000 AXNT20 KNHC 292349 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT THU AUG 29 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...SPECIAL FEATURES... TROPICAL WAVE EXTENDS FROM 09N16W TO 20N13W MOVING W AT 10-15 KT. A 1008 MB LOW IS CENTERED ALONG THE WAVE AXIS NEAR 15N15W. ALTHOUGH THIS WAVE HAS YET TO FULLY EMERGE OFF THE COAST OF WEST AFRICA...IT DISPLAYS PLENTY OF SURFACE TO 700 MB VORTICITY WITH A MAXIMUM IN THE VICINITY OF THE SURFACE LOW AND AREAS TO THE SOUTH ALONG THE WAVE AXIS. SCATTERED MODERATE CONVECTION IS OCCURRING FROM 10N-12N BETWEEN 14W-18W...WITH ISOLATED MODERATE CONVECTION ELSEWHERE FROM 09N-18N BETWEEN 10W-19W. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 11N46W TO 19N45W MOVING W AT 10-15 KT. BROAD LOW-LEVEL CYCLONIC TURNING IS EVIDENT IN SATELLITE IMAGERY ABOUT THE WAVE AXIS WITH A 700 MB RELATIVE VORTICITY MAXIMUM CENTERED IN THE VICINITY OF 15N46W. TOTAL PRECIPITABLE WATER IMAGERY ALSO SHOWS MAXIMUM VALUES SURROUNDING THE AXIS FROM 13N-20N BETWEEN 37W-51W. CONVECTION WITH THE WAVE HAS INCREASED OVER THE PAST 24 HOURS WITH WIDELY SCATTERED MODERATE CONVECTION OCCURRING WITHIN 90 NM EITHER SIDE OF A LINE FROM 13N33W TO 18N45W NEAR THE NORTHERN EXTENT OF THE WAVE AXIS. TROPICAL WAVE EXTENDS FROM 15N64W TO 22N61W MOVING W-NW AT 15-20 KT. OVERALL THE WAVE COINCIDES WITH WEAK SURFACE TO 700 MB LOW- LEVEL TROUGHING...HOWEVER SOME OF THE VORTICITY LOCATED NEAR THE SOUTHERN EXTENT OF THE WAVE AXIS 24 HOURS AGO HAS BEEN LEFT BEHIND TO THE SOUTHEAST AS THE WAVE CONTINUES ITS W-NW MOVEMENT. WHILE A FEW SHOWERS AND TSTMS REMAIN TO THE EAST OF THE LESSER ANTILLES...ISOLATED MODERATE CONVECTION IS OCCURRING FROM 19N- 23N BETWEEN 57W-65W. TROPICAL WAVE EXTENDS FROM 08N96W TO 19N94W MOVING W AT 10-15 KT. WHILE MOST OF THE WAVE LIES IN THE EAST PACIFIC REGION... OVERALL THE WAVE AXIS COINCIDES WITH BROAD 700 MB TROUGHING S OF 23N BETWEEN 89W-98W. WIDELY SCATTERED MODERATE CONVECTION IS FROM 15N-19N BETWEEN 92W-96W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 14N17W TO 11N29W TO 10N34W TO 11N43W. ISOLATED MODERATE CONVECTION IS FROM 05N-12N BETWEEN 21W-33W. ...DISCUSSION... GULF OF MEXICO... A MIDDLE TO UPPER LEVEL LOW IS CENTERED OVER THE FLORIDA KEYS NEAR 25N82W THAT IS PROVIDING FOR A FEW ISOLATED SHOWERS THIS EVENING OVER THE FLORIDA PENINSULA AND ADJACENT COASTAL WATERS IN THE VICINITY OF 27N83W. WATER VAPOR IMAGERY INDICATES MOST OF THE GULF IS HOWEVER UNDER A FAIRLY DRY AND STABLEE AIRMASS. THIS IS FURTHER SUPPORTED BY OVERALL SURFACE RIDGING MAINLY NOTED N OF 22N. ONE COMPROMISE TO THE RIDGE IS A WEAK SURFACE TROUGH ANALYZED FROM 24N90W TO 28N90W. WHILE NO SIGNIFICANT DEEP CONVECTION IS NOTED WITH THE TROUGH...A SUBTLE WIND SHIFT ACROSS THE CENTRAL GULF IS APPARENT IN SHIP OBSERVATIONS...BUOYS...AND A FEW OF THE OFFSHORE OIL PLATFORMS. ACROSS THE SW GULF..THE NORTHERN EXTENT OF A TROPICAL WAVE IS ALONG 94W AND CONTINUES TO PROVIDE FOCUS FOR ISOLATED SHOWERS AND TSTMS S OF 19N BETWEEN 93W-95W. LOOKING AHEAD...THE GULF IS EXPECTED TO REMAIN FAIRLY TRANQUIL WITH DRY AIR AND STABILITY ALOFT...AND A SURFACE RIDGE ANCHORED OVER EASTERN PORTIONS THROUGH THE UPCOMING WEEKEND. THE RIDGE AXIS IS FORECAST ALONG 26N/27N WITH GENERALLY LIGHT E-SE WINDS SOUTH OF THE AXIS. CARIBBEAN SEA... AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER