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| #6190 (Received by flhurricane at: 4:51 AM 27.Aug.2004) TCDAT1 HURRICANE FRANCES DISCUSSION NUMBER 10 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT FRI AUG 27 2004 FOR A COUPLE OF HOURS BEFORE 0600Z THERE WAS A WELL-DEFINED EYE EMBEDDED WITHIN A SYMMETRIC AREA OF DEEP CONVECTION. THIS GAVE THE APPEARANCE OF A STRONGER HURRICANE SINCE OBJECTIVE NUMBERS WERE NEAR 5.0 AND A SUBJECTIVE CLASSIFICATION WOULD GIVE A 5.5 ON THE DVORAK SCALE DURING THAT PERIOD. AT THE CLASSIFICATION TIME...06Z... THE EYE BECAME LESS DEFINED AND CONVECTION WEAKENED A LITTLE. THIS RESULTED IN THE SAME 4.5 T-NUMBERS THAT WERE PROVIDED AT 00Z. THEREAFTER...MORE RECENT SATELLITE IMAGES SHOW A RAGGED EYE SO... THE INITIAL INTENSITY HAS BEEN INCREASED TO 80 KNOTS. THE OUTFLOW REMAINS VERY WELL ESTABLISHED AND THE OCEAN IS WARM. IN ADDITION... GLOBAL MODELS DEVELOP A LARGE UPPER-LEVEL ANTICYCLONE OVER/AROUND FRANCES WITH THE CIRCULATION OF THE HURRICANE EXTENDING UP TO 200 MB. THIS PATTERN IS COMMON IN INTENSE HURRICANES. THEREFORE... ADDITIONAL STRENGTHENING IS INDICATED. THE INTENSITY FORECAST ASSUMES THAT THE UNFAVORABLE UPPER-LEVEL WESTERLIES CURRENTLY OBSERVED IN THE AREA WHERE THE HURRICANE IS EXPECTED TO BE IN 3 DAYS WILL WEAKEN AS SUGGESTED BY GLOBAL MODELS. FRANCES APPEARS TO BE MOVING TOWARD THE WEST-NORTHWEST OR 295 DEGREES AT 12 KNOTS. THE SUBTROPICAL RIDGE IS EXPECTED TO WEAKEN TEMPORARILY AS A MID-LEVEL TROUGH MOVES EASTWARD. THIS WOULD RESULT IN A DECREASE IN FORWARD SPEED AND PERHAPS A TURN MORE TO THE NORTHWEST. IN FACT...THE HURRICANE MAY BE DOING SO AS WE SPEAK. HOWEVER...UNANIMOULSY ALL GLOBAL MODELS ARE REBUILDING THE SUBTROPICAL RIDGE. THIS PATTERN WOULD FORCE THE HURRICANE TO MAKE A LEFT TURN IN A COUPLE OF DAYS. THE STRENGTH OF THE SUBTROPICAL RIDGE WILL CONTROL HOW MUCH THE HURRICANE WILL TURN WESTWARD. THE GFS AND THE CANADIAN GLOBAL MODELS ARE THE MOST AGGRESSIVE BRINGING THE HURRICANE WESTWARD BASICALLY ALONG 20 NORTH FOR THE NEXT SEVERAL DAYS. THE UK AND THE GFDL HAVE ALSO SHIFTED THE TRACK MORE TO THE WEST BUT NOT AS MUCH AS THE GFS. THE OFFICIAL FORECAST IS HALFWAY BETWEEN THE GFS AND THE UK MODELS. THE TREND OF THE GLOBAL MODELS SUGGEST THAT THIS HURRICANE MUST BE MONITORED VERY CAREFULLY OVER THE NEXT SEVERAL DAYS. ONCE AGAIN...IT SHOULD BE STRESSED THAT 4- AND 5-DAY FORECAST POINTS CAN EASILY BE IN ERROR BY SEVERAL HUNDRED MILES. FORECASTER AVILA FORECAST POSITIONS AND MAX WINDS INITIAL 27/0900Z 14.5N 48.4W 80 KT 12HR VT 27/1800Z 15.3N 50.3W 85 KT 24HR VT 28/0600Z 16.5N 52.0W 95 KT 36HR VT 28/1800Z 18.0N 53.5W 100 KT 48HR VT 29/0600Z 19.0N 55.5W 100 KT 72HR VT 30/0600Z 20.5N 58.5W 105 KT 96HR VT 31/0600Z 21.0N 61.5W 105 KT 120HR VT 01/0600Z 21.5N 65.0W 105 KT |
