000 AXNT20 KNHC 120555 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 105 AM EST WED DEC 12 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 08N13W TO 07N17W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 07N17W TO 04N38W TO 07N50W TO 06N55W. SCATTERED MODERATE CONVECTION IS FROM 05N-10N BETWEEN 39W-49W. ...DISCUSSION... GULF OF MEXICO... MIDDLE TO UPPER LEVEL SOUTHWESTERLY FLOW DOMINATE OVER THE GULF THIS EVENING BETWEEN UPPER LEVEL TROUGHING LOCATED OVER THE CENTRAL CONUS AND AN UPPER LEVEL RIDGE CENTERED NEAR 25N69W OVER THE SW NORTH ATLC. WITH A MID-LEVEL SHORTWAVE TROUGH AXIS OVER OKLAHOMA AND TEXAS...THE TROUGHING SUPPORTS A COLD FRONT ANALYZED FROM NORTHERN FLORIDA NEAR 30N82W TO 26N88W WHICH THEN BECOMES STATIONARY TO 24N92W TO THE MEXICO COAST NEAR 19N96W. PLENTY OF MIDDLE TO UPPER LEVEL MOISTURE CONTINUES TO STREAM E-NE FROM THE PACIFIC REGION OVER CENTRAL MEXICO TO THE SE CONUS. SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING WITHIN 240 NM NORTHWEST OF THE FRONT. OTHERWISE...THE REMAINDER OF THE GULF IS UNDER THE INFLUENCE OF PRE-FRONTAL SURFACE TROUGHING WITH A SURFACE TROUGH AXIS ANALYZED FROM 25N84W TO THE YUCATAN PENINSULA 21N88W. SCATTERED SHOWERS AND TSTMS ARE OCCURRING EAST OF A LINE FROM 29N83W TO 22N89W. THE FRONTAL BOUNDARY IS EXPECTED TO INCREASE IN EASTWARD MOVEMENT AS ENERGY ASSOCIATED WITH THE MID-LEVEL SHORTWAVE TROUGH PROGRESSES EAST OVER THE NEXT 24 TO 36 HOURS WITH THE FRONT CLEARING THE GULF REGION BY THURSDAY. HIGH PRESSURE WILL THEN BUILD IN ACROSS THE GULF WITH PERSISTENT N-NE WINDS. CARIBBEAN SEA... MUCH OF THE BASIN IS UNDER FAIRLY TRANQUIL CONDITIONS AS WATER VAPOR IMAGERY INDICATES AN UPPER LEVEL RIDGE WITH AXIS EXTENDING FROM THE SW CARIBBEAN NEAR 13N80W TO BEYOND 23N70W IS PROVIDING A RELATIVELY DRY AND STABLE ATMOSPHERE E OF 85W. 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 08N77W. OTHERWISE...A FEW PASSING LOW- TOPPED ISOLATED SHOWERS ARE NOTED ON SATELLITE IMAGERY ACROSS THE NORTH-CENTRAL CARIBBEAN N OF 15N BETWEEN 65W-74W AND THE SE CARIBBEAN S OF 15N E OF 70W. 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 FROM THE SW CARIBBEAN SEA NORTHEASTWARD TO BEYOND 32N64W. WATER VAPOR IMAGERY INDICATES FAIRLY DRY AIR REMAINS EAST OF A LINE FROM 32N68W TO 22N80W...HOWEVER WITH THE PRESENCE OF A COLD FRONT FROM 32N79W TO 30N81W AND THE APPROACH OF A FRONTAL TROUGH CURRENTLY OVER THE FLORIDA PENINSULA AND EASTERN GULF OF MEXICO...SCATTERED SHOWERS AND TSTMS ARE OCCURRING ACROSS THE FLORIDA PENINSULA AND SW NORTH ATLC WATERS NW OF A LINE FROM 32N71W TO 24N80W. OTHERWISE...THE REMAINDER OF THE SW NORTH ATLC AND CENTRAL ATLC ARE UNDER THE INFLUENCE OF A BROAD RIDGE ANCHORED BY A 1029 MB HIGH AND 1030 MB HIGH CENTERED NEAR 32N53W AND 34N39W RESPECTIVELY. ON THE SOUTHERN PERIPHERY OF THE RIDGE...AN UPPER LEVEL TROUGH AXIS IS NOTED ON WATER VAPOR IMAGERY FROM 26N45W TO 16N61W THAT SUPPORTS A SURFACE TROUGH AXIS ANALYZED FROM 17N44W TO 08N51W. ASIDE FROM LOW-LEVEL MOISTURE CONVERGENCE...STRONG MIDDLE TO UPPER LEVEL DIFFLUENCE IS GENERATING SCATTERED SHOWERS AND TSTMS FROM 10N-18N BETWEEN 40W-52W...AND FROM 13N-22N BETWEEN 28W-40W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN