000 AXNT20 KNHC 212346 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST MON NOV 21 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 2315 UTC. ...SPECIAL FEATURES... A LARGE-SCALE UPPER LEVEL TROUGH IS LOCATED OVER THE CENTRAL ATLC WITH AXIS EXTENDING FROM 30N57W SW OVER HISPANIOLA TO THE WESTERN CARIBBEAN NEAR 15N83W. EMBEDDED WITHIN THIS TROUGHING... WATER VAPOR IMAGERY INDICATES A SHORTWAVE WITH AXIS FROM 28N54W TO 29N48W. THIS UPPER LEVEL FEATURE SUPPORTS A 1005 MB LOW CENTERED NEAR 28N51W AND A SURFACE TROUGH ANALYZED FROM THE LOW SW TO THE LEEWARD ISLANDS AND INTO THE EASTERN CARIBBEAN SEA. THIS SURFACE LOW REMAINS THE FOCUS FOR POTENTIAL TROPICAL OR SUB-TROPICAL CYCLONE GENESIS WITHIN THE NEXT 48 HOURS. WHILE UPPER LEVEL DIFFLUENCE CONTINUES TO BE MAXIMIZED NORTH AND EAST OF THE SHORTWAVE TROUGHING...SCATTERED MODERATE CONVECTION IS OCCURRING FROM 27N-33N BETWEEN 47W-51W. AS THE LOW CONTINUES TO CREATE A TIGHT PRESSURE GRADIENT AGAINST SURFACE RIDGING TO THE NORTH OF THE DISCUSSION AREA...GALE FORCE WIND CONDITIONS ARE EXPECTED THROUGH THE NEXT 24 TO 48 HOURS. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 08N13W TO 07N15W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 07N15W TO 03N23W TO 07N44W TO 07N58W. WIDELY SCATTERED MODERATE CONVECTION IS FROM 02N-10N BETWEEN 14W-22W AND FROM 02N-06N BETWEEN 22W-33W. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY INDICATES AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED NEAR 21N97W WITH A RIDGE AXIS EXTENDING NE ACROSS THE NORTHERN FLORIDA PENINSULA AND INTO THE SW NORTH ATLC WATERS. DRY AIR AND SUBSIDENT CONDITIONS PREVAIL ALOFT ACROSS THE GULF WHICH IS SUPPORTIVE OF A SURFACE RIDGE ANCHORED BY A 1025 MB HIGH CENTERED OVER SOUTHERN GEORGIA NEAR 31N84W. FAIR WEATHER AND OVERALL STABLE CONDITIONS ARE NOTED ON SATELLITE IMAGERY ACROSS THE BASIN WITH ONLY A SMALL AREA OF ISOLATED SHOWERS OCCURRING FROM 26N-29N BETWEEN 88W-90W...AND ACROSS THE FLORIDA PENINSULA S OF 28N INTO THE PORTIONS OF THE FLORIDA STRAITS. ELSEWHERE...E TO SE WINDS ARE IN THE RANGE OF 10-20 KT THIS EVENING. THE RIDGE IS FORECAST TO BEGIN SLIDING EASTWARD INTO THE SW NORTH ATLC WITH SOUTHERLY RETURN FLOW INCREASING GRADUALLY ACROSS THE WESTERN GULF AS THE NEXT COLD FRONT IS EXPECTED TO MOVE OFF THE TEXAS GULF COAST LATE TUESDAY INTO EARLY WEDNESDAY. CARIBBEAN SEA... AN UPPER LEVEL TROUGH AXIS EXTENDS FROM THE CENTRAL ATLC SPECIAL FEATURE MENTIONED ABOVE INTO THE CARIBBEAN NEAR 20N73W TO A BASE NEAR 15N83W. MAINLY NORTH TO NORTHWESTERLY UPPER LEVEL FLOW IS NOTED OVER THE NW CARIBBEAN WHILE WEST TO SOUTHWESTERLY FLOW IS EAST OF THE TROUGH AXIS. WATER VAPOR IMAGERY INDICATES THAT STRONG SUBSIDENCE AND DRY AIR IS ASSOCIATED WITH THE UPPER LEVEL TROUGHING AND THAT CONDITIONS ACROSS THE CARIBBEAN THIS EVENING ARE FAIRLY TRANQUIL UNDER NE TO E WINDS. THE MOST ACTIVE CONVECTIVE AREA IS LOCATED IN THE SW CARIBBEAN WITH SCATTERED SHOWERS AND TSTMS OCCURRING S OF 13N W OF 80W DUE TO LOW-LEVEL CONVERGENCE AND CLOSE PROXIMITY OF THE MONSOON TROUGH AXIS EXTENDING FROM THE E PACIFIC REGION ALONG 09N/10N TO NORTHERN COLOMBIA. FARTHER EAST...THE UPPER LEVEL TROUGHING SUPPORTS A SURFACE TROUGH EXTENDING INTO THE EASTERN CARIBBEAN NEAR 18N62W TO 14N68W. ISOLATED SHOWERS ARE OCCURRING WITHIN 150 NM NORTHWEST OF THE BOUNDARY. WIDELY SCATTERED SHOWERS ARE ALSO OCCURRING OVER THE SE CARIBBEAN AND WINDWARD ISLANDS S OF 15N BETWEEN 60W-65W. ATLANTIC OCEAN... AN UPPER LEVEL RIDGE AXIS EXTENDS FROM THE WESTERN GULF OF MEXICO NORTHEASTWARD ACROSS THE NORTHERN FLORIDA PENINSULA INTO THE SW NORTH ATLC WATERS TO BEYOND 32N78W. THIS UPPER LEVEL RIDGE SUPPORTS A 1025 MB HIGH CENTERED OVER SOUTHERN GEORGIA AND A 1024 MB HIGH CENTERED NEAR 32N71W. MOSTLY NE WINDS DOMINATE ACROSS THE W ATLC DISCUSSION AREA WEST OF 60W WITH ISOLATED SHOWERS POSSIBLE FROM 21N-30N W OF 62W. FARTHER EAST...AN UPPER LEVEL TROUGH IS OVER THE CENTRAL ATLC WITH AXIS EXTENDING FROM 30N57W SW OVER HISPANIOLA INTO THE WESTERN CARIBBEAN SEA. THIS TROUGH LARGELY SUPPORTS THE 1005 MB SPECIAL FEATURES LOW AND AREA OF CONVECTION LOCATED MAINLY WITHIN THE NE QUADRANT OF THE LOW FROM 27N-33N BETWEEN 47W-51W. THE REMAINDER OF THE EASTERN ATLC IS UNDER THE INFLUENCE OF SURFACE RIDGING PROVIDING NE TO E WINDS IN THE 15 TO 20 KT RANGE S OF 32N E OF 30W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN