Tropical Storm MERANTI Advisory Sa, 13.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 16W (MERANTI) WARNING NR
17//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 16W (MERANTI), LOCATED APPROXIMATELY 436 NM
SOUTH OF KADENA AB, OKINAWA, JAPAN HAS TRACKED WEST-NORTHWESTWARD AT
15 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY DEPICTS AN IMPRESSIVE CYCLONE WITH A DEEP
CONVECTIVE CORE SURROUNDING A SHARP 8NM EYE WHICH SUPPORTS THE
CURRENT POSITION WITH HIGH CONFIDENCE. THE CLOUD TOPS HAVE WARMED
SLIGHTLY OVER THE PAST FEW HOURS AS THE SYSTEM RESPONDS TO DIURNAL
PHASES. A 121826Z AMSU MICROWAVE IMAGE SHOWS MULTIPLE CONVECTIVE
BANDS WRAPPING INTO THE WELL-DEFINED EYE. STY 16W REMAINS AT 155
KNOTS BASED ON DVORAK CURRENT INTENSITY ESTIMATES OF T7.5 (155
KNOTS) FROM PGTW AND RJTD. THE WATER VAPOR LOOP SHOWS RADIAL OUTFLOW
DUE TO A POINT SOURCE ANTI-CYCLONE OVER THE TOP OF THE SYSTEM WITH
LOW (5-10 KNOT) VERTICAL WIND SHEAR (VWS). SEA SURFACE TEMPERATURES
NEAR 30 CELSIUS AND HIGH OCEAN HEAT CONTENT ARE ALSO FAVORABLE FOR
FURTHER INTENSIFICATION. STY 16W CONTINUES TO TRACK TOWARD THE WEST-
NORTHWEST UNDER THE STEERING INFLUENCE OF A SUBTROPICAL RIDGE (STR)
TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE; HOWEVER, THE FORECAST TRACK HAS
SHIFTED SOUTHWARD INTO THE TAIWAN STRAIT.
   B. THROUGH TAU 72, STY 16W WILL TRACK GENERALLY WEST-
NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE STR. VERY
FAVORABLE ENVIRONMENTAL CONDITIONS WILL SUPPORT THE POTENTIAL FOR
ADDITIONAL INTENSIFICATION OVER THE NEXT 12 TO 24 HOURS. AFTERWARDS,
LAND INTERACTION WITH TAIWAN AND INCREASING VWS WILL BEGIN THE
WEAKENING PHASE. STY MERANTI WILL MAKE LANDFALL ALONG THE COAST OF
CHINA JUST AFTER TAU 48 AS A STRONG TYPHOON. DYNAMIC MODEL GUIDANCE
SHOWS TWO POSSIBLE SCENARIOS FOR THE SYSTEM BUT OVERALL CONTINUE TO
WALK THE TRACK SOUTHWARD INTO THE TAIWAN STRAIT. THE FIRST SCENARIO
SHOWS LANDFALL OVER THE SOUTHERN TIP OF TAIWAN WITH THE SECOND
SCENARIO IS SHOWING A TRACK OVER THE TAIWAN STRAIT.
   C. IN THE EXTENDED FORECAST, STY 16W WILL CONTINUE TRACKING OVER
LAND AND FULLY DISSIPATE DUE TO LAND INTERACTION AND INCREASED VWS
DUE TO INTERACTION WITH THE ZONAL MID-LATITUDE WESTERLIES. MODEL
GUIDANCE IN THE EXTENDED FORECAST DIVERGES GREATLY DUE TO THE RAPID
WEAKENING OF THE CYCLONE. VWS IS EXPECTED TO BE IN EXCESS OF 30
KNOTS AT THIS TIME. THE CURRENT FORECAST HAS BEEN SHIFTED FURTHER
SOUTH, WITH LOW CONFIDENCE, CLOSE TO THE MULTI-MODEL CONSENSUS.//
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