000 AXNT20 KNHC 192344 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST WED DEC 19 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 06N10W TO 05N11W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 05N11W TO 01N26W TO 01N48W. ISOLATED MODERATE CONVECTION IS FROM THE EQUATOR TO 06N BETWEEN 15W-33W. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY INDICATES A VERY DRY AND SUBSIDENT AIRMASS IS IN CONTROL OVER THE GULF BASIN THIS EVENING...HOWEVER A WEAK MID-LEVEL SHORTWAVE TROUGH IS NOTED IN THE VICINITY OF 25N90W. AS A SURFACE RIDGE ANCHORED BY A 1020 MB HIGH CENTERED OVER NE FLORIDA NEAR 30N82W CONTINUES TO DOMINATE STABLE WEATHER CONDITIONS AT THE SURFACE...THIS AREA OF MID-LEVEL ENERGY IS GENERATING AN AREA OF SCATTERED TO BROKEN CLOUDINESS AND POSSIBLE ISOLATED SHOWERS FROM 24N-30N BETWEEN 89W-93W. THIS AREA IS LOCATED ON THE WESTERN PERIPHERY OF THE SURFACE RIDGE WHERE SOUTHERLY FLOW CONTINUES TO STREAM INTO A DEVELOPING AREA OF LOW PRESSURE OVER THE CENTRAL PLAINS THIS EVENING. WITH THE SURFACE HIGH EXPECTED TO SHIFT EASTWARD AND INTO THE SW NORTH ATLC OVERNIGHT....S-SE WINDS WILL VEER S-SW BY EARLY THURSDAY MORNING AS THE NEXT COLD FRONT EMERGES OFF THE TEXAS AND LOUISIANA COAST. THIS FRONT WILL PACK A PUNCH OF NORTHERLY WINDS EXPECTED TO SPREAD ACROSS THE ENTIRE BASIN BY EARLY FRIDAY. GALE FORCE CONDITIONS ARE FORECAST TO BEGIN WITHIN 24 HOURS ACROSS PORTIONS OF THE SOUTHWESTERN GULF WATERS. CARIBBEAN SEA... CONDITIONS ACROSS THE CARIBBEAN SEA BASIN REMAIN FAIRLY TRANQUIL THIS EVENING AS WATER VAPOR IMAGERY INDICATES VERY DRY AIR AND SUBSIDENCE PREVAILING ALOFT WITH MOSTLY NORTHWEST TO WESTERLY FLOW DOMINATING. THIS PATTERN IS EXPECTED TO KEEP THE CARIBBEAN STABLE OVER THE NEXT 24 TO 36 HOURS. AT THE SURFACE...A FAIRLY WEAK PRESSURE GRADIENT CONTINUES TO SLOWLY TIGHTEN AS HIGH PRESSURE SLIDES OFF THE SE CONUS AND INTO THE SW NORTH ATLC WATERS. TRADE WINDS REMAIN IN THE RANGE OF 10 TO 20 KT WITH SLIGHTLY STRONGER E-NE WINDS EXPECTED BETWEEN 70W-80W THROUGH THE OVERNIGHT HOURS INTO THURSDAY. ISOLATED LOW-TOPPED SHOWERS ARE OCCURRING OVER PORTIONS OF THE CENTRAL AND SW CARIBBEAN FROM 13N-17N BETWEEN 68W-82W...AND S OF 12N BETWEEN 76W-83W. THE TRADES ARE EXPECTED TO PERSIST THROUGH LATE FRIDAY AS A COLD FRONT WILL BEGIN TO IMPACT THE NW CARIBBEAN LATE FRIDAY INTO THE WEEKEND WITH STRONG NE WINDS. ATLANTIC OCEAN... AN UPPER LEVEL TROUGH COUPLED WITH A MID-LEVEL LOW IS CENTERED OFF THE NEW ENGLAND COAST NEAR 41N65W THAT SUPPORTS A COLD FRONT ANALYZED FROM 32N55W SW TO 26N65W TO THE CENTRAL BAHAMAS NEAR 25N76W. THE FRONT REMAINS FREE OF PRECIPITATION W OF 64W...HOWEVER ISOLATED SHOWERS ARE OCCURRING WITHIN 60 NM EITHER SIDE OF THE BOUNDARY E OF 64W. OTHERWISE...THE REMAINDER OF THE SW NORTH ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1020 MB HIGH CENTERED OVER NE FLORIDA NEAR 30N82W. FARTHER EAST...AN UPPER LEVEL TROUGH IS OVER THE EASTERN ATLC WITH AXIS EXTENDING FROM 30N26W TO A BASE NEAR 12N40W. THIS TROUGHING SUPPORTS A STATIONARY FRONT ANALYZED INTO THE DISCUSSION AREA NEAR 32N23W EXTENDING SW TO 26N35W. A WEAK SURFACE TROUGH TAILS OFF TO THE WEST FROM THE FRONT ALONG 27N39W TO 22N52W. THE STATIONARY FRONT CONTINUES TO BRIDGE BETWEEN A PAIR OF 1020 MB HIGHS...ONE CENTERED NEAR 33N27W AND THE OTHER CENTERED NEAR 29N23W. POSSIBLE ISOLATED SHOWERS ARE OCCURRING WITHIN 90 NM EITHER SIDE OF THE FRONT...AND WITHIN 45 NM NORTH OF THE SURFACE TROUGH AXIS. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN