000 WTNT43 KNHC 272035 TCDAT3 TROPICAL STORM RINA DISCUSSION NUMBER 19 NWS NATIONAL HURRICANE CENTER MIAMI FL AL182011 400 PM CDT THU OCT 27 2011 SATELLITE IMAGERY...RADAR DATA...AND REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER INDICATE THAT RINA CONTINUES TO WEAKEN. THE PREVIOUSLY OBSERVED STRONG CONVECTIVE BURST HAS DISSIPATED...AND THERE IS CURRENTLY LITTLE CONVECTION NEAR THE CENTER. THE AIRCRAFT HAS REPORTED MAXIMUM 850 MB FLIGHT-LEVEL WINDS OF 58 KT AND SURFACE WIND ESTIMATES OF 48 KT FROM THE STEPPED FREQUENCY MICROWAVE RADIOMETER. BASED ON THESE DATA...THE INITIAL INTENSITY IS DECREASED TO 50 KT. THE INITIAL MOTION IS NOW 350/6. THE TROPICAL CYCLONE SHOULD MOVE SLOWLY NORTHWARD NEAR THE EAST COAST OF THE YUCATAN PENINSULA FOR THE NEXT 12-24 HOURS ON THE WEST SIDE OF A MID/UPPER-LEVEL RIDGE OVER THE CARIBBEAN SEA. AFTER THAT...THE DYNAMICAL MODELS ARE IN GOOD AGREEMENT THAT A COMBINATION OF RINA WEAKENING TO A SHALLOW VORTEX AND RISING LOW-LEVEL PRESSURES TO ITS NORTHWEST SHOULD CAUSE RINA TO TURN SOUTHWARD. WHILE THERE REMAIN DIFFERENCES IN THE DETAILS...THE GUIDANCE SUGGESTS THAT RINA OR ITS REMNANTS WILL MEANDER OVER THE NORTHWEST CARIBBEAN SEA OR THE ADJACENT LAND AREAS FOR THE REST OF THE FORECAST PERIOD. THE FORECAST TRACK AFTER 48 HOURS SHOWS A SLIGHTLY FASTER SOUTHWARD AND THEN SOUTH- SOUTHWESTWARD MOTION THAN THE OLD FORECAST. WHILE THIS TRACK IS NEAR THE CENTER OF THE TRACK GUIDANCE ENVELOPE...THE SOUTHWARD MOTION IS SLOWER THAN THAT OF MOST OF THE DYNAMICAL GUIDANCE. MODERATE TO STRONG SOUTHERLY VERTICAL WIND SHEAR IS LIKELY TO PERSIST NEAR OR OVER RINA FOR THE NEXT 72 HOURS OR SO. THIS... ALONG WITH LAND INTERACTION AND DRY AIR ENTRAINING INTO THE CYCLONE...SHOULD CAUSE CONTINUED WEAKENING. BASED ON THIS AND THE CURRENT TRENDS...THE NEW INTENSITY FORECAST CALLS FOR RINA TO MEET AN EARLIER DEMISE THAN ON THE PREVIOUS ADVISORY...WITH THE CYCLONE EXPECTED TO WEAKEN TO A TROPICAL DEPRESSION BY 48 HOURS AND TO DEGENERATE TO A REMNANT LOW BY 72 HOURS. THE DYNAMICAL MODELS SUGGEST THE SHEAR MAY DECREASE AFTER 72 HOURS. HOWEVER...GIVEN THE UNCERTAINTIES OF THE STRUCTURE AND LOCATION OF THE REMNANTS OF RINA THE FORECAST OF REMNANT LOW AT 120 HOURS WILL REMAIN UNCHANGED. FORECAST POSITIONS AND MAX WINDS INIT 27/2100Z 19.8N 87.2W 50 KT 60 MPH 12H 28/0600Z 20.6N 87.2W 45 KT 50 MPH...INLAND 24H 28/1800Z 21.3N 87.1W 40 KT 45 MPH...INLAND 36H 29/0600Z 21.2N 86.5W 35 KT 40 MPH...OVER WATER 48H 29/1800Z 20.9N 86.1W 30 KT 35 MPH 72H 30/1800Z 20.0N 86.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 31/1800Z 18.5N 86.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 01/1800Z 17.0N 87.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ FORECASTER BEVEN