000 AXNT20 KNHC 201148 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 AM EST SUN NOV 20 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 1115 UTC. ...SPECIAL FEATURES... AN UPPER LEVEL LOW IS CENTERED NEAR 23N54W WITH AN UPPER LEVEL TROUGH AXIS ORIENTED N-NW TO S-SE ALONG 31N57W TO 13N52W. THIS UPPER LEVEL FEATURE SUPPORTS AN ELONGATED AREA OF SURFACE TROUGHING ACROSS THE CENTRAL ATLC WITH A SURFACE TROUGH ANALYZED FROM 13N52W ALONG 18N53W THROUGH A 1010 MB LOW NEAR 22N54W CONTINUING ALONG 28N52W TO 33N48W WITH WEAKER SURFACE TROUGH ANALYZED FROM 19N58W TO 22N63W. THE DOMINANT EASTERLY SURFACE TROUGH REMAINS THE FOCUS FOR POTENTIAL TROPICAL OR SUB-TROPICAL CYCLONE FORMATION WITH A MEDIUM CHANCE DURING THE NEXT 48 HOURS. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN 45 NM OF LINE FROM 21N52W TO 25N53W. THE ACTIVITY FURTHER E IS ASSOCIATED MORE WITH THE UPPER RIDGE TO THE E RATHER THAN THE LOW/TROUGH ITSELF. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS AFRICA ENTERING THE E TROPICAL ATLC NEAR 12N15W TO 9N18W. THE ITCZ AXIS EXTENDS FROM 9N18W ALONG 7N29W 4N37W TO SOUTH AMERICA NEAR 4N51W. SCATTERED MODERATE/STRONG CONVECTION IS FROM 3N-9N BETWEEN 16W-24W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 2N-8N BETWEEN 24W-35W. CLUSTERS OF SCATTERED MODERATE/STRONG CONVECTION ARE FROM 4N-9N BETWEEN 11W-16W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM 2N-10N BETWEEN 25W-30W AND FROM 6N-10N BETWEEN 30W-35W. ...DISCUSSION... GULF OF MEXICO... BROAD UPPER RIDGE DOMINATES THE GULF ANCHORED IN THE E PACIFIC REGION WITH THE UPPER RIDGE AXIS EXTENDING ACROSS S MEXICO NEAR VERACRUZ TO OVER NE FLORIDA WITH DRY STABLE AIR ALOFT COVERING THE ENTIRE GULF. A SURFACE RIDGE DOMINATES THE GULF ANCHORED IN THE W ATLC EXTENDING AN AXIS ACROSS THE SE CONUS ALONG 30N86W TO NEAR TUXPAN MEXICO. RETURN FLOW IS NOW ESTABLISHED OVER THE NW GULF. OVERCAST LOW CLOUDS WITH SCATTERED SHOWERS ARE IN THE NE GULF WITHIN 60/75 NM OF LINE FROM 27N87W TO INLAND OVER THE FLORIDA PANHANDLE NEAR PANAMA CITY. ISOLATED SHOWERS ARE OBSERVED ON MIAMI AND KEY WEST RADAR OVER THE STRAITS OF FLORIDA FROM 24N TO THE FLORIDA KEYS LEAVING THE REMAINDER OF THE GULF UNDER CLEAR SKIES THIS MORNING. SURFACE RIDGE WILL PERSIST THROUGH MON WITH RETURN FLOW OVER THE NW GULF. A COLD FRONT WILL MOVE OFF THE TEXAS COAST LATE TUE AND EXTEND FROM THE FLORIDA BIG BEND AREA TO VERACRUZ MEXICO BY WED EVENING THEN WILL STALL AND BECOME DIFFUSE ON THU. CARIBBEAN SEA... THE UPPER RIDGE OVER THE GULF OF MEXICO COVERS THE NW CARIBBEAN N OF 15N W OF 78W. A WEAK INVERTED UPPER TROUGH EXTENDS FROM S OF JAMAICA NEAR 17N77W TO NE NICARAGUA NEAR 13N84W GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS INLAND AND WITHIN 75 NM ALONG THE COAST OF NICARAGUA FROM 14N TO THE COSTA RICA BORDER. WEAK NE FLOW ALOFT COVERS THE REMAINDER OF THE CARIBBEAN E OF 77W. DRY STABLE AIR ALOFT DOMINATES THE E CARIBBEAN E OF 75W WITH MOIST TROPICAL AIR OVER THE W CARIBBEAN. SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS DOT THE W CARIBBEAN SW OF LINE FROM THE YUCATAN PENINSULA NEAR 21N87W ALONG 17N80W TO COLOMBIA NEAR 12N72W BEING USHERED IN ON THE STRONG EASTERLY TRADE WINDS. THE MONSOON TROUGH EXTENDS FROM COLOMBIA NEAR 11N75W ALONG 11N79W ACROSS COSTA RICA INTO THE E PACIFIC REGION NEAR 10N84W. ISOLATED LOW LEVEL FAST MOVING SHOWERS ARE POSSIBLE ACROSS THE SE CARIBBEAN S OF 15N E OF 73W ALSO USHERED IN ON THE EASTERLY TRADE WINDS. FRESH TO STRONG NE TO E WINDS WILL PERSIST OVER THE N CARIBBEAN AND N LEEWARD ISLANDS THROUGH MIDWEEK. ATLANTIC OCEAN... A SURFACE RIDGE DOMINATES THE W ATLC EXTENDING INTO THE GULF OF MEXICO ANCHORED BY A 1034 MB HIGH ABOUT 850 NM NE BERMUDA. ISOLATED SHOWERS ARE WITHIN 75 NM OF LINE FROM 26N70W TO OVER S FLORIDA AND INTO THE STRAITS OF FLORIDA NEAR MIAMI. THE ELONGATED UPPER LEVEL TROUGH/SURFACE FEATURES IN THE SPECIAL FEATURES SECTION IS TO THE E OF THE SURFACE RIDGE...SEE ABOVE. A HIGHLY AMPLIFIED UPPER RIDGE IS TO THE E OF THE SPECIAL FEATURES EXTENDING FROM NEAR 12N41W ALONG 23N42W TO BEYOND 32N39W PROVIDING DIFFLUENCE ALOFT TO GENERATE SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS WITHIN 120 NM OF LINE FROM 13N48W TO 25N48W AND WITHIN 150/175 NM OF LINE FROM 25N51W TO BEYOND 32N46W. AN UPPER TROUGH CONTINUES TO DIG S OVER THE E ATLC TO 15N E OF 27W SUPPORTING A COLD FRONT NE OF THE DISCUSSION AREA. THE REMAINDER OF THE E ATLC IS DOMINATED BY A SURFACE RIDGE AXIS THAT EXTENDS THROUGH 32N33W TO 20N27W. STRONG PRESSURE GRADIENT BETWEEN SURFACE RIDGE OVER THE ATLC AND THE PERSISTENT ELONGATED SURFACE TROUGH IN THE SPECIAL FEATURES WILL PRODUCE FRESH TO STRONG NE WINDS ACROSS MOST OF THE AREA THROUGH TONIGHT BEFORE THE SURFACE LOW LIFTS NE MON AND TUE. SOUTHERLY FLOW OFF THE N FLORIDA COAST WILL INCREASE WED AHEAD OF A COLD FRONT EXPECTED TO MOVE INTO THE AREA FROM THE N WED NIGHT. THE FRONT WILL MOVE SE THU AND REACH FROM W OF BERMUDA TO THE COAST OF CENTRAL CUBA BY THU AFTERNOON. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ PAW