000 AXNT20 KNHC 230513 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT WED SEP 23 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0430 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 41W/42W S OF 18N MOVING WNW 15 KT. SATELLITE IMAGERY INDICATES A WELL DEFINED INVERTED-V STRUCTURE IN THE LOW LEVEL CLOUD PATTERN. AN ASCAT PASS FROM 0032 UTC ALSO CONFIRMS CYCLONIC FLOW IN THE VICINITY OF THE WAVE AXIS. A LARGE AREA OF SAHARAN DUST IS E OF THE AXIS MAINLY E OF 35W WHICH IS CURRENTLY CONFINING CONVECTION TO THE ITCZ. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 13N16W 8N22W 7N30W 10N40W 9N50W 11N64W. A BROAD AREA OF MID LEVEL CYCLONIC ROTATION IS ALONG THE COAST OF W AFRICA AND IS GENERATING A CLUSTER OF SCATTERED STRONG CONVECTION FROM 13N-15N BETWEEN 17W-19W. SMALL CLUSTERS OF ISOLATED MODERATE/STRONG CONVECTION ARE WITHIN 100 NM OF THE AXIS BETWEEN 16W-20W...AND 24W-48W. ...DISCUSSION... GULF OF MEXICO... AS OF 0300 UTC...A COLD FRONT EXTENDS ACROSS THE NW GULF FROM LAKE CHARLES LOUISIANA NEAR 30N93W ALONG 27N96W TO THE SRN TIP OF TEXAS NEAR 26N97W. A PRE-FRONTAL SURFACE TROUGH IS AHEAD OF THE FRONT FROM 29N90W ALONG 27N93W TO 24N96W. SURFACE CONVERGENCE NEAR THE FRONT/TROUGH IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS NW OF A LINE FROM 30N87W TO 24N98W. A WEAK SURFACE TROUGH EXTENDS THROUGH THE YUCATAN PENINSULA FROM 23N85W TO 18N85W IN THE NW CARIBBEAN. THE TROUGH IS SUPPORTING ISOLATED SHOWERS/THUNDERSTORMS S OF 23N BETWEEN 86W-88W. A LINE OF SHOWERS/THUNDERSTORMS PREVIOUSLY INLAND OVER FLORIDA HAS NOW MOVED OFF THE W COAST OF FLORIDA FROM 24N-29N ALONG 83W. THESE SHOWERS ARE MOST LIKELY LEFT OVER FROM AFTERNOON HEATING AND SEABREEZE CONVERGENCE OVER THE PENINSULA. IN THE UPPER LEVELS...A BROAD UPPER LEVEL RIDGE COVERS THE MAJORITY OF THE BASIN CENTERED OVER MEXICO NEAR 22N101W. SHOWERS/THUNDERSTORMS ASSOCIATED WITH THE FRONT IN THE NW GULF ARE ALSO ENHANCED BY DIFFLUENT FLOW BETWEEN THE UPPER LEVEL RIDGE AND AN UPPER LEVEL LOW OVER THE CENTRAL CONUS. A SHORTWAVE UPPER LEVEL TROUGH DIGS E-W ACROSS S FLORIDA AND THE STRAITS OF FLORIDA ENHANCING THE SHOWERS/THUNDERSTORMS ALONG THE W COAST OF FLORIDA. EXPECT THE FRONT TO STALL AND BECOME STATIONARY FOR THE NEXT COUPLE OF DAYS. CARIBBEAN SEA... AS OF 0300 UTC...A WEAK SURFACE TROUGH EXTENDS ACROSS THE NW CARIBBEAN FROM 23N85W TO 18N85W SUPPORTING A FEW ISOLATED SHOWERS/THUNDERSTORMS FROM 19N-23N W OF 86W. SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS CUBA N OF 19N BETWEEN 74W-84W. ISOLATED SHOWERS/THUNDERSTORMS ARE S AND E OF THIS ACTIVITY FROM 16N-19N BETWEEN 75W-84W...AND N OF 16N BETWEEN 66W-72W AFFECTING PUERTO RICO AND HISPANIOLA. THESE AREAS OF SHOWERS/THUNDERSTORMS ARE SUPPORTED BY UPPER LEVEL DIFFLUENT FLOW BETWEEN THE UPPER RIDGE OVER THE GULF OF MEXICO...A SHORTWAVE E-W UPPER TROUGH OVER THE BAHAMAS TO THE STRAITS OF FLORIDA EMBEDDED IN A LARGER AND MORE BROAD UPPER LEVEL TROUGH COVERING THE MAJORITY OF THE CARIBBEAN WITH AXIS E OF THE LESSER ANTILLES ALONG 59W. ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO ACROSS THE SW CARIBBEAN S OF 13N BETWEEN 72W-83W DUE TO SURFACE CONVERGENCE NEAR A 1006 MB LOW OVER COLOMBIA NEAR 9N74W...AND THE CLOSE PROXIMITY OF THE E PACIFIC ITCZ. THE REMAINDER OF THE CARIBBEAN REMAINS CALM UNDER THE INFLUENCE OF DRY AIR ALOFT. FRESH TRADEWINDS ARE ACROSS MUCH OF THE BASIN. ATLANTIC OCEAN... AS OF 0300 UTC...A WEAK SURFACE TROUGH LINES THE E COAST OF FLORIDA FROM 31N80W TO 27N80W SUPPORTING ISOLATED SHOWERS FROM 28N-32N BETWEEN 77W-80W. ISOLATED SHOWERS/THUNDERSTORMS ARE S OF 22N TO THE NRN CARIBBEAN BETWEEN 66W-81W DUE TO UPPER DIFFLUENT FLOW AROUND A SHORTWAVE E-W UPPER TROUGH ACROSS THE BAHAMAS EMBEDDED IN A LARGER AND MORE BROAD UPPER TROUGH ALONG 59W EXTENDING TO AN UPPER LEVEL LOW NEAR 31N64W. THE UPPER LEVEL LOW IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS N OF 26N BETWEEN 54W-63W. A FEW ISOLATED SHOWERS ARE ALSO E OF THE UPPER TROUGH AXIS FROM 17N-20N BETWEEN 54W-58W. A WEAKENING 1012 MB SURFACE LOW IS NEAR 16N49W. A SURFACE TROUGH EXTENDS THROUGH THE LOW FROM 21N47W TO 12N50W. SURFACE CONVERGENCE NEAR THE TROUGH IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM 20W-23W BETWEEN 45W-48W...AND A LINE OF ISOLATED SHOWERS FROM 25N40W TO 19N43W. THE REMAINDER OF THE ATLC IS RELATIVELY CALM UNDER THE INFLUENCE OF A BROAD SURFACE RIDGE. A BROAD UPPER LEVEL RIDGE DOMINATES THE BASIN E OF 50W E OF THE UPPER LEVEL TROUGH ALONG 59W. A LARGE AREA OF SAHARAN DUST IS ACROSS THE ERN ATLC MAINLY E OF 35W. $$ WALTON