[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 171756
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON OCT 17 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM
THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON
SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...

TROPICAL STORM WILMA IS CENTERED NEAR 16.1N 80.0W AT 17/1800
UTC...OR 205 NM SSE OF GRAND CAYMAN...MOVING SW 4 KT. MAXIMUM
SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 997 MB. SEE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE
PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT4/WTNT34 KNHC
FOR MORE DETAILS. WILMA CONSISTS OF A LARGE CLUSTER OF NUMEROUS
STRONG CONVECTION JUST OFFSHORE THE HONDURAS/NICARAGUA COAST
FROM 12N-16.5N BETWEEN 78W-84W. THE CENTER IS BECOMING MORE
EMBEDDED BENEATH THIS CLUSTER AND IS ALSO SHOWING SIGNS OF SOME
INCREASED BANDING WRAPPING AROUND THIS CENTER. AN UPPER
TROUGH/SHEAR AXIS EXTENDS FROM CNTRL CUBA ACROSS THE CAYMAN
ISLANDS TO THE GULF OF HONDURAS AND IS PLACING SOME NORTHERLY
SHEAR OVER WILMA...AS WELL AS INFILTRATING SOME DRIER AIR INTO
THE CIRCULATION. OUTFLOW IS BEST ACROSS THE SE SEMICIRCLE DUE TO
THE RIDGE AXIS BEING ORIENTED FROM NICARAGUA TO HISPANIOLA. AS
SUCH...SCATTERED MODERATE/STRONG CONVECTION ALSO LIES E OF THE
MAIN CORE CONVECTION FROM 14N-21N BETWEEN 71W-77W EXTENDING OVER
PARTS OF JAMAICA...HISPANIOLA...AND E CUBA.

...TROPICAL WAVES...

CENTRAL ATLANTIC TROPICAL WAVE ALONG 44W S OF 20N MOVING W 10 KT
WITH A WEAKENING 1012 MB LOW ALONG THE AXIS NEAR 15N44W. THE LOW
DOES NOT APPEAR TO HAVE A CLOSED CIRCULATION ANY LONGER...BUT
SHIP AND BUOY OBSERVATIONS STILL INDICATE A GENERAL MINIMUM IN
PRESSURE. SCATTERED MODERATE CONVECTION FROM 13N-18N BETWEEN
39W-46W.

A TROPICAL WAVE IS ADDED JUST E OF THE LESSER ANTILLES ALONG 60W
S OF 16N MOVING W 10-15 KT. THE WAVE IS ADDED BASED ON UPPER AIR
DATA FROM CAYENNE WHICH INDICATED A SHARP WIND SHIFT BETWEEN 900
AND 700 MB LATE ON OCT 15. THE WAVE IS MOVED W BY EXTRAPOLATION
AND CLOSELY FOLLOWS A CLUSTER OF NUMEROUS MODERATE CONVECTION
MOVING ACROSS THE WINDWARD ISLANDS FROM 11N-14N BETWEEN 58W-63W.
THE HEAVIEST RAINFALL CURRENTLY EXTENDS BETWEEN MARTINIQUE AND
THE GRENADINES...AND EWD TO BARBADOS.

CENTRAL CARIBBEAN TROPICAL WAVE EXTENDS FROM HAITI SWD ALONG 73W
MOVING W 10 KT. THE WAVE IS INCHING CLOSER AND CLOSER TO T.S.
WILMA AND HAS RELATIVELY LITTLE SIGNATURE OF ITS OWN.
HOWEVER...A LARGE AREA OF DEEP CONVECTION EXTENDS FROM
HISPANIOLA SWWD FOR ABOUT 300 NM AND THIS COULD BE PARTLY CAUSED
BY THE WAVE MOVING INTO THE AREA. SCATTERED MODERATE/STRONG
CONVECTION FROM 14N-21N BETWEEN 71W-77W. THE HEAVIEST ACTIVITY
CURRENTLY LIES OFFSHORE S OF JAMAICA AND HAITI BUT SOME OF THE
SHOWERS/TSTMS HAVE BEEN SPREADING N AND E OVER THE NEARBY
ISLANDS.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 10N6W 6N14W 8N28W 8N41W...THEN ALONG
13N45W 8N58W. ISOLATED SHOWERS/TSTMS FROM 3N-7N BETWEEN 10W-25W.
SCATTERED MODERATE/ISOLATED STRONG COVERING A LARGE AREA FROM
3N-11N BETWEEN 28W-43W. CLUSTER OF SCATTERED MODERATE FROM
10N-14N BETWEEN 48W-52W.

...DISCUSSION...

