000 WTNT44 KNHC 182024 TCDAT4 HURRICANE DEAN DISCUSSION NUMBER 23 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042007 500 PM EDT SAT AUG 18 2007 THERE HAVE BEEN NO SIGNIFICANT CHANGES IN THE STRUCTURE OF DEAN DURING THE PAST SEVERAL HOURS. THE LAST RECONNAISSANCE AIRCRAFT INTO THE EYE MEASURED 930 MB AND THE REPORTED WINDS SUPPORT AN INITIAL INTENSITY OF 130 KNOTS. HOWEVER...THE CREW OBSERVED A DOUBLE EYEWALL AND THE PRESENCE OF THIS FEATURE WILL PROBABLY RESULT IN SHORT TERM FLUCTUATIONS IN INTENSITY. THE SATELLITE PRESENTATION IS OUTSTANDING WITH A WELL DEFINED EYE...NUMEROUS SPIRAL BANDS AND AN EXPANDING OUTFLOW. WITH AN ENVIRONMENT OF LOW SHEAR AND VERY HIGH OCEANIC HEAT CONTENT BETWEEN THE CAYMAN ISLANDS AND YUCATAN...SOME ADDITIONAL INTENSIFICATION IS POSSIBLE. IN FACT...DEAN COULD BECOME A POTENTIALLY CATASTROPHIC CATEGORY FIVE HURRICANE AT ANY TIME BEFORE IT REACHES YUCATAN. THE HURRICANE IS HEADING ON A STEADY WEST-NORTHWESTWARD TRACK OR 285 DEGREES AT 16 KNOTS. THE STRONG HIGH TO THE NORTH OF THE HURRICANE IS EXPECTED TO BUILD WESTWARD AS INDICATED BY THE LATEST GLOBAL MODEL RUNS. THIS PATTERN CALLS FOR NO SIGNIFICANT CHANGE IN TRACK OR SPEED THROUGH 5 DAYS...BUT PERHAPS WITH A SLIGHT TURN MORE TO THE WEST IN A DAY OR SO. THE GFDL CONTINUES TO BE ON THE NORTHERN SIDE OF THE GUIDANCE ENVELOPE AND IS THE ONLY MODEL THAT BRINGS THE HURRICANE OVER THE SOUTHERN TEXAS COAST. THE OFFICIAL FORECAST GOES ALONG WITH THE CONSENSUS OF THE DYNAMICAL MODELS AND KEEPS DEAN IN THE BAY OF CAMPECHE OR SOUTHERN GULF OF MEXICO BY DAY FOUR. THERE COULD BE VERY UNCERTAIN DAYS AHEAD SINCE THE GFDL HAS HAD A VERY RELIABLE TRACK RECORD. FORECAST POSITIONS AND MAX WINDS INITIAL 18/2100Z 16.1N 70.2W 130 KT 12HR VT 19/0600Z 16.8N 72.6W 135 KT 24HR VT 19/1800Z 17.7N 76.0W 135 KT 36HR VT 20/0600Z 18.5N 79.3W 125 KT 48HR VT 20/1800Z 19.5N 83.0W 140 KT 72HR VT 21/1800Z 21.5N 90.0W 100 KT 96HR VT 22/1800Z 23.0N 96.0W 105 KT 120HR VT 23/1800Z 24.5N 101.5W 40 KT...INLAND $$ FORECASTER AVILA