000 WTNT41 KNHC 160858 TCDAT1 TROPICAL STORM FAY DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062008 500 AM EDT SAT AUG 16 2008 EVEN THOUGH WE CANNOT DETERMINE EXACTLY WHERE THE CENTER OF FAY IS LOCATED...SATELLITE IMAGERY AND DATA FROM AN AIR FORCE RECONNAISSANCE AIRCRAFT SUGGEST IT IS STILL INLAND...OVER SOUTH-CENTRAL HISPANIOLA NEAR THE BORDER BETWEEN THE DOMINICAN REPUBLIC AND HAITI. THE AIR FORCE PLANE CIRCUMNAVIGATED THE ENTIRE ISLAND OF HISPANIOLA DURING THE PAST FEW HOURS...ENDURING SOME RATHER TURBULENT CONDITIONS...ESPECIALLY WITHIN THE STRONGEST THUNDERSTORMS NEAR THE SOUTHERN COAST...AND WE APPRECIATE THE HARD WORK OF THE CREW. FLIGHT-LEVEL AND SFMR DATA FROM THE AIRCRAFT SUPPORT MAINTAINING THE INTENSITY AT 40 KT. FAY REMAINS BENEATH A LARGE UPPER-LEVEL ANTICYCLONE RESULTING IN WELL-ESTABLISHED OUTFLOW ALOFT...AND DESPITE THE INTERACTION WITH MOUNTAINOUS TERRAIN...THE STORM HAS A RELATIVE WELL-ORGANIZED APPEARANCE IN SATELLITE IMAGERY. THE SYSTEM APPEARS TO BE CONTINUING WESTWARD AT ABOUT 270/12 TO THE SOUTH OF A NARROW MID-LEVEL RIDGE OVER THE WESTERN ATLANTIC. THE SYNOPTIC REASONING...DYNAMICAL MODEL TRACKS...AND THE OFFICIAL FORECAST TRACK ARE NOT SIGNIFICANTLY CHANGED FROM THE PREVIOUS ADVISORY. ALL OF THE MODELS FORECAST THE MID- TO UPPER-LEVEL TROUGH OVER THE EASTERN U.S. TO GRADUALLY ERODE THE RIDGE DURING THE NEXT COUPLE OF DAYS...ALLOWING FAY TO TURN TO THE RIGHT INTO THE WEAKNESS...EVENTUALLY LEADING TO A NORTH-NORTHWESTWARD MOTION IN 3-5 DAYS. THE NEW OFFICIAL TRACK IS VERY CLOSE TO THE PREVIOUS ONE AND TO THE MODEL CONSENSUS...BUT THERE ARE RELIABLE MODELS ON BOTH SIDES OF THAT TRACK. THE GFDL AND HWRF TRACKS HEAD UP THE WESTERN PORTION OF THE FLORIDA PENINSULA IN A FEW DAYS...WHILE THE GFS AND UKMET ARE FARTHER WEST OVER THE EASTERN GULF OF MEXICO. IN THE SHORTER TERM...THE MODELS ALSO DO NOT AGREE ON WHETHER THE CENTER OF FAY WILL PASS OVER OR JUST SOUTH OF SOUTHEASTERN CUBA BEFORE TURNING NORTHWESTWARD. THESE DIFFERING SOLUTIONS AGAIN HIGHLIGHT THE PITFALLS OF FOCUSING TOO MUCH ON THE EXACT OFFICIAL FORECAST TRACK...ESPECIALLY AT THE LONGER RANGES. INTENSITY FORECASTING IS ALWAYS DIFFICULT...BUT IN THIS CASE IS MADE EVEN MORE COMPLICATED BY THE LIKELY INTERACTIONS WITH LAND DURING THE NEXT FEW DAYS. ATMOSPHERIC AND OCEAN CONDITIONS ALONG THE FORECAST TRACK APPEAR RATHER CONDUCIVE FOR STRENGTHENING...SO THE MORE TIME FAY SPENDS OVER WATER...THE STRONGER IT IS LIKELY TO BECOME...AND VICE VERSA. DYNAMICAL MODEL FIELDS INDICATE THAT THE WEAK-SHEAR ENVIRONMENT AROUND FAY SHOULD PERSIST THROUGHOUT MOST OF THE FIVE-DAY FORECAST PERIOD...WITH PERHAPS A MODEST BUT TEMPORARY INCREASE IN SHEAR IN ROUGHLY 48 HOURS. WHEN FAY IS OVER WATER...THOSE WATERS WILL BE VERY WARM. SINCE THE OFFICIAL TRACK IMPLIES AMPLE AMOUNT OF TIME OVER WATER...STEADY STRENGTHENING IS FORECAST...IN A MANNER SIMILAR TO THE GFDL MODEL. FAY COULD BE WEAKER THAN FORECAST IF ITS STAY OVER HISPANIOLA HAS SUBSTANTIALLY DISRUPTED THE CIRCULATION...OR IF IT MOVES FARTHER NORTH AND EAST AND SPENDS MORE TIME OVER CUBA. A TRACK FARTHER SOUTH AND WEST...HOWEVER...COULD ALLOW FAY TO GET STRONGER THAN WHAT IS SHOWN BELOW. FORECAST POSITIONS AND MAX WINDS INITIAL 16/0900Z 18.7N 72.0W 40 KT 12HR VT 16/1800Z 19.0N 74.0W 40 KT 24HR VT 17/0600Z 19.6N 76.4W 50 KT 36HR VT 17/1800Z 20.5N 78.3W 55 KT 48HR VT 18/0600Z 21.8N 79.9W 65 KT...NEAR S COAST OF CUBA 72HR VT 19/0600Z 25.0N 82.0W 70 KT 96HR VT 20/0600Z 28.5N 83.5W 80 KT 120HR VT 21/0600Z 32.0N 84.5W 35 KT...INLAND $$ FORECASTER KNABB