000 AXNT20 KNHC 231807 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SUN AUG 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1630 UTC. ...SPECIAL FEATURES... AS OF 23/1800 UTC...THE CENTER OF HURRICANE BILL IS NEAR 44.4N 62.5W OR ABOUT 60 MILES...95 KM...EAST-SOUTHEAST OF HALIFAX NOVA SCOTIA. BILL IS MOVING TO THE NE NEAR 29 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 970 MB. MAXIMUM SUSTAINED WIND SPEEDS ARE 70 KT WITH GUSTS TO 85 KT. PLEASE READ THE FORECAST/ADVISORY UNDER AFOS/ WMO HEADERS TCMAT3/WTNT23 KNHC AND THE PUBLIC ADVISORY UNDER TCPAT3/WTNT33 KNHC FOR MORE DETAILS. NUMEROUS SHOWERS/THUNDERSTORMS ARE FROM 41N-49N BETWEEN 53W-65W TO THE NE OF THE CENTER OF BILL. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 21W S OF 17N MOVING W 10-15 KT. VISIBLE SATELLITE IMAGERY AND SATELLITE DERIVED WINDS INDICATE GOOD LOW/MID-LEVEL CYCLONIC FLOW IN THE VICINITY OF THE WAVE AXIS. THIS WAVE ALSO COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 10N-16N BETWEEN 23W-27W. SIMILAR ACTIVITY IS FROM 14N-16N BETWEEN 18W-20W. A TROPICAL WAVE EXTENDS FROM 17N51W TO 9N48W MOVING W 20-25 KT. AN INVERTED-V FEATURE IS APPARENT IN THE LOW-LEVEL CLOUD STRUCTURE IN VISIBLE SATELLITE IMAGERY. THE WAVE ALSO COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 14N-15N BETWEEN 45W-54W. A TROPICAL WAVE IS ALONG 68W S OF 18N MOVING W NEAR 15 KT. WAVE POSITION IS BASED MAINLY ON CONTINUITY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 11N-13N BETWEEN 67W-72W. THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 11N14W 13N22W 9N33W 15N48W 12N56W 11N64W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 13N-18N BETWEEN 14W-18W. SIMILAR ACTIVITY IS FROM 10N-12N BETWEEN 60W-64W. ...DISCUSSION... THE GULF OF MEXICO... A COLD FRONT DIPS ACROSS THE N AND CENTRAL GULF EXTENDING FROM N FLORIDA NEAR 31N81W TO 25N88W AND UP TO THE TEXAS COAST TO NEAR 29N95 WHERE IT CONTINUES AS A STATIONARY FRONT INTO N TEXAS. THE FRONT IS SUPPORTED BY AN UPPER LEVEL TROUGH ACROSS THE ERN CONUS WHICH EXTENDS INTO THE NRN GULF TO NEAR 24N92W. SHOWERS/THUNDERSTORMS ARE WITHIN 100 NM EITHER SIDE OF THE FRONT. A WEAK 1015 MB SURFACE HIGH IS IN THE SW GULF NEAR 25N94W. AN 1148 UTC QUIKSCAT PASS CONFIRMED THE LOCATION OF THE HIGH. A SMALL UPPER LEVEL LOW IS OVER THE YUCATAN PENINSULA NEAR 19N93W SUPPORTING A FEW ISOLATED SHOWERS/THUNDERSTORMS IN THE SRN BAY OF CAMPECHE S OF 20N W OF 93W. EXPECT THE COLD FRONT TO DISSIPATE TONIGHT AS A RIDGE BUILDS BACK ACROSS THE AREA. THE CARIBBEAN SEA... A BROAD UPPER LEVEL RIDGE DOMINATES THE CARIBBEAN CENTERED OVER HAITI NEAR 20N73W. UPPER LEVEL DIFFLUENCE BETWEEN THIS RIDGE AND THE UPPER LEVEL LOW OVER THE YUCATAN PENINSULA NEAR 19N93W IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS IN THE SW CARIBBEAN S OF 16N W OF 80W INCLUDING PORTIONS OF COSTA RICA AND NICARAGUA. SHOWERS/THUNDERSTORMS ARE ALONG THE SE CARIBBEAN ASSOCIATED WITH THE TROPICAL WAVE ALONG 68W...SEE ABOVE. MODERATE TO FRESH TRADEWINDS ARE ACROSS MUCH OF THE BASIN WITH STRONGER WINDS IN THE E CARIBBEAN AND NEAR THE COAST OF COLOMBIA. EXPECT THE WAVE ALONG 68W TO MOVE WWD ACROSS THE CENTRAL CARIBBEAN LATER TONIGHT. THE ATLANTIC OCEAN... A COLD FRONT ACROSS NRN FLORIDA EXTENDS TO A 1010 MB SURFACE LOW IN COASTAL SOUTH CAROLINA NEAR 33N80W. SCATTERED SHOWERS/THUNDERSTORMS ARE WITHIN 250 NM AHEAD OF THE FRONT AFFECTING THE FLORIDA PENINSULA AND THE FAR NW BAHAMAS. THIS ACTIVITY IS ALSO SUPPORTED BY UPPER LEVEL DIFFLUENCE BETWEEN THE STRONG UPPER LEVEL TROUGH OVER THE ERN CONUS AND AN UPPER LEVEL RIDGE THAT EXTENDS FROM AN UPPER LEVEL HIGH OVER HAITI NEAR 20N73W. TO THE E OF THE RIDGE A STRONG UPPER LEVEL LOW IS CENTERED NEAR 25N56W AND IS SUPPORTING ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS FROM 20N-29N BETWEEN 50W-62W. ELSEWHERE ACROSS THE ATLC...A BROAD SURFACE RIDGE DOMINATES ANCHORED BY A 1028 MB HIGH NEAR 36N47W. ACROSS THE TROPICAL ATLC...AN UPPER LEVEL HIGH IS CENTERED NEAR 18N39W ENHANCING CONVECTION ALONG THE TROPICAL WAVE NEAR 50W. $$ WALTON