000 AXNT20 KNHC 271050 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT SAT JUN 27 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1045 UTC. ...SPECIAL FEATURES... AN ACTIVE TROPICAL WAVE IN THE W CARIBBEAN IS ALONG 86W/87W S OF 23N MOVING W 10-15 KT. LOW LEVEL CONVERGENCE NEAR THE TROPICAL WAVE IS SUPPORTING SHOWERS AND THUNDERSTORMS OVER PORTIONS OF THE W CARIBBEAN. IN PARTICULAR...NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS FROM 17N-22N BETWEEN 79W-84W AND FROM 18N-20N BETWEEN 85W-87W. ALL OF THIS CONVECTION IS ALSO BEING SUPPORTED BY UPPER LEVEL DIVERGENCE W OF AN UPPER LEVEL RIDGE OVER THE CENTRAL CARIBBEAN AND SE GULF OF MEXICO... AS WELL AS THE PRESENCE OF ABUNDANT DEEP LAYER MOISTURE. SIGNIFICANT DEVELOPMENT OF THIS SYSTEM IS NOT EXPECTED BEFORE IT REACHES THE YUCATAN PENINSULA LATER TODAY. HOWEVER... ENVIRONMENTAL CONDITIONS COULD BECOME FAVORABLE FOR DEVELOPMENT ONCE THE SYSTEM EMERGES INTO THE SOUTHERN GULF OF MEXICO TONIGHT OR SUNDAY. THERE IS A MEDIUM CHANCE...30 TO 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. MEANWHILE...LOCALLY HEAVY RAINS ARE POSSIBLE OVER PORTIONS OF WESTERN CUBA AND HONDURAS TODAY AND COULD SPREAD WESTWARD INTO NORTHERN CENTRAL AMERICA AND THE YUCATAN PENINSULA DURING THE NEXT DAY OR SO. ...TROPICAL WAVES... A TROPICAL WAVE EXTENDS FROM 13N37W TO 6N38W TO 1N39W MOVING W NEAR 10 KT AND IS AFFECTING PORTIONS OF THE TROPICAL ATLC. THIS WAVE IS ANALYZED NEAR THE LEADING EDGE OF AN ELONGATED MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. THE CIMSS WAVETRAK PRODUCT INDICATES THAT THIS WAVE IS ASSOCIATED WITH AN AREA OF WEAK LOW LEVEL CYCLONIC CIRCULATION. SCATTERED MODERATE CONVECTION IS FROM 2N-8N BETWEEN 33W-38W. COMPUTER MODEL GUIDANCE SUGGESTS THAT AN AREA OF STRONGER LOW LEVEL CYCLONIC CIRCULATION IS EMBEDDED FARTHER EASTWARD INTO THE ELONGATED DEEP LAYER MOISTURE MAXIMUM... APPROXIMATELY ALONG 29W S OF 9N. THIS AREA WILL CONTINUE TO BE MONITORED FOR THE PRESENCE OF A TROPICAL WAVE. A TROPICAL WAVE IS ALONG 69W/70W S OF 20N MOVING W 10-15 KT AND IS AFFECTING PORTIONS OF THE E CARIBBEAN. THIS WAVE IS ALSO ASSOCIATED WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. THE PRESENCE OF DRY LOW/MID-LEVEL SAHARAN AIR OVER PORTIONS OF THE E CARIBBEAN IS INHIBITING DEEP CONVECTION NEAR THIS WAVE. HOWEVER...SCATTERED SHOWERS ARE OCCURRING FROM 16N-18N BETWEEN 68W-71W INCLUDING PORTIONS OF HISPANIOLA. AN ACTIVE TROPICAL WAVE IS ALONG 86W/87W S OF 23N MOVING W 10-15 KT AND IS AFFECTING PORTIONS OF THE W CARIBBEAN. THE 1009 MB SURFACE LOW PREVIOUSLY ANALYZED ALONG THIS WAVE NEAR 17.9N84W AT 27/0000 UTC HAS BEEN REMOVED FOR THE 27/0600 UTC SURFACE ANALYSIS DUE TO THE ABSENCE OF A CLOSED CIRCULATION IN THIS AREA BASED ON THE 27/0240 UTC ASCAT PASS. THIS WAVE AND ITS ASSOCIATED CONVECTION IS DISCUSSED IN THE SPECIAL FEATURES SECTION ABOVE. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 12N16W 8N25W 8N35W 7N45W 5N54W. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 5N-11N BETWEEN 10W-23W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 6N-9N BETWEEN 23W-28W. SCATTERED MODERATE CONVECTION IS FROM 5N-8N BETWEEN 51W-59W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL LOW IS CENTERED OVER THE BAY OF CAMPECHE NEAR 21N93W. ATMOSPHERIC INSTABILITY ASSOCIATED WITH THIS UPPER LEVEL LOW IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS S OF 21N W OF 93W. ALSO...DIFFLUENT SOUTHERLY FLOW ALOFT BETWEEN THE AFOREMENTIONED UPPER LEVEL LOW AND AN UPPER LEVEL RIDGE OVER THE SE GULF AND CENTRAL CARIBBEAN...AS WELL AS DEEP LAYER MOISTURE...ARE SUPPORTING SCATTERED SHOWERS FROM 22N-24N BETWEEN 83W-87W. ELSEWHERE ACROSS THE N AND W GULF...SUBSIDENCE IN NE FLOW ALOFT BETWEEN AN UPPER LEVEL HIGH OVER N TEXAS AND THE AFOREMENTIONED UPPER LEVEL LOW OVER THE BAY OF CAMPECHE...AS WELL AS DEEP LAYER DRY AIR...ARE RESULTING IN GENERALLY FAIR WEATHER. HOWEVER...UPPER LEVEL MOISTURE STREAMING SOUTHWESTWARD AROUND THE UPPER HIGH IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ACROSS THE N GULF N OF 27N BETWEEN 89W-93W. SHOWERS AND THUNDERSTORMS OVER THE W CARIBBEAN ARE ASSOCIATED WITH A TROPICAL WAVE ALONG 86W/87W. ENVIRONMENTAL CONDITIONS COULD BECOME FAVORABLE FOR DEVELOPMENT ONCE THE SYSTEM EMERGES INTO THE SOUTHERN GULF OF MEXICO TONIGHT OR SUNDAY. CARIBBEAN SEA... SHOWERS AND THUNDERSTORMS OVER THE W CARIBBEAN ARE ASSOCIATED WITH A TROPICAL WAVE ALONG 86W/87W. PLEASE SEE THE TROPICAL WAVES SECTION AND SPECIAL FEATURES SECTION ABOVE FOR MORE INFORMATION ON THIS SYSTEM. ACROSS THE CENTRAL CARIBBEAN...AN UPPER LEVEL RIDGE IS PRESENT...WITH SUBSIDENCE AND ATMOSPHERIC STABILITY SUPPORTING GENERALLY FAIR WEATHER ACROSS MUCH OF THE CENTRAL CARIBBEAN. ACROSS THE E CARIBBEAN...DEEP LAYER DRY AIR...SUBSIDENCE DUE TO CONFLUENT NORTHWESTERLY FLOW ALOFT...AND THE PRESENCE OF LOW/MID-LEVEL DRY SAHARAN AIR ARE RESULTING IN GENERALLY FAIR WEATHER. ATLANTIC OCEAN... ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN UPPER LEVEL TROUGH OVER THE SW NORTH ATLC IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS N OF 25N BETWEEN 66W-78W. ALSO...ATMOSPHERIC LIFT IN MOIST SOUTHWESTERLY FLOW ALOFT IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS N OF 26N BETWEEN 60W-66W. THIS ACTIVITY IS ALSO BEING SUPPORTED BY LOW LEVEL CONVERGENCE NEAR A SURFACE TROUGH THAT EXTENDS FROM 31N62W TO 32N61W TO NE OF THE DISCUSSION AREA. 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. THIS SURFACE RIDGE IS ASSOCIATED WITH A 1023 MB SURFACE HIGH NEAR 32N46W AND A 1019 MB SURFACE HIGH NEAR 22N29W. HOWEVER...AN UPPER LEVEL TROUGH N OF 23N BETWEEN 19W-31W IS SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM 27N35W TO 30N25W TO 32N22W TO NE OF THE DISCUSSION AREA. LOW LEVEL CONVERGENCE IS SUPPORTING SCATTERED SHOWERS WITHIN 60 NM EITHER SIDE OF THE SURFACE TROUGH. ALSO...ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN UPPER LEVEL LOW NEAR 22N53W IS SUPPORTING SCATTERED SHOWERS FROM 19N-22N BETWEEN 56W-60W. ACROSS THE TROPICAL ATLC...AN UPPER LEVEL RIDGE AXIS EXTENDS FROM 17N15W TO AN UPPER LEVEL HIGH NEAR 16N36W TO 6N49W. UPPER LEVEL DIVERGENCE ASSOCIATED WITH THE UPPER LEVEL HIGH AND UPPER LEVEL RIDGE IS SUPPORTING CONVECTION ASSOCIATED WITH THE ITCZ AND THE TROPICAL WAVE THAT EXTENDS FROM 13N37W TO 6N38W TO 1N39W. $$ COHEN