WDPN31 PGTW 200300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (KOPPU) WARNING NR 
29//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 24W (KOPPU), LOCATED APPROXIMATELY 246 NM 
NORTH-NORTHWEST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWARD AT 04 
KNOTS OVER THE PAST SIX HOURS. ANIMATED MSI SHOWS A DISORGANIZED 
SYSTEM THAT CONTINUES TO HUG THE LUZON COAST, WITH THE BULK OF THE 
DEEP CONVECTION ON THE WESTERN SIDE OF THE RAGGED LLCC. A PREVIOUS 
192008Z SSMIS IMAGE CONTINUES TO SHOW THE DEEP CONVECTION ON THE 
WESTERN SIDE OF THE SYSTEM WITH LIMITED BANDING. DUE TO THE LOOSE 
STRUCTURE OF THE LLCC, THERE IS LOW CONFIDENCE IN THE INITIAL 
POSITION AND THE INTENSITY HAS BEEN DROPPED TO 50 KNOTS TO REFLECT 
THE DISORGANIZED STRUCTURE OF THE SYSTEM. TS 24W REMAINS IN A 
MARGINAL ENVIRONMENT WITH GOOD POLEWARD OUTFLOW WHICH ALMOST OFFSETS 
THE 20+ KNOTS OF VWS. TS KOPPU IS TRACKING ALONG THE NORTHERN SIDE 
OF A NER SOUTH OF THE SYSTEM AND AN INDUCED RIDGE BETWEEN TY 25W AND 
TS 24W.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TS 24W WILL SLOWLY TRACK EAST-NORTHEASTWARD, NORTH OF LUZON 
OVER THE NEXT 36 HOURS AS THE NER IS THE MAIN STEERING MECHANISM. 
DUE TO CONTINUED LAND INTERACTION AND INCREASED VWS, THE SYSTEM WILL 
SLOWLY DECREASE IN INTENSITY THROUGH TAU 36. BEYOND TAU 36, THE NER 
WILL TRACK TO THE WEST, PROMOTING THE INDUCED RIDGE TO BECOME THE 
MAIN STEERING MECHANISM, FORCING A POLEWARD COMPONENT TO THE TRACK. 
ADDITIONALLY, THE SYSTEM WILL MAINTAIN ITS INTENSITY OF 40 KNOTS 
THOUGH TAU 72 AS THE SLIGHTLY FAVORABLE INCREASED OUTFLOW WILL BE 
OFFSET BY INCREASED VWS.
   C. IN THE EXTENDED TAUS, TS KOPPU WILL CONTINUE TO TRACK POLEWARD 
ALONG THE WESTERN PERIPHERY OF THE BUILDING STR. THE SYSTEM WILL 
CONTINUE TO SLOWLY WEAKEN AS IT ENCOUNTERS ADDITIONAL VWS BETWEEN 
THE HIGHLY ZONALLY WESTERLIES TO THE NORTH AND THE STR TO THE EAST. 
DYNAMIC MODEL GUIDANCE CONTINUE SO BE FAIRLY WIDELY SPREAD TRACKING 
FROM THE EASTERN COAST OF TAIWAN TO EAST OF THE RYUKYU ISLAND CHAIN. 
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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