000 WTNT43 KNHC 261457 TCDAT3 HURRICANE RINA DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL AL182011 1000 AM CDT WED OCT 26 2011 RINA HAS A SOMEWHAT RAGGED APPEARANCE THIS MORNING. THE EYE IS NOT APPARENT IN VISIBLE IMAGERY...AND DATA FROM THE RADARS AT BELIZE CITY AND ON THE TRMM SATELLITE SUGGEST THE EYEWALL HAS LOST SOME DEFINITION. WHILE THE EYEWALL CLOUD TOP TEMPERATURES ARE COLDER THAN -80C...THE OVERALL AMOUNT OF CONVECTION ASSOCIATED WITH THE CYCLONE HAS DECREASED DURING THE PAST SEVERAL HOURS. IN ADDITION...THE OUTFLOW HAS DIMINISHED SINCE YESTERDAY...AND ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN SUGGEST 15-20 KT OF SOUTHERLY VERTICAL WIND SHEAR. THE INITIAL INTENSITY IS KEPT AT 95 KT FOR THIS ADVISORY...BUT THIS COULD BE GENEROUS AND IT IS QUITE POSSIBLE THAT THE NOAA HURRICANE HUNTER AIRCRAFT ABOUT TO REACH THE STORM WILL FIND RINA HAS WEAKENED. THE RECENT CENTER FIXES INDICATE THAT RINA HAS TURNED TOWARD THE RIGHT DURING THE PAST SEVERAL HOURS WITH THE INITIAL MOTION NOW 290/4. RINA IS CURRENTLY EMBEDDED IN A MID-LEVEL RIDGE...WITH A STRONG LOW-LEVEL RIDGE NORTH OF THE HURRICANE AND AN UPPER-LEVEL ANTICYCLONE TO ITS EAST OVER THE CENTRAL CARIBBEAN. THE DYNAMICAL MODELS FORECAST THE RIDGES TO THE NORTH AND WEST TO WEAKEN DURING THE NEXT 48-72 HOURS AS A TROUGH IN THE WESTERLIES AND ASSOCIATED COLD FRONT MOVE INTO THE GULF OF MEXICO. THIS EVOLUTION SHOULD CAUSE RINA TO GRADUALLY TURN NORTHWARD NEAR THE EAST COAST OF THE YUCATAN PENINSULA. THE TRACK GUIDANCE IS IN GOOD AGREEMENT ON THIS PART OF THE FORECAST...AND THE NEW FORECAST TRACK IS SIMILAR TO THE OLD ONE. AFTER 72 HOURS...RINA IS EXPECTED TO MOVE INTO AN ENVIRONMENT WHERE THE MID/UPPER-LEVEL FLOW TRIES TO STEER THE CYCLONE NORTHEASTWARD WHILE THE LOW-LEVEL FLOW TRIES TO STEER IT SOUTHWARD OR SOUTHWESTWARD. THIS SHOULD CAUSE RINA TO SHEAR APART...BUT THE MODELS DISAGREE ON WHEN THIS WILL HAPPEN AND THUS ARE IN POOR AGREEMENT ON THE FORECAST TRACK. THE ECMWF AND CANADIAN WEAKEN RINA VERY QUICKLY AND KEEP THE LOW-LEVEL REMNANT NEAR YUCATAN...WHILE THE GFDL FORECASTS A STRONGER CYCLONE TO CROSS SOUTH FLORIDA INTO THE ATLANTIC. THE OTHER MODELS ARE BETWEEN THESE EXTREMES. THE LATTER PORTION OF THE NEW FORECAST TRACK IS SIMILAR TO THE PREVIOUS TRACK...IN BEST AGREEMENT WITH THE GFS AND NOGAPS MODELS. HOWEVER...THIS IS A LOW CONFIDENCE FORECAST. SINCE THE OUTFLOW IS LESS IMPRESSIVE THAN 24 HOURS AGO AND THE SHEAR IS FORECAST TO INCREASE FURTHER...IT APPEARS THAT RINA HAS RUN OUT OF TIME TO INTENSIFY. THE INTENSITY FORECAST NOW CALLS FOR THE HURRICANE TO GRADUALLY WEAKEN DURING THE NEXT 12-24 HOURS...WITH A FASTER WEAKENING AT 36-48 HOURS DUE TO LAND INTERACTION. DUE TO THE UNCERTAINTY OF JUST HOW QUICKLY RINA WILL SHEAR APART OVER THE GULF OF MEXICO...THE FORECAST KEEPS RINA A HURRICANE THROUGH 72 HOURS AND A TROPICAL STORM THROUGH 120 HOURS IN BEST AGREEMENT WITH THE SHIPS AND LGEM MODELS. HOWEVER...IT IS POSSIBLE THAT THE CYCLONE COULD WEAKEN MUCH FASTER THAN CURRENTLY FORECAST. FORECAST POSITIONS AND MAX WINDS INIT 26/1500Z 17.9N 85.5W 95 KT 110 MPH 12H 27/0000Z 18.5N 86.2W 95 KT 110 MPH 24H 27/1200Z 19.5N 87.0W 90 KT 105 MPH 36H 28/0000Z 20.8N 87.1W 80 KT 90 MPH...INLAND 48H 28/1200Z 22.0N 87.0W 75 KT 85 MPH...OVER WATER 72H 29/1200Z 23.0N 85.0W 65 KT 75 MPH 96H 30/1200Z 23.5N 83.0W 55 KT 65 MPH 120H 31/1200Z 23.5N 82.5W 45 KT 50 MPH $$ FORECASTER BEVEN