Tropical Storm KOPPU Advisory Mon Oct 19

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (KOPPU) WARNING NR 25//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 24W (KOPPU), LOCATED APPROXIMATELY 173 NM
NORTH-NORTHWEST OF MANILA, PHILIPPINES, HAS TRACKED
NORTH-NORTHEASTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE SYSTEM HAS REMAINED
DISORGANIZED AS THE MAIN CONVECTION IS SHEARED WESTWARD OF A RAGGED
AND PARTLY OBSCURED LOW LEVEL CIRCULATION CENTER. THE INITIAL
POSITION IS BASED ON THE MSI ANIMATION AND EXTRAPOLATED FROM RECENT
MICROWAVE IMAGES AND IN-SITU OBSERVATIONS. THE INITIAL INTENSITY OF
75 KNOTS IS BASED ON AN OVERALL ASSESSMENT OF DVORAK ESTIMATES FROM
PGTW, KNES, AND RJTD. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS IN
AN AREA OF MODERATE (20 TO 25 KNOT) EASTERLY VERTICAL WIND SHEAR
(VWS) THAT IS PARTLY OFFSET BY STRONG DUAL OUTFLOW. LAND INTERACTION
DUE TO ITS PROXIMITY TO LUZON IS ALSO INHIBITING THE SYSTEM FROM
CONSOLIDATING. THE CYCLONE 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. TY 24W WILL SLOWLY TRACK NORTHEASTWARD THEN EAST-NORTHEASTWARD
OVER THE NEXT 48 HOURS AS A NEAR EQUATORIAL RIDGE BUILDING TO THE
SOUTH ASSUMES STEERING AND NUDGES THE SYSTEM BACK INTO LAND AT THE
NORTHWEST PORTION OF LUZON, ALBEIT MOMENTARILY. SHORTLY AFTER TAU 36,
TY 24W WILL EXIT INTO THE LUZON STRAIT, DEGRADED TO A 50-KNOT
TROPICAL STORM.
   C. IN THE EXTENDED TAUS, TY KOPPU WILL TURN NORTHWESTWARD AS A
BUILDING STR TO THE NORTHEAST ASSUMES STEERING. THE TYPHOON WILL
RE-INTENSIFY AS LOW VWS, GOOD OUTFLOW, AND WARM SSTS PREVAIL REACHING
70 KNOTS BY THE END OF FORECAST JUST EAST OF TAIPEI, TAIWAN. DYNAMIC
MODEL GUIDANCE CONTINUES TO SHOW A WIDE SPREAD IN THE MODEL ENVELOPE
LEADING TO AN OVERALL LOW CONFIDENCE IN THE JTWC FORECAST TRACK WHICH
IS POSITIONED NEAR THE MULTI-MODEL CONSENSUS.//
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