[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 282347
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI OCT 28 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURE...

TROPICAL STORM BETA IS CENTERED NEAR 13.4N 81.3W...OVER THE
ISLAND OF PROVIDENCIA AND 135 NM ESE OF PUERTO CABEZAS
NICARAGUA...AT 29/0000 UTC MOVING NNW 4 KT. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 990 MB. MAXIMUM SUSTAINED WIND SPEED IS 55
KT WITH GUSTS TO 65 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC AND THE PUBLIC ADVISORY
UNDER HEADERS MIATCPAT1/WTNT31 FOR MORE DETAILS. BETA HAS
MAINTAINED ITS INTENSITY FOR MUCH OF THE DAY AND THE CONVECTIVE
PATTERN REFLECTS THIS WITH VERY LITTLE CHANGE IN THE STRUCTURE.
THE TSTM ACTIVITY COMES AND GOES IN BURSTS WITH THE STRONGEST
CONVECTION ISOLATED NEAR THE CENTER. ONE PRIMARY SPIRAL BAND IS
NOTED EXTENDING N AND E...MELDING INTO ADDITIONAL CONVECTION
WHICH HAS FORMED NEAR THE CAYMAN ISLANDS. NUMEROUS MODERATE/
STRONG CONVECTION IS FROM 11N-16N BETWEEN 80W-83W. TEN TO
FIFTEEN INCHES OF RAIN ARE EXPECTED OVER PARTS OF NICARAGUA...NE
HONDURAS...AND THE ISLANDS OF SAN ANDRES AND PROVIDENCIA DUE TO
THE SLOW N/NW MOVEMENT OF BETA OVER THE NEXT FEW DAYS.

...TROPICAL WAVES...

CENTRAL ATLANTIC TROPICAL WAVE ALONG 45W S OF 19N MOVING W 10-15
KT. A WELL-DEFINED AND ALMOST CIRCULAR LOW-LEVEL CIRCULATION IS
ASSOCIATED WITH THE WAVE...AND IT ALMOST APPEARS THAT A WEAK LOW
COULD BE CENTERED NEAR 12N45W. SCATTERED MODERATE CONVECTION HAS
DEVELOPED IN A SMALL AREA NW OF THE LOW FROM 12N-16N BETWEEN
44W-48W.

EAST/CENTRAL CARIBBEAN TROPICAL WAVE ROUGHLY ALONG 67W S OF 20N
MOVING W 10-15 KT. VISIBLE SATELLITE IMAGERY ACTUALLY SUGGESTS
THAT THE WAVE MAY HAVE A STRONG NE/SW TILT NOTED BY A LINE OF
TSTMS EXTENDING FROM THE MONA PASSAGE SW TO THE GUAJIRA
PENINSULA OF COLOMBIA. WIDELY SCATTERED MODERATE CONVECTION
EXTENDS FROM 16N-20N BETWEEN 65W-70W STRETCHING FROM THE VIRGIN
ISLANDS ACROSS PUERTO RICO TO THE DOMINICAN REPUBLIC. NUMEROUS
MODERATE IS FROM 12N-19N BETWEEN 69W-75W MAINLY FROM HAITI SWD.

WEST CARIBBEAN TROPICAL WAVE ALONG 78W S OF 19N MOVING W 10 KT.
THE SIGNATURE OF THE WAVE IS BECOMING INCREASINGLY DIFFUSE AS IT
BECOMES INCORPORATED INTO THE CIRCULATION OF T.S. BETA.
THEREFORE...THE WAVE WILL BE REMOVED ON THE 0000 UTC ANALYSIS.

...ITCZ...

ITCZ AXIS IS ALONG 11N4W 5N15W 4N31W 15N42W...THEN ALONG 10N46W
12N61W. SCATTERED MODERATE/STRONG CONVECTION INLAND OVER W
AFRICA FROM GUINEA-BISSAU SEWD TO LIBERIA...BEGINNING TO MOVE
OFFSHORE. WIDELY SCATTERED MODERATE FROM EQ-9N BETWEEN 15W-21W.
ISOLATED SHOWERS/TSTMS WITHIN 180 NM OF THE AXIS BETWEEN
21W-35W. SCATTERED MODERATE FROM 6N-12N BETWEEN 53W-63W PARTLY
DUE TO AN UPPER LOW NEAR 11N58W IS BRUSHING ACROSS TRINIDAD...NE
VENEZUELA...N GUYANA...N SURINAME...AND N FRENCH GUIANA.

...DISCUSSION...

GULF OF MEXICO...
DRY AIR CONTINUES TO FILTER INTO THE AREA FROM THE N VIA A LARGE
MID-LATITUDE UPPER TROUGH EXTENDING FROM NEW ENGLAND TO THE
LOWER MISSISSIPPI VALLEY. A DISORGANIZED BAND OF LOW/MID LEVEL
CLOUDS EXTENDS FROM NEAR TAMPA FLORIDA SW TO VERACRUZ MEXICO AND
IS LIKELY THE LEADING EDGE OF A SECONDARY SURGE OF THE DRIER
AIR. SSM/I IMAGERY AND UPPER AIR DATA FROM THE N GULF COAST
INDICATE THAT PRECIPITABLE WATER VALUES HAVE DROPPED BELOW 0.50"
OVER THE N GULF WATERS...AND ONLY INCREASE TO ABOUT 1.5" OVER
THE SRN GULF. THE HIGHEST VALUES (OVER 2.0") ARE LOCATED ALONG
THE MEXICAN COAST WHERE NELY FLOW IS POOLING MOISTURE AGAINST
THE SIERRA MADRES...AND THIS IS VERIFIED BY LOW CLOUDS/DRIZZLE
WHICH LIE OVER THE COASTAL PLAINS N OF VERACRUZ TO THE RIO
GRANDE. LITTLE CHANGE IS EXPECTED IN THE OVERALL PATTERN THROUGH
THE WEEKEND WITH MOISTURE STILL TRAPPED OVER ERN MEXICO UNTIL AT
LEAST EARLY NEXT WEEK. A COLD FRONT IS EXPECTED TO MOVE OFF THE
TEXAS COAST TUE MORNING WITH INCREASING MOISTURE OVER THE E GULF
AHEAD OF THE BOUNDARY.

