WTPQ32 RJTD 281200 RSMC TROPICAL CYCLONE PROGNOSTIC REASONING REASONING NO.19 FOR TY 2509 KROSA (2509) 1.GENERAL COMMENTS TY KROSA IS LOCATED AT 27.2N, 144.1E. INFORMATION ON THE CURRENT POSITION IS BASED ON ANIMATED MSI AND SURFACE OBSERVATIONS. POSITIONAL ACCURACY IS GOOD. CENTRAL PRESSURE IS 970HPA AND MAXIMUM SUSTAINED WINDS NEAR THE CENTER ARE 65KNOTS. THE SYSTEM IS IN AN UNFAVORABLE ENVIRONMENT FOR DEVELOPMENT UNDER THE INFLUENCE OF WEAK VWS, LOW TCHP AND DRY AIR. 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 NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF A MID-LEVEL SUB-TROPICAL HIGH. ANIMATED MSI SHOWS THE SYSTEM HAS A BAND WITH A CURVATURE SUGGESTING THE CSC. ANIMATED MSI SHOWS GOOD CLOUD CHARACTERISTICS OF ANTICYCLONIC OUTFLOW. WATER VAPOR IMAGERY SHOWS DRY AIR AROUND THE SYSTEM. METOP-B/MHS 85 GHZ MICROWAVE IMAGERY SHOWS THE SYSTEM HAS A BAND WITH CURVATURE INDICATING THE CSC. 3.TRACK FORECAST THE SYSTEM WILL GRADUALLY DECELERATE AND MOVE NORTHWESTWARD ALONG THE PERIPHERY OF A MID-LEVEL SUB-TROPICAL HIGH UNTIL FT24. THE SYSTEM WILL THEN REMAIN ALMOST STATIONARY BETWEEN TWO MID-LEVEL SUB-TROPICAL HIGHS UNTIL FT72. THE SYSTEM WILL THEN MOVE SLOWLY NORTHWARD BETWEEN TWO MID-LEVEL SUB-TROPICAL HIGHS UNTIL FT120. THE TRACK FORECAST IS BASED ON GSM PREDICTIONS, AND REFERENCE TO OTHER NWP MODELS. TRACK FORECAST CONFIDENCE IS FAIR UNTIL FT48 BUT LOW THEREAFTER DUE TO SIGNIFICANT DIFFERENCES AMONG NWP MODEL OUTPUTS. 4.INTENSITY FORECAST THE SYSTEM WILL GRADUALLY WEAKEN UNTIL FT48 DUE TO THE INFLUENCE OF INTERACTION WITH WEAK VWS, LOW TCHP AND DRY AIR. THE SYSTEM WILL THEN MAINTAIN ITS INTENSITY UNTIL FT120 DUE TO THE INFLUENCE OF INTERACTION WITH WEAK VWS AND LOW TCHP. THE INTENSITY FORECAST IS BASED ON A CONSENSUS OF GUIDANCE DATA INCLUDING GSM. =