THE WESTERN CARIBBEAN NEAR 18N78W THAT IS PROVIDING PRIMARILY A MOIST AND DIFFLUENT AIRMASS W OF 80W AND A DRY AND SUBSIDENT AIRMASS FOR THE CENTRAL AND EASTERN CARIBBEAN THIS EVENING. WHILE THE SURFACE PRESSURE GRADIENT REMAINS RELATIVELY WEAK ACROSS THE WESTERN CARIBBEAN...THE UPPER LEVEL RIDGE AXIS EXTENDS WEST-NORTHWEST TO OVER THE YUCATAN PENINSULA AND IS GENERATING SCATTERED SHOWERS AND TSTMS NW OF A LINE FROM COASTAL NICARAGUA NEAR 12N84W TO JAMAICA NEAR 18N77W TO THE WINDWARD PASSAGE NEAR 20N74W. PORTIONS OF THIS CONVECTION ARE OCCURRING OVER INTERIOR AREAS OF CUBA...NICARAGUA...HONDURAS...AND THE YUCATAN PENINSULA THIS EVENING AND ARE LIKELY ENHANCED DUE TO THE UPPER LEVEL RIDGING AND ASSOCIATED DIFFLUENCE ALOFT. OVER THE EASTERN CARIBBEAN...DRY AIR ALOFT DOMINATES S OF 17N E OF 80W WITH VERY LITTLE SIGNIFICANT WEATHER OCCURRING THIS EVENING OVER THIS AREA. A TROPICAL WAVE CLIPS THE NE CARIBBEAN FROM 15N64W TO 22N61W AND IS PROVIDING FOCUS FOR ISOLATED SHOWERS FROM 15N-19N BETWEEN 60W-72W...INCLUDING PUERTO RICO...AND PORTIONS OF HISPANIOLA. THE TROPICAL WAVE IS FORECAST TO CONTINUE W-NW INCREASING PROBABILITY FOR PRECIPITATION OVER THE NEXT 24 TO 36 HOURS ACROSS THE GREATER ANTILLES AND ADJACENT COASTAL WATERS. HISPANIOLA... CURRENTLY A FEW ISOLATED SHOWERS AND TSTMS REMAIN ACROSS PORTIONS OF THE ISLAND AND THIS ACTIVITY IS EXPECTED TO GRADUALLY DIMINISH OVER THE NEXT FEW HOURS. WATER VAPOR IMAGERY INDICATES AN UPPER LEVEL ANTICYCLONE IS CENTERED WEST OF THE ISLAND NEAR 18N78W THAT IS PROVIDING THE CENTRAL AND EASTERN CARIBBEAN WITH RELATIVELY DRY AND STABLE AIR ALOFT. HOWEVER MOISTURE CONTINUES TO ADVECT SOUTHEASTWARD FROM THE SW NORTH ATLC ACROSS THE GREATER ANTILLES AND THE APPROACH OF A TROPICAL WAVE OVER THE NEXT 24 TO 48 HOURS WILL INCREASE MOISTURE AND CONVECTIVE ACTIVITY ACROSS HISPANIOLA ON FRIDAY AND SATURDAY. ATLANTIC OCEAN... A MIDDLE TO UPPER LEVEL LOW IS CENTERED OVER THE FLORIDA KEYS NEAR 25N82W THAT SUPPORTS A SURFACE TROUGH EXTENDING FROM 21N79W TO 25N78W WITH ISOLATED SHOWERS OCCURRING FROM 23N-28N BETWEEN 74W-78W. STRONGER CONVECTION IS LOCATED OVER INTERIOR PORTIONS OF CUBA E OF 80W THIS EVENING. FARTHER EAST...OVER THE REMAINDER OF THE SW NORTH ATLC...MID-LEVEL TROUGHING IS NOTED ON WATER VAPOR IMAGERY BETWEEN 60W-80W AND IS PROVIDING AN OVERALL UNSTABLE ENVIRONMENT. WITH A COLD FRONT EXTENDING ALONG 34N PROGRESSING OFF THE CAROLINA COAST AND THE ASSOCIATED SURFACE TROUGHING DIPPING SOUTHWARD TO 30N AND A TROPICAL WAVE ALONG 63W NE OF PUERTO RICO...WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS COVER THE AREA FROM 20N-32N BETWEEN 57W-74W. THE MORE INTENSE CONVECTION IS LOCATED GENERALLY N OF 30N IN AN AREA OF MAXIMUM MIDDLE TO UPPER LEVEL DIFFLUENCE SOUTHEAST OF THE COLD FRONT. ASIDE FROM THE TROPICAL WAVE PROGRESSING WESTWARD S OF 20N ALONG 46W...A SURFACE RIDGE INFLUENCES THE REMAINDER OF THE CENTRAL AND EASTERN ATLC ANCHORED BY A 1025 MB HIGH CENTERED NEAR 34N44W. THE ONLY COMPROMISE TO THE RIDGE IS A SURFACE TROUGH ANALYZED FROM 34N35W TO A 1020 MB LOW CENTERED NEAR 30N38W. THIS WEAK LOW REMAINS A SURFACE REFLECTION OF AN UPPER LEVEL LOW CENTERED NEAR 29N36W. ISOLATED SHOWERS ARE OCCURRING FROM 29N- 32N BETWEEN 35W-38W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN