000 AXNT20 KNHC 152348 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT TUE JUL 15 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 2245 UTC. ...SPECIAL FEATURES... TROPICAL STORM BERTHA IS CENTERED NEAR 36.4N 62.3W AT 15/2100 UTC OR ABOUT 275 NM NORTH-NORTHEAST OF BERMUDA. ESTIMATED MINIMUM CENTRAL PRESSURE IS 995 MB. MAXIMUM SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. PLEASE SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC AND THE PUBLIC ADVISORY UNDER MIATCPAT2/WTNT32 KNHC FOR MORE DETAILS. BERTHA IS MAINTAINING STRONG TROPICAL STORM STRENGTH AND IS COULD GRADUALLY INTENSIFY SLIGHTLY TO A HURRICANE AGAIN. LARGE SWELLS AND HIGH SURF ARE AFFECTING BERMUDA AND ARE EXPECTED TO GRADUALLY DECREASE DURING THE NEXT COUPLE OF DAYS AS BERTHA TURNS EASTWARD AND MOVES FARTHER AWAY FROM BERMUDA. DANGEROUS RIP CURRENTS ARE ALSO OCCURRING ALONG THE U.S. EAST COAST FROM THE CAROLINAS THROUGH SOUTHERN NEW ENGLAND. SCATTERED MODERATE CONVECTION IS WITHIN 45/60 NM OF A LINE FROM 34N68W TO 38N62W WITH SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS COVERING A BROADER AREA FROM 34N-39N BETWEEN 57W-65W. STRONG TROPICAL WAVE IS ALONG 50W S OF 17N MOVING W 15-20 KT WITH A 1012 MB LOW ANALYZED ALONG THE AXIS NEAR 13N MOVING ROUGHLY WNW. THE SATELLITE PRESENTATION IS NOT AS WELL DEFINED AS YESTERDAY BUT REMAINS ROUGHLY FOCUSED NEAR THE LOW CENTER. SCATTERED CLUSTERS OF SCATTERED MODERATE CONVECTION ARE SURROUNDING THE LOW CENTER FROM 10N-14N BETWEEN 48W-53W. THIS SYSTEM IS BECOMING LESS ORGANIZED AND THE POSSIBILITY OF A TROPICAL DEPRESSION TO FORM IS DECREASING. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 31W/32W S OF 17N MOVING W 15-20 KT. A MID LEVEL LOW IS EMBEDDED WITHIN THE ITCZ ALONG THE WAVE AXIS NEAR 8N WITH AN INVERTED-V CURVATURE OBSERVED ON SATELLITE IMAGERY. THIS WAVE HAS NOT BEEN ABLE TO MAINTAIN ANY DEEP CONVECTION WITH SCATTERED SHOWERS ASSOCIATED WITH THE ITCZ. TROPICAL WAVE EXTENDS FROM E DOMINICAN REPUBLIC NEAR 18N70W TILTED ALONG 13N72W TO INLAND OVER NW VENEZUELA/NE COLOMBIA MOVING W 15-20 KT. THIS FEATURE REMAINS WELL DEFINED WITH AN INVERTED-V CURVATURE ON SATELLITE IMAGERY. A LARGE AREA OF SCATTERED MODERATE CONVECTION IS FROM 14N-18N BETWEEN 68W-75W. THE ITCZ... ITCZ AXIS IS CENTERED ALONG 8N11W 7N15W 10N26W 6N39W 9N49W 8N55W 9N62W ALONG THE N COAST OF SOUTH AMERICA ACROSS E PANAMA INTO THE E PACIFIC REGION. CLUSTERS OF SCATTERED MODERATE CONVECTION ARE FROM 2N-5N BETWEEN 39W-44W AND WITHIN 100 NM OF THE ITCZ BETWEEN 51W-60W. SCATTERED CLUSTERS OF SIMILAR CONVECTION ARE 150 NM OF THE ITCZ E OF 27W TO THE COAST OF W AFRICA. SCATTERED STRONG CONVECTION IS INLAND AND WITHIN 60 NM ALONG THE COAST OF SOUTH AMERICA AND PANAMA BETWEEN 68W-79W. ...DISCUSSION... GULF OF MEXICO... DEEP LAYERED TROUGH IS OVER THE E U.S. DIPPING S OVER THE N GULF PROVIDING SUPPORT FOR A COLD FRONT THAT IS SAGGING S INTO THE N GULF FROM TALLAHASSEE FLORIDA JUST OFF SHORE OF ALABAMA AND MISSISSIPPI INTO SE LOUISIANA NEAR NEW ORLEANS. A WEAK 1013 MB LOW IS ANALYZED JUST NW OF TAMPA FLORIDA NEAR 28N83W AT 15/2100 UTC WITH A SURFACE TROUGH EXTENDING WSW TO NEAR 25N91W THUS SPLITTING THE SURFACE RIDGE AND FORMING A BUBBLE 1018 MB HIGH IN THE NW GULF NEAR 28N93W. THIS IS CREATING A MESSY EVENING OVER THE E GULF WITH SCATTERED/NUMEROUS THUNDERSTORMS WITHIN 75 NM OF THE LOW WITH HEAVY SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS OVER THE FLORIDA PENINSULA AND FLORIDA KEYS. SCATTERED SHOWERS/ ISOLATED THUNDERSTORMS ARE WITHIN 120 NM S OF THE FRONT E OF 89W WITH SCATTERED SHOWERS/THUNDERSTORMS FROM 23N26N BETWEEN 83W-88W. AN UPPER RIDGE EXTENDS E FROM TEXAS/N MEXICO COVERING THE GULF W TO 90W PRODUCING ISOLATED SHOWERS N OF 25N BETWEEN 89W-96W. THE SW GULF REMAINS RATHER CLEAR THIS EVENING. CARIBBEAN SEA... AN UPPER TROUGH DOMINATES THE CENTRAL CARIBBEAN DRYING THE AIR NEAR ITS AXIS THAT EXTENDS FROM THE WINDWARD PASSAGE TO THE TIP OF NICARAGUA/HONDURAS AND KEEPING THE AREA N OF 15N W OF 75W TRANQUIL THIS EVENING. HOWEVER...UPPER DIFFLUENCE BETWEEN THIS TROUGH AND THE UPPER RIDGE OVER THE W GULF OF MEXICO IS PROVIDING ENOUGH UPPER LEVEL MOISTURE ACROSS THE NW CARIBBEAN TO GENERATE SCATTERED THUNDERSTORMS INLAND OVER CUBA AND THE ADJACENT COASTAL WATERS. THE ITCZ IS ALONG THE N COAST OF SOUTH AMERICA...SEE ABOVE. AND E/W UPPER RIDGE EXTENDS FROM COLOMBIA TO ACROSS S NICARAGUA GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 14NW 79W. AN UPPER HIGH DOMINATES THE E CARIBBEAN INTO THE W TROPICAL ATLC ANCHORED W OF THE WINDWARD ISLANDS NEAR 14N64W WHICH IS ENHANCING THE ACTIVITY ASSOCIATED WITH THE TROPICAL WAVE AND DRYING THE LESSER ANTILLES. ATLANTIC OCEAN... TROPICAL STORM BERTHA IS FINALLY FAR ENOUGH AWAY FROM BERMUDA FOR SKIES TO BEGIN CLEARING...SEE ABOVE. BROAD UPPER LEVEL TROUGH IS OVER THE E U.S. AND INTO THE FAR W ATLC WITH A NARROW UPPER RIDGE EXTENDING FROM THE CENTRAL FLORIDA E COAST NE TO BEYOND 32N72W PROVIDING AMPLE DIFFLUENCE TO GENERATE SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 24N-30N W OF 75W AND WITHIN 90 NM OF A LINE FROM 28N75W TO BEYOND 32N71W. AN AREA OF HIGH SURFACE PRESSURE IS BUILDING S OF THE BERTHA ANCHORED BY A 1023 MB HIGH NEAR 29N60W. A BROAD DEEP LAYERED TROUGH IS OVER THE CENTRAL ATLC N OF 17N BETWEEN 37W-55W WITH A SURFACE TROUGH ENTERING THE REGION NEAR 32N43W TO 28N47W GENERATING SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS WITHIN 120 NM EITHER SIDE OF THE TROUGH. AN UPPER RIDGE EXTENDS FROM THE UPPER HIGH IN THE E CARIBBEAN TO OVER THE W ATLC W OF 56W. A LARGE UPPER LEVEL HIGH IS CENTERED OVER THE E ATLC ANCHORED W OF THE CANARY ISLANDS NEAR 28N22W COVERING THE AREA E OF 37W. A SURFACE RIDGE EXTENDS INTO THE E ATLC THROUGH 32N30W SW TO 24N40W. $$ WALLACE