000 AXNT20 KNHC 151750 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...SPECIAL FEATURES... TROPICAL STORM BERTHA IS CENTERED NEAR 35.6N 62.7W AT 15/1500 UTC OR ABOUT 225 NM NORTH-NORTHEAST OF BERMUDA. THE MINIMUM CENTRAL PRESSURE IS 995 MB. THE 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 FORECAST TO 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. THE DEEPEST CONVECTION IS WITHIN 120 NM OF THE CENTER OVER THE NORTHERN SEMICIRCLE WITH SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS COVERING A BROAD AREA ELSEWHERE FROM 33N-38N BETWEEN 58W-64W. STRONG TROPICAL WAVE IS ALONG 48W S OF 18N MOVING W NEAR 15 KT WITH A 1012 MB LOW ANALYZED ALONG THE AXIS NEAR 12N MOVING ROUGHLY WNW NEAR 15 KT. SATELLITE IMAGERY SHOWS A LARGE WELL DEFINED ENVELOPE OF CYCLONIC ROTATION...FOCUSED NEAR THE LOW CENTER. SCATTERED MODERATE CONVECTION IS MAINLY WEST OF THE AXIS FROM 11N-14N BETWEEN 47W-53W. THIS SYSTEM HAS GENERALLY BECOME LESS ORGANIZED AND THE POSSIBILITY OF A TROPICAL DEPRESSION TO FORM IS DECREASING. ...TROPICAL WAVES... NEW TROPICAL WAVE IS INTRODUCED OFF THE COAST OF AFRICA ALONG 28W/29W S OF 18N. THE AREA OF CLOUDINESS ASSOCIATED WITH THE WAVE HAS BEEN TRACKED FOR SEVERAL DAYS NOW AS IT MOVED WWD AND NOW SHOWS SOME APPARENT CYCLONIC TURNING. SCATTERED MODERATE CONVECTION IS MOSTLY W OF THE AXIS FROM 3N-9N BETWEEN 28W-35W. TROPICAL WAVE EXTENDS FROM EASTERN DOMINICAN REPUBLIC TILTED ALONG 70W MOVING W 15 KT. THIS FEATURE REMAINS WELL DEFINED WITH IR SATELLITE IMAGERY SHOWING INVERTED-V CURVATURE ALONG THE AXIS IN THE ERN CARIBBEAN. A LARGE AREA OF SCATTERED MODERATE AND EMBEDDED ISOLATED STRONG CONVECTION IS FROM 13N-17N BETWEEN 67W-74W. THE ITCZ... ITCZ AXIS IS CENTERED ALONG 11N16W 12N27W 8N39W 10N57W 9N83W. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 5N-9N BETWEEN 11W-16W. SCATTERED MODERATE CONVECTION IS FROM SIMILAR CONVECTION IS FROM 8N-11N BETWEEN 79W-82W. ...DISCUSSION... GULF OF MEXICO... DEEP LAYERED TROUGH IS OVER THE ERN U.S. DIPPING S TO THE N GULF COAST PROVIDING SUPPORT FOR A STATIONARY FRONTAL BOUNDARY AT THE SURFACE ALONG THE N GULF COAST. A WEAK 1012 MB LOW IS LOCATED NEAR TALLAHASSEE FLORIDA ANALYZED WITH A SURFACE TROUGH EXTENDING WSW. THIS SURFACE LOW PRESSURE COUPLED WITH THE DIFFLUENCE AHEAD OF THE UPPER TROUGH IS GENERATING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ALONG THE N GULF. ACTIVITY HAS DECREASED SINCE EARLIER THIS MORNING BUT IS STILL PRESENT FROM 26N-29N BETWEEN 85W-87W AND FROM 26N-30N BETWEEN 88W-94W. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE ALSO ACROSS THE SE GULF AND SRN FLORIDA. STRONG SUBSIDENCE AND DRY STABLE AIR ARE NORTH OF THE STATIONARY BOUNDARY THAT EXTENDS ACROSS THE SE CONUS. AN UPPER HIGH IS OVER CENTRAL TEXAS WITH THE RIDGE AXIS EXTENDING SE TO THE CENTRAL GULF OF MEXICO. THIS UPPER LEVEL DIFFLUENT PATTERN IS ENHANCING THE TSTM ACTIVITY OVER THE NRN GULF AS WELL AS AIDING IN THE AFOREMENTIONED CLUSTERS OF SCATTERED SHOWERS/THUNDERSTORMS OVER THE ERN GULF E OF 85W. CARIBBEAN SEA... AN UPPER TROUGH DOMINATES THE CENTRAL CARIBBEAN DRYING THE AIR NEAR ITS AXIS CAUSING TRANQUIL WEATHER ON THE SURFACE. HOWEVER...UPPER DIFFLUENCE BETWEEN THE TROUGH AND THE UPPER RIDGE THAT COVERS THE GULF OF MEXICO IS PROVIDING ABUNDANT UPPER LEVEL MOISTURE ACROSS THE NW CARIBBEAN SEA. THE ITCZ CROSSES THE SW CARIBBEAN FROM NRN COLOMBIA ACROSS PANAMA INTO THE E PACIFIC REGION GENERATING SCATTERED SHOWERS AND TSTMS ALONG COASTAL PANAMA AND COSTA RICA BETWEEN 78W-83W. THE ERN CARIBBEAN IS DOMINATED BY AN UPPER HIGH ANCHORED OVER THE WINDWARD ISLANDS WHICH IS ENHANCING THE CONVECTIVE ACTIVITY ASSOCIATED WITH THE TROPICAL WAVE ALONG 70W. ATLANTIC OCEAN... TROPICAL STORM BERTHA IS PULLING N AWAY FROM BERMUDA...SEE ABOVE. BROAD UPPER LEVEL TROUGHING IS ACROSS THE ERN U.S. SEABOARD AND THE FAR W ATLC WATERS. THIS ALONG WITH A SMALL UPPER RIDGE FROM 31N72W TO 28N80W IS PROVIDING AMPLE DIFFLUENCE TO GENERATE SCATTERED SHOWERS AND TSTMS WITHIN 90 NM OF A LINE FROM 30N75W ACROSS GRAND BAHAMA ISLAND TO NEAR THE STRAITS OF FLORIDA. A BROAD DEEP LAYERED TROUGH IS OVER THE CENTRAL ATLC N OF 18N BETWEEN 35W-55W WITH A DISSIPATING ASSOCIATED COLD FRONT NORTH OF THE AREA AND SURFACE TROUGH ENTERING THE AREA NEAR 32N43W TO 28N49W. SCATTERED SHOWERS ARE WITHIN 120 NM EITHER SIDE OF THE TROUGH. A LARGE UPPER LEVEL HIGH IS CENTERED OVER THE SOUTH CENTRAL AND WEST TROPICAL ATLC NEAR 15N62W. A WEAKER UPPER HIGH IS NEAR 16N41W. THE COMBINATION OF THESE TWO HIGHS IS CAUSING DIFFLUENCE ALOFT WHICH SUPPORTS THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVE NEAR 48W. ANOTHER UPPER LEVEL HIGH IS WEST OF THE CANARY ISLANDS NEAR 29N22W COVERING THE ERN ATLC E OF 35W. A SURFACE RIDGE OF HIGH PRESSURE EXTENDS ACROSS THE ERN ATLC ANCHORED ON A 1036 MB HIGH CENTERED WELL N OF THE AZORES. $$ WALTON/CANGIALOSI