000 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