000 AXNT20 KNHC 181804 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST WED NOV 18 2015 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 1745 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS WITHIN 450 NM SE OF THE WINDWARD ISLANDS WITH AXIS NEAR 53W...MOVING W AT APPROXIMATELY 15 TO 20 KT WITHIN THE LAST 24 HOURS. CIRA LAYER PRECIPITABLE WATER IMAGERY FROM SURFACE TO 850 MB AND THE METEOSAT SAHARAN AIR LAYER PRODUCT SHOW DRY AIR IN THE NORTHERN WAVE ENVIRONMENT THAT ALONG WITH STRONG DEEP LAYER WIND SHEAR HINDER DEEP CONVECTION. ISOLATED SHOWERS AND TSTMS ARE WITHIN 100 NM W OF THE WAVE AXIS S OF 10N AND FROM 9N TO 11N BETWEEN 46W AND 50W. MODEL GUIDANCE INDICATE THE WAVE WILL WEAKEN INTO A SURFACE TROUGH AND DISSIPATE EARLY THU PRIOR TO REACHING THE CARIBBEAN. A TROPICAL WAVE IS IN THE EASTERN CARIBBEAN WITH AXIS ALONG 67W...MOVING W AT APPROXIMATELY 15 TO 20 KT WITHIN THE LAST 24 HOURS. CIRA LAYER PRECIPITABLE WATER IMAGERY FROM SURFACE TO 850 MB SHOW THE WAVE IS EMBEDDED IN A MODERATE MOIST ENVIRONMENT. THE WAVE ITSELF IS ALSO EMBEDDED IN A STRONG DEEP LAYER WIND SHEAR ENVIRONMENT. HOWEVER, THE BASE OF AN UPPER LEVEL TROUGH EXTENDING FROM THE ATLC AND WEAK RIDGING N OF S AMERICA IS GENERATING DIFFLUENCE ALOFT THAT SUPPORT SCATTERED MODERATE CONVECTION AND ISOLATED TSTMS AHEAD OF THE WAVE...OVER THE CENTRAL CARIBBEAN...INCLUDING HISPANIOLA. SCATTERED SHOWERS AND TSTMS ARE OVER THE MONA PASSAGE AND MOVING INTO WESTERN PUERTO RICO AS THE TROUGH ALOFT MOVES E THROUGH THU. THE WAVE IS FORECAST TO WEAKEN INTO A SURFACE TROUGH AND DISSIPATE LATE TODAY. ...ITCZ/MONSOON TROUGH... THE ITCZ EXTENDS FROM 08N13W AND CONTINUE TO 04N30W TO 06N46W TO 05N52W. ISOLATED SHOWERS ARE WITHIN 30 NM EITHER SIDE OF THE AXIS BETWEEN 20W AND 30W. ...DISCUSSION... ...THE GULF OF MEXICO... A MIDDLE TO UPPER LEVEL TROUGH OVER THE CENTRAL UNITED STATES EXTENDS INTO THE WESTERN GULF OF MEXICO AND SUPPORTS A FRONTAL SYSTEM ANALYZED AS A COLD FRONT FROM SW ALABAMA NEAR 30N87W TO 25N92W TO A 1008 MB LOW OVER THE W BAY OF CAMPECHE NEAR 20N96W. AN UPPER LEVEL ANTICYCLONE ANCHORED OVER S MEXICO EXTENDS A RIDGE AXIS NE ALONG THE FLORIDA PENINSULA AND THE E CONUS. THIS IS GENERATING A DIFFLUENT ENVIRONMENT THAT ALONG WITH MOISTURE ADVECTION FROM THE CARIBBEAN SUPPORT SCATTERED MODERATE CONVECTION AND TSTMS WITHIN 230 NM E OF THE FRONT N OF 23N. SCATTERED SHOWERS ARE WITHIN 200 NM W OF THE FRONT. E OF FRONT TO 85W SE TO S WINDS OF 20 TO 25 KT ARE N OF 26N WITH SEAS TO 8 FT. W OF FRONT...FROM 25N TO 26.5N...WINDS ARE FROM THE N-NW OF 20 TO 25 KT WITH SEAS REACHING