000 AXNT20 KNHC 132354 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST THU DEC 13 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 ACROSS MOST OF AFRICA. THE ITCZ EXTENDS FROM OVER LIBERIA INTO THE E TROPICAL ATLC NEAR 6N10W ALONG 4N18W 3N30W TO 3N41W. CLUSTERS OF SCATTERED MODERATE/ ISOLATED STRONG CONVECTION ARE FROM 4N-8N BETWEEN 12W-16W... FROM 1N-5N BETWEEN 15W-39W...AND FROM 5N-9N BETWEEN 37W-45W. ...DISCUSSION... GULF OF MEXICO... A BROAD LOW AMPLITUDE UPPER TROUGH COVERS THE GULF N OF 26N AND INTO THE W ATLC SUPPORTING A COLD FRONT THAT AT 13/2100 UTC EXTENDS THROUGH THE STRAITS OF FLORIDA NEAR 25N80W JUST S OF THE FLORIDA KEYS TO 23N84W WHERE IT DISSIPATES ALONG THE N COAST OF THE YUCATAN TO 21N93W AND CONTINUES DISSIPATING AS A STATIONARY FRONT ALONG 21N95W TO THE COAST OF MEXICO NEAR THE ISTHMUS OF TEHUANTEPEC. SCATTERED SHOWERS ARE WITHIN 30 NM ALONG THE FRONT E OF 82W. STRONG SUBSIDENCE WITH DRY STABLE AIR AND MOSTLY CLEAR SKIES ARE N OF A LINE FROM TAMPA FLORIDA TO CORPUS CHRISTI TEXAS WITH THE EXCEPTION OF OVERCAST LOW CLOUDS N OF 27N W OF 85W TO OVER NE FLORIDA. A BROAD UPPER RIDGE ANCHORED IN THE E PACIFIC REGION COVERS THE REMAINDER OF THE GULF. A SURFACE RIDGE IS BUILDING S OVER THE GULF BEHIND THE FRONT ANCHORED BY A 1030 MB HIGH OVER TENNESSEE. COLD FRONT WILL BECOME STATIONARY TONIGHT THEN DISSIPATE ACROSS THE STRAITS OF FLORIDA FRI. SOUTHERLY RETURN FLOW WILL INCREASE ACROSS THE W GULF FRI NIGHT THROUGH LATE SUN AHEAD OF THE NEXT COLD FRONT THAT WILL MOVE ACROSS THE GULF MON AND TUE. CARIBBEAN SEA... BROAD UPPER RIDGE COVERS THE W CARIBBEAN W OF 70W ANCHORED IN THE E PACIFIC REGION. A LARGE UPPER TROUGH EXTENDS FROM AN UPPER LOW IN THE W TROPICAL ATLC OVER THE REMAINDER OF THE CARIBBEAN. NE TRADE WINDS ARE USHERING IN SOME ISOLATED LOW LEVEL SHOWERS MAINLY N OF 15N E OF 69W AND S OF 16N BETWEEN 74W-83W. OTHERWISE THE CARIBBEAN REMAINS TRANQUIL THIS EVENING. THE COLD FRONT IN GULF OF MEXICO WILL REACH THE NW CARIBBEAN FRI. FRESH TRADE WINDS ACROSS E/CENTRAL CARIBBEAN WILL DIMINISH THROUGH FRI AS A SURFACE RIDGE OVER THE ATLC WATERS SHIFTS E AHEAD OF THE NEXT COLD FRONT THAT WILL MOVE INTO THE W ATLC TUE. ATLANTIC OCEAN... A BROAD LOW AMPLITUDE UPPER TROUGH COVERS THE W ATLC N OF 26N W OF 70W SUPPORTING A COLD FRONT THAT AT 13/2100 UTC EXTENDS THROUGH 32N70W ACROSS THE N BAHAMA ISLANDS TO THE STRAITS OF FLORIDA INTO THE GULF OF MEXICO NEAR 25N80W. SCATTERED SHOWERS ARE WITHIN 30/45 NM SE OF THE FRONT. AN UPPER LOW IS IN W TROPICAL ATLC NEAR 19N50W WITH AN UPPER TROUGH COVERING THE AREA FROM 10N-25N BETWEEN 45W-70W. SCATTERED SHOWERS/THUNDERSTORMS ARE ASSOCIATED WITH THE UPPER LOW COVERING THE AREA FROM 18N-22N BETWEEN 48W-51W. A SURFACE TROUGH IS SE OF THE UPPER LOW EXTENDING FROM 19N45W TO 10N49W. A UPPER RIDGE TO THE E IS PROVIDING DIFFLUENCE ALOFT TO GENERATE SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS WITHIN 200 NM E OF THE SURFACE TROUGH. A LARGE SURFACE RIDGE DOMINATES THE ATLC N OF 20N BETWEEN AFRICA AND 60W ANCHORED BY A 1023 MB HIGH NEAR 30N33W. W ATLC COLD FRONT WILL REACH FROM 32N64W TO THE STRAITS OF FLORIDA FRI THEN DISSIPATE FRI NIGHT AND SAT. THE NEXT COLD FRONT WILL MOVE INTO THE W ATLC TUE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ PAW