MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
OCTOBER, 2005
First Installment
(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.)
NOTE: The October summary will be issued in two installments. The first
will cover the Atlantic and Northeast Pacific basins, while the second
will cover the remaining tropical cyclone basins.
*************************************************************************
OCTOBER HIGHLIGHTS
--> Extremely active Atlantic with six storms--four hurricanes
--> Record low Atlantic barometric pressure recorded
--> Devastating hurricane strikes Yucatan Peninsula and southern Florida
--> Hundreds of deaths in Mexico and Central America from tropical
cyclone-induced and monsoon rains
--> Western North Pacific quieter--two typhoons and neither destructive
*************************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for October: 1 tropical depression
1 subtropical depression
2 tropical storms
2 hurricanes
2 intense hurricanes
Sources of Information
----------------------
Most of the information presented below was obtained from the
various tropical cyclone products issued by the Tropical Prediction
Center/National Hurricane Center (TPC/NHC) in Miami, Florida:
discussions, public advisories, forecast/advisories, tropical weather
outlooks, special tropical disturbance statements, etc. Some
additional information may have been gleaned from the monthly
summaries prepared by the hurricane specialists and available on
TPC/NHC's website. All references to sustained winds imply a
1-minute averaging period unless otherwise noted.
SPECIAL NOTE!!! Many of the official TPC/NHC tropical cyclone reports
are now available online at the following link:
<http://www.nhc.noaa.gov/2005atlan.shtml>
Atlantic Tropical Activity for October
--------------------------------------
October, 2005, became the most active October on record in the
Atlantic basin. The six NS tied the previous record set in 1887 and
again in 1950. The NTC was a whopping 63% (based on 1950-2004), the
average NTC for October being 16%. Over the period 1950-2004, the
averages are: 1.7 NS, 1.1 H, 0.4 IH, 9.1 NSD, 4.3 NSD, 0.8 IHD. The
numbers for October, 2005, are: 6 NS, 4 H, 2 IH, 18.5 NSD, 9.75 HD,
and 5 IHD. With 17 named storms already having formed by the end of
September, the six NS of October carried the count of Atlantic storms
to 23--two more than the previous record season of 1933. Also, by
month's end 13 storms had reached hurricane intensity, exceeding 1969's
previous record of 12 hurricanes.
Hurricane Wilma dominated the tropical scene, producing the most
explosive, rapid intensification episode ever seen in the annals of
Atlantic hurricane history. The central pressure fell 97 mb in 24 hours
to a record basin low of 882 mb. The hurricane devastated the north-
eastern portions of Mexico's Yucatan Peninsula and also delivered a
rather destructive blow to South Florida. This amazing hurricane also
produced the smallest eye known to TPC hurricane forecasters (2 nm), and
set a new world record for 24-hour rainfall accumulation over non-
mountainous terrain when Mexico's Isla Mujeres recorded more than
62 inches (1575 mm) in a 24-hour period.
Early in the month Tropical Storm Stan formed just off the eastern
coast of the Yucatan Peninsula and crossed the peninsula into the Bay
of Campeche where it became a minimal hurricane. Stan brought heavy
rainfall to portions of Mexico, resulting in at least 80 deaths. Very
heavy monsoon rains further east in Mexico and in Central America were
blamed for between 1000 and 2000 fatalities, and these deaths at the
time were attributed to Stan by the press. Late in the month Hurricane
Beta formed deep in the southwestern Caribbean Sea, moved northward, then
made a left hook toward Central America, eventually striking Nicaragua as
a Category 2 hurricane.
During the first week of October, Tropical Storm Tammy formed just off
the Florida East Coast and moved north-northwestward and inland in
extreme northeastern Florida. Hurricane Vince formed northwest of the
Madeira Islands, becoming the most northeasterly-forming Atlantic
tropical cyclone on record. Vince later made landfall on the Iberian
Peninsula shortly after weakening to tropical depression status. The
other October storm, Tropical Storm Alpha, formed in the central
Caribbean and struck the Dominican Republic's Barahona Peninsula. Alpha
was the first of six tropical storms to be named with Greek letter
alphabet names, a procedure established more than a decade earlier as
a contingency plan in case either the Atlantic's or Eastern North
Pacific's regular list of names was exhausted and additional storms
developed.
Reports on all the named cyclones follow. Kevin Boyle journeyed out
of his normal Northwest Pacific haunts to write the reports on Tammy,
Vince and Beta. A special thanks to Kevin for his assistance.
In addition to the six named storms, there were two non-developing
depressions during the month, one tropical in character while the other
was classified as a subtropical depression. Tropical Depression 19
formed late on 30 September several hundred miles west of the Cape Verde
Islands. The system tracked generally north-northwestward over the next
couple of days, encountering strong southwesterly shear which rendered it
unable to strengthen into a tropical storm. A very brief report on this
system, written by Lixion Avila, is available on TPC/NHC's website. A
graphic depicting the track of Tropical Depression 19 may be found at the
following link:
<http://www.tropicalcyclone2005.com/database/2005/atlantic/BT-IMAGES/2005-19
L-NONAME.gif>
Subtropical Depression 22 formed on 8 October about 535 nm southeast
of Bermuda in a surface trough located on the northeastern side of an
upper-level LOW. Due to the association of the surface and upper-level
LOWs, combined with the influence of the cold air of the upper-level
system, the depression was classified as subtropical rather than
tropical. The depression turned westward on the 9th as deep convection
began to diminish due to strong easterly shear. The depression was
downgraded to a remnant LOW, but the residual system moved on toward the
U. S. East Coast, merging with a cold front on 11 October east of Cape
Hatteras. The LOW then intensified as an extratropical system, causing
gale-force winds over the western Atlantic from 12-14 October. A short
report on this system, authored by Jack Beven, is available on TPC/NHC's
website. A graphic depicting the track of Subtropical Depression 22 may
be found at the following link:
<http://www.tropicalcyclone2005.com/database/2005/atlantic/BT-IMAGES/2005-22
L-NONAME.gif>
HURRICANE STAN
(TC-20)
1 - 5 October
----------------------------------
A. Synoptic History
-------------------
October's first tropical storm formed from a tropical wave which left
the African coast after the middle of September. The first mention of
this wave in TPC/NHC's Tropical Weather Outlooks was on the morning of
25 September at 0930 UTC when the wave was producing showers and thunder-
storms over the southeastern Caribbean Sea. This wave moved across the
Caribbean during the ensuing week, gradually increasing in organization
as environmental conditions slowly became more conducive for tropical
cyclone development. A Special Tropical Disturbance Statement was issued
at 1910 UTC on the 29th after a U. S. Air Force Reserve reconnaissance
aircraft had investigated the system. At that time, a tropical
depression had not formed--the plane found a large area of light and
variable winds with a minimum pressure of 1009 mb at a point about
150 nm southwest of Grand Cayman Island. However, there was no deep
convection located near the area of lowest pressure.
