Tropical Storm LIONROCK Advisory dom, 28.08.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (LIONROCK) WARNING NR 41//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
  TYPHOON 12W (LIONROCK), LOCATED APPROXIMATELY 265 NM WEST-
NORTHWEST OF IWO TO, HAS TRACKED NORTHEASTWARD AT 11 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS
IMPROVED BANDING STRUCTURE IN THE LAST SIX HOURS WRAPPING INTO A
TIGHTLY WOUND 15 NM EYE. SATELLITE IMAGERY ALSO SHOWS SLIGHTLY
WEAKENED CONVECTION ON THE WESTERN PERIPHERY DUE TO SUBSIDENCE
PROVIDED BY WEAK RIDGING BETWEEN TY 12W AND THE APPROACHING TROUGH
MOVING OVER SOUTHERN JAPAN. THE INITIAL POSITION IS BASED ON
SATELLITE EYE FIXES FROM PGTW AND RJTD WITH GOOD CONFIDENCE. THE
INITIAL INTENSITY IS ASSESSED AT 110 KNOTS AND IS BASED ON DVORAK
ESTIMATES FROM RJTD REPORTING T5.5 (102 KNOTS) AND PGTW REPORTING
T6.0 (115 KNOTS). UPPER-LEVEL ANALYSIS SHOWS STEADY RADIAL OUTFLOW
WITH A VERY STRONG EQUATORWARD CHANNEL AND VERY LOW VERTICAL WIND
SHEAR. SEA SURFACE TEMPERATURES REMAIN FAVORABLE AROUND 30 CELSIUS.
CURRENTLY TY 12W IS TRACKING NORTHEAST ALONG THE PERIPHERY OF THE
NEAR-EQUATORIAL RIDGE (NER) TO THE SOUTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. IN THE NEAR-TERM FORECAST TY 12W WILL CONTINUE TRACKING
NORTHEAST ALONG THE NER. ENVIRONMENTAL CONDITIONS WILL REMAIN
FAVORABLE FOR THE NEXT 24 HOURS MAINTAINING THE INTENSITY AROUND
105 KNOTS WITH GRADUAL OSCILLATIONS. BEYOND TAU 24 STEADY WEAKENING
IS EXPECTED AS THE ENVIRONMENT STARTS TO DETERIORATE. BEGINNING
AROUND TAU 48 THE TRACK WILL BEGIN TO SHIFT NORTHWEST AS STEERING
TRANSITIONS FROM THE NER TO A NORTHERN RIDGE POSITIONED SOUTH OF
KAMCHATKA.
   C. IN THE EXTENDED FORECAST THE NORTHERN RIDGE WILL STEER TY 12W
ALONG A NORTHWESTERN TRACK INTO A NEGATIVELY TILTED TROUGH OVER
JAPAN. LANDFALL OVER NORTHERN HONSHU IS EXPECTED AROUND TAU 60.
SOMEWHERE AROUND TAU 72 TY 12W WILL START TRANSITIONING INTO
AN EXTRATROPICAL SYSTEM BECOMING FULLY EXTRATROPICAL BY TAU 96.
DYNAMIC MODEL GUIDANCE IS SHOWING TWO DIFFERENT SCENARIOS. NAVGEM
AND MESOSCALE SOLUTIONS, COAMPS-TC AND GFDN (BOTH INITIALIZED BY
NAVGEM), ARE SHOWING A WEAKENED NER, RESULTING IN A TRACK MORE
SOUTHWARD IN THE NEAR TERM AND A TRAJECTORY SUFFICIENTLY SOUTH TO
AVOID THE STEERING TRANSITION; ULTIMATELY ENDING IN A QUASI-
STATIONARY SCENARIO NEAR 150 DEGREES EAST. THIS IS AN UNLIKELY
SOLUTION AS THE NER HAS ALREADY SHOWN SIGNIFICANT BUILDING,
EVIDENCED BY THE EXPANDING SOUTHERN WIND FIELD. ALL OTHER SOLUTIONS
IN THE MULTI-MODEL CONSENSUS ARE SHOWING TIGHT GROUPING THROUGH TAU
48 AND A TRANSITION TO THE NORTHWEST ENTERING THE TROUGH. HOWEVER
DIFFERENCES ARE STILL EVIDENT IN THE POSITION AND TIMING OF THE
WESTWARD TURN BEYOND TAU 48. THE FORECAST TRACK IS CLOSELY
POSITIONED TO THE GFS AND ECMWF SOLUTIONS SHOWING A REALISTIC TURN
TO THE NORTHWEST AND EVENTUAL CAPTURE BY THE TROUGH. THE JGSM AND
HWRF SOLUTIONS SHIFTED RECENTLY SHOWING BETTER AGREEMENT WITH GFS
AND ECMWF. NUMERICAL MODELS ARE STARTING TO COME INTO BETTER
AGREEMENT BUT UNCERTAINTY IS STILL HIGH AS TY 12W MAKES THE
TRANSITION TO THE NORTHWEST AND TRACKS INTO THE TROUGH LENDING LOW
CONFIDENCE TO THE FORECAST TRACK.//
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