WDPN31 PGTW 301500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (BOPHA) WARNING NR 20// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 26W (BOPHA) LOCATED APPROXIMATELY 605 NM EAST- SOUTHEAST OF PALAU, HAS TRACKED WEST-NORTHWESTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED IMAGERY (EIR) DEPICTS TIGHTLY CURVED SPIRAL BANDING WRAPPING AROUND A GROWING LOW LEVEL CIRCULATION CENTER. THE CURRENT POSITION IS BASED ON POSITION FIXES FROM PGTW AND RJTD, WHICH ARE IN CLOSE AGREEMENT. THE INTENSITY IS ASSESSED AT 65 KNOTS BASED ON DVORAK ESTIMATES OF THE SAME FROM ALL AGENCIES. UPPER-LEVEL ANALYSIS INDICATES TY 26W IS SOUTH OF A RIDGE AXIS, WITH GOOD DIFFLUENCE, LOW (10 KNOTS) VERTICAL WIND SHEAR (VWS), AND A POINT SOURCE OVERHEAD PROVIDING FAVORABLE RADIAL OUTFLOW. THIS OUTFLOW IS READILY APPARENT IN THE ANIMATED WATER VAPOR LOOP. ADDITIONALLY, THE UPPER-LEVEL WARM CORE ANOMALY HAS INCREASED TO PLUS FOUR DEGREES, INDICATIVE OF A STRONG VERTICAL CIRCULATION. THE SYSTEM IS CONTINUING TO TRACK WEST- NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE DEEP-LAYERED SUBTROPICAL RIDGE POSITIONED TO THE NORTH. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 26W IS FORECAST TO TRACK WEST-NORTHWESTWARD THROUGHOUT THE PERIOD AS IT MOVES ALONG THE SOUTHWESTERN PERIPHERY OF THE CURRENT STEERING RIDGE. CONTINUED FAVORABLE ENVIRONMENTAL CONDITIONS, INCLUDING FAVORABLE OUTFLOW, LOW VWS, AND PASSAGE OVER VERY WARM WATER, SHOULD ALLOW FOR STEADY INTENSIFICATION TO A PEAK NEAR 110 KNOTS BY TAU 72. DYNAMIC MODEL GUIDANCE HAS REMAINED IN FAIR AGREEMENT THROUGH TAU 72, WITH ALL MODELS INDICATING A NEAR CONSTANT WEST-NORTHWESTWARD MOVEMENT. THERE IS HIGH CONFIDENCE IN THIS PORTION OF THE TRACK FORECAST. C. IN THE EXTENDED TAUS, TY 26W IS EXPECTED TO TRACK NORTHWESTWARD TOWARD A WEAKNESS IN THE STR, WHICH WILL DEVELOP IN RESPONSE TO A BROAD UPPER-LEVEL TROUGH OVER THE EAST CHINA SEA. BY TAU 96 THE INTENSITY SHOULD BEGIN TO DECREASE AS THE SYSTEM APPROACHES THE CENTRAL PHILIPPINES. BY TAU 120, INTERACTION WITH THE PHILIPPINE ISLANDS AND INCREASING VWS WILL RESULT IN ADDITIONAL WEAKENING. THE OFFICIAL FORECAST IS CLOSE TO CONSENSUS, BUT ADJUSTED SLIGHTLY SLOWER AND POLEWARD IN FAVOR OF THE GFS, ECMWF, AND UKMET MODEL SOLUTIONS, WHICH DEPICT SLIGHTLY MORE WEAKENING IN THE STR VERSUS NOGAPS AND GFDN WHICH ARE TOO FAST DUE TO A STRONGER STR. TRACK FORECAST CONFIDENCE IS LOW DURING THIS PERIOD DUE TO THE UNCERTAINTY OF THE DEPTH AND POSITION OF THE UPPER-LEVEL TROUGHING AND ORIENTATION OF THE SUBTROPICAL RIDGE AT THIS TIME.// NNNN