WTPQ32 RJTD 030000 RSMC TROPICAL CYCLONE PROGNOSTIC REASONING REASONING NO.41 FOR TS 2509 KROSA (2509) 1.GENERAL COMMENTS TS KROSA IS LOCATED AT 39.9N, 150.9E. INFORMATION ON THE CURRENT POSITION IS BASED ON ANIMATED MSI AND SURFACE OBSERVATIONS. POSITIONAL ACCURACY IS FAIR. CENTRAL PRESSURE IS 980HPA AND MAXIMUM SUSTAINED WINDS NEAR THE CENTER ARE 45KNOTS. THE SYSTEM IS IN AN UNFAVORABLE ENVIRONMENT FOR DEVELOPMENT UNDER THE INFLUENCE OF LOWER SSTS AND LOW TCHP. THIS HAS CAUSED THE SYSTEM TO WEAKEN OVER THE LAST SIX HOURS. INFORMATION ON THE CURRENT INTENSITY IS BASED ON DVORAK INTENSITY ANALYSES AND SURFACE OBSERVATIONS. 2.SYNOPTIC SITUATION THE SYSTEM IS MOVING EAST-NORTHEASTWARD ALONG THE NORTHWESTERN PERIPHERY OF A MID-LEVEL SUB-TROPICAL HIGH. ANIMATED MSI SHOWS THE SEPARATION OF ACTIVE CONVECTIVE CLOUD CLUSTERS FROM THE CSC. ANIMATED MSI SHOWS GOOD CLOUD CHARACTERISTICS OF ANTICYCLONIC OUTFLOW. WATER VAPOR IMAGERY SHOWS DRY AIR AROUND THE SYSTEM. GPM/GMI 89 GHZ MICROWAVE IMAGERY SHOWS THE SYSTEM HAS A BAND WITH CURVATURE INDICATING THE CSC. 3.TRACK FORECAST THE SYSTEM WILL MOVE EAST-NORTHEASTWARD ALONG THE PERIPHERY OF A MID-LEVEL SUB-TROPICAL HIGH UNTIL FT36. THE SYSTEM WILL THEN MOVE EASTWARD UNDER THE INFLUENCE OF MID-LATITUDE PREVAILING WESTERLIES UNTIL FT48. THE TRACK FORECAST IS BASED ON GSM PREDICTIONS, AND REFERENCE TO OTHER NWP MODELS. TRACK FORECAST CONFIDENCE IS FAIR BECAUSE ALL NWP MODELS ARE IN CLOSE AGREEMENT. 4.INTENSITY FORECAST THE SYSTEM WILL WEAKEN UNTIL FT48 DUE TO THE INFLUENCE OF INTERACTION WITH LOW SSTS, LOW TCHP AND INCREASED VWS. THE SYSTEM WILL TRANSFORM INTO AN EXTRATROPICAL CYCLONE BY FT48. THE INTENSITY FORECAST IS BASED ON A CONSENSUS OF GUIDANCE DATA INCLUDING GSM. =