000 WTNT42 KNHC 090232 TCDAT2 HURRICANE OTTO DISCUSSION NUMBER 12 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 1100 PM AST FRI OCT 08 2010 ALTHOUGH THE CENTRAL DENSE OVERCAST FEATURE HAS DECREASED IN AREAL COVERAGE...CLOUD TOP TEMPERATURES COLDER THAN -80C HAVE PERSISTED NEAR THE UPPER-LEVEL CENTER. A 08/2217Z SSMIS MICROWAVE OVERPASS INDICATED THE EYE IS TILTED SIGNIFICANTLY DOWNSTREAM TO THE NORTHEAST BY AT LEAST 35 NMI BETWEEN THE LOW- AND MID-LEVEL CIRCULATIONS. SUBJECTIVE SATELLITE INTENSITY ESTIMATES ARE T5.0/90 KT FROM TAFB AND T4.5/77 KT FROM SAB...AND AROUND 67 KT FROM THE UW-CIMSS ADT PROGRAM. THEREFORE...THE INITIAL INTENSITY IS BEING INCREASED TO 75 KT...AND OTTO HAS LIKELY PEAKED IN STRENGTH GIVEN THE EYEWALL WAS OPEN AT ALL LEVELS IN THE AFOREMENTIONED SSMIS MICROWAVE IMAGES. THE INITIAL MOTION IS 060/18. WATER VAPOR IMAGERY INDICATES OTTO IS NOW EMBEDDED WITHIN A DEEP-LAYER WEST-SOUTHWESTERLY FLOW ON THE EAST SIDE OF A MASSIVE MID-LATITUDE TROUGH THAT EXTENDS SOUTHWARD FROM THE CANADIAN MARITIME PROVINCES TO THE NORTHERN BAHAMAS. THIS FLOW REGIME SHOULD CONTINUE TO ACCELERATE OTTO TO THE NORTHEAST OR EAST-NORTHEAST FOR THE NEXT 72 HOURS OR SO...WHICH IS CONSISTENT WITH ALL OF THE NHC MODEL GUIDANCE. AFTER THAT...HOWEVER...THE GUIDANCE REMAINS DIVERGENT ON WHETHER OTTO WILL CONTINUE TO MOVE TO THE NORTHEAST OR SLOW DOWN AND TURN SOUTHEASTWARD TOWARD THE AZORES ISLANDS. THERE IS MUCH LESS SPREAD IN THE MODEL SOLUTIONS FOR THIS RUN COMPARED TO THE PREVIOUS ADVISORY...SO THE FORECAST TRACK HAS BEEN SHIFTED SLIGHTLY NORTHWARD WITH A NOTED DECREASE IN FORWARD SPEED. OVERALL...THE OFFICIAL FORECAST IS SIMILAR TO THE CONSENSUS MODEL...TVCN...THROUGH 72 HOURS...AND THEN A LITTLE SOUTH OF THAT MODEL AT 96 AND 120 HOURS. CONVENTIONAL INFRARED SATELLITE POSITION ESTIMATES INDICATE THAT THE UPPER-LEVEL CIRCULATION IS OUTRUNNING THE LOW-LEVEL CENTER NOTED IN MICROWAVE DATA BY MORE THAN 60 NMI...SO GRADUAL WEAKENING IS FORECAST SINCE OTTO WILL BE MOVING OVER PROGRESSIVELY COOLER SSTS AND EXPERIENCING INCREASING SOUTHWESTERLY VERTICAL SHEAR. TIMING POSSIBLE DECOUPLING OF THE LOWER- AND UPPER-LEVEL CIRCULATIONS IS TRICKY. HOWEVER...SINCE OTTO WILL BE MOVING OVER SUB-23C SSTS...BE UNDERNEATH VERTICAL SHEAR CONDITIONS EXCEEDING 40 KT...AND POSSIBLY MERGE WITH A FRONTAL ZONE BY 48 HOURS...OTTO IS EXPECTED TO BEGIN EXTRATROPICAL TRANSITION BETWEEN 36-48 HOURS. THE INTENSITY FORECAST IS SIMILAR TO BUT SLIGHTLY LOWER THAN A BLEND OF THE NHC INTENSITY GUIDANCE...DUE IN PART TO THE TILTED VORTEX STRUCTURE. FORECAST POSITIONS AND MAX WINDS INITIAL 09/0300Z 27.8N 60.8W 75 KT 12HR VT 09/1200Z 29.7N 57.4W 70 KT 24HR VT 10/0000Z 32.6N 51.7W 70 KT 36HR VT 10/1200Z 36.1N 44.4W 65 KT 48HR VT 11/0000Z 40.0N 36.4W 60 KT...POST-TROP/EXTRATROP 72HR VT 12/0000Z 43.0N 28.0W 50 KT...POST-TROP/EXTRATROP 96HR VT 13/0000Z 43.0N 23.5W 40 KT...POST-TROP/EXTRATROP 120HR VT 14/0000Z 40.0N 20.0W 40 KT...POST-TROP/EXTRATROP $$ FORECASTER STEWART