000 AXNT20 KNHC 201040 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1015 UTC. ...SPECIAL FEATURES... HURRICANE BILL IS CENTERED NEAR 21.6N 60.3W OR ABOUT 285 NM NNE OF THE LEEWARD ISLANDS AND ABOUT 685 NM SSE OF BERMUDA MOVING NW AT 16 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 949 MB. MAXIMUM SUSTAINED WIND SPEED IS 110 KT WITH GUSTS TO 135 KT. SEE THE LATEST FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS TCMAT3/WTNT23 KNHC FOR MORE DETAILS. ALTHOUGH BILL HAS WEAKENED SLIGHTLY TO A CATEGORY 3 STORM IT IS NOT EXPECTED LONG LASTING AND COULD BECOME A CATEGORY 4 LATER TODAY OR FRIDAY. HURRICANE BILL CONTINUES TO DISPLAY A WELL DEFINED EYE WITH SCATTERED STRONG CONVECTION WITHIN 45 NM OF THE CENTER IN THE NW QUADRANT AND SCATTERED MODERATE/ISOLATED STRONG CONVECTION COVERING THE REMAINDER OF THE AREA FROM 20N-26N BETWEEN 56W-63W. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 22W/23W S OF 16N MOVING W NEAR 10 KT. WAVE IS NOW EMBEDDED WITHIN AN AREA DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY AND IS CLEARLY DEFINED MAINLY IN THE LOW/MID LEVELS. HOWEVER...IT REMAINS WITHIN AN AREA OF DRY UPPER AIR...THEREFORE NO ASSOCIATED SHOWERS/CONVECTION. TROPICAL WAVE REMAINS SLIGHTLY TILED DUE TO HURRICANE BILL EXTENDING FROM 15N50W TO 8N46W MOVING W 15-20 KT. WAVE REMAINS 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 88W S OF 19N MOVING W 10-15 KT. WAVE IS NOW INLAND OVER CENTRAL AMERICA AND THE YUCATAN PENINSULA. ...THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 15N16W 8N29W 7N39W 8N55W 10N62W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM 9N-12N E OF 21W TO INLAND OVER W AFRICA. SMALL CLUSTERS OF SCATTERED MODERATE CONVECTION ARE FROM 5N-12N BETWEEN 24W-43W. ...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 E GULF. ISOLATED SHOWERS CONTINUE TO DOT THE E GULF E OF 90W WHILE THE REMAINDER OF THE GULF IS BEGINNING TO CLEAR. CARIBBEAN SEA... AN UPPER LOW REMAINS JUST OFF THE YUCATAN NEAR 18N87W COVERING THE NW CARIBBEAN AND EXTENDING AN UPPER TROUGH N OVER THE E GULF OF MEXICO. AN UPPER RIDGE EXTENDS FROM E PANAMA TO E CUBA ALONG 78W PROVIDING UPPER LEVEL DIFFLUENCE TO GENERATE SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF A LINE FROM COLOMBIA NEAR 10N75W TO NICARAGUA NEAR 13N84W. 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 75W WITH SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS 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. A NARROW UPPER TROUGH EXTENDS THROUGH 32N66W TO THE TURKS AND CAICOS NEAR 23N75W GENERATING ISOLATED SHOWERS/THUNDERSTORMS FROM 27N-31N BETWEEN 68W-71W. OTHERWISE THE ATLC BASIN IS DOMINATED BY A SURFACE RIDGE ANCHORED IN THE W ATLC BY A 1021 MB HIGH NW OF BERMUDA AND IN THE E ATLC BY A 1026 MB HIGH W OF THE AZORES AND A 1024 MB HIGH NEAR 32N29W WITH A WEAKNESS OVER THE CENTRAL ATLC DUE TO HURRICANE BILL. $$ WALLACE