000 AXNT20 KNHC 191754 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 105 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH EXTENDS 100 NM OFF THE NORTHWESTERN COAST OF LIBERIA. THE ITCZ CONTINUES FROM 5N12W SOUTHWESTWARD TOWARDS THE EQUATOR AND 22W THEN TO 1N35W TO THE COAST OF NORTHERN BRAZIL CLOSE TO THE EQUATOR AND 49W. SCATTERED PRECIPITATION IS OBSERVED FROM THE EQUATOR TO 6N BETWEEN 12W AND 22W. SIMILAR TYPE OF CONVECTION IS OBSERVED WITHIN 250 NM N OF THE ITCZ BETWEEN 25W AND 32W. ...DISCUSSION... THE GULF OF MEXICO... AT THE MIDDLE TO UPPER LEVELS...THE SOUTHERN PORTION OF A RIDGE POSITIONED OVER THE CENTRAL AND EASTERN U.S.A IS PROVIDING WESTERLY AND NORTHWESTERLY WIND FLOW. AT THE SURFACE SOUTHEASTERLY WINDS OR RETURN FLOW OF 10 KT TO 20 KT ASSOCIATED TO A 1021 MB HIGH PRESSURE OVER NORTHEASTERN FLORIDA DOMINATE THE REGION. AN EXTENSION OF A DYING COLD FRONT IS ACROSS THE FLORIDA KEYS AND EXTENDS TO THE EASTERN GULF NEAR 25N82W. ACCORDING TO THE WATER VAPOR IMAGERY THERE IS MODERATE TO STRONG SUBSIDENCE OVER THE GULF SUPPORTING NO CONVECTIVE ACTIVITY AT THIS TIME. WITHIN THE NEXT 24 HOURS...THE RETURN FLOW IS EXPECTED TO CONTINUE OVER THE REGION WHILE A NEW COLD FRONT STARTS ENTERING THE NORTHWESTERN GULF. THE CARIBBEAN SEA... AT THE MIDDLE TO UPPER LEVELS...THE NORTHWESTERN CARIBBEAN HAS WESTERLY TO SOUTHWESTERLY WINDS UP TO 45 KT ASSOCIATED TO THE UPPER RIDGE AXIS THAT EXTENDS OVER THE GULF REGION. THE CENTRAL AND EASTERN CARIBBEAN IS DOMINATED BY UPPER LEVEL SOUTHEASTERLY WIND ASSOCIATED TO RETURN FLOW FROM AN ANTICYCLONE LOCATED IN THE TROPICAL CENTRAL ATLC. AT THE SURFACE...WEAK PRESSURE GRADIENT DOMINATES THE REGION. TRADE WINDS OF 10 KT TO 20 KT ARE E OF 75W IN THE CENTRAL AND EASTERN CARIBBEAN. IN THE WESTERN CARIBBEAN RETURN FLOW OF THE SAME MAGNITUDE COVERS THE REGION. WATER VAPOR IMAGERY SHOWS MODERATE TO STRONG SUBSIDENCE OVER THE ENTIRE CARIBBEAN WHICH IS ALLOWING FAIR WEATHER CONDITIONS. WITHIN 24 HOURS...MOSTLY RETURN FLOW WILL COVER THE REGION AS THE HIGH PRESSURE LOCATED OVER NORTHER FLORIDA DISPLACES TO THE SOUTHWEST IN THE WESTERN ATLC. AN INCREASE OF WIND MAGNITUDE UP TO 25 KT IS POSSIBLE IN THE CENTRAL AND SOUTHERN CARIBBEAN. THE ATLANTIC OCEAN... IN THE MIDDLE TO UPPER LEVELS...A TROUGH ASSOCIATED TO AN UPPER LOW CENTERED NEAR 41N67W COVERS THE WESTERN ATLC FOLLOWED BY AN UPPER RIDGE IN THE CENTRAL ATLANTIC WITH AXIS EXTENDING TO THE GREATER AND LESSER ANTILLES. THE UPPER LEVEL TROUGH IS SUPPORTING A COLD FRONT THAT ENTERS THE REGION NEAR 30N63W AND EXTENDS SOUTHWEST TO 27N71W THEN TO THE S OF THE FLORIDA PENINSULA NEAR 25N80W. NO CONVECTIVE ACTIVITY IS OBSERVED ASSOCIATED TO THIS SURFACE FEATURE. IN THE CENTRAL ATLC...A NARROW UPPER LEVEL TROUGH SUPPORTS A SURFACE TROUGH THAT EXTENDS FROM 28N38W SOUTHWESTWARD TO 24N44W 19N49W. THIS UPPER LEVEL NARROW TROUGH ALSO SUPPORTS A STATIONARY FRONT NE OF THE SURFACE TROUGH THAT ENTERS THE REGION NEAR 29N27W AND CONTINUES SOUTHWESTWARD TO 26N34W. IN THE EASTERN ATLC...E OF THE STATIONARY FRONT A 1021 MB HIGH NEAR 29N20W STEADILY DISPLACES NORTHEAST OUT OF THE REGION IN 24 HOURS. SOME SHOWER ACTIVITY CAN BE FOUND AHEAD OF THE STATIONARY FRONT WHERE THE BOUNDARY BETWEEN THE MIDDLE TO UPPER LEVEL NARROW TROUGH AND A RIDGE THAT STARTS TO BUILD E OF 35W IS FOUND. THIS AREA OF PRECIPITATION LIES N 16N BETWEEN 20W AND 36W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ NR/CW