting storms chronologically for the
whole region.
A study of cyclone tracks in the Australian Region dating back to
1960 revealed that the Arafura Sea north of the Northern Territory's
Top End in the vicinity of 135E is an area of minimum tropical cyclone
formation and movement. Gulf of Carpentaria cyclones seem to have
more in common with Coral Sea systems, especially with regard to
intensity, than with those of the Timor Sea. Very intense cyclones
seem to be rather rare in the Coral Sea and Gulf of Carpentaria, but
occur quite frequently in the waters off Western Australia.
I specifically made tallies of cyclone tracks falling into three
groups: (1) storms which crossed 135E (moving either east or west)
over water north of the Northern Territory, (2) systems which crossed
135E over land and re-emerged over water (mostly westward movers but
2 or 3 moved southeastward from the Arafura Sea over the Top End and
entered the Gulf of Carpentaria), and (3) cyclones which crossed the
Cape York Peninsula moving in either direction.
The results were:
(1) Crossed 135E over water: 16
(2) Crossed 135E over land: 11
(3) Crossed Cape York Peninsula: 34
Of the 34 systems which crossed the Cape York Peninsula, 5 crossed
the peninsula twice, moving in each direction.
I realize that using 135E as a line of demarcation for reporting
purposes will break Darwin's AOR into two regions, but the Darwin AOR
is an area of very low cyclone formation frequency with usually only
one or two cyclones forming per season. This past season there were
none. The majority of tropical cyclones forming in the Darwin region
fall into two distinct groups: (1) those which form in and make land-
fall along the shores of the Gulf of Carpentaria (a few of which
eventually reach the Timor Sea or move eastward and enter the South
Pacific Ocean), and (2) those which form north of the Top End and move
westward over water into the Timor Sea or else strike the Northern
Territory's northern coastline.
***********************************************************************
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 June 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
June as an example: jun00.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: jun00.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.typhoon2000.com> OR http://www.geocities.com/taifun00/>
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)
ITCZ - Intertropical Convergence Zone
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
SPCZ - South Pacific Convergence Zone
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
WFO - Weather Forecast Office
WMO - World Meteorological Organization, headquartered at Geneva,
Switzerland
UTC - Universal Time Coordinated, equivalent to Greenwich Mean Time
or Zulu (Z)
|
Document: summ0006.htm
Updated: 4th January 2007 |
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