MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 16W (SIXTEEN) WARNING NR 01// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 16W (SIXTEEN), LOCATED APPROXIMATELY 327 NM EAST-SOUTHEAST OF ANDERSEN AFB, GUAM HAS TRACKED WEST- NORTHWESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS BETTER DEFINED CLOUD LINES WRAPPING INTO A CONSOLIDATING LOW LEVEL CIRCULATION CENTER (LLCC) OBSCURED BY DEEPENING CENTRAL CONVECTION. A 132119Z SSMIS 91GHZ MICROWAVE IMAGE SHOWS AN ELONGATED LLCC WITH CURVED CONVECTION ALONG THE PERIPHERIES OF THE BROADER CIRCULATION. THE INITIAL POSITION IS BASED ON THE LLCC IN THE ABOVE IMAGERY WITH FAIR CONFIDENCE. THE CURRENT INTENSITY IS ASSESSED AT 25 KNOTS BASED ON DVORAK INTENSITY ESTIMATES OF 25 KNOTS FROM ALL AGENCIES AND SUPPORTED BY THE IMPROVED DEFINITION IN THE LOW LEVEL CLOUD LINES. ENVIRONMENTAL ANALYSIS INDICATES A MARGINALLY FAVORABLE ENVIRONMENT WITH LOW TO MODERATE VERTICAL WIND SHEAR (VWS) AND EXCELLENT DIVERGENT OUTFLOW WITH AN EQUATORWARD BIAS. HOWEVER, A TUTT CELL, APPARENT IN WATER VAPOR IMAGERY, IS LOCATED TO THE NORTHEAST OF THE SYSTEM AND DISRUPTING CONVECTIVE ORGANIZATION. SEA SURFACE TEMPERATURES (SSTS) ABOVE 28 CELSIUS ARE CONDUCIVE FOR DEVELOPMENT. TD 16W IS TRACKING SLOWLY WESTWARD ALONG THE SOUTHERN PERIPHERY OF A SUB-TROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST PHILOSOPHY. B. TD 16W IS EXPECTED TO CONTINUE TO SLOW DOWN AS A BUILDING NEAR- EQUATORIAL RIDGE (NER) TO THE SOUTHEAST COMPLICATES THE STEERING ENVIRONMENT AND DRIVES THE SYSTEM NORTH. AS THE SYSTEM GAINS LATITUDE, TOWARDS THE AFOREMENTIONED TUTT CELL, EXPECT MODEST INTENSIFICATION DUE TO THE INCREASED SUBSIDENCE ALOFT. BEYOND TAU 36, THE STR TO THE NORTH WILL ASSUME STEERING ONCE AGAIN, TURNING THE CYCLONE TO THE WEST. CONCURRENTLY, THE TUTT CELL WILL MOVE DOWNSTREAM FROM TD 16W, PROVIDING A POLEWARD OUTFLOW CHANNEL WHICH WILL INCREASE THE RATE OF INTENSIFICATION. AFTER TAU 48, ENVIRONMENTAL CONDITIONS WILL BE OPTIMAL FOR RAPID INTENSIFICATION (RI) DUE TO STRONG DUAL CHANNEL OUTFLOW AND LOW VWS WITH HIGH SSTS AND OCEAN HEAT CONTENT. C. IN THE EXTENDED TAUS, TD 16W WILL ACCELERATE WEST- NORTHWESTWARD UNDER THE DOMINANT STR. ENVIRONMENTAL CONDITIONS WILL REMAIN OPTIMAL TO CONTINUE RI THROUGH TAU 96. BEYOND TAU 96, AN UPPER LEVEL RIDGE NORTHWEST OF THE CYCLONE WILL ONCE AGAIN REDUCE THE POLEWARD OUTFLOW AND INCREASE THE VWS. THESE CONDITIONS WILL REDUCE THE RATE OF INTENSIFICATION. LIMITED MODEL GUIDANCE IS IN FAIR AGREEMENT WITH THE OVERALL TRACK PHILOSOPHY, HOWEVER, THERE IS A LARGE SPREAD IN THE INITIAL 24 HOURS. NAVGEM, COAMPS-TC, AND GFDN TRACK THE SYSTEM NORTHEASTWARD UNDER A STRONGER NER PRIOR TO THE STR ASSUMING STEERING. GFS AND HWRF INITIALLY TRACK THE SYSTEM NORTH- NORTHWESTWARD AND THEN TURN IT TO THE WEST. THIS DIFFERENCE CREATES A LARGE TIMING DISCREPANCY IN THE OVERALL GUIDANCE. DUE TO THIS TIMING AND TRACK SPREAD, THE INITIAL JTWC TRACK IS LAID JUST INSIDE OF THE MULTI-MODEL CONSENSUS, CLOSER TO THE GFS SOLUTION, WITH LOW CONFIDENCE.// NNNN NNNN