[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 291801
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON OCT 29 2012

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN 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 FEATURES...

THE CENTER OF HURRICANE SANDY AT 29/1800 UTC IS NEAR 38.3N
73.1W. SANDY IS ABOUT 95 NM TO THE SOUTHEAST OF ATLANTIC CITY
NEW JERSEY...AND ABOUT 150 NM TO THE SOUTH-SOUTHEAST OF NEW YORK
CITY. SANDY IS MOVING NORTHWEST 24 KT. THE ESTIMATED
MINIMUM CENTRAL PRESSURE IS 94 MB. THE MAXIMUM SUSTAINED WIND
SPEEDS ARE 80 KNOTS WITH GUSTS TO 100 KNOTS. PLEASE READ THE
FORECAST/ADVISORY UNDER THE AWIPS/WMO HEADERS MIATCMAT3/WTNT23
KNHC...AND THE PUBLIC ADVISORY UNDER MIATCPAT3/WTNT33 KNHC FOR
MORE DETAILS. MODERATE CONVECTION PERSISTS WITHIN 60 NM OF THE
CENTER.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH PASSES THROUGH THE COASTAL GUINEA-BISSAU NEAR
12N16W TO 08N18W TO 06N28W. THE ITCZ CONTINUES FROM 06N28W TO
08N41W...THEN FROM 0845W TO 07N58W. SCATTERED MODERATE
CONVECTION IS NOTED FROM 07N TO 09N BETWEEN 20N AND 25N.
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS NOTED 07N TO
10N BETWEEN 40W AND 43W.

...DISCUSSION...

THE GULF OF MEXICO...
A SHORT WAVE MID TO UPPER LEVEL TROUGH OVER THE LOWER
MISSISSIPPI VALLEY IS ROUNDING THE BASE OF A BROAD LOW CENTERED
OVER THE TENNESSEE VALLEY...LEAVING GENERALLY ZONAL FLOW ALOFT
IN PLACE ACROSS THE GULF INTO TUE. RESIDUAL STRATOCUMULUS CLOUDS
ARE SLOWLY DISSIPATING ACROSS THE EASTERN GULF...BEHIND A COLD
FRONT THAT PASSED THROUGH THE GULF YESTERDAY DRIVEN BY THE BROAD
NORTHERLY FLOW AROUND HURRICANE SANDY IN THE WESTERN ATLC. FRESH
TO STRONG NW TO N WINDS PERSIST OVER THE FAR EASTERN GULF...BUT
HAVE STARTED TO DIMINISH OVER MOST OF THE CENTRAL AND WESTERN
GULF WATERS. AREAS OF SHOWERS WITH A FEW THUNDERSTORMS ARE
ACTIVE IN THE BAY OF CAMPECHE ALONG A REMNANT BOUNDARY OF THE
OLD FRONT...SUPPORTED IN PART BY CONVERGENT NORTHERLY FLOW AND
MID TO UPPER LEVEL MOISTURE ORIGINATING FROM THE EASTERN
PACIFIC. HIGH PRES WILL BUILD OVER THE NW GULF...THEN INTO THE
CENTRAL GULF BY TUE...ALLOWING WINDS AND SEAS TO DIMINISH FROM W
TO E.

THE CARIBBEAN SEA...
THE MAIN DRIVER OF WEATHER IN THE CARIBBEAN FOR THE PAST COUPLE
OF DAYS HAS BEEN A BROAD UPPER TROUGH THAT WAS DIGGING THROUGH
THE GULF OF MEXICO...THEN WRAPPING AROUND HURRICANE SANDY IN THE
NW ATLC. AN ASSOCIATED COLD FRONT PENETRATED INTO THE FAR NW
CARIBBEAN YESTERDAY...AND IS STARTING TO STALL AND DISSIPATE
FROM CENTRAL CUBA TO THE GULF OF HONDURAS. THIS FEATURE SHOWS UP
WELL ON VISIBLE SATELLITE IMAGERY...AND IS FOLLOWED BY MODERATE
TO FRESH NW FLOW. A PORTION OF THE UPPER TROUGH BECAME CUT OFF
OVER THE SW CARIBBEAN OVER THE PAST COUPLE OF DAYS. CLUSTERS OF
SHOWERS AND TSTMS PERSIST OVER THE S CENTRAL CARIBBEAN THIS
AFTERNOON...DRIVEN IN PART BY UPPER LEVEL DIVERGENCE BETWEEN THE
UPPER LOW PRES AND AN UPPER ANTICYCLONE CENTERED E OF THE
CARIBBEAN. BOUY OBSERVATIONS INDICATE THAT THE PREVAILING WINDS
ARE STARTING TO CHANGE FROM MOSTLY W TO NW IN THE WAKE OF
SANDY...TO A RETURN OF EASTERLY TRADES OVER THE EASTERN
CARIBBEAN. IN FACT BUOY 42059 NEAR 15N68W IS SHOWING LIGHT SE
FLOW...JUST E OF THE CONVECTION. THIS IS AN INDICATION THAT A
WEAK SURFACE TROUGH MAY BE FORMING OVER THE CENTRAL CARIBBEAN.
EXPECT WINDS OVER THE NW CARIBBEAN TO VEER MORE NE BETWEEN THE
TROUGH AND HIGH PRES BUILDING OVER THE GULF OF MEXICO.

