Tropical Storm MERANTI Advisory Wed Sep 14

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 16W (MERANTI) WARNING NR
23//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 16W (MERANTI), LOCATED APPROXIMATELY 40 NM
WEST-SOUTHWEST KAOHSIUNG, TAIWAN, HAS TRACKED NORTHWESTWARD AT 14
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY SHOWS THE SYSTEM HAS MAINTAINED A DEEP SYMMETRIC CONVECTIVE
SIGNATURE AND A 10-NM EYE. THE INITIAL POSITION IS BASED WITH HIGH
CONFIDENCE ON A COMPOSITE REFLECTIVITY RADAR LOOP FROM THE TAIWAN
CENTRAL WEATHER BUREAU. THE INITIAL INTENSITY OF 155 KNOTS IS BASED
ON A T7.5 DVORAK ESTIMATE FROM PGTW AND RJTD. UPPER LEVEL ANALYSIS
INDICATES THE SYSTEM IS JUST SOUTH OF THE RIDGE AXIS IN AN AREA OF
LIGHT EASTERLY VERTICAL WIND SHEAR (VWS) AND EXCELLENT RADIAL
OUTFLOW. SEA SURFACE TEMPERATURES AT 30 CELSIUS AND HIGH OCEAN HEAT
CONTENT ARE ALSO VERY FAVORABLE. STY 16W IS 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.
   B. STY 16W WILL TRACK GENERALLY WEST-NORTHWESTWARD THROUGHOUT ITS
LIFE SPAN UNDER THE STEERING INFLUENCE OF THE STR. INCREASING VWS AND
LAND INTERACTION, AS IT BRUSHES THE SOUTHERN COAST OF TAIWAN AND
APPROACHES EASTERN CHINA, WILL GRADUALLY WEAKEN THE SYSTEM. SHORTLY
BEFORE TAU 12, STY MERANTI WILL MAKE LANDFALL IN CHINA NEAR SHANTOU.
THE RUGGED TERRAIN AND INCREASED VWS WILL RAPIDLY ERODE THE SYSTEM,
DISSIPATING IT AS A SIGNIFICANT CYCLONE OVER LAND BY TAU 36. DYNAMIC
MODEL GUIDANCE REMAINS IN GOOD AGREEMENT, LENDING HIGH CONFIDENCE IN
THE JTWC TRACK FORECAST UP TO LANDFALL IN CHINA WHERE TRACK
VARIABILITY IS HIGH DUE TO LAND INTERACTION.//
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