[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 092348
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST WED NOV 09 2011

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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2335 UTC.

...SPECIAL FEATURES...

TROPICAL STORM SEAN IS CENTERED NEAR 29.1N 70.5W AT 10/0000 UTC
OR 405 MI...650 KM WSW OF BERMUDA MOVING N AT 5 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 991 MB. MAXIMUM SUSTAINED WIND SPEED
IS 55 KT WITH GUSTS TO 65 KT. SCATTERED MODERATE CONVECTION IS
FROM 26N-32N BETWEEN 67W-74W. SEE LATEST NHC INTERMEDIATE PUBLIC
ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT4/WTNT34 KNHC AND THE
FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24
KNHC FOR MORE DETAILS. WITH THE DEVELOPMENT OF THE CENTRAL CORE
AND ABOUT A DAY OF LIGHT SHEAR CONDITIONS REMAINING...FURTHER
INTENSIFICATION SEEMS PROBABLE. GIVEN THE DEVELOPING EYE
FEATURE...THE NEW NHC FORECAST SHOWS SEAN REACHING HURRICANE
STRENGTH IN 24 HOURS. A GRADUAL TURN TOWARD THE NORTHEAST WITH
SOME ACCELERATION IS EXPECTED TOMORROW AS THE TROPICAL CYCLONE
FEELS THE INFLUENCE OF A TROUGH MOVING INTO THE EASTERN UNITED
STATES.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH REMAINS INLAND ACROSS WEST AFRICA. THE ITCZ
EXTENDS WESTWARD FROM THE NORTHERN COAST OF GUINEA ALONG 11N15W
8N20W 6N30W 7N40W 5N52W. SCATTERED MODERATE TO ISOLATED STRONG
CONVECTION IS FROM 4N-11N W OF 18W.

...DISCUSSION...

GULF OF MEXICO...
THE MAIN FEATURE AFFECTING THE GULF THIS EVENING IS A COLD FRONT
EXTENDING SW ALONG THE COAST OF ALABAMA NEAR 30N80W TO 25N93W TO
S OF TAMPICO MEXICO ALONG 20N97W. A SHORTWAVE UPPER LEVEL TROUGH
MOVING ACROSS THE GREAT LAKES REGION SUPPORTS THE COLD FRONT.
CURRENTLY...THE FRONT LACKS OF ANY SIGNIFICANT DEEP CONVECTION
...ALLOWING ONLY FOR WIDELY SCATTERED SHOWERS WITHIN 80-120 NM
ON EITHER SIDE OF THE FRONT. GUSTY NORTHERLY WINDS UP TO 25 KT
ARE BEHIND THE FRONT. A SURFACE TROUGH IS ANALYZED S OF THE COLD
FRONT IN THE BAY OF CAMPECHE FROM 23N93W TO 19N94W WITH NO
CONVECTION. ELSEWHERE...THE EASTERN GULF WATERS ARE UNDER THE
INFLUENCE OF A WEAKENING SURFACE RIDGE. THE RIDGE IS EXPECTED TO
DISSIPATE AS THE FRONT MOVES EASTWARD INTO THE SW NORTH ATLC
THROUGH EARLY FRIDAY. BEHIND THE FRONT A RIDGE IS FORECAST TO
INFLUENCE THE GULF OVER THE WEEKEND WITH STRONG N-NE WINDS
GRADUALLY DIMINISHING BY SATURDAY.

CARIBBEAN SEA...
DRY AIR ALOFT AND STRONG SUBSIDENCE COVERS A GREAT PART OF THE
CARIBBEAN SEA THIS EVENING...SUPPRESSING DEEP CONVECTION ACROSS
MOST OF THE BASIN. HOWEVER...STRONG DIFFLUENCE IS NOTICED OVER
THE NE BASIN SUPPORTING A SURFACE TROUGH ANALYZED FROM 18N67W TO
12N70W WITH SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS N OF
14N E OF 68W. LAST VISIBLE PICTURES OF THE DAY SHOWED POSSIBLE
ISOLATED SHOWERS OCCURRING ACROSS THE CENTRAL BASIN...WITHIN 60
NM EITHER SIDE OF A LINE FROM 12N78W TO 18N69W. SCATTERED HEAVY
SHOWERS AND THUNDERSTORMS ARE ALSO IN THE SW CARIBBEAN S OF 12N
W OF 75W...ASSOCIATED TO THE MONSOON TROUGH EXTENDING ACROSS
COSTA RICA TO A NEAR STATIONARY 1008 MB LOW NEAR 11N78W INTO NRN
COLOMBIA. SHORT RANGE MODEL DATA SUGGEST THIS AREA OF CONVECTION
WILL LINGER OVER THE NEXT 24 HOURS.

ATLANTIC OCEAN...
TROPICAL STORM SEAN CONTINUES TO IMPACT THE WRN ATLC WITH
SCATTERED STRONG CONVECTION AROUND THE CENTER AND SEAS TO 20 FT
WITH LONG AND PERSISTENT N TO NE FETCH NORTHWEST OF THE CENTER.
SWELLS GENERATED BY SEAN ARE EXPECTED TO AFFECT PORTIONS OF THE
SOUTHEASTERN U.S. COAST AND BERMUDA DURING THE NEXT COUPLE OF
DAYS...CAUSING LIFE-THREATENING SURF AND RIP CURRENTS. FOR MORE
INFORMATION SEE SPECIAL FEATURE ABOVE. AN UPPER LEVEL LOW IS
NEARLY COLLOCATED OVER SEAN WITH A TROUGH AXIS EXTENDING SE
PROVIDING MIDDLE TO UPPER LEVEL DIFFLUENCE GENERATING SCATTERED
SHOWERS AND TSTMS N OF 17N BETWEEN 57W-63W. A BROAD UPPER LEVEL
TROUGH IS IN THE NE ATLC SUPPORTING A COLD FRONT THAT ENTERS THE
DISCUSSION AREA NEAR 32N15W TO 27N23W WHERE THE FRONT BECOMES
STATIONARY ALONG 27N30W 26N40W TO 27N51W. A WEAK 1012 MB LOW IS
LOCATED NEAR THE TAIL END OF THE FRONT NEAR 28N48W WITH A
SURFACE TROUGH EXTENDING SW FROM THE LOW ALONG 24N50W TO 22N55W.
LOW-LEVEL MOISTURE CONTINUES TO CONVERGE AND LIFT ALONG AND
NORTH OF THE FRONTAL BOUNDARY WITH SCATTERED SHOWERS AND
ISOLATED TSTMS WITHIN 100 NM SOUTH...AND 180 NM NORTH OF THE
STATIONARY FRONT.

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

$$

GARCIA



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