000 AXNT20 KNHC 251051 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT SAT JUL 25 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 1000 UTC. ...TROPICAL WAVES... A TROPICAL WAVE EXTENDS FROM 21N41W TO 14N38W TO 8N34W MOVING W NEAR 18 KT. THIS WAVE IS JUST W OF A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. SATELLITE IMAGERY INDICATES LOW-LEVEL CYCLONIC FLOW AROUND THE VICINITY OF THIS WAVE. SATELLITE DERIVED WINDS ALSO INDICATE CYCLONIC TURNING IN THE LOW/MID-LEVELS OF THE ATMOSPHERE. THE PRESENCE OF LOW/MID-LEVEL DRY SAHARAN AIR IS LIMITING DEEP CONVECTION NEAR THE WAVE. HOWEVER...SCATTERED MODERATE CONVECTION IS EMBEDDED WITHIN THE ITCZ FROM 7N-9N BETWEEN 34W-37W. A TROPICAL WAVE IS ALONG 78W/79W S OF 21N MOVING W 20 KT. THIS WAVE COINCIDES WITH A BROAD AREA OF DEEP LAYER MOISTURE OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. SUBSIDENCE AND DRY AIR IN NELY FLOW ALOFT ARE INHIBITING DEEP CONVECTION NEAR THE WAVE. HOWEVER...NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS OVER COLUMBIA FROM 7N-11N BETWEEN 76W-80W. THIS CONVECTION IS ENHANCED BY LOW-LEVEL CONVERGENCE NEAR A PERSISTENT SURFACE LOW CENTERED NEAR 8N76W AND THE PROXIMITY OF THE E PACIFIC ITCZ. A TROPICAL WAVE IS ALONG 92W S OF 21N MOVING W 20-25 KT. THIS WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. A CLUSTER OF NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS E OF THE WAVE AXIS FROM 11N-14N BETWEEN 88W-91W. THIS CONVECTION IS ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL RIDGE OVER MEXICO AND AN UPPER LEVEL TROUGH IN THE E PACIFIC. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 12N15W 9N25W 10N43W 10N53W 8N61W. SCATTERED MODERATE CONVECTION IS FROM 6N-10N BETWEEN 21W-29W. SIMILAR CONVECTION IS FROM 8N-12N BETWEEN 48W-53W. ...DISCUSSION... GULF OF MEXICO... A BROAD UPPER LEVEL TROUGH EXTENDS DOWN THE ERN CONUS TO LOUISIANA EXTENDING OVER THE GULF OF MEXICO TO 25N97W. THIS UPPER LEVEL TROUGH SUPPORTS A STATIONARY FRONT EXTENDING ALONG 31N BETWEEN 85W-92W. LOW-LEVEL CONVERGENCE AHEAD OF THIS FRONT IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS ALONG THE NW GULF N OF 27N BETWEEN 85W-92W. UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL TROUGH AND AN UPPER LEVEL RIDGE OVER MEXICO IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE SW GULF S OF 21N BETWEEN 94W-97W. UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL TROUGH OVER THE GULF AND AN UPPER LEVEL HIGH N OF THE BAHAMAS NEAR 23N71W IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE SE GULF S OF 25N E OF 88W INCLUDING THE STRAITS OF FLORIDA. THE REMAINDER OF THE GULF IS DOMINATED BY DRY AIR AND SUBSIDENCE ALOFT ASSOCIATED WITH A 1017 MB SURFACE HIGH NEAR 27N84W...RESULTING IN GENERALLY FAIR WEATHER. E TO SE SURFACE WINDS UP TO 15 KT ARE ACROSS THE SW GULF...REACHING 20 KT NEAR THE YUCATAN PENINSULA COAST. EXPECT SE FLOW TO INCREASE ACROSS THE W GULF EARLY NEXT WEEK. CARIBBEAN SEA... UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL TROUGH OVER THE GULF OF MEXICO AND AN UPPER LEVEL HIGH N OF THE BAHAMAS NEAR 23N71W IS SUPPORTING ISOLATED SHOWERS/THUNDERSTORMS ACROSS THE NW CARIBBEAN N OF 16N W OF 83W. SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS THE SW CARIBBEAN S OF 14N W OF 76W INCLUDING NICARAGUA...COSTA RICA...AND PANAMA. THIS ACTIVITY IS SUPPORTED BY UPPER LEVEL DIFFLUENCE...THE PROXIMITY OF THE E PACIFIC ITCZ...AND A TROPICAL WAVE ALONG 78W/79W. ELSEWHERE...DRY AIR AND SUBSIDENCE IN NELY FLOW ALOFT ARE SUPPORTING GENERALLY FAIR WEATHER ACROSS THE CENTRAL AND E CARIBBEAN. FRESH TO STRONG TRADE WINDS ARE OCCURRING ACROSS THE E AND CENTRAL CARIBBEAN WITH THE STRONGEST WINDS UP TO 30 KT OCCURRING NEAR THE COAST OF COLUMBIA. ATLANTIC OCEAN... THE BROAD UPPER LEVEL TROUGH OVER THE ERN CONUS EXTENDS OVER THE FAR W ATLC SUPPORTING A SURFACE TROUGH OVER THE FLORIDA PENINSULA EXTENDING FROM 27N81W TO 30N79W. LOW-LEVEL CONVERGENCE NEAR THE SURFACE TROUGH ALONG WITH UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL TROUGH AND AN UPPER LEVEL RIDGE TO THE E CENTERED N OF THE BAHAMAS NEAR 23N71W ARE SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS N OF 23N BETWEEN 71W-80W. A SECOND SURFACE TROUGH IS ANALYZED N OF THE BAHAMAS FROM 22N73N TO 27N67W. LOW-LEVEL CONVERGENCE NEAR THIS TROUGH MAY BE ENHANCING THE SHOWER ACTIVITY TO THE W. UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL TROUGH CENTERED NEAR 28N56W AND AN UPPER LEVEL RIDGE CENTERED NEAR 21N41N IS SUPPORTING AN AREA OF SHOWERS/POSSIBLE THUNDERSTORMS FROM 25N-29N BETWEEN 56W-58W. THE REMAINDER OF THE ATLC IS DOMINATED BY A BROAD SURFACE RIDGE ANCHORED BY A 1028 MB HIGH N OF THE DISCUSSION AREA CENTERED NEAR 34N34W BRINGING GENERALLY FAIR WEATHER ACROSS THE AREA. AN UPPER LEVEL HIGH OVER THE CENTRAL ATLC CENTERED NEAR 21N41W IS SUPPORTING CONVECTION ALONG THE ITCZ. $$ WALTON