000 AXNT20 KNHC 112345 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EDT FRI NOV 11 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 2315 UTC. ...SPECIAL FEATURES... TROPICAL STORM SEAN IS CENTERED NEAR 35.5N 61.3W AT 11/2100 UTC OR ABOUT 260 NM NE OF BERMUDA MOVING NE AT 26 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 991 MB. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. PLEASE SEE LATEST FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. SEAN IS QUICKLY LOSING TROPICAL CHARACTERISTICS WITH THE CONVECTION REMOVED TO THE NE OF THE LOW CENTER. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM OF LINE FROM 34N58W TO 37N61W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE E TROPICAL ATLC NEAR 12N16W TO 8N20W. THE ITCZ AXIS EXTENDS FROM 8N20W ALONG 6N25W 7N31W TO 6N50W. CLUSTERS OF SCATTERED MODERATE/ STRONG CONVECTION ARE FROM 3N-10N BETWEEN 17W-40W. ...DISCUSSION... GULF OF MEXICO... A BROAD UPPER TROUGH COVERS THE E CONUS INTO THE W ATLC AND S OVER THE GULF WITH THE AXIS EXTENDING FROM NEAR MOBILE ALABAMA TO VERACRUZ MEXICO SUPPORTING A STRONG COLD FRONT THAT HAS JUST EXITED THE GULF. A SURFACE RIDGE HAS BUILT IN BEHIND THE FRONT ANCHORED BY A 1027 MB HIGH ALONG THE COAST OF LOUISIANA NEAR 30N92W. THE STRONG NORTHERLY SURFACE WINDS ARE BANKING LOW CLOUDS WITH POSSIBLE ISOLATED SHOWERS ALONG THE E SLOPES OF THE SIERRA MADRE MOUNTAINS OF MEXICO AND WITHIN 90/120 NM ALONG THE COAST S OF TAMPICO AND W OF CIUDAD DEL CARMEN. COLD AIR STRATOCUMULUS CLOUDS COVER MOST OF THE GULF WITH THE EXCEPTION OF THE NE GULF WHERE CLEAR SKIES PREVAIL. SURFACE RIDGE WILL MOVE E ALONG THE N GULF COAST ALLOWING FOR SOUTHERLY RETURN FLOW TO BECOME ESTABLISHED OVER THE W GULF THROUGH TUE AHEAD OF THE NEXT COLD FRONT FORECAST TO ENTER THE GULF TUE EVENING. CARIBBEAN SEA... THE UPPER TROUGH OVER THE GULF OF MEXICO IS APPROACHING THE NW CARIBBEAN. HOWEVER...THE ASSOCIATED FRONT HAS ALREADY ENTERED THE AREA EXTENDING FROM THE W ATLC ACROSS W CUBA AND THE ISLE OF YOUTH TO THE YUCATAN PENINSULA NEAR 20N87W TO INLAND OVER S MEXICO. WATER VAPOR IMAGERY INDICATES DRY STABLE AIR AND STRONG SUBSIDENCE OVER THE NW CARIBBEAN...THUS NO SHOWER ACTIVITY IS ASSOCIATED WITH THE FRONT. A BROAD UPPER RIDGE COVERS THE CARIBBEAN W OF 70W ANCHORED IN THE CENTRAL CARIBBEAN NEAR 15N75W PROVIDING DIFFLUENCE ALOFT TO GENERATE CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 75/90 NM OF LINE FROM 17N72W TO 14N76W EXPANDING TO WITHIN 120 NM TO NEAR 11N81W. THE BROAD UPPER TROUGH OVER THE CENTRAL ATLC EXTENDS S OVER THE REMAINDER OF THE CARIBBEAN E OF 70W WITH A SURFACE TROUGH EXTENDING FROM THE DOMINICAN REPUBLIC NEAR 19N69W TO INLAND OVER SOUTH AMERICA NEAR 12N72W AND SCATTERED SHOWERS/THUNDERSTORMS INLAND AND WITHIN 45 NM ALONG THE COAST OF COLOMBIA BETWEEN 72W-75W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE INLAND AND WITHIN 60 NM ALONG THE COAST OF PUERTO RICO. THIS IS LEAVING THE REMAINDER OF THE CARIBBEAN WITH FAIR CONDITIONS THIS EVENING. COLD FRONT WILL REACH FROM E CUBA TO NE NICARAGUA LATE TONIGHT THEN DISSIPATE SAT. ATLANTIC OCEAN... BROAD UPPER TROUGH COVERS THE E CONUS INTO THE W ATLC W OF 75W SUPPORTING A STRONG COLD FRONT THAT EXTENDS INTO THE W ATLC THROUGH 32N68W ACROSS THE N BAHAMA ISLANDS NEAR 25N77W TO OVER CUBA INTO THE NW CARIBBEAN NEAR 23N80W. WATER VAPOR IMAGERY INDICATES DRY STABLE AIR AND STRONG SUBSIDENCE W AND E OF THE FRONT LIMITING SHOWER ACTIVITY WITH A NARROW SWATH OF MOISTURE ALONG THE FRONT. A BROAD UPPER RIDGE AXIS EXTENDS FROM THE CARIBBEAN ACROSS HAITI NEAR 20N71W TO BEYOND 32N62W WITH DRY STABLE AIR W OF 60W. A NARROW UPPER TROUGH IS IN THE CENTRAL ATLC WITH THE AXIS EXTENDING THROUGH 32N55W ALONG 24N58W INTO THE E CARIBBEAN OVER THE LEEWARD ISLANDS NEAR 17N62W WITH POSSIBLE ISOLATED SHOWERS WITHIN 200/250 NM OF THE TROUGH AXIS. A SURFACE RIDGE IS BUILDING S OVER THE CENTRAL ATLC N OF 25N BETWEEN 30W-55W. AN UPPER TROUGH COVERS THE E ATLC N OF 24N E OF 40W WITH A SURFACE TROUGH EXTENDING THROUGH 32N22W TO 24N28W. AN AMPLIFIED UPPER RIDGE REMAINS IN THE TROPICS S OF 25N E OF 35W TO THE COAST OF W AFRICA DRAWING TROPICAL MOISTURE N FROM THE ITCZ WITH ISOLATED SHOWERS FROM 10N-26N BETWEEN 20W-35W. W ATLC COLD FRONT WILL REACH FROM THE CENTRAL ATLC TO N HISPANIOLA SAT NIGHT DISSIPATING OVER THE CENTRAL ATLC MON. SURFACE RIDGE WILL BUILD BEHIND FRONT THROUGH TUE. A SECOND COLD FRONT WILL ENTER NW ATLC EARLY WED. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ PAW