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| #30843 (Received by flhurricane at: 11:11 PM 07.Jul.2005) TCDAT4 HURRICANE DENNIS DISCUSSION NUMBER 14 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT THU JUL 07 2005 AN AIR FORCE RESERVE HURRICANE HUNTER MEASURED 700-MB FLIGHT-LEVEL WINDS OF 134 KT IN THE NORTHEAST EYEWALL AT 07/2314Z...AND ALSO REPORTED THAT THE CENTRAL PRESSURE OF DENNIS HAD DROPPED TO 951 MB. SINCE THAT TIME...THE SATELLITE SIGNATURE OF DENNIS HAS NOT CHANGED SIGNIFICANTLY. BASED ON THIS AND ON 115 KT SATELLITE INTENSITY ESTIMATES FROM SAB AND TAFB...DENNIS IS UPGRADED TO A CATEGORY FOUR HURRICANE ON THE SAFFIR-SIMPSON HURRICANE SCALE. DENNIS MAY HAVE UNDERGONE AN EYEWALL REPLACEMENT CYCLE DURING THE AFTERNOON...AS THE 9 N MI WIDE EYE SEEN EARLIER IS NOW 16 TO 20 N MI WIDE. IT SHOULD BE NOTED THAT THE 950 MB CENTRAL PRESSURE IS AN ESTIMATE AND COULD WELL BE TOO HIGH. THE INITIAL MOTION IS 310-315 AT ABOUT 13 KT. DATA FROM A TWO-AIRCRAFT SYNOPTIC SURVEILLANCE MISSION SHOWS THAT A MID/UPPER-LEVEL RIDGE REMAINS WELL ESTABLISHED ALONG 26N OVER FLOIDA AND THE ADJACENT GULF OF MEXICO. A LOW-LEVEL RIDGE IS ALSO PRESENT...BUT IS SOMEWHAT WEAKER. GUIDANCE MODELS ARE IN GOOD AGREEMENT THAT DENNIS SHOULD CONTINUE GENERALLY NORTHWESTWARD FOR ABOUT 24 HR. AFTER THAT TIME...THERE IS SOME DIVERGENCE...WITH THE UKMET TAKING DENNIS NORTHWESTWARD TOWARD LOUISIANA...THE CANADIAN TAKING DENNIS NORTHWARD ALONG THE FLORIDA WEST COAST...AND THE OTHER GUIDANCE IN BETWEEN. THE GFDL HAS SHIFTED SOMEWHAT LEFT FROM ITS PREVIOUS FORECAST...WHILE THE GFS HAS SHIFTED A LITTLE TO THE RIGHT IN THE FIRST 36 HR AND A LITTLE TO THE LEFT THEREAFTER. AS DENNIS HAS NOT YET DEVIATED FROM THE PREVIOUS FORECAST TRACK...THE NEW FORECAST IS BASICALLY AN UPDATE OF THAT TRACK THROUGH THE FIRST 36 HR. AFTER THAT...THE FORECAST TRACK IS SHIFTED SLIGHTLY TO THE LEFT...WEST...AND LIES ALONG THE RIGHT EDGE OF THE MAIN CLUSTER OF GUIDANCE. THE INTENSITY FORECAST IS PROBLEMATIC. IN THE SHORT TERM...DENNIS COULD CONTINUE TO STRENGTHEN UNTIL THE CORE ENCOUNTERS CENTRAL CUBA...AND THIS IS REFLECTED IN THE INTENSITY FORECAST. AFTER THAT...SEVERAL FACTORS COME INTO PLAY. THESE INCLUDE...WILL THE CURRENTLY TIGHTLY WOUND CORE OF DENNIS SURVIVE PASSAGE ACROSS LAND...WHAT CONCENTRIC EYEWALL CYCLES MAY OCCUR...AND HOW MUCH ENERGY IS AVAILABLE IN THE WARM...BUT THIN...SURFACE LAYER OF THE GULF OF MEXICO. THE SHIPS MODEL SUGGEST THAT THE OCEANIC HEAT CONTENT WILL DECREASE AS DENNIS MOVES NORTHWARD...CAUSING THE STORM TO WEAKEN. ON THE OTHER HAND...THE GFDL AND GFDN BOTH CALL FOR SIGNIFICANT INTENSIFICATION OVER THE GULF. THE INTENSITY FORECAST WILL COMPROMISE BETWEEN THESE EXTREMES. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 08/0300Z 19.9N 77.6W 115 KT 12HR VT 08/1200Z 21.2N 79.2W 120 KT 24HR VT 09/0000Z 23.0N 81.2W 100 KT...INLAND 36HR VT 09/1200Z 24.8N 83.1W 100 KT 48HR VT 10/0000Z 26.8N 84.6W 110 KT 72HR VT 11/0000Z 30.5N 87.0W 100 KT...INLAND 96HR VT 12/0000Z 35.5N 88.0W 30 KT...INLAND 120HR VT 13/0000Z 38.5N 86.0W 20 KT...INLAND |
