000 AXNT20 KNHC 132317 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST THU NOV 13 2008 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...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2245 UTC. ...THE ITCZ... THE ITCZ AXIS IS ANALYZED ALONG 11N13W 7N22W 8N36W 9N49W 7N60W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 3N-7N BETWEEN 13W-18W. SCATTERED MODERATE CONVECTION IS WITHIN 90 NM EITHER SIDE OF THE ITCZ AXIS BETWEEN 29W-34W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 7N-12N BETWEEN 36W-53W. ...DISCUSSION... GULF OF MEXICO... MOIST SOUTHWESTERLY FLOW ALOFT IS OVER THE NW GULF IN ADVANCE OF A DEEP LAYER TROUGH THAT EXTENDS FROM THE PLAINS OF THE CONUS TO CENTRAL MEXICO. ALSO...STRONG UPPER LEVEL DIVERGENCE IS AFFECTING PORTIONS OF THE NW GULF TO THE S OF A MID/UPPER-LEVEL WIND SPEED MAXIMUM PRESENT OVER SE TEXAS. AS A RESULT...NUMEROUS SHOWERS AND THUNDERSTORMS ARE AFFECTING THE NW GULF TO THE W OF A LINE FROM 23N98W TO 29N93W...INCLUDING COASTAL AREAS OF SE TEXAS. THIS ACTIVITY IS BEING ENHANCED BY LOW LEVEL CONVERGENCE IN THE VICINITY OF A SURFACE STATIONARY FRONT THAT EXTENDS FROM 22N98W TO A 1009 MB SURFACE LOW E OF BROWNSVILLE TEXAS NEAR 27N96W TO 28N89W. TO THE E OF THE SURFACE STATIONARY FRONT...A SURFACE COLD FRONT EXTENDS FROM 28N89W TO 29N87W TO A 1013 MB SURFACE LOW IN SOUTH CENTRAL ALABAMA NEAR 31N87W...WITH A SURFACE STATIONARY FRONT EXTENDING TO THE NE OF THIS LOW FROM 31N87W TO 32N84W TO NE OF THE DISCUSSION AREA. THESE FEATURES ARE SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS OVER THE NE GULF N OF 28N E OF 86W...AFFECTING PORTIONS OF THE FLORIDA PANHANDLE. FARTHER TO THE S...VISIBLE SATELLITE IMAGERY INDICATES LOW-LEVEL CYCLONIC CIRCULATION AROUND A SURFACE TROUGH EXTENDING FROM 28N85W TO 26N85W TO 23N85W. ISOLATED SHOWERS ARE OCCURRING WITHIN 120 NM EITHER SIDE OF THIS SURFACE TROUGH. HOWEVER...DEEP LAYER DRY AIR IS LIMITING DEEP CONVECTION ACROSS MUCH OF THE S AND E GULF. CARIBBEAN SEA... AN UPPER RIDGE IS AFFECTING THE W CARIBBEAN...WITH THE UPPER RIDGE AXIS EXTENDING FROM W CUBA NEAR 22N79W TO E COSTA RICA NEAR 10N83W. SUBSIDENCE AND DEEP LAYER DRY AIR IN THE VICINITY OF THIS UPPER RIDGE ARE BRINGING FAIR WEATHER CONDITIONS TO MUCH OF THE W CARIBBEAN. OVER THE E CARIBBEAN...AN UPPER LEVEL TROUGH IS PRESENT...WHICH IS ANCHORED BY AN UPPER LOW N OF THE LEEWARD ISLANDS NEAR 19N63W. WEAK INSTABILITY...COMBINED WITH GREATER DEEP MOISTURE OVER THE E CARIBBEAN...IS SUPPORTING SCATTERED SHOWERS E OF 67W...INCLUDING PORTIONS OF THE LESSER ANTILLES. THIS ACTIVITY IS FURTHER BEING ENHANCED BY A SURFACE TROUGH THAT EXTENDS FROM SE OF PUERTO RICO NEAR 17N66W TO 19N65W NORTHEASTWARD TO THE SW ATLC. ALSO...SCATTERED SHOWERS AND THUNDERSTORMS ARE OCCURRING OVER PORTIONS OF N PANAMA... N COLOMBIA...AND N VENEZUELA...AS WELL AS THE ADJACENT CARIBBEAN SEA. THIS CONVECTION IS BEING ENHANCED BY GREATER INSTABILITY OVER HIGHER TERRAIN. ATLANTIC OCEAN... AN UPPER RIDGE AXIS IS OVER THE W ATLC EXTENDING FROM W CUBA NEAR 22N79W TO 29N75W TO 31N74W TO NE OF THE DISCUSSION AREA. DEEP LAYER DRY AIR IS INHIBITING DEEP CONVECTION ACROSS MUCH OF THE W ATLC. FARTHER TO THE E...THE AXIS OF A DEEP LAYER TROUGH EXTENDS FROM AN UPPER LOW N OF THE LEEWARD ISLANDS NEAR 19N63W TO 26N62W TO 29N59W. THIS DEEP LAYER TROUGH IS ACCOMPANIED BY A SURFACE TROUGH THAT EXTENDS FROM 26N62W TO 22N64W TO 17N66W. LOW LEVEL CONVERGENCE NEAR THIS SURFACE TROUGH...COMBINED WITH UPPER LEVEL DIFFLUENCE...IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS FROM 11N-24N BETWEEN 56W-64W...INCLUDING PORTIONS OF THE LESSER ANTILLES. ALTHOUGH UPPER-LEVEL WINDS ARE ONLY MARGINALLY FAVORABLE...SOME ADDITIONAL DEVELOPMENT OF THIS SYSTEM IS POSSIBLE OVER THE NEXT COUPLE OF DAYS AS IT MOVES WESTWARD AT 10 TO 15 KT. ALSO...A COLD FRONT EXTENDS FROM 31N55W TO NE OF THE DISCUSSION AREA...WITH DEEP LAYER DRY AIR INHIBITING DEEP CONVECTION NEAR THE COLD FRONT S OF 32N. FARTHER TO THE E...AN UPPER TROUGH IS N OF 19N BETWEEN 18W-39W. THIS UPPER TROUGH IS SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM 31N36W TO 28N36W TO 24N35W. ISOLATED SHOWERS WITHIN 60 NM EITHER SIDE OF THE SURFACE TROUGH N OF 27N. OVER THE TROPICAL ATLC...AN UPPER HIGH IS CENTERED NEAR 2N47W...AND AN UPPER RIDGE IS S OF 8N BETWEEN 11W-20W. UPPER LEVEL DIVERGENCE OVER THE N PERIPHERY OF EACH OF THESE FEATURES IS ENHANCING THE CONVECTION NEAR THE ITCZ. $$ COHEN