000 AXNT20 KNHC 110545 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 105 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0500 UTC. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS AFRICA TO THE COAST OF GUINEA-BISSAU NEAR 11N15W CONTINUING SW TO 7N19W. THE ITCZ CONTINUES FROM 7N19W ALONG 3N30W 2N43W. ISOLATED MODERATE/STRONG CONVECTION IS WITHIN 250 NM N...120 NM S OF THE AXIS BETWEEN 19W-34W. ...DISCUSSION... GULF OF MEXICO... MAINLY NELY SURFACE FLOW COVERS THE GULF OF MEXICO TONIGHT AROUND A 1035 MB HIGH CENTERED OVER SRN INDIANA. DUE TO THE TIGHT PRESSURE GRADIENT...WINDY CONDITIONS PERSIST UP TO 25 KTS. RADAR IMAGERY INDICATES SCATTERED SHOWERS ARE ACROSS THE NW GULF LIKELY DUE TO WIND CONVERGENCE ALONG THE COASTLINE. 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 ERN CONUS. THE STRONG NELY SURFACE WINDS ARE EXPECTED TO BEGIN DIMINISHING TO 15-20 KTS OVER THE NEXT 24-48 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 SMALL AMOUNTS OF WIND SPEED CONVERGENCE IS HELPING PRODUCE SCATTERED SHOWERS/ISOLATED THUNDERSTORMS N OF HONDURAS FROM 16N-19N BETWEEN 84W-88W...AND E OF NICARAGUA...N OF COSTA RICA AND PANAMA FROM 9N-16N BETWEEN 74W-83W. A SHEAR LINE REMAINS IN THE NE CARIBBEAN ALONG 16N E OF 70W SUPPORTING ISOLATED SHOWERS FROM 16N-18N E OF 70W. 15-20 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 32N75W TO JUST E OF CAPE CANAVERAL NEAR 28N81W. ISOLATED SHOWERS ARE WITHIN 75 NM EITHER SIDE OF THE AXIS. THE FRONT IS SUPPORTED BY AN UPPER LEVEL TROUGH OVER THE ERN CONUS. AN UPPER LEVEL RIDGE IS TO THE E CENTERED NEAR 33N53W PROVIDING FAIR WEATHER ACROSS THE REMAINDER OF THE W ATLC. ACROSS THE CENTRAL ATLC...AN UPPER LEVEL LOW NEAR 22N54W SUPPORTS A SURFACE TROUGH ALONG 27N58W 22N55W 16N60W CONTINUING AS A SHEAR LINE INTO THE NE CARIBBEAN. GALE FORCE WINDS ARE NOTED E OF THE AXIS NEAR 25N51W AND EXPECTED TO CONTINUE THROUGH 1800 UTC. MOST OF THE SHOWER ACTIVITY IS ALSO E OF THE AXIS WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 15N-22N BETWEEN 42W-54W...AND FROM 22N-27N BETWEEN 47W-56W. SIMILAR ACTIVITY IS ALSO WITHIN 150 NM N OF THE SHEAR AXIS. SURFACE RIDGING DOMINATES THE ERN ATLC AROUND A 1034 MB HIGH NEAR 36N40W SUPPORTED BY BROAD UPPER RIDGING COVERING THE NRN ATLC. AN 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