CARIBBEAN...
T.S. BETA IS STILL LOCATED OFF THE NICARAGUAN COAST AND IS
SLOWLY DRIFTING N PAST PROVIDENCIA ISLAND. SEE SPECIAL FEATURES
FOR FURTHER DISCUSSION. A LARGE UPPER LEVEL HIGH IS CENTERED
JUST S OF HISPANIOLA NEAR 17N73W AND IS INTERACTING WITH THE
TROPICAL WAVE OVER THE CNTRL CARIBBEAN TO PRODUCE A BROAD AREA
OF SCATTERED MODERATE CONVECTION EXTENDING S OF HAITI TO NRN
COLOMBIA AND VENEZUELA. THE WAVE IS USHERING IN DRIER AIR OVER
THE E CARIBBEAN AND IS GETTING SOME HELP FROM MODERATE
SUBSIDENCE ON THE W SIDE OF AN UPPER LOW LOCATED N OF GUYANA
NEAR 12N59W. THIS IS PRODUCING TRANQUIL WEATHER FROM TRINIDAD
NWD ACROSS THE ENTIRE LESSER ANTILLES CHAIN TO THE VIRGIN
ISLANDS. ELSEWHERE...MOISTURE FROM BETA IS BEING DRAWN NWD BY
THE SUBTROPICAL JET AND THERE IS AMPLE LOW-LEVEL CONVERGENCE TO
PRODUCE SCATTERED MODERATE CONVECTION FROM 16N-22N BETWEEN
79W-83W EXTENDING ACROSS THE CAYMAN ISLANDS AND CNTRL CUBA.
DRIER WEATHER EXTENDS W OF 84W TO THE YUCATAN PENINSULA DUE TO
SUBSIDENCE ASSOCIATED WITH THE GULF OF MEXICO UPPER TROUGH.

WEST ATLANTIC...
AN UPPER LEVEL SHORTWAVE EXTENDING FROM COASTAL SOUTH CAROLINA
TO N FLORIDA IS EMBEDDED WITHIN A MUCH LARGER UPPER TROUGH OVER
THE EASTERN UNITED STATES...AND IS INSTIGATING COASTAL
CYCLOGENESIS WITH A 1016 MB LOW OFF THE CAROLINA COAST. A
DEVELOPING COLD FRONT EXTENDS S OF THE LOW TO 32N72W TO 26.5N77W
NEAR GREAT ABACO ISLAND IN THE BAHAMAS. DRY AIR IS FLOWING OFF
THE CONTINENT BEHIND THE FRONT AND IS PRODUCING STRATOCU OVER
THE WARMER GULF STREAM WATERS N OF 29N. A DISSIPATING WARM FRONT
LIES JUST SE OF THE COLD FRONT ALONG 25N74W 30N66W 30N58W AND IS
PRODUCING WIDELY SCATTERED SHOWERS/TSTMS UP TO 200 NM NW OF THE
BOUNDARY. ULTIMATELY THE WARM FRONT IS EXPECTED TO DISSIPATE
WITH THE COLD FRONT BECOMING THE DOMINANT FEATURE OVER THE NEXT
24 HRS.

EAST/CENTRAL ATLANTIC...
A VIGOROUS UPPER LEVEL LOW IS LOCATED ABOUT 180 NM ENE OF
TRINIDAD NEAR 12N59W WITH AN INVERTED TROUGH EXTENDING N TO
20N60W...MOVING QUICKLY W TOWARDS THE WINDWARD ISLANDS AND
EXPECTED TO CROSS IN THE E CARIBBEAN SAT MORNING. THE LOW IS
PRODUCING DRY WEATHER ACROSS THE LESSER ANTILLES BUT TSTMS ARE
LOOMING TO THE E WITH SCATTERED MODERATE CONVECTION FROM 8N-12N
BETWEEN 53W-60W ON THE DIFFLUENT S/E SIDE. A LARGE UPPER HIGH IS
OVER THE CNTRL ATLC NEAR 26N43W AND IS PUSHING THE SUBTROPICAL
JET WELL N OF THE AREA...ALLOWING A SURFACE RIDGE TO BUILD ALONG
27N. A NEARLY STATIONARY UPPER TROUGH LIES E OF THE HIGH FROM
MOROCCO SW TO THE CAPE VERDE ISLANDS. THE FRONT THAT IS
ASSOCIATED WITH THIS TROUGH HAS BECOME STATIONARY AND IS NOW
DISSIPATING ALONG 32N10W 25N17W 21N25W...ROUGHLY ALONG THE N
EDGE OF A SAHARAN DUST PLUME. FARTHER S...AN ELONGATED UPPER LOW
IS CENTERED NEAR 10N34W AND IS INDUCING SLIGHT UPPER DIFFLUENCE
TO ITS E...MORE OR LESS ONLY ACTING TO INCREASE MID/UPPER LEVEL
CLOUDINESS WITH OCCASIONAL SHOWERS/TSTMS BETWEEN 20W-35W.

$$
BERG


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