000 AXNT20 KNHC 200606 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT MON AUG 20 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0415 UTC. ...SPECIAL FEATURE... THE EYE OF EXTREMELY DANGEROUS CATEGORY FOUR HURRICANE DEAN WAS NEAR 17.7N 79.7W...OR 130 NM/240 KM SOUTHEAST OF GRAND CAYMAN. DEAN IS MOVING WEST 17 KT. THE MAXIMUM SUSTAINED WIND SPEEDS ARE 125 KT WITH GUSTS TO 155 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 926 MB. FLUCTUATIONS IN INTENSITY ARE COMMON IN MAJOR HURRICANES AND ARE POSSIBLE DURING THE NEXT 24 HOURS. DEAN HAS THE POTENTIAL TO BECOME A CATEGORY FIVE HURRICANE IN THE NORTHWESTERN CARIBBEAN SEA ON MONDAY...LIKE GILBERT IN 1988 AND WILMA IN 2005. ALL RESIDENTS IN THE WESTERN CARIBBEAN SEA...AND THE GULF OF MEXICO SHOULD MONITOR THE PROGRESS OF THIS POWERFUL HURRICANE. PLEASE SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE LATEST PUBLIC ADVISORY UNDER MIATCPAT4/WTNT34 KNHC FOR THE MOST RECENT WATCH AND WARNING INFORMATION. FOR STORM INFORMATION SPECIFIC TO YOUR AREA...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS. PLEASE MONITOR FORECASTS AND BULLETINS ISSUED BY YOUR LOCAL WEATHER OFFICE. HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 52 NM/95 KM FROM THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 176 NM/335 KM. COASTAL STORM SURGE FLOODING OF 5 TO 7 FEET ABOVE NORMAL TIDE LEVELS...ALONG WITH LARGE AND DANGEROUS BATTERING WAVES...IS POSSIBLE NEAR THE CENTER OF DEAN WITHIN THE HURRICANE WARNING AREAS IN JAMAICA AND THE CAYMAN ISLANDS. STORM SURGE FLOODING AND WAVES IN JAMAICA SHOULD SUBSIDE LATER TODAY. COASTAL STORM SURGE FLOODING OF 9 TO 11 FEET ABOVE NORMAL TIDE LEVELS IS POSSIBLE NEAR AND TO THE NORTH OF WHERE DEAN MAKES LANDFALL ALONG THE EAST COAST OF THE YUCATAN PENINSULA. THE EYE OF DEAN PASSED JUST SOUTH OF JAMAICA STARTING AT 19/1900 UTC AND HAS JUST CROSSED THE LONGITUDE OF NEGRIL ON THE WESTERN END OF THE ISLAND AROUND 20/0300 UTC. THE CENTER CAME WITHIN ABOUT 20 N MI OF PORTLAND POINT ON THE SOUTH CENTRAL COAST...CLOSE ENOUGH TO BRING HURRICANE-FORCE WINDS TO KINGSTON. SATELLITE IMAGERY SUGGESTED THAT THE EYE DIAMETER WAS SHRINKING GRADUALLY AS THE EYE WAS PASSING BY JAMAICA. AN AIR FORCE HURRICANE HUNTER AIRCRAFT ARRIVED IN THE EYE OF DEAN AT 20/0130 UTC AND REVEALED THAT THE PRESSURE HAD FALLEN TO NEAR 925 MB...AND THAT DEAN NOW HAS A SINGLE EYEWALL AT A DIAMETER OF ABOUT 15 N MI. THE SATELLITE APPEARANCE OF DEAN WAS IMPRESSIVE WITH GOOD SYMMETRY FOR THE EYE...THE EYEWALL...SPIRAL RAINBANDS AND OUTFLOW. NUMEROUS STRONG SHOWERS AND THUNDERSTORMS ARE FROM 16.5N TO 18.5N BETWEEN 78W AND 80.5W. STRONG SHOWERS AND THUNDERSTORMS IN BANDS AROUND THE CENTER ARE WITHIN 90 TO 120 NM OF THE CENTER FROM EAST TO SOUTH. STRONG SHOWERS AND THUNDERSTORMS ARE FROM 15N TO 17N BETWEEN 71W AND 73W...AND FROM 11N TO 12N BETWEEN 73W AND 75W IN THE OUTER BAND THAT IS ABOUT 400 NM EAST OF THE CENTER. ISOLATED MODERATE SHOWERS TO LOCALLY STRONG THUNDERSTORMS EXTEND FROM ONE END OF CUBA TO THE OTHER END. ...TROPICAL WAVES... A LARGE ATLANTIC OCEAN TROPICAL WAVE IS ALONG 54W/55W SOUTH OF 25N MOVING WEST 20 KT DURING THE LAST 24 HOURS. A 1010 MB LOW PRESSURE CENTER IS ALONG THIS WAVE NEAR 12.5N. THE LOW CENTER HAS BEEN WEAKENING WITH TIME. SCATTERED STRONG SHOWERS AND THUNDERSTORMS ARE FROM 20N TO 22N BETWEEN 50W AND 53.5W...AND FROM 23.5N TO 25N BETWEEN 55W AND 57W. SCATTERED MODERATE SHOWERS TO ISOLATED STRONG THUNDERSTORMS ARE ELSEWHERE FROM 19.5N TO 26N BETWEEN 50W AND 60W. ISOLATED MODERATE SHOWERS ARE IN THE ATLANTIC OCEAN AND THE