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WDPN33 PGTW 070300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 31W (HAIYAN) WARNING NR 16// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUPER TYPHOON 31W (HAIYAN), LOCATED APPROXIMATELY 123 NM NORTHWEST OF KOROR, PALAU, HAS TRACKED WEST-NORTHWESTWARD AT 16 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY REVEALS STY 31W HAS MAINTAINED THE DEEP CONVECTIVE EYEWALL, WITH DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD MAINTAINING THE CURRENT INTENSITY AT 150 KNOTS. SEA SURFACE TEMPERATURES (SSTS) ALONG THE TRACK REMAIN VERY FAVORABLE PROVIDING AMPLE SURFACE HEATING, SUPPORTING THE SUPER TYPHOON INTENSITY OVER THE PAST FEW HOURS. UPPER LEVEL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH NEAR- RADIAL OUTFLOW AND LOW (05 TO 10 KNOTS) VERTICAL WIND SHEAR. STY 31W IS CURRENTLY TRACKING ALONG THE SOUTHERN PERIPHERY OF THE DEEP- LAYERED SUBTROPICAL RIDGE (STR), WHICH IS ENTRENCHED TO THE NORTH. 3. FORECAST REASONING. A. NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. STY 31W IS EXPECTED TO MAINTAIN A WESTWARD TRACK ALONG THE SOUTHERN EDGE OF THE STR, SHIFTING TO A WEST-NORTHWESTWARD TRACK BY TAU 72. DUE TO VERY FAVORABLE ENVIRONMENTAL CONDITIONS, THE SYSTEM IS EXPECTED TO REMAIN AT SUPER TYPHOON INTENSITY OVER THE NEXT 24 HOURS. LANDFALL WITH THE PHILIPPINES IS ANTICIPATED AROUND TAU 24 AND WILL START TO IMPACT THE LOW LEVEL INFLOW, LEADING TO A SLIGHT WEAKENING TREND THROUGH TAU 72. STY 31W WILL TRACK INTO THE SOUTH CHINA SEA (SCS) WHERE SSTS BEGIN TO SLOWLY DECREASE, AND SUBSEQUENTLY THE SURFACE HEAT POTENTIAL WILL NOT SUPPORT THE STRONGER SUPER TYPHOON INTENSITIES. C. IN THE EXTENDED TAUS, STY 31W IS FORECAST TO WEAKEN AFTER TAU 72 AS IT TRACKS OVER MARGINAL SSTS IN THE WESTERN SCS AND BEGINS TO ENCOUNTER LAND, MAKING LANDFALL SHORTLY BEFORE TAU 96, WHICH WILL LEAD TO A MORE RAPID WEAKENING OF THE LOW LEVEL STRUCTURE AS THE SYSTEM TRACKS INTO THE CENTRAL REGION OF SOUTHEASTERN ASIA. DYNAMIC GUIDANCE REMAINS IN GOOD AGREEMENT THROUGH THE EXTENDED TAUS, THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST.// NNNN