By the morning of 1 October the disturbance had become better defined
and advisories were initiated on Tropical Depression 20 at 1500 UTC.
The broad center of the depression was located about 95 nm southeast of
Cozumel, Mexico, moving west-northwestward at 5 kts. The initial MSW
was estimated at 25 kts, but this was increased to 30 kts in an
intermediate advisory issued 1800 UTC as the system continued to become
better organized. The depression continued slowly to approach the
Yucatan Peninsula and attained tropical storm status just before making
landfall early in the morning of 2 October. A Tropical Cyclone Update
was issued at 02/0635 UTC upgrading TD-20 to Tropical Storm Stan. A
reconnaissance plane had found an 850-mb FLW of 50 kts within a band of
very deep convection to the southeast of the broad LLCC. By the time
of the 02/0900 UTC advisory, the 40-kt tropical storm was making landfall
about 35 nm south of Tulum, Mexico, and about 65 nm south-southwest of
Cozumel.
NOTE: While so many of the tropical storms of the 2005 season represented
the earliest occurrence of their particular ordinal number, Stan was not
the earliest 18th "named" storm on record. That distinction belongs to
the 18th storm of 1933, which reached tropical storm status on 1 October,
one day earlier than Stan.
Stan continued moving west-northwestward across the Yucatan Peninsula
and maintained tropical storm status due to the presence of tropical
storm-force winds in bands offshore. The cyclone was downgraded to
tropical depression status at 03/0300 UTC while located about 85 km
southwest of Progresso, Mexico, but this was only for a 6-hour period.
Around 03/0000 UTC Stan was centered roughly 50 km due south of Merida
and its track at this time bent to the west, a motion which brought the
center back into the Gulf of Mexico off the northwestern Yucatan coast
around 0430 UTC. Based on an 850-mb FLW of 43 kts and a CP of 1002 mb,
Stan was re-upgraded to a tropical storm at 0900 UTC. After emerging
into the Gulf, Stan's track became increasingly west-southwesterly due
to a mid-level ridge to the north. By 2100 UTC the MSW had increased
to 50 kts based on dropsonde reports of surface winds of that magnitude.
Winds were up to 60 kts by 04/0600 UTC with Stan then located about
120 nm east of Veracruz and moving west-southwestward at 8 kts.
Stan was upgraded to a hurricane at 04/0900 UTC with the CP having
fallen to 979 mb and FLWs supporting 65 kts at the surface. Hurricane
Stan made landfall around 1500 UTC on 4 October about 75 nm east-
southeast of Veracruz with the MSW estimated at 70 kts. The system was
downgraded to a tropical storm at 1800 UTC and further to tropical
depression status at 05/0300 UTC. Stan was by then well inland over
Oaxaca State and weakening. The circulation continued to become less
defined and TPC/NHC issued the final advisory at 0900 UTC with peak
winds estimated at 25 kts. The accompanying discussion bulletin stressed
that, while most of the core convection had dissipated, some thunderstorm
activity persisted around the periphery of the circulation, and with the
very slow movement of the system, very heavy rainfall was likely with
life-threatening flash floods and mudslides likely.
A graphic depicting the track of Hurricane Stan may be found at the
following link:
<http://www.tropicalcyclone2005.com/database/2005/atlantic/BT-IMAGES/2005-20
L-STAN.gif>
B. Damage and Casualties
------------------------
The Mexican government reported that 80 deaths occurred in the states
of Chiapas, Oaxaca and Veracruz due to flooding and landslides caused
by the heavy rains of Stan. However, at around the same time torrential
rains fell in eastern Mexico and Central America in association with the
western portion of a broad-scale low-level cyclonic circulation, leading
to disastrous flooding in these areas. Estimates of the number of
fatalities related to this flooding range from 1000 to over 2000 with
Guatemala alone experiencing more than 1000 deaths. Given that the
surface circulation of Stan was confined to the Mexican states in the
area where landfall occurred, the TPC/NHC report places the direct death
toll from Stan at 80. However, many reports in the media attributed all
the Central American rainfall-related fatalities to Hurricane Stan.
(Report written by Gary Padgett)
TROPICAL STORM TAMMY
(TC-21)
5 - 6 October
----------------------------------------
Tropical Storm Tammy formed from a disturbance initially noted
roughly 750 nm east of the central Bahamas. The storm's roots involved
a complex interaction between an upper-level LOW and a westward-moving
tropical wave which had left the African coast on 24 September. The
disturbance was first mentioned in TPC/NHC's Tropical Weather Outlook
at 2121 UTC 1 October. The disturbance persisted for several days while
drifting towards the west-northwest and passed through the Bahamas late
on 3 October. The system began to organize on 4 October and, after radar
and surface data indicated the formation of a surface circulation, the
disturbance was upgraded to Tropical Storm Tammy in a special advisory
issued by TPC/NHC at 05/1100 UTC. The newly-christened tropical storm
was centred a little over 20 nm east of Cape Canaveral, Florida.
(Editor's Note: Due to the pressure gradient with a HIGH to the north,
gale-force winds were already present over the area. As soon as the
existence of a surface circulation was confirmed, it was by definition
a tropical storm. Hence, Tammy skipped the tropical depression stage.)
Tropical Storm Tammy tracked quickly north-northwestwards parallel to
the Florida East Coast on 5 October, embedded in the southerly flow
between a mid to upper-level LOW over the northeastern Gulf of Mexico
and a deep-layer ridge over the mid-Atlantic states. Intensifying
further, the system reached its peak intensity of 45 kts at 2100 UTC
5 October shortly before making landfall near Mayport, Florida, at
around 05/2300 UTC. The system continued inland over south-central
Georgia and was downgraded to a tropical depression at 06/1500 UTC, the
time of the final advisory issued by TPC/NHC. The tropical cyclone was
finally absorbed by a large extratropical LOW over the Florida Panhandle.
Reconnaissance aircraft reported peak flight-level winds of 53 kts
about 150 nm northeast of the center at 2100 UTC 5 October. At this
time, the crew made visual surface estimates of 50 to 55 kts in a few
spots. Based on these observations, the forecaster on duty writing the
advisory at 05/2100 UTC suggested that the peak intensity of Tammy
could have been slightly higher than 45 kts.
Minor flooding from rainfall and a 2-4 ft storm surge were reported
in northeastern Florida and southern Georgia. Scattered minor damage
was reported but the total was less than $25 million.
A graphic displaying the track of Tropical Storm Tammy may be
found at the following link:
<http://www.tropicalcyclone2005.com/database/2005/atlantic/BT-IMAGES/2005-21
L-TAMMY.gif>
Editor's Note: Since the above report was written by Kevin Boyle, the
official TPC/NHC storm report, authored by Stacy Stewart, has been
made available online. The official peak intensity for Tammy has been
estimated at 45 kts.
(Report written by Kevin Boyle)
HURRICANE VINCE
(TC-23)
9 - 11 October
-----------------------------------
Vince was a very small and short-lived hurricane which formed in an
unusual location in the far northeastern Atlantic a few hundred miles
northwest of the popular holiday resort of Madeira. It was the first
tropical cyclone ever to be assigned a name beginning with the letter
'V' since NHC began the practice of naming storms in the Atlantic basin
in 1950. Vince became a hurricane late on 9 October near 18.6W, the
farthest east a tropical cyclone has ever done so. Also, Vince became
the first recorded tropical cyclone to make landfall on the Iberian
Peninsula.
Hurricane Vince formed from a non-tropical LOW which drifted
southeastward across the Azores on 6 October before becoming slow-moving
in the far northeastern Atlantic on 8 October. The system was first
mentioned in NHC's Tropical Weather Outlook at 1516 UTC 8 October.
Remarks include: "Satellite imagery indicates that shower activity has
increased in association with a non-tropical low pressure system
located about midway between the Azores and the Canary Islands. While
this system is over relatively cold sea surface temperatures...it will
be monitored for any additional signs of subtropical cyclone
development." The LOW remained slow-moving until 9 October when a slow
northeastward crawl began. The system steadily acquired tropical
characteristics and became a 45-kt tropical storm at 09/1500 UTC while
located over SSTs of approximately 23 to 24 Deg C.
Continuing slowly northeastwards, Vince was upgraded to a 65-kt
hurricane at 2100 UTC 9 October while located a little over 130 nm
northwest of Madeira. However, an approaching frontal trough and its
associated unfavourable wind shear environment ensured that Vince would
not be a hurricane for long, and by early 10 October the tropical
cyclone was already beginning to deteriorate markedly. The eye soon
faded and the deep convection decreased significantly while becoming
displaced to the east of the centre. Vince was downgraded to a
tropical storm at 10/1500 UTC after the LLCC had become completely
exposed. Accelerating east-northeastwards, Vince maintained tropical
storm intensity while passing south of Faro, Portugal, early on
11 October. It was downgraded to a tropical depression at 11/0900 UTC
while making landfall near Huelva in southern Spain. Vince quickly
dissipated over southern Spain late on 11 October.
The remnants of Hurricane Vince brought much-needed rain to the
drought-ridden regions of southern Spain. Streets were flooded in
Cordoba where 86 mm fell in just 12 hours, but overall there were few
really exceptional rainfall totals. A number of locations in Spain
reported tropical storm-force wind gusts. There were no reports of
damage or casualties.
A graphic displaying the track of Hurricane Vince may be found at
the following link:
<http://www.tropicalcyclone2005.com/database/2005/atlantic/BT-IMAGES/2005-23
L-VINCE.gif>
Editor's Note: The above report was written by Kevin Boyle before the
official TPC/NHC storm report, written by James Franklin, had become
available online. According to the official report, the pre-Vince
LOW has now been classified as a subtropical storm from 08/0600 UTC.
However, it was not carried as a subtropical storm operationally.
(Report written by Kevin Boyle)
HURRICANE WILMA
(TC-24)
15 - 26 October
-----------------------------------
A. Introduction
---------------
After having produced two near-Category 5 hurricanes in early July
(Dennis and Emily), the warm waters of the western Caribbean Sea took
a back seat to the Gulf of Mexico and the Bahamas region through the
middle part of the season. However, according to climatology, this
region is the favored area for major tropical cyclone development
during the latter part of the season, and the western Caribbean certainly
lived up to its reputation during October, 2005. At the first of the
month, Tropical Storm Stan formed just off the eastern Yucatan coast and
later became a minimal hurricane in the Bay of Campeche. And during
the closing days of the month, major Hurricane Beta formed deep in the
southwestern reaches of the Caribbean and took a westward turn toward
Nicaragua. However, it was in the middle of the month and in the middle
of the western Caribbean that the real show took place.
