WTPQ31 RJTD 191200 RSMC TROPICAL CYCLONE PROGNOSTIC REASONING REASONING NO.11 FOR TS 2518 RAGASA (2518) 1.GENERAL COMMENTS TS RAGASA IS LOCATED AT 16.5N, 130.0E. INFORMATION ON THE CURRENT POSITION IS BASED ON ANIMATED MSI AND SURFACE OBSERVATIONS. POSITIONAL ACCURACY IS FAIR. CENTRAL PRESSURE IS 994HPA AND MAXIMUM SUSTAINED WINDS NEAR THE CENTER ARE 45KNOTS. THE SYSTEM IS IN A FAVORABLE ENVIRONMENT FOR DEVELOPMENT UNDER THE INFLUENCE OF HIGH SSTS, HIGH TCHP AND GOOD UPPER-LEVEL OUTFLOW. THIS HAS CAUSED THE SYSTEM TO DEVELOP 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 WESTWARD ALONG THE SOUTHERN PERIPHERY OF A MID-LEVEL SUB-TROPICAL HIGH. ANIMATED MSI SHOWS CB CLUSTERS GATHERING AROUND THE CSC AND FORMING A CURVED BAND. 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 SLOWLY NORTHWESTWARD DUE TO INTERACTION WITH AN UPPER VORTEX UNTIL FT24. THE SYSTEM WILL THEN MOVE WESTWARD ALONG THE PERIPHERY OF A MID-LEVEL SUB-TROPICAL HIGH UNTIL FT120. 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 DEVELOP UNTIL FT72 DUE TO THE INFLUENCE OF INTERACTION WITH HIGH SSTS, HIGH TCHP, WEAK VWS AND GOOD UPPER-LEVEL OUTFLOW. THE SYSTEM WILL THEN MAINTAIN ITS INTENSITY UNTIL FT96 DUE TO THE INFLUENCE OF INTERACTION WITH HIGH SSTS AND REDUCED TCHP. THE SYSTEM WILL THEN WEAKEN UNTIL FT120 DUE TO THE INFLUENCE OF LAND. THE INTENSITY FORECAST IS BASED ON A CONSENSUS OF GUIDANCE DATA INCLUDING GSM. =