000 AXNT20 KNHC 172351 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT FRI AUG 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...SPECIAL FEATURES... TROPICAL STORM HELENE IS CENTERED NEAR 20.7N 96.1W AT 18/0000 UTC OR ABOUT 80 NM ESE OF TUXPAN MEXICO AND ABOUT 140 NM SE OF TAMPICO MEXICO MOVING N AT 02 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. WIDELY SCATTERED MODERATE CONVECTION IS FROM 19N-23N BETWEEN 93W-99W. SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT2/WTNT32 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. TROPICAL STORM GORDON IS CENTERED NEAR 34.3N 44.0W AT 17/2100 UTC OR ABOUT 850 NM W OF THE AZORES MOVING E AT 17 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 993 MB. MAXIMUM SUSTAINED WIND SPEED IS 55 KT WITH GUSTS TO 65 KT. WIDELY SCATTERED MODERATE CONVECTION IS FROM 33N-36N BETWEEN 41W-45W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 11N24W TO 17N21W MOVING W AT 15-20 KT. THE WAVE IS EMBEDDED WITHIN AN EASTERN ATLC MONSOON GYRE FOCUSED AROUND A 1009 MB LOW CENTERED NEAR 11N24W. TOTAL PRECIPITABLE WATER IMAGERY INDICATES DEEP LAYER MOISTURE IN THE VICINITY OF THE WAVE FROM 08N-15N BETWEEN 18W-24W WITH ISOLATED MODERATE CONVECTION OCCURRING WITHIN 180 NM EITHER SIDE OF THE WAVE AXIS. TROPICAL WAVE EXTENDS FROM 10N39W TO 18N38W MOVING W AT 15-20 KT. THE WAVE REMAINS EMBEDDED WITHIN A BROAD AREA OF ENHANCED DEEP LAYER MOISTURE AS NOTED ON THE TOTAL PRECIPITABLE WATER IMAGERY FROM 06N-16N BETWEEN 30W-41W. GLOBAL MODEL DATA SHOWS THAT THE WAVE COINCIDES WITH A 700 MB TROUGH AXIS ALONG 37W. DUE TO A LARGE DRY AIRMASS ASSOCIATED WITH A SAHARAN AIR LAYER...NO DEEP CONVECTION IS CURRENTLY ASSOCIATED WITH THE WAVE. TROPICAL WAVE EXTENDS FROM 12N63W TO 20N65W MOVING W AT 20-25 KT. MOVING WEST OF THE AREA OF SAHARAN DUST...ISOLATED SHOWERS ARE MORE PLENTIFUL THIS EVENING ACROSS PUERTO RICO...THE LESSER ANTILLES...AND THE EASTERN CARIBBEAN SEA OCCURRING FROM 13N-22N BETWEEN 61W-69W. BROAD LOW-LEVEL CYCLONIC FLOW IS NOTED ACROSS THE CARIBBEAN BETWEEN 60W-70W AND IS EXPECTED TO RESULT IN INCREASED CLOUDINESS AND PRECIPITATION ACROSS HISPANIOLA THROUGH THE WEEKEND. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 21N17W TO 17N20W THEN FROM 11N24W TO A 1010 LOW PRESSURE ARE NEAR 09N35W TO 09N46W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 09N46W TO 08N53W TO 10N61W. SCATTERED MODERATE CONVECTION IS FROM 05N-12N BETWEEN 26W-41W. ...DISCUSSION... GULF OF MEXICO... TROPICAL STORM HELENE CONTINUES TO IMPACT THE SW GULF WATERS THIS EVENING AND IS FORECAST TO TRACK INLAND ACROSS EAST-CENTRAL MEXICO BY EARLY SATURDAY. SCATTERED SHOWERS AND TSTMS ARE OCCURRING S OF 25N W OF 92W OVER THE GULF WATERS INCLUDING INLAND PORTIONS OF EAST-CENTRAL