WDPN31 PGTW 191500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (KOPPU) WARNING NR 
27//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 24W (KOPPU), LOCATED APPROXIMATELY 224 NM 
NORTH OF MANILA, PHILIPPINES, HAS TRACKED NORTH-NORTHEASTWARD AT 04 
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE 
IMAGERY DEPICTS AN UNORGANIZED CONVECTIVE STRUCTURE ASSOCIATED WITH 
A RAGGED LOW LEVEL CIRCULATION CENTER (LLCC). A 191021Z PARTIAL 
CORIOLIS MICROWAVE IMAGE SHOWS THE WESTERN HALF OF THE SYSTEM AND 
PROVIDES SUPPORT THAT THE LLCC IS ALONG THE LUZON COAST. THE CURRENT 
POSITION IS BASED ON THE ABOVE IMAGERY WITH FAIR CONFIDENCE. THE 
INTENSITY HAS BEEN DECREASED DUE TO DECREASING DVORAK INTENSITY 
ESTIMATES AND REFLECTS THE CONTINUED WEAKENING OF THE CYCLONE IN ALL 
IMAGERY. UPPER LEVEL ANALYSIS INDICATES A MARGINAL ENVIRONMENT WITH 
MODERATE VERTICAL WIND SHEAR (VWS) BEING PARTIALLY OFFSET BY DUAL 
CHANNEL OUTFLOW. IN ADDITION, LAND INTERACTION CONTINUES TO IMPACT 
THE ORGANIZATION OF THE LLCC. TS KOPPU IS TRACKING ALONG THE WESTERN 
PERIPHERY OF AN EXTENSION OF THE DEEP-LAYERED SUB-TROPICAL RIDGE 
(STR) TO THE EAST-NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TS 24W WILL SLOWLY TRACK EAST-NORTHEASTWARD, SKIRTING THE 
NORTHWESTERN COAST OF LUZON, OVER THE NEXT 48 HOURS AS A NEAR 
EQUATORIAL RIDGE BUILDING TO THE SOUTH ASSUMES STEERING. NEAR TAU 
24, TS 24W WILL MOVE OVER THE LUZON STRAIT. AS THE CYCLONE TRACKS 
NEAR LAND THE LLCC WILL STRUGGLE TO RECONSOLIDATE CAUSING IT TO 
CONTINUE THE CURRENT WEAKENING TREND. AS TS KOPPU MOVES FURTHER AWAY 
FROM LUZON, IT WILL BEGIN TO STRENGTHEN ONCE AGAIN UNDER MARGINAL 
ENVIRONMENTAL CONDITIONS. BEYOND TAU 48, TS 24W WILL TURN POLEWARD 
UNDER THE INFLUENCE OF A BUILDING STR TO THE EAST.
   C. IN THE EXTENDED TAUS, TS KOPPU WILL CONTINUE TO TRACK POLEWARD 
ALONG THE WESTERN PERIPHERY OF THE BUILDING STR. THE SYSTEM WILL 
SLOWLY INTENSIFY AS IT TRACKS OVER WARM SSTS WITH GOOD DIVERGENT 
OUTFLOW. DYNAMIC MODEL GUIDANCE CONTINUES TO STRUGGLE TO FIND A 
SOLUTION TO THE COMPLEX STEERING ENVIRONMENT; SHOWING A WIDE SPREAD 
OF POSSIBILITIES. HOWEVER, THERE IS A BULK OF GUIDANCE NOW IN FAIR 
AGREEMENT THAT SUPPORTS THE CURRENT TRACK POSITIONING. THE TIMING 
AND STRENGTH OF THE BUILDING STR EAST OF TAIWAN IS STILL DEPENDENT 
ON TY 25W ACCELERATING TO THE NORTHEAST. DUE TO THE COMPLEX STEERING 
ENVIRONMENT AND THE CONTINUED SPREAD OF MODEL GUIDANCE, THERE IS LOW 
CONFIDENCE IN THE JTWC FORECAST TRACK WHICH IS POSITIONED NEAR THE 
MULTI-MODEL CONSENSUS.//
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