Tropical Storm MEGI Advisory Dom, 25-09

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (MEGI) WARNING NR 09//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 20W (MEGI), LOCATED APPROXIMATELY 486 NM SOUTH-SOUTHEAST
OF KADENA AB, HAS TRACKED WEST-NORTHWESTWARD AT 12 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY AND A
242205Z SSMIS 91 GHZ IMAGE DEPICTS DEEP CONVECTIVE BANDING TIGHTLY
WRAPPING INTO THE STORM CENTER WITH THE BEGINNING STAGES OF EYE
FORMATION. THE INITIAL POSITION IS BASED ON SATELLITE FIXES FROM
PGTW AND RJTD WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS
ASSESSED AT 90 KNOTS AND IS BASED ON THE IMPROVED CONVECTIVE
STRUCTURE AND DVORAK ESTIMATES FROM PGTW AND RJTD REPORTING T5.0 (90
KNOTS). UPPER-LEVEL ANALYSIS SHOWS EXCELLENT RADIAL OUTFLOW OVER THE
SYSTEM WITH A TUTT CELL POSITIONED TO THE EAST ASSISTING OUTFLOW.
VERTICAL WIND SHEAR IS VERY LOW (5 TO 10 KNOTS) AND SSTS ARE VERY
WARM, NEAR 30 CELSIUS. CURRENTLY TY MEGI IS TRACKING WEST-NORTHWEST
ALONG THE PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE.
3. FORECAST REASONING.
    A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING BULLETIN.
    B. TY MEGI WILL CONTINUE ON A WEST-NORTHWEST TRACK ALONG THE
CURRENT STEERING RIDGE THROUGHOUT THE FORECAST PERIOD.
INTENSIFICATION IS EXPECTED OVER THE NEXT 48 HOURS REACHING A PEAK
INTENSITY OF 110 KNOTS AS ENVIRONMENTAL CONDITIONS CONTINUE TO
REMAIN FAVORABLE. THERE IS POTENTIAL FOR THE EASTWARD POSITIONED
TUTT CELL TO MARGINALLY DISRUPT OUTFLOW, BUT THIS SCENARIO SHOULD
DECREASE AS IT DRIFTS TO THE SOUTHWEST AWAY FROM TY MEGI THROUGH THE
FORECAST PERIOD.  TY MEGI IS EXPECTED TO MAKE LANDFALL OVER THE
MOUNTAINOUS REGION OF SOUTHERN TAIWAN NEAR TAU 60, WEAKENING RAPIDLY
INTO A TROPICAL STORM AS IT RESURFACES OVER WATER SHORTLY THEREAFTER.
    C. IN THE EXTENDED FORECAST TY MEGI WILL CONTINUE WEST-NORTHWEST
ALONG THE CURRENT STEERING RIDGE INTO CHINA. RAPID DISSIPATION IS
EXPECTED OVER LAND JUST BEYOND TAU 120. DYNAMIC MODEL GUIDANCE IS
IN VERY TIGHT AGREEMENT WITH BOTH THE SPEED AND TRACK OF TY MEGI.
THE FORECAST TRACK IS PLACED WITH HIGH CONFIDENCE ALONG THE MULTI-
MODEL CONSENSUS.//
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