000 AXNT20 KNHC 202340 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST WED NOV 20 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 STORM MELISSA IS CENTERED NEAR 37.2N 44.9W AT 20/2100 UTC OR ABOUT 850 NM W OF THE AZORES MOVING ENE AT 26 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 988 MB. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. WIDELY SCATTERED MODERATE CONVECTION IS FROM 36N-40N BETWEEN 44W-49W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 08N13W TO 06N18W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 06N18W TO 03N25W TO 05N31W TO 04N43W. A SURFACE TROUGH IS ANALYZED ON THE WESTERN EXTENT OF THE AXIS FROM 04N44W TO 11N45W. SCATTERED MODERATE CONVECTION IS FROM 03N-15N BETWEEN 12W-23W...FROM 01N-06N BETWEEN 23W-31W...AND WITHIN 150 NM EITHER SIDE OF A LINE FROM 02N31W TO 07N45W. ...DISCUSSION... GULF OF MEXICO... SOUTHWEST TO WESTERLY FLOW IS NOTED ON WATER VAPOR IMAGERY OVER THE GULF BASIN THIS EVENING EAST OF AN APPROACHING MIDDLE TO UPPER LEVEL TROUGH WITH AXIS EXTENDING FROM OVER SOUTHERN TEXAS NEAR 28N98W SW TO 22N106W. AS OF 20/2100 UTC...A STATIONARY FRONT EXTENDS ACROSS THE SOUTHERN FLORIDA PENINSULA INTO THE GULF NEAR 27N82W TO 26N87W WHERE THE FRONT WEAKENS SOMEWHAT OVER THE CENTRAL GULF AND RESUMES A MORE NOTICEABLE PRESENCE OVER THE NW GULF FROM 26N93W TO THE TEXAS COAST NEAR 29N96W. WHILE THE SOUTHWESTERLY FLOW IS ADVECTING MOISTURE OVER MUCH OF THE BASIN...THE FRONTAL BOUNDARY IS PROVIDING LOW-LEVEL MOISTURE CONVERGENCE TO GENERATE A COUPLE SPECIFIC AREAS OF CONVECTION THIS EVENING. ONE AREA OF SCATTERED SHOWERS AND TSTMS IS OCCURRING ACROSS THE WESTERN GULF IN THE VICINITY OF THE FRONT FROM 25N-29N BETWEEN 91W-95W...AND THE OTHER AREA OF SCATTERED SHOWERS AND ISOLATED TSTMS IS OCCURRING PRIMARILY SOUTH OF THE STATIONARY FRONT AND EAST OF A SURFACE TROUGH AXIS ANALYZED FROM THE FRONT NEAR 27N86W SOUTHWARD TO THE NE YUCATAN PENINSULA NEAR 21N88W ACROSS THE SE GULF WATERS N OF 24N. E-SE WINDS ARE EXPECTED TO PERSIST FROM THIS EVENING THROUGH LATE FRIDAY WHEN THE NEXT COLD FRONT IS EXPECTED TO EMERGE OFF THE TEXAS AND LOUISIANA COASTS LATE FRIDAY INTO EARLY SATURDAY WITH N-NE WINDS SPREADING ACROSS THE BASIN THROUGH THE UPCOMING WEEKEND. CARIBBEAN SEA... AN UPPER LEVEL ANTICYCLONE IS CENTERED OVER THE WESTERN CARIBBEAN NEAR 14N78W AND IS PROVIDING MUCH OF THE BASIN E OF 80W WITH DRY NORTHWEST TO WESTERLY FLOW ALOFT. IN ADDITION...A BROAD UPPER LEVEL TROUGH IS NOTED ON WATER VAPOR IMAGERY E OF 70W BUT IS HOWEVER REMAINING VERY DRY AND STABLE ALOFT. WITH OVERALL STABILITY ALOFT DOMINATING...CONDITIONS AT THE SURFACE REMAIN FAIRLY TRANQUIL WITH ONLY A FEW AREA OF ISOLATED LOW- TOPPED SHOWERS OCCURRING THIS EVENING IN THE VICINITY OF WEAK SURFACE TROUGHS. ONE SURFACE