MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (SOUDELOR) WARNING NR 08// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 13W (SOUDELOR), LOCATED APPROXIMATELY 441 NM EAST-SOUTHEAST OF SAIPAN, HAS TRACKED WESTWARD AT 14 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS FRAGMENTED CURVED BANDING WRAPPING INTO A COMPACT EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC). A 312354Z ASCAT PASS INDICATES 35 KNOTS ALONG THE NOTHERN SEMICIRCLE OF A CLOSED CIRCULATION, AND SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 35 KNOTS BASED ON T2.5 DVORAK CURRENT INTENSITY ESTIMATES FROM ALL AGENCIES, AS WELL AS THE AFOREMENTIONED ASCAT DATA. A TIME SERIES OF RECENT DATA SUGGESTS THE LLCC IS SLOWLY BECOMING MORE ORGANIZED. ANIMATED VAPOR LOOP SHOWS THE TUTT CELL LOCATED NORTH OF THE CYCLONE IS BEGINNING TO PULL POLEWARD AND STARTING TO PROVIDE AN OUTFLOW MECHANISM. VERTICAL WIND SHEAR IS LIGHT, AT 5-10 KNOTS. ADDITIONALLY, SSTS IN THE AREA ARE VERY CONDUCIVE FOR DEVELOPMENT AT 30-31 DEGREES CELSIUS. TS SOUDELOR IS CURRENTLY TRACKING ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED SUB-TROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 13W IS FORECAST TO TRACK GENERALLY WEST-NORTHWESTWARD THROUGHOUT THE FORECAST PERIOD UNDER THE STEERING INFLUENCE OF THE WELL-ESTABLISHED STR. DYNAMICAL MODEL GUIDANCE IS IN GOOD AGREEMENT WITH THIS MOTION, WITH NAVY MODELS ON THE POLEWARD SIDE OF THE ENVELOPE. MODEL SPREAD IS APPROXIMATELY 150 NM AS THE CYCLONE PASSES OVER THE MARIANAS ISLAND CHAIN. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO REMAIN FAVORABLE OVER THE NEXT 72 HOURS, PARTICULARLY AS POLEWARD OUTFLOW INTO THE TUTT BECOMES MORE ESTABLISHED. AS THE LLCC BECOMES BETTER ORGANIZED, THESE CONDITIONS WILL MAKE RAPID INTENSIFICATION LIKELY AFTER TAU 12. AN INTENSIFICATION TREND WILL CONTINUE THROUGH TAU 72. BASED ON GOOD MODEL AGREEMENT THROUGH TAU 72, THERE IS HIGH CONFIDENCE IN THIS PORTION OF THE FORECAST. C. IN THE EXTENDED FORECAST, THE STR IS EXPECTED TO REMAIN IN PLACE LEADING TO CONTINUED WEST-NORTHWESTWARD MOTION THROUGHOUT THE PERIOD. INTENSIFICATION WILL BE TEMPERED BY A DECREASE IN SSTS AND OCEAN HEAT CONTENT AS WELL AS A SLIGHT INCREASE IN VWS. ALTHOUGH MODEL TRACK SOLUTIONS FAN OUT, NONE OF THE GUIDANCE HAS ANY INDICATION OF A RECURVATURE SCENARIO. THE JTWC TRACK IS POSITIONED VERY CLOSE TO THE PREVIOUS FORECAST AND JUST SOUTH OF THE MULTI- MODEL CONSENSUS IN FAVOR OF THE GFS, HWRF, AND EUROPEAN MODELS BASED ON THEIR INITIALIZATION OF THE STR. DUE TO THE INCREASING MODEL SPREAD BEYOND TAU 72, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST.// NNNN NNNN