000 AXNT20 KNHC 132341 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT THU SEP 13 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 2335 UTC. ...SPECIAL FEATURES... TROPICAL STORM NADINE IS CENTERED NEAR 24.0N 53.0W 13/2100 UTC OR ABOUT 765 MI...1230 KM ENE OF THE NORTHERN LEEWARD ISLANDS MOVING NW AT 14 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 990 MB. MAXIMUM SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 22N-27N BETWEEN 48W-55W. ...TROPICAL WAVES... A TROPICAL WAVE AXIS IS ANALYZED FROM 15N43W ALONG A 1012 MB LOW LEVEL CENTER NEAR 10N41W TO 7N38W MOVING W 10-15 KT. THIS SYSTEM IS EMBEDDED IN A SURGE OF MODERATE MOISTURE VALUES ON TOTAL PRECIPITABLE WATER IMAGERY. THIS SYSTEM IS ALSO EMBEDDED IN DRY SAHARAN AIR ALOFT LIMITING THE CONVECTIVE ACTIVITY NEAR THE CENTER. ONLY A SMALL AREA OF SCATTERED WEAK CONVECTION IS N OF THE LOW LEVEL CENTER FROM 11N-15N BETWEEN 40W-45W. ...ITCZ/MONSOON TROUGH... THE OCEANIC MONSOON TROUGH IS ANALYZED FROM THE NRN COAST OF GUINEA NEAR 11N15W TO 9N27W...WHERE THE ITCZ AXIS CONTINUES TO 11N37W. THE ITCZ REDEVELOPS SW OF A TROPICAL WAVE NEAR 8N44W TO 7N55W. SCATTERED MODERATE CONVECTION IS FROM 5N-11N E OF 30W. ISOLATED WEAK CONVECTION IS WITHIN 50 NM ON EITHER SIDE OF THE ITCZ BETWEEN 44W-50W. ...DISCUSSION... GULF OF MEXICO... SEVERAL AREAS OF CONVECTION ARE KEEPING THE WEATHER ACROSS THE GULF UNSETTLED THIS EVENING. AN ELONGATED UPPER LEVEL LOW IS NOTED ON WATER VAPOR IMAGERY MOVING ACROSS THE SE CONUS. THIS FEATURE EXTENDS AN UPPER TROUGH INTO THE CENTRAL GULF PROVIDING FOCUS FOR SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS N OF 26N BETWEEN 85W-89W. UPPER LEVEL DIVERGENCE OVER THE WRN GULF IS GENERATING SIMILAR CONVECTION NEAR THE COASTAL WATERS OF MEXICO FROM 21N-26N W OF 95W. THE REMNANTS OF A DISSIPATING STATIONARY FRONT ANALYZED FROM THE WRN NORTH ATLANTIC TO OVER THE STRAITS OF FLORIDA CONTINUE TO PROVIDE SCATTERED SHOWERS TO THE ERN GULF AND THE YUCATAN CHANNEL E OF 85W S OF 28N. THIS LEAVES THE CENTRAL GULF AND BAY OF CAMPECHE THE ONLY AREAS WHERE FAIR WEATHER CONDITIONS PREVAIL. MARINE OBSERVATIONS ACROSS THE GULF SHOW EASTERLY WINDS 10-15 KT ACROSS THE BASIN...OCCASIONALLY GUSTING TO 20 KT. SHORT RANGE COMPUTER MODELS SUGGEST THE WEATHER ACROSS THE GULF WILL REMAIN UNSTABLE DURING THE NEXT 24 HOURS. CARIBBEAN SEA... THE REMNANTS OF A DISSIPATING STATIONARY FRONT N OF CUBA COASTAL WATERS CONTINUE TO GENERATE SCATTERED SHOWERS INLAND W OF 80W...SOME OF THESE REACHING THE WATERS NEAR THE YUCATAN CHANNEL. THE REMAINDER OF THE NW AND CENTRAL BASIN ARE DOMINATED BY DRY AIR AND STRONG SUBSIDENCE ALOFT PROVIDED BY A BROAD UPPER RIDGE CENTERED OVER THE NW BAHAMAS...SUPPRESSING DEEP CONVECTION AND ONLY ALLOWING FOR A FEW ISOLATED LOW-TOP SHOWERS DOTTING THE DISCUSSION AREA TONIGHT. HOWEVER...AN ELONGATED UPPER LOW DRIFTS WESTWARD CENTERED JUST A FEW MILES N OF PUERTO RICO GENERATING SCATTERED MODERATE TO HEAVY SHOWERS N OF 15N E OF 68W EVIDENT ON SAN JUAN DOPPLER RADAR IMAGERY. SIMILAR CONVECTION IS NOTED S OF 13N W OF 75W...ASSOCIATED TO THE ERN PACIFIC MONSOON TROUGH EXTENDING ACROSS COSTA RICA TO NRN COLOMBIA. FAIR WEATHER CONDITIONS WITH A FEW ISOLATED SHOWERS WILL PREDOMINATE ACROSS THE DISCUSSION AREA DURING THE NEXT 24 HOURS. MODERATE TO ISOLATED STRONG CONVECTION WILL LINGER OVER THE SW BASIN DURING THE FORECAST PERIOD. ATLANTIC OCEAN... AN UPPER LEVEL TROUGH CONTINUES TO MOVE ACROSS THE WRN NORTH ATLANTIC SUPPORTING A STATIONARY FRONT EXTENDING INTO OUR DISCUSSION AREA AS A SURFACE TROUGH ALONG 31N63W 24N70W TO ACROSS THE BAHAMAS AS A DISSIPATING STATIONARY FRONT NEAR 24N75W AND INTO THE FAR ERN GULF OF MEXICO ACROSS THE STRAITS OF FLORIDA. SCATTERED MODERATE TO HEAVY SHOWERS AND THUNDERSTORMS ARE NOTED WITHIN 90-120 NM ON EITHER SIDE OF THE FRONT W OF 75W. ISOLATED WEAK SHOWERS ARE ALSO WITHIN 80 NM ON EITHER SIDE E OF 70W. THIS FRONTAL BOUNDARY IS EXPECTED TO CONTINUE TO WEAKEN OVER THE NEXT 12-24 HOURS. TROPICAL STORM NADINE IS WELL TO THE ENE OF THE LESSER ANTILLES. SEE SPECIAL FEATURE ABOVE FOR MORE DETAILS ON NADINE. THE REMAINDER OF THE ATLC BASIN DISCUSSION AREA IS DOMINATED BY A SURFACE RIDGE OF HIGH PRESSURE ANCHORED BY A 1021 MB HIGH NEAR 32N44W. THE OVERALL FAIR WEATHER IS ENHANCED ALOFT BY THICK LAYER OF SAHARAN DUST NOTED ON METEOSAT-9 SAL PRODUCT E OF 50W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GARCIA