000 AXNT20 KNHC 271728 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1645 UTC. ...SPECIAL FEATURES... AN ACTIVE TROPICAL WAVE IN THE FAR W CARIBBEAN EXTENDING FROM 21N86W TO 5N88W MOVG W 10-15 KT. LOW LEVEL CONVERGENCE NEAR THE WAVE IS SUPPORTING DISORGANIZED SHOWERS AND THUNDERSTORMS FROM CUBA AND THE CAYMAN ISLANDS WESTWARD TO THE YUCATAN PENINSULA. IN PARTICULAR...NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS FROM 17N-21N BETWEEN 84W-88W. SCATTERED MODERATE CONVECTION IS FROM 20N-23N BETWEEN 78W-81W. THIS CONVECTION IS BEING ENHANCING BY UPPER LEVEL DIFFLUENCE W OF AN UPPER LEVEL RIDGE OVER THE CENTRAL CARIBBEAN. CURRENT SATELLITE IMAGES INDICATE THAT THE LOW-LEVEL CIRCULATION IS NOT WELL-DEFINED. SIGNIFICANT DEVELOPMENT OF THIS SYSTEM IS NOT EXPECTED TODAY ALTHOUGH ENVIRONMENTAL CONDITIONS SHOULD BECOME MORE FAVORABLE FOR SOME DEVELOPMENT ONCE THE SYSTEM MOVES INTO THE SOUTHERN GULF OF MEXICO TONIGHT. THERE IS A MEDIUM CHANCE...30 TO 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. LOCALLY HEAVY RAINS WILL AFFECT PORTIONS OF WESTERN AND CENTRAL CUBA...THE CAYMAN ISLANDS...AND THE YUCATAN PENINSULA TODAY AND COULD SPREAD NORTHWARD TOWARDS SOUTH FLORIDA OVER THE NEXT DAY OR SO. ...TROPICAL WAVES... A TROPICAL WAVE IN THE CENTRAL ATLANTIC HAS BEEN RELOCATED JUST E OF THE PREVIOUS ANALYSIS POSITION AND EXTENDS FROM 10N37W TO 1N38W MOVG W 10 KT. THE RELOCATION IS BASED ON SCATTEROMETER DATA INDICATING A STRONGER CYCLONIC WIND SHIFT FARTHER E OF THE PREVIOUS POSITION. THE NEW POSITION ALSO COINCIDES BETTER WITH AN ELONGATED DEEP MOISTURE MAXIMUM BASED ON TOTAL PRECIPITABLE WATER IMAGERY. THIS WAVE IS EMBEDDED IN THE ITCZ REDUCING THE CONFIDENCE IN THE EXACT LOCATION AND TRACKING OF THIS WAVE. ISOLATED MODERATE CONVECTION IS FROM 1N-9N BETWEEN 36W-41W. MODEL GUIDANCE SUGGESTS THAT AN AREA OF STRONGER LOW LEVEL CYCLONIC CIRCULATION IS EMBEDDED EVEN FARTHER E ALONG 31W. THAT AREA WILL CONTINUE TO BE MONITORED FOR THE PRESENCE OF A TROPICAL WAVE. A TROPICAL WAVE IS ALONG 71W/72W S OF 20N MOVING W 10-15 KT. THE PRESENCE OF DRY LOW/MID-LEVEL SAHARAN AIR OVER PORTIONS OF THE E CARIBBEAN IS INHIBITING DEEP CONVECTION NEAR THIS WAVE. HOWEVER...ISOLATED SHOWERS ARE OCCURRING FROM 18N-20N BETWEEN 69W-71W INCLUDING PORTIONS OF HISPANIOLA. AN ACTIVE TROPICAL WAVE EXTENDS FROM 21N86W TO 5N88W MOVG W 10-15 KT AND IS AFFECTING PORTIONS OF THE W CARIBBEAN. THIS WAVE AND ITS ASSOCIATED CONVECTION IS DISCUSSED IN THE SPECIAL FEATURES SECTION ABOVE. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 12N16W 8N24W 8N36W 7N47W AND INTO NE S AMERICA NEAR 5N56W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 5N-9N BETWEEN 15W-18W. SCATTERED MODERATE CONVECTION IS FROM 3N-10N BETWEEN 22W-27W...FROM6N-8N BETWEEN 28W-34W...AND FROM 6N-10N BETWEEN 52W-58W. ...DISCUSSION... GULF OF MEXICO... UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL LOW CENTERED OVER THE BAY OF CAMPECHE NEAR 20N94W AND AN UPPER LEVEL HIGH OVER N TEXAS IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS OFF THE COAST OF LOUISIANA AND TEXAS N OF 28N BETWEEN 91W-94W. UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL RIDGE OVER THE CENTRAL/E UNITED STATES AND AN UPPER LEVEL TROUGH IN THE NW ATLC IS SUPPORTING ISOLATED SHOWERS/THUNDERSTORMS ACROSS N FLORIDA AND THE ADJACENT COASTAL WATERS N OF 27N E OF 85W. ELSEWHERE ACROSS THE CENTRAL AND W GULF...SUBSIDENCE AND DEEP LAYER DRY AIR ARE RESULTING IN GENERALLY FAIR WEATHER. HOWEVER...MOISTURE SURGING N FROM THE YUCATAN DUE TO THE APPROACH OF AN ACTIVE TROPICAL WAVE IN THE FAR W CARIBBEAN IS SUPPORTING SHOWERS IN THE FAR SE GULF OF MEXICO AND YUCATAN CHANNEL E OF 87W S OF 25N. CARIBBEAN SEA... SHOWERS AND THUNDERSTORMS OVER THE W CARIBBEAN ARE ASSOCIATED WITH A TROPICAL WAVE...SEE ABOVE. AN UPPER LEVEL RIDGE IS OVER THE CENTRAL CARIBBEAN BRINGING SUBSIDENCE AND ATMOSPHERIC STABILITY SUPPRESSING THE TROPICAL WAVE IN THE CENTRAL CARIBBEAN...SEE ABOVE... IS SUPPORTING GENERALLY FAIR WEATHER ACROSS MUCH OF THE CENTRAL CARIBBEAN. ACROSS THE E CARIBBEAN CONFLUENT NORTHWESTERLY FLOW ALOFT AND THE PRESENCE OF LOW/MID-LEVEL DRY SAHARAN AIR ARE ALSO RESULTING IN GENERALLY FAIR WEATHER. ATLANTIC OCEAN... UPPER LEVEL DIFFLUENCE ASSOCIATED WITH AN UPPER LEVEL TROUGH OVER THE SW NORTH ATLC IS SUPPORTING SCATTERED SHOWERS/ THUNDERSTORMS N OF 27N BETWEEN 64W-78W. ALSO MOIST SOUTHWESTERLY FLOW ALOFT IS SUPPORTING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS N OF 29N BETWEEN 59W-62W. MOIST UPPER LEVEL FLOW AROUND THE RIDGE OVER THE CENTRAL CARIBBEAN IS SUPPORTING ISOLATED SHOWERS/THUNDERSTORMS ACROSS THE BAHAMAS S OF 27N W OF 72W. REMNANTS OF A CONVECTIVE BURST ASSOCIATED WITH THE TROPICAL WAVE IN THE W CARIBBEAN CONTINUES TO AFFECT PORTIONS OF CENTRAL CUBA AND THE ADJACENT N WATERS S OF 24N BETWEEN 78W-80W. FARTHER TO THE E...A PAIR OF SURFACE HIGHS...A 1023 MB CENTER NEAR 32N47W...AND A 1021 MB CENTER NEAR 22N30W... ARE RESULTING IN GENERALLY FAIR WEATHER. AN UPPER LEVEL TROUGH N OF 22N BETWEEN 20W-35W IS SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM 26N34W TO 31N22W. ACROSS THE TROPICAL ATLC...A BROAD UPPER LEVEL RIDGE IS PRESENT WITH AXIS EXTENDING FROM AN UPPER LEVEL HIGH NEAR 16N35W IS SUPPORTING CONVECTION ALONG THE ITCZ. $$ WALTON