Tropical Storm MALAKAS Advisory Wed Sep 14

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 18W (MALAKAS) WARNING NR 12//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 18W (MALAKAS), LOCATED APPROXIMATELY 637 NM
SOUTH-SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED
WEST-NORTHWESTWARD AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED
ENHANCED INFRARED SATELLITE IMAGERY SHOWS THE SYSTEM CONTINUES TO
CONSOLIDATE AS A COLD DENSE OVERCAST FEATURE BUILDS OVERHEAD. THE
INITIAL POSITION IS BASED ON A LOW REFLECTIVITY CIRCULATION FEATURE
IN THE 140938Z AMSU-B MICROWAVE SATELLITE PASS WITH FAIR CONFIDENCE.
THE INITIAL INTENSITY OF 70 KNOTS IS BASED ON AN OVERALL ASSESSMENT
OF AGENCY AND OBJECTIVE DVORAK ESTIMATES AND REFLECTS THE IMPROVED
CONVECTIVE SIGNATURE. UPPER LEVEL ANALYSIS INDICATES A MARGINAL
ENVIRONMENT WITH MODERATE (15-20 KNOT) VERTICAL WIND SHEAR (VWS).
HOWEVER, WATER VAPOR IMAGERY SHOWS A TUTT CELL TO THE NORTHEAST THAT
IS ENHANCING EASTWARD OUTFLOW WHICH IS PROVIDING EXCELLENT
VENTILATION TO THE CENTRAL CONVECTION. SEA SURFACE TEMPERATURES
(SSTS) REMAIN FAVORABLE NEAR 29 CELSIUS. TY 18W IS TRACKING ALONG
THE SOUTHERN PERIPHERY OF THE 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 TRACK WEST-NORTHWESTWARD THEN NORTHWESTWARD
THROUGH TAU 72 UNDER THE STR. TY MALAKAS WILL BEGIN TO RAPIDLY
INTENSIFY AS VWS DECREASES AND OUTFLOW IMPROVES. THE SYSTEM WILL
REACH A PEAK OF 120 KNOTS BY TAU 48. DYNAMIC MODEL GUIDANCE IS IN
GOOD AGREEMENT THROUGH THIS PORTION OF THE FORECAST.
   C. IN THE EXTENDED FORECAST, TY 18W WILL REACH THE WESTERN EXTENT
OF THE STEERING STR AND TURN NORTHEASTWARD INTO THE STRONG MID-
LATITUDE WESTERLIES, MAKING LANDFALL IN KYUSHU JUST AFTER TAU 96.
STRONG VWS WILL GRADUALLY WEAKEN THE CYCLONE AS IT ACCELERATES
NORTHEASTWARD. DYNAMIC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT
DURING THIS PORTION OF THE FORECAST; OVERALL, THERE IS FAIR
CONFIDENCE IN THE JTWC TRACK FORECAST.//
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