000 AXNT20 KNHC 151756 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU AUG 15 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. ...SPECIAL FEATURES... TROPICAL STORM ERIN IS CENTERED NEAR 14.4N 26.5W AT 15/1500 UTC OR ABOUT 100 NM WSW OF BRAVA IN THE CAPE VERDE ISLANDS MOVING W- NW AT 13 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUST TO 45 KT. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 12N- 15N BETWEEN 25W-28W. SEE LATEST FORECAST/ADVISORY UNDER AWIPS/ WMO HEADERS MIATCMAT5/WTNT25 KNHC FOR MORE DETAILS. TROPICAL WAVE EXTENDS FROM 18N88W TO 25N86W MOVING W-NW AT 10 KT. A 1010 MB LOW IS CENTERED ALONG THE YUCATAN PENINSULA COAST NEAR 19N88W AND THE SYSTEM REMAINS ON THE WESTERN PERIPHERY OF AN UPPER LEVEL ANTCYCLONIC CIRCULATION CENTERED OVER WESTERN CUBA. LOW-LEVEL MOISTURE CONVERGENCE EAST OF THE TROPICAL WAVE AXIS AND A FAVORABLE UPPER LEVEL DIFFLUENT ENVIRONMENT OVER THE NW CARIBBEAN IS GENERATING SCATTERED MODERATE CONVECTION FROM 16N-26N BETWEEN 84W-89W. AS THE WAVE TRACKS GENERALLY WESTWARD INTO THE WESTERN GULF OF MEXICO THROUGH THE WEEKEND...NUMEROUS SHOWERS AND TSTMS ARE EXPECTED TO IMPACT THE YUCATAN PENINSULA AND SW GULF OVER THE NEXT 24 TO 48 HOURS. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 12N44W TO 19N44W MOVING W AT 10-15 KT. THE WAVE REMAINS EMBEDDED WITHIN THE MONSOON TROUGH AND IS LARGELY CONVECTION FREE DUE TO THE SAHARAN AIR LAYER ACROSS THE CENTRAL ATLC. TROPICAL WAVE EXTENDS FROM 12N57W TO 20N57W MOVING W AT 10-15 KT. THE WAVE IS LIKELY ENERGY THAT EMERGED OFF THE AFRICAN COAST DAYS AGO AND MERGED WITH MID-LATITUDE ENERGY DIVING SOUTHWESTWARD ACROSS THE CENTRAL ATLC BETWEEN 35W-55W IN THE PAST 24 TO 48 HOURS. WHILE THE WAVE IS MOVING WITHIN A STRONG SAHARAN AIR LAYER...NO SIGNIFICANT DEEP CONVECTION IS NOTED IN THE VICINITY OF THE WAVE AXIS HOWEVER ISOLATED LOW-TOPPED SHOWERS ARE POSSIBLE FROM 13N-22N BETWEEN 53W-61W. THIS ACTIVITY WILL BE MOVING ACROSS THE LESSER ANTILLES AND EASTERN CARIBBEAN THROUGH THE WEEKEND. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM 12N28W TO 11N31W TO 13N42W TO 09N52W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 09N52W TO 07N59W. SCATTERED MODERATE CONVECTION IS FROM 07N-12N BETWEEN 23W-47W. ISOLATED MODERATE CONVECTION IS WITHIN 75 NM EITHER SIDE OF A LINE FROM 12N48W TO 09N57W. ...DISCUSSION... GULF OF MEXICO... A NARROW MIDDLE TO UPPER LEVEL LOW IS CENTERED NEAR 24N87W OVER THE CENTRAL GULF AND REMAINS IN BETWEEN TWO UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERS...ONE OVER THE NW GULF NEAR 27N94W...AND THE OTHER CENTERED OVER THE NW CARIBBEAN SEA NEAR 20N84W. WATER VAPOR IMAGERY INDICATES PLENTY OF MIDDLE TO UPPER LEVEL DIFFLUENCE ON THE EASTERN PERIPHERY OF THE TROUGHING AND THIS DIFFLUENCE ALONG WITH LOW-LEVEL MOISTURE CONVERGENCE ASSOCIATED WITH A TROPICAL WAVE ALONG 87W IS GENERATING SCATTERED SHOWERS AND WIDELY SCATTERED TSTMS S OF 27N BETWEEN 80W-88W...INCLUDING THE SOUTHERN FLORIDA PENINSULA...AND FLORIDA STRAITS. TO THE NORTH...WATER VAPOR IMAGERY ALSO INDICATES BROADER MIDDLE TO UPPER LEVEL LONGWAVE TROUGHING THAT SUPPORTS A WEAK STATIONARY FRONT ANALYZED FROM SOUTHERN GEORGIA NEAR 32N83W W-SW TO THE TEXAS GULF COAST NEAR 28N97W. A PRE-FRONTAL SURFACE TROUGH IS ALSO NOTED FROM THE MISSISSIPPI RIVER DELTA NEAR 29N89W TO 28N94W. BOTH BOUNDARIES ARE PROVIDING FOCUS FOR WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS N OF 27N W OF 84W. THE REMAINDER OF THE GULF BASIN IS UNDER THE