000 AXNT20 KNHC 211753 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT TUE AUG 21 2007 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND THE 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 FEATURE... THE CENTER OF NOW CATEGORY ONE HURRICANE DEAN AT 21/1800 UTC WAS NEAR 19.2N 90.4W...OR ABOUT 45 MILES...75 KM...SOUTH-SOUTHEAST OF CAMPECHE MEXICO. HURRICANE DEAN IS MOVING WEST NEAR 18 MPH. THE MAXIMUM SUSTAINED WIND SPEEDS HAVE DIMINISHED TO NEAR 85 MPH WITH HIGHER GUSTS. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 960 MB. PLEASE SEE THE LATEST NHC FORECAST ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE PUBLIC ADVISORY UNDER MIATCPAT4/WTNT34 KNHC FOR MORE DETAILS INCLUDING THE LATEST WATCH AND WARNING INFORMATION. DEAN HAS WEAKENED OVER THE YUCATAN PENINSULA OVER THE LAST SEVERAL HOURS. HOWEVER...DEAN IS ABOUT TO EMERGE INTO THE BAY OF CAMPECHE...AND WILL HAVE ABOUT 18 HOURS OVER WATER TO REGAIN STRENGTH. NUMEROUS MODERATE CONVECTION IS OVER LAND AND THE ERN BAY OF CAMPECHE FROM 16N-20N BETWEEN 89W-95W. SCATTERED MODERATE IS ELSEWHERE FROM 15N-26N BETWEEN 86W-95W. OVER THE LAST FEW HOURS LIGHTNING DATA HAS BEEN DEPICTING SEVERAL STRIKES IN THE BANDS NOTED IN THE GULF FROM 22N-26N BETWEEN 87W-94W. ...TROPICAL WAVES... A TROPICAL WAVE HAS BEEN ADDED TO THE 21/1200 UTC MAP TILTED ALONG 23N54W 15N52W 6N50W...ESTIMATED TO BE MOVING W NEAR 15-20 KT. THE WAVE WAS ADDED DUE ITS SIGNATURE IN THIS MORNINGS VISIBLE SATELLITE IMAGERY SHOWING CYCLONIC TURNING IN THE LOW LEVEL CLOUD FIELD...AND ALSO ITS APPEARANCE IN A LONG TERM LOOP OVER THE LAST FEW DAYS. IN ADDITION...THE WAVE ALSO SHOWS UP WELL IN THE UW-CIMSS SSMI/AMSRE DERIVED TPW PRODUCT AS A SECONDARY SURGE OF MOISTURE BEHIND THE LARGER WAVE TO ITS W. FINALLY...BOTH THE DAKAR AND SAL SOUNDINGS SHOWED TWO SEPARATE WAVES PASS LAST WEEK. ASSOCIATED SCATTERED MODERATE CONVECTION IS LIMITED TO WHERE THE SRN PORTION OF THE WAVE INTERSECTS WITH THE ITCZ FROM 7N-12N BETWEEN 47W-55W. A LARGE AMPLITUDE TROPICAL WAVE IS ALONG 67W S OF 29N MOVING W 15-20 KT. THE WAVE IS INTERACTING WITH AN ELONGATED UPPER LOW MOVING W THROUGH HISPANIOLA TO PRODUCE DISORGANIZED SCATTERED SHOWERS AND ISOLATED TSTMS...MAINLY FROM 20N-29N BETWEEN 58W-72W. A 1014 MB LOW IS ALONG THE WAVE AXIS NEAR 25N BUT THIS CIRCULATION IS RATHER RAGGED AT THE MOMENT. UPPER-LEVEL WINDS ARE BECOMING LESS FAVORABLE FOR DEVELOPMENT FOR THIS SYSTEM. ...THE ITCZ... AXIS CENTERED ALONG 12N16W 11N30W 10N40W 11N48W 7N59W. SCATTERED MODERATE CONVECTION IS ALONG AND OFF THE AFRICAN COAST FROM 6N-13N E OF 22W. SOME OF THIS APPEARS TO BE ASSOCIATED WITH A TROPICAL WAVE STILL INLAND OVER AFRICA. SCATTERED MODERATE IS ALSO WITHIN 30 NM N AND 210 NM S OF THE AXIS BETWEEN 33W-47W. DISCUSSION... THE GULF OF MEXICO... HURRICANE DEAN WILL MOVE INTO THE FAR SRN GULF/ERN BAY OF CAMPECHE OVER THE NEXT COUPLE OF HOURS. SEE DETAILS ABOVE. ASIDE FROM THE HIGH WINDS/SEAS NEAR THE CENTER OF DEAN...A FAIRLY SIGNIFICANT LONGER PERIOD SWELL WILL SPREAD THROUGH THE NW AND MIDDLE GULF OVER THE NEXT COUPLE OF DAYS. SEE STATEMENTS FROM LOCAL WEATHER SERVICE OFFICES AND TAFB HIGH SEAS/OFFSHORE WATERS FORECASTS FOR MORE DETAILS. ELSEWHERE AT THE SFC A WEAK RIDGE IS ALONG 30N AND WILL REMAIN QUASI-STATIONARY OVER THE NEXT FEW DAYS. ALOFT...A MID TO UPPER LOW CONTINUES TO MOVE INLAND OVER NRN MEXICO WHILE A MID TO UPPER RIDGE IS N/NE OF DEAN...STEERING THE CYCLONE WWD. THE CARIBBEAN SEA... WINDS AND SEAS STILL AN ISSUE IN THE FAR NW PORTION FROM DEAN...BUT WILL CONTINUE TO STEADILY RELAX THROUGH WED AS THE STORM MOVES AWAY FROM THE AREA. OUTSIDE OF DEAN THE MOST ACTIVE WEATHER IS IN THE SW PORTION...WITH SCATTERED SHOWERS/TSTMS S OF 16N BETWEEN 75W-84W. IN ADDITION TO CONFLUENT LOW LEVEL FLOW IN THIS VICINITY...THE ACTIVITY IS BEING SUPPORTED BY DIFFLUENCE ALOFT BETWEEN NE FLOW OVER THE SW CARIBBEAN AND THE FLOW AROUND THE DOMINATING UPPER LOW MOVING W OVER HISPANIOLA. THE SW FLOW AHEAD OF THIS LOW IS ADVECTING TROPICAL MOISTURE NE THROUGH THE ERN CARIBBEAN. THIS ALONG WITH THE TROPICAL WAVE IN THE VICINITY IS SUPPORTING SCATTERED SHOWERS MAINLY N OF 15N E OF 70W. THE ATLANTIC OCEAN... THE AREA JUST OFF THE FLORIDA/SE U.S. COAST IS EXPERIENCING FAIR WEATHER WITH DEEP LAYER RIDGING AND DRY MID TO UPPER AIR IN PLACE. THE WEATHER IS A BIT MORE ACTIVE FURTHER E/N OF HISPANIOLA AND PUERTO RICO DUE TO THE COMBINATION OF THE UPPER LOW AND TROPICAL WAVE IN THE VICINITY...SEE DETAILS ABOVE. AN UPPER HIGH IS NEAR 31N64W WHILE A BENIGN UPPER LOW IS NEAR 32N34W. TYPICAL UPPER RIDGING EXTENDS W FROM AFRICA OUT TO 30W. ELSEWHERE AT THE SFC LARGE SCALE RIDGING DOMINATES IN THE S/SW PERIPHERY OF A 1024 MB HIGH CENTERED WELL NE OF THE AZORES. THIS IS PRODUCING ABUNDANT FAIR WEATHER AND MODERATE TRADES N OF 15N E OF 50W. $$ WILLIS