WDPN31 PGTW 131500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 22W (PRAPIROON) WARNING NR 25// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 22W (PRAPIROON), LOCATED APPROXIMATELY 325 NM SOUTH- SOUTHEAST OF KADENA AIR BASE, OKINAWA, JAPAN, HAS TRACKED NORTHEASTWARD AT 05 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS THE SYSTEM HAS MAINTAINED DEEP CENTRAL CONVECTION AS EQUATORWARD OUTFLOW INCREASED TO COMPENSATE A DIMINISHING POLEWARD OUTFLOW CHANNEL. THE INITIAL POSITION IS EXTRAPOLATED FROM A SEMI-CLOSED EYE FEATURE ON A 131108Z SSMI MICROWAVE IMAGE. THE INITIAL INTENSITY IS AVERAGED FROM DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD RANGING FROM 65 TO 90 KNOTS. UPPER-LEVEL ANALYSIS INDICATES 22W IS LOCATED IN A REGION OF WEAK (5-10 KNOT) VERTICAL WIND SHEAR (VWS) AND SLIGHTLY WEST OF A POINT SOURCE ANTICYCLONE. ANIMATED WATER VAPOR IMAGERY SHOWS GOOD RADIAL OUTFLOW. HOWEVER, WEAKENING IS EVIDENT ALONG THE NORTHERN PERIPHERY. THE CYCLONE IS TRACKING ALONG THE NORTHWEST PERIPHERY OF A WEAK NEAR EQUATORIAL RIDGE (NER) TO THE SOUTHEAST. 3. FORECAST REASONING. A. THE FORECAST TRACK WAS ADJUSTED TO REFLECT A SLOWER STORM MOTION FROM TAU 24 TO TAU 72, OTHERWISE, THE FORECAST PHILOSOPHY REMAINS UNCHANGED. B. TY 22W IS EXPECTED TO CONTINUE ALONG ITS TRACK DURING THE NEXT 24 HOURS AS THE SYSTEM STEERS ALONG THE NORTHWESTERN PERIPHERY OF THE NER. AFTERWARDS, A BUILDING SUBTROPICAL RIDGE (STR) TO THE EAST WILL ASSUME STEERING, SIGNIFICANTLY SLOWING AND DEFLECTING THE SYSTEM IN A MORE POLEWARD DIRECTION. AFTER TAU 48, AN APPROACHING MID-LATITUDE TROUGH FROM THE NORTHWEST WILL WEAKEN THE STR AND CAUSE TY 22W TO RECURVE AND ACCELERATE NORTHEASTWARD. INCREASED POLEWARD OUTFLOW AHEAD OF THE APPROACHING TROUGH WILL RESULT IN A SLIGHT INCREASE IN INTENSITY. WITH THE EXCEPTION OF JGSM, ALL THE NUMERICAL MODELS INDICATE A SLOW DOWN, A POLEWARD DEFLECTION, AND ACCELERATED RECURVATURE, ALBEIT AT VARYING DEGREES. IT IS THE VARIANCE THAT GIVES LOW CONFIDENCE IN THIS PORTION OF THE FORECAST. C. AS THE STEERING RIDGE ERODES AFTER TAU 72, TY 22W IS EXPECTED TO ACCELERATE NORTHEASTWARD AND WEAKEN AS SSTS DECREASE AND VWS INCREASES. BY TAU 120 TY PRAPIROON WILL BEGIN TO INTERACT WITH THE BAROCLINIC ZONE AND BEGIN EXTRATROPICAL TRANSITION. DYNAMIC MODEL GUIDANCE ARE IN AGREEMENT WITH THE NORTHEASTWARD RECURVATURE BUT AT DIFFERENT TRACK SPEEDS. CONFIDENCE IN THE EXTENDED TRACK FORECAST REMAINS LOW AFTER DUE TO MODEL DIFFERENCES IN TRACK SPEEDS. // NNNN