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Monthly Global Tropical Cyclone Summary November 1999
[Summaries and Track Data] [Prepared by Gary Padgett]
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Monthly Global Tropical Cyclone Summary November 1999 [Summaries and Track Data] [Prepared by Gary Padgett] |
MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
NOVEMBER, 1999
(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.)
***********************************************************************
TROPICAL CYCLONE NAMES
for the SOUTH INDIAN OCEAN
and the SOUTHWEST PACIFIC OCEAN
The Tropical Cyclone Warning Centre (TCWC) at Nadi, Fiji, has
tropical cyclone warning responsibility for the South Pacific east of
160E and from the equator to 25S. The Meteorological Service of New
Zealand at Wellington has warning responsibility for waters south of
25S, but almost all tropical cyclones in this basin form north of 25S.
When a rare cyclone forms in the Wellington area of responsibility
(AOR), it usually will be assigned a name from the Fiji list (such as
was done for Tropical Cyclone Gita last February).
Tropical cyclone warning responsibility for South Indian waters west
of 90E are shared by several TCWCs. The Regional Specialty
Meteorological Centre (RSMC) for the region is the office of Meteo
France on the island of La Reunion. However, following a long-standing
practice, the sub-regional centres at Mauritius and Madagascar share
the responsibility for actually naming tropical storms with Mauritius
naming systems east of 55E and Madagascar covering the area west of
55E. RSMC La Reunion issues warnings for the basin independently of
these sub-regional centres, but only advises regarding when or when not
to assign a name to a developing cyclone.
Names for the 1999-2000 season (** indicates name has already been
assigned):
South Indian Southwest Pacific
-----------------------------------------------------------------------
Astride ** Lisanne Iris ** Trina
Babiola ** Maizy Jo Uka
Connie Nella Kim Vicky
Damienne Ortensia Leo Walter
Eline Priscilla Mona Yolande
Felicia Rebecca Neil Zoe
Gloria Sophia Oma Ami
Hudah Terrence Paula Beni
Innocente Victorine Rita Cilla
Jonna Wilna Sam Dovi
Kenetha Yanselma
***********************************************************************
NOVEMBER HIGHLIGHTS
--> Rare major November Caribbean hurricane almost becomes a
Category 5 hurricane--moves eastward across much of Caribbean Sea
and affects Lesser Antilles
--> Other basins relatively quiet--a few Northwest Pacific storms
***********************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for November: 1 hurricane
2 possible subtropical storms
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. A special thanks to John Wallace, a tropical cyclone
enthusiast and college student from San Antonio, for providing me with
a log which he had kept of all Atlantic/Northeast Pacific tropical
waves that proved to be very valuable in helping to trace the pre-
depression history of some of the cyclones.
Atlantic Activity for November
------------------------------
The tendency toward increased late-season major hurricane activity
seen in recent years in the Atlantic basin continued in 1999. One of
the strongest, if not the strongest, November hurricanes of the century
developed south of Jamaica and took an unprecedented eastward track
across the Caribbean Sea, ultimately affecting some of the Leeward
Islands. Hurricane Lenny reached an estimated MSW of 130 kts (which
possibly will be increased to 135 kts in post-season analysis) when
it was just south of the U. S. Virgin Islands. The only other
November hurricane in the official Atlantic historical database to
have reached 130 kts was the destructive Jamaican hurricane of 1912.
Fortunately, Lenny weakened somewhat before the inner core of the
hurricane passed over some of the islands, so the effects were not
nearly as devastating as they could have been. Lenny is also the
first hurricane on record to strike the Leewards moving in from the
west. The only other tropical storm to do so was Klaus in November,
1984, which eventually became a hurricane to the north of the Antilles.
Non-tropical Gale Centers
-------------------------
There were several gale centers in the subtropical Atlantic during
the month which occasionally produced substantial amounts of
convection. At least two of these displayed enough organization in
the convection to warrant their being mentioned in the Tropical Weather
Outlooks (TWO) from TPC/NHC. Neither system, however, evolved to the
point that they could be considered tropical cyclones, but remained as
hybrid (or possibly subtropical) storms.
The first of these two more prominent LOWs formed a few hundred
miles southeast of the Azores on 4 Nov. It drifted slowly westward
through 6 Nov, then moved off to the northeast on the 7th as a trough
approached. The cyclone appeared to be best organized on 6 Nov as
a band of convection wrapped around the center; however, there was no
CDO and the center remained partially exposed at all times. It was on
the 6th that the LOW was mentioned in the TWOs as having some potential
for tropical development. Scatterometer passes on the 6th and 7th
indicated surface winds on the order of 30-35 kts. The system was
beneath a strong upper-level LOW throughout its lifetime; shear was
quite low at peak intensity, but outflow was poor also.