INFLUENCE OF A VERY WEAK SURFACE RIDGE EXTENDING FROM A 1015 MB HIGH CENTERED NEAR 27N94W TO A 1017 MB HIGH CENTERED INLAND OVER EAST-CENTRAL MEXICO NEAR 20N98W. THE TROPICAL WAVE AND ASSOCIATED LOW PRESSURE AREA IS EXPECTED TO MOVE W-NW THROUGH THE WEEKEND WITH GENERAL SURFACE TROUGHING EXTENDING FROM THE COASTAL GULF PLAINS TO THE SW GULF. CARIBBEAN SEA... AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER THE NW CARIBBEAN NEAR 19N84W THAT IS PROVIDING AN OVERALL DIFFLUENT ENVIRONMENT IN THE VICINITY OF A TROPICAL WAVE AND ASSOCIATED SURFACE LOW LOCATED ALONG THE YUCATAN PENINSULA COAST NEAR 19N88W. LOW-LEVEL MOISTURE CONVERGENCE EAST OF THE TROPICAL WAVE AND THE FAVORABLE UPPER LEVEL DIFFLUENCE IS GENERATING SCATTERED SHOWERS AND TSTMS GENERALLY N OF 16N W OF 79W. THE STRONGEST OF THIS ACTIVITY IS LOCATED WITHIN 180 NM OF THE NE QUADRANT OF THE SURFACE LOW. THE 1010 MB LOW IS EXPECTED TO CONTINUE MOVING W-NW ACROSS INLAND PORTIONS OF THE YUCATAN PENINSULA OVER THE NEXT 12 TO 24 HOURS AND EMERGE INTO THE WATERS OF THE SW GULF OF MEXICO. FARTHER SE...WATER VAPOR IMAGERY INDICATES NORTHEASTERLY FLOW ALOFT WEST OF A LINE FROM 18N69W TO 09N76W THAT IS PROVIDING AN OVERALL DRY AND SUBSIDENT ATMOSPHERE FOR THE CENTRAL CARIBBEAN. SKIES CURRENTLY ARE CLEAR WITH ONLY A FEW PASSING LOW-LEVEL CUMULUS OR HIGH-LEVEL CIRRUS CLOUDS. EAST OF THE AFOREMENTIONED LINE...FLOW ALOFT SHIFTS MORE SOUTHERLY AND IS DRY ALOFT. THE EASTERN CARIBBEAN AND LESSER ANTILLES LIE WITHIN AN AREA OF E-NE WINDS ON THE WESTERN PERIPHERY OF AN APPROACHING TROPICAL WAVE ALONG 57W. LOW-LEVEL MOISTURE WILL BE ON THE INCREASE FOR THE ISLANDS AND EASTERN CARIBBEAN OVER THE NEXT 24 TO 36 HOURS... HOWEVER WILL BE GENERALLY LIMITED TO LOW-TOPPED SHOWERS AS ANY SIGNIFICANT DEEP CONVECTION WILL LIKELY BE SUPPRESSED DUE TO THE PRESENCE OF A SAHARAN AIR LAYER. HISPANIOLA... CURRENTLY SKIES REMAIN CLEAR WITH FAIR CONDITIONS THIS AFTERNOON AS DRIER AIR AND SUBSIDENCE ALOFT CONTINUES TO MOVE IN FROM THE EAST AS NOTED ON WATER VAPOR IMAGERY. THE DRY AIR ALOFT STRETCHES WELL INTO THE CENTRAL ATLC...HOWEVER...THE APPROACH OF A TROPICAL WAVE ALONG 57W WILL INCREASE MOISTURE AND CLOUDINESS ACROSS THE REGION OVER THE UPCOMING WEEKEND WITH THE A HIGHER POSSIBILITY OF SHOWER AND THUNDERSTORM ACTIVITY. ATLANTIC OCEAN... AN UPPER LEVEL RIDGE IS NOTED ON WATER VAPOR IMAGERY GENERALLY S OF 30N W OF 73W AND IS PROVIDING AN UPPER LEVEL DIFFLUENT ENVIRONMENT OVER THE SW NORTH ATLC THIS AFTERNOON. LOW-LEVEL MOISTURE CONTINUES TO ADVECT NORTHEASTWARD AWAY FROM THE TROPICAL WAVE IMPACTING THE YUCATAN PENINUSLA AND ALONG WITH THE DIFFLUENCE IS GENERATING SCATTERED SHOWERS AND TSTMS FROM 23N- 28N BETWEEN 74W TO BEYOND 81W AND INTO THE SE GULF OF MEXICO. TO THE NORTH OF THIS AREA...A STATIONARY FRONT IS ANALYZED ALONG 32N-33N AND IS PROVIDING FOR ISOLATED SHOWERS AND TSTMS OFFSHORE OF THE CAROLINAS N OF 31N BETWEEN 74W-81W. OVER THE REMAINDER OF THE SW NORTH ATLC...A MIDDLE TO UPPER LEVEL LOW IS CENTERED NEAR 30N65W AND SUPPORTS A SURFACE TROUGH ANALYZED FROM 34N66W TO 28N69W. LOW-LEVEL CONVERGENCE IN THE VICINITY OF THE SURFACE TROUGH ALONG WITH UPPER LEVEL LIFT PROVIDING BY THE UPPER LEVEL LOW IS GENERATING SCATTERED SHOWERS AND TSTMS FROM 23N-33N BETWEEN 60W-72W. FINALLY...THE CENTRAL AND EASTERN CARIBBEAN ARE UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1026 MB HIGH CENTERED NORTH OF THE DISCUSSION AREA NEAR 35N45W. 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