GULF OF MEXICO...
STRONG HIGH PRES IN THE UPPER LEVELS IS CENTERED OVER THE BAY OF
CAMPECHE NEAR 23N94W AND IS DRIVING DRY AND STABLE AIR SWD OVER
THE E PART OF THE AREA...THEN CURLING IT BACK TO THE W ACROSS
THE YUCATAN INTO THE BAY OF CAMPECHE. SKIES ARE MOSTLY
CLEAR...ESPECIALLY N OF 27N...AND ONLY PATCHY CLOUDS WITH
ISOLATED SHOWERS ARE MOVING S NEAR THE W COAST OF THE YUCATAN. A
WEAK COLD FRONT IS DRIFTING SWD FROM NEAR CAPE CANAVERAL FLORIDA
WWD TO 27N90W AND IS MAINLY MARKED BY AN ADDITIONAL DEWPOINT
DROP. DEWPOINTS HAVE FALLEN INTO THE MID-60S F INTO SOUTH
FLORIDA FROM THE PREVIOUS FRONT A COUPLE OF DAYS AGO...AND ARE
NOW FALLING AS LOW AS THE MID-40S F IN THE FLORIDA PANHANDLE
BEHIND THIS NEW FRONT. THE ATMOSPHERE WILL REMAIN MOSTLY DRY
OVER THE AREA FOR THE NEXT FEW DAYS BUT WILL GRADUALLY INCREASE
FROM THE SE LATER IN THE WEEK AS T.S. WILMA APPROACHES FROM THE
CARIBBEAN.

CARIBBEAN...
THE CIRCULATION OF T.S. WILMA ENCOMPASSES THE ENTIRE W HALF OF
THE CARIBBEAN...AND BROAD E/SE FLOW FEEDING INTO THE CIRCULATION
COVERS THE REST OF THE AREA. THE UPPER LEVEL ANTICYCLONE OVER
WILMA IS NOT WELL-DEFINED AT THE MOMENT BUT THE RIDGE AXIS
EXTENDING FROM 15N76W NEWD PAST THE DOMINICAN REPUBLIC IS
PRODUCING EXCELLENT OUTFLOW OVER THE CONVECTION LOCATED FROM
JAMAICA TO HISPANIOLA. A SIGNIFICANT AREA OF DRY AIR AND STRONG
SUBSIDENCE EXTENDS NW OF AN UPPER LEVEL TROUGH/SHEAR AXIS WHICH
STRETCHES FROM CNTRL CUBA SW INTO THE GULF OF HONDURAS...AND
THIS FEATURE APPEARS TO BE AT LEAST TEMPORARILY AFFECTING WILMA
WITH SOME NORTHERLY SHEAR. FARTHER E...THE WEATHER IS A LITTLE
LESS CONVECTIVE E OF 70W WITH THE EXCEPTION OF SHOWERS/TSTMS
MOVING ACROSS THE WINDWARD ISLANDS IN ASSOCIATION WITH A
TROPICAL WAVE. DRIER AIR IS EXPECTED TO BEGIN MOVING INTO THE
AREA FROM THE E OVER THE NEXT 24 HRS...HANGING AROUND OVER THE E
CARIBBEAN AT LEAST THROUGH THU NIGHT BEFORE THE ARRIVAL OF THE
NEXT WAVE.

ATLANTIC...
A WEAK COLD FRONT EXTENDS FROM BERMUDA SW TO CAPE CANAVERAL
FLORIDA...MARKED BY A ROPE CLOUD AND LOWER DEWPOINTS. A SURFACE
TROUGH MARKED BY A NE/SE WIND SHIFT EXTENDS FROM T.S. WILMA IN
THE CARIBBEAN NWD ACROSS CNTRL CUBA TO THE CNTRL BAHAMAS WITH
MOISTURE BEHIND THE TROUGH PRODUCING WIDELY SCATTERED
SHOWERS/TSTMS S OF 26N BETWEEN 67W-77W INCLUDING OVER THE SRN
BAHAMAS. A MID-OCEANIC TROUGH IS EMBEDDED ALONG 28N64W
15N58W...EXTENDING FROM A MUCH LARGER W ATLC TROUGH...AND IS
COLLOCATED WITH LOW-LEVEL CONVERGENCE N OF THE SUBTROPICAL RIDGE
TO PRODUCE SCATTERED MODERATE CONVECTION N OF THE NRN LEEWARD
ISLANDS FROM 19N-25N BETWEEN 61W-65W. A SECOND UPPER TROUGH/LOW
IS CENTERED OVER THE TROPICAL ATLC NEAR 20N40W AND IS NEAR A
WEAK 1016 MB LOW NEAR 23N38W. A SURFACE TROUGH EXTENDS SW OF THE
LOW TO THE TROPICAL WAVE ALONG 44W AND IS PRODUCING SCATTERED
SHOWERS/TSTMS FROM 17N-23N BETWEEN 36W-42W. AN UPPER RIDGE LIES
ALONG 8N E OF 40W AND THE ASSOCIATED DIFFLUENCE ALOFT HAS
INITIATED A LARGE AREA OF ITCZ CONVECTION BETWEEN 28W-35W.
FARTHER E...A SHARP UPPER TROUGH IS SWINGING PAST THE CANARY
ISLANDS ALONG 32N12W 26N15W 21N29W WITH A COLD FRONT AND TROUGH
BRINGING COOLER AND MORE STABLE AIR TOWARDS THE MOROCCAN COAST.
THE TROUGH IS ALSO PUSHING THIS AIR SWD OVER THE E
ATLC...FORCING A LARGE AREA OF SAHARAN DUST S OF 23N AND E OF
40W.

$$
BERG


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