Tropical Storm NAMTHEUN Advisory 05 Σεπ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W (NAMTHEUN) WARNING
NR 18//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 15W (NAMTHEUN), LOCATED APPROXIMATELY 5 NM
EAST OF SASEBO, JAPAN, HAS TRACKED  NORTHEASTWARD AT 04 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND
THE KYUSHU RADAR LOOP SHOW THE CENTRAL CONVECTION HAS SIGNIFICANTLY
ERODED AND DISPERSED AS THE SYSTEM MADE LANDFALL INTO WESTERN KYUSHU.
THE INITIAL POSITION IS BASED ON THE RADAR LOOP AND FROM THE 18Z JMA
OBSERVATION MAP WITH FAIR CONFIDENCE. THE INITIAL INTENSITY OF 35
KNOTS IS BASED ON THE RJTD DVORAK INTENSITY ESTIMATE AND INTERPOLATED
FROM NEARBY SURFACE OBSERVATIONS. ENVIRONMENTAL CONDITIONS REMAIN
UNFAVORABLE DUE TO HIGH (30-35 KNOT) VERTICAL WIND SHEAR (VWS) AND
LAND INTERACTION. THE CYCLONE IS TRACKING NORTHEASTWARD ON THE
POLEWARD SIDE OF THE SUBTROPICAL RIDGE AXIS.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS NAMTHEUN WILL ACCELERATE NORTHEASTWARD INTO THE SEA OF JAPAN
(SOJ) WITH THE MID-LATITUDE WESTERLY FLOW WHERE IT WILL CONTINUE TO
WEAKEN DUE TO COLD WATER (LESS THAN 25C) AND INCREASING VWS.
CONCURRENTLY, TS 15W WILL UNDERGO EXTRA-TROPICAL TRANSITION (ETT) AND
COMPLETE ETT AS A WEAK COLD-CORE LOW BY TAU 36. THERE IS A DISTINCT
POSSIBILITY THAT THE SYSTEM WILL DISSIPATE IN THE SOJ DURING ETT.
DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT, LENDING HIGH CONFIDENCE
IN THE JTWC FORECAST TRACK.//
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