000 AXNT20 KNHC 200553 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT THU AUG 20 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 0415 UTC. ...SPECIAL FEATURES... HURRICANE BILL IS CENTERED NEAR 20.7N 58.9W OR ABOUT 275 NM NE OF THE LEEWARD ISLANDS AND ABOUT 765 NM SSE OF BERMUDA MOVING NW AT 15 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 945 MB. MAXIMUM SUSTAINED WIND SPEED IS 115 KT WITH GUSTS TO 140 KT. SEE THE LATEST FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS TCMAT3/WTNT23 KNHC FOR MORE DETAILS. HURRICANE BILL DISPLAYED A WELL DEFINED EYE WITH SCATTERED STRONG CONVECTION WITHIN 90 NM OF THE CENTER IN THE SW QUADRANT AND SCATTERED MODERATE/ISOLATED STRONG CONVECTION COVERING THE REMAINDER OF THE AREA FROM 18N-24N BETWEEN 55W-61W. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 22W S OF 16N MOVING W 10 KT. WAVE IS AT THE LEADING EDGE OF AN AREA DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY AND IS CLEARLY DEFINED MAINLY IN THE LOW/MID LEVELS. HOWEVER...DUE TO DRY UPPER AIR THERE IS NO ASSOCIATED CONVECTION WITH POSSIBLE ISOLATED SHOWERS 90 NM OF THE WAVE AXIS. TROPICAL WAVE REMAINS SLIGHTLY TILED DUE TO HURRICANE BILL EXTENDING FROM 15N46W TO 8N44W MOVING W 15-20 KT. WAVE IS CLEARLY EMBEDDED WITHIN AN AREA DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY AND IS WELL DEFINED IN THE LOW/MID LEVELS. HOWEVER...DUE TO DRY UPPER AIR THERE IS NO ASSOCIATED SHOWERS/CONVECTION. TROPICAL WAVE IS ALONG 85W/86W S OF 19N MOVING W 10-15 KT. WAVE IS CLEARLY DEFINED IN THE E PACIFIC REGION BUT DUE TO DRY STABLE AIR OVER THE CARIBBEAN IS NOT PRODUCING ANY SHOWERS/CONVECTION IN THE ATLC/CARIBBEAN BASIN. ...THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 13N15W 12N24W 9N33W 13N43W 10N49W 11N56W 9N62W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE WITHIN 60/75 NM OF LINE FROM 8N30W 5N37W. CLUSTERS OF SCATTERED MODERATE CONVECTION ARE INLAND AND WITHIN 60/75 NM ALONG THE COAST OF W AFRICA BETWEEN 8N-13N. SMALL CLUSTERS OF SIMILAR CONVECTION ARE WITHIN 75 NM OF THE ITCZ AXIS BETWEEN 24W-35W. ...DISCUSSION... GULF OF MEXICO... BROAD UPPER RIDGE EXTENDS FROM OVER MEXICO NEAR TUXPAN NNE TO OVER THE LOWER MISSISSIPPI VALLEY TO THE CAROLINAS WHILE A UPPER LOW IN THE CARIBBEAN EXTENDS AN UPPER TROUGH OVER THE REMAINDER OF THE GULF. THE SURFACE RIDGE FROM THE W ATLC IS CONTINUES TO BUILD ACROSS THE N GULF WITH A WEAKENING SURFACE TROUGH EXTENDING FROM 28N96W TO NW YUCATAN. SCATTERED SHOWERS/ THUNDERSTORMS ARE N OF ERN CUBA WITHIN 30/45 NM OF LINE FROM 24N83W TO 23N85W. ISOLATED SHOWERS CONTINUE TO DOT THE REMAINDER OF THE GULF MAINLY WITHIN N OF 27N AND WITHIN 120 NM OF THE SURFACE TROUGH. CARIBBEAN SEA... AN UPPER LOW IS CENTERED JUST OFF THE YUCATAN NEAR 19N86W COVERING THE NW CARIBBEAN AND EXTENDING AN UPPER TROUGH N OVER THE E GULF OF MEXICO. AN UPPER RIDGE EXTENDS FROM E PANAMA ALONG 79W N TO 15N PROVIDING UPPER LEVEL DIFFLUENCE TO GENERATE SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 12N W OF 75W FROM COLOMBIA TO CENTRAL AMERICA. SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS ARE OBSERVED OVER S HAITI AND WITHIN 60 NM ALONG THE COAST IN THE ADJACENT COASTAL WATERS. FRESH TO STRONG EASTERLY TRADE WINDS CONTINUE ACROSS THE AREA. DRY STABLE AIR IS ACROSS THE REMAINDER OF THE AREA E OF 80W LIMITING ANY DEEP LAYERED SHOWERS. HOWEVER...FAST LOW LEVEL ISOLATED SHOWERS ARE ACROSS THE E CARIBBEAN E OF 69W WITH SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS MOVING SW AS WELL AS HIGHER SEAS AND SWELLS ACROSS THE LEEWARD ISLANDS TO PUERTO RICO ALL COMPLIMENTS OF HURRICANE BILL AS IT CONTINUES TO MOVE NW OF THE ISLANDS. ATLANTIC OCEAN... THE MAIN FOCUS THIS MORNING FOR THE ATLC IS HURRICANE BILL. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS LINGER OFF THE COAST OF FLORIDA FROM 25N-31N BETWEEN 79W-80W. THE NARROW UPPER TROUGH EXTENDS THROUGH 32N70W TO THE BAHAMAS NEAR 25N76W PROVIDING SUPPORT FOR A SURFACE TROUGH THAT EXTENDS FROM 31N64W TO 28N66W GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 28N-31N BETWEEN 65W-68W. OTHERWISE THE ATLC BASIN IS DOMINATED BY A SURFACE RIDGE ANCHORED IN THE W ATLC BY A 1021 MB HIGH BETWEEN BERMUDA AND NORTH CAROLINA COAST AND BY A 1025 MB HIGH S OF THE AZORES WITH A WEAKNESS OVER THE CENTRAL ATLC DUE TO HURRICANE BILL. $$ WALLACE