000 WTNT42 KNHC 080241 TCDAT2 TROPICAL STORM OTTO DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 1100 PM AST THU OCT 07 2010 A LITTLE BIT OF WESTERLY SHEAR IS AFFECTING OTTO...AND THE LOW-LEVEL CENTER IS EMBEDDED BENEATH THE WESTERN SIDE OF A NEARLY CIRCULAR AREA OF DEEP CONVECTION. SATELLITE INTENSITY ESTIMATES ARE T3.5/55 KT AND T3.0/45 KT FROM TAFB AND SAB...RESPECTIVELY...AND THE INITIAL INTENSITY WILL BE MAINTAINED AT 50 KT. STRENGTHENING IS STILL POSSIBLE DURING THE NEXT 48 HOURS SINCE THE VERTICAL SHEAR IS EXPECTED TO BE RELATIVELY LIGHT. THE ONE BIG CHANGE IN THE INTENSITY GUIDANCE IS THAT MOST OF THE MODELS NOW SHOW A PEAK IN INTENSITY OCCURRING AROUND 48 HOURS...WHICH IS ABOUT 12 HOURS LATER THAN INDICATED IN THE PREVIOUS ADVISORY. THE NEW FORECAST... THEREFORE...DOES NOT SHOW WEAKENING COMMENCING UNTIL AFTER 48 HOURS. THIS SOLUTION IS CLOSE TO THE STATISTICAL AND GLOBAL GUIDANCE BUT TENDS TO DISREGARD THE HWRF AND GFDL SINCE THOSE MODELS APPEAR TO DISSIPATE OTTO TOO SOON. THE INITIAL MOTION IS 070/8. THE CYCLONE IS BEING PICKED UP BY A LARGE MID/UPPER-LEVEL TROUGH OVER THE WESTERN ATLANTIC AND IS EXPECTED TO BECOME EMBEDDED WITHIN FAST MID-LATITUDE WESTERLIES OVER THE NEXT 24-48 HOURS. BY THE END OF THE FORECAST...MODEL GUIDANCE SUGGESTS THAT THE FLOW WILL SPLIT WITH THE POST-TROPICAL CYCLONE TAKING THE SOUTHERN ROUTE AND SLOWING DOWN AS IT NEARS THE AZORES. THE OFFICIAL FORECAST IS NOT MUCH DIFFERENT FROM THE PREVIOUS ONE AND GENERALLY LIES BETWEEN THE FASTER ECMWF AND SLOWER GFS. THE FSU PHASE SPACE DIAGRAMS SHOW THAT OTTO SHOULD BEGIN EXTRATROPICAL TRANSITION IN THE NEXT 24-36 HOURS...BUT THEY ALSO SUGGEST THAT IT WILL NOT BECOME A DEEP COLD-CORE SYSTEM WITHIN THE 5-DAY FORECAST PERIOD. AS SUCH...CONFIDENCE IS NOT HIGH THAT OTTO WILL BECOME COMPLETELY EXTRATROPICAL BY 72 HOURS. FORECAST POSITIONS AND MAX WINDS INITIAL 08/0300Z 24.1N 66.6W 50 KT 12HR VT 08/1200Z 24.9N 65.1W 55 KT 24HR VT 09/0000Z 26.7N 62.0W 55 KT 36HR VT 09/1200Z 29.0N 57.6W 60 KT 48HR VT 10/0000Z 31.4N 52.1W 60 KT 72HR VT 11/0000Z 36.5N 38.5W 50 KT...POST-TROP/EXTRATROP 96HR VT 12/0000Z 39.0N 27.0W 45 KT...POST-TROP/EXTRATROP 120HR VT 13/0000Z 36.5N 23.0W 35 KT...POST-TROP/EXTRATROP $$ FORECASTER BERG