MEXICO FROM 19N-24N FROM THE COAST TO 100W. LOCALLY HEAVY RAINFALL IS EXPECTED TO REMAIN A PRIME HAZARD OVER THE NEXT FEW DAYS AS HIGH POTENTIAL EXISTS FOR FLASH FLOODING AND MUDSLIDES OVER HIGHER TERRAIN. ELSEWHERE OVER THE GULF...BROAD UPPER LEVEL TROUGHING IS OVER THE EASTERN CONUS THAT DIPS SOUTHWARD OVER PORTIONS OF THE NE GULF AND FLORIDA PENINSULA. WITH WEAK PRESSURE TROUGHING ACROSS THE SE CONUS AND PEAK DAYTIME HEATING AND INSTABILITY...SCATTERED SHOWERS AND TSTMS ARE OCCURRING N OF 25N E OF A LINE FROM 25N88W TO 29N95W...INCLUDING INLAND PORTIONS OF LOUISIANA...MISSISSIPPI... AND THE FLORIDA PANHANDLE. AT THE SURFACE HOWEVER...A WEAK RIDGE AXIS EXTENDS FROM THE SW NORTH ATLC ALONG 26N BUT CONTINUES TO BE SECONDARY TO THE STRONGER MIDDLE TO UPPER LEVEL DYNAMICS. CARIBBEAN SEA... NORTHEASTERLY FLOW ALOFT ASSOCIATED WITH AN UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED IN THE GULF OF MEXICO NEAR 22N94W CONTINUES TO PROVIDE AN OVERALL STABLE ATMOSPHERE ACROSS MUCH OF THE WESTERN CARIBBEAN W OF 74W. A FEW ISOLATED SHOWERS AND TSTMS ARE OCCURRING OVER PORTIONS OF CUBA DUE TO PEAK DAYTIME HEATING AND INSTABILITY...HOWEVER THESE ARE EXPECTED TO DIMINISH WITH SUNSET. THE MONSOON TROUGH AXIS EXTENDS ALONG 09N AND IS PROVIDING FOCUS FOR SCATTERED SHOWERS AND TSTMS ACROSS THE SW CARIBBEAN S OF 12N BETWEEN 74W-85W. FARTHER EAST...UPPER LEVEL TROUGHING COVERS THE REMAINDER OF THE CARIBBEAN BETWEEN 62W-74W WITH AXIS EXTENDING FROM AN UPPER LEVEL LOW IN THE ATLC NEAR 26N64W TO 19N70W TO 12N80W. WHILE WATER VAPOR IMAGERY INDICATES A RELATIVELY DRY ATMOSPHERE ALOFT...THE PRESENCE OF A TROPICAL WAVE ALONG 64W IS GENERATING ISOLATED SHOWERS E OF 70W THIS EVENING. ATLANTIC OCEAN... BROAD MIDDLE TO UPPER LEVEL TROUGHING IS OVER THE EASTERN CONUS AND THE INFLUENCE OF THE TROUGHING AND ASSOCIATED DIFFLUENCE ALOFT TO THE EAST OF THE TROUGH AXIS IS GENERATING SCATTERED SHOWERS AND TSTMS ACROSS THE SW NORTH ATLC THIS EVENING N OF 23N W OF 71W...INCLUDING PORTIONS OF THE FLORIDA PENINSULA. EMBEDDED WITHIN THIS TROUGHING...AN UPPER LEVEL LOW IS CENTERED NEAR 27N64W THAT CONTINUES TO GENERATE ISOLATED SHOWERS OVER THE AREA FROM 23N-32N BETWEEN 63W-71W. ELSEWHERE ACROSS THE REMAINDER OF THE CENTRAL AND EASTERN ATLC...A BROAD SURFACE RIDGE SPANS THE LENGTH OF THE BASIN ALONG 26N ANCHORED BY A 1020 MB HIGH CENTERED NEAR 26N48W. THE RIDGE AXIS EXTENDS WESTWARD ALONG 26N INTO THE GULF OF MEXICO...YET AS MENTIONED ABOVE...THE OVERRIDING MIDDLE TO UPPER LEVEL DYNAMICS ACROSS THE SW NORTH ATLC ARE CONTRIBUTING TO THE CONVECTION W OF 63W. OTHERWISE... THE SAHARAN AIR LAYER AND ASSOCIATED DUST IS MAINTAINING STABLE CONDITIONS FROM 20N-32N E OF 63W TO THE AFRICAN COAST. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN