Tropical Storm MALAKAS Advisory So, 18.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 18W (MALAKAS) WARNING NR 26//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 18W (MALAKAS), LOCATED APPROXIMATELY 231 NM WEST OF
KADENA AB, HAS TRACKED NORTHEASTWARD AT 09 KNOTS OVER THE PAST SIX
HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS FURTHER
WARMING OF CONVECTIVE CLOUD-TOPS, WHILE THE SYSTEM CONTINUES TO
ELONGATE, INDICATING SLIGHT WEAKENING HAS OCCURRED. A 172205Z
CORIOLIS 37 GHZ IMAGE REVEALS A DETERIORATION OF DEEP CONVECTION
ALONG THE WESTERN SEMICIRCLE WHERE DRY, CONTINENTAL AIR IS IMPINGING
ON THE SYSTEM. THE CURRENT BEST TRACK POSITION IS SUPPORTED BY THE
AFOREMENTIONED IMAGERY WITH GOOD CONFIDENCE. THE INITIAL INTENSITY
OF 80 KNOTS IS BASED ON AN OVERALL ASSESSMENT OF AGENCY AND
OBJECTIVE DVORAK ESTIMATES AND REFLECTS THE WEAKENED STATE. UPPER-
LEVEL ANALYSIS INDICATES A MARGINALLY-FAVORABLE ENVIRONMENT WITH
GOOD OUTFLOW OFFSET BY MODERATE (15 TO 20 KNOTS) VERTICAL WIND SHEAR
(VWS). SEA SURFACE TEMPERATURES REMAIN FAVORABLE (AROUND 28C),
HOWEVER OCEAN HEAT CONTENT VALUES REMAINS UNFAVORABLE FOR
DEVELOPMENT. THE CYCLONE IS TRACKING ALONG THE WESTERN PERIPHERY OF
A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE EAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 18W WILL CONTINUE TRACKING ON A NORTHEASTWARD TRAJECTORY
AND ACCELERATING, AS IT ROUNDS THE WESTERN PERIPHERY OF THE STR, AND
BECOMES EMBEDDED WITHIN THE STRONG MID-LATITUDE WESTERLIES. THIS
SYSTEM IS FORECAST TO WEAKEN GRADUALLY THROUGH THE FIRST 48 HOURS AS
VWS SLOWLY INCREASES. THE SYSTEM WILL MAKE LANDFALL OVER KYUSHU,
JAPAN, BETWEEN TAU 36 AND 48.
   C. BEYOND TAU 72, TY MALAKAS WILL CONTINUE ACCELERATING
NORTHEASTWARD ALONG COASTAL JAPAN WITHIN THE WESTERLIES. VWS WILL
BECOME INCREASINGLY UNFAVORABLE, RESULTING IN RAPID WEAKENING OF THE
SYSTEM. TC 18W IS FORECAST TO FULLY DISSIPATE BY TAU 96, JUST
OFFSHORE OF TOKYO. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT ON
THE FORECAST TRACK, HOWEVER THERE ARE SOME DIFFERENCES IN THE SPEED
OF MOVEMENT OF TY MALAKAS. THEREFORE, THERE IS FAIR OVERALL
CONFIDENCE IN THE JTWC TRACK FORECAST.//
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