000 AXNT20 KNHC 082327 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT WED JUL 08 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2245 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 47W/48W S OF 17N MOVING W 15-20 KT. THIS WAVE IS JUST W OF A DEEP LAYER MOISTURE MAXIMUM OBSERVED ON TOTAL PRECIPITABLE WATER IMAGERY. A LARGE AREA OF SAHARAN DUST SURROUNDS THE WAVE THAT COVERS THE TROPICAL ATLC E OF 55W TO W AFRICA. WITH THE DRY SAHARAN AIR LAYER SURROUNDING THE WAVE...NO DEEP CONVECTION IS IN THE VICINITY OF THE WAVE. A TROPICAL WAVE EXTENDS FROM THE NRN YUCATAN PENINSULA NEAR 21N88W TO 14N91W AND INTO THE E PACIFIC MOVING W NEAR 20 KT. THIS WAVE COINCIDES WITH A SIGNIFICANT AREA OF INCREASED MOISTURE ACROSS THE WRN CARIBBEAN AND CENTRAL AMERICA OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FOUND ACROSS THE YUCATAN PENINSULA AND PORTIONS OF CENTRAL AMERICA FROM 13N-22N BETWEEN 88W-93W. UPPER LEVEL DIFFLUENCE TO THE E OF AN UPPER LEVEL LOW OVER THE SRN BAY OF CAMPECHE IS ENHANCING THIS CONVECTION ASSOCIATED WITH THE WAVE. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 12N15W 8N25W 6N39W 7N55W AND INTO VENEZUELA NEAR 8N64W. ISOLATED MODERATE CONVECTION IS FROM 4N-12N BETWEEN 14W-27W. SIMILAR CONVECTION IS INLAND OVER VENEZUELA FROM 7N-10N BETWEEN 60W-63W. ...DISCUSSION... GULF OF MEXICO... A SURFACE TROUGH IN THE N CENTRAL GULF OF MEXICO EXTENDS FROM 28N88W TO 31N85W CONTINUING N OF THE DISCUSSION AREA TO A SURFACE LOW OVER CENTRAL GEORGIA. A SHORTWAVE UPPER LEVEL TROUGH IS OVER THE ERN CONUS ALONG 88W SUPPORTING THE SURFACE TROUGH. SURFACE CONVERGENCE NEAR THE SURFACE TROUGH AS WELL AS UPPER LEVEL DIFFLUENT FLOW ARE SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE NRN GULF N OF 27N E OF 93W CONTINUING INTO THE WRN ATLC. A TROPICAL WAVE OVER THE YUCATAN PENINSULA IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS IN THE ERN BAY OF CAMPECHE S OF 22N E OF 91W. THESE SHOWERS AREA ALSO SUPPORTED BY AN UPPER LEVEL LOW OVER THE BAY OF CAMPECHE NEAR 19N93W. THE REMAINDER OF THE GULF OF MEXICO IS UNDER A WEAK SURFACE RIDGE EXTENDING WWD FROM THE ATLC PRODUCING GENERALLY FAIR WEATHER S OF 27N. MOSTLY S TO SW SURFACE WINDS UP TO 15 KT ARE OBSERVED. MODERATE SUBSIDENCE ALOFT IS SUPPORTING THE FAIR WEATHER. CARIBBEAN SEA... A TROPICAL WAVE IS OVER THE YUCATAN PENINSULA IMPACTING PORTIONS OF CENTRAL AMERICA AND THE FAR WRN CARIBBEAN. SCATTERED SHOWERS/THUNDERSTORMS ARE S OF 22N W OF 88W. UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL LOW OVER THE BAY OF CAMPECHE NEAR 19N93W AND AN UPPER LEVEL HIGH OVER GUATEMALA NEAR 17N90W IS ENHANCING THIS SHOWER ACTIVITY AS WELL AS SCATTERED SHOWERS/THUNDERSTORMS NOT ASSOCIATED WITH THE WAVE S OF 16N W OF 83W ACROSS SRN CENTRAL AMERICA INCLUDING HONDURAS...NICARAGUA...AND COSTA RICA. A 1008 MB SURFACE LOW OVER COLUMBIA NEAR 8N75W AS WELL AS CONVERGENCE ALONG THE ITCZ ARE SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS OVER THE S CARIBBEAN S OF 11N BETWEEN 74W-83W INCLUDING PORTIONS OF COSTA RICA AND PANAMA. THE REMAINDER OF THE CARIBBEAN...WITH THE EXCEPTION OF THE FAR NERN WATERS...IS UNDER THE INFLUENCE OF A SAHARAN AIR LAYER OF DUST SUSPENDED IN THE MIDDLE LEVELS OF THE ATMOSPHERE. THE SUSPENDED DUST IS OBSERVED ON VISIBLE SATELLITE IMAGERY AND NUMEROUS OF THE UPPER AIR TIME SECTION ANALYSES ACROSS THE ERN AND CENTRAL CARIBBEAN. WITH THIS DRIER AIR IN PLACE...ONLY A FEW ISOLATED LOW-LEVEL SHOWERS ARE NOTED N OF 16N E OF 67W IN ASSOCIATION WITH A SURFACE TROUGH THAT EXTENDS FROM THE CENTRAL ATLC TO NEAR 18N65W. FRESH TO STRONG ELY TRADE WIND FLOW CONTINUES ACROSS THE BASIN AND IS FORECAST TO PERSIST THROUGH FRIDAY AND INTO THE WEEKEND. ATLANTIC OCEAN... SCATTERED SHOWERS AND TSTMS ARE ACROSS THE SW NORTH ATLC N OF 28N W OF 70W. THIS ACTIVITY IS SUPPORTED BY LOW-LEVEL CONVERGENCE ALONG AND S OF A COLD FRONT THAT PARALLELS 32N BETWEEN 70W-75W CONTINUING AS A STATIONARY FRONT TO THE SOUTH CAROLINA/GEORGIA COAST. THIS ACTIVITY IS FURTHER ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL TROUGH OVER THE ERN CONUS ALONG 88W AND AN UPPER LEVEL RIDGE OVER THE W ATLC CENTERED AROUND AN UPPER LEVEL HIGH NEAR 31W62W. A 1023 MB SURFACE HIGH IS OVER THE CENTRAL ATLC NEAR 29N43W SUPPORTING GENERALLY FAIR WEATHER BESIDES A WEAK SURFACE TROUGH THAT EXTENDS FROM 25N52W TO THE LEEWARD ISLANDS NEAR 18N65W. PREVIOUSLY NOTED SHOWERS HAVE NOW DISSIPATED. A LARGE AREA OF SAHARAN DUST COVERS THE TROPICAL ATLC E OF 55W TO W AFRICA REDUCING CONVECTION ALONG THE ITCZ. $$ WALTON