The second hybrid LOW was producing gales at least by 24 Nov (as
per High Seas Forecasts from MPC), but it was on the 29th and 30th
that convection began to appear more organized. A TWO issued on the
final day of the Atlantic Hurricane Season (30 Nov) indicated that if
the trend seen during the morning continued, a tropical cyclone might
possibly develop, but by 1 Dec the convection looked less impressive
on satellite imagery. This gale center meandered around in the
mid-Atlantic roughly 1000 nm east and southeast of Bermuda for several
days. CIMSS low-level wind analyses indicated near-surface winds of
35-40 kts, but these gale-force winds were sparse and were to be found
exclusively in the northern semicircle--likely a result of the steep
pressure gradient between the LOW and a ridge to the north.
A special thanks is due John Wallace, a student at the San Antonio
branch of the University of Texas and a rather knowledgeable tropical
cyclone enthusiast, for supplying me with much of the above information
on the hybrid systems. John also sent me some tracking information
for the two LOWs which I used to construct tracks for these systems in
the accompanying cyclone tracks file.
Hurricane Lenny (TC #16)
13 - 21 November
-------------------------
An broad, weak area of low pressure accompanied by thunderstorms
appeared in the extreme southwestern Caribbean Sea early on 8 Nov.
Over the next few days this system drifted slowly northwestward toward
the region generally between Jamaica and Central America. The
convection was very slow to organize, although upper-level winds were
generally favorable for tropical development. By the 13th the LOW
had become better organized, and a reconnaissance plane from the
53rd Weather Reconnaissance Squadron of the U. S. Air Force Reserves
investigated the disturbance and found it to be sufficiently organized
enough so that TPC/NHC upgraded it to a tropical depression and began
issuing advisories. The depression at this time was centered about
300 nm west-southwest of Kingston, Jamaica.
By early the next morning the LLCC had become better involved with
the deep convection although the coldest cloud tops (to -80 C) remained
north of the center. Two ship observations from near the center
indicated winds of only around 12-13 kts, so the system was kept as
a tropical depression in the 14/0900 UTC advisory. By mid-morning
satellite estimates were at tropical storm intensity, but there had
been no recent ship or island observations to confirm that, so the
depression was not upgraded at this time--likely due to the earlier
ship reports of light winds. However, at one point during the early
morning, a feature which looked like a developing eye was briefly
visible. A midday flight by the Hurricane Hunters found FLW of
66 kts at 300 m just southeast of the center with a CP of 992 mb,
so the depression was upgraded to Tropical Storm Lenny in a special
advisory at 1915 UTC. Lenny's initial MSW was set at 55 kts and
the new storm was centered approximately 175 nm southwest of Kingston,
Jamaica.
In the 2100 UTC advisory the MSW was increased to 60 kts with the
CP having fallen further to 988 mb, and Lenny was upgraded to a
hurricane with 70-kt winds--the season's eighth--in a special Tropical
Cyclone Update issued at 2150 UTC. During the evening an SSM/I pass
revealed an eye 15-20 nm in diameter which had been obscured by a
burst of convection. The Discussion Bulletin accompanying the
15/0300 UTC advisory contained the following remark: "Obviously, the
rapid intensification of this tropical cyclone was not anticipated.
This again underscores our limited ability to predict intensity
changes." (Authored by Dr. Richard Pasch.) The rapid intensification
of Lenny from a tropical depression to a hurricane was not the only
unexpected thing which happened with this cyclone. During the night
the pressure continued to fall to 971 mb, and a reconnaissance plane
found 100-kt winds at 850 mb. The surface MSW was increased to 85 kts
at 15/0900 UTC as Lenny moved slowly east-southeastward south of
Jamaica. The wind radii were fairly small: hurricane-force winds
extended outward from the eye only 20 nm, and gale-force winds reached
out 75 nm to the northwest and 40 nm to the northeast.
During the morning the rapid intensification trend was halted and
Lenny weakened significantly. The highest winds found by the Hurricane
Hunters on a midday flight were 73 kts measured by a GPS dropwindsonde
in the southwest quadrant. The pressure had risen to 981 mb and
subsequently rose to 984 mb during the afternoon. The MSW was lowered
to 70 kts at 16/0300 UTC. There was no eye evident in either micro-
wave or infrared imagery, and the cloud pattern, while containing much
very deep convection, was not all that well organized. The reason for
this weakening was not understood very well either--possibly it was
due to the fact that the very small inner core region was affected by
some subtle environmental changes. However, during the night the
weakening trend was reversed and Lenny began to rapidly strengthen
again. An early morning (16th) reconnaissance flight found that the
pressure had dropped once more to 971 mb and the maximum FLW found at
850 mb was 109 kts. The plane also reported a 45-nm diameter eye.
Cloud tops near the center were -80 to -85 C and some satellite
intensity estimates were up to 102 kts (T5.5). The MSW was upped once
more to 85 kts based on this information, and this was possibly
conservative.
