MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 09W (NINE) WARNING NR 06// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 09W (NINE), LOCATED APPROXIMATELY 63 NM EAST-SOUTHEAST OF ANDERSEN AFB, GUAM HAS TRACKED WEST-NORTHWESTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. TD 09W HAS BEEN DOWNGRADED FROM TROPICAL STORM STATUS DUE TO RECENT OBSERVATIONS AND THE LACK OF SUPPORTING DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD. THE OBSERVATIONS AT GUAM INDICATE THE SYSTEM REMAINS A WEAKLY DEFINED LOW LEVEL CIRCULATION CENTER (LLCC) TO THE EAST OF GUAM. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS DEEP CONVECTION ASSOCIATED WITH THE SYSTEM HAS BEEN SHEARED TO THE NORTHWEST UNDER A MARGINAL UPPER LEVEL ENVIRONMENT. RECENT FRESH CONVECTION HAS STARTED TO BUILD OVER THE LOOSELY ORGANIZED LLCC. A SERIES OF SPURIOUS SMALLER CIRCULATIONS TO THE SOUTH OF GUAM HAVE BEEN OBSERVED IN THE GUAM RADAR IMAGERY. ATMOSPHERIC SOUNDINGS FROM GUAM AT 1200Z INDICATED STRONGER 25 TO 30 KNOTS OF EASTERLY FLOW IN THE MID TO UPPER LEVELS, CREATING MODERATE LEVELS OF VERTICAL WIND SHEAR (VWS) OVER THE LLCC. TD 09W CONTINUES TO TRACK ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR), ANCHORED BETWEEN IWO TO AND GUAM. 3. FORECAST REASONING. A. THE CURRENT FORECAST SHIFTS THE INTENSITY FORECAST REASONING, DECREASING THE INITIAL INTENSITY TO 30 KNOTS, BASED ON THE AVAILABLE ENVIRONMENTAL OBSERVATIONS. THE FORECASTED INTENSITY HAS BEEN DECREASED AT ALL TAUS IN RESPONSE TO THE RE-EVALUATION OF THE UPPER LEVEL ENVIRONMENT. B. TD 09W IS FORECAST TO TRACK WESTWARD FOR THE NEXT 72 HOURS ALONG THE SOUTHERN PERIPHERY OF THE STR. BASED ON THE SHIFT IN UPPER LEVEL SUPPORT, INCREASED VWS THAN PREVIOUSLY FORECASTED, THE OVERALL ENVIRONMENT WILL STRUGGLE TO ALIGN FOR THE NEXT 36 TO 48 HOURS, LEADING TO A SLOW DEVELOPMENT POTENTIAL THROUGH TAU 48. SEA SURFACE TEMPERATURES (SST) REMAIN FAVORABLE ALONG THE FORECASTED TRACK, BUT THE OUTFLOW WILL REMAIN THE LIMITING FACTOR IN THE NEAR TERM. BY TAU 72, VWS IS EXPECTED TO DECREASE ALLOWING FOR INCREASED INTENSIFI- CATION. C. AFTER TAU 72, A MID-LATITUDE TROUGH IS FORECAST TO DIG OVER EASTERN CHINA, CAUSING A SHIFT IN THE STR, LEADING TO A MORE WEST- NORTHWEST TRACK TOWARDS THE NORTHERN PART OF LUZON. ADDITIONALLY, THE VERY FAVORABLE SST VALUES PRIOR TO THE APPROACH WILL LEAD TO A MAXIMUM INTENSITY AROUND TAU 84, POSSIBLY NEAR 100 KNOTS BUT IS NOT REFLECTED IN THE FORECAST AS THE TAU 120 INTENSITY OF 95 KNOTS ENCOMPASSES A SLIGHT IMPACT TO THE LOW LEVEL STRUCTURE AS THE INFLOW WITHIN THE NORTHWEST QUADRANT IS IMPACTED BY CROSSING OVER LUZON. THE AVAILABLE MODEL GUIDANCE IS IN GOOD AGREEMENT; HOWEVER, DUE TO THE INITIAL POSITIONING AND TRACK SPEED UNCERTAINTY, THE OVERALL CONFIDENCE IN THE FORECAST REMAINS LOW.// NNNN NNNN