000 AXNT20 KNHC 111727 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SAT JUL 11 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. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 36W/37W S OF 18N MOVING W NEAR 15 KT. SATELLITE IMAGERY INDICATES THAT THIS WAVE COINCIDES WITHIN A BROAD AREA OF LOWER LEVEL CYCLONIC TURNING. ANY DEEP CONVECTION IS ABSENT ACROSS MOST OF THE AREA BEING SUPPRESSED BY LOW/MID LEVEL DRY SAHARAN AIR. TOPICAL WAVE EXTENDS FROM 20N69W TO 10N73W MOVING W NEAR 20 KT. THIS WAVE IS MOVING BENEATH A BROAD UPPER TROUGH OVER THE CENTRAL CARIBBEAN ENHANCING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS MAINLY S OF 22N TO OVER HISPANIOLA AND TO THE N OVER THE TURKS AND CAICOS BETWEEN 69W-72W. ISOLATED SHOWERS ARE IN THE COASTAL WATERS OVER THE CARIBBEAN N OF 17N BETWEEN 68W-72W. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 10N13W 8N25W 9N36W 6N49W 6N58W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 45/60 NM OF LINE FROM 11N18W TO INLAND OVER THE S PORTION OF SENEGAL AND WITHIN 60 NM ALONG THE COAST OF GUINEA FROM 9.5N TO THE BORDER OF SIERRA LEONE. ISOLATED/SCATTERED MODERATE CONVECTION IS WITHIN 90 NM OF LINE FROM THE COAST OF SIERRA LEONE NEAR 7N13W TO 6N23W. ...DISCUSSION... GULF OF MEXICO... A LARGE UPPER HIGH OVER THE S CENTRAL PLAINS IS PROVIDING NLY FLOW AND ADVECTING DRY AIR SOUTHWARD OVER THE NW GULF...HELPING TO SUSTAIN A SURFACE RIDGE ALONG 30N. A CUT-OFF UPPER LOW IS OVER THE SW GULF JUST N OF THE YUCATAN NEAR 24N87W. INSTABILITY NEAR AND E OF THE UPPER LOW IS GENERATING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS MAINLY S OF 27N E OF 90W...AS REVEALED BY DOPPLER RADAR AND LIGHTNING DATA. THE UPPER LOW EXTENDS AN UPPER TROUGH WESTWARD TO THE COAST OF MEXICO IN THE W BAY OF CAMPECHE. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE ALSO OCCURRING ASSOCIATED WITH UPPER DIFFLUENCE AND LOW LEVEL CONVERGENCE OVER THE SW GULF WITHIN A 60 NM RADIUS OF 23N93.5W AND IN THE W BAY OF CAMPECHE WITHIN 60 NM ALONG THE COAST OF MEXICO S OF 23N W OF 95W. THE WEAK RIDGE ACROSS N FLORIDA AND THE NE GULF WILL SHIFT S TO ACROSS THE CENTRAL GULF BY MON AND REMAIN THROUGH WED. CARIBBEAN SEA... THE UPPER LOW IN THE GULF OF MEXICO COVERS THE NW CARIBBEAN GENERATING SCATTERED SHOWERS/THUNDERSTORMS N OF 20N TO OVER W CUBA W OF 80W TO THE COAST OF THE YUCATAN PENINSULA AND THROUGH THE YUCATAN CHANNEL. A SECOND UPPER LOW IS OVER E CUBA WITH AN UPPER TROUGH EXTENDING S ACROSS THE CENTRAL CARIBBEAN. MODERATE/ STRONG TRADE WINDS ARE ACROSS THE REGION BETWEEN THE SUBTROPICAL SURFACE RIDGE OVER THE CENTRAL ATLC AND A TYPICAL BROAD TROUGH OVER NORTHERN SOUTH AMERICA...WITH THE STRONGEST FLOW NEAR THE COAST OF COLOMBIA. THESE WINDS WILL REMAIN STRONG OVER THE NEXT SEVERAL DAYS AS THE SUBTROPICAL RIDGE REMAINS. UPPER LEVEL DIFFLUENCE AND LOW LEVEL CONVERGENCE OVER THE SW CARIBBEAN IS GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 17N BETWEEN 79W-85W INCLUDING PORTIONS OF CENTRAL AMERICA. ATLANTIC OCEAN... A SURFACE TROUGH IS OVER THE W ATLC EXTENDING FROM 26N70W ACROSS THE BAHAMAS TO THE COAST OF CUBA NEAR BAHIA DE NIPE WITH THE UPPER LOW OVER E CUBA AND AN UPPER RIDGE OVER THE W ATLC PROVIDING UPPER LEVEL DIFFLUENCE TO GENERATE SCATTERED SHOWERS/THUNDERSTORMS W OF THE TROUGH AXIS TO A LINE FROM 26N73W TO CUBA NEAR SAGUA LA GRANDE AND SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 75 NM EITHER SIDE OF THE REMAINDER OF THE TROUGH AXIS. A SURFACE TROUGH...PREVIOUSLY A PORTION OF A TROPICAL WAVE...IS TO THE E EXTENDING FROM 25N62W TO 22N65W WITH CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 90/120 NM OF THE TROUGH AXIS. THIS TROUGH COULD EXTENDING AS FAR N AS 30N61W AS THERE ARE NOW SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 60 NM LINE FROM 27N60W TO 30N61W. THE REMAINDER OF THE BASIN IS RATHER TRANQUIL THIS AFTERNOON ESPECIALLY E OF 60W WITH DRY SAHARAN AIR EXTENDING OVER THE AREA S OF 29N TO 45W. $$ WALLACE