Developing with excruciating slowness in a monsoon trough-like
situation, Hurricane Wilma deepened into not only the most intense
hurricane of the incredible 2005 season, but managed to produce the
lowest pressure ever recorded in an Atlantic hurricane. This amazing
hurricane set several records, which will be summarized in Section C
following. Following its show-stopping meteorological statistics
performance, dangerous Wilma devastated the northeastern Yucatan
Peninsula and later struck a destructive blow to South Florida.
The excellent and informative official TPC/NHC report on "super"
Hurricane Wilma is now available online at the link referenced in the
introductory paragraph, and I highly recommend that readers access and
read it. This report was a collaborative effort by Richard Pasch, Eric
Blake, Hugh Cobb and David Roberts, all of TPC. Some of the information
below was taken from this report, and since it is now available, I will
not attempt a full report on Wilma.
John Diebolt has produced three graphics of the track of Hurricane
Wilma. The graphic with the larger view depicting the entire track
may be accessed at the following link:
<http://www.tropicalcyclone2005.com/database/2005/atlantic/BT-IMAGES/2005-24
L-WILMA.gif>
A zoom-in showing the details of the erratic track in the western
Caribbean may be found at:
<http://www.tropicalcyclone2005.com/database/2005/atlantic/BT-IMAGES/2005-24
L-WILMA-A.gif>
Finally, a close-up depicting the track from the northeastern Yucatan
Peninsula across South Florida (including Florida counties) may be
accessed at:
<http://www.tropicalcyclone2005.com/database/2005/atlantic/BT-IMAGES/2005-24
L-WILMA-B.gif>
B. Brief Synoptic History
-------------------------
As mentioned above, around mid-October a very large, monsoon-like
circulation with an associated broad area of disturbed weather formed
over much of the Caribbean Sea. A concentrated area of convection with
surface low pressure formed near Jamaica around 14 October. Development
of this disturbed area was possibly aided by a couple of tropical waves
moving through the Caribbean around that time. The system had become
sufficiently organized that advisories were initiated on Tropical
Depression 24 at 2100 UTC. The center was estimated to be located about
75 nm southwest of Montego Bay, Jamaica. Steering currents were weak
and the depression moved slowly and erratically, primarily south-
southwestward to southward, over the next 2 or 3 days. Strengthening
was very slow and TD-24 was not upgraded to tropical storm status until
0900 UTC on 17 October when centered about 150 nm southeast of Grand
Cayman. Wilma thus became only the second 21st tropical storm to form
in the Atlantic basin during a season, the only other known occurrence
being on 15 November 1933.
On the 18th Tropical Storm Wilma turned toward the west-northwest and
was upgraded to the season's 12th hurricane while centered about 170 nm
south-southeast of Grand Cayman. This tied 1969's record number of
twelve hurricanes tracked during a single season. Wilma had developed
into a tropical depression and tropical storm very slowly, and had
required 24 additional hours to reach hurricane intensity (about
average), but late on the 18th and early on 19 October, one of the most
remarkable and explosive deepening episodes ever noted occurred. In a
span of 24 hours (18/1200 to 19/1200 UTC), Wilma intensified from a
65-kt minimal hurricane to a 160-kt monster storm. (More on the super
rapid intensification episode in Section C.) The highest FLW measured
by a U. S. Air Force reconnaissance plane was 168 kts at 700 mb in the
southeastern eyewall at 19/0619 UTC. Using the standard eyewall
reduction factor, this equates to 151 kts at the surface. The highest
MSW assigned operationally for Wilma was 150 kts, but in post-analysis
this was bumped up to 160 kts due to the fact that the pressure was
still falling some when the plane departed the storm, and during the
10-hour gap with no reconnaissance, the satellite signature suggested
that Wilma maintained intensity for several hours. Also, it is assumed
that following very rapid pressure falls there is a time lag before the
peak winds "catch up" with the drop in pressure.
Wilma slowly weakened as it moved northwestward toward the north-
eastern portion of the Yucatan Peninsula. The tiny, 2-nm diameter eye
was replaced with one ranging from 40 to 60 nm in diameter which was
maintained for most of Wilma's remaining lifetime. Winds were estimated
at 130 kts when the center made landfall on Cozumel Island around 2145
UTC on 21 October and were only slightly weaker when it crossed the coast
of the Yucatan Peninsula a few hours later. Wilma moved very slowly
northward, battering the northeastern Yucatan region, finally emerging
into the southern Gulf of Mexico around 23/0000 UTC as a Category 2
hurricane. A strong mid-tropospheric trough moving eastward from the
central U. S. provided an increasingly strong southwesterly steering
current that accelerated Wilma northeastward toward southern Florida.
The hurricane began to strengthen again and reached a secondary peak
of 110 kts as it neared the southwestern Florida coast.
Moving northeastward at 20-25 kts, Wilma made landfall near Cape
Romano around 1030 UTC on 24 October with the MSW estimated at 105 kts.
Wilma crossed the Florida Peninsula in only 4.5 hours, the center
emerging into the Atlantic southeast of Jupiter around 1500 UTC. The
intensity had decreased to 95 kts while crossing Florida, but the
hurricane re-intensified one final time late on the 24th with winds
peaking again near 110 kts around 25/0000 UTC. Following this, Wilma
began to enter an unfavorable environment and weakened while racing
northeastward at 40-50 kts over the western Atlantic. The former
Category 5 hurricane became an extratropical cyclone around 26/0000 UTC
while centered about 200 nm southeast of Halifax, Nova Scotia, and was
absorbed by another extratropical LOW located over eastern Nova Scotia
24 hours later.
C. Meteorological Extremes
--------------------------
(1) Record Low Central Pressure
-------------------------------
The officially accepted minimum CP of 882 mb in Wilma around 0800 UTC
on
19 October beats the old record of 888 mb measured in Hurricane Gilbert,
also in the Northwest Caribbean, on 13 September 1988. The actual SLP
reported by the dropsonde was 884 mb, but the surface wind was 23 kts, so
it is concluded that the drop was likely not in the center of the eye.
Using the rule of thumb explained last month in the summary for Hurricane
Rita, the pressure was decreased by 2 mb in order to arrive at what was
likely the lowest pressure in Wilma's eye. Given that the pressure had
been falling on successive drops early on 19 October, it is possible that
the CP dropped a little below 882 mb.
(2) Record Pressure Drop
------------------------
The rate at which Hurricane Wilma's CP plummeted was phenomenal. The
12-hour drop of 88 mb between 18/2000 UTC and 19/0800 UTC represents a
new world record for a 12-hour pressure fall, the previous being a drop
of 75 mb in Super Typhoon Irma in November, 1971. Wilma's peak 24-hour
drop of 98 mb sets a new record for the Atlantic, the previous being a
drop of 72 mb in 24 hours in Hurricane Gilbert. However, the world's
24-hour pressure fall record is still 101 mb in Super Typhoon Forrest
in September, 1983. The Atlantic basin's previous record 12-hour drop
in CP was 48 mb in Hurricane Allen in August, 1980.
Wilma's CP fell an astounding 57 mb in six hours, beating the old
Atlantic 6-hour pressure drop of 38 mb in Hurricane Beulah in September,
1967. Wilma's 6-hour CP drop also established a new world record in
this category, exceeding a 6-hour drop of 43 mb measured in Typhoon Opal
in September, 1967. To round out the pressure drop records, Wilma's CP
fell 31 mb in three hours, beating the 23-mb drop in three hours observed
in Super Typhoon June in November, 1975; and finally, at one point the
pressure in Wilma fell 10 mb in one hour, exceeding a one-hour drop of
8.5 mb measured in Atlantic Hurricane Opal in October, 1995.
(A special thanks to Karl Hoarau for sending me a summary of record
pressure falls observed in tropical cyclones. Some of the information
in the above paragraphs was taken from Karl's e-mail; some from the
official TPC/NHC report. It should be noted that the pressure drops
referenced in the official report are based upon CP estimates for
synoptic hours entered into the Best Track database. Hence, there are
some differences of a few millibars between those and Karl's values,
the latter representing the actual pressure falls for various time
periods.)
(3) Record Small Eye Diameter
-----------------------------
Around the time that Wilma's minimum pressure was observed, aerial
reconnaissance observations indicated that the cyclone's eye had
contracted to a diameter of 2 nm. This is the smallest eye ever noted
in an Atlantic hurricane.
(4) Record Rainfall
-------------------
The Meteorological Service of Mexico reported a 24-hour rainfall total
of 62.05 inches (1576.1 mm) measured on Isla Mujeres near Cancun. As far
as is known to the author, this establishes a new world record for rain-
fall in a 24-hour period over non-mountainous terrain. The old record
was around 42 inches (1067 mm) measured at Alvin, Texas, in association
with Tropical Storm Claudette in July, 1979.
(5) Peak Wind Considerations
----------------------------
As noted above, the maximum 700-mb FLW measured in Wilma was 168 kts,
which was reduced to 150 kts at the surface, and was the highest MSW
reported operationally for the hurricane. I have in my possession an
from e-mail Mark Lander shedding some light on the problems inherent in
trying to measure the actual peak winds in very small hurricanes. Mark's
comments follow:
"I have another concern. Given that the eye of Wilma was only 2 miles
across and that the hurricane-force winds extended out only 15 miles, is
it possible that the aircraft (flying at 300 mph, or whatever) registers
a spatially-averaged wind when flying across a wind max that may only
be 0.5 miles wide? Even at 300 mph, the plane will cover a distance of
5 miles in one minute, and one mile every 12 seconds! So in 12 seconds,
the flight-level wind will be the average of 1 mile of air, and in one
minute, the flight-level wind will be the average of 5 miles of air!
Quite a long distance given the dimensions of Wilma at peak intensity.
"To make a long story short, I postulate that the flight-level wind
is a sort of area average, and in very small hurricanes may underestimate
the sharp peak by a considerable amount."
D. Damage and Casualties
------------------------
Wilma dealt a major blow to the tourist industry in the northeastern
Yucatan Peninsula, an area which suffered severely from the prolonged
exposure to destructive winds, high tides and torrential rainfall due to
the hurricane's very slow movement in that region. However, detailed
figures are not available from Mexico. In southern Florida damage was
unusually widespread, including substantial crop losses, many downed
trees and power line poles, extensive roof damage, and many mobile
homes destroyed. Hurricane Wilma caused the largest disruption of
electrical service ever experienced in Florida with 98% of customers
in the southern part of the peninsula losing service. Power outages
were reported in 42 Florida counties. Total insured damages have been
estimated at $6.1 billion by the Property Claims Service. Doubling this
amount to obtain the total damage gives an estimate of Wilma's damage
to the U. S. around $12.2 billion.
Fatalities attributed to Hurricane Wilma include 12 in Haiti, 1 in
Jamaica, 4 in Mexico, and 5 in Florida for a total of 22 deaths.
(Report written by Gary Padgett, based primarily on the official TPC/NHC
report, and with contributions by Karl Hoarau and Mark Lander)
TROPICAL STORM ALPHA
(TC-25)
22 - 24 October
----------------------------------------
As the TPC/NHC official report on Tropical Storm Alpha is already
available online, this report will be brief. Alpha was the 22nd named
tropical cyclone of the 2005 Atlantic hurricane season, besting the
previous record of 21 storms set in 1933. For the first time Greek
alphabet letter names were used to designate Atlantic tropical storms.
