000 AXNT20 KNHC 082349 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST THU MAR 08 2012 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. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH EXTENDS SW FROM THE AFRICAN COAST AT 08N13W TO 03N16W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ WHICH CONTINUES WESTWARD ALONG 02N TO 40W THEN TURNS SW TO THE EQUATOR AT THE COAST OF S AMERICA. LOCALLY BROKEN LOW AND MID LEVEL CLOUDS...WITH EMBEDDED SHOWERS...ARE OBSERVED WITHIN 120 NM EITHER SIDE OF A LINE FROM 02N24W TO 06N48W. ...DISCUSSION... THE GULF OF MEXICO... AN UPPER ANTICYCLONE IS QUASI STATIONARY OVER THE E PACIFIC NEAR 13N97W...WITH AN UPPER RIDGE EXTENDING NE ACROSS CENTRAL MEXICO AND THE BAY OF CAMPECHE TO THE WESTERN FLORIDA PANHANDLE...AND CONTINUING NE ALONG THE EASTERN SEABOARD OF THE CONUS. LOOKING UPSTREAM...A DEEP LAYERED SHORTWAVE TROUGH DISSECTS THE CENTRAL CONUS ENHANCING CONSIDERABLE CONVECTION WITH SOME OF THE RESULTANT UPPER DEBRIS MOISTURE...MOSTLY FROM PREVIOUS CONVECTION OVER CENTRAL TEXAS...NOW SPILLING E ACROSS THE UPPER RIDGE OVER THE NW GULF OF MEXICO. THIN BROKEN CIRRIFORM CLOUDS ARE RACING NE ACROSS CENTRAL OLD MEXICO AND ACROSS THE WESTERN BAY OF CAMPECHE. OTHERWISE...THE UPPER LEVELS APPEAR DRY ACROSS THE GULF OF MEXICO. AT THE LOW LEVELS A STATIONARY RIDGE DISSECTS THE GULF FROM NW FLORIDA TO THE BAY OF CAMPECHE. SCATTERED LOW LEVEL CLOUDS...WITH ONLY A FEW SHOWERS...CONTINUE TO MOVE N OVER THE E CENTRAL GULF WATERS. A SHRINKING AREA OF LOCALLY OVERCAST LOW LEVEL CLOUDS...AND PATCHY FOG REDUCING VISIBILITIES BELOW 3 SM...IS MOVING N IN THE 15 TO 20 KT LOW LEVEL SOUTHERLY FLOW OVER THE NW GULF...EXTENDING INLAND OVER THE NE TEXAS AND SW LOUISIANA COASTAL PLAINS. THE SURFACE RIDGE IS EXPECTED TO SHIFT EASTWARD TONIGHT ALLOWING A COLD FRONT TO MOVE INTO THE NW WATERS ON FRI ACCOMPANIED BRIEFLY BY NORTHERLY WINDS TO 30 KT. THE FRONT STALLS LATE FRI NIGHT INTO SAT WITH THE NORTHERLY WINDS DIMINISHING TO 20 KT. THE CARIBBEAN SEA... AN UPPER TROUGH CONTINUES OVER THE CENTRAL CARIBBEAN WITH ITS MEAN AXIS EXTENDING FROM THE WINDWARD PASSAGE TO THE NW COAST OF COLOMBIA...AND IS ACCOMPANIED BY VERY DRY AIR ALOFT. LOCALLY BROKEN LOW LEVEL CLOUDS...WITH BRIEF SHOWERS...ARE RACING WESTWARD OVER THE CARIBBEAN TO THE N OF 15N AND DOWNSTREAM OF THE LARGER WINDWARD ISLANDS. THE EASTERLY TRADES ARE ENHANCED ALONG THE NW COAST OF COLOMBIA WITH A 30 TO 35 KT GALE WARNING IN EFFECT FROM 11N TO 15N BETWEEN 73W AND 79W THIS AFTERNOON... BUT THE EFFECTED AREA IS FORECAST TO SHRINK FROM 11N TO 13N BETWEEN 73W AND 77W ON FRI THEN DIMINISH BELOW GALE FRIDAY EVENING. THE ASSOCIATED SEAS TO 18 FT TONIGHT WILL SUBSIDE TO ABOUT A 16 FT MAXIMUM ON FRI...AND FURTHER SUBSIDE TO 14 FT ON FRI NIGHT. THE ATLANTIC OCEAN... AN UPPER RIDGE IS ORIENTATED SW TO NE ALONG THE EASTERN SEABOARD OF THE CONUS WITH DENSE UPPER MOISTURE OBSERVED W OF THE RIDGE AXIS...AND WILL LIKELY SHIFT E OVER THE COASTAL WATERS OF GEORGIA AND FLORIDA TONIGHT. THE NORTHERN SEGMENT OF A DEEP LAYERED TROUGH MOVING INTO THE N CENTRAL ATLANTIC IS MERGING WITH THE REMNANTS OF AN UPPER CYCLONE THAT PREVIOUSLY CUT OFF OVER THE N CENTRAL PORTION OF THE DISCUSSION AREA. THE SOUTHERN SEGMENT OF THE UPPER TROUGH EXTENDS FROM NEAR BERMUDA TO THE WINDWARD PASSAGE. UPPER DIFFLUENCE IS ENHANCING CONVECTION ALONG A DISSIPATING LOW LEVEL SHEAR AXIS THAT EXTENDS FROM 31N35W TO 24N60W TO THE CENTRAL BAHAMAS...WITH SOME EVIDENCE OF THE SHEAR AXIS CONTINUING NW ACROSS SOUTHERN FLORIDA WHERE CONVECTION HAS PERSISTED FOR NEARLY 24 HOURS. UPPER MOISTURE IS SWINGING CYCLONICALLY THROUGH THE TROUGH NEAR 24N70W. A DEEP TROPICAL UPPER ANTICYCLONE IS NEAR 04N27W WITH A RIDGE EXTENDING N TO A CREST AT 32N60W. A LARGE AREA OF OVERCAST MULTILAYERED CLOUDS IS OBSERVED UNDER THE RIDGE CREST WITHIN 120 NM OF 28N60W WITH LIGHTNING DATA DETECTING EMBEDDED TSTMS NEAR 26N58W. UPPER DEBRIS MOISTURE FROM THIS CLOUDINESS AND CONVECTION IS ADVECTED E IN A 200 NM WIDE BAND FROM 27N50W TO 28N38W TO WELL BEYOND 32N32N. AN UPPER TROUGH IS DIGGING S OVER NW AFRICA WITH ITS MEAN AXIS EXTENDING FROM 31N07W TO A BASE NEAR 19N01E AT THE MOMENT. A SECOND RIDGE EXTENDS NE FROM THE DEEP TROPICAL ANTICYCLONE AT 04N27W TO A CREST AT 28N20W. A VERY DENSE MOISTURE PLUME... ORIGINATING OVER S AMERICA...IS STREAMING E ACROSS THE DISCUSSION AREA S OF 15N BETWEEN 35W AND 60W...FANNING OUT UNDER THE UPPER RIDGE OVER THE AREA FROM 10N TO 27N BETWEEN 30W AND 10W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ NELSON