000 AXNT20 KNHC 241757 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT FRI JUL 24 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... A TROPICAL WAVE EXTENDS ALONG 10N30W TO 21N35W MOVING W NEAR 18 KT. SATELLITE IMAGERY INDICATES A BROAD AREA OF LOW-LEVEL CYCLONIC TURNING NEAR THE WAVE AXIS AND THIS IS CONFIRMED ON AN EARLIER QSCAT PASS AROUND 24/0800 UTC...THOUGH WINDS ARE GENERALLY WEAK. CONVECTION IS MINIMAL AND MOSTLY CONFINED ALONG THE ITCZ AXIS FROM 8N-11N BETWEEN 28W-32W. A TROPICAL WAVE IS ALONG 73W S OF 20N MOVING W NEAR 25 KT. VISIBLE SATELLITE IMAGERY AND TOTAL PRECIPITABLE WATER IMAGES INDICATE A SLIGHT INVERTED-V SIGNATURE IN THE LOW-LEVEL CLOUDS ACROSS THE CENTRAL CARIBBEAN. UPPER LEVEL DRY AIR AND A MID-LEVEL SAHARAN AIR LAYER ARE INHIBITING ANY DEEP CONVECTION. A TROPICAL WAVE IS ALONG 85W S OF 22N MOVING W NEAR 25 KT. SATELLITE IMAGES SHOW LITTLE EVIDENCE OF THIS WAVE AT THE MOMENT...HOWEVER TOTAL PRECIPITABLE WATER IMAGERY INDICATES A MAXIMUM MOVING OVER THE NW CARIBBEAN AND PORTIONS OF HONDURAS AND NICARAGUA SUGGESTING THE POSITION OF THE WAVE AS IT TRACKS WWD. ISOLATED SHOWERS AND TSTMS ARE S OF 12N W OF 81W AND ARE MORE LIKELY ASSOCIATED WITH UPPER LEVEL DIFFLUENCE. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 11N15W 11N27W 10N32W 9N62W. SCATTERED MODERATE CONVECTION IS FROM 7N-12N BETWEEN 20W-26W. ISOLATED MODERATE CONVECTION IS FROM 7N-12N BETWEEN 32W-46W. ...DISCUSSION... GULF OF MEXICO... UPPER LEVEL DIFFLUENCE AND MOISTURE IN WLY FLOW ALOFT COMBINED WITH LOW-LEVEL CONVERGENCE ALONG A WEAK COLD FRONT EXTENDING FROM THE FLORIDA PANHANDLE THROUGH NEW ORLEANS LOUISIANA TO ERN TEXAS ARE SUPPORTING SCATTERED SHOWERS AND ISOLATED TSTMS N OF 27N BETWEEN 84W-93W. SCATTERED SHOWERS AND TSTMS ARE OVER S FLORIDA ENHANCED BY A WEAK SURFACE TROUGH THAT EXTENDS FROM WRN CUBA TO NEAR LAKE OKEECHOBEE. ALSO OF NOTE...AN UPPER LEVEL HIGH IS CENTERED ALONG THE E/CENTRAL MEXICO COAST NEAR 19N98W AND IS PROVIDING UPPER DIFFLUENCE FOR SCATTERED SHOWERS AND ISOLATED TSTMS ACROSS THE WRN BAY OF CAMPECHE FROM 18N-23N W OF 94W. ELSEWHERE...DEEP LAYER DRY AIR AND SURFACE RIDGING IS PROMOTING FAIR WEATHER. THE SURFACE RIDGE IS FORECAST TO GRADUALLY SHIFT EWD THROUGH THE WEEKEND WITH INCREASING SE RETURN FLOW ACROSS THE WRN GULF BY LATE IN THE WEEKEND AND EARLY NEXT WEEK. CARIBBEAN SEA... A BROAD UPPER LEVEL RIDGE EXTENDS ACROSS SRN MEXICO AND THE YUCATAN PENINSULA TO CUBA...JAMAICA AND HISPANIOLA REMAINING LARGELY N OF 15N OVER THE NW AND N/CENTRAL CARIBBEAN. UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THIS UPPER RIDGE AND LOW-LEVEL SPEED CONVERGENCE ARE SUPPORTING ISOLATED SHOWERS AND TSTMS OVER PORTIONS OF WRN CUBA AND NRN CENTRAL AMERICA ALONG WITH THE NW CARIBBEAN WATERS N OF 17N. UPPER LEVEL DIFFLUENCE IS ALSO SUPPORTING SCATTERED SHOWERS AND TSTMS OVER THE SW CARIBBEAN S OF 12N...INCLUDING COSTA RICA AND PANAMA. ACROSS THE ERN CARIBBEAN...SCATTERED SHOWERS AND ISOLATED TSTMS ARE AFFECTING THE SE WATERS S OF 13N E OF 67W DUE TO THE PROXIMITY OF THE ITCZ AXIS THAT EXTENDS ALONG THE NRN BORDER OF VENEZUELA. FAIR WEATHER EXISTS ACROSS THE CENTRAL CARIBBEAN SUPPORTED BY MODERATE SUBSIDENCE AND DRY AIR ALOFT. ATLANTIC OCEAN... A MID-UPPER LEVEL TROUGH IS OVER THE W ATLC WHILE AN UPPER LEVEL RIDGE EXTENDS FROM E OF THE BAHAMAS NEAR 25N71W TO BEYOND 32N65W. BETWEEN THESE TWO UPPER LEVEL FEATURES...DIFFLUENCE ALOFT AND LOW-LEVEL CONVERGENCE ARE SUPPORTING SCATTERED SHOWERS AND TSTMS FROM 25N-28N BETWEEN 74W-78W WHILE MORE WIDELY SCATTERED SHOWERS ARE LOCATED N OF 22N BETWEEN 66W-74W. FARTHER TO THE E...SUBSIDENCE ASSOCIATED WITH A DEEP LAYER RIDGE IS RESULTING IN GENERALLY FAIR WEATHER ACROSS MUCH OF THE CENTRAL AND E ATLC. HOWEVER...ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN UPPER LEVEL LOW CENTERED NEAR 26N58W IS SUPPORTING ISOLATED SHOWERS FROM 22N-25N BETWEEN 53W-62W. $$ HUFFMAN