WDPN31 PGTW 070300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (BOPHA) WARNING NR 46// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 26W (BOPHA) LOCATED APPROXIMATELY 320 NM WEST OF MANILA, PHILIPPINES HAS TRACKED NORTH-NORTHWESTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE SHOWS A RECENT INCREASE IN CENTRAL CONVECTION WITH THE DEVELOPMENT OF A WEAK BANDING FEATURE OVER THE PAST FEW HOURS BUILDING FROM THE LOW LEVEL CIRCULATION CENTER (LLCC). THE TOTAL PRECIPITABLE WATER IMAGERY INDICATES THE RIBBON OF DRY AIR HAS FURTHER PENETRATED THE EASTERN PERIPHERY OF THE LLCC, WITH A NOTABLE SHRINKING OF LLCC SIGNATURE WITHIN THE LOOP. THE CURRENT INTENSITY HAS BEEN MAINTAINED AT 50 KNOTS BASED ON DVORAK ESTIMATES REMAINING CONSISTENT FROM THE PREVIOUS FORECAST CYCLE. UPPER LEVEL ANALYSIS INDICATES THE LLCC IS LOCATED UNDER THE SUBTROPICAL RIDGE (STR) AXIS, WHICH IS PROVIDING FAVORABLE DIVERGENCE ALOFT AND LOW TO MODERATE LEVELS (10 TO 20 KNOTS) OF VERTICAL WIND SHEAR (VWS). TS 26W HAS BEEN TRACKING STEADILY ALONG THE SOUTHWESTERN PERIPHERY OF A STR TOWARDS A COL REGION BETWEEN TWO LOBES OF THE DEEP LAYERED STR. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 26W IS FORECAST TO SLOW DOWN AS IT TRACKS TOWARDS THE COL REGION BETWEEN THE TWO LOBES OF THE STR. DRY AIR WILL BEGIN TO WRAP AROUND THE PERIPHERY OF THE SYSTEM, LEADING TO FURTHER WEAKENING OF THE LOW LEVEL STRUCTURE WHILE CONTINUING TO ACT AS A BUFFER ALONG THE NORTHWESTERN QUADRANT OF THE SYSTEM. AS TS 26W WEAKENS, THE STEERING MECHANISM WILL SHIFT FROM THE DEEP LAYER FLOW AROUND THE STR TO A SURFACE STEERING INFLUENCE ASSOCIATED WITH THE NORTHEAST MONSOON FLOW BETWEEN TAU 36 AND 48. C. AFTER TAU 72, TS 26W IS EXPECTED TO REMAIN ON A WEAKENING TREND WITH DISSIPATION BEGINNING AROUND TAU 72 AND FULL DISSIPATION OF THE SYSTEM BY TAU 96. THE LLCC WILL REMAIN WITHIN THE NORTHEAST MONSOON FLOW THROUGH DISSIPATION, TRACKING TO THE SOUTHWEST. MODEL GUIDANCE PERSISTS WITH A WIDE VARIATION OF SOLUTIONS IN THE EXTENDED TAUS. THE OFFICIAL FORECAST FAVORS THE NGPS SOLUTION, WHICH SLOWS TS 26W BEFORE SHIFTING TO A SOUTHWESTWARD TRACK IN THE MID TAUS. CONSENSUS HAS BEEN INDICATING A MORE NORTHWARD TRACK WITH A LOOP BACK TO THE EAST BEFORE TRACKING SOUTHWEST BUT IS BEING AFFECTED BY WBAR AND GFS, BOTH INDICATING A SIGNIFICANT TRACK TO THE NORTHEAST PRIOR TO BEING CAUGHT IN THE NORTHEAST MONSOON FLOW. THIS REQUIRES THE LLCC TRACKING INTO THE NORTHEAST MONSOON FLOW AND IS ASSESSED AS A LESS LIKELY FORECAST SCENARIO. DUE TO THE LARGE SPREAD IN MODEL GUIDANCE, TRACK CONFIDENCE REMAINS LOW.// NNNN