000 AXNT20 KNHC 280556 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT SUN JUN 28 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...TROPICAL WAVES... A TROPICAL WAVE EXTENDS FROM 11N40W TO 6N42W TO THE EQUATOR ALONG 42W 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 QUIKSCAT PASS AROUND 27/2040 UTC INDICATES CYCLONIC CURVATURE IN THE LOW LEVEL FLOW NEAR THIS WAVE. 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 35W S OF 10N. THIS AREA WILL CONTINUE TO BE MONITORED FOR THE PRESENCE OF A TROPICAL WAVE. A TROPICAL WAVE IS ALONG 72W S OF 20N MOVING W NEAR 10 KT AND IS AFFECTING PORTIONS OF THE CENTRAL CARIBBEAN. THIS WAVE IS NOT PARTICULARLY WELL DEFINED. HOWEVER...COMPUTER MODEL GUIDANCE SUGGESTS THAT THE WAVE COINCIDES WITH WEAK LOW LEVEL CYCLONIC CIRCULATION. ALSO...THE SOUNDING FROM CURACAO AT 27/1200 UTC INDICATES ANOMALOUS SOUTHEASTERLY FLOW IN THE LOW LEVELS...SUGGESTING THE WAVE AXIS WAS WEST OF CURACAO AT THAT TIME. THE PRESENCE OF DRY LOW/MID-LEVEL SAHARAN AIR OVER PORTIONS OF THE CENTRAL AND E CARIBBEAN IS INHIBITING DEEP CONVECTION NEAR THIS WAVE. HOWEVER...SCATTERED SHOWERS ARE OCCURRING FROM 16N-18N BETWEEN 68W-71W INCLUDING PORTIONS OF HISPANIOLA. A VIGOROUS TROPICAL WAVE EXTENDS FROM 23N86W TO 16N90W TO 10N90W IN THE E PACIFIC REGION MOVING W 10-15 KT AND IS AFFECTING PORTIONS OF THE W CARIBBEAN SEA AND E PACIFIC REGION. SURFACE OBSERVATIONS INDICATE CYCLONIC CURVATURE IN THE LOW LEVEL FLOW NEAR THE WAVE. LOW LEVEL CONVERGENCE NEAR THE WAVE IS SUPPORTING SHOWERS AND THUNDERSTORMS OVER PORTIONS OF THE W CARIBBEAN. IN PARTICULAR...NUMEROUS MODERATE CONVECTION IS FROM 18N-22N BETWEEN 82W-87W. ALSO...SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 14N-20N BETWEEN 86W-92W INCLUDING N PORTIONS OF SOUTH AMERICA AND SE PORTIONS OF MEXICO. ALL OF THIS CONVECTION IS ALSO BEING SUPPORTED BY UPPER LEVEL DIVERGENCE ASSOCIATED WITH AN UPPER LEVEL RIDGE OVER THE W AND CENTRAL CARIBBEAN. WHILE NO DEVELOPMENT OF THIS SYSTEM IS EXPECTED AS IT MOVES ACROSS THE YUCATAN PENINSULA...SOME SLOW DEVELOPMENT IS POSSIBLE AFTER IT MOVES INTO THE SOUTHERN GULF OF MEXICO LATER TODAY OR TONIGHT. THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. MEANWHILE...LOCALLY HEAVY RAINS AND GUSTY WINDS WILL CONTINUE TO AFFECT PORTIONS OF THE YUCATAN PENINSULA AND WESTERN CUBA THROUGH TONIGHT. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 10N14W 10N25W 9N36W 7N46W 5N54W. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 9N-11N BETWEEN 16W-19W. SCATTERED MODERATE CONVECTION IS FROM 1N-11N BETWEEN 19W-21W. SCATTERED MODERATE CONVECTION IS ALSO FROM 2N-4N BETWEEN 27W-29W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL LOW IS CENTERED OVER THE W GULF NEAR 22N96W. ATMOSPHERIC INSTABILITY ASSOCIATED WITH THIS UPPER LEVEL LOW IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS S OF 20N W OF 95W. ALSO...UPPER LEVEL DIFFLUENCE BETWEEN THE AFOREMENTIONED UPPER LEVEL LOW AND AN UPPER LEVEL RIDGE OVER THE W AND CENTRAL CARIBBEAN...AS WELL AS DEEP LAYER MOISTURE...ARE SUPPORTING SCATTERED SHOWERS S OF 24N BETWEEN 85W-87W. ELSEWHERE ACROSS THE N AND W GULF...SUBSIDENCE IN CONFLUENT EASTERLY FLOW ALOFT BETWEEN AN UPPER LEVEL HIGH OVER N TEXAS AND THE AFOREMENTIONED UPPER LEVEL LOW OVER THE W GULF...AS WELL AS DEEP LAYER DRY AIR...ARE RESULTING IN GENERALLY FAIR WEATHER. SHOWERS AND THUNDERSTORMS OVER THE W CARIBBEAN ARE ASSOCIATED WITH A TROPICAL WAVE EXTENDING FROM 23N86W TO 16N90W TO 10N90W. WHILE NO DEVELOPMENT OF THIS SYSTEM IS EXPECTED AS IT MOVES ACROSS THE YUCATAN PENINSULA...SOME SLOW DEVELOPMENT IS POSSIBLE AFTER IT MOVES INTO THE SOUTHERN GULF OF MEXICO LATER TODAY OR TONIGHT. CARIBBEAN SEA... SHOWERS AND THUNDERSTORMS OVER THE W CARIBBEAN ARE ASSOCIATED WITH A TROPICAL WAVE EXTENDING FROM 23N86W TO 16N90W TO 10N90W. PLEASE SEE THE TROPICAL WAVES 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. HOWEVER...UPPER LEVEL MOISTURE STREAMING SOUTHWARD IS SUPPORTING SCATTERED SHOWERS N OF 15N BETWEEN 71W-77W INCLUDING PORTIONS OF HISPANIOLA AND E CUBA. ACROSS THE E CARIBBEAN...DEEP LAYER DRY AIR...INCLUDING LOW/MID-LEVEL DRY SAHARAN AIR...IS 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 27N BETWEEN 65W-75W. ALSO...UPPER LEVEL DIFFLUENCE AND UPPER LEVEL MOISTURE ARE SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS FROM 23N-26N BETWEEN 73W-79W INCLUDING PORTIONS OF THE NW BAHAMAS. 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 1022 MB SURFACE HIGH NEAR 31N46W AND A 1021 MB SURFACE HIGH NEAR 22N37W. HOWEVER...AN UPPER LEVEL TROUGH N OF 19N E OF 26W IS SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM 23N44W TO 28N31W TO 31N24W AND A COLD FRONT THAT EXTENDS FROM 31N24W TO 32N19W TO NE OF THE DISCUSSION AREA. LOW LEVEL CONVERGENCE IS SUPPORTING SCATTERED SHOWERS WITHIN 60 NM EITHER SIDE OF THE SURFACE TROUGH AND COLD FRONT. ALSO...ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN UPPER LEVEL LOW NEAR 25N53W IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS FROM 23N-27N BETWEEN 52W-56W. ACROSS THE TROPICAL ATLC...MOIST EASTERLY FLOW ALOFT IS PRESENT...WITH UPPER LEVEL DIFFLUENCE SUPPORTING CONVECTION ASSOCIATED WITH THE ITCZ AND THE TROPICAL WAVE THAT EXTENDS FROM 11N40W TO 6N42W TO THE EQUATOR ALONG 42W. $$ COHEN