000 AXNT20 KNHC 211800 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1745 UTC. ...SPECIAL FEATURES... AS OF 1800 UTC...HURRICANE BILL IS CENTERED NEAR 28.5N 66.8W ABOUT 255 NM...465 KM...SOUTH-SOUTHWEST OF BERMUDA AND ABOUT 6O5 NM...1115 KM...SOUTHEAST OF CAPE HATTERAS NORTH CAROLINA. MOVING NW OR 325 DEG AT 16 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 957 MB. MAXIMUM SUSTAINED WIND SPEEDS ARE 100 KT WITH GUSTS TO 120 KT. BILL IS A CATEGORY THREE HURRICANE ON THE SAFFIR-SIMPSON SCALE. SOME FLUCTUATIONS IN INTENSITY ARE LIKELY THE REST OF TODAY AND SATURDAY. A TROPICAL STORM WARNING AND A HURRICANE WATCH ARE IN EFFECT FOR BERMUDA. RADAR IMAGERY FROM BERMUDA INDICATES THAT SOME RAINBANDS ARE ALREADY AFFECTING THE ISLAND. SEE THE LATEST FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS TCMAT3/WTNT23 KNHC FOR MORE DETAILS. NUMEROUS STRONG CONVECTION IS WITHIN 80 NM OF CENTER OF BILL. LARGE SWELLS GENERATED BY THIS HURRICANE ARE AFFECTING PUERTO RICO...HISPANIOLA...THE BAHAMAS...AND BERMUDA...AND SHOULD BEGIN AFFECTING MOST OF THE U.S. EAST COAST AND THE ATLANTIC MARITIMES OF CANADA DURING THE NEXT DAY OR TWO. THESE SWELLS WILL LIKELY CAUSE EXTREMELY DANGEROUS SURF AND LIFE-THREATENING RIP CURRENTS. THE METEOROLOGICAL SERVICE OF THE DOMINICAN REPUBLIC REPORTED SOME COASTAL FLOODING WITH DAMAGE TO ROADS AND HOUSES DUE TO HIGH WAVES ALONG THE NORTH COAST OF THE ISLAND. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 28W/29W S OF 17N MOVING W NEAR 15 KT. THE WAVE COINCIDES WITH A DEEP LAYERED MOISTURE MAXIMUM OBSERVED IN THE TOTAL PRECIPITABLE WATER IMAGERY. AN INCREASE IN MODERATE CONVECTION IS NOTED JUST AHEAD OF THE WAVE AXIS WITH SOME CYCLONIC TURNING NEAR 12N. THIS IS CONFIRMED BY ASCAT DATA FROM AROUND 1100 UTC AND VIS SATELLITE IMAGERY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 11N-14N BETWEEN 29W-33W. A TROPICAL WAVE IS ALONG 56W S OF 16N MOVING W NEAR 20 KT. CONVECTION HAS ALSO INCREASED EITHER SIDE OF THE WAVE AXIS PARTICULARLY S OF 12N. THIS WAVE LIES WITHIN A BROAD AREA OF DEEP LAYER MOISTURE OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS NOTED FROM 8N-12N BETWEEN 52W-57W. ...THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 13N17W 10N35W 10N50W 9N61W. A CLUSTER OF NUMEROUS MODERATE/ISOLATED STRONG CONVECTION HAS MOVED OFF THE AFRICA COAST FROM 10N-13N BETWEEN 18W-21W. THIS CONVECTIVE ACTIVITY IS MOST LIKELY ASSOCIATED WITH NEXT TROPICAL WAVE. IN ADDITION TO CONVECTION ASSOCIATED WITH THE TROPICAL WAVES...SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 7N-11N BETWEEN 36W-52W. ...DISCUSSION... GULF OF MEXICO... A WEAK SURFACE RIDGE IS ACROSS THE GULF OF MEXICO BUILDING FROM THE W ATLC WITH A 1019 MB HIGH NEAR 29N88W AT 1500 UTC. A WEAK SFC TROUGH HAS DEVELOPED OVER THE SW PORTION OF THE AREA GENERATING SOME SHOWER AND TSTM ACTIVITY. A QSCAT PASS SHOWS SE WINDS OF 15 TO 20 KT BEHIND THE TROUGH AXIS WHILE NOAA BUOY 42005 IN THE SW GULF IS REPORTING SUSTAINED WINDS OF 21 KT. SCATTERED SHOWERS AND TSTMS ARE ALSO NOTED OVER THE REGION N OF 27N E OF 93W. A DIFFLUENT PATTERN ALOFT...AHEAD OF A DEEP LAYER TROUGH DIGGING S OVER THE E CONUS AND THE NORTHERN GULF WATERS...IS ENHANCING THIS ACTIVITY. AN UPPER LEVEL RIDGE COVERS MOST OF THE GULF EXTENDING FROM AN UPPER LEVEL HIGH CENTER OVER MEXICO NEAR 23N104W. THE UPPER-LEVEL LOW THAT WAS MOVING IN TANDEM WITH THE REMNANTS OF ANA A FEW DAYS AGO IS NOW CENTERED OVER NORTHERN BELIZE. IT IS INDUCING SCATTERED SHOWERS AND TSTMS OVER THE NW CARIBBEAN. THE SE GULF IS EXPERIENCING GENERALLY FAIR WEATHER UNDER THE INFLUENCE OF DRY AIR AND SUBSIDENCE ALOFT. LOOKING AHEAD...THE RIDGE ACROSS THE N GULF IS FORECAST TO MOVE S TO ALONG 25N BY SAT. A WEAK FRONTAL TROUGH IS EXPECTED TO EXTEND ACROSS THE GULF N OF 27N DURING THE UPCOMING WEEKEND. CARIBBEAN SEA... AS PREVIOUSLY MENTIONED...AN UPPER-LEVEL LOW IS GENERATING SCATTERED SHOWERS AND TSTMS OVER THE NW CARIBBEAN...INCLUDING THE GULF OF HONDURAS. SIMILAR CONVECTIVE ACTIVITY IS ALSO NOTED OVER THE SW CARIBBEAN S OF 12N AND OVER PARTS OF PANAMA AND COSTA RICA. THIS ACTIVITY IS ASSOCIATED WITH THE COLOMBIAN OR PANAMANIAN LOW...ANALYZED 1008 MB NEAR 10N77W. LOW-TOPPED TRADE WIND SHOWERS DOT THE REMAINDER OF THE AREA UNDER DRY SUBSIDENCE AIR ALOFT. MOISTURE ASSOCIATED WITH THE TROPICAL WAVE ALONG 56W IS ALREADY REACHING THE WINDWARD ISLANDS WITH BARBADOS REPORTING A FEW PASSING LIGHT SHOWERS. NARROW LINES OF SHOWERS ARE ACROSS THE FAR NE ISLANDS AS WELL AS ACROSS THE LESSER ANTILLES ASSOCIATED WITH THE LARGE CYCLONIC FLOW AROUND HURRICANE BILL. MODERATE TRADE WINDS ARE BLOWING ACROSS MUCH OF THE BASIN WITH STRONGER WINDS NEAR THE COAST OF COLOMBIA WHERE A QSCAT PASS FROM THIS MORNING SHOWED NE WINDS OF 20 KT. ATLANTIC OCEAN... HURRICANE BILL REMAINS THE MAIN FEATURE ACROSS THE ATLC. SEE SPECIAL FEATURES FOR DETAILS. THE REMAINDER OF THE ATLC OCEAN IS UNDER A BROAD RIDGE ANCHORED BY A 1030 MB AZORES HIGH NEAR 39N22W. BILL CONTINUES TO MOVE AROUND THE WESTERN PERIPHERY OF THIS SFC RIDGE...BUT WILL SOON BECOME STEERED NORTHWARD AND NORTHEASTWARD BY THE FLOW BETWEEN THE AZORES HIGH AND A LARGE MID-LATITUDE TROUGH DEVELOPING OVER THE EASTERN UNITED STATES. A WEAK UPPER-LEVEL LOW IS NE OF THE NW BAHAMAS NEAR 28N75W. AN UPPER LEVEL ANTICYCLONE...EXISTING AS A RESULT OF THE OUTFLOW OF HURRICANE BILL...IS CENTERED NEAR 24N56W. IT DOMINATES MOST OF THE AREA BETWEEN 50W AND 70W. THE RIDGE EXTENDS INTO THE EASTERN CARIBBEAN PRODUCING MOSTLY FAIR WEATHER OVER THE ABC ISLANDS. $$ GR/JA