000 AXNT20 KNHC 172340 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST THU NOV 17 2011 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. ...TROPICAL WAVES... A TROPICAL WAVE EXTENDS FROM 18N49W TO 11N50W MOVING WNW AT 10-15 KT. THE WAVE IS EMBEDDED WITHIN A BROAD SURGE OF DEEP LAYER MOISTURE EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY. AN UPPER LEVEL TROUGH EXTENDING ALONG 56W IS PLACING DIFFLUENCE ALOFT OVER THE AREA BETWEEN 41W-53W...INCLUDING THE WAVE. THIS MAKES IT DIFFICULT TO DISCERN WHETHER CONVECTION NEAR THE WAVE IS ASSOCIATED DIRECTLY WITH THE WAVE OR THE UPPER LEVEL PATTERN. REGARDLESS OF THE INFLUENCE...SCATTERED MODERATE/ISOLATED CONVECTION IS FROM 14N-20N BETWEEN 44W-54W. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS W AFRICA ENTERING OVER ATLC WATERS NEAR 11N15W TO 6N19W. THE ITCZ CONTINUES FROM 6N19W ALONG 3N32W 6N45 PICKING UP ON THE OTHER SIDE OF THE TROPICAL WAVE ALONG 8N52W TO 10N61W. SCATTERED MODERATE/STRONG CONVECTION IS FROM 5N-8N BETWEEN 15W-17W. SIMILAR ACTIVITY IS FROM 6N-9N BETWEEN 36W-41W...AND N OF 8N BETWEEN 40W-49W. THIS LAST AREA OF CONVECTION LEADS INTO MORE WIDESPREAD ACTIVITY ASSOCIATED WITH AN UPPER LEVEL TROUGH OVER THE CENTRAL ATLC. ...DISCUSSION... THE GULF OF MEXICO... A WEAK AND FAST MOVING COLD FRONT IS ACROSS THE GULF MEXICO THIS EVENING EXTENDING FROM NEAR FORT MYERS FLORIDA AT 26N82W ALONG 23N90W 20N97W...AS OF 2100 UTC. ISOLATED SHOWERS ARE ALONG THE FRONT AXIS WITH SCATTERED SHOWERS/THUNDERSTORMS IN THE SRN BAY OF CAMPECHE AND ACROSS THE YUCATAN PENINSULA. SURFACE RIDGING IS BUILDING IN BEHIND THE FRONT AROUND A 1032 MB HIGH OVER SRN OKLAHOMA. THIS PRESSURE GRADIENT IS SUPPORTING 20-25 KT N-NE WINDS BEHIND THE FRONT. ALOFT...MAINLY WSWLY FLOW ALOFT COVERS THE BASIN ACCOMPANIED BY DRY AIR WHICH IS HELPING INHIBIT SHOWER ACTIVITY ALONG THE FRONTAL BOUNDARY AND KEEPING CONDITIONS FAIR ELSEWHERE. EXPECT THE FRONT TO CONTINUE TO PUSH SE OUT OF THE BASIN WITHIN THE NEXT 12-24 HOURS WITH SURFACE RIDGING BUILDING IN BEHIND IT. THE CARIBBEAN SEA... DRY AIR AND SUBSIDENCE COVER MUCH OF THE CARIBBEAN THIS EVENING AROUND AN UPPER LEVEL RIDGE CENTERED N OF ERN CUBA HELPING MAINTAIN MOSTLY FAIR CONDITIONS BASIN-WIDE. A FEW ISOLATED SHOWERS ARE NOTED OVER PORTIONS OF PUERTO RICO...HISPANIOLA...JAMAICA...AND ERN CUBA. SIMILAR ACTIVITY IS IN THE NW CARIBBEAN FROM 13N-20N BETWEEN 80W-84W. SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO OVER PANAMA...AND COSTA RICA ASSOCIATED WITH THE MONSOON TROUGH THAT EXTENDS ACROSS PANAMA TO NRN COLOMBIA. AT THE SURFACE...TRADEWIND FLOW OF 10-15 KTS COVERS MUCH OF THE BASIN. EXPECT SHOWER ACTIVITY TO REMAIN NEAR THE MONSOON TROUGH AND ACROSS CENTRAL AMERICA WITH FAIR CONDITIONS ELSEWHERE. THE FRONT CURRENTLY IN THE GULF OF MEXICO IS EXPECTED TO DISSIPATE BEFORE REACHING THE NW CARIBBEAN. THE ATLANTIC OCEAN... A BROAD UPPER LEVEL TROUGH EXTENDS DOWN THE ERN UNITED STATES SEABOARD SUPPORTING A COLD FRONT THAT ENTERS THE DISCUSSION AREA NEAR 32N78W TO NRN FLORIDA NEAR 29N81W AND INTO THE GULF OF MEXICO. POSSIBLE ISOLATED SHOWERS ARE ALONG THE FRONT AXIS. THE REMAINDER OF THE W ATLC IS EXPERIENCING MOSTLY FAIR WEATHER DUE TO DRY AIR ALOFT AROUND AN UPPER LEVEL RIDGE EXTENDING FROM ERN CUBA TO NEAR 33N61W. FARTHER E...A SHARP UPPER TROUGH EXTENDS ALONG 55W. UPPER LEVEL DIFFLUENCE AROUND THE E SIDE OF THE TROUGH IS HELPING SUPPORT A BROAD AREA OF SHOWERS/THUNDERSTORMS FROM N OF THE ITCZ TO 30N BETWEEN 40W-55W. SOME OF THE ACTIVITY IS ALSO ENHANCED BY A TROPICAL WAVE NEAR 50W...AND A SURFACE TROUGH ALONG 29N49W TO 22N52W. IT APPEARS THAT A SURFACE LOW MAY BE FORMING ALONG THE SURFACE TROUGH AXIS. THE ERN ATLC IS COVERED BY AN UPPER LEVEL RIDGE WITH AXIS ALONG 38W SUPPORTING A 1026 MB HIGH NEAR 35N41W. A BROAD UPPER LEVEL TROUGH IS ACROSS THE FAR ERN ATLC WITH AXIS EXTENDING OVER NW AFRICA CAUSING NO SIGNIFICANT WEATHER WITHIN THE DISCUSSION AREA. EXPECT THE AREA OF DISTURBED WEATHER IN THE CENTRAL ATLC TO BE THE MAIN FOCUS FOR THE NEXT SEVERAL DAYS AS SHOWER/POSSIBLE THUNDERSTORM ACTIVITY CONTINUES. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON