000 AXNT20 KNHC 252335 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT WED JUL 25 2007 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND THE 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...TROPICAL WAVES... TROPICAL WAVE WILL BE INTRODUCED ALONG 27W S OF 17N MOVING W ABOUT 15 KT. THERE ARE SEVERAL INDICATIONS OF THIS WAVE. 1...A WEAK SIGNAL IS NOTED IN THE DAKAR SOUNDING BETWEEN 00Z AND 12Z ON THE 23RD. 2...A SIGNAL IS NOTED IN THE SAL SOUNDING BETWEEN 12Z ON THE 24TH AND 00Z ON THE 25TH MAINLY IN 850-900 MB LEVEL. 3...A 1946Z QUIKSCAT PASS SHOWS A WEAK CIRCULATION CENTERED W OF THE CAPE VERDES NEAR 13N27W. SCATTERED MODERATE CONVECTION IS FROM 12N-15N BETWEEN 25W-28W. TROPICAL WAVE ROUGHLY ALONG 40W/41W S OF 15N MOVING W 10-15 KT. SATELLITE IMAGERY INDICATES AN ELONGATED E/W ZONE OF LOW-LEVEL CYCLONIC TURNING EXTENDING ABOUT 300-400 NM EITHER SIDE OF THE WAVE AXIS ALONG 11N. THE WAVE IS ALSO EVIDENT IN THE SSM/I- DERIVED TPW PRODUCT WITH SOME CYCLONIC TURNING AND A SURGE OF MOISTURE S OF 15N. TROPICAL WAVE LOCATED OVER THE FAR SE CARIBBEAN ALONG 64W S OF 15N MOVING W 20-25 KT. UPPER LEVEL SOUNDINGS FROM TRINIDAD AND GUADELOUPE INDICATE THAT THE WAVE PASSED THOSE STATIONS JUST BEFORE 12Z THIS MORNING AND THE TPW PRODUCT NOW INDICATES THAT IT HAS PROBABLY REACHED ABOUT 65W. A FEW TSTMS DEVELOPED NEAR THE APEX OF THE WAVE AXIS EARLIER IN THE DAY BUT MOST OF THIS ACTIVITY HAS SINCE DISSIPATED. TROPICAL WAVE MOVING INLAND ACROSS THE YUCATAN PENINSULA AND THE SE GULF OF MEXICO ALONG 89W S OF 24N MOVING W 20 KT. SATELLITE IMAGERY INDICATES THAT THE WAVE IS ASSOCIATED WITH THE LEADING EDGE OF A MOISTURE SURGE WITH ENHANCED CLOUDINESS AND CONVECTION. SCATTERED MODERATE CONVECTION IS CURRENTLY FOCUSED FROM 20N-25N BETWEEN 84W-91W OVER THE S/CENTRAL GULF OF MEXICO. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 14N17W 12N32W 7N43W 8N55W 8N62W. WIDELY SCATTERED MODERATE CONVECTION OFF THE COAST OF SENEGAL FROM 12N-16N BETWEEN 16W-21W. SCATTERED MODERATE FROM 9N-14N BETWEEN 29W-36W. ...DISCUSSION... GULF OF MEXICO... A WEAK SURFACE RIDGE HAS BUILT IN ACROSS GULF REGION WITH THE MAIN AXIS STRETCHING FROM N/CENTRAL FLORIDA TO THE TEXAS/MEXICO BORDER. THE UPPER LEVEL TROUGH WHICH HAS BEEN SITUATED OVER THE AREA THE PAST FEW DAYS HAS RETROGRADED NW OVER TEXAS AND HAS BEEN REPLACED BY BROAD ANTICYCLONIC FLOW WITH THE UPPER HIGH CENTERED JUST E OF CANCUN MEXICO. A SERIES OF TROPICAL WAVES MOVING ACROSS THE SRN PART OF THE GULF HAS ALREADY BROUGHT IN LOW-LEVEL MOISTURE AND NOW THE SOUTHWESTERLY UPPER FLOW IS BRINGING IN MORE MID/UPPER LEVEL MOISTURE FROM THE PACIFIC. AS A RESULT...PRECIPITABLE WATER VALUES ARE WELL OVER 2.0" OVER THE WRN GULF. LOW-LEVEL SPEED CONVERGENCE OF EASTERLY WINDS OVER THE SW GULF SERVED AS THE TRIGGERING MECHANISM FOR SCATTERED MODERATE CONVECTION TO DEVELOP...NOW EXTENDING FROM 21N-25N BETWEEN 88W-95W AND MERGING WITH TSTM ACTIVITY ASSOCIATED WITH THE TROPICAL WAVE ALONG 88W. SCATTERED SHOWERS/TSTMS ARE ALSO LOCATED N OF 25N TO THE N GULF COAST W OF 87W TO THE W GULF COAST. THE AIR MASS OVER THE E GULF IS MUCH DRIER AND IS DOMINATED BY CIRRUS EMANATING FROM THE CONVECTION OVER THE W GULF. CARIBBEAN... AS MENTIONED ABOVE...A LARGE UPPER HIGH IS CENTERED JUST E OF CANCUN MEXICO AND ITS CIRCULATION COVERS MUCH OF THE W CARIBBEAN W OF 75W. THIS AREA ALSO HAS THE HIGHEST MOISTURE VALUES IN THE WAKE OF THE TROPICAL WAVE ALONG 88W. LOW-LEVEL TRADE CONVERGENCE AND MULTIPLE OUTFLOW BOUNDARY COLLISIONS ARE PRODUCING SCATTERED MODERATE CONVECTION FROM 15N-20N BETWEEN 76W-83W. SOME OF THESE TSTMS ARE ORIGINATING INLAND OVER CUBA AND JAMAICA AND ARE MOVING WWD IN THE PREVAILING FLOW. FARTHER E...AN INVERTED UPPER TROUGH EXTENDS FROM PUERTO RICO SW TO THE GUAJIRA PENINSULA WHILE A RIDGE AXIS POKES W ACROSS THE WINDWARD ISLANDS INTO THE SE CARIBBEAN. THE BULK OF THE AREA E OF 75W IS UNDER FAIRLY DRY CONDITIONS EXCEPT FOR A FEW SHOWERS/TSTMS OCCASIONALLY DEVELOPING NEAR THE SE CARIBBEAN TROPICAL WAVE. ATLANTIC... AN EXTENSIVE AREA OF HIGH PRES COVERS MUCH OF THE ATLC WITH A 1028 MB HIGH CENTERED NEAR 36N42W. HOWEVER...A WEAK SURFACE TROUGH DOES LIE OVER THE W ATLC WATERS FROM 31N75W SW TO NEAR SE FLORIDA. BROAD UPPER LEVEL TROUGHING OVER THE ERN U.S. AND AN UPPER RIDGE OVER THE BAHAMAS ARE PRODUCING ENOUGH DIFFLUENCE FOR SCATTERED MODERATE CONVECTION TO DEVELOP E OF THE SURFACE TROUGH FROM 26N-31N BETWEEN 69W-76W. FARTHER E...A CLOSED MID/UPPER LOW IS CENTERED NEAR 31N55W AND IS CAUSING ISOLATED SHOWERS/TSTMS N OF 28N BETWEEN 50W-54W. THE E AND CENTRAL ATLC ARE DOMINATED BY A LARGE UPPER RIDGE WHICH EXTENDS FROM WRN SAHARA SW TO THE WINDWARD ISLANDS. WATER VAPOR IMAGERY AND TPW LOOPS SHOW THAT THE DEEPEST MOISTURE IS LIMITED S OF 15N IN THE TROPICS WHILE MODERATE SUBSIDENCE PREVAILS FARTHER N. $$ BERG