WDPN31 PGTW 150300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (KOPPU) WARNING NR 
09//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 24W (KOPPU), LOCATED APPROXIMATELY 627 NM 
EAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 10 KNOTS OVER 
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) 
DEPICTS SLIGHTLY DEEPENED CONVECTION OBSCURING THE LOW LEVEL 
CIRCULATION CENTER (LLCC). THE CURRENT POSITION IS BASED ON THE MSI 
AND SATELLITE FIXES FROM PGTW AND RJTD WITH GOOD CONFIDENCE. THE 
CURRENT INTENSITY OF 50 KNOTS BASED ON THE CURRENT STRUCTURE AND 
OVERALL ASSESSMENT OF DVORAK INTENSITY ESTIMATES FROM ALL REPORTING 
AGENCIES. UPPER-LEVEL ANALYSIS INDICATES A MARGINALLY-FAVORABLE 
ENVIRONMENT WITH MODERATE (20-25 KNOT) NORTHEASTERLY VERTICAL WIND 
SHEAR (VWS) BEING OFFSET BY THE STRONG DIVERGENT OUTFLOW. 
ADDITIONALLY, WARM SEA SURFACE TEMPERATURES (SSTS) IS CONDUCIVE FOR 
DEVELOPMENT. TS 24W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF THE 
DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC 
REASONING MESSAGE.
   B. TS KOPPU WILL CONTINUE TO TRACK WESTWARD THROUGH TAU 72 ALONG 
THE SOUTHERN PERIPHERY OF THE STEERING STR. A GRADUAL 
INTENSIFICATION IS EXPECTED AS VWS SLOWLY BECOMES MORE IN-PHASE WITH 
THE STORM MOTION. IN ADDITION TO THE IMPROVING UPPER-LEVEL 
CONDITIONS, SSTS AND OHC ALONG TRACK ARE CONDUCIVE FOR FURTHER 
INTENSIFICATION, LEADING TO A PEAK INTENSITY OF 110 KNOTS BY TAU 72.
   C. IN THE EXTENDED FORECAST, TS 24W WILL SLOW AND TURN MORE 
NORTHWESTWARD DUE TO A WEAKNESS IN THE STR. WEAKENING TREND IS 
EXPECTED AS THE SYSTEM TRACKS OVER THE MOUNTAINOUS TERRAIN IN LUZON. 
DYNAMIC MODEL GUIDANCE IS OVERALL IN GOOD AGREEMENT TROUGH TAU 72. 
HOWEVER, DUE TO SIGNIFICANT DIFFERENCE AMONG AVAILABLE TRACKERS IN 
THE EXTENDED TAUS, THERE IS LOW CONFIDENCE IN THE JTWC TRACK.//
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