WDPN31 PGTW 041500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 22W (HAGUPIT) WARNING NR 15// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUPER TYPHOON (STY) 22W (HAGUPIT), LOCATED APPROXIMATELY 640 NM EAST-SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-NORTHWESTWARD AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY INDICATES A SLIGHT WEAKENING TREND WITH A MORE ASYMMETRIC CONVECTIVE STRUCTURE, HOWEVER, THE SYSTEM HAS MAINTAINED A 12-NM ROUND EYE AND INTENSE CORE CONVECTION. A 040800Z SSMIS 91 GHZ IMAGE DEPICTS A POSSIBLE EYEWALL REPLACEMENT CYCLE (ERC) AND A 041205Z METOP-B 89 GHZ IMAGE INDICATES THAT THE BULK OF THE DEEP CONVECTION IS DISPLACED OVER THE WESTERN SEMI-CIRCLE DUE TO MODERATE EASTERLY VERTICAL WIND SHEAR (VWS). BASED ON THE SMALL EYE, THERE IS GOOD CONFIDENCE IN THE CURRENT POSITION AND RECENT TRACK MOTION. AS A RESULT OF THE RECENT WEAKENING TREND, DVORAK INTENSITY ESTIMATES HAVE DECREASED TO T7.0 (140 KNOTS) ALTHOUGH CURRENT INTENSITY ESTIMATES REMAIN AT T7.5 (155 KNOTS), THEREFORE, THE INITIAL INTENSITY HAS BEEN DECREASED SLIGHTLY TO 150 KNOTS WITH SOME POTENTIAL FOR FURTHER WEAKENING DUE TO THE ERC. UPPER-LEVEL ANALYSIS INDICATES THAT STY 22W REMAINS IN A FAVORABLE ENVIRONMENT WITH NEAR RADIAL OUTFLOW OFFSETTING MODERATE (15 TO 20 KNOTS) VERTICAL WIND SHEAR (VWS). STY HAGUPIT IS CURRENTLY TRACKING ALONG THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. STY HAGUPIT WILL MAINTAIN A GENERALLY WEST TO WEST- NORTHWESTWARD TRAJECTORY UNDER THE STEERING INFLUENCE OF THE STR THROUGH TAU 72. BETWEEN TAUS 24-48, THE SYSTEM IS EXPECTED TO SLOW SLIGHTLY AS AN APPROACHING, WEAK SHORTWAVE TROUGH PASSING TO THE NORTH WILL PRODUCE A WEAKNESS IN THE STEERING RIDGE. BASED ON THE INITIAL EVIDENCE OF AN ERC AND THE MODERATE VWS, STY 22W IS FORECAST TO WEAKEN SLOWLY THROUGH TAU 48 THEN WEAKEN MORE RAPIDLY AFTER TAU 48 AS THE SYSTEM INTERACTS WITH LAND. WITH THE EXCEPTION OF HWRF AND JENS, THE DYNAMIC MODELS HAVE COME INTO CLOSER AGREEMENT ON A STRAIGHT-RUNNER TRACK INTO THE CENTRAL PHILIPPINES. RECENT 500MB ANALYSES SHOW THAT THE STR HAS MAINTAINED TO THE NORTH OF THE SYSTEM AS A SHORTWAVE TROUGH PROPAGATED OVER WESTERN JAPAN. C. IN THE EXTENDED TAUS, THE BULK OF THE DYNAMIC MODELS HAVE COME INTO CLOSER AGREEMENT ON A GENERALLY WESTWARD TRACK OVER THE PHILIPPINES. HWRF AND JENS ARE THE PRIMARY OUTLIERS, INDICATING A SHARP POLEWARD TURN. AS PREVIOUSLY MENTIONED, THERE IS NO EVIDENCE IN THE UPPER-LEVEL ANALYSES THAT THE MIDLATITUDE TROUGH IS DEEP ENOUGH TO WEAKEN THE STR, THEREFORE, THE RE-CURVATURE SCENARIO IS INCREASINGLY UNLIKELY. STY 22W IS FORECAST TO WEAKEN SIGNIFICANTLY AS IT TRACKS OVER THE PHILIPPINES. OVERALL, THERE IS STILL LOW CONFIDENCE IN THE EXTENDED FORECAST TRACK DUE TO THE BIFURCATION IN THE MODELS AND UNCERTAINTY IN THE EXACT TRACK WESTWARD WITH THE DYNAMIC MODELS IN FAIR AGREEMENT.// NNNN