000 AXNT20 KNHC 191101 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1015 UTC. ...SPECIAL FEATURES... NONE. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 38W/39W S OF 17N MOVING W 10-15 KT. SATELLITE IMAGERY DEPICTS INVERTED-V SIGNATURE IN LOW LEVEL CLOUD COVERAGE...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 90 NM EITHER SIDE OF WAVE AXIS N OF 14N. TROPICAL WAVE IS ALONG 57W/58W S OF 16N MOVING W NEAR 10 KT. WAVE IS NOT PARTICULARLY WELL-DEFINED BASED ON SATELLITE IMAGERY...WITH WEAK COUNTERCLOCKWISE CURVATURE DEPICTED SURFACE WIND OBSERVATIONS NEAR WAVE AXIS. THIS WAVE IS BENEATH STABLE AND DEEP LAYER DRY AIR ON THE SE PERIPHERY OF AN UPPER HIGH NEAR 17N65W...RESULTING IN THE ABSENCE OF ANY DEEP CONVECTION NEAR THIS WAVE. ...THE ITCZ... ITCZ AXIS IS ANALYZED ALONG 9N12W 7N30W 9N45W 10N54W 10N61W. SCATTERED MODERATE CONVECTION IS FROM 4N-11N BETWEEN 12W-25W...AFFECTING W PORTIONS OF GAMBIA AND GUINEA-BISSAU. ISOLATED MODERATE CONVECTION IS FROM 8N-13N BETWEEN 43W-51W. ISOLATED MODERATE CONVECTION IS ALSO FROM 8N-12N BETWEEN 60W-65W. ...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 26N82W TO 24N86W 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...COMBINED WITH LOW LEVEL CONVERGENCE FROM THE COLD FRONT...ARE RESULTING IN CLOUDINESS AND ISOLATED SHOWERS WITHIN 60 NM EITHER SIDE OF THE COLD FRONT N OF 22N. FARTHER 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 OVER THE YUCATAN PENINSULA NEAR 17N90W. UPPER DIFFLUENCE NW OF THIS HIGH IS GENERATING ISOLATED SHOWERS OVER THE SW GULF FROM 19N-23N BETWEEN 94W-97W. CARIBBEAN SEA... AN UPPER RIDGE EXTENDS FROM AN UPPER HIGH NEAR 17N65W TO N VENEZUELA...AND A WEAK UPPER TROUGH IS PRESENT OVER THE NW CARIBBEAN. ALSO...A SURFACE TROUGH EXTENDS FROM E BELIZE NEAR 17N88W TO A 1010 MB SURFACE LOW NEAR 18N87W TO 16N79W TO 17N78W. LOW LEVEL CONVERGENCE FROM THE SURFACE TROUGH...COMBINED WITH UPPER LEVEL DIVERGENCE ASSOCIATED WITH AN UPPER HIGH NEAR 19N81W AND AMPLE MOISTURE OVER THE W CARIBBEAN...IS SUPPORTING SCATTERED MODERATE CONVECTION WITHIN 120 NM EITHER SIDE OF THE SURFACE TROUGH W OF 83W. FURTHER TO THE E...CONVECTIVE COVERAGE IS LIMITED AS A RESULT OF DRY AIR EMBEDDED WITHIN CONFLUENT SW FLOW ALOFT. HOWEVER...LOW LEVEL CONVERGENCE NEAR THE SURFACE TROUGH IS STRONG ENOUGH TO GENERATE ISOLATED MODERATE CONVECTION WITHIN 90 NM EITHER SIDE OF THE SURFACE TROUGH BETWEEN 78W-84W...AS WELL AS FROM 16N-19N BETWEEN 72W-76W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION OVER PORTIONS OF COSTA RICA...PANAMA...AND N COLOMBIA IS IMPACTING THE NEARBY SW CARIBBEAN WATERS. THIS CONVECTION IS BEING ENHANCED BY STRONG UPPER LEVEL DIVERGENCE. 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 1008 MB SURFACE LOW NEAR 35N71W TO 29N77W TO THE E CENTRAL FLORIDA PENINSULA NEAR 27N80W. DRY AIR WRAPPING AROUND THE BASE OF THE UPPER TROUGH...COMBINED WITH SUBSIDENCE IN NW FLOW ALOFT W OF THE UPPER TROUGH AXIS...IS GENERALLY LIMITING CONVECTION OVER THE W ATLC...HOWEVER ISOLATED SHOWERS ARE PRESENT WITHIN 90 NM EITHER SIDE OF THE FRONT W OF 78W. FURTHER TO THE E...A SURFACE TROUGH EXTENDS FROM THE 1010 MB SURFACE REMNANT LOW OF OMAR NEAR 35N49W TO 31N48W TO 28N55W TO 26N59W. HOWEVER...MAINLY DRY AND STABLE CONDITIONS AROUND AN UPPER HIGH CENTERED NEAR 17N65W 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 16N31W...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 15W...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 28N37W DUE THE COUNTERCLOCKWISE CIRCULATION AROUND A COMPACT N-TO-S UPPER TROUGH EXTENDING FROM 27N48W TO AN UPPER LOW NEAR 17N46W TO 11N46W. DEEP LAYER DRY AIR EMBEDDED WITHIN THESE FEATURES IS GENERALLY LIMITING ANY CONVECTIVE DEVELOPMENT. $$ COHEN