Tropical Storm MALAKAS Advisory Sun Sep 18

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 18W (MALAKAS) WARNING NR 23//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 18W (MALAKAS), LOCATED APPROXIMATELY 72 NM EAST OF
TAIPEI, TAIWAN, HAS TRACKED NORTHWARD AT 12 KNOTS OVER THE PAST SIX
HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE
SYSTEM HAS MAINTAINED OVERALL CONVECTIVE DEPTH BUT WITH INCREASING
ELONGATION ALONG THE NORTHEAST QUADRANT. THE INITIAL POSITION IS
BASED ON A 10-NM RAGGED AND CLOUD FILLED EYE IN THE MSI LOOP AND ALSO
REFLECTED AS AN EYE FEATURE ON A COMPOSITE RADAR REFLECTIVITY LOOP
FROM THE JAPAN METEOROLOGICAL AGENCY. THE INITIAL INTENSITY OF 110
KNOTS IS BASED ON AN OVERALL ASSESSMENT OF AGENCY AND OBJECTIVE
DVORAK ESTIMATES. UPPER-
LEVEL ANALYSIS INDICATES THE CORE IS STILL IN AN AREA OF LOW VERTICAL
WIND SHEAR (VWS); HOWEVER, THE NORTHERN PERIPHERIES ARE NOW IN
MODERATE TO STRONG VWS. EQUATORWARD OUTFLOW REMAINS ROBUST AND SEA
SURFACE TEMPERATURES REMAIN VERY FAVORABLE NEAR 29 TO 30 CELSIUS. TY
MALAKAS IS TRACKING NORTHWARD ALONG THE PERIPHERY OF A DEEP-LAYERED
SUBTROPICAL RIDGE (STR) TO THE EAST-NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 18W IS FORECAST TO CONTINUE TO TRACK NORTHWARD OVER THE NEXT
12 HOURS AS IT ROUNDS THE WESTERN EDGE OF THE STR. AFTERWARDS, THE
SYSTEM WILL BEGIN TO ACCELERATE NORTHEASTWARD ON THE POLEWARD SIDE OF
THE STR, MAKING LANDFALL OVER KYUSHU, JAPAN, BEFORE TAU 72.
INCREASING VWS THEN LAND INTERACTION WILL REDUCE THE CYCLONE TO 50
KNOTS BY TAU 72.
   C. BEYOND TAU 72, TY MALAKAS WILL DRAG ACROSS THE RUGGED TERRAIN
OF JAPAN. THIS, IN ADDITION TO STRONG VWS, WILL CAUSE ITS DISSIPATION
OVER HONSHU BY TAU 96. THE NUMERIC GUIDANCE IS IN TIGHT AGREEMENT
WITH SOME DIFFERENCES IN LATERAL SPEED, LENDING FAIR CONFIDENCE IN
THE JTWC TRACK FORECAST.//
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