000 AXNT20 KNHC 190544 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT SUN OCT 19 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...SPECIAL FEATURES... NONE. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 38W S OF 18N MOVING W 10-15 KT. SATELLITE IMAGERY DEPICTS INVERTED-V SIGNATURE IN CLOUD COVERAGE...ALONG WITH COUNTERCLOCKWISE MOTION OF CLOUD ELEMENTS IN THE VICINITY OF THE WAVE AXIS. COMPUTER MODEL GUIDANCE AND CIMSS WAVETRAK PRODUCT CONFIRM PRESENCE OF LOW LEVEL COUNTERCLOCKWISE CIRCULATION NEAR WAVE AXIS. THIS WAVE ALSO COINCIDES WITH A BROAD WESTWARD-MOVING DEEP LAYER MOISTURE SURGE BASED ON TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. ISOLATED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF WAVE AXIS N OF 13N. TROPICAL WAVE IS ALONG 56W/57W S OF 16N MOVING W NEAR 10 KT. WAVE IS NOT PARTICULARLY WELL-DEFINED BASED ON SATELLITE IMAGERY...THOUGH IT DOES COINCIDE WITH A NORTH-TO-SOUTH DEEP LAYER MOISTURE MAXIMUM. ISOLATED MODERATE CONVECTION IS WITHIN 90 NM W OF WAVE AXIS FROM 9N-11N...WHICH IS BEING ENHANCED BY LOW LEVEL CONVERGENCE NEAR THE ITCZ. ...THE ITCZ... ITCZ AXIS IS ANALYZED ALONG 7N12W 9N32W 9N45W 10N54W 9N61W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE ALONG FROM 3N-11N BETWEEN 11W-22W...AFFECTING W PORTIONS OF SENEGAL...GAMBIA...AND GUINEA-BISSAU. ISOLATED MODERATE CONVECTION IS FROM 8N-14N BETWEEN 30W-34W. ISOLATED MODERATE CONVECTION IS ALSO FROM 9N-12N BETWEEN 59W-61W...AFFECTING THE SOUTHERN WINDWARD ISLANDS. ...DISCUSSION... GULF OF MEXICO... AN UPPER TROUGH OVER THE E CONUS EXTENDS SOUTHWARD INTO THE GULF...WITH SW TO W FLOW ALOFT COVERING MUCH OF THE GULF. THIS TROUGH CONTINUES TO SUPPORT A COLD FRONT THAT IS DRAPED ACROSS THE CENTRAL AND E GULF...EXTENDING FROM THE WEST CENTRAL FLORIDA PENINSULA NEAR 27N82W TO 25N87W TO 22N91W. THIS FRONT IS STATIONARY FROM 22N91W SOUTHWARD INTO THE BAY OF CAMPECHE NEAR 19N92W. MID/UPPER-LEVEL MOISTURE AND ATMOSPHERIC LIFT EMBEDDED WITHIN SW FLOW ALOFT ARE JUXTAPOSED WITH THE SURFACE FRONT...RESULTING IN CLOUDINESS AND ISOLATED SHOWERS WITHIN 90 NM EITHER SIDE OF THE COLD FRONT N OF 23N. FURTHER TO THE NW...SUBSIDENCE AND DRY AIR IN NW FLOW ALOFT ARE RESULTING IN FAIR WEATHER ACROSS MUCH OF THE NW GULF. ALSO...AN UPPER HIGH IS CENTERED W OF THE YUCATAN PENINSULA NEAR 17N92W. MOISTURE EMBEDDED IN DIFFLUENT FLOW ALOFT SE OF THIS HIGH IS SUPPORTING SCATTERED MODERATE CONVECTION FROM 16N-20N BETWEEN 89W-92W... AFFECTING THE W YUCATAN PENINSULA AND ADJACENT WATERS OF THE BAY OF CAMPECHE. THIS CONVECTION IS BEING