000 AXNT20 KNHC 111142 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 AM EST SUN DEC 11 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 1100 UTC. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS AFRICA TO THE COAST OF GUINEA-BISSAU NEAR 11N15W CONTINUING SW TO 7N20W. THE ITCZ CONTINUES FROM 7N20W ALONG 3N28W 3N48W. ISOLATED MODERATE CONVECTION IS WITHIN NM N OF THE AXIS BETWEEN 20W-37W. ...DISCUSSION... GULF OF MEXICO... MAINLY NELY SURFACE FLOW COVERS THE GULF OF MEXICO THIS MORNING AROUND AN ELONGATED SURFACE RIDGE WITH AXIS EXTENDING FROM NEW ENGLAND TO TEXAS. DUE TO THE TIGHT PRESSURE GRADIENT ACROSS THE BASIN...WINDY CONDITIONS PERSIST UP TO 20 KTS...SLIGHTLY DECREASED FROM OVERNIGHT. RADAR IMAGERY INDICATES SCATTERED SHOWERS CONTINUE ACROSS THE NW GULF FROM THE COAST OF LOUISIANA TO SRN TEXAS. ISOLATED SHOWERS ARE ALSO ACROSS S FLORIDA AND POSSIBLE IN THE CENTRAL GULF WHERE WIDESPREAD LOW-LEVEL CLOUDS ARE PRESENT. ALOFT...MOIST WSWLY FLOW DOMINATES AROUND A BROAD UPPER LEVEL TROUGH COVERING THE FAR ERN CONUS. THE STRONG NELY SURFACE WINDS ARE ALREADY DIMINISHING AND WILL CONTINUE TO DROP TO 15 KTS OVER THE NEXT 24 HOURS AS THE SURFACE RIDGE MOVES OFF TO THE E. ISOLATED SHOWERS WILL ALSO LIKELY REMAIN ACROSS THE BASIN. CARIBBEAN SEA... DRY AIR ALOFT AROUND A BROAD UPPER RIDGE OVER THE CARIBBEAN IS KEEPING MUCH OF THE BASIN UNDER CLEAR SKIES AND FAIR CONDITIONS. HOWEVER...DUE TO A SHORTWAVE UPPER LEVEL TROUGH EXTENDING FROM GUATEMALA INTO THE E PACIFIC...UPPER LEVEL DIFFLUENCE IS PRESENT OVER THE AREA JUST E OF CENTRAL AMERICA. THIS ALONG WITH AREAS OF WIND SPEED CONVERGENCE IS HELPING PRODUCE SCATTERED SHOWERS/ISOLATED THUNDERSTORMS N OF HONDURAS FROM 16N-19N BETWEEN 85W-88W...AND E OF NICARAGUA S OF 16N BETWEEN 74W-83W. SOME OF THIS ACTIVITY IS ALSO INFLUENCED BY LOW LEVEL CYCLONIC FLOW AROUND THE MONSOON TROUGH EXTENDING ACROSS PANAMA TO NRN COLOMBIA. A SHEAR LINE REMAINS IN THE NE CARIBBEAN ALONG 16N E OF 69W SUPPORTING ISOLATED SHOWERS WITHIN 30 NM OF THE AXIS. 15 KT ENE WINDS ARE NOTED N OF THE AXIS WHILE 5-10 KT WINDS ARE TO THE S. EXPECT SHOWERS/THUNDERSTORMS TO REMAIN ACROSS THE FAR WRN CARIBBEAN AS WELL AS THE NE PORTION OF THE BASIN AS A SURFACE TROUGH IN THE CENTRAL ATLC DRIFTS WWD. ATLANTIC OCEAN... A WEAK COLD FRONT IS IN THE W ATLC ENTERING THE DISCUSSION AREA NEAR 32N72W TO 30N76W. ISOLATED SHOWERS ARE WITHIN 75 NM EITHER SIDE OF THE AXIS. THE FRONT IS SUPPORTED BY A BROAD UPPER LEVEL TROUGH OVER THE FAR ERN CONUS. AN UPPER LEVEL RIDGE IS TO THE E CENTERED NEAR 34N48W PROVIDING FAIR WEATHER ACROSS THE REMAINDER OF THE W ATLC. AN UPPER LEVEL LOW TO THE S OF THE UPPER RIDGE NEAR 23N55W SUPPORTS A SURFACE TROUGH ALONG 25N61W TO 19N58W. GALE FORCE WINDS ARE NOTED E OF THE AXIS NEAR 26N54W AND EXPECTED TO CONTINUE THROUGH 1800 UTC. MOST OF THE SHOWER ACTIVITY IS ALSO E OF THE AXIS UNDER THE AREA OF DIFFLUENCE ALOFT AROUND THE UPPER LOW WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 18N-23N BETWEEN 44W-55W...AND FROM 23N-28N BETWEEN 51W-58W. A SHEAR AXIS IS TO THE S OF THE SURFACE TROUGH ALONG 16N W OF 59W CONTINUING INTO THE NE CARIBBEAN. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN 150 NM N OF THE AXIS. SURFACE RIDGING DOMINATES THE ERN ATLC AROUND A 1033 MB HIGH NEAR 36N38W SUPPORTED BY BROAD UPPER RIDGING COVERING THE NRN ATLC. A NARROW UPPER LEVEL TROUGH EXTENDS FROM THE CANARY ISLANDS TO E OF THE UPPER LEVEL LOW IN THE CENTRAL ATLC. MAINLY WLY FLOW ALOFT COVERS THE TROPICAL ATLC. EXPECT THE SURFACE TROUGH IN THE CENTRAL ATLC TO DRIFT WWD OVER THE NEXT SEVERAL DAYS. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON