000 AXNT20 KNHC 261745 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU SEP 26 2013 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 1715 UTC. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 10N41W TO 15N43W TO 19N43W MOVING W AT 15 KT. THE WAVE COINCIDES WITH A WEAK SURFACE TO 700 MB TROUGH WITH A 30 TO 35 KT AFRICAN EASTERLY JET CORE EXTENDING FROM WEST AFRICA NEAR 13N17W TO 10N27W TO 14N40W EAST OF THE WAVE AXIS. SCATTERED MODERATE CONVECTION IS FROM 09N-19N BETWEEN 36W-48W. CONVECTION HAS INCREASED WITH THIS WAVE OVER THE PAST 24 HOURS AS THE WAVE HAS MOVED BENEATH THE UPPER LEVEL DIFFLUENT ENVIRONMENT OF AN UPPER LEVEL LOW CENTERED NEAR 19N52W. TROPICAL WAVE EXTENDS FROM 09N52W TO 17N55W MOVING W AT 10-15 KT. THE WAVE REMAINS ASSOCIATED WITH WEAK LOW-LEVEL TROUGHING AND IN THE PAST 24 HOURS HAS MOVED INTO THE STABLE AND SUBSIDENT ENVIRONMENT WEST OF AN UPPER LEVEL LOW CENTERED NEAR 19N52W. ISOLATED MODERATE CONVECTION IS FROM 15N-18N BETWEEN 52W-55W. FARTHER SOUTH...NEAR THE BASE OF THE UPPER LEVEL TROUGHING... SCATTERED MODERATE CONVECTION IS FROM 09N-13N BETWEEN 48W-52W. TROPICAL WAVE EXTENDS FROM 12N64W TO 20N62W MOVING W AT 15 KT. THE WAVE CONTINUES TO EXHIBIT A WEAK SATELLITE SIGNATURE AND HAS LIKELY FRACTURED MOST ENERGY TO THE NORTH GETTING CAUGHT UP WITH A MID-LATITUDE SWEEPING EASTWARD N OF 30N. WATER VAPOR IMAGERY INDICATES THE WAVE IS EMBEDDED WITHIN A VERY DRY AIRMASS ALOFT WITH NO SIGNIFICANT CONVECTION NOTED AT THIS TIME. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 15N17W TO 10N20W TO 05N27W. THE INTERTROPICAL CONVERGENGE ZONE AXIS EXTENDS FROM 05N27W TO 04N31W TO 05N36W. ISOLATED MODERATE CONVECTION IS FROM 06N-09N BETWEEN 10W-16W AND LIKELY ASSOCIATED WITH THE NEXT TROPICAL WAVE TO EMERGE OFF THE WEST AFRICAN COAST IN THE NEXT 24 TO 36 HOURS. ...DISCUSSION... GULF OF MEXICO... A BROAD UPPER LEVEL TROUGH AXIS EXTENDS FROM OVER THE SW NORTH ATLC NEAR 30N77W SW TO A BASE OVER THE WESTERN GULF NEAR 24N98W. WATER VAPOR IMAGERY INDICATES THAT MOST OF THE BASIN N OF 23N IS UNDER THE INFLUENCE OF A VERY DRY AND STABLE AIRMASS ALOFT. AT THE SURFACE...UPPER LEVEL SUPPORT WANES FOR A 1007 MB LOW CENTERED NEAR 28N90W WITH A SURFACE TROUGH ANALYZED SW TO 27N92W AND A SURFACE TROUGH ANALYZED E-NE TO NEAR 29N84W. LOW-LEVEL MOISTURE REMAINS VERY LIMITED ALONG THIS BOUNDARY WITH ONLY A FEW ISOLATED LOW-TOPPED SHOWERS OCCURRING FROM 27N-29N BETWEEN 83W-88W. TO THE NORTH OF THIS SURFACE TROUGH...WATER VAPOR IMAGERY INDICATES A MID-LEVEL SHORTWAVE PROGRESSING OFFSHORE OF THE CAROLINAS THAT IS SUPPORTIVE OF A DEVELOPING COLD FRONT ANALYZED AT 26/1500 UTC FROM SOUTH OF JACKSONVILLE FLORIDA TO 29N86W IN THE NE GULF WATERS. WITH CYCLOGENESIS FORECAST OVER THE SW NORTH ATLC WATERS IN THE VICINITY OF 29N76W BY EARLY FRIDAY...THE COLD FRONT IS EXPECTED TO QUICKLY MOVE EASTWARD W OF 80W BY LATE FRIDAY. THEREAFTER SURFACE RIDGING AND LIGHT ANTICYCLONIC WINDS ARE EXPECTED TO PERSIST ACROSS THE GULF THROUGH THE WEEKEND. FINALLY...S OF 25N WHERE MORE MIDDLE TO UPPER LEVEL MOISTURE IS PRESENT...ISOLATED SHOWERS ARE NOTED ON SATELLITE IMAGERY S OF 23N BETWEEN 91W-98W. CARIBBEAN SEA... AN INVERTED UPPER LEVEL TROUGH AXIS EXTENDS FROM OVER THE WINDWARD PASSAGE NEAR 19N76W SW TO 12N84W PROVIDING MUCH OF THE NW CARIBBEAN WITH NORTHEASTERLY FLOW ALOFT AND OVERALL CLEAR SKIES AND FAIR CONDITIONS. FURTHER SUPPORTING THE TRANQUIL WEATHER IS A 1014 MB SURFACE HIGH CENTERED OVER THE GULF OF BATABANO NEAR 22N82W. FARTHER SOUTH...WITHIN THE MOIST DIFFLUENT SOUTH-SOUTHWESTERLY FLOW ALOFT EAST OF THE UPPER LEVEL TROUGH AXIS...LOW-LEVEL MOISTURE CONVERGENCE IS MAXIMIZED OVER THE SW CARIBBEAN ALONG THE MONSOON TROUGH ANALYZED ALONG 10N/11N BETWEEN NORTHERN COLOMBIA AND COSTA RICA GENERATING SCATTERED SHOWERS AND STRONG TSTMS S OF 14N BETWEEN 74W-84W. OTHERWISE...A WEAK TROPICAL WAVE ALONG 63W REMAINS RELATIVELY PRECIPITATION- FREE AND VOID OF ANY DEEP SIGNIFICANT CONVECTION. SKIES REMAIN MOSTLY CLEAR THIS AFTERNOON E OF 72W AS WATER VAPOR IMAGERY INDICATES VERY DRY AIR ALOFT. HISPANIOLA... CURRENTLY SKIES CONTINUE AS MOSTLY CLEAR WITH FAIR CONDITIONS AS MANY WEATHER OBSERVATIONS PRIMARILY LOCATED AT COASTAL LOCATIONS AROUND THE ISLAND ARE REPORTING FEW LOW-LEVEL CLOUDS AND UNLIMITED VISIBILITIES. THIS OVERALL TREND SHOULD CONTINUE THROUGH THE AFTERNOON AND EVENING HOURS AS EASTERLY WINDS ALOFT PREVAIL AND A DRIER AIRMASS CONTINUES TO SUPPRESS ANY SIGNIFICANT CONVECTION. HOWEVER...GIVEN PEAK DAYTIME HEATING AND INSTABILITY...A FEW ISOLATED SHOWERS AND TSTMS CERTAINLY CANNOT BE RULED OUT OF THE FORECAST THROUGH THE LAST EVENING. IN THE DAYS AHEAD...THE SOUTHERN EXTENT OF A WEAK TROPICAL WAVE CURRENTLY ALONG 63W IS FORECAST TO CLIP ACROSS THE ISLAND SATURDAY PROVIDING A POSSIBLE SLIGHT INCREASE IN CONVECTION DURING THE AFTERNOON AND EVENING HOURS. ATLANTIC OCEAN... A MIDDLE TO UPPER LEVEL LOW IS CENTERED OVER THE MID-ATLC COAST NEAR 36N77W THAT EXTENDS A TROUGH AXIS SOUTH TO 30N77W THEN SW OVER THE CENTRAL FLORIDA PENINSULA AND INTO THE GULF OF MEXICO. THIS TROUGHING SUPPORTS A COMPLEX AREA OF LOW PRESSURE ALONG 30N THAT STRETCHES WESTWARD TO THE U.S. EAST COAST. A 1002 MB LOW IS CENTERED NEAR 31N68W THAT EXTENDS A COLD FRONT ALONG 29N74W TO 30N79W BECOMING STATIONARY TO THE COAST NEAR 31N81W. SCATTERED SHOWERS AND TSTMS ARE OCCURRING PRIMARILY WITHIN THE WARM SECTOR OF THIS SYSTEM FROM 24N-32N BETWEEN 56W-73W. ISOLATED SHOWERS AND TSTMS ARE ELSEWHERE N OF 25N BETWEEN 73W-81W. OTHERWISE... THE REMAINDER OF THE CENTRAL AND EASTERN ATLC REMAINS UNDER THE INFLUENCE OF A FAIRLY BROAD SURFACE RIDGE ANCHORED BY A 1020 MB HIGH CENTERED NEAR 24N37W. A DEEP LAYERED LOW CENTERED WEST- NORTHWEST OF THE IBERIAN PENINSULA NEAR 43N19W SUPPORTS A COLD FRONT ANALYZED FROM 33N20W TO 32N26W TO 34N33W. WIDELY SCATTERED SHOWERS ARE OCCURRING WITHIN 150 NM SOUTH OF THE FRONT. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN