Tropical Storm MALAKAS Advisory Mon Sep 19

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 18W (MALAKAS) WARNING NR 32//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
    TYPHOON (TY) 18W (MALAKAS), LOCATED APPROXIMATELY 132 NM SOUTH OF
SASEBO, JAPAN, HAS TRACKED EAST-NORTHEASTWARD AT 14 KNOTS OVER THE
PAST SIX HOURS.  ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS
THE SYSTEM HAS BECOME ELONGATED AND LOST CONVECTIVE DEPTH AS IT BEGAN
TO ENCOUNTER CROSS VERTICAL WIND SHEAR AND THE JAPANESE LANDMASS. THE
INITIAL POSITION IS BASED ON A COMPOSITE RADAR LOOP FROM KYUSHU WHICH
LINES UP WITH A MICROWAVE EYE FEATURE IN THE 190942Z SSMIS PASS. THE
INITIAL INTENSITY OF 100 KNOTS IS BASED ON AN OVERALL ASSESSMENT OF
AGENCY DVORAK ESTIMATES AND REFLECTS THE WEAKENING TREND. UPPER-LEVEL
ANALYSIS INDICATES THE SYSTEM HAS DRIFTED INTO STRONG (25-30 KNOT)
VERTICAL WIND SHEAR (VWS); HOWEVER, THE VWS IS PARTIALLY OFFSET BY
EXCELLENT OUTFLOW AND WARM SEA SURFACE TEMPERATURES. THE CYCLONE IS
TRACKING ALONG THE NORTHWESTERN 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 TO ACCELERATE NORTHEASTWARD ON THE
POLEWARD SIDE OF THE STR AS IT BECOMES EMBEDDED DEEPER INTO THE
STRONG MID-LATITUDE WESTERLIES. IT IS EXPECTED TO MAKE LANDFALL IN
KYUSHU OVER THE NEXT FEW HOURS. TY MALAKAS WILL THEN DRAG ACROSS THE
SOUTHERN COAST OF JAPAN. THE LAND INTERACTION, IN ADDITION TO VERY
STRONG VWS (GREATER THAN 40 KNOTS), WILL CAUSE ITS RAPID DISSIPATION
BY TAU 48. CONCURRENTLY, THE CYCLONE WILL UNDERGO EXTRA-TROPICAL
TRANSITION. THE NUMERIC GUIDANCE REMAINS IN TIGHT AGREEMENT WITH SOME
DIFFERENCES IN LATERAL SPEED, BUT OVERALL, THE TIGHT GROUPING LENDS
FAIR CONFIDENCE IN THE JTWC TRACK FORECAST.//
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