TROUGH IS ANALYZED FROM 15N77W TO THE WINDWARD PASSAGE NEAR 20N74W THAT IS PROVIDING FOCUS FOR ISOLATED SHOWERS FROM 13N-20N BETWEEN 69W-78W AND THE OTHER SURFACE TROUGH EXTENDS FROM 11N80W TO 15N84W WITH ISOLATED SHOWERS AND TSTMS OCCURRING MOSTLY INLAND ACROSS NICARAGUA AND EASTERN HONDURAS FROM 12N-16N BETWEEN 83W-86W. OTHERWISE... ANOTHER AREA OF ISOLATED SHOWERS IS OCCURRING WITHIN 90 NM EITHER SIDE OF A LINE FROM 18N62W TO 15N68W. FINALLY...A FEW ISOLATED SHOWERS AND TSTMS ARE NOTED S OF 10N...INCLUDING INLAND PORTIONS OF PANAMA DUE TO THE CLOSE PROXIMITY OF THE MONSOON TROUGH ANALYZED ALONG 09N BETWEEN NORTHERN COLOMBIA AND EXTREME SOUTHERN COSTA RICA. TRADES ARE FORECAST TO REMAIN 20 KT OR LESS THROUGH THE REMAINDER OF THE WEEK INTO THE UPCOMING WEEKEND. ...HISPANIOLA... CURRENTLY A FEW ISOLATED LOW-TOPPED SHOWERS ARE OCCURRING OVER PORTIONS OF HISPANIOLA AND THE SOUTHERN AND WESTERN COASTAL WATERS STRETCHING INTO THE CENTRAL CARIBBEAN SEA. WHILE THIS LOW- LEVEL MOISTURE CONTINUES TO LINGER...ALOFT MIDDLE TO UPPER LEVEL NORTHWESTERLY FLOW IS PROVIDING A VERY DRY AND STABLE ENVIRONMENT LIMITING OVERALL DEEPER CONVECTION. A WEAK PRESSURE GRADIENT REMAINS OVER THE ISLAND AND GIVEN THE STABILITY...FAIR CONDITIONS AND TRANQUIL WEATHER IS EXPECTED OVER THE NEXT FEW DAYS WITH THE EXCEPTION OF A FEW ONSHORE-MOVING PASSING ISOLATED SHOWERS. ATLANTIC OCEAN... A DEEP LAYERED LOW NOTED OFF THE COAST OF NOVA SCOTIA NEAR 46N57W SUPPORTS A COLD FRONT ANALYZED FROM 32N58W SW TO 29N67W WHERE IT BECOMES STATIONARY WESTWARD TO THE FLORIDA PENINSULA NEAR 27N80W. WHILE THE MIDDLE TO UPPER LEVEL DYNAMICS ARE FOUND WELL NORTH OF THE DISCUSSION AREA...ISOLATED SHOWERS AND TSTMS ARE OCCURRING WITHIN 90 NM EITHER SIDE OF THE FRONTAL BOUNDARY. THE FRONTAL BOUNDARY IS EXPECTED TO REMAIN STATIONARY AND GRADUALLY WEAKEN THROUGH LATE THURSDAY AS SURFACE RIDGING BUILDS IN ACROSS THE SW NORTH ATLC FROM THE NORTH. ACROSS THE REMAINDER OF THE SW NORTH ATLC...A WEAK SURFACE RIDGE REMAINS TO THE SE OF THE FRONT FOCUSED ON A 1018 MB HIGH CENTERED NEAR 26N64W. FARTHER EAST...THE MIDDLE TO UPPER LEVEL LOW ASSOCIATED WITH TROPICAL STORM MELISSA IS CENTERED NEAR 37N45W AND EXTENDS A TROUGH AXIS SOUTHWARD TO 18N60W. WHILE MELISSA CONTINUES TO RACE TO THE NORTHEAST...SURFACE TROUGHING RESULTS OVER THE CENTRAL ATLC FROM 18N53W TO 24N47W TO 29N45W AND PROVIDES FOCUS FOR LOW- LEVEL MOISTURE CONVERGENCE. THIS CONVERGENCE ALONG WITH A LARGE AREA OF UPPER LEVEL DIFFLUENCE EAST OF THE UPPER LEVEL TROUGH IS GENERATING SCATTERED SHOWERS AND TSTMS WITHIN 180 NM EITHER SIDE OF A LINE FROM 16N50W TO 32N38W. FINALLY...THE REMAINDER OF THE EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1023 MB HIGH CENTERED NEAR 32N27W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN