Tropical Storm ETAU Advisory вт, 08.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (ETAU) WARNING NR 04//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 18W (ETAU), LOCATED APPROXIMATELY 579 NM SOUTH
OF YOKOSUKA, JAPAN, HAS TRACKED NORTHWARD AT 10 KNOTS OVER THE PAST
SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS THE
SYSTEM HAS OVERALL MAINTAINED ITS CONVECTIVE SIGNATURE. THE INITIAL
POSITION IS BASED ON THE ABOVE ANIMATION AND ON AGENCY FIXES WITH LOW
CONFIDENCE. THE INITIAL INTENSITY OF 35 KNOTS IS BASED ON AN OVERALL
ASSESSMENT OF AVAILABLE DVORAK ESTIMATES. UPPER-LEVEL ANALYSIS
INDICATES A GENERALLY FAVORABLE ENVIRONMENT WITH LOW VERTICAL WIND
SHEAR AND ROBUST POLEWARD VENTING. TS 18W IS CURRENTLY TRACKING ALONG
THE WESTERN EXTENSION OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO
THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 18W WILL TRACK NORTH-NORTHWESTWARD THROUGH TAU 36 ALONG THE
WESTERN PERIPHERY OF THE LOW- TO MID-LAYER REFLECTION OF THE STR. TS
18W SHOULD CONTINUE TO SLOWLY INTENSIFY THROUGH TAU 24 UNDER
FAVORABLE CONDITIONS. HOWEVER, AFTER TAU 24 THE SYSTEM WILL ENCOUNTER
STRONG VERTICAL WIND SHEAR ASSOCIATED WITH A DEEP SHORTWAVE TROUGH
FORECAST TO DIG OVER WESTERN JAPAN BY TAU 24. AFTER TAU 36, TS 18W
WILL WEAKEN FURTHER AS IT MAKES LANDFALL OVER HONSHU AND IS EXPECTED
TO DISSIPATE BY TAU 72. DYNAMIC GUIDANCE IS IN GOOD AGREEMENT,
LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK.//
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