UP TO 9 FT. BY THU NIGHT...THE COLD FRONT WILL EXTEND FROM JACKSONVILLE FLORIDA SW TO THE CENTRAL GULF NEAR 25N90W. A PORTION OF THE FRONT WILL START TO WEAKEN AND STALL BY FRIDAY...THUS ACTING TO DIMINISH THE WINDS AND SEAS. SHOWERS ARE EXPECTED TO CONTINUE IN THE N-NE BASIN THROUGH THIS PERIOD. ...CARIBBEAN SEA... A TROPICAL WAVE IS IN THE EASTERN CARIBBEAN WITH AXIS ALONG 67W. THE WAVE IS EMBEDDED IN A MODERATE MOIST ENVIRONMENT AS WELL AS IN A STRONG DEEP LAYER WIND SHEAR ENVIRONMENT. SCATTERED MODERATE CONVECTION IS AHEAD OF THE OF THE WAVE OVER THE CENTRAL CARIBBEAN...INCLUDING HISPANIOLA. THIS CONVECTION IS BEING SUPPORTED BY AN UPPER LEVEL TROUGH EXTENDING FROM THE ATLC TO A BASE NE OF COSTA RICA AND DIFFLUENCE GENERATED BY A WEAK RIDGE N OF S AMERICA. SHOWERS AND TSTMS EXTEND TO THE MONA PASSAGE AND MOVE INTO WESTERN PUERTO RICO AS THE TROUGH ALOFT MOVES E THROUGH THU. THE WAVE IS FORECAST TO WEAKEN INTO A SURFACE TROUGH AND DISSIPATE LATE TODAY. TROUGHING ALOFT ALSO SUPPORTS A 1008 MB LOW OVER THE SW BASIN NEAR 11N81W WITH SURFACE TROUGH EXTENDING FROM 16N83W TO THE LOW TO 9N81W. THE LOW IS FORECAST TO STAY NEARLY STATIONARY DURING THE NEXT 24 HOURS...ASSOCIATED CONVECTION WILL PERSIST THROUGH THIS PERIOD. STRONG PRESSURE GRADIENT BETWEEN A RIDGE OVER THE W ATLC EXTENDING ACROSS THE NORTHERN CARIBBEAN AND THE LOW IN THE SW BASIN SUPPORT E WINDS OF 20 TO 25 KT FROM 13N TO 16N BETWEEN 72W AND 77W WITH SEAS TO 9 FT. WINDS AND SEAS ARE FORECAST TO DIMINISH BY FRIDAY MORNING. ...HISPANIOLA... SCATTERED MODERATE CONVECTION AND ISOLATED TSTMS ARE OVER THE CENTRAL CARIBBEAN...INCLUDING HISPANIOLA. THIS CONVECTION IS BEING SUPPORTED BY AN UPPER LEVEL TROUGH EXTENDING FROM THE ATLC TO A BASE NE OF COSTA RICA AND DIFFLUENCE GENERATED BY A WEAK RIDGE N OF S AMERICA. SHOWERS AND TSTMS EXTEND TO THE MONA PASSAGE. SHOWERS ACROSS THE ISLAND ARE FORECAST TO DIMINISH THU MORNING AS THE TROUGH ALOFT MOVES EAST WITHIN THIS PERIOD. ...ATLANTIC OCEAN... AN UPPER TROUGH EXTENDS FROM THE N CENTRAL ATLC SW TO A BASE IN THE CARIBBEAN...NE OF COSTA RICA. THIS TROUGH CONTINUE TO SUPPORT A FRONTAL SYSTEM THAT INVOLVES A DISSIPATING COLD FRONT FROM 32N48W TO 25N60W TO 25N70W AND A REINFORCING COLD FRONT FROM 32N48W TO 29N61W TO 30N70W. SCATTERED MODERATE CONVECTION AND ISOLATED TSTMS ARE WITHIN 300 NM S-SE OF THE DISSIPATING COLD FRONT. OVER THE SW N ATLC...A WARM FRONT EXTENDS FROM THE NORTHERN BAHAMAS NW TO A FRONTAL TRIPLE POINT OVER NW GEORGIA. OTHERWISE...RIDGING DOMINATES ELSEWHERE. FOR ADDITIONAL INFORMATION PLEASE VISIT WWW.HURRICANES.GOV/MARINE $$ NR