CARIBBEAN SEA FROM 9N TO 20N BETWEEN 50W AND 61W...AND IN THE ATLANTIC OCEAN FROM 14N TO 21N BETWEEN 42W AND 50W. THIS WAVE WILL CONTINUE TO BE MONITORED AS SLOW DEVELOPMENT APPEARS POSSIBLE AS IT TRACKS WEST-NORTHWESTWARD DURING THE NEXT COUPLE OF DAYS. A GULF OF MEXICO TROPICAL WAVE IS ALONG 92W/93W SOUTH OF 20N MOVING WEST 10 TO 15 KT. A MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION CENTER IS NEAR 26N92W. ALL THE PRECIPITATION IN THE GULF OF MEXICO WEST OF 84W/85W APPEARS TO BE RELATED TO THIS CYCLONIC CENTER. FEW SHOWERS OVER THE ISTHMUS OF TEHUANTEPEC. ...THE ITCZ... FROM THE AFRICA COAST NEAR 12N16W TO 7N33W TO 14N44W 16N50W... FROM 11N58W TO 10N62W. STRONG SHOWERS AND THUNDERSTORMS ARE FROM 10N TO 11N BETWEEN 24W AND 29W...AND FROM 6.5N TO 7N BETWEEN 41W AND 42.5W. ISOLATED MODERATE SHOWERS TO LOCALLY STRONG THUNDERSTORMS ELSEWHERE FROM 3N TO 10N BETWEEN 20W AND 50W. DISCUSSION... THE GULF OF MEXICO... A MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION CENTER IS NEAR 26N92W CONTINUING TO MOVE WESTWARD ACROSS THE GULF OF MEXICO. THE WESTWARD MOVEMENT OF 15 TO 20 KT THAT WAS PREDICTED BY MANY OF THE COMPUTER MODELS HAS BEEN PRETTY ACCURATE...THUS LIMITING IT'S IMPACTS ON HURRICANE DEAN. CYCLONIC FLOW AROUND THE CENTER COVERS THE AREA WEST OF 84W/85W. PRECIPITATION FROM 4 TO 5 HOURS AGO ALONG THE NORTHWESTERN YUCATAN PENINSULA AND ABOUT 240 NM TO THE SOUTH OF THE CENTER HAS DISSIPATED. POSSIBLE SHOWERS ARE NORTH OF 21N WEST OF 90W. SCATTERED MODERATE SHOWERS TO ISOLATED STRONG THUNDERSTORMS ARE FROM 26N TO 27N BETWEEN 83W AND 84W OFF THE WEST COAST OF FLORIDA IN UPPER LEVEL DIFFLUENT WIND FLOW. A MIDDLE LEVEL ANTICYCLONIC CIRCULATION CENTER IS NEAR 30N/31N ALONG 75W. UPPER LEVEL ANTICYCLONIC FLOW IS IN THE GULF OF MEXICO EAST OF 84W/85W...AND FROM THE BAHAMAS NORTHWARD WEST OF 70W IN THE ATLANTIC OCEAN. A SURFACE RIDGE EXTENDS FROM SOUTHWESTERN GEORGIA TO SOUTHEASTERN LOUISIANA TOWARD 23N95W IN THE SOUTHWESTERN CORNER OF THE GULF OF MEXICO. A TROPICAL WAVE IS ALONG 92W/93W SOUTH OF 20N. THE CARIBBEAN SEA... ALL THE ATTENTION REMAINS FOCUSED ON POWERFUL CATEGORY FOUR HURRICANE DEAN. DEAN WILL CONTINUE TO HAVE SIGNIFICANT IMPACTS ON THE CENTRAL AND WESTERN CARIBBEAN SEA AS WELL AS THE YUCATAN PENINSULA FROM NOW UNTIL AND INCLUDING TUESDAY NIGHT. A MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM THE ATLANTIC OCEAN NEAR 25N56W TO 16N63W IN THE NORTHEASTERN CORNER OF THE AREA. THE ATLANTIC OCEAN... AN MIDDLE LEVEL ANTICYCLONIC CIRCULATION CENTER IS NEAR 30N/31N ALONG 75W. MIDDLE LEVEL ANTICYCLONIC FLOW IS IN THE ATLANTIC OCEAN FROM THE BAHAMAS NORTHWARD WEST OF 70W. THIS IS THE FEATURE STEERING DEAN FAIRLY QUICKLY TO THE WEST OR WEST- NORTHWEST ACROSS THE WESTERN CARIBBEAN SEA. DEAN'S STRONG CIRCULATION IS CAUSING DISTINCT SINKING/DRYING BEYOND IT'S OUTFLOW ACROSS THE CENTRAL BAHAMAS AND REGIONS MORE TO THE NORTH. EASTERLY WINDS ARE QUITE STRONG...25 TO 30 KT WITH HIGHER GUSTS ACROSS THE EXTREME SOUTHWESTERN ATLANTIC OCEAN NEAR DEAN. A MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM THE ATLANTIC OCEAN NEAR 25N56W TO 16N63W IN THE NORTHEASTERN CORNER OF THE CARIBBEAN SEA. THIS TROUGH IS RIGHT ON TOP OF THE 54W/55W TROPICAL WAVE. A MIDDLE LEVEL ANTICYCLONIC CIRCULATION CENTER IS NEAR 14N40W. ANTICYCLONIC FLOW IS WITHIN A 360 NM RADIUS OF THE CENTER. A MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM A CYCLONIC CIRCULATION CENTER NEAR 30N29W TO 23N38W. A SURFACE RIDGE PASSES THROUGH 32N49W...TO JUST SOUTH OF BERMUDA...TO 32N77W...INTO SOUTHWESTERN GEORGIA. $$ MT