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| #146734 (Received by flhurricane at: 4:40 AM 18.Aug.2007) TCDAT4 HURRICANE DEAN DISCUSSION NUMBER 21 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042007 500 AM EDT SAT AUG 18 2007 NEAR 0500 UTC...AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT REPORTED 154 KT FLIGHT-LEVEL WINDS IN THE NORTHERN EYEWALL OF DEAN...AND ALSO REPORTED THAT THE CENTRAL PRESSURE FELL TO 930 MB. THE FLIGHT-LEVEL WINDS COULD HAVE JUSTIFIED CALLING DEAN A CATEGORY FIVE HURRICANE. HOWEVER...DATA FROM DROPSONDES...THE STEPPED- FREQUENCY MICROWAVE RADIOMETER...AND SATELLITE INTENSITY ESTIMATES DID NOT SUPPORT THAT STATUS. THE INTENSITY WAS THUS SET TO A SLIGHTLY MORE CONSERVATIVE 130 KT. THERE HAS BEEN LITTLE CHANGE IN THE SATELLITE APPEARANCE OF DEAN SINCE THE AIRCRAFT LEFT...SO 130 KT IS THE INITIAL INTENSITY FOR THIS ADVISORY. THE INITIAL MOTION IS 275/15...AGAIN SLIGHTLY SLOWER THAN BEFORE. DEAN CONTINUES TO BE STEERED BY A RIDGE OVER THE WESTERN ATLANTIC WHICH SHOULD BUILD WESTWARD DURING THE NEXT 72-96 HR AS AN UPPER-LEVEL LOW OVER SOUTH FLORIDA MOVES WESTWARD. IN THE SHORT TERM...THE GUIDANCE IS IN GOOD AGREEMENT ON A WEST-NORTHWESTWARD TRACK TOWARD JAMAICA. THE OFFICIAL FORECAST WILL FOLLOW THIS...WITH THE TRACK DOWN THE LEFT SIDE OF THE GUIDANCE ENVELOPE DUE TO THE INITIAL MOTION. AFTER THAT...UKMET...GFS...AND CONSENSUS MODELS CALL FOR A MOTION TOWARD THE NORTHERN YUCATAN PENINSULA AND NORTHEASTERN MEXICO. THE GFDL CALLS FOR A MOTION THROUGH THE YUCATAN CHANNEL TO THE TEXAS COAST...WHILE THE ECMWF AND NOGAPS CALL FOR A MORE WESTERLY MOTION THROUGH THE CENTRAL YUCATAN AND THE BAY OF CAMPECHE INTO MAINLAND MEXICO. THE TRACK FORECAST IS NUDGED A LITTLE SOUTH OF THE PREVIOUS FORECAST IN BEST AGREEMENT WITH THE CONSENSUS MODELS. SINCE UPPER-LEVEL WINDS ARE FORECAST TO REMAIN FAVORABLE...THE INTENSITY FORECAST CALLS FOR A GRADUAL INCREASE IN STRENGTH THROUGH 72 HR DUE TO INCREASING SEA SURFACE TEMPERATURES AND MAXIMUM POTENTIAL INTENSITY. HOWEVER...THERE ARE LIKELY TO BE SIGNIFICANT FLUCTUATIONS ON TOP OF THIS DUE TO DIFFICULT TO TIME EYEWALL REPLACEMENT CYCLES. PASSAGE OVER THE YUCATAN PENINSULA SHOULD CAUSE SOME WEAKENING...FOLLOWED BY RE-INTENSIFICATION OVER THE GULF OF MEXICO. FORECAST POSITIONS AND MAX WINDS INITIAL 18/0900Z 15.1N 67.3W 130 KT 12HR VT 18/1800Z 15.6N 69.6W 130 KT 24HR VT 19/0600Z 16.5N 72.8W 135 KT 36HR VT 19/1800Z 17.6N 76.4W 135 KT 48HR VT 20/0600Z 18.5N 80.0W 135 KT 72HR VT 21/0600Z 20.5N 86.5W 140 KT 96HR VT 22/0600Z 22.5N 92.5W 110 KT 120HR VT 23/0600Z 24.5N 98.0W 115 KT...INLAND $$ FORECASTER BEVEN |