FURTHER ENHANCED BY LOW LEVEL CONVERGENCE NEAR THE AFOREMENTIONED STATIONARY FRONT. CARIBBEAN SEA... AN UPPER RIDGE EXTENDS FROM AN UPPER HIGH NEAR 20N57W TO N COLOMBIA...AND A WEAK UPPER TROUGH IS PRESENT OVER THE NW CARIBBEAN. ALSO...A SURFACE TROUGH EXTENDS FROM W HONDURAS NEAR 16N88W TO A 1009 MB SURFACE LOW NEAR 18N87W TO 16N81W TO A 1011 MB SURFACE LOW LOCATED S OF JAMAICA NEAR 17N77W. LOW LEVEL CONVERGENCE FROM THE SURFACE TROUGH...COMBINED WITH DIVERGENCE ASSOCIATED WITH AN UPPER HIGH NEAR 19N82W AND AMPLE MOISTURE OVER THE W CARIBBEAN...IS SUPPORTING SCATTERED MODERATE/ISOLATED STRONG CONVECTION WITHIN 150 NM EITHER SIDE OF THE SURFACE TROUGH W OF 84W. FURTHER TO THE E...CONVECTIVE COVERAGE IS LIMITED AS A RESULT OF DRY AIR EMBEDDED WITHIN CONFLUENT SW FLOW ALOFT...WITH ISOLATED MODERATE CONVECTION OCCURRING WITH 210 NM EITHER SIDE OF THE SURFACE TROUGH BETWEEN 78W-84W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION OVER PORTIONS OF COSTA RICA...PANAMA...AND NW COLOMBIA IS IMPACTING THE NEARBY SW CARIBBEAN WATERS. THIS CONVECTION IS BEING ENHANCED BY A 1008 MB SURFACE LOW OVER THE VENEZUELA-COLOMBIA BORDER NEAR 9N73W AND GREATER INSTABILITY OVER HIGHER TERRAIN. ATLANTIC OCEAN... AN UPPER TROUGH OVER THE E CONUS IS BRINGING SW FLOW ALOFT TO THE W ATLC...AND IS SUPPORTING A SURFACE COLD FRONT THAT EXTENDS FROM A 1010 MB SURFACE LOW NEAR 34N75W TO 29N78W TO THE E CENTRAL FLORIDA PENINSULA NEAR 28N80W. DRY AIR WRAPPING AROUND THE BASE OF THE UPPER TROUGH...COMBINED WITH SUBSIDENCE IN NW FLOW ALOFT W OF THE UPPER TROUGH AXIS...IS LIMITING CONVECTION OVER THE W ATLC. FURTHER TO THE E...A SURFACE TROUGH EXTENDS FROM 31N51W TO 28N55W TO 26N59W. HOWEVER...MAINLY DRY AND STABLE CONDITIONS AROUND AN UPPER HIGH CENTERED NEAR 20N57W ARE PREVENTING CONVECTIVE DEVELOPMENT WITH THE SURFACE TROUGH. FURTHER TO THE E...A 1026 MB SURFACE HIGH IS CENTERED NEAR 30N32W...AND A SURFACE RIDGE EXTENDS FROM THIS HIGH TO THE S NEAR 13N30W... WHERE SUBSIDENCE AND STABLE CONDITIONS PREDOMINATE OVER MUCH OF THE E ATLC. ALSO...AN UPPER TROUGH IS PRESENT OVER THE NE ATLC N OF 18N AND E OF 19W...WITH DEEP LAYER DRY AIR EMBEDDED WITHIN THIS TROUGH. OVER THE TROPICAL ATLC...AN UPPER RIDGE EXTENDS ALONG 12N BETWEEN W AFRICA AND 29W. THE W PORTION OF THIS RIDGE IS DRAWN NORTHWESTWARD TO NEAR 23N34W DUE THE COUNTERCLOCKWISE CIRCULATION AROUND A COMPACT N-TO-S UPPER TROUGH EXTENDING FROM 24N46W TO AN UPPER LOW NEAR 17N45W TO 11N46W. DEEP LAYER DRY AIR EMBEDDED WITHIN THESE FEATURES IS GENERALLY LIMITING ANY CONVECTIVE DEVELOPMENT. $$ COHEN