000 WTNT43 KNHC 260845 TCDAT3 HURRICANE RINA DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL AL182011 400 AM CDT WED OCT 26 2011 THE EYE CONTINUES TO BE OBSCURED ON GEOSTATIONARY IMAGERY AND THE ORGANIZATION OF THE HURRICANE HAS CHANGED LITTLE OVER THE PAST SEVERAL HOURS. AN AIR FORCE HURRICANE HUNTER PLANE MEASURED PEAK 700 MB FLIGHT-LEVEL WINDS OF 104 KT AND MAXIMUM BELIEVABLE SFMR-OBSERVED SURFACE WINDS OF NEAR 90 KT...AND THE INITIAL WIND SPEED IS HELD AT 95 KT FOR THIS ADVISORY. WATER VAPOR IMAGERY CONTINUES TO DEPICT A WELL-DEFINED UPPER-LEVEL OUTFLOW PATTERN... AND ANALYSES FROM UW/CIMSS SUGGEST THAT STRONG VERTICAL SHEAR HAS NOT YET REACHED THE CORE OF THE HURRICANE. THEREFORE...RINA STILL HAS AN OPPORTUNITY TO INTENSIFY INTO A MAJOR HURRICANE BEFORE IT REACHES THE YUCATAN PENINSULA. IT SHOULD BE NOTED...HOWEVER...THAT THE OCEANIC HEAT CONTENT BELOW THE CYCLONE SHOULD DIMINISH FROM THIS POINT ONWARD...WHICH COULD BE A MITIGATING FACTOR FOR STRENGTHENING. THE OFFICIAL WIND SPEED FORECAST CONTINUES TO SHOW RINA INTENSIFYING TO CATEGORY 3 STATUS LATER TODAY. SOME DECREASE IN STRENGTH IS LIKELY TO OCCUR DUE TO THE INTERACTION WITH THE YUCATAN PENINSULA. BY DAYS 2-3...WHEN RINA IS FORECAST TO MOVE OVER THE SOUTHEASTERN GULF OF MEXICO...SIGNIFICANTLY HIGHER SHEAR DUE TO STRONG UPPER-LEVEL WESTERLIES SHOULD CAUSE A WEAKENING TREND. THE OFFICIAL INTENSITY FORECAST IS CLOSE TO THE NUMERICAL CONSENSUS AND SLIGHTLY ABOVE THE STATISTICAL-DYNAMICAL GUIDANCE. CENTER FIXES FROM THE HURRICANE HUNTERS INDICATE THAT RINA CONTINUES TO MOVE VERY SLOWLY...OR 280/4. AS A MID-TROPOSPHERIC RIDGE TO THE NORTH SHIFTS EASTWARD DURING THE NEXT DAY OR TWO...THE HURRICANE SHOULD TURN NORTHWESTWARD AND THEN NORTHWARD. THE TRACK GUIDANCE MODELS ARE IN REASONABLY GOOD AGREEMENT ON THIS SCENARIO FOR THE FIRST 48 HOURS OF THE FORECAST PERIOD. BY 3 TO 4 DAYS...A LARGE 500 MB TROUGH MOVES TO THE U.S. EAST COAST...RESULTING IN A STRENGTHENING MID-TROPOSPHERIC WEST-SOUTHWESTERLY FLOW OVER THE EASTERN GULF OF MEXICO. IF RINA WERE TO MAINTAIN HURRICANE INTENSITY BEYOND DAY 3 OR SO...AND THEREFORE REMAIN A DEEP-LAYER VORTEX...IT WOULD LIKELY ACCELERATE EAST-NORTHEASTWARD. HOWEVER THE MAJORITY OF THE GUIDANCE...AND THE OFFICIAL FORECAST...SHOW SIGNIFICANT WEAKENING IN THAT TIME FRAME. THEREFORE THE OFFICIAL TRACK FORECAST...LIKE THE PREVIOUS ONE...SHOWS ONLY A SLOW EASTWARD MOTION NEAR THE END OF THE PERIOD. THIS IS REASONABLY CLOSE TO THE LATEST GFS TRACK. IT IS WORTH REPEATING THAT THERE IS GREAT UNCERTAINTY AS TO WHERE RINA WILL BE LOCATED BY THE WEEKEND. FORECAST POSITIONS AND MAX WINDS INIT 26/0900Z 17.5N 85.2W 95 KT 110 MPH 12H 26/1800Z 18.2N 85.8W 100 KT 115 MPH 24H 27/0600Z 19.2N 86.6W 100 KT 115 MPH 36H 27/1800Z 20.5N 87.0W 100 KT 115 MPH 48H 28/0600Z 21.8N 86.6W 85 KT 100 MPH 72H 29/0600Z 23.5N 84.5W 70 KT 80 MPH 96H 30/0600Z 23.5N 83.0W 60 KT 70 MPH 120H 31/0600Z 23.5N 82.0W 45 KT 50 MPH $$ FORECASTER PASCH