000 AXNT20 KNHC 171745 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU SEP 17 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 1700 UTC. ...TROPICAL WAVES... TROPICAL WAVE PREVIOUSLY ALONG 23W/24W HAS BEEN RELOCATED ALONG 19W S OF 18N MOVING W 10-15 KT. WHILE A BURST OF CONVECTION WITH ASSOCIATED CYCLONIC FLOW DID EMERGE OFF THE AFRICAN COAST YESTERDAY...IT APPEARS THAT THE ACTUAL WAVE AXIS FOLLOWED BEHIND IT. A 17/0000 UPPER AIR SOUNDING FROM DAKAR SENEGAL INDICATES A STRONGER AND MORE CONCLUSIVE SURFACE WIND SHIFT INDICATING THE WAVE PASSAGE...JUSTIFYING THE RELOCATION. SCATTERED STRONG CONVECTION IS FROM 13N-15N BETWEEN 18W-20W. ISOLATED MODERATE CONVECTION IS FROM 8N-11N BETWEEN 17W-20W. TROPICAL WAVE IS ALONG 83W S OF 19N MOVING W NEAR 12 KT. THE WAVE LIES WITHIN A BROAD AREA OF DEEP LAYER MOISTURE. NO DEEP CONVECTION IS CURRENTLY ASSOCIATED WITH THE WAVE. HOWEVER...ISOLATED SHOWERS ARE WITHIN 100 NM OF THE WAVE AXIS. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 12N20W 9N25W 11N32W 7N42W 9N52W 10N62W. ISOLATED MODERATE CONVECTION IS FROM 6N-10N BETWEEN 25W-40W. ...DISCUSSION... GULF OF MEXICO... AS OF 1500 UTC...A COLD FRONT EXTENDS THROUGH LOUISIANA TO NEAR 29N92W INTO THE NW GULF EXTENDING TO SRN TEXAS NEAR 27N97W. SCATTERED SHOWERS/THUNDERSTORMS ARE WITHIN 75 NM AHEAD OF THE FRONT. A PRE-FRONTAL SURFACE TROUGH IS ANALYZED FROM THE FLORIDA PANHANDLE NEAR 30N86W TO 23N92W. SCATTERED SHOWERS/THUNDERSTORMS ARE WITHIN 50 NM EITHER SIDE OF THE TROUGH AXIS. ISOLATED SHOWERS ALSO LINE THE SW COAST OF FLORIDA FROM 25N-28N BETWEEN 82W-83W. THE FRONTAL SYSTEM IS SUPPORTED BY AN UPPER LEVEL TROUGH ACROSS THE CENTRAL UNITED STATES EXTENDING ACROSS THE WRN AND CENTRAL GULF. THE SHOWER ACTIVITY ALONG THE SURFACE TROUGH IS ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL TROUGH OVER THE CENTRAL CONUS AND AN UPPER LEVEL RIDGE OVER THE SE GULF AND INTO THE WRN ATLC. CARIBBEAN SEA... THE NW CARIBBEAN REMAINS FAIRLY CALM DUE TO MODERATE DRY AIR ALOFT AROUND AN UPPER LEVEL RIDGE EXTENDING FROM THE WRN ATLC INTO THE NW CARIBBEAN. HOWEVER...ISOLATED SHOWERS ARE WITHIN 100 NM OF THE TROPICAL WAVE ALONG 83W...SEE ABOVE. SCATTERED SHOWERS/THUNDERSTORMS ARE IN THE FAR SW CARIBBEAN S OF 11N BETWEEN 76W-81W DUE TO SURFACE CONVERGENCE NEAR THE E PACIFIC ITCZ. ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS ARE IN THE CENTRAL AND E CARIBBEAN FROM 13N-18N BETWEEN 67W-78W. SCATTERED SHOWERS/THUNDERSTORMS ARE FROM 12N-17N BETWEEN 63W-66W. BOTH AREAS OF ACTIVITY ARE ASSOCIATED WITH AN UPPER LEVEL LOW NEAR 15N74W. MODERATE TRADE WINDS REMAIN ACROSS MUCH OF THE BASIN. EXPECT THE TROPICAL WAVE ALONG 83W TO CONTINUE W AND OUT OF THE BASIN BY TOMORROW. ATLANTIC OCEAN... A SURFACE TROUGH EXTENDS FROM A 1009 MB LOW NEAR 35N69W ENTERING THE DISCUSSION AREA NEAR 32N71W CONTINUING TO THE CENTRAL BAHAMAS NEAR 25N76W. ISOLATED SHOWERS ARE WITHIN 75 NM EITHER SIDE OF THE TROUGH AXIS FROM 23N-28N. SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS ARE WITHIN 150 NM AHEAD OF THE TROUGH N OF 28N. SHOWERS ALONG THE TROUGH ARE ALSO SUPPORTED BY UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL TROUGH OVER THE NW ATLC AND AN UPPER LEVEL RIDGE OVER THE SW ATLC EXTENDING FROM 33N62W ACROSS THE BAHAMAS AND CUBA TO THE NW CARIBBEAN. A SURFACE TROUGH...REMNANT OF FRED...IS ANALYZED FROM 21N59W TO 27N61W. SURFACE CONVERGENCE NEAR THE TROUGH IS SUPPORTING ISOLATED SHOWERS 21N-26N BETWEEN 59W-63W. AN UPPER LEVEL LOW NEAR 20N53W IS ALSO ENHANCING THE SHOWERS NEAR THE SURFACE TROUGH AS WELL AS AN AREA OF SCATTERED SHOWERS/THUNDERSTORMS FROM 20N-26N BETWEEN 50W-56W. THE REMAINDER OF THE ATLC IS DOMINATED BY A BROAD SURFACE RIDGE ANCHORED BY A 1027 MB HIGH NEAR 35N46W. IN THE UPPER LEVELS...AN UPPER LEVEL TROUGH DOMINATES THE NE ATLC CENTERED NEAR 28N26W. A BROAD UPPER LEVEL RIDGE DOMINATES THE TROPICAL ATLC ENHANCING CONVECTION ALONG THE ITCZ. $$ WALTON