TS 24W(KOMPASU) is a very large system over the South China Sea, 12/09utc update

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL STORM (TS) 24W IS FORECAST TO TRACK WESTWARD THROUGH THE FORECAST PERIOD UNDER THE STEERING INFLUENCE OF THE SUBTROPICAL RIDGE(STR). TS 24W WILL STRENGTHEN TO A PEAK OF 60 KNOTS BY 12H THEN GRADUALLY WEAKEN AS VWS INCREASES. AS THE SYSTEM TRACKS OVER HAINAN AFTER 24, IT WILL WEAKEN SIGNIFICANTLY WITH MORE RAPID WEAKENING EXPECTED AS THE SYSTEM MAKES LANDFALL OVER VIETNAM AFTER 48H. DISSIPAT

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A VERY LARGE (GREATER THAN 10 DEGREE DIAMETER) SYSTEM WITH EXTENSIVE DEEP CONVECTIVE BANDING WRAPPING INTO A LARGE RAGGED CENTER (APPROXIMATELY 200KM DIAMETER). DUE TO THE VERY LARGE NATURE OF THIS SYSTEM, GALE-FORCE WINDS EXTEND OUT ALONG THE PERIPHERY NEAR TAIWAN AND SOUTHWEST OF LUZON. A 120600Z AMSR2 89GHZ MICROWAVE IMAGE INDICATES FRAGMENTED CONVECTIVE BANDS WRAPPING AROUND THE WESTERN SEMICIRCLE OF THE LARGE LOW-LEVEL CIRCULATION CENTER, WHICH SUPPORTS THE INITIAL POSITION WITH MEDIUM CONFIDENCE. THE INITIAL INTENSITY OF 55 KNOTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK ESTIMATES. UPPER-LEVEL ANALYSIS INDICATES A MARGINALLY FAVORABLE ENVIRONMENT WITH LOW TO MODERATE VERTICAL WIND SHEAR (VWS) OFFSET BY STRONG EQUATORWARD OUTFLOW.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT THROUGH 36H WITH A 90KM SPREAD IN SOLUTIONS AT 36H. THE MODELS DIVERGE AFTER 36H BUT REMAIN IN GOOD AGREEMENT LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK.

12/09UTC.