Tropical Storm MALAKAS Advisory 15.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 18W (MALAKAS) WARNING NR 14//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 18W (MALAKAS), LOCATED APPROXIMATELY 460 NM EAST-
NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-NORTHWESTWARD AT
15 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS A COMPACT SYSTEM WITH A LARGE CENTRAL DENSE OVERCAST
OVER THE CIRCULATION CENTER. A 142214Z AMSU 89 IMAGE REVEALS DEEP
CONVECTIVE BANDING WRAPPING INTO THE SYSTEM ALONG NORTHERN AND
SOUTHERN SEMICIRCLES AND SUPPORTS THE CURRENT BEST TRACK POSITION
WITH FAIR CONFIDENCE. THE INITIAL INTENSITY OF 80 KNOTS IS BASED ON
DVORAK CURRENT INTENSITY ESTIMATES OF T4.5 (77 TO 90 KNOTS) FROM
PGTW AND RJTD. UPPER-LEVEL ANALYSIS INDICATES A FAVORABLE
ENVIRONMENT WITH IMPROVING OUTFLOW AND WEAK (5 TO 10 KNOTS) VERTICAL
WIND SHEAR (VWS). SSTS ALSO REMAIN FAVORABLE NEAR 29 CELSIUS. TY 18W
IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED
SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 18W WILL CONTINUE TRACKING ON A NORTHWEST TRAJECTORY
THROUGH TAU 36 UNDER THE STEERING INFLUENCE OF THE STR. TY MALAKAS
WILL BEGIN TO RAPIDLY INTENSIFY AS UPPER-LEVEL OUTFLOW CONTINUES TO
IMPROVE. THE SYSTEM WILL REACH A PEAK INTENSITY OF 120 KNOTS BY TAU
36. FROM TAU 36 TO 72, THE SYSTEM IS FORECAST TO SLOW IN FOREWARD
SPEED AT IT ROUNDS THE WESTERN PERIPHERY OF THE RIDGE, AND TRACK ON
A NORTHWARD TRAJECTORY WITHIN A WEAKNESS IN THE STR. DYNAMIC MODEL
GUIDANCE IS IN GOOD AGREEMENT THROUGH THIS PORTION OF THE FORECAST.
   C. AFTER TAU 72, THE SYSTEM WILL BEGIN ACCELERATING NORTHEASTWARD
WITHIN STRONG MID-LATITUDE WESTERLY FLOW. VWS WILL ALSO INCREASE
RAPIDLY BETWEEN TAU 72 AND TAU 120 LEADING TO RAPID WEAKENING OF TY
MALAKAS. THIS SYSTEM IS FORECAST TO MAKE LANDFALL IN KYUSHU BETWEEN
TAU 96 AND 120. DYNAMIC MODEL GUIDANCE IS IN FAIR AGREEMENT DURING
THIS PORTION OF THE FORECAST DUE TO THE UNCERTAINTY IN THE DEGREE OF
RECURVATURE OF THE SYSTEM. OVERALL, THERE IS GOOD CONFIDENCE IN THE
JTWC TRACK FORECAST.//
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