000 AXNT20 KNHC 181800 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT WED JUL 18 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 19N29W TO THE MONSOON TROUGH AXIS NEAR 13N28W. LIMITED MOISTURE SURROUNDS THE WAVE AXIS ON TOTAL PRECIPITABLE WATER IMAGERY...AS A LAYER OF DRY/SAHARAN AIR CONTINUES TO OVERTAKE THE WAVE. THEREFORE...ANY CONVECTIVE ACTIVITY IS CONFINED TO THE EXTREME SRN PORTION OF THE WAVE AXIS ATTACHED TO THE MONSOON TROUGH. TROPICAL WAVE IS HEADING TOWARDS THE LESSER ANTILLES WITH AXIS EXTENDING FROM 19N55W TO 11N54W MOVING W AT 15-20 KT. THE WAVE PRECEDES A NARROW SURGE OF MOISTURE NOTED ON TOTAL PRECIPITABLE WATER IMAGERY WITH LIMITED SHOWER ACTIVITY DUE TO SAHARAN DUST AROUND THE WAVE AXIS. TROPICAL WAVE IS IMPACTING THE ERN COASTAL WATERS AND INLAND PORTIONS OF THE YUCATAN PENINSULA WITH AXIS EXTENDING FROM 23N84W TO 16N85W MOVING W AT ABOUT 15 KT. SCATTERED SHOWERS AND THUNDERSTORMS W OF 85W TO INLAND ACROSS THE YUCATAN PENINSULA. THE SHOWER ACTIVITY IS ENHANCED BY A WEAK UPPER LEVEL CYCLONIC CIRCULATION MOVING ACROSS THE NRN YUCATAN PENINSULA. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS INLAND ACROSS WEST AFRICA...PASSING THROUGH DAKAR SENEGAL TO 12N21W 12N30W 11N36W TO 8N43W...WHERE THE ITCZ CONTINUES ALONG 9N50W TO THE COAST OF GUYANA NEAR 8N58W. SCATTERED MODERATE CONVECTION IS FROM 8N-12N BETWEEN 30W-40W AND FROM 7N-12N BETWEEN 22W-28W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL CYCLONIC CIRCULATION CENTERED OVER ERN GEORGIA CONTINUES TO DOMINATE THE NE GULF WATERS THIS AFTERNOON. THIS FEATURE SUPPORTS A SURFACE TROUGH EXTENDING ACROSS THE SE CONUS INTO THE GULF BASIN ALONG 30N83W TO 27N84W. THIS SYSTEM IS GENERATING SCATTERED SHOWERS AND THUNDERSTORMS N OF 27N E OF 90W. SIMILAR CONVECTION IS FOUND OVER THE WRN GULF COAST W OF 94W N OF VERACRUZ MEXICO. THE ACTIVITY IN THIS REGION IS ASSOCIATED TO AN UPPER LEVEL LOW SPINNING OVER THE NRN MEXICO REGION. RELATIVELY STABLE CONDITIONS ARE ELSEWHERE ACROSS THE AREA THIS AFTERNOON. AS THE UPPER LOW OVER THE SE CONUS DRIFTS NNE...SHORT RANGE COMPUTER MODELS SUGGEST THE RAIN ACTIVITY OVER THE NE GULF WILL SLOWLY MOVE N DURING THE NEXT 24 HOURS. FAIR WEATHER IS EXPECTED TO REMAIN CONSTANT ACROSS THE REMAINDER OF THE GULF DURING THE FORECAST PERIOD. CARIBBEAN SEA... THE TWO MAIN AREAS OF ACTIVE WEATHER ARE FOUND OVER THE FAR NW AND SW CORNERS OF THE BASIN THIS AFTERNOON. A TROPICAL WAVE IS APPROACHING THE ERN COAST OF THE YUCATAN PENINSULA WITH SCATTERED SHOWERS AND THUNDERSTORMS W OF 85W TO INLAND ACROSS THE YUCATAN PENINSULA. THE SHOWER ACTIVITY IS ENHANCED BY A WEAK UPPER LEVEL CYCLONIC CIRCULATION MOVING ACROSS THE NRN YUCATAN PENINSULA...PROVIDING FURTHER LIFTING AND INSTABILITY ACROSS THIS AREA. SIMILAR CONVECTION IS S OF 11N W OF 77W ASSOCIATED TO THE MONSOON TROUGH AXIS EXTENDING ACROSS NRN COLOMBIA TO THE SRN COASTAL WATERS OF PANAMA AND WRN COSTA RICA. THE REMAINDER OF THE DISCUSSION AREA IS UNDER FAIR WEATHER ASSOCIATED TO AN ELONGATED UPPER LEVEL CYCLONIC CIRCULATION CENTERED NE OF PUERTO RICO NEAR 21N64W. MODERATE TO FRESH EASTERLY TRADE WINDS ARE OBSERVED ACROSS THE AREA WITH SOME STRONGER WINDS GUSTING TO NEAR GALE FORCE CRITERIA OVER THE NRN COASTAL WATERS OF COLOMBIA. ATLANTIC OCEAN... THE UPPER LEVEL LOW CONTINUES TO WOBBLE OVER THE SE CONUS THIS AFTERNOON...NOW CENTERED OVER ERN GEORGIA. HOWEVER...THE SHOWER AND THUNDERSTORM ACTIVITY OVER THE WRN ATLC HAVE DECREASED CONSIDERABLY COMPARED TO 24 HOURS AGO. ONLY A FEW ISOLATED SHOWERS AND THUNDERSTORMS ARE OBSERVED N OF 27N BETWEEN 76W-79W. AN UPPER LEVEL ANTI-CYCLONE CENTERED W OF BERMUDA CONTINUES TO SUPPORT A WEAKENING 1024 MB HIGH AROUND 29N67W. HOWEVER...AN ELONGATED UPPER LEVEL CYCLONIC CIRCULATION CENTERED NE OF PUERTO RICO NEAR 21N64W IS GENERATING SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS WITHIN 72 NM ON EITHER SIDE OF A LINE EXTENDING FROM 30N58W TO 20N68W. OTHERWISE...A LARGE AREA OF HIGH PRESSURE DOMINATES THE REMAINDER OF THE ATLC DISCUSSION AREA ANCHORED BY A 1030 MB HIGH CENTERED WSW OF THE AZORES ISLANDS NEAR 37N31W. THE WEATHER IN THIS REGION IS FURTHER ENHANCED BY A LAYER SAHARAN DUST ALOFT NOTED ON METEOSAT-9 E OF 55W. WHILE SOME CONVECTION FROM THE NE GULF IS EXPECTED TO MOVE OVER THE WRN ATLC DURING THE AFTERNOON AND EVENING HOURS OF TODAY... THE OVERALL WEATHER PATTERN IS EXPECTED TO FURTHER IMPROVE OVER THE NEXT 24 HOURS...AS THE UPPER LOW SLOWLY LIFTS NNE AND A SURFACE RIDGE AXIS REBUILDS ACROSS THE WRN ATLC. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GARCIA