000 AXNT20 KNHC 251751 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 22N44W TO 11N38W MOVING W 15-20 KT. THIS WAVE IS ALONG THE LEADING EDGE OF A WEAK DEEP LAYER MOISTURE MAXIMUM AS OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. VISIBLE SATELLITE IMAGERY INDICATES LOW LEVEL CYCLONIC CURVATURE MAINLY N OF 17N. THE PRESENCE OF DRY SAHARAN AIR IS LIMITING DEEP CONVECTION NEAR THE WAVE. TROPICAL WAVE IS ALONG 80W/81W S OF 21N MOVING NEAR W 20 KT. THIS WAVE IS EMBEDDED WITHIN A BROAD AREA OF DEEP LAYER MOISTURE MAXIMUM AS OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. SUBSIDENCE AND DRY AIR OVER THE CENTRAL CARIBBEAN IS LIMITING DEEP CONVECTION. TROPICAL WAVE IS FROM 21N95W THROUGH THE GULF OF TEHUANTEPEC INTO THE E PACIFIC REGION MOVING WNW 20-25 KT. VISIBLE SATELLITE IMAGERY INDICATES THAT THIS WAVE HAS SPLIT WITH THE NORTHERN PORTION OVER THE GULF OF MEXICO WHILE THE REMAINDER OF THE WAVE IS OVER THE COAST OF CENTRAL AMERICA IN THE E PACIFIC REGION. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE S OF 22N TO OVER THE BAY OF CAMPECHE BETWEEN 92W-97W. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 14N16W 9N35W 11N54W 10N64W. AN AREA OF UPPER DIFFLUENCE IS OVER THE W TROPICAL ATLC GENERATING CLUSTERS OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION FROM 8N-14N BETWEEN 48W-55W. SMALL CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM 9N-13N BETWEEN 26W-30W. ISOLATED CLUSTERS OF SCATTERED MODERATE CONVECTION ARE WITHIN 120 NM ALONG THE COAST OF GUINEA AND WITHIN 120 NM S OF THE ITCZ FROM 23W-39W. ...DISCUSSION... GULF OF MEXICO... A BROAD UPPER LEVEL TROUGH EXTENDS DOWN FROM THE GREAT LAKES REGION THROUGH LOUISIANA AND INTO NE MEXICO COVERING THE GULF NW OF A LINE FROM TAMPICO MEXICO TO NAPLES FLORIDA. THIS UPPER LEVEL TROUGH CONTINUES TO SUPPORT A WEAKENING STATIONARY FRONT EXTENDING ALONG THE N GULF COAST STATES FROM S GEORGIA ALONG THE COASTLINE FROM PENSACOLA FLORIDA TO THE MISSISSIPPI/LOUISIANA BORDER. LOW LEVEL CONVERGENCE AND UPPER DIFFLUENCE SE OF THE FRONT IS SUPPORTING NUMEROUS/SCATTERED SHOWERS/THUNDERSTORMS WITHIN 120 NM OF LINE FROM 26N92W TO OVER THE FLORIDA PANHANDLE NEAR PANAMA CITY. AN ISOLATED CLUSTER OF SHOWERS/THUNDERSTORMS ARE N OF THE YUCATAN PENINSULA WITHIN A 60 NM RADIUS OF 23.5N87.5W. UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL TROUGH OVER THE GULF AND AN UPPER LEVEL RIDGE OVER THE W ATLC IS SUPPORTING NUMEROUS/SCATTERED SHOWERS/THUNDERSTORMS ACROSS S FLORIDA AND THE STRAITS OF FLORIDA FROM 24N TO LAKE OKEECHOBEE E OF 82W INTO THE W ATLC. THE REMAINDER OF THE GULF REMAINS TRANQUIL THIS AFTERNOON DOMINATED BY DRY AIR AND A 1017 MB SURFACE HIGH JUST OFF THE COAST OF TAMPA FLORIDA. CARIBBEAN SEA... BROAD UPPER LOW IN THE CENTRAL ATLC EXTENDS ACROSS THE NE CARIBBEAN FROM THE LEEWARD ISLANDS TO HISPANIOLA AND INTO THE CENTRAL CARIBBEAN NEAR 13N75W SETTING UP THE WEAK UPPER RIDGE OVER THE W ATLC TO THE E OF THE UPPER TROUGH OVER THE GULF OF MEXICO. UPPER LEVEL DIFFLUENCE BETWEEN THESE FEATURES IS SUPPORTING ISOLATED SHOWERS ACROSS THE NW CARIBBEAN N OF 20N W OF 80W. LOW LEVEL CONVERGENCE AND THE CLOSE PROXIMITY OF THE ITCZ IN THE E PACIFIC ARE GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ACROSS THE SW CARIBBEAN SW OF A LINE FROM CENTRAL NICARAGUA NEAR 13N84W TO PANAMA NEAR 9N80W. THE REMAINDER OF THE CARIBBEAN IS DOMINATED BY DRY AIR GIVING THE CENTRAL AND E CARIBBEAN TRANQUIL WEATHER THIS AFTERNOON. FRESH TO STRONG TRADE WINDS ARE ACROSS MOST OF THE CARIBBEAN WITH THE STRONGEST WINDS OF UP TO 30 KT OCCURRING NEAR THE COAST OF COLUMBIA. ATLANTIC OCEAN... A SURFACE TROUGH EXTENDS FROM 30N80W TO INLAND OVER CENTRAL FLORIDA NEAR LAKE OKEECHOBEE. THE BROAD UPPER LEVEL TROUGH OVER THE GULF OF MEXICO AND A BROAD UPPER TROUGH OVER THE CENTRAL ATLC IS INDUCING AN UPPER RIDGE OVER THE W ATLC PROVIDING UPPER LEVEL DIFFLUENCE TO GENERATE NUMEROUS/SCATTERED SHOWERS/ THUNDERSTORMS WITHIN 200/240 NM SW OF THE TROUGH S OF 29N AND SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 27N-30N BETWEEN 70W-76W. A SECOND SURFACE TROUGH EXTENDS FROM 27N67W TO 23N70W. THE BROAD UPPER TROUGH COVERING THE CENTRAL ATLC IS BETWEEN 56W-70W AND EXTENDS INTO THE E CARIBBEAN WITH AN UPPER LOW NEAR 28N60W. UPPER LEVEL DIFFLUENCE TO THE E OF THE UPPER TROUGH IS GENERATING SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS WITHIN 75 NM OF LINE FROM 27N59W TO 32N56W. THE REMAINDER OF THE ATLC IS DOMINATED BY A BROAD UPPER RIDGE WHICH IS PROVIDING UPPER LEVEL DIFFLUENCE TO GENERATE THE ACTIVITY ASSOCIATED WITH THE ITCZ. A SURFACE RIDGE COVERS THE ENTIRE ATLC BASIN INTO THE GULF OF MEXICO ANCHORED BY A 1029 MB HIGH JUST N OF THE DISCUSSION AREA NEAR 33N36W. THIS IS GIVING THE E ATLC AND THE REMAINDER OF THE CENTRAL ATLC FAIR WEATHER THIS AFTERNOON. $$ WALLACE