Tropical Storm LIONROCK Advisory Mon Aug 29

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (LIONROCK) WARNING NR 42//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 12W (LIONROCK), LOCATED APPROXIMATELY 465 NM SOUTH-
SOUTHWEST OF YOKOSUKA, JAPAN, HAS TRACKED NORTHEASTWARD AT 19
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY AND RECENT MICROWAVE IMAGERY DEPICT A COMPACT, STRENGTHENING
CORE (APPROXIMATELY 60-NM DIAMETER EYEWALL) WITH A 20-NM ROUND EYE,
WHICH PROVIDES HIGH CONFIDENCE IN THE CURRENT POSITION AND RECENT
TRACK ACCELERATION TO THE NORTHEAST. ANIMATED WATER VAPOR IMAGERY
INDICATES IMPROVED, RADIAL OUTFLOW, WHICH HAS FUELED THE RECENT
INTENSIFICATION TREND TO THE CURRENT INTENSITY OF 115 KNOTS. ALL
AGENCIES ARE REPORTING A DVORAK INTENSITY ESTIMATE OF T6.0 (115
KNOTS) AND THE MOST RECENT SATCON ESTIMATE IS AT 122 KNOTS AT
28/0600Z. TY 12W IS CURRENTLY TRACKING ALONG A POLEWARD EXTENSION OF
THE NEAR-EQUATORIAL RIDGE (NER) POSITIONED TO THE EAST. RECENT 500MB
ANALYSES DEPICT A DEEPENING LOW OVER THE KOREAN PENINSULA AND
ASSOCIATED MAJOR SHORTWAVE TROUGH DIGGING INTO THE EAST CHINA SEA
AND WESTERN JAPAN. OVERALL, THE DYNAMIC MODELS HAVE DONE AN
EXCELLENT JOB IN FORECASTING THE DEVELOPMENT OF THIS EXPANSIVE,
STRONG LOW AND MAJOR SHORTWAVE TROUGH, AND ARE CURRENTLY ACCURATELY
INITIALIZING THIS SYNOPIC FEATURE, WHICH WILL BECOME THE DOMINANT
INFLUENCE ON TY 12W'S TRACK AND INTENSITY AFTER TAU 24.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE. WIND RADII HAVE BEEN ADJUSTED BASED ON
A BULLS-EYE ASCAT IMAGE AT 280059Z. THE FORECAST TRACK AND CPA TO
YOKOSUKA REMAIN HIGHLY CONSISTENT WITH THE PREVIOUS JTWC FORECAST
TRACK.
   B. TY 12W WILL CONTINUE TO TRACK NORTHEASTWARD ALONG THE
NORTHWEST PERIPHERY OF THE NER THROUGH TAU 24. AFTER TAU 24, THE
AFOREMENTIONED UPPER LOW AND MAJOR SHORTWAVE TROUGH ARE FORECAST TO
REMAIN ENTRENCHED OVER THE EAST SEA AND JAPAN WITH THE PRIMARY
STEERING RIDGE POSITIONED OVER SAKHALIN ISLAND AND THE SEA OF
OKHOTSK, EXTENDING SOUTHEASTWARD ACROSS THE KURIL ISLANDS. TY 12W IS
FORECAST TO RE-CURVE WITHIN THE ENHANCED FLOW BETWEEN THESE TWO
SYNOPTIC FEATURES. WITH A FEW EXCEPTIONS, THE DYNAMIC MODEL TRACKERS
HAVE COME INTO BETTER AGREEMENT OVER THE PAST DAY AND GENERALLY SHOW
A TRACK OVER NORTHERN HONSHU THEN A RAPID NORTHWESTWARD TRACK ACROSS
THE EAST SEA. NAVGEM REMAINS ERRATIC AND THUS UNRELIABLE, AND NOW
SHOWS A QUASI-STATIONARY TRACK EAST OF HONSHU. GFDN AND COAMPS-TC
CONTINUE TO INDICATE AN UNREALISTIC EASTWARD TRACK AND ARE BEING
DISCOUNTED. DESPITE THE IMPROVED AGREEMENT IN THE BULK OF THE
GUIDANCE AND AGENCY FORECASTS, THERE REMAINS SIGNIFICANT UNCERTAINTY
IN THE EXACT RE-CURVE POINT AFTER TAU 36 AND TRACK SPEEDS AFTER TAU
48. TY LIONROCK HAS RECENTLY DISPLAYED MAJOR DIURNAL VARIATIONS IN
CONVECTIVE STRUCTURE AND PEAK INTENSITY, AND WILL LIKELY CONTINUE
THIS TREND THROUGH TAU 24. THE CURRENT PEAK INTENSITY IS FORECAST TO
BE 115 KNOTS, HOWEVER, IT'S POSSIBLE THAT THE SYSTEM MAY SPIKE
HIGHER WITHIN THE NEXT 24 HOURS. AFTER TAU 24, TY 12W IS FORECAST TO
GRADUALLY WEAKEN DUE TO COOLER SST, INCREASING VWS AND INTERACTION
WITH LAND. ADDITIONALLY, TY 12W SHOULD BEGIN EXTRA-TROPICAL
TRANSITION (ETT) JUST AFTER TAU 48, AS IT BEGINS TO INTERACT WITH
THE MAJOR SHORTWAVE TROUGH.
   C. AFTER CROSSING THE MOUNTAINOUS TERRAIN OF NORTHERN HONSHU, A
MUCH WEAKER SYSTEM IS EXPECTED TO RE-EMERGE IN THE EAST SEA AND TO
ACCELERATE NORTHWESTWARD WITHIN THE ENHANCED FLOW BETWEEN THE STRONG
BAROCLINIC LOW AND THE STEERING RIDGE. TY 12W IS FORECAST TO
COMPLETE ETT NEAR OR JUST AFTER TAU 72 AS IT BECOMES EMBEDDED WITHIN
THE BAROCLINIC LOW. DUE TO THE UNCERTAINTY IN THE RE-CURVE POINT,
WHICH IS TIED TO UNCERTAINTY IN THE DEPTH AND ORIENTATION OF THE
STRONG UPPER LOW, AND MAJOR DIFFERENCES IN MODEL GUIDANCE TRACK
SPEED, THERE IS LOW CONFIDENCE IN THE FORECAST TRACK.//
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