WDPN31 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 25W (JEBI) WARNING NR 
22//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 25W (JEBI), LOCATED APPROXIMATELY 314 NM 
SOUTHWEST OF IWO TO, HAS TRACKED NORTHWESTWARD AT 10 KNOTS OVER THE 
PAST SIX HOURS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE 
USING ANIMATED ENHANCED INFRARED SATELLITE IMAGERY WHICH SHOWS THE 
SYSTEM HAS AN APPROXIMATELY 22 NM RAGGED EYE AND DECAYING 
CONVECTION, PARTICULARLY ON THE NORTHERN HALF OF THE STORM. THE 
MIMIC TOTAL PRECIPITABLE WATER LOOP SHOWS THAT DRY AIR IS WRAPPING 
IN FROM THE WEST, LIKELY EXPLAINING THE DROP IN CONVECTION. THE 
INITIAL INTENSITY OF 135 KNOTS IS BASED ON MULTI-AGENCY DVORAK 
CURRENT INTENSITY ESTIMATES OF T6.5-T7.0 (127-140 KTS). ASIDE FROM 
THE DRY AIR ENTRAINING IN FROM THE WEST, THE ENVIRONMENT IS 
FAVORABLE WITH LOW (5-15 KTS) VERTICAL WIND SHEAR (VWS), GOOD RADIAL 
OUTFLOW, AND WARM (29-30 C) SEA SURFACE TEMPERATURES (SSTS). THE 
CYCLONE IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A 
SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING. 
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE 
PREVIOUS WARNING. 
   B. AROUND TAU 48, STY 25W WILL ROUND THE STR AXIS AND BEGIN 
ACCELERATING POLEWARD TOWARD SOUTHERN HONSHU, PASSING JUST EAST OF 
KYOTO AROUND TAU 60. THE CYCLONE HAS BEGUN TO WEAKEN DUE TO SLIGHTLY 
DEGRADED OUTFLOW AND DRY AIR ENTRAINMENT. THIS TREND IS EXPECTED TO 
CONTINUE AND THE INTENSITY WILL WEAKEN STEADILY TO 80 KNOTS BY TAU 
72. NUMERICAL MODEL GUIDANCE IS INITIALLY IN TIGHT AGREEMENT BUT 
DIFFERENCES IN ALONG TRACK SPEED CAUSE THE SPREAD TO INCREASE 
SIGNIFICANTLY AFTER TAU 36. CONFIDENCE IN THIS PORTION OF THE JTWC 
TRACK FORECAST IS LOW, PRIMARILY DUE TO INCREASING UNCERTAINTY IN 
ALONG-TRACK SPEED AFTER TAU 36.
   C. AFTER TAU 72, STY 25W WILL ACCELERATE ON ITS POLEWARD TRACK 
AND WEAKEN. THROUGHOUT THIS PERIOD, AN APPROACHING MID-LATITUDE 
CYCLONE WILL ENHANCE TEMPERATURE ADVECTION AND CAUSE STY 25W TO 
COMPLETE EXTRATROPICAL TRANSITION BY TAU 96. THE JTWC FORECAST TRACK 
CLOSELY FOLLOWS THE CONSENSUS TRACK AND IS REFLECTIVE OF ALL THE 
MODEL TRACK GUIDANCE. THE INTENSITY IS EXPECTED TO STEADILY DECAY 
DUE TO INCREASING VWS AND COOLER SSTS IN THE SEA OF JAPAN. ALTHOUGH 
THE MODELS GENERALLY AGREE ON THE PATH THE CYCLONE WILL FOLLOW, 
DIFFERENCES IN ALONG-TRACK SPEED CONTINUE TO INCREASE THE 
UNCERTAINTY AND CONFIDENCE IN THE JTWC FORECAST TRACK IS LOW FOR 
THIS PORTION OF THE FORECAST.//
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