Through the latter 1950s the annual list of names utilized all 26 letters
of the English alphabet, but beginning with the 1960 season, when
rotating sets were introduced, names beginning with the letters Q, U, X,
Y and Z were omitted, leaving 21 names available for each year's
cyclones. I am not exactly sure when the idea of using Greek letter
names as a backup was conceived. I first learned that this was the
backup plan for the Eastern North Pacific basin in 1992 after that
basin's list of names was exhausted during that very active season.
(In 1992, no further storms formed following Tropical Storm Zeke in late
October, so no Greek names were assigned.) It was around the mid-1990s
that I became aware that the Atlantic would also "go Greek" if more than
21 names were required.
Alpha formed from a tropical wave which reached the Windward Islands
on 19 October. Shear was light over the eastern Caribbean Sea and the
disturbance gradually became organized with the first advisory on
Tropical Depression 25 being issued at 1500 UTC on 22 October, placing
the center about 185 nm southeast of Santo Domingo in the Dominican
Republic. The depression was christened Tropical Storm Alpha at 2100
UTC. Dvorak ratings from all three satellite agencies at 1800 UTC were
T2.0/2.0, but the cloud pattern had continued to improve since that
time. Also, ship C6FN4 had reported 22-kt winds at 1800 UTC about 30 nm
southeast of the center with a SLP of 1007 mb. The tropical storm
continued to intensify and reached its peak intensity of 45 kts with a
CP of 998 mb around 0600 UTC on 23 October as it was nearing the coast
of the Dominican Republic.
Tropical Storm Alpha made landfall near the town of Barahona around
23/1000 UTC. A meteorological station in the area reported sustained
winds of 45 kts as the center of Alpha moved inland. Following landfall
the cyclone quickly weakened over the high mountains of Hispaniola, being
downgraded to a tropical depression at 1500 UTC. The depression then
turned toward the north-northwest and then north over the southeastern
Bahamas, never regaining tropical storm status. By 0000 UTC on the 25th
Alpha's circulation had been absorbed into the much larger circulation
of Hurricane Wilma.
A graphic depicting the track of Tropical Storm Alpha may be found at
the following link:
<http://www.tropicalcyclone2005.com/database/2005/atlantic/BT-IMAGES/2005-25
L-ALPHA.gif>
Press reports attribute 26 deaths to Tropical Storm Alpha: seventeen
in Haiti and nine more in the Dominican Republic, primarily from mud-
slides caused by the heavy rains. Also, in Haiti floods and mudslides
damaged or destroyed at least 400 homes.
(Report written by Gary Padgett, based on official TPC/NHC storm report
authored by Lixion Avila)
HURRICANE BETA
(TC-26)
27 - 31 October
-----------------------------------
A. Introduction and Storm Origins
---------------------------------
Hurricane Beta was the 14th hurricane and 7th major hurricane of the
remarkable 2005 Atlantic tropical cyclone season. This is the highest
number of Category 3+ hurricanes to form in a single season since 1950,
when there were eight. Operationally, Beta was the 13th hurricane, as
this was before Cindy had been officially upgraded to hurricane status
during post-analysis.
Hurricane Beta developed slowly from a large, slow-moving area of
disturbed weather deep in the southwestern Caribbean Sea that was first
mentioned in NHC's Tropical Weather Outlook at 1130 UTC 25 October.
The system gradually became better organized on 26 October while drifting
slowly northwestwards and was upgraded to Tropical Depression 26 at
27/0300 UTC while located approximately 150 nm east-southeast of
Bluefields, Nicaragua. Situated in very favourable environmental
conditions, it became Tropical Storm Beta at 27/0900 UTC while located
about 65 nm south of San Andres Island and around 120 nm east-southeast
of Bluefields, Nicaragua. The upgrade was based upon satellite intensity
estimates of 35 kts, and the discussion noted that the MSW was that low
due only to Dvorak method restraints. Thus, Beta became the 23rd
tropical storm of the record-breaking 2005 season.
B. Synoptic History
-------------------
The northwesterly heading became more northerly as Tropical Storm
Beta headed towards a weakness in the subtropical ridge induced by a
large deep-layer trough located over the eastern United States. The
cyclone increased its intensity on 27 October, but easterly shear over
the system hindered further strengthening on 28 October. However, Beta
remained a strong 55-kt tropical storm while moving progressively
closer to the islands of San Andres and Providencia. The center of
Beta moved over or very near the island of Providencia during the
evening of 28 October (local time), and sustained winds up to 55 kts
were reported. Convection was increasing again with a vengeance, and
it appeared that Beta was on the verge of reaching hurricane intensity.
Tropical Storm Beta was upgraded to the (at the time) 13th hurricane
of the 2005 season in the intermediate advisory issued at 29/0600 UTC.
The centre was located just northwest of the island of Providencia or
approximately 130 nm southeast of Cabo Gracias a Dios on the Nicaragua/
Honduras border. A 29/0211 UTC SSM/I overpass, not available for the
previous advisory, revealed a very small eye within the deepest
convection, so it was considered likely that Beta had been a hurricane
at 29/0000 UTC. The environment was highly conducive for further
strengthening, and it was just a matter of how strong Beta could become
before its predicted landfall in Nicaragua.
At the time of its upgrade to hurricane status, Beta was moving very
slowly northwestwards, and shortly afterward began to slowly turn
westwards on 29 October in response to a ridge building to its north.
Also, once the easterly shear relaxed, intensification proceeded more
rapidly. Reports from a Hurricane Hunter plane around midday on the 29th
found 700-mb flight-level winds of 77 kts just north of the centre and
the CP extrapolated from the dropsondes was 979 mb. The very small eye
was measured to be 10 nm in diameter. Beta's intensity had reached
80 kts by 1800 UTC but remained plateaued there for about 12 hours.
Satellite imagery early on 30 October revealed that the eye was
surrounded by a solid ring of deep convection with cloud tops as low
as -80 Deg C.
