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| #45220 (Received by flhurricane at: 10:40 PM 10.Sep.2005) TCDAT1 HURRICANE OPHELIA DISCUSSION NUMBER 19 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT SAT SEP 10 2005 SATELLITE IMAGERY DURING THE EVENING SHOWS THAT THE LOW-LEVEL CENTER OF OPHELIA HAS BECOME PARTIALLY EXPOSED ON THE WESTERN EDGE OF THE CONVECTION. REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE A CENTRAL PRESSURE OF 977-978 MB AND AN EYEWALL OPEN IN THE SOUTH SEMICIRCLE. MAXIMUM FLIGHT-LEVEL WINDS AT 700 MB ARE 79 KT IN THE SOUTHWEST QUADRANT...WHILE EYEWALL DROPSONDES IN THE SOUTHEAST AND NORTHEAST QUADRANTS INDICATED 60-65 KT SURFACE WINDS. SINCE THE AIRCRAFT DATA IS ESSENTIALLY IDENTICAL TO THE PREVIOUS FLIGHT...THE INITIAL INTENSITY REMAINS 70 KT. OPHELIA HAS DRIFTED A LITTLE TO THE EAST-NORTHEAST OVER THE PAST 6 HR BUT IS NOW NEARLY STATIONARY. WATER VAPOR IMAGERY INDICATES LARGE MID/UPPER-LEVEL RIDGES CENTERED OVER WESTERN TENNESSEE AND NEAR 25N57W...WITH OPHELIA IN BETWEEN. THE LATEST LARGE-SCALE MODEL RUNS FORECAST THIS COMBINATION TO KEEP OPHELIA NEARLY STATIONARY FOR THE NEXT 2-3 DAYS...FOLLOWED BY A SLOW GENERALLY NORTHWARD MOTION AS THE U. S. RIDGE SHIFTS EASTWARD INTO THE ALTANTIC. THE GUIDANCE IS STILL WELL SPREAD...WITH THE LEFT OUTLIERS OF THE GFDN AND THE CANADIAN CALLING FOR LANDFALL IN SOUTH CAROLINA AND THE RIGHT OUTLIERS OF THE GFS AND GFDL CALLING FOR THE STORM TO PASS EAST OF CAPE HATTERAS. THE NEW FORECAST TRACK IS SHIFTED A LITTLE TO THE RIGHT AND A LITTLE SLOWER THAN THE PREVIOUS PACKAGE...AND IS ON THE LEFT SIDE OF THE MAIN ENVELOPE OF GUIDANCE. THE NEW TRACK HAS A SMALL LOOP IN THE FIRST 24-36 HR...AS MUCH OF THE GUIDANCE SUGGESTS THAT OPHELIA WILL DRIFT SOUTHWARD DURING PART OF THAT TIME. OPHELIA CONTINUES TO EXPERIENCE LIGHT TO MODERATE WESTERLY SHEAR... AND WATER VAPOR IMAGERY SHOWS ABUNDANT DRY AIR WEST OF THE CYCLONE. THESE HAVE PROBABLY ERODED THE CONVECTIVE STRUCTURE TO SOME DEGREE. HOWEVER...THE LARGEST FACTOR CONTROLLING THE INTENSITY IS LIKELY TO BE SEA SURFACE TEMPERATURES AND UPWELLING OF COLD WATER UNDERNEATH THE SLOW-MOVING STORM. NOAA BUOY 41002 LOCATED NORTHEAST OF THE CENTER IS REPORTING AN SST OF 27.2C...AND A DRIFTING BUOY SOUTH OF THE CENTER IS REPORTING 24.4C...DOWN ALMOST 3C FROM BEFORE OPHELIA PASSED OVER IT. ELSEWHERE IN THE AREA...SSTS ARE BETWEEN 27-28C EXCEPT IN THE RELATIVELY NARROW GULF STREAM. SHOULD OPHELIA MOVE AS SLOWLY AS FORECAST...IT MAY UPWELL ENOUGH COLD WATER TO SUPPRESS DEVELOPMENT. THE GFDL...SHIPS...AND SUPERENSEMBLE ALL SHOW A LITTLE STRENGTHENING THROUGH 30 HR...AND THE INTENSITY FORECAST FOLLOWS SUIT. HOWEVER...THOSE MODELS ALL FORECAST WEAKENING AFTER 36-48 HR. THE INTENSITY FORECAST WILL NOT YET FOLLOW THAT SCENARIO...BUT IT IS A DISTINCT POSSIBILITY. THE HURRICANE WATCH REMAINS IN EFFECT FOR PORTIONS OF THE SOUTHEAST U. S. COAST WITH NO CHANGES AT THIS TIME. IF OPHELIA IS TO BEGIN A TRACK LIKE THAT OF THE GFDN OR CANADIAN TOWARD SOUTH CAROLINA...IT SHOULD HAPPEN WITHIN THE NEXT 24-36 HR. THEREFORE...IT IS TOO EARLY TO SOUND AN ALL CLEAR FOR ANY PART OF THE AREA CURRENTLY UNDER THE HURRICANE WATCH. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 11/0300Z 31.8N 75.8W 70 KT 12HR VT 11/1200Z 31.7N 75.8W 70 KT 24HR VT 12/0000Z 31.7N 76.1W 75 KT 36HR VT 12/1200Z 32.0N 76.4W 75 KT 48HR VT 13/0000Z 32.4N 76.7W 75 KT 72HR VT 14/0000Z 33.5N 77.5W 75 KT 96HR VT 15/0000Z 35.5N 76.5W 45 KT...INLAND 120HR VT 16/0000Z 38.0N 73.0W 35 KT...OVER WATER |
