Tropical Storm LIONROCK Advisory wto., 30.08.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (LIONROCK) WARNING
NR 49//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 12W (LIONROCK), LOCATED APPROXIMATELY 275 NM SOUTH-
SOUTHEAST OF MISAWA, JAPAN, HAS TRACKED NORTHWARD AT 17 KNOTS OVER
THE PAST SIX HOURS. ANIMATED VISIBLE SATELLITE IMAGERY DEPICTS
DECAYING DEEP CENTRAL CONVECTION THAT IS DISPLACED TO THE EAST OF
THE ASSESSED LOW-LEVEL CIRCULATION CENTER (LLCC). THE INITIAL
POSITION IS BASED ON THE VISIBLE IMAGERY LOOP AND ON A LOW
REFLECTIVITY CIRCULATION FEATURE IN A 292126Z SSMIS MICROWAVE PASS
WITH MODERATE CONFIDENCE. TS 12W CONTINUES TO TRACK NORTH-
NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP MID-
LATITUDE HIGH TO THE EAST. THE INITIAL INTENSITY OF 55 KNOTS IS A
BLEND OF DVORAK CURRENT INTENSITY ESTIMATES OF 3.0 FROM ALL AGENCIES
AND A 292106Z WINDSAT SCATTEROMETER PASS, WHICH INDICATED WINDS
SLIGHTLY HIGHER THAN THE DVORAK INTENSITY ESTIMATES WOULD SUGGEST.
SYNOPTIC ANALYSIS INDICATES TS 12W IS IN AN AREA OF LOW TO MODERATE
(10-15 KNOT) WESTERLY VERTICAL WIND SHEAR (VWS), CONFIRMED BY THE
DISPLACED CONVECTIVE ACTIVITY. A DEEP TROUGH EXTENDING FROM THE
UPPER LOW OVER THE SEA OF JAPAN IS CREATING SUBSIDENCE ALONG THE
WESTERN PERIPHERY OF TS 12W, ALSO HELPING TO LIMIT CONVECTION IN
THAT PORTION OF THE STORM. A DEVELOPING UPPER LEVEL HIGH TO THE
SOUTH OF THE SYSTEM IS SUPPORTING GOOD DIVERGENT OUTFLOW TO THE EAST
AND SOUTH. TS 12W IS PASSING OVER AN EXTENSION OF THE KUROSHIO
CURRENT WITH SEA SURFACE TEMPERATURES (SSTS) NEAR 29 CELSIUS.
HOWEVER, TS 12W IS MOVING NEAR 20 KNOTS AND WILL RAPIDLY MOVE PAST
THIS WARM TONGUE AND INTO WATERS LESS THAN 25 CELSIUS.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY
SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS LIONROCK IS EXPECTED TO BEGIN TRACKING MORE NORTHWESTWARD
OVER THE NEXT 6 TO 12 HOURS AS THE PREVIOUSLY MENTIONED MID-LATITUDE
STEERING RIDGE TO THE NORTHEAST ANCHORED NEAR 45N STRENGTHENS AND
REMAINS NEARLY QUASI-STATIONARY. TS 12W WILL INCREASE FORWARD SPEED
AND MAKE LANDFALL NORTH OF SENDAI, JAPAN AND MOVE INTO THE SEA OF
JAPAN. AS THE SYSTEM CROSSES HONSHU, THE COMBINATION OF HIGHER
TERRAIN, INCREASED VWS AND INTERACTION WITH THE MID-LATITUDE
DYNAMICS ASSOCIATED WITH THE DEEP UPPER-LEVEL LOW IN THE SEA OF
JAPAN WILL RESULT IN A RAPID DECAY OF THE SYSTEM BEFORE MAKING A
FINAL LANDFALL NEAR VLADIVOSTOK, RUSSIA BY TAU 24. WHILE TS 12W WILL
BEGIN EXTRA-TROPICAL TRANSITION, IT WILL MAKE LANDFALL IN RUSSIA AND
DISSIPATE BEFORE COMPLETING THE TRANSITION. DYNAMIC GUIDANCE REMAINS
IN FAIRLY GOOD AGREEMENT THEREFORE, THERE IS HIGH CONFIDENCE IN THE
JTWC FORECAST TRACK.//
NNNN
NNNN