Hurricane Lenny was steered on an unprecedented easterly course
across the central Caribbean Sea by the flow around the southern end
of a deep-layer trough to the north. The CP had fallen to 965 mb by
around midday on 16 Nov, and a GPS dropwindsonde measured mean boundary
layer winds of 107 kts and 96 kts at the surface. By 1800 UTC Lenny
had become the season's fifth major hurricane on the Saffir/Simpson
scale with 100-kt MSW at a point about 200 nm south-southeast of Santo
Domingo. Early in the evening a center fix by a new WC-130 Model J
Hurricane Hunter aircraft found a CP of 958 mb, and a GPS dropwindsonde
measured winds of 126 kts at 907 mb in the southeast eyewall. The San
Juan WSR-88D radar revealed a 25-nm diameter eye surrounded by a
closed wall. The storm had grown larger in areal extent with gales
extending outward 175 nm and hurricane-force winds reaching outward
60 nm from the center.
Early on the 17th another GPS dropwindsonde measured 132 kts at
924 mb and 110 kts just above the surface. In an Intermediate
Advisory issued at 1300 UTC, Lenny's MSW was increased to 115 kts,
thereby making the storm the fifth Category 4 hurricane of the year.
The 17/1500 UTC advisory stated that a gust to hurricane force had
already been observed on St. Croix. A morning reconnaissance flight
found an extrapolated surface pressure of 942 mb and 134-kt winds at
700 mb, and a GPS dropwindsonde measured mean boundary layer winds of
118 kts. By 1800 UTC dangerous Hurricane Lenny had become a very
strong Category 4 hurricane with the MSW estimated at 130 kts and
the CP measured at 934 mb. The maximum FLW had increased to 149 kts,
the mean boundary layer winds measured by a GPS dropwindsonde were
155 kts, and peak winds at the 891-mb level had reached 180 kts a
couple of hours earlier.
Lenny began to move more toward the northeast early on 17 Nov and
was centered only about 20 nm south of the western part of the island
of St. Croix at 1800 UTC when its winds reached 130 kts. St. Croix
reported sustained winds of 72 kts with gusts to 97 kts during the
afternoon, and St. John reported gusts to 75 kts. Lenny's forward
motion slowed considerably as it approached the Leeward Islands.
The storm's center moved east-northeastward to near St. Maarten and
Anguilla by 19/0000 UTC and moved slowly over those islands, then
turned gradually toward the east-southeast, passing near St. Barthlemy
and later over Antigua around 0000 UTC on 20 Nov. After peaking in
intensity Lenny began to slowly weaken, likely due to upwelling since
initially the atmospheric environment was not particularly hostile.
At 18/0000 UTC the CP had risen to 939 mb and the MSW was lowered
slightly to 125 kts based on the most recent reconnaissance FLW of
128 kts. By 0600 UTC the CP had continued to rise to 947 mb, but
an aircraft encountered 700-mb winds of 145 kts and an eyewall GPS
dropwindsonde indicated winds of 132 kts near the surface. However,
by the time the storm had reached St. Maarten a reconnaissance flight
found FLW of only 107 kts, so the MSW was decreased to 95 kts with
the CP having risen to 975 mb. Lenny had been downgraded to a
60-kt tropical storm by the time it reached Antigua early on 20 Nov.
Some shearing of the system at the cirrus level was becoming apparent
in satellite imagery.
After passing through the Leewards the weakening Lenny moved slowly
east-southeastward away from the islands. The large, diffuse center
passed about 100 nm east of Guadeloupe around 1200 UTC on 20 Nov and
had reached a point about 125 nm east of the island of Dominica by
21/0000 UTC. Lenny was downgraded to a depression at 0900 UTC since
there had not been any surface reports of tropical storm-force winds
for 21 hours and there were neither scatterometer nor low-cloud winds
at this threshold. However, the long anticipated movement to the
northeast began as the once powerful hurricane was downgraded to a
dissipating depression. The weakening center had moved northeast-
ward to a point about 375 nm east of St. Maarten when the final
advisory was issued at 1800 UTC on 21 Nov.
There were quite a few observations of winds well above hurricane
force from the islands during Lenny's passage. A gust to 85 kts
was reported on Virgin Gorda in the British Virgin Islands during the
evening hours of 17 Nov. Later that evening a gust to 88 kts was
observed on the small island of Saba. Around midday on the 18th
St. Maarten reported wind gusts to 94 kts while St. Barthelemy reported
gusts to 108 kts. During the evening hours of 18 Nov a portion of
the eye was over St. Maarten and a ship (CAIT NAMARO) in Simpsons Bay
experienced winds of 87 kts. Shortly after midnight on the 19th,
St. Maarten was still reporting sustained winds of 64 kts gusting to
90 kts.
Damage was widespread and rather severe on some islands, but in
general was much less than it could have been had the intense inner
core of Hurricane Lenny passed directly over some of the islands when
the storm was near its peak intensity. The latest information
available to the author indicates that there were a total of 12 deaths
attributed to Hurricane Lenny with four of these on Guadeloupe. And
while several hundred homes were destroyed, the majority of damage
appears to have been to the infrastructure and environment, especially
coastal roads, sea defenses, piers, and beaches. The western coasts
of the islands were the most severely affected, as would be expected
with the hurricane approaching from the west. Industries affected
most severely were agriculture, fishing, and tourism. One preliminary
estimate placed the total damage amount at several hundred million
U. S. dollars.
On Antigua there was severe beach erosion with many roads washed
out and some mud slides resulting from the heavy rainfall. The nearby
island of Barbuda was especially hard hit by the torrential rains.
Almost 65% of the island was under water, roads were severely damaged,
and the ground water supply was contaminated. About 95% of the
agriculture industry, which includes peanuts, vegetables, corn, and
coconuts, was destroyed. St. Kitts suffered severe damage from
flooding and wave action with the total damage estimated to be near
$41 million in U. S. dollars. About $50 million (USD) in damage
was sustained by hotels on the island of Anguilla. Even Dominica,
which lay well south of the track of Lenny's eye, was affected
rather extensively by the storm. Hotels along the island's west
coast suffered major damage, about 35% of the banana crop was wiped
out, about 40% of coastal roads were washed out, and many piers and
port facilities were damaged.
More information about the effects of Hurricane Lenny may be found
at the following website: http://wwwnotes.reliefweb.int>. Click on
the "Natural Disasters" link.
***********************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for November: No tropical cyclones
***********************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for November: 2 tropical depressions (a)
3 tropical storms (b)
1 typhoon (c)
(a) One of these was not carried operationally as a tropical
depression, but later evolved into a vigorous subtropical
storm.
(b) Only one of these was carried operationally as a tropical
storm. One storm evolved out of a Hawaiian Kona storm
(subtropical) and the other was a monsoon depression carrying
gale-force winds. Additionally, Tropical Storm Frankie/Sendang
was not treated as a tropical storm by JMA.
(c) Not treated as a typhoon by JMA.
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. Also, as
announced earlier in a separate posting, a column of 10-min avg MSW
is included--the values being obtained from either PAGASA's or JMA's
advisories. A special thanks to Michael V. Padua, owner of the
Typhoon '99 webpage, 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 and name (if
any), JMA's tropical storm numeric designator, and PAGASA's name for
systems forming in or passing through their area of responsibility.
Northwest Pacific Activity for November
---------------------------------------
Sporadic activity continued over the Northwest Pacific basin during
November, but there were no intense typhoons. Only one storm was
classified as a typhoon and this by JTWC only. One weak minimal
tropical storm affected the central Philippines--this was treated as
a tropical storm by JTWC and PAGASA but not by JMA. One additional
short-lived system was carried operationally as a tropical depression
by JTWC and JMA, but there were drastic differences between the two
TCWCs during the latter portion of the system's life.
A circulation developed on 5 Nov northeast of the Mariana Islands
along the tail end of a shear line. JMA first mentioned the system
in their High Seas Warnings at 0600 UTC, placing the center about
400 nm northeast of Guam, but subsequently relocated the center to the
south and west six hours later. JTWC initiated warnings on TD-28W
at 1800 UTC with the center estimated to be just east of the northern
Marianas and accompanied by a broad and very disorganized area of
convection. Satellite intensity estimates were 25 kts but ship and
scatterometer data indicated winds to 30 kts. The depression had good
outflow aloft but was located in an environment of moderate vertical
shear. The depression moved little during the time that it was in
warning status by JTWC. At 06/0600 UTC it was relocated to just
west of the northern Marianas, but at 1200 UTC the LLCC had become
difficult to locate and shear was increasing, so the final warning
was issued with the dissipating center about 200 nm north of Guam.
While earlier during the depression's history, JTWC's and JMA's
position estimates had been in reasonably close agreement for such a
weak, disorganized system, at 06/1200 UTC JMA gave a center position
almost 450 nm to the northeast of JTWC's final warning position.
JMA subsequently tracked this center fairly quickly northward and
northeastward into the subtropics. The final JMA bulletin, at
07/1800 UTC, placed the center more than 1000 nm northeast of Guam.
I really don't have enough information to piece together just what
took place; i.e., whether or not JMA picked up on a totally different
LLCC or else this was a redevelopment of the center within the same
general circulation. Unfortunately, I don't have any JMA information
available for 0600 UTC on 6 Nov, and since JMA doesn't assign any
numbers or other identification to tropical depressions, I have no
idea if that TCWC considered the LLCC tracked on 6 and 7 Nov to be
a continuation of the center being following on 5 Nov or a totally
different system.
There were three interesting systems in the Northwest Pacific in
November for which warnings were not issued by any TCWC that I'm aware
of. I am indebted to Dr. Mark Lander of the University of Guam for
providing me with much information and some satellite imagery of these
systems. Dr. Lander is a professor at the Water and Environmental
Research Institute of the Pacific at the University of Guam, and for
ten years worked under a grant from the Office of Naval Research to
conduct research on tropical cyclones. Dr. Lander worked closely
during those years with forecasters and satellite analysts at JTWC.
