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| #381760 (Received by flhurricane at: 4:44 AM 08.Oct.2010) TCDAT2 TROPICAL STORM OTTO DISCUSSION NUMBER 9 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 500 AM AST FRI OCT 08 2010 SATELLITE IMAGES INDICATE THAT DEEP AND SYMMETRIC CONVECTION HAS INTENSIFIED NEAR THE CENTER OF OTTO DURING THE PAST SEVERAL HOURS WITH AN OCCASIONAL HINT OF A WARM SPOT IN THE INFRARED CHANNEL. UNFORTUNATELY THERE HAVE BEEN NO RECENT MICROWAVE OVERPASSES TO HELP LOCATE THE CENTER...WHICH HANDICAPS THE INTENSITY ESTIMATE. DVORAK NUMBERS FROM TAFB/SAB ARE 65/55 KT...AND A BLEND OF THESE DATA GIVE AN INITIAL WIND SPEED OF 60 KT. THE SHIPS MODEL SUGGESTS THAT SOUTHWESTERLY SHEAR WILL RELAX NEAR OTTO DURING THE NEXT 24 HOURS...WHICH SHOULD ALLOW THE STORM TO BECOME A HURRICANE. GUIDANCE IS NOW IN AGREEMENT ON OTTO ATTAINING HURRICANE STRENGTH LATER TODAY. SINCE ANY SUBTROPICAL CHARACTERISTICS ARE NOW GONE...I DO NOT SEE A GOOD REASON TO DISCOUNT THE GUIDANCE...AND THE OFFICIAL FORECAST IS RAISED FROM THE PREVIOUS ONE...JUST BELOW THE MODEL CONSENSUS. WEAKENING SEEMS LIKELY IN A COUPLE OF DAYS DUE TO WATERS COOLING BELOW 26C AND INCREASING SOUTHWESTERLY SHEAR. BASED PRIMARILY ON CONTINUITY FROM THE PREVIOUS FORECAST TRACK...THE INITIAL MOTION IS 060/12. OTTO IS BEING ACCELERATED GENERALLY NORTHEASTWARD BY A LARGE MID-LATITUDE TROUGH OVER THE WESTERN ATLANTIC OCEAN. THE TROPICAL CYCLONE SHOULD BECOME EMBEDDED WITHIN FAST SOUTHWESTERLY FLOW FOR THE NEXT TWO TO THREE DAYS...AND MODEL GUIDANCE IS IN GOOD AGREEMENT ON THE TRACK DURING THAT TIME. HOWEVER...LARGE DISAGREEMENTS OCCUR IN THE LONG RANGE AS IT IS NOT CLEAR WHETHER OTTO WILL REMAIN WITHIN THE MID-LATITUDE FLOW OR TURN MORE TO THE EAST AND SOUTHEAST AROUND THE WEST SIDE OF A TROUGH OVER THE FAR NORTHEASTERN ATLANTIC OCEAN. THE MOST RELIABLE GUIDANCE SHOW THE LATTER SOLUTION...AND THE OFFICIAL FORECAST WILL STAY WITH THAT SCENARIO. EXTRATROPICAL TRANSITION WILL PROBABLY BEGIN AFTER THE CYCLONE CROSSES 30N AS THE CYCLONE MOVES OVER COOLER WATERS AND INTO HIGHER SHEAR. FSU PHASE SPACE DIAGRAMS...HOWEVER...SUGGEST THAT OTTO WILL RETAIN ITS WARM CORE FOR SEVERAL DAYS. THE MODEL THICKNESS FIELDS DO SHOW THE CYCLONE DEVELOPING FRONTAL FEATURES IN ABOUT THREE DAYS... THUS EXTRATROPICAL STATUS IS SHOWN AT THAT TIME. FORECAST POSITIONS AND MAX WINDS INITIAL 08/0900Z 24.8N 65.5W 60 KT 12HR VT 08/1800Z 25.9N 63.6W 65 KT 24HR VT 09/0600Z 28.0N 60.1W 70 KT 36HR VT 09/1800Z 30.3N 55.2W 75 KT 48HR VT 10/0600Z 33.2N 49.0W 70 KT 72HR VT 11/0600Z 38.5N 34.0W 55 KT...POST-TROP/EXTRATROP 96HR VT 12/0600Z 39.0N 25.5W 45 KT...POST-TROP/EXTRATROP 120HR VT 13/0600Z 36.5N 21.5W 35 KT...POST-TROP/EXTRATROP $$ FORECASTER BLAKE |
