MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (FOUR) WARNING NR 06// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 04W (FOUR), LOCATED APPROXIMATELY 510 NM EAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION IS BASED ON RECENT MICROWAVE SATELLITE IMAGERY INCLUDING A 292214Z SSMIS AND A 292127Z CORIOLIS IMAGE. THE INTENSITY OF 35 KNOTS IS CONSISTENT WITH DVORAK CURRENT INTENSITY ESTIMATES OF T2.5 FROM PGTW AND KNES. TD 04W IS TRACKING NORTHWESTWARD ALONG THE PERIPHERY OF A SUBTROPICAL STEERING RIDGE SITUATED TO THE NORTH AND EAST. THE LOW LEVEL CIRCULATION CENTER (LLCC) HAS BECOME LESS DEFINED IN MICROWAVE AND VISIBLE SATELLITE IMAGERY. ALTHOUGH A PATCH OF DEEP CONVECTION PERSISTS OVER THE SOUTHWESTERN PORTION OF THE CIRCULATION, NEARLY ALL CONVECTION HAS DIMINISHED NEAR THE CENTER. THIS STRUCTURAL CHANGE SUGGESTS THAT VERTICAL WIND SHEARS (VWS) IS EFFECTING THE SYSTEM MORE THAN PREVIOUSLY ANTICIPATED. DIFFLUENCE ALOFT REMAINS STRONG, AND SEA SURFACE TEMPERATURES ARE VERY SUPPORTIVE AT ABOUT 30 DEGREES CELSIUS. 3. FORECAST REASONING. A. FORECAST INTENSITIES HAVE BEEN REDUCED FROM THE PREVIOUS WARNING BASED ON ONGOING AND ANTICIPATED DISRUPTION TO THE STORM STRUCTURE BY PERSISTENT VWS. OTHERWISE, THERE IS NO MAJOR CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS WARNING. B. TS 04W IS EXPECTED TO TRACK GENERALLY NORTHWESTWARD FOLLOWING THE STEERING FLOW ASSOCIATED WITH THE SUBTROPICAL STEERING TO THE NORTH AND EAST FOR THE NEXT 72 HOURS. VWS WILL DECREASE SLIGHTLY THROUGH TAU 48, WHICH MAY ALLOW THE SYSTEM TO INTENSIFY SLOWLY WITH THE SUPPORT OF VERY WARM SEA SURFACE TEMPERATURES AND STRONG DIFFLUENCE ALOFT. HOWEVER, RECENT DISORGANIZATION OF THE STORM STRUCTURE MAY HAMPER FURTHER INTENSIFICATION AND LEAVE THE STORM VULNERABLE TO DISSIPATING EARLIER THAN THE CURRENT FORECAST INDICATES. THIS EARLY DISSIPATION IS CONSIDERED A PLAUSIBLE ALTERNATE SCENARIO TO THE CURRENT FORECAST. NUMERICAL MODELS ARE IN FAIR AGREEMENT REGARDING THE GENERAL NORTHWESTWARD TRACK OF TS 04W THROUGH TAU 72, ALTHOUGH THE LATEST NAVGEM RUN PREDICTS RECURVATURE OF A STRONGER THAN EXPECTED SYSTEM TO THE EAST OF TAIWAN AND SEVERAL MODELS DISSIPATE THE SYSTEM PRIOR TO LANDFALL. THE CURRENT FORECAST TRACK IS CONSERVATIVELY CONSISTENT WITH THE PREVIOUS FORECAST TRACK AND IS SUPPORTED BY SEVERAL MODEL SOLUTIONS. GIVEN NOTED MODEL DIVERGENCE, CONFIDENCE IN THE FORECAST TRACK IS LOW. C. IN THE EXTENDED RANGE, TS 04W IS EXPECTED TO TRACK INLAND AND DISSIPATE OVER SOUTHEASTERN CHINA, IF IT SURVIVES TO THAT POINT. NUMERICAL GUIDANCE DIVERGES SIGNIFICANTLY, ALTHOUGH ALL MODELS SUPPORT DISSIPATION. CONFIDENCE IN THE EXTENDED FORECAST PORTION OF THE JTWC TRACK FORECAST IS ALSO LOW.// NNNN NNNN