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| #468576 (Received by flhurricane at: 4:50 PM 26.Oct.2011) TCDAT3 HURRICANE RINA DISCUSSION NUMBER 15 NWS NATIONAL HURRICANE CENTER MIAMI FL AL182011 400 PM CDT WED OCT 26 2011 RECENT SATELLITE IMAGERY...DATA FROM THE BELIZE CITY RADAR...AND REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT SUGGEST THAT RINA HAS CHANGED LITTLE IN STRENGTH DURING THE PAST FEW HOURS. THE AIRCRAFT HAS REPORTED 700 MB FLIGHT-LEVEL WINDS OF 79 KT AND SFMR SURFACE WIND ESTIMATES OF 75-78 KT...WHILE AN EYEWALL DROPSONDE SUGGESTS SURFACE WINDS NEAR 70 KT. THE INITIAL INTENSITY OF 75 KT IS A COMPROMISE BETWEEN THESE DATA. THE AIRCRAFT DATA SUGGEST THE VORTEX IS TILTED WITH HEIGHT...AS DROPSONDES AT THE FLIGHT-LEVEL CENTER HAVE CONSISTENTLY REPORTED 25-30 KT SURFACE WINDS. THIS TILT IS LIKELY DUE TO 20 KT OF SOUTHERLY VERTICAL WIND SHEAR DEPICTED IN ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN. RITA HAS CONTINUED ITS SLOW RIGHT TURN...AND THE INITIAL MOTION IS NOW 310/5. THE FORECAST TRACK AND PHILOSOPHY ARE UNCHANGED FOR THE FIRST 48 HOURS...WITH THE HURRICANE FORECAST TO MOVE SLOWLY NORTHWARD AND THEN NORTH-NORTHEASTWARD NEAR OR OVER THE NORTHEASTERN PORTION OF THE YUCATAN PENINSULA AS AN UPPER-LEVEL TROUGH AND ASSOCIATED COLD FRONT MOVE ACROSS THE SOUTHEASTERN UNITED STATES AND THE GULF OF MEXICO. THE TRACK FORECAST BECOMES VERY PROBLEMATIC AFTER 48 HOURS DUE TO UNCERTAINTIES OF HOW RINA INTERACTS WITH THE TROUGH AND HOW LONG IT HOLDS TOGETHER VERTICALLY. THE GFDL AND GFDN MODELS CONTINUE TO FORECAST THE SYSTEM TO MOVE EAST-NORTHEASTWARD OVER FLORIDA OR THE FLORIDA STRAITS INTO THE ATLANTIC. THE ECMWF...NOGAPS...UKMET...AND CANADIAN MODELS NOW FORECAST RINA OR ITS REMNANTS TO MAKE A HAIRPIN TURN AND MOVE SOUTHWARD NEAR THE EAST COAST OF YUCATAN. THE GFS...GFS ENSEMBLE MEAN...AND HWRF MODELS ARE BETWEEN THESE EXTREMES...FORECASTING THE CYCLONE TO MOVE SLOWLY EASTWARD AND THEN SOUTHEASTWARD NEAR OR OVER WESTERN CUBA. THE NEW FORECAST TRACK FOLLOWS THESE MODELS AND IS THUS SHIFTED SOUTH OF THE PREVIOUS TRACK. THIS LATTER PART OF THE FORECAST TRACK REMAINS A LOW CONFIDENCE FORECAST. RINA IS FORECAST TO BE IN A MODERATE SHEAR ENVIRONMENT FOR THE NEXT 24-36 HOURS. THIS...COMBINED WITH EXPECTED LAND INTERACTION... SUGGESTS IT SHOULD SLOWLY WEAKEN DURING THIS TIME. AFTER 36 HOURS...THE CYCLONE SHOULD ENCOUNTER STRONG SHEAR AS THE MID/UPPER-LEVEL FLOW TRIES TO STEER IT EAST-NORTHEASTWARD AND THE LOW-LEVEL FLOW TRIES TO STEER IT SOUTHWARD OR SOUTHWESTWARD. THIS SHOULD CAUSE RINA TO WEAKEN IN AGREEMENT WITH ALL THE INTENSITY GUIDANCE. THE NEW INTENSITY FORECAST CALLS FOR A FASTER WEAKENING THAN PREVIOUSLY SHOWN...IN BEST AGREEMENT WITH THE DECAY SHIPS MODEL. IT IS POSSIBLE THAT THIS RELATIVELY SMALL SYSTEM COULD WEAKEN FASTER THAN CURRENTLY FORECAST AND BECOME A REMNANT LOW BY 120 HOURS OR EARLIER. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 18.2N 85.9W 75 KT 85 MPH 12H 27/0600Z 18.7N 86.5W 75 KT 85 MPH 24H 27/1800Z 20.0N 86.9W 70 KT 80 MPH 36H 28/0600Z 21.4N 86.9W 60 KT 70 MPH...INLAND 48H 28/1800Z 22.5N 86.5W 60 KT 70 MPH...OVER WATER 72H 29/1800Z 23.0N 84.5W 50 KT 60 MPH 96H 30/1800Z 22.5N 83.0W 35 KT 40 MPH...INLAND 120H 31/1800Z 22.5N 83.0W 25 KT 30 MPH...INLAND $$ FORECASTER BEVEN |