Turning to the southwest, Hurricane Beta continued to strengthen and
was upgraded to a Category 2 hurricane on the Saffir/Simpson scale with
90-kt winds at 30/0300 UTC. The hurricane reached its peak intensity of
100 kts, or Category 3 on the Saffir/Simpson scale, around 0600 UTC
while located about 45 nm south-southeast of Puerto Cabezas, Nicaragua.
The MSW was not upped to 100 kts until the 0900 UTC advisory, but the
discussion bulletin at that hour makes it clear that Beta's intensity
was likely 100 kts three hours earlier. All the satellite agencies
were reporting T5.5/102 kts at that hour. At its peak, Hurricane Beta
was a small hurricane with hurricane-force winds extending outward from
the center only 15 nm, while the diameter of the zone experiencing
gales was only about 100 nm.
By 30/0900 UTC the satellite signature was beginning to deteriorate
some, and Beta's MSW had weakened to 90 kts by the time the center made
landfall near La Barra, Nicaragua, around 1200 UTC. Beta rapidly
weakened as it moved further into Nicaragua and was downgraded to a
55-kt tropical storm at 30/2100 UTC, and to a tropical depression by the
time the final NHC advisory was issued at 31/0300 UTC. The weakening
25-kt depression was then located about 115 km east-northeast of Managua,
Nicaragua. The remnants of Beta continued to be monitored as they
made their journey westwards across Central America, but dissipated
over the mountainous terrain before reaching the Eastern North Pacific.
A graphic displaying the track of Hurricane Beta may be found at the
following link:
<http://www.tropicalcyclone2005.com/database/2005/atlantic/BT-IMAGES/2005-26
L-BETA.gif>
C. Damage and Casualties
------------------------
Hurricane Beta caused widespread damage on Providencia Island, and
extensive damage to structures was reported along the central
Nicaraguan coast. Also, significant flooding was reported in Honduras
with some areas receiving more than 400 mm of rain. Dozens of
communities were flooded, hundreds of buildings damaged, and crops
destroyed throughout the region. In Nicaragua more than 7000 persons
were affected by Beta with many of them left homeless. Very fortunately,
no fatalities were reported due to Hurricane Beta.
(Report written by Kevin Boyle and Gary Padgett)
*************************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for October: 1 tropical depression
1 hurricane **
** - storm formed in September and was covered in the September summary
Sources of Information
----------------------
Most of the information presented below was obtained from the
various tropical cyclone products issued by the Tropical Prediction
Center/National Hurricane Center (TPC/NHC) in Miami, Florida (or the
Central Pacific Hurricane Center (CPHC) in Honolulu, Hawaii, for
locations west of longitude 140W): discussions, public advisories,
forecast/advisories, tropical weather outlooks, special tropical
disturbance statements, etc. Some additional information may have
been gleaned from the monthly summaries prepared by the hurricane
specialists and available on TPC/NHC's website. All references to
sustained winds imply a 1-minute averaging period unless otherwise
noted.
SPECIAL NOTE!!! Many of the official TPC/NHC tropical cyclone reports
are now available online at the following link:
<http://www.nhc.noaa.gov/2005epac.shtml>
Northeast Pacific Tropical Activity for October
-----------------------------------------------
As the month of October opened, Hurricane Otis was reaching its peak
intensity of 90 kts about 125 nm west-southwest of Cabo San Lucas on the
southern tip of the Baja California Peninsula. Otis soon began to weaken
rapidly and had dissipated by the afternoon of 3 October. While the
month of September had seen a rather impressive outbreak of tropical
cyclone activity in the Northeast Pacific basin, Otis proved to be the
final named cyclone of the 2005 season. Advisories were issued on one
additional tropical system during October. Tropical Depression 16E
formed on 15 October a few hundred miles to the south of Acapulco and
pursued a fairly straight westerly track at low latitudes for several
days. Advisories were discontinued at 0300 UTC on 18 October when the
system appeared to be dissipating, but were re-initiated 36 hours later
when the depression seemed to take on new life. Following this brief
re-flowering on the 19th, the TD-16E began to slowly weaken once more
and had dissipated by 1800 UTC on 20 October while located several
hundred miles to the southwest of Cabo San Lucas.
The most interesting episode in the life of TD-16E occurred very early
on 17 October (UTC). At 17/0000 UTC, TAFB, SAB and AFWA all classified
the system at T2.5 (35 kts), based on improved banding features and cloud
tops colder than -70 C over the western half of the circulation. The
decision was made to upgrade the depression to Tropical Storm Pilar, but
shortly before advisory release time at 0300 UTC, shortwave infrared
imagery revealed that the center had become sheared farther to the
southeast of the banding feature and that convective cloud tops had
warmed considerably. Therefore, the responsible forecaster decided to
keep the cyclone at depression status for the time being, but the
weakening trend continued and TD-16E was never officially upgraded to
a tropical storm. There was a chance that it might be upgraded to a
tropical storm in post-storm analysis, but the official TPC/NHC report
on Tropical Depression 16E is now available online and that action was
not taken. A graphic depicting the track of this tropical depression
may be accessed at the following link:
<http://www.tropicalcyclone2005.com/database/2005/e_pacific/BT-IMAGES/2005-1
6E-NONAME.gif>
*************************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for October: 3 tropical depressions **
3 typhoons ++
** - only one of these was treated as a tropical depression by JTWC
++ - one of these formed in September and was covered in the September
summary
NOTE!!! The Northwest Pacific basin will be covered in the second
installment of the October summary.
*************************************************************************
NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea
Activity for October: 2 tropical cyclones **
** - both of these were classified as minimal tropical storms by JTWC.
One was treated as a deep depression by IMD, the other was never
classified as a depression by that agency.
NOTE!!! The North Indian Ocean basin will be covered in the second
installment of the October summary.
*************************************************************************
SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E
Activity for October: 1 tropical depression
NOTE!!! The Southwest Indian Ocean basin will be covered in the second
installment of the October summary.
*************************************************************************
NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E
Activity for October: No tropical cyclones
*************************************************************************
NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E
Activity for October: No tropical cyclones
*************************************************************************
SOUTH PACIFIC (SPA) - South Pacific Ocean East of Longitude 160E
Activity for October: No tropical cyclones
*************************************************************************
SPECIAL FEATURE - SOURCES OF TROPICAL CYCLONE INFORMATION
The purpose of this section is to list some websites where many and
varied types of tropical cyclone information are archived. Many readers
will know about these already, but for the benefit of those who don't,
I wanted to include them.
(1) Aircraft Reconnaissance Information
---------------------------------------
Various types of messages from reconnaissance aircraft may be
retrieved from the following FTP site:
<ftp://ftp.nhc.noaa.gov/pub/products/nhc/recon/>
Information regarding how to interpret the coded reconnaissance
messages may be found at the following URL:
<http://www.nhc.noaa.gov/reconlist.shtml>
Links are also included to websites with further information about the
U. S. Air Force 53rd Weather Reconnaissance Squadron and the NOAA Air-
craft Operations Center.
(2) Archived Advisories
-----------------------
All the advisory products (public advisories, forecast/advisories,
strike probabilities, discussions, various graphics) issued by TPC/NHC
are archived on TPC's website. For the current year (using 2004 as an
example), the archived products can be found at:
<http://www.nhc.noaa.gov/archive/2004/index.shtml>
Links to tropical products archives for earlier years are available at
the following URL:
<http://www.nhc.noaa.gov/pastall.shtml>
JTWC warnings for past storms are archived on the NRL Monterry website:
<http://www.nrlmry.navy.mil/tc_pages/tc_home.html>
On the NRL site, the link to past years can be found in the upper left
corner of the screen.
I am not aware at the moment of any other TCWC which archives all
its tropical cyclone warning/advisory products for public access, but
if I learn of any, I will add them to this list.
(3) Satellite Imagery
---------------------
Satellite images of tropical cyclones in various sensor bands are
available on the NRL Monterrey and University of Wisconsin websites,
courtesy of Jeff Hawkins and Chris Velden and their associates. The
links are:
<http://www.nrlmry.navy.mil/tc_pages/tc_home.html>
<http://cimss.ssec.wisc.edu/tropic/tropic.html>
On the NRL site, the link to past years can be found in the upper left
corner of the screen. For the CIMSS site, a link to data archives is
located in the lower left portion of the screen.
Additional tropical satellite imagery, along with looping ability for
composite microwave imagery for the Western Hemisphere north of the
equator, can be found at:
(1) For the Eastern North Pacific:
<http://www.ssd.noaa.gov/PS/TROP/trop-epac.html>
(2) For the Atlantic, Gulf of Mexico and Caribbean Sea:
<http://www.ssd.noaa.gov/PS/TROP/trop-atl.html>
I'm sure there are other sites with available imagery available, and
as I learn of them, I will add the links to this list.
*************************************************************************
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 August, 1998
summary. I don't normally include the Glossary in most months in
order to help keep them from being too long. If anyone would like to
receive a copy of the Glossary, please e-mail me and I'll be happy
to send them a copy.
*************************************************************************
AUTHOR'S NOTE: This summary should be considered a very preliminary
overview of the tropical cyclones that occur in each month. The cyclone
tracks (provided separately) will generally be based upon operational
warnings issued by the various tropical cyclone warning centers. The
information contained therein may differ somewhat from the tracking and
intensity information obtained from a "best-track" file which is based
on a detailed post-seasonal analysis of all available data. Information
on where to find official "best-track" files from the various warning
centers will be passed along from time to time.
The track files are not being sent via e-mail. They can be retrieved
from the archive sites listed below. (Note: I do have a limited e-mail
distribution list for the track files. If anyone wishes to receive
these via e-mail, please send me a message.)
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. Back issues can be obtained from the following websites
(courtesy of Michael Bath, Michael V. Padua, Michael Pitt, Chris
Landsea, and John Diebolt):
<http://australiasevereweather.com/cyclones/>
<http://www.typhoon2000.ph>
<http://mpittweather.com>
<ftp://ftp.aoml.noaa.gov/hrd/pub/landsea/padgett/>
<http://www.tropicalcyclone2005.com/>
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.metoffice.gov.uk/weather/tropicalcyclone>
TROPICAL CYCLONE REPORTS AVAILABLE
JTWC now has available on its website the Annual Tropical Cyclone
Report (ATCR) for 2004 (2003-2004 season for the Southern Hemisphere).
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 2004 Atlantic and Eastern North Pacific
tropical cyclones; also, storm reports for all the 2004 Atlantic
and Eastern North Pacific cyclones are now available, as well as
track charts and reports on storms from earlier years.
The URL is: <http://www.nhc.noaa.gov>
A special thanks to Michael Bath of McLeans Ridges, New South Wales,
Australia, for assisting me with proofreading the summaries.
PREPARED BY
Gary Padgett
E-mail: garyp@alaweb.com
Phone: 334-222-5327
Kevin Boyle (Northwest Pacific)
E-mail: newchapelobservatory@btinternet.com
Simon Clarke (Northeast Australia/Coral Sea, South Pacific)
E-mail: saclarke@iprimus.com.au
*************************************************************************
*************************************************************************
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
To unsubscribe, e-mail LISTSERV@UIUC.EDU with "unsub wx-atlan" in the
body of the message or e-mail chris@lib.siu.edu for help. Products are also available directly from NHC via e-mail. See: http://www.nhc.noaa.gov/signup.shtml for available products and sign-up.
This archive was generated by hypermail 2b29 : Fri Dec 05 2008 - 02:15:09 EST