000 AXNT20 KNHC 110009 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT THU JUL 10 2008 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...SPECIAL FEATURE.... THE CENTER OF HURRICANE BERTHA AT 10/2100 UTC IS NEAR 27.2N 60.8W. BERTHA IS MOVING NORTHWEST OR 315 DEGREES AT 9 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 980 MB. THE MAXIMUM SUSTAINED WIND SPEEDS ARE NOW 75 KT WITH GUSTS TO 90 KT MAKING BERTHA A CATEGORY 1 HURRICANE ON THE SAFFIR-SIMPSON SCALE. BERTHA IS LOCATED ABOUT 425 MILES...685 KM...SOUTHEAST OF BERMUDA. LONG PERIOD SWELLS OF 12-13 SECONDS ASSOCIATED WITH BERTHA ARE NOW AFFECTING BERMUDA. SATELLITE IMAGERY INDICATES THAT THE EYE OF BERTHA HAS BECOME BETTER DEFINED THIS AFTERNOON. HOWEVER...CONVECTIVE TOPS IN THE EYEWALL HAVE WARMED AND THERE ARE SIGNS THAT THE SYSTEM MAY BE ENTRAINING SOME DRY AIR. THE INITIAL INTENSITY HAS THUS BEEN REDUCED TO 75 KT. NONETHELESS THE ATMOSPHERE IS EXPECTED TO REMAIN FAVORABLE FOR ADDITIONAL STRENGTHENING AS A LARGE UPPER-LEVEL ANTICYCLONE DEVELOPS OVER BERTHA DURING THE NEXT 24-48 HOURS. IN ADDITION...THE SYSTEM IS STILL OVER WARM WATER. GIVEN THE ENVIRONMENT...THE INTENSITY FORECAST CALLS FOR MODEST STRENGTHENING IN 24 HOURS. LATER IN THE FORECAST PERIOD...BERTHA IS EXPECTED TO MOVE OUT FROM UNDER THE ANTICYCLONE AND ENCOUNTER VERTICAL WIND SHEAR. THIS SHOULD OCCUR AS BERTHA REACHES COOLER WATERS AND RESULT IN A WEAKENING TREND. DUE TO THE UNCERTAINTY IN THE FORECAST TRACK...INTERESTS IN BERMUDA SHOULD CLOSELY MONITOR THE PROGRESS OF BERTHA DURING THE NEXT SEVERAL DAYS. PLEASE REFER TO THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC AND THE PUBLIC ADVISORY UNDER MIATCPAT2/WTNT32 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 36W SOUTH OF 13N IS MOVING WEST 10 TO 15 KT. INVERTED-V PATTERN SEEN EARLIER ON VIS SAT IMAGERY IS ALSO NOTED IN IR IMAGERY AS WELL. POCKETS OF MODERATE CONVECTION ARE NOTED NEAR THE INTERSECTION OF THE WAVE AXIS AND THE ITCZ. LOW-LEVEL SATELLITE DERIVED WINDS ALSO SUPPORT THE POSITION OF THE WAVE AXIS. A TROPICAL WAVE IS ALONG 61W/62W SOUTH OF 14N IS MOVING WEST AT 15 KT. MOST OF THE CONVECTION ASSOCIATED WITH THE WAVE HAS MOVED INTO THE EASTERN CARIBBEAN SEA. HOWEVER SOME ACTIVITY CONTINUES OVER PORTIONS OF TRINIDAD AND GRENADA. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 11N TO 14N BETWEEN 63W AND 70W. A DIFFLUENT PATTERN ALOFT IS HELPING TO INDUCE THIS SHOWER AND TSTM ACTIVITY. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 11N15W 8N22W 8N30W 5N42W 8N59W. SCATTERED MODERATE CONVECTION IS FROM 4N TO 9N BETWEEN 25W AND 30W. SIMILAR CONVECTION IS FROM 9N TO 11N BETWEEN 40W AND 45W AND NEAR 7N51W. A CLUSTER OF SCATTERED MODERATE ISOLATED STRONG CONVECTION HAS MOVED OFFSHORE OF SENEGAL AND GUINEA BISSAU. THIS CONVECTION IS OCCURRING IN ADVANCE OF THE NEXT TROPICAL WAVE JUST ABOUT TO EMERGE OFF THE AFRICAN COAST. ...DISCUSSION... THE GULF OF MEXICO... MIDDLE TO UPPER-LEVEL RIDGE CENTERED OVER THE SE CONUS COVERS MOST OF THE GULF REGION WHILE A WEAK CYCLONIC CIRCULATION REMAINS OVER THE BAY OF CAMPECHE. A SFC TROUGH ALONG 24N97W TO 19N95W IS DRIFTING WESTWARD. SCATTERED SHOWERS AND ISOLATED TSTMS ASSOCIATED WITH THIS FEATURE OVER THE BAY OF CAMPECHE HAVE WEAKENED. HOWEVER A CLUSTER OF STRONG THUNDERSTORMS ARE SLIDING ACROSS THE EXTREME SOUTHERN BAY OF CAMPECHE AFTER EMERGING OFF THE ISTHMUS OF TEHUANTEPEC. ISOLATED SHOWERS OR THUNDERSTORMS ARE NOTED OVER THE REMAINDER OF THE GULF THANKS TO THE INFLUENCE OF THE RIDGE. AT THE SURFACE...A WEAK RIDGE OF HIGH PRESSURE DOMINATES THE GULF GIVING THE AREA MAINLY LIGHT TO MODERATE WINDS. THE STRONGEST WINDS UP TO 20 KT ARE FOUND OVER THE BAY CAMPECHE DUE A SLIGHTLY THIGH PRES GRADIENT BETWEEN THE RIDGE AND THE SFC TROUGH. THE CARIBBEAN SEA... A MIDDLE TO UPPER-LEVEL TROUGH FROM THE W ATLC EXTENDS SW ACROSS EASTERN CUBA AND THE NORTHWEST CARIBBEAN SEA GENERATING SCATTERED SHOWERS AND TSTMS. AN UPPER-LEVEL RIDGE ANCHORED ON A HIGH OVER NORTHERN COLOMBIA IS SOUTH OF THIS TROUGH. UPPER DIFFLUENT FLOW ASSOCIATED WITH THIS FEATURE IS ENHANCING SCATTERED MODERATE CONVECTION OVER THE SW CARIBBEAN. AS PREVIOUSLY MENTIONED A TROPICAL WAVE IS AFFECTING THE WINDWARD ISLANDS AND THE FAR SE CARIBBEAN SEA. SEE TROPICAL WAVE SECTION FOR DETAILS. NARROW BANDS OF MAINLY LOW CLOUDS ASSOCIATED WITH THE PERIPHERAL CIRCULATION OF HURRICANE BERTHA ARE MOVING ACROSS THE NORTHEAST LEEWARD ISLANDS...THE UK/US VIRGIN ISLANDS AND PUERTO RICO. MODERATE TRADE WINDS ARE BLOWING ACROSS THE BASIN. THESE WINDS ARE FORECAST TO INCREASE UP TO 30 KT NEAR THE COLOMBIAN COAST BEGINNING TONIGHT THROUGH AT LEAST SUN MORNING AS PRES GRADIENT TIGHTENS OVER THE E AND CENTRAL CARIBBEAN. THE ATLANTIC OCEAN... A STATIONARY MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION CENTER IS NEAR 28N70W. CYCLONIC FLOW AROUND THIS CENTER EXTENDS SW ACROSS THE BAHAMAS AND EASTERN CUBA. A MIDDLE TO UPPER LEVEL TROUGH IS DROPPING SOUTHWARD JUST TO THE NORTHEAST OF HURRICANE BERTHA...WITH AXIS CLIPPING THE FORECAST AREA NEAR 29N48W. THIS TROUGH SUPPORTS A COLD FRONT LOCATED OVER THE CENTRAL ATLC. OUTSIDE OF HURRICANE BERTHA...A SURFACE RIDGE DOMINATES THE REMAINDER OF THE ATLC DISCUSSION AREA WITH A 1026 MB HIGH CENTERED NEAR 32N31W. THIS SFC HIGH PAIRED WITH LOWER PRES OVER WESTERN AFRICA IS PRODUCING A SWATH OF MODERATE TO STRONG NE WINDS N OF 20N AND E OF 20W...INCLUDING THE CANARY ISLANDS. A SHEARED MIDDLE TO UPPER LEVEL TROUGH ENTERS THE THE EASTERN ATLANTIC NEAR 32N24W THEN CONTINUES SW TO NEAR 22N34W. MID TO UPPER LEVEL RIDGE ANCHORED ON A HIGH OVER MAINLAND AFRICA DOMINATES THE FLOW OVER THE DEEP TROPICS PARTICULARLY E OF 50W. $$ COBB