WDPN31 PGTW 101500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 22W (PRAPIROON) WARNING NR 13// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON 22W (PRAPIROON), LOCATED APPROXIMATELY 470 NM SOUTH-SOUTHEAST OF KADENA AIR BASE, OKINAWA, JAPAN, HAS TRACKED WEST- NORTHWESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A 101144Z SSMI-S MICROWAVE IMAGE DEPICT A WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH TIGHTLY-CURVED BANDING. ANIMATED WATER VAPOR IMAGERY SHOWS GOOD RADIAL OUTFLOW ENHANCED BY STRONG WESTERLY FLOW TO THE NORTH. THE INITIAL INTENSITY IS BASED ON CONGRUENT DVORAK ESTIMATES OF 90 KNOTS FROM PGTW, KNES, AND RJTD. THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION BASED ON THE EYE FEATURE IN THE MICROWAVE IMAGE. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS JUST TO THE SOUTH OF A RIDGE AXIS IN AN AREA OF LOW (05-10 KNOT) VERTICAL WIND SHEAR (VWS). THE CYCLONE IS TRACKING SLOWLY ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) SOUTH OF JAPAN. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 22W IS FORECAST TO CONTINUE ALONG ITS CURRENT TRACK THROUGH TAU 12, AFTERWARDS, IT SHOULD BEGIN TO DRIFT MORE POLEWARD AS THE STR IS ERODED BY A DEEP SHORTWAVE TROUGH, WHICH IS CURRENTLY OVER JAPAN. AFTER TAU 36, THE SYSTEM WILL RECURVE NORTHEASTWARD AS A REFLECTION OF THE NEAR-EQUATORIAL RIDGE TO THE SOUTHEAST BUILDS AND BECOMES THE DOMINANT STEERING MECHANISM. TY 22W WILL INTENSIFY UP TO 115 KNOTS DUE TO CONTINUED LOW VWS AND FAVORABLE OUTFLOW. DYNAMIC MODEL GUIDANCE IS IN GENERAL AGREEMENT ON THE RECURVATURE BUT IS IN POOR AGREEMENT ON THE SPEED AND TIMING OF THE TURN. THE JTWC TRACK FORECAST CONTINUES TO FAVOR THE SLOWER ECMWF, GFS AND UKMO SOLUTIONS. C. AFTER TAU 72, TY PRAPIROON WILL ACCELERATE SLIGHTLY AS IT TRACKS ALONG THE NORTHWESTERN PERIPHERY OF THE STR TOWARD A BREAK IN THE RIDGE. DYNAMIC MODEL GUIDANCE DIVERGES SIGNIFICANTLY WITH WBAR, GFDN AND NOGAPS INDICATING MUCH FASTER TRACK SPEEDS WHILE ECMWF AND JGSM INDICATE VERY SLOW TRACK SPEEDS. THE JTWC FORECAST FAVORS THE CONSISTENT GFS SOLUTION AND IS SLOWER THAN THE MULTI-MODEL CONSENSUS TO OFFSET THE FASTEST MODELS. TY 22W IS FORECAST TO WEAKEN SLIGHTLY DUE TO SLIGHTLY COOLER SST (26-27C) BUT SHOULD NOT ENCOUNTER STRONG VWS UNTIL IT IS FURTHER NORTH. ADDITIONALLY, THERE IS NO EVIDENCE OF EXTRA-TROPICAL TRANSITION DURING THE SPAN OF THIS FORECAST. // NNNN