MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 16W (SIXTEEN) WARNING NR 04// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 16W (SIXTEEN), LOCATED APPROXIMATELY 175 NM WEST-NORTHWEST OF ANDERSEN AFB, GUAM HAS TRACKED NORTHWESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS INCREASED CONVECTION BUILDING JUST SOUTH OF A CONSOLIDATING LOW LEVEL CIRCULATION CENTER (LLCC) DUE TO NORTHERLY VERTICAL WIND SHEAR (VWS). A 091301Z GPM 89GHZ MICROWAVE IMAGE SHOWS CONVECTIVE BANDING WRAPPING FROM THE SOUTH INTO A DEFINED LLCC WHICH SUPPORTS THE CURRENT POSITION WITH GOOD CONFIDENCE. THE CURRENT INTENSITY HAS BEEN HELD AT 30 KNOTS BASED ON AN ASSESSMENT OF DVORAK INTENSITY ESTIMATES RANGING FROM 25 TO 30 KNOTS AND IS SUPPORTED BY A PARTIAL 091121Z ASCAT PASS SHOWING THE EASTERN SEMI-CIRCLE WITH 25 KNOT WINDS TO THE SOUTHEAST; HOWEVER, THE BULK OF DEEP CONVECTION IS ON THE SOUTHWESTERN SIDE. ENVIRONMENTAL ANALYSIS INDICATES A MARGINALLY-FAVORABLE ENVIRONMENT WITH LOW (5-10 KNOT) VWS, WEAK RADIAL OUTFLOW, AND WARM (29 CELSIUS) SEA SURFACE TEMPERATURES (SSTS). THE SYSTEM HAS STARTED TO TRACK NORTHWESTWARD UNDER THE INFLUENCE OF A BUILDING LOW LEVEL SUB- TROPICAL RIDGE (STR) TO THE NORTHEAST. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD 16W WILL CONTINUE TRACKING NORTHWESTWARD UNDER THE BUILDING STR THROUGHOUT THE FORECAST PERIOD. THE FAVORABLE ENVIRONMENTAL CONDITIONS WILL ALLOW FOR A STEADY INTENSIFICATION OVER THE NEXT 36 HOURS. AFTERWARDS, INCREASED VWS DUE TO NORTHEASTERLY FLOW ASSOCIATED WITH THE EASTERN EDGE OF AN UPPER LEVEL STR POSITIONED OVER CHINA WILL TEMPER THE RATE OF INTENSIFICATION. BEYOND TAU 48, THIS RIDGE WILL WEAKEN, DECREASING THE VWS ONCE AGAIN. DYNAMIC MODEL GUIDANCE REMAINS IN FAIRLY GOOD AGREEMENT DURING THIS PORTION OF THE FORECAST, WITH ONLY SMALL DIFFERENCES IN THE FORWARD SPEED OF THE CYCLONE. C. IN THE EXTENDED FORECAST, TD 16W WILL REMAIN UNDER THE STEERING INFLUENCE OF THE STR AND BY TAU 120, WILL REACH THE SOUTHWESTERN PERIPHERY OF THE STR AND TURN POLEWARD TOWARDS A BREAK IN THE STEERING RIDGE. BEYOND TAU 72, IMPROVED VWS AND OUTFLOW ASSOCIATED WITH A MID-LATITUDE TROUGH APPROACHING FROM THE WEST, COMBINED WITH INCREASED SSTS AND HIGH OCEAN HEAT CONTENT, WILL SUPPORT AN INCREASED INTENSIFICATION RATE WITH THE POSSIBILITY OF RAPID INTENSIFICATION. DYNAMICAL MODEL GUIDANCE IS IN FAIR AGREEMENT IN THE EXTENDED PORTION OF THE FORECAST WITH AN 125NM SPREAD AT TAU 120. HWRF CONTINUES TO BE THE ONLY OUTLIER OF THE GROUP WITH A TRACK INTO TAIWAN. THE JTWC TRACK FORECAST IS LAID NEAR THE MULTI-MODEL CONSENSUS (CONW) THROUGH TAU 72 AND THEN RIGHT OF CONW FAVORING ALL OF THE GLOBAL MODELS WHICH SHOW A RECURVE SCENARIO. DUE TO IMPROVING MODEL TRACKERS WITH A SMALL SPREAD IN THE EXTENDED FORECAST, THERE IS HIGH CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN NNNN