000 AXNT20 KNHC 110000 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST SAT DEC 10 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2345 UTC. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH ENTERS THE ATLC WATERS ACROSS THE COAST OF GUINEA-BISSAU NEAR 12N16W TO 6N20W. THE ITCZ CONTINUES FROM THIS POINT WESTWARD ALONG 3N30W 4N40W TO 5N48W. SCATTERED MODERATE CONVECTION IS WITHIN 90 NM ON EITHER SIDE OF THE ITCZ BETWEEN 20W-40W. ...DISCUSSION... GULF OF MEXICO... A STRONG 1037 MB HIGH IS MOVING ACROSS THE ERN CONUS THIS EVENING. THE MOVEMENT OF THIS FEATURE IS CREATING A TIGHT SURFACE PRESSURE GRADIENT OVER MOST OF THE NRN HALF OF THE GULF...WITH MARINE OBSERVATIONS INDICATING GUSTY NE WINDS UP TO 25 KT N OF 24N. SPEED CONVERGENCE FLOW IS NOTICED NEAR THE TEXAS AND MEXICO COAST N OF TAMPICO W OF 94W. DOPPLER RADAR IMAGERY INDICATES SCATTERED WEAK SHOWERS IN THIS REGION. BROAD SURFACE TROUGHINESS COVERS THE FLORIDA PENINSULA INCLUDING THE STRAITS AND NW CUBA. SLOW MOVING SCATTERED HEAVY SHOWERS AND THUNDERSTORMS ARE S OF 26N E OF 83W. OVERCAST LOW LEVEL STRATOCUMULUS CLOUDS WITH A FEW POSSIBLE ISOLATES SHOWERS ARE ELSEWHERE ACROSS THE DISCUSSION AREA. THE OVERALL ACTIVITY ACROSS THE GULF IS EXPECTED TO REMAIN SIMILAR OVER THE NEXT 24 HOURS AS AN ELONGATED UPPER LEVEL SHORTWAVE MOVES ACROSS NRN BASIN. WHILE SIMILARITIES REMAIN BETWEEN COMPUTER MODELS...THE RAIN ACTIVITY IS LIKELY TO SPREAD TO THE CENTRAL BASIN DURING THE FORECAST PERIOD. CARIBBEAN SEA... A SHEAR LINE IS ANALYZED OVER THE NW CARIBBEAN FROM 20N82W TO CENTRAL HONDURAS NEAR 15N86W. MARINE OBSERVATIONS IN THIS REGION SUGGESTED THE WIND SPEED GRADIENT ALONG THE LINE HAS DECREASED DURING THE PAST 6 HOURS...YET THE SHOWER/THUNDERSTORM ACTIVITY REMAINS WITHIN 170 NM W OF THE AXIS. A SIMILAR SHEAR LINE EXTENDS INTO THE FAR NE CARIBBEAN ALONG BARBUDA TO NEAR 16N69W. A RECENT SATELLITE SCATTEROMETER PASS OVER THIS AREA REVEALED E-NE CONVERGING LOW LEVEL WINDS INCREASING FROM 5 KT T0 25 KT FROM S TO N ALONG THE AXIS...GENERATING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS AFFECTING THE WATERS NEAR PUERTO RICO AND THE LESSER ANTILLES N OF DOMINICA E OF 70W. THE CONVECTION IN THIS REGION IS EXPECTED TO CONTINUE BUT DECREASE IN INTENSITY OVER THE NEXT 24 HOURS. BROAD CYCLONIC TURNING IS OBSERVED IN THE MULTI LAYER CLOUD FIELD OVER THE SW BASIN...IN RESPONSE OF THE LOWER PRESSURE REGION ASSOCIATED TO THE MONSOON TROUGH ANALYZED ACROSS COSTA RICA INTO NRN COLOMBIA. SCATTERED SHOWERS AND THUNDERSTORMS ARE S OF 16N W OF 75W. THE REMAINDER OF THE CARIBBEAN SEA IS UNDER FAIR WEATHER THIS EVENING. ATLANTIC OCEAN... AN UPPER LEVEL SHORTWAVE MOVES ACROSS THE SE CONUS SUPPORTING A COLD FRONT EXTENDING ACROSS THE WRN N ATLC. AS THE FRONT ENTERS OUR REGION IT BECOMES NEARLY STATIONARY/SURFACE TROUGH ALONG 3275 INTO THE FLORIDA PENINSULA S OF DAYTONA BEACH. AS THE UPPER SHORTWAVE MOVES OFF THE SEABOARD...THE FRONTAL BOUNDARY IS EXPECTED TO LIFT NE INTO THE N CENTRAL ATLC WITHIN THE NEXT 12 HOURS. A BROAD UPPER LEVEL LOW SPINS NEAR 22N57W SUPPORTING A SURFACE TROUGH EXTENDING FROM 25N50W ALONG 18N50W TO 17N58W WHERE IT BECOMES A SHEAR LINE EXTENDING W INTO THE CARIBBEAN ALONG THE ISLAND OF DOMINICA. SCATTERED MODERATE SHOWERS AND THUNDERSTORMS ARE WITHIN 200-250 NM E OF THE SURFACE TROUGH OF 15N. BROAD CYCLONIC TURNING 15-25 KT IS OVER A GREAT PORTION OF THE CENTRAL ATLC SURROUNDING THE SURFACE TROUGH...WITH GALE FORCE WINDS FROM 23N TO 29N BETWEEN 47W AND 54W...GENERATING SEAS 12 TO 18 FT IN NE SWELL. WEATHER CONDITIONS ELSEWHERE ACROSS THE BASIN REMAIN FAIR DUE TO A LARGE/STRONG 1033 MB HIGH CENTERED NEAR 35N38W. THE CENTRAL ATLC SURFACE TROUGH WILL MOVE WESTWARD DURING THE NEXT 24 HOURS. AT THE SAME TIME...A BROAD SURFACE RIDGE CURRENTLY MOVING ACROSS THE ERN CONUS WILL APPROACH THE FAR WRN ATLC. THIS WILL MAKE THE SURFACE PRESSURE GRADIENT OVER THE WRN ATLC TO CONTRACT AND GENERATE GUSTY NE WINDS UP TO 30 KT W OF 65W N OF 23N DURING THE TIME PERIOD. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GARCIA