A very special thanks to Mark for providing me with information on
these weather systems.
In keeping with the practice I initiated back during August, I have
chosen to designate these systems with letters of the Greek alphabet.
(See the Global Tropical Cyclone Summary for August, 1999, for a
discussion of this subject.) "Zeta" was a large monsoon depression
with peripheral gale-force winds which moved into southern Vietnam and
was responsible for very disastrous flooding which claimed hundreds of
lives. "Eta" began as a small tropical depression deep in the tropics
near Pohnpei and never attained tropical storm intensity, but later
merged with a frontal shear line and deepened into a large, intense
subtropical-type cyclone of near typhoon strength. Finally, "Theta"
was a large Hawaiian-style Kona storm which evolved into a small,
sheared tropical cyclone which likely was briefly of tropical storm
intensity. The narrative below on these three weather systems is
pretty much just as I received it from Mark with a slight amount of
editing performed and a few geographical references added.
Tropical (Monsoon) Depression "Zeta"
2 - 5 November
------------------------------------
During the period 3-5 Nov, a monsoon depression consolidated in
the South China Sea and moved westward into Vietnam on 5 Nov. Gale-
force winds were occurring in the primary cloud band to the north and
east of the LLCC, and were probably nearing gale force in the core as
"Zeta" made landfall.
This tropical cyclone was a typical monsoon depression with (among
other things):
(1) a large, sprawling tropical LOW with mesoscale convective
systems loosely organized into large-scale bands
(2) a large area of outflow cirrus and cirrus debris organized into
a well-defined, nearly symmetrical, anticyclonic pattern
(3) a wind distribution featuring a core of lighter winds of
15-20 kts, with near gale and gale-force winds displaced
100-250 nm outside of the low-level wind center (often in
a backwards "C"-shaped pattern)
Monsoon depressions become conventional tropical cyclones when they
acquire a persistent core of deep convection associated with higher
core wind speeds. About two-thirds of Northwest Pacific basin tropical
cyclones begin as monsoon depressions. JTWC (and likely other TCWCs
as well) has for years had trouble with monsoon depressions. Dvorak
satellite analysis (which was primarily developed in the Atlantic
basin where monsoon depressions are extremely rare) does not address
them as applied, and the higher winds are located at some distance
away from the core. JTWC prefers to attribute the gales in these
systems to "monsoon surges" or other types of "gradient" winds. The
danger is that when they acquire persistent central convection, an
"instant" (i.e., Warning #1) tropical storm is born with a very large
radius of gales.
In any case the monsoon depression that moved into Vietnam on 5 Nov
was a "significant" tropical cyclone with deadly impact. According to
a story from the 12 Nov edition of the_Pacific Daily News_ (of Guam),
the depression dumped more than 7 feet (2100 mm) of rain on seven
central provinces during a three-day period. At least 574 people
were known dead after Vietnam's worst flooding in a century. A
preliminary estimate places the damage at $215 million.
Another report received by the author dated 15 Nov gives some
additional information on the aftermath of the flooding: thousands
of cases of various diseases; 622 deaths; 70 persons missing; over
41,000 homes destroyed; 870,000 homes damaged; 94,000 classrooms
destroyed; almost 100,000 hectares of rice fields and other farmland
inundated; 205,000 metric tons of food lost; over 3000 hectares of
shrimp and fish farms destroyed; 1,470 bridges destroyed; and 25,000
head of cattle killed.
Tropical Storm Frankie/Sendang (TC-29W)
6 - 10 November
----------------------------------------
A Significant Tropical Weather Outlook (STWO) from JTWC on 3 Nov
indicated that an area of convection had developed and persisted for
about 12 hours several hundred miles south of Guam. Animated visible
satellite imagery indicated that a broad LLCC might be forming. By
4 Nov the system had become better organized with a LLCC evident,
falling surface pressures, and equatorial westerlies to the south
feeding into the disturbance. The development potential was upgraded
to Fair but was downgraded to Poor the following day when the LLCC was
no longer apparent in satellite imagery. The weakening trend,
however, reversed itself and the disturbance once more began to exhibit
increased organization. A Formation Alert was issued by JTWC at
05/0600 UTC, upgrading the development potential to Good. Convection
remained embedded in a very active monsoon trough, but there was once
more evidence of a LLCC associated with the convection while vertical
shear was weak to moderate.
JTWC upgraded the system to TD-29W at 0600 UTC on 6 Nov when it was
centered about 200 nm north of Koror or over 500 nm east of southern
Samar in the Philippines. Outflow was good and the convection was
slowly increasing in organization in a moderate shearing environment.
The depression was located under the weak steering influence of a
subtropical ridge to the northeast. Intensification proceeded at a
slow rate due to the persistent easterly shear. A subtropical ridge
to the northwest became the dominant steering influence and caused
the depression to track toward the west-southwest. PAGASA commenced
issuing warnings at 06/1800 UTC, naming the depression Sendang.
