000 AXNT20 KNHC 291750 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT MON JUN 29 2009 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 21W S OF 15N MOVING W NEAR 15 KT. TIME-HEIGHT ANALYSES OF THE DAKAR SENEGAL UPPER AIR SOUNDING DATA INDICATES THAT THE WAVE AXIS MOVED W OF DAKAR WITHIN THE PAST 12 HOURS. METEOSAT-9 VISIBLE SATELLITE IMAGERY FROM THIS MORNING ALSO CONFIRMS THE POSITION OF THE WAVE WITH CYCLONIC TURNING NOTED IN THE LOW-LEVEL CLOUD FIELD AND AN INVERTED-V STRUCTURE. AT THE PRESENT TIME...THE WAVE LACKS ANY DEEP CONVECTION WITH ONLY SCATTERED SHOWERS FROM 5N-11N E OF THE WAVE AXIS TO 15W AND FROM 12N-16N BETWEEN 20W-25W. THESE SHOWERS REMAIN IN A LARGE SAHARAN AIR LAYER OF DUST SUSPENDED BETWEEN 950 MB TO 750 MB THAT STRETCHES ACROSS MUCH OF THE ERN ATLC. A TROPICAL WAVE EXTENDS FROM 14N47W TO 3N49W MOVING W 10-15 KT. THIS WAVE COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TPW PRODUCT FROM CIMSS. SATELLITE IMAGERY INDICATES THAT THE WAVE REMAINS ON THE LEADING EDGE OF A DRY AND STABLE SAHARAN AIR LAYER THAT IS RESULTING IN A LACK OF ANY DEEP CONVECTION ASSOCIATED WITH THE WAVE. HOWEVER... POSSIBLE SCATTERED SHOWERS ARE FROM 10N-15N BETWEEN 45W-51W. A TROPICAL WAVE IS ALONG 84W S OF 18N MOVING W NEAR 15 KT. THIS WAVE REMAINED ILL-DEFINED ON SATELLITE IMAGERY AND THE POSITION IS BASED ON CONTINUITY. GLOBAL MODEL DATA INDICATES THAT THE WAVE COINCIDES WITH WEAK LOW LEVEL CYCLONIC CIRCULATION. ISOLATED SHOWERS ARE OVER PORTIONS OF THE NW CARIBBEAN FROM 9N-17N BETWEEN 80W-87W INCLUDING PORTIONS OF CENTRAL AMERICA. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 12N15W 10N19W 8N22W 4N34W 4N47W. ISOLATED MODERATE CONVECTION IS FROM 4N-9N BETWEEN 23W-29W. ...DISCUSSION... GULF OF MEXICO... A SURFACE TROUGH OVER THE S GULF EXTENDS FROM 26N87W TO THE COAST OF MEXICO NEAR 19N92W. LOW LEVEL CONVERGENCE IS SUPPORTING SCATTERED SHOWERS FROM 18N-25N WITHIN 200 NM E OF THE SURFACE TROUGH INCLUDING PORTIONS OF THE YUCATAN PENINSULA. ISOLATED SHOWERS ARE ALSO OBSERVED ACROSS THE BAY OF CAMPECHE S OF 23N. THIS ACTIVITY IS BEING SUPPORTED BY UPPER LEVEL DIVERGENCE ASSOCIATED WITH AN UPPER LEVEL RIDGE OVER THE MIDDLE AND SW GULF. UPPER LEVEL DIVERGENCE SPREADS FARTHER TO THE E ACROSS THE ERN GULF AND FLORIDA PENINSULA AND ALONG WITH INCREASED LOW-LEVEL CONVERGENCE AHEAD OF A COLD FRONTAL BOUNDARY ACROSS THE SE CONUS ARE GENERATING SCATTERED SHOWERS AND TSTMS E OF 87W...INCLUDING MUCH OF THE FLORIDA PENINSULA. ACROSS THE NW GULF...SUBSIDENCE RESULTING FROM UPPER LEVEL CONFLUENCE IS SUPPORTING A 1011 MB SURFACE HIGH NEAR 25N92W. THIS SUBSIDENT ENVIRONMENT...ALONG WITH DEEP LAYER DRY AIR...ARE RESULTING IN GENERALLY FAIR WEATHER ACROSS THE NW GULF. CARIBBEAN SEA... A TROPICAL WAVE IS ALONG 84W IN THE WRN CARIBBEAN AND IS ASSOCIATED WITH ISOLATED SHOWERS W OF 81W AND ACROSS THE GULF OF HONDURAS AND PORTIONS OF INTERIOR CENTRAL AMERICA. THIS SHOWER ACTIVITY IS BEING SUPPORTED BY UPPER LEVEL DIFFLUENCE IN NLY FLOW ALOFT...AS WELL AS THE PRESENCE OF DEEP LAYER MOISTURE. ALSO...ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN UPPER LEVEL LOW OVER WRN HISPANIOLA NEAR 19N73W IS SUPPORTING SCATTERED SHOWERS N OF 15N BETWEEN 70W-76W INCLUDING PORTIONS OF SRN HAITI AND SWRN DOMINICAN REPUBLIC. ACROSS THE E CARIBBEAN...SUBSIDENCE IN CONFLUENT WLY FLOW ALOFT AND DEEP LAYER DRY AIR...INCLUDING LOW/MID-LEVEL DRY SAHARAN AIR...ARE RESULTING IN GENERALLY FAIR WEATHER ACROSS MUCH OF THE NE CARIBBEAN AND LESSER ANTILLES. HOWEVER...A FEW PASSING ISOLATED SHOWERS ARE BEING USHERED WWD ON FRESH TO STRONG TRADE WINDS. THESE WINDS ARE FORECAST TO PERSIST ACROSS THE CENTRAL CARIBBEAN THROUGH THE WEEK...WITH E TO SE WINDS OF 20 TO 25 KT AS A SURFACE HIGH PRESSURE RIDGE BUILDS IN ACROSS THE CENTRAL ATLC. ATLANTIC OCEAN... ACROSS THE SW NORTH ATLC...DIFFLUENCE IN NWLY FLOW ALOFT IS INTERACTING WITH DEEP LAYER MOISTURE TO SUPPORT SCATTERED SHOWERS AND TSTMS N OF 25N BETWEEN 57W-80W. THIS ACTIVITY IS ALSO BEING SUPPORTED BY LOW LEVEL CONVERGENCE ASSOCIATED WITH A SURFACE COLD FRONT DIPPING INTO THE DISCUSSION AREA ALONG 32N64W TO 31N69W. ISOLATED SHOWERS REMAIN ELSEWHERE N OF 22N BETWEEN 74W-81W ACROSS THE BAHAMAS AND STRAITS OF FLORIDA. FARTHER TO THE E...GENERALLY FAIR WEATHER IS PRESENT ACROSS MUCH OF THE CENTRAL AND E ATLC...WHERE SUBSIDENCE IS OCCURRING NEAR A BROAD SURFACE RIDGE ANCHORED ON A 1021 MB HIGH CENTERED NEAR 28N42W. HOWEVER...ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN UPPER LEVEL LOW NEAR 27N48W IS SUPPORTING ISOLATED SHOWERS AND TSTMS FROM 25N-29N BETWEEN 43W-48W. ACROSS THE TROPICAL ATLC...MOIST E-NE FLOW ALOFT IS PRESENT...WITH UPPER LEVEL DIFFLUENCE SUPPORTING THE SHOWER ACTIVITY ASSOCIATED WITH THE ITCZ AND THE TROPICAL WAVES. $$ HUFFMAN