Tropical Storm KOPPU Advisory Cts, 17.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (KOPPU) WARNING NR 16//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 24W (KOPPU), LOCATED APPROXIMATELY 237 NM EAST-
NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 08 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY CONTINUES TO SHOW DEEP CONVECTIVE BANDING WRAPPING TIGHTER
INTO THE LOW-LEVEL CIRCULATION CENTER. THE INITIAL POSITION IS BASED
ON A WARM PIXEL CLUSTER IN THE EIR LOOP AND ON CLOSELY-GROUPED FIXES
FROM ALL AGENCIES WITH HIGH CONFIDENCE. THE INITIAL INTENSITY OF 95
KNOTS IS HELD SLIGHTLY HIGHER THAN THE DVORAK ESTIMATES FROM PGTW,
KNES, AND RJTD TO REFLECT THE TIGHTER WRAP. UPPER-LEVEL ANALYSIS
INDICATES THE SYSTEM REMAINS IN A FAVORABLE ENVIRONMENT WITH LOW
VERTICAL WIND SHEAR AND DUAL OUTFLOW WITH A STRONG EQUATORWARD BIAS.
ADDITIONALLY, SEA SURFACE TEMPERATURES (SSTS) AT OVER 31 DEGREES
CELSIUS IN THE PHILIPPINE SEA ARE HIGHLY CONDUCIVE FOR FURTHER
DEVELOPMENT. THE CYCLONE IS TRACKING ALONG THE SOUTHERN PERIPHERY OF
AN EXTENSION OF THE DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 24W WILL CONTINUE TO TRACK WESTWARD THROUGH TAU 36 ALONG
THE SOUTHERN PERIPHERY OF THE STEERING STR EXTENSION. UPPER-LEVEL
DYNAMICS AND SSTS WILL REMAIN FAVORABLE LEADING TO A RAPID
INTENSIFICATION OVER THE NEXT 24 HOURS WITH A PEAK INTENSITY
OF 120 KNOTS NEAR TAU 18. THE CYCLONE WILL MAKE LANDFALL SHORTLY
AFTER TAU 24 NEAR CASIGURAN AND RAPIDLY DECAY AS IT TRACKS THROUGH
NORTHERN LUZON. BEYOND TAU 36, TY 24W WILL TURN POLEWARD AS THE STR
EXTENSION RETREATS AND AN INDUCED RIDGE FORMS BETWEEN TY 25W AND TY
24W AND ACTS AS THE WEAK PRIMARY STEERING MECHANISM FOR THE REMAINDER
OF THE FORECAST.
   C. IN THE EXTENDED FORECAST, TY KOPPU WILL EXIT INTO THE LUZON
STRAIT AT TROPICAL STORM STRENGTH AND CONTINUE TO TRACK NORTHWARD.
MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT THROUGH TAU 36, BUT
CONTINUES TO SHOW SIGNIFICANT SPREAD AFTERWARDS. DUE TO THE
UNCERTAINTY IN THE STORM MOTION AND DISPARITY AMONG AVAILABLE
TRACKERS IN THE EXTENDED TAUS, THE JTWC TRACK FORECAST CONFIDENCE
LEVEL IS LOW.//
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