THE ATLANTIC OCEAN...

W OF 60W...WARNINGS HAVE BEEN DROPPED OVER THE AREA N OF 28N AS
HURRICANE SANDY CONTINUES TO MOVE N. W WINDS WILL PERSIST NEAR
GALE FORCE HOWEVER THROUGH LATE TODAY ESPECIALLY OFF NE FLORIDA.
A COLD FRONT EXTENDING FROM 31N75W THROUGH THE CENTRAL BAHAMAS
IS DISSIPATING CURRENTLY. HIGH PRES WILL BUILD W TO E S OF
25N...WITH FRESH TO STRONG W FLOW N OF 25N THROUGH LATE IN THE
WEEK. SCATTERED LOW CLOUDS PERSIST IN THE COOL NW TO W FLOW.
BETWEEN 30W AND 60W...A DEEP LAYER ANTICYCLONE PERSISTS NEAR
17N55W. TO ITS EAST...A MID LATITUDE MID TO UPPER LEVEL TROUGH
IS MOVING E THROUGH 40W...BRIEFLY COMING IN PHASE WITH A DEEP
LAYER TROUGH IN THE TROPICS ALONG 45W. AT THE SURFACE...AN
ASSOCIATED COLD FRONT TROUGH EXTENDS FROM 31N33W TO
25N37W...WITH A TRAILING TROUGH FROM 20N45W...NEARLY IN PHASE
WITH A GENERALLY STATIONARY TROUGH S OF 15N ALONG 40W. E OF
40W...

A MIDDLE LEVEL TO UPPER LEVEL TROUGH EXTENDS FROM A 35N39W
CYCLONIC CIRCULATION CENTER TO 26N40W. NORTHWESTERLY-TO-WESTERLY
WIND FLOW COVERS THE ATLANTIC OCEAN TO THE NORTH OF 25N BETWEEN
AND 50W. THE TROUGH SUPPORTS A COLD FRONT THAT PASSES THROUGH
32N34W TO 25N39W. CONVECTIVE PRECIPITATION...SCATTERED MODERATE
TO STRONG TO THE NORTH OF 22N BETWEEN 25W AND 34W. BROKEN TO
OVERCAST MULTILAYERED CLOUDS ISOLATED MODERATE TO LOCALLY STRONG
CONVECTIVE PRECIPITATION ARE ELSEWHERE TO THE NORTH OF 17N
BETWEEN 20W AND 50W. A LINE OF MODERATE CONVECTION PRECEDES THE
FRONT...WITH MODERATE TO STRONG CONVECTION NEAR THE TROUGH S OF
15N ALONG 40W. W OF 30W CONVECTION HAS DIMINISHED FROM YESTERDAY
OFF THE COAST OF AFRICA S OF THE CANARAY ISLANDS...AS A VIGOROUS
SHORT WAVE DIGGING INTO THE REGION LIFTED TO THE NE AND
WEAKENED. AN ASCAT PASS FROM 11 UTC INDICATED SOME CYCLONIC
TURING PERSISTED...REGARDED TO BE ALONG THE MONSOON TROUGH.
GLOBAL MODELS TO INCLUDE THE GFS AND ECMWF INDICATE A WEAK
CIRCULATION MAY FORM OVER THE NEXT COUPLE OF DAYS ALTHOUGH
SUPPORTING CONVECTION MAY BE LIMITED.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
CHRISTENSEN





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