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| #45267 (Received by flhurricane at: 5:03 AM 11.Sep.2005) TCDAT1 HURRICANE OPHELIA DISCUSSION NUMBER 20 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT SUN SEP 11 2005 AIR FORCE RECON MEASURED A PEAK 700 MB FLIGHT LEVEL WIND OF 85 KT ABOUT 25 N MI WEST OF THE CENTER AS THEY DEPARTED FROM THEIR LAST FIX AT AROUND 06Z. THIS IS THE STRONGEST FLIGHT LEVEL WIND REPORTED TO DATE IN OPHELIA AND SUPPORTS INCREASING THE INTENSITY TO 75 KT. THE MOST RECENT CENTRAL PRESSURE MEASURED BY DROPSONDE WAS 978 MB...BASICALLY UNCHANGED DURING THE PAST SEVERAL HOURS. THE 75 KT INTENSITY IS ALSO CONSISTENT WITH THE LATEST DVORAK ESTIMATES... ALTHOUGH THE DATA T NUMBERS ARE ONLY 4.0 DUE TO THE SLIGHT DEGRADATION OF THE SATELLITE APPEARANCE SINCE COMING OUT OF THE GOES-12 ECLIPSE PERIOD... SO IT IS POSSIBLE THAT OPHELIA IS AGAIN A LITTLE WEAKER THAN 75 KT. WHILE OPHELIA MIGHT BE WITHIN AN ENVIRONMENT MORE CONDUCIVE FOR STRENGTHENING ONCE THE UPPER LEVEL RIDGE REACHES THE EAST COAST AND THE LONGITUDE OF THE HURRICANE IN A COUPLE OF DAYS... THE SLOW MOTION OF OPHELIA COULD CAUSE OCEAN UPWELLING AND PROVIDE A COUNTERACTING LIMITATION ON THE INTENSITY. GIVEN THIS REASONING AND THAT NONE OF THE INTENSITY GUIDANCE FORECASTS SIGNIFICANT CHANGES... THE OFFICIAL FORECAST MAINTAINS 75 KT THROUGH 72 HOURS...FOLLOWED BY WEAKENING DUE TO INCREASING SHEAR AND COOLER WATERS AHEAD OF THE NEXT MIDLATITUDE TROUGH. OPHELIA REMAINS STATIONARY AND SANDWICHED BETWEEN STRONG AND DEEP HIGH PRESSURE CENTERS OVER THE WESTERN HALF OF THE ATLANTIC AND OVER THE EAST HALF OF THE UNITED STATES. LACKING A SUBSTANTIAL CHANGE IN THIS PATTERN DURING THE NEXT COUPLE OF DAYS...VERY SLOW MOTION IS EXPECTED. THE MIDLATITUDE PATTERN IS FORECAST BY THE DYNAMICAL MODELS TO BECOME MORE PROGRESSIVE AND MOVE THE U.S. RIDGE OFFSHORE IN ABOUT 3 DAYS...FOLLOWED BY THE NEXT TROUGH WHICH SHOULD THEN FINALLY GET OPHELIA MOVING NORTHEASTWARD. PERHAPS DUE IN PART TO THE SYNOPTIC SURVEILLANCE MISSION BY THE NOAA G-IV JET LAST NIGHT... SOME OF THE DYNAMICAL MODELS HAVE COME INTO BETTER AGREEMENT ON THE FORECAST TRACK. THE 00Z GFS HAS SHIFTED MORE THAN 100 MILES WESTWARD AND NOW FORECASTS LANDFALL OVER THE NORTH CAROLINA OUTER BANKS IN THREE TO FOUR DAYS. THIS SHIFT BRINGS THE GFS INTO REMARKABLY GOOD AGREEMENT WITH THE 00Z RUNS OF THE NOGAPS AND UKMET. THE NEW OFFICIAL FORECAST IS ADJUSTED SOMEWHAT TO THE EAST AT 72 HOURS...AND IS A LITTLE FASTER THERAFTER... TO CONFORM WITH THIS GUIDANCE...BUT IS ESSENTIALLY UNCHANGED DURING THE PERIOD OF SLOW MOTION THROUGH DAY TWO. THE NEW FORECAST IMPLIES A LESSER POSSIBILITY OF OPHELIA DIRECTLY IMPACTING THE EXTREME SOUTHERN END OF THE HURRICANE WATCH AREA... SO A SMALL PORTION OF THE WATCH HAS BEEN DISCONTINUED...FROM EDISTO BEACH SOUTHWARD. HOWEVER... THROUGHOUT THE REMAINDER OF THE HURRICANE WATCH AREA... SINCE OPHELIA IS NOT YET MOVING... IT IS STILL MUCH TOO EARLY TO RULE OUT THE POSSIBILITY OF HURRICANE CONDITIONS. FORECASTER KNABB FORECAST POSITIONS AND MAX WINDS INITIAL 11/0900Z 31.7N 75.9W 75 KT 12HR VT 11/1800Z 31.6N 76.0W 75 KT 24HR VT 12/0600Z 31.6N 76.2W 75 KT 36HR VT 12/1800Z 32.0N 76.5W 75 KT 48HR VT 13/0600Z 32.6N 76.7W 75 KT 72HR VT 14/0600Z 34.0N 76.5W 75 KT 96HR VT 15/0600Z 36.5N 75.0W 50 KT 120HR VT 16/0600Z 39.5N 71.0W 40 KT |