By 07/1800 UTC, after having moved west-southwestward for about
24 hours, Sendang turned back to the west-northwest and began to
show increased convective organization. At 0000 UTC on 8 Nov the
depression was centered northeast of the Leyte Gulf and moving west-
northwestward at 18 kts. PAGASA upgraded Sendang to a 40-kt tropical
storm at this time while JTWC waited until 0600 UTC before classifying
the system as Tropical Storm Frankie. Frankie was then located over
northern Samar. Satellite intensity estimates were 30-35 kts, but
a scatterometer pass showed winds of 35 kts. By 1200 UTC the storm's
convection was decreasing due to land interaction, and at 1800 UTC
JTWC downgraded Frankie back to a tropical depression. PAGASA,
however, kept Frankie/Sendang at tropical storm levels for six more
hours. The center of the storm at this time was in the Sibuyan Sea
about 65 nm east of Mindoro (this based upon JTWC information). Some
deep convection had begun to regenerate southeast and northwest of the
LLCC.
By 09/0000 UTC Frankie/Sendang had become quasi-stationary in the
vicinity of Masbate island with a fully exposed LLCC located about
40 nm east of the deeper convection. PAGASA had downgraded Sendang
to a depression by this time, and the weakening system spent the next
day or so meandering about the central Philippines in the general
area of Masbate, Sibuyan, and extreme southeastern Luzon. Some
orographically-induced convection occasionally was seen, but the
weakening trend continued and JTWC issued the final warning at 0000 UTC
on 10 Nov. No reports of damage or casualties have been located by
the author, although one press report mentioned that some Filipino
rice paddies had been flooded due to the storm's rains. (It should be
noted that JMA never upgraded Frankie/Sendang to a tropical storm in
their bulletins.)
Tropical Depression/Subtropical Cyclone "Eta"
8 - 16 November
---------------------------------------------
During the first week of November, the monsoon trough extended
eastward into the eastern Caroline Islands--a rare event this time of
year. During this active period of the monsoon, an unnumbered/unnamed
monsoon depression formed in the South China Sea, TD-28W formed north-
northeast of Guam, Tropical Storm Frankie (TC-29W) formed near the
Philippines, Typhoon Gloria (TC-30W) formed northwest of Guam, and a
small unnumbered/unnamed tropical cyclone formed northeast of Pohnpei.
The tropical disturbance that became Tropical Cyclone "Eta" formed
near Pohnpei at the eastern end of the monsoon trough. A prominent
TUTT cell--with its own areas of deep convection--was present to the
northeast of this disturbance. Around 8 Nov, well-defined low-level
cloud lines indicated that a tropical depression had formed in
association with the persistent deep convection near Pohnpei. The
depression was centered about 200 nm north-northeast of Pohnpei at
08/0000 UTC. This tropical depression moved to the northwest into a
relatively cloud-free environment. It was a very small tropical
cyclone with a shear pattern structure. The deep convection near the
small LLCC collapsed and redeveloped several times. This sort of
behavior of the deep convection associated with a weak sheared tropical
cyclone is commonly indicative of an intensity of about 30 kts, as
confirmed by an ERS-2 Scatterometer pass at 1215 UTC on 9 Nov which
showed a small region with winds of at least 25 kts.
The tropical cyclone recurved as it approached a shear line, reaching
the westernmost point of its track at 1200 UTC on 10 Nov when it was
centered about 800 nm northwest of Pohnpei or 600 nm northeast of Guam.
On 11 Nov the tropical cyclone merged with the the shear line cloud
band and then began to re-intensify, becoming a subtropical storm with
35-kt winds at 12/1200 UTC when it was located 550 nm north of Wake
Island. The system evolved into a large and intense subtropical
cyclone and peaked at near typhoon intensity on 15 Nov when it was
centered roughly 500 nm northwest of Midway. The intense subtropical
LOW moved eastward and weakened on 16 Nov about 475 nm north-northeast
of Midway.
Typhoon Gloria/Trining (TC-30W / STS 9922)
13 - 16 November
-------------------------------------------
The final named tropical cyclone of 1999 in the Northwest Pacific
basin had its beginnings in an area of convection which had developed
by 10 Nov over the Philippine Sea along the tail end of a shear line.
By the next day the area had moved westward and was located east of
northern Samar. No LLCC was apparent yet but atmospheric conditions
in general were considered quite favorable for development, so the
system was given a Fair development potential by JTWC. The daily
STWO issued at 0600 UTC on 12 Nov indicated that the main area of
interest had drifted southward and was located about 330 nm east of
Samar. A Formation Alert was issued at 0700 UTC and indicated that
animated visible imagery showed convection building around a LLCC.
The system had some monsoon depression characteristics at the time
with the strongest winds around the periphery. A second Formation
Alert was issued at 13/0500 UTC, locating the center of the developing
depression about 150 nm to the north of its position the previous day.
JTWC upgraded the disturbance to a tropical depression at 0600 UTC
on 13 Nov with the center roughly 400 nm east of Catanduanes Island in
the Philippines. PAGASA initiated warnings at 1800 UTC, naming the
depression Trining. The depression was steered slowly northward by
a subtropical ridge to the northeast. Trining's development was
initially hampered by easterly shear resulting from converging
monsoonal flow and easterlies situated to the northeast. Early on
14 Nov the LLCC reconsolidated to the west beneath resurging deep
convection while the old center weakened. At 0600 UTC JTWC relocated
the center to the west-northwest and upgraded the depression to
Tropical Storm Gloria--the center was located about 475 nm east of
Cabo Engano on the northeastern tip of Luzon at the time. By 1800 UTC
the MSW had increased to 45 kts as Gloria moved northward at 10 kts
from a position about 350 nm southeast of Okinawa.
As the 15th began drier air and increasing vertical shear had
led to the dissipation of most of the convection in the southern half
of the circulation. JTWC maintained the MSW at 45 kts through
0600 UTC and then decreased it to 40 kts at 1200 UTC, but JMA raised
their 10-min avg MSW estimate to 50 kts at 0600 UTC. By 1800 UTC
Gloria had accelerated and was moving northeastward at 36 kts. This
rapid motion with the flow decreased the relative shear and allowed
the cyclone to strengthen. In an infrared image sent to me by Mark
Lander, taken at 15/1130 UTC, an eye appears to be forming; and in
another image taken two hours later, a cloud-filled eye is clearly
visible. After having reduced the MSW to 40 kts at 1200 UTC, JTWC
abruptly increased the MSW to 65 kts at 1800 UTC. The 20-nm diameter
eye was centered about 525 nm east of Okinawa at this time.
Gloria's tenure as a typhoon was short-lived as drier air continued
to invade the circulation. The storm passed about 300 nm north of
Iwo Jima at 16/0000 UTC, racing northeastward at 40 kts. Convection
had decreased and the eye was no longer apparent. Gloria was being
steered by the combination of a mid-latitude trough over Japan and
a subtropical ridge located to the southeast of the typhoon. By
0600 UTC Gloria was weakening and had become primarily extratropical,
so JTWC issued their final warning on the storm, which was located
about 350 nm east-southeast of Tokyo and moving northeastward at
47 kts. Based on satellite estimates the final MSW was reported as
55 kts. JMA issued one additional warning on the system at 1200 UTC
with the storm having moved quickly northeastward to a point almost
650 nm east of Tokyo.
Subtropical Storm/Tropical Cyclone "Theta"
26 November - 1 December
------------------------------------------
On 26 Nov a large Kona LOW (or Kona storm) formed to the west-
northwest of Hawaii or about 120 nm south of Midway. The Kona LOW is
a Hawaiian regional designation for cut-off LOWs in the subtropics
that turn the winds in Hawaii from trades to southwesterly, or Kona
(leeward-side) winds. This large Kona LOW drifted to the southwest,
crossing the International Dateline on 27 Nov at a point about 250 nm
southwest of Midway. The system intensified and acquired the
characteristics of a subtropical cyclone. The core convection of the
LOW began to detach from the large outer spiral cloud band as it
slowly evolved from its subtropical structure to that of a tropical
cyclone. On the morning of 29 Nov, a small area of persistent deep
convection consolidated near the core to become a midget tropical
cyclone.
The system by now was located more than 400 nm west-southwest of
Midway. The very small tropical cyclone drifted to the west and
slowly weakened as shear caused the LLCC to become partially exposed
on the north side of the deep convection. The estimated MSW had
dropped to 30 kts by 0000 UTC on 30 Nov--at this point the center
was about 400 nm north-northeast of Wake Island. The shear continued
as the deep convection was first pushed off to the south side of the
circulation and later collapsed to leave a swirl of low cloud lines.
The final position given in the track file places the dissipating
center about 425 nm northwest of Wake Island at 0000 UTC on 1 Dec.
Based upon the best track data supplied by Mark, the system's peak
intensity as a subtropical storm was 50 kts from 0600 to 1200 UTC
on 27 Nov. After "Theta" had made the transition to a tropical
cyclone, the peak MSW had dropped to 40-45 kts.
***********************************************************************
NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea
Activity for November: No tropical cyclones
***********************************************************************
SOUTH INDIAN OCEAN (SIO) - South Indian Ocean West of Longitude 90E
Activity for November: No tropical cyclones
***********************************************************************
AUSTRALIAN REGION (AUG) - From Longitude 90E Eastward to Longitude 160E
Activity for November: No tropical cyclones
***********************************************************************
SOUTHWEST PACIFIC (SWP) - South Pacific Ocean East of Longitude 160E
Activity for November: 1 tropical depression (possibly hybrid)
1 depression (or LOW)--likely baroclinic
Southwest Pacific Activity for November
---------------------------------------
While there were no named tropical cyclones in the Southwest Pacific
basin during November, there were a couple of systems for which gale
warnings were issued. The first depression was analyzed about 400 nm
southwest of Fiji at 1200 UTC on 1 Nov. All the convection and the
peripheral gales were confined to the southern semicircle. The system
drifted slowly southward and into Wellington's AOR on 2 Nov. Someone
(Patrick Hoareau I think) sent me a visible satellite image taken at
05/0031 UTC which showed a tightly-wound vortex of low- and mid-
level clouds right along the 165th meridian between New Zealand and
Australia. I wrote to Steve Ready of the New Zealand Meteorological
Service to see if there were any connection with the tropical
depression of a few days earlier. So Steve sent me a brief history
of this system, most of which is included in the following paragraphs:
"At 0000 UTC on 3 Nov the depression was centered near 29.0 S,
172.0 E with a CP of 1001 mb. At this stage the LLCC was located near
the northern edge of a dense overcast. Between 0800 and 1700 UTC on
the 3rd, the LOW wound up very quickly with a dry slot working its way
around a blob of central convection to the northern side of the LLCC.
As far as we could ascertain, the CP fell to 994 mb. The LOW deepened
in response to a shortwave trough shifting across the northern Tasman
Sea and tilting over to become negatively oriented (i.e., northeast-
southwest). The behaviour of this shortwave trough increased the
divergence in the vicinity of the LLCC, causing it to transform into
a more significant LOW system. The tropical depression brought a pool
of moisture and vorticity into the subtropics which was right for being
picked up by an appropriate upstream shortwave trough.
This type of development is quite common in this part of the world.
The tropical input did play a very important part, but you would have
to call it a hybrid LOW as the mid-latitude forcing was also essential
to its development. The LOW continued to track south-southwestward at
3 to 6 degrees (of latitude) per day and on the 5th and 6th a lot of
the clouds around the centre evaporated with a wee bit of convective
activity left in the southeast quadrant. The remains of the LOW
passed close to the southwest corner of the South Island before being
absorbed into the high-latitude westerlies south of 50S between 170E
and 180. On 5 Nov the CP rose from near 990 mb to just over 1000 mb."
(A special thanks for Steve for sending me a write-up of this
interesting system.)
There was another LOW pressure system in the South Pacific which
produced gales around mid-month, but this was never referred to in
warnings from Nadi as a "tropical" depression, so likely it was more
baroclinic in nature. The LOW was located about 150 nm south-southeast
of Tahiti at 0000 UTC on 13 Nov and tracked generally to the south-
southwest over the next 36 hours, being located about 525 nm south-
southwest of Tahiti at 14/1200 UTC. A couple of tropical disturbances
which formed west of the Dateline during the latter part of November
were designated as 01F and 02F by the Nadi TCWC, but neither attained
sufficient enough organization to be classed as a tropical depression.
***********************************************************************
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 included in the July, 1998 summary.
I will include this glossary from time to time, primarily in "lean"
months without a lot of tropical cyclone activity to cover. But if
anyone missed receiving it and wishes to obtain a copy, send me an
e-mail privately and I'll forward them a copy.
***********************************************************************
AUTHOR'S NOTE: This summary should be considered a very preliminary
overview of the tropical cyclones that occur in each month. The cyclone
tracks (provided separately) will generally be based upon operational
warnings issued by the various tropical cyclone warning centers. The
information contained therein may differ somewhat from the tracking and
intensity information obtained from a "best-track" file which is based
on a detailed post-seasonal analysis of all available data. Information
on where to find official "best-track" files from the various warning
centers will be passed along from time to time.
The track files are not being sent via e-mail. They can be retrieved
in the following manner:
(a) FTP to: 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
November as an example: nov99.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: nov99.sum, for
example.
Back issues can also be obtained from the following websites
(courtesy of Michael Bath, Michael V. Padua, Tom Berg, Michael
Pitt, and Rich Henning):
http://australiansevereweather.com/cyclones/>
http://www.geocities.com/capecanaveral/6825>
http://www.hcane.com/tropcl.html>
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
JTWC now has available on its new website the completed Annual
Tropical Cyclone Report for 1998. Also, reports for each year from
1959 through 1997 are available in Adobe Acrobat format.
The URL is: http://199.10.200.33/jtwc.html>
TPC/NHC has available on its webpage nice "technicolor" tracking
charts for the 1998 Atlantic and Eastern North Pacific tropical
cyclones, and preliminary storm reports for all the 1998 Atlantic
and Eastern North Pacific cyclones are now available. Also, a few
preliminary reports for some of the 1999 tropical cyclones are
already available.
The URL is: http://www.nhc.noaa.gov/1998.html>
Prepared by: Gary Padgett
E-mail: [email protected]
Phone: 334-222-5327 (nights & weekends) / 850-882-2594 (weekdays)
***********************************************************************
***********************************************************************
|
Document: summ9911.htm
Updated: 4th January 2007 |
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