000 AXNT20 KNHC 181128 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 AM EST SUN DEC 18 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1045 UTC. ...ITCZ/MONSOON TROUGH... THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 07N12W TO 05N24W TO 07N50W TO 06N57W. SCATTERED MODERATE CONVECTION IS FROM 06N-10N BETWEEN 30W-39W. ...DISCUSSION... GULF OF MEXICO... UPPER LEVEL CONFLUENCE IS NOTED ACROSS THE GULF THIS MORNING AS AN UPPER LEVEL LONGWAVE TROUGH REMAINS TO THE NORTH OVER THE SE CONUS AND EASTERN SEABOARD AND AN UPPER LEVEL RIDGE REMAINS ANCHORED OVER THE WESTERN CARIBBEAN SEA. WITH THE UPPER LEVEL TROUGHING CONTINUING TO SLIDE E-SE INTO NORTHERN PORTIONS OF THE SW NORTH ATLC...A DISSIPATING COLD FRONT IS ANALYZED FROM THE FLORIDA PENINSULA NEAR 27N83W TO 26N92W AND BECOMES STATIONARY ALONG 25N95W TO 19N96W. LOW-LEVEL MOISTURE REMAINS LIMITED ALONG THE COLD FRONT...HOWEVER...ISOLATED SHOWERS ARE POSSIBLE S OF 27N W OF 94W. THE FRONT IS EXPECTED TO CONTINUE DISSIPATING AS SURFACE TROUGHING SETS UP OVER THE WESTERN GULF AND A 1031 MB SURFACE HIGH PRESSURE CURRENTLY ANCHORED OVER NW LOUISIANA BUILDS EASTWARD ACROSS THE SE CONUS THROUGH LATE SUNDAY. THE HIGH IS EXPECTED TO PROVIDE MOSTLY EAST TO NORTHEAST WINDS ACROSS MUCH OF THE GULF THROUGHOUT THE DAY ON SUNDAY. BY MONDAY...SOUTHERLY RETURN FLOW IS EXPECTED TO RE-ESTABLISH OVER PORTIONS OF THE WESTERN GULF AS AN AREA OF LOW PRESSURE DEVELOPS OVER NORTH TEXAS AND OKLAHOMA. THE NEXT COLD FRONT IS THEN FORECAST TO ENTER THE NW GULF WATERS EARLY TUESDAY. CARIBBEAN SEA... AN UPPER LEVEL ANTICYCLONIC CIRCULATION INFLUENCES MUCH OF THE WESTERN CARIBBEAN CENTERED NEAR 15N72W WITH AXIS EXTENDING NW TO NEAR 23N83W. ON THE WESTERN PERIPHERY OF THE RIDGE...SOUTHERLY DIFFLUENT FLOW ALOFT CONTINUES TO ENHANCE SCATTERED SHOWERS AND ISOLATED TSTMS S OF 19N BETWEEN 77W-84W...INCLUDING PORTIONS OF PANAMA...COSTA RICA...AND EASTERN NICARAGUA. MOST OF THIS CONVECTIVE ACTIVITY IS FOCUSED IN THE VICINITY AND NORTH OF THE MONSOON TROUGH AXIS EXTENDING FROM THE E PACIFIC ALONG 09N TO NORTHERN COLOMBIA. OTHERWISE THE REMAINDER OF THE WESTERN CARIBBEAN W OF 72W IS UNDER STRONG NE TRADES DUE TO AN INCREASED PRESSURE GRADIENT FROM A HIGH PRESSURE CENTER OVER THE SW NORTH ATLC. FARTHER EAST...A VERY DRY AND STABLE ATMOSPHERE IS NOTED UNDER NW FLOW ALOFT ON THE EASTERN PERIPHERY OF THE PREVIOUSLY MENTIONED UPPER LEVEL RIDGE. NE TRADES PREVAIL E OF 72W AS WELL...HOWEVER REMAIN GENERALLY FROM 10 TO 15 KT. TWO AREAS OF ISOLATED SHOWERS ARE ALSO NOTED ON SATELLITE IMAGERY...ONE N OF 16N E OF 71W...AND THE OTHER S OF 13N E OF 71W. WITH INCREASED POSSIBILITY OF PRECIPITATION CONTINUING ALONG THE NORTHERN SHORES OF THE GREATER ANTILLES...NAMELY HISPANIOLA...POTENTIAL LOCALIZED FLOODING REMAINS AN IMPACT FOR THE NEXT 24-36 HOURS. HIGH PRESSURE IS FORECAST TO REMAIN ANCHORED EAST OF THE BAHAMAS THROUGH LATE SUNDAY MAINTAINING THE AREA OF INCREASED E-NE TRADES. ATLANTIC OCEAN... AN UPPER LEVEL LONGWAVE TROUGH IS PROGRESSING OVER THE EASTERN CONUS AND SUPPORTS A COLD FRONT ANALYZED INTO THE DISCUSSION AREA NEAR 32N70W THAT EXTENDS SW TO THE CENTRAL FLORIDA PENINSULA NEAR 28N80W. POSSIBLE ISOLATED SHOWERS ARE OCCURRING WITHIN 90 NM EITHER SIDE OF THE FRONT. TO THE SE OF THE COLD FRONT...AN UPPER LEVEL RIDGE AXIS EXTENDS FROM THE WESTERN CARIBBEAN SEA ALONG 15N72W NE TO BEYOND 32N57W AND SUPPORTS A WEAKENING 1020 MB SURFACE HIGH CENTERED NEAR 26N67W. MOSTLY NE WINDS ARE NOTED WITHIN THE SOUTHEASTERN PERIPHERY OF THE HIGH AS A RECENT ASCAT PASS AROUND 18/0052 UTC DEPICTED WINDS IN THE RANGE OF 10 TO 15 KT. OVER THE CENTRAL ATLC...AN UPPER LEVEL LOW IS CENTERED NEAR 26N48W AND EXTENDS TROUGHING SOUTHWARD TO 09N BETWEEN 40W-62W. THE UPPER LEVEL LOW SUPPORTS A COLLOCATED SURFACE LOW WITH A SET OF FRONTAL BOUNDARIES ASSOCIATED WITH THE SYSTEM. A STATIONARY FRONT EXTENDS FROM EAST OF THE LOW CENTER ALONG 27N46W TO 20N47W TO 17N48W THEN AS SURFACE TROUGH TO 10N50W. SCATTERED SHOWERS AND TSTMS ARE OCCURRING WITHIN 240 NM EAST OF THE BOUNDARY N OF 16N. CLOSER TO THE LOW CENTER...A STATIONARY FRONT EXTENDS NORTHWARD FROM THE LOW CENTER TO BEYOND 32N50W AND A SURFACE TROUGH IS ANALYZED FROM THE LOW TO 25N49W TO 19N56W. SCATTERED SHOWERS ARE OCCURRING WITHIN 330 NM EAST OF THE STATIONARY FRONT. BOTH OF THESE CONVECTIVELY ACTIVE AREAS ARE ENHANCED EAST OF THE UPPER LEVEL TROUGH AXIS DUE TO STRONG UPPER LEVEL DIFFLUENCE. THE REMAINDER OF THE EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1033 MB HIGH CENTERED SE OF THE AZORES NEAR 37N26W. THE INFLUENCE OF THE RIDGE EXTENDS SOUTHWARD TO 16N REMAINING E OF 40W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN