000 AXNT20 KNHC 110543 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 105 AM EST TUE DEC 11 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 11N15W TO 07N19W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 07N19W TO 04N24W TO 04N36W. SCATTERED MODERATE CONVECTION IS FROM 06N-12N BETWEEN 38W-51W. ...DISCUSSION... GULF OF MEXICO... BROAD MIDDLE TO UPPER LEVEL TROUGHING IS OVER THE CONUS WHICH IS PROVIDING MUCH OF THE GULF WITH SOUTHWESTERLY FLOW ALOFT. THE TROUGHING SUPPORTS A COLD FRONT ANALYZED INTO THE GULF REGION ACROSS THE FLORIDA PANHANDLE ALONG 30N87W TO 27N90W TO THE MEXICO COAST NEAR 20N97W. ISOLATED SHOWERS ARE OCCURRING WITHIN 30 NM EITHER SIDE OF THE FRONT E OF 90W...AND ACROSS MUCH OF THE WESTERN GULF W OF 90W. ANOTHER IMPACT WITH THE FRONT IS GALE FORCE NORTHERLY WINDS FOLLOW IN WAKE OF THE FRONT S OF 26N. WINDS ARE FORECAST TO DIMINISH BELOW GALE FORCE THROUGH THE OVERNIGHT HOURS...BUT REMAIN IN THE RANGE OF 20 TO 30 KT. OTHERWISE...THE REMAINDER OF THE GULF IS UNDER THE INFLUENCE OF WEAK PRE-FRONTAL TROUGHING WITH ISOLATED SHOWERS AND TSTMS OCCURRING FROM 23N-28N E OF 87W...INCLUDING PORTIONS OF THE CENTRAL AND SOUTHWESTERN FLORIDA PENINSULA. THE COLD FRONT IS EXPECTED TO CONTINUE MOVING EASTWARD INTO THE SW NORTH ATLC AND NW CARIBBEAN BY THURSDAY AS HIGH PRESSURE BUILDS IN ACROSS THE GULF WITH PERSISTENT N-NE WINDS. CARIBBEAN SEA... MUCH OF THE BASIN THIS EVENING IS UNDER TRANQUIL CONDITIONS AS WATER VAPOR IMAGERY INDICATES AN UPPER LEVEL RIDGE WITH AXIS ALONG 73W IS PROVIDING A RELATIVELY DRY AND STABLE ATMOSPHERE. A FEW ISOLATED SHOWERS AND TSTMS ARE HOWEVER OCCURRING OVER PORTIONS OF THE SW CARIBBEAN S OF 11N DUE TO CLOSE PROXIMITY OF THE MONSOON TROUGH AXIS WHICH EXTENDS FROM THE EASTERN PACIFIC REGION ALONG 09N TO NORTHERN COLOMBIA NEAR 09N77W. OTHERWISE...A FEW PASSING LOW-TOPPED ISOLATED SHOWERS ARE NOTED ON SATELLITE IMAGERY ACROSS WESTERN HISPANIOLA...THE ADJACENT COASTAL WATERS SURROUNDING PUERTO RICO...AND THE SE CARIBBEAN S OF 15N E OF 66W. WHILE CONDITIONS ARE CONVECTIVELY QUIET...THE EXISTING PRESSURE GRADIENT BETWEEN A STRONG CENTRAL ATLC RIDGE AND LOWER PRESSURE ACROSS NORTHERN SOUTH AMERICA IS PROVIDING FOR ENHANCED EASTERLY TRADE WIND FLOW IN THE RANGE OF 20 TO 30 KT. THESE TRADES ARE EXPECTED TO PERSIST THROUGH LATE THURSDAY. ATLANTIC OCEAN... A MIDDLE TO UPPER LEVEL RIDGE IS OVER THE SW NORTH ATLC WITH AXIS EXTENDING NORTHWARD ALONG 74W FROM THE WESTERN CARIBBEAN SEA. WATER VAPOR IMAGERY INDICATES FAIR DRY AIR REMAINS S OF 27N...HOWEVER WITH THE APPROACH OF A FRONTAL TROUGH CURRENTLY OVER THE SE CONUS AND EASTERN GULF OF MEXICO...SCATTERED SHOWERS AND TSTMS ARE OCCURRING ACROSS PORTIONS OF THE FLORIDA PENINSULA...AND SW NORTH ATLC WATERS N OF 28N BETWEEN 74W-80W. OTHERWISE...THE REMAINDER OF THE SW NORTH ATLC AND CENTRAL ATLC ARE UNDER THE INFLUENCE OF A 1027 MB HIGH CENTERED NEAR 31N50W. A SURFACE RIDGE AXIS EXTENDS W-SW FROM THE HIGH TO THE BAHAMAS AND CUBA. FARTHER EAST...AN UPPER LEVEL TROUGH IS NOTED ON WATER VAPOR IMAGERY IN THE VICINITY OF 28N48W THAT CONTINUES TO SUPPORT A STATIONARY FRONT ANALYZED FROM 32N25W TO 23N31W THAT BECOMES A SHEAR LINE SW TO 10N60W. ISOLATED SHOWERS AND TSTMS ARE OCCURRING WITHIN 90 NM EITHER SIDE OF THE STATIONARY FRONT. AS FOR THE SHEAR LINE...RECENT SCATTEROMETER PASSES INDICATE THE PRESENCE OF THE AXIS WITH STRONGER WINDS TO THE NORTH AND WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS OCCURRING WITHIN 240 NM EITHER SIDE OF THE SHEAR LINE AXIS. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN