Tropical Storm NAMTHEUN Advisory 04 Σεπ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (NAMTHEUN) WARNING NR 14//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 15W (NAMTHEUN), LOCATED APPROXIMATELY 120 NM SOUTH OF
SASEBO, JAPAN, HAS TRACKED NORTHWARD AT 04 KNOTS OVER THE PAST SIX
HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE SHOWS CONTINUED
WARMING OF CENTRAL CONVECTION THAT HAS BECOME SLIGHTLY SHEARED
NORTHEASTWARD FROM THE LOW LEVEL CIRCULATION. HOWEVER, PGTW DVORAK
ANALYSIS CONTINUES TO INDICATE A COMPACT SYSTEM THAT IS TIGHTLY
WRAPPED AT THE LOW LEVELS. THE INITIAL POSITION IS BASED ON A
COMPOSITE RADAR LOOP FROM JMA AND LINED UP WITH A LOW REFLECTIVITY
CIRCULATION FEATURE IN THE 031456Z 36GHZ GPM MICROWAVE PASS WITH GOOD
CONFIDENCE. THE INITIAL INTENSITY OF 65 KNOTS IS BASED ON AN OVERALL
ASSESSMENT OF AGENCY AND OBJECTIVE DVORAK ESTIMATES. UPPER LEVEL
ANALYSIS INDICATES THE SYSTEM IS IN AN AREA OF HIGH (30-35 KNOT) VWS
AND INCREASING LAND INTERACTION. THE CYCLONE IS TRACKING ALONG THE
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) TO THE EAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY NAMTHEUN IS FORECAST TO CONTINUE TRACKING NORTHWARD ALONG
THE WESTERN PERIPHERY OF THE STR AND WEAKEN AS IT GAINS LATITUDE DUE
TO INCREASING VWS AND LAND INTERACTION. TY 15W WILL MAKE LANDFALL
ALONG THE WESTERN COAST OF KYUSHU, JUST SOUTH OF SASEBO, NEAR TAU 16.
AFTERWARDS THE SYSTEM WILL ROUND THE STR AXIS AND ACCELERATE
NORTHEASTWARD WITH THE MID-LATITUDE WESTERLY FLOW. RAPID DECAY WILL
BEGIN ONCE THE SYSTEM MOVES OVER COLD WATER (LESS THAN 25C) IN THE
SEA OF JAPAN. TY 15W WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) NEAR
TAU 36 AND COMPLETE ETT AS A WEAK COLD-CORE LOW BY THE END OF THE
FORECAST PERIOD. DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT,
LENDING HIGH CONFIDENCE IN THE JTWC FORECAST TRACK; HOWEVER, ANY
EASTWARD WOBBLE IN THE STORM MOTION WILL RESULT IN A MUCH WEAKER
SYSTEM MAKING LANDFALL DUE TO INCREASED LAND INTERACTION WITH HIGHER
TERRAIN.//
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