000 AXNT20 KNHC 171804 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT TUE JUL 17 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1745 UTC. ...TROPICAL WAVES... TROPICAL WAVE MOVES ACROSS THE ERN TROPICAL ATLC WITH AXIS ANALYZED FROM 21N21W TO THE MONSOON TROUGH AXIS NEAR 15N20W. WAVE PRECEDES A SURGE OF DEEP MOISTURE NOTED ON TOTAL PRECIPITABLE WATER IMAGERY. HOWEVER...NO CONVECTION IS CURRENTLY ASSOCIATED TO THE WAVE DUE TO HIGH REFLECTIVITY VALUES OF DRY/SAHARAN AIR NOTED ON METEOSAT-9. TROPICAL WAVE MOVES ACROSS THE CENTRAL TROPICAL ATLC EXTENDING FROM 19N47W TO 11N48W MOVING W AT 15-20 KT. THE WAVE PRECEDES A SURGE OF MOISTURE NOTED ON TOTAL PRECIPITABLE WATER IMAGERY WITH LIMITED SHOWER ACTIVITY DUE TO SAHARAN DUST AROUND THE AXIS. TROPICAL WAVE MOVES ACROSS THE NW CARIBBEAN WITH AXIS EXTENDING FROM 24N78W ACROSS CENTRAL CUBA TO 16N78W MOVING W AT ABOUT 15 KT. THE WAVE IS BECOMING LESS DISTINCT ON TOTAL PRECIPITABLE WATER IMAGERY. THE WAVE IS CURRENTLY UNDERGOING AN AREA OF SAHARAN DUST ALOFT NOTED ON METEOSAT-9. UPPER LEVEL SOUNDINGS FROM JAMAICA AND GRAND CAYMAN INDICATED THE PASSAGE OF THE WAVE AS WELL AS THE CLASSIC DOUBLE TEMPERATURE INVERSION PATTERN ASSOCIATED TO THE SAHARAN AIR LAYER. THEREFORE...NO SIGNIFICANT CONVECTION IS CURRENTLY NOTED. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS INLAND ACROSS WEST AFRICA...PASSING THROUGH THE COAST OF SENEGAL ALONG 14N17W TO 15N21W 8N36W 10N44W TO 9N49W...WHERE THE ITCZ CONTINUES ALONG 7N53W TO THE COAST OF GUYANA NEAR 6N58W. SCATTERED MODERATE CONVECTION IS FROM 5N-10N BETWEEN 30W-45W AND FROM 6N-13N E OF 23W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL CYCLONIC CIRCULATION OVER NE FLORIDA CONTINUES TO DOMINATE THE ERN GULF THIS AFTERNOON...SUPPORTING A SURFACE TROUGH ANALYZED FROM 30N83W TO 26N86W. THIS SYSTEM IS GENERATING SCATTERED SHOWERS AND THUNDERSTORMS FROM 25N-29N E OF 87W. SIMILAR CONVECTION IS FOUND WITHIN 170 NM OFF THE WRN GULF COAST FROM TAMPICO MEXICO TO MATAGORDA BAY TEXAS. THE ACTIVITY IN THIS REGION IS ASSOCIATED TO A NARROW UPPER LEVEL TROUGH EXTENDING ACROSS N-CENTRAL TEXAS TO NE MEXICO. SHORT RANGE COMPUTER MODELS SUGGEST THE RAIN ACTIVITY OVER THE ERN GULF WILL BEGIN TO IMPACT THE COASTAL WATERS OF MISSISSIPPI AND ALABAMA DURING THE NEXT 24 HOURS. FAIR WEATHER IS EXPECTED TO REMAIN CONSTANT ACROSS THE REMAINDER OF THE GULF WITH A FEW SHOWERS/ISOLATED THUNDERSTORMS TRAVELING WEST ACROSS THE BAY OF CAMPECHE DURING THE FORECAST PERIOD. CARIBBEAN SEA... A WEAK UPPER LEVEL CYCLONIC CIRCULATION IS NOTED OVER THE YUCATAN CHANEL ON WATER VAPOR IMAGERY. THIS FEATURE IS HELPING TO GENERATE A FEW SHOWERS AND THUNDERSTORMS OVER THE FAR NW CARIBBEAN BASIN W OF 83W TO INLAND ACROSS THE YUCATAN PENINSULA N OF 18N. TO THE E OF THIS AREA OF CONVECTION...A TROPICAL WAVE MOVES ACROSS THE WATERS S OF CUBA AND W OF JAMAICA WITH VERY LIMITED CONVECTION DUE TO SAHARAN DUST ALOFT IN THE VICINITY OF THE WAVE NOTED ON METEOSAT-9. THE REMAINDER OF THE DISCUSSION AREA IS UNDER FAIR WEATHER ASSOCIATED TO AN UPPER LEVEL ANTI CYCLONE CENTERED OVER THE SW CARIBBEAN AND A DRY UPPER LEVEL TROUGH E OF 72W. MODERATE TO FRESH EASTERLY TRADE WINDS ARE OBSERVED ACROSS THE AREA WITH SOME STRONGER WINDS GUSTING TO NEAR GALE FORCE CRITERIA OVER THE COASTAL WATERS NEAR COLOMBIA. THE FAIR WEATHER OVER THE ERN CARIBBEAN IS FURTHER ENHANCED BY SAHARAN DUST ALOFT NOTED ON METEOSAT-9. ATLANTIC OCEAN... AN UPPER LEVEL LOW IS CENTERED INLAND OVER THE FAR NE FLORIDA PENINSULA CONTINUES TO GENERATE SCATTERED SHOWERS AND THUNDERSTORMS N OF 25N W OF 75W INCLUDING THE NW BAHAMAS. AN UPPER LEVEL ANTI-CYCLONE OVER THE ISLAND OF CONTINUES TO SUPPORT A NEARLY STATIONARY 1021 MB HIGH AROUND 26N66W...EXPECTED TO START DRIFTING N DURING THE NEXT 24 HOURS. THE SOUTHERN EXTENSION OF A WEAKENING SURFACE TROUGH AXIS ENTERS OUR REGION FROM 32N52W TO 27N54W SUPPORTING A FEW ISOLATED SHOWERS IN THE VICINITY OF A SURFACE TROUGH. THIS FEATURE IS EXPECTED TO DISSIPATED OVER THE NEXT 6-9 HOURS. OTHERWISE...A LARGE AREA OF HIGH PRESSURE DOMINATES THE REMAINDER OF THE ATLC DISCUSSION AREA ANCHORED BY A 1031 MB HIGH CENTERED WELL E OF THE IBERIAN PENINSULA NEAR 41N19W. THE WEATHER IN THIS REGION IS FURTHER ENHANCED BY A LAYER SAHARAN DUST ALOFT NOTED ON METEOSAT-9 E OF 50W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GARCIA