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| #54309 (Received by flhurricane at: 4:43 PM 27.Oct.2005) TCDAT1 TROPICAL STORM BETA DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 PM EDT THU OCT 27 2005 BETA REMAINS A SMALL AND WELL-ORGANIZED TROPICAL STORM THIS AFTERNOON. VISIBLE IMAGERY SHOWS THAT THE CENTRAL DENSE OVERCAST PATTERN SEEN THIS MORNING HAS BECOME MORE OF A CURVED BAND PATTERN...WITH INFRARED IMAGERY SHOWING TOPS OF -75C TO -80C. AN AMSU OVERPASS AT 1547Z SHOWED A BANDING EYE UNDERNEATH THE CONVECTIVE TOPS. SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM TAFB...45 KT FROM SAB...AND 30 KT FROM AFWA. BASED ON THIS...THE INITIAL INTENSITY IS INCREASED TO 50 KT. THE INITIAL MOTION IS 350/3. BETA IS DRIFTING TOWARD A WEAKNESS IN THE SUBTROPICAL RIDGE CAUSED BY A LARGE DEEP-LAYER TROUGH OVER THE EASTERN UNITED STATES. LARGE-SCALE MODELS SUGGEST THAT AFTER A SERIES OF SHORTWAVES PASS THROUGH THE SOUTHERN END OF THE TROUGH IN THE NEXT 24-36 HR...THE TROUGH SHOULD LIFT A LITTLE NORTHWARD AND ALLOW A WEAK RIDGE TO BUILD ACROSS THE NORTHWESTERN CARIBBEAN. THIS EVOLUTION SHOULD CAUSE BETA TO DRIFT SLOWLY NORTHWARD OR NORTH-NORTHWESTWARD FOR THE NEXT 24-36 HR...FOLLOWED BY A WESTWARD MOTION. THE DYNAMICAL MODELS GENERALLY AGREE ON THIS SCENARIO... WITH THE GFS AND GFDL CALLING FOR A WESTWARD TO WEST-SOUTHWESTWARD TURN...AND THE UKMET AND NOGAPS CALLING FOR A MORE GRADUAL WESTWARD TURN. THE OFFICIAL FORECAST IS BETWEEN THESE MODELS AND IS JUST EAST AND NORTH OF THE MODEL CONSENSUS. IT SHOULD BE NOTED THAT TWO MODELS WHICH BRING BETA NORTHWARD TOWARD CUBA AND FLORIDA...LBAR AND THE CANADIAN...HAVE SHOWN A NORTHWARD BIAS IN PREVIOUS SIMILAR SITUATIONS. THEREFORE...WHILE NOT BEING RULED OUT AS POSSIBILITIES THEY ARE BEING GIVEN LITTLE WEIGHT AT THIS TIME. CONDITIONS CONTINUE TO APPEAR FAVORABLE FOR RAPID INTENSIFICATION... WITH THE RAPID INTENSIFICATION INDEX ATTACHED TO THE SHIPS MODEL SHOWING A 55 PERCENT CHANCE OF 25 KT OR GREATER STRENGTHENING DURING THE NEXT 24 HOURS. THE NEW INTENSITY FORECAST CALLS FOR THIS...MAKING BETA A HURRICANE IN JUST OVER 12 HR AND A 75 KT SYSTEM IN 24 HR. ONE POSSIBLE RESTRAINING FACTOR IS THAT THE WARM WATER OF THE SOUTHWESTERN CARIBBEAN IS RELATIVELY SHALLOW...AND THE SLOW MOTION OF BETA WILL LIKELY RESULT IN SOME UPWELLING OF COLD WATER. HOWEVER...THE EFFECTS OF THIS MAY NOT BE FELT FOR 24 HR OR MORE. THE INTENSITY FORECAST WILL CALL FOR A SLOWER DEVELOPMENT RATE AFTER 24 HR BASED ON THIS POSSIBILITY...ALTHOUGH IT WOULD NOT BE ANY SURPRISE IF BETA GOT STRONGER AND BECAME A MAJOR HURRICANE. AFTER LANDFALL...BETA SHOULD WEAKEN..ESPECIALLY WHEN IT REACHES THE MOUNTAINS OF CENTRAL AMERICA. MOST OF THE RAINFALL CURRENTLY ASSOCIATED WITH BETA IS OFFSHORE. ONCE THE STORM COMES CLOSE ENOUGH TO THE COAST TO BRING THE RAINS ONSHORE...FLOODS AND MUDSLIDES WILL BECOME SERIOUS THREATS. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 27/2100Z 11.7N 81.4W 50 KT 12HR VT 28/0600Z 12.1N 81.5W 60 KT 24HR VT 28/1800Z 12.6N 81.6W 75 KT 36HR VT 29/0600Z 13.0N 82.0W 85 KT 48HR VT 29/1800Z 13.3N 82.5W 90 KT 72HR VT 30/1800Z 13.5N 83.5W 95 KT...NEAR COAST 96HR VT 31/1800Z 13.5N 85.0W 40 KT...INLAND 120HR VT 01/1800Z 13.0N 87.0W 20 KT...INLAND DISSIPATING |
