Tropical Storm LIONROCK Advisory Tue Aug 23

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (LIONROCK) WARNING
NR 23//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 12W (LIONROCK), LOCATED APPROXIMATELY 333 NM
EAST OF KADENA AB, HAS TRACKED SOUTH-SOUTHWESTWARD AT 06 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
DEPICTS A CENTRAL DENSE OVERCAST FEATURE OBSCURING A CONSOLIDATING
LOW-LEVEL CIRCULATION CENTER (LLCC). A 231216Z METOP-B 89GHZ IMAGE
SHOWS TIGHTLY-CURVED BANDING WRAPPING INTO A WELL-DEFINED CENTER,
WHICH PROVIDES GOOD CONFIDENCE IN THE CURRENT POSITION AND RECENT
TRACK MOTION. THE CURRENT INTENSITY IS ASSSESSED AT 60 KNOTS BASED
ON AN AVERAGE OF DVORAK INTENSITY ESTIMATES RANGING FROM T3.5
(55 KNOTS) TO T4.0 (65 KNOTS). UPPER-LEVEL ANALYSIS INDICATES
ENHANCED POLEWARD OUTFLOW, AIDED BY A SHARP SHORTWAVE TROUGH OVER
CENTRAL JAPAN, AND GOOD EQUATORWARD OUTFLOW. TS 12W IS LOCATED
WITHIN A WEAK STEERING ENVIRONMENT BETWEEN THE DOMINANT WESTERN
SUBTROPICAL RIDGE (STR) AND EASTERN STR, AND IS DRIFTING GENERALLY
SOUTHWARD.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 12W WILL REMAIN TRAPPED WITHIN THIS COMPETING STEERING
ENVIRONMENT WHILE DRIFTING SOUTH-SOUTHWESTWARD TO WESTWARD THROUGH
TAU 48. THE WESTERN STR IS EXPECTED TO REMAIN ENTRENCHED OVER THE
EAST CHINA SEA AND OKINAWA PROVIDING A BARRIER TO ANY SIGNIFICANT
WESTWARD MOVEMENT. IN FACT, ALL DYNAMIC MODELS SHOW A SLOW, QUASI-
STATIONARY MOTION THROUGH TAU 72 AND SHOW NO POSITION WEST OF 130E
LONGITUDE. TS 12W IS FORECAST TO GRADUALLY INTENSIFY UNDER FAVORABLE
CONDITIONS TO A PEAK OF 75 KNOTS BY TAU 36.
   C. IN THE EXTENDED TAUS, THE NEAR-EQUATORIAL RIDGE (NER) IS
FORECAST TO BUILD TO THE SOUTH OF TS 12W WHILE A DEEP MIDLATITUDE
TROUGH DEEPENS OVER JAPAN, ALLOWING THE SYSTEM TO ACCELERATE
NORTHEASTWARD. WHILE THE MODEL VORTEX TRACKERS DIFFER ON THE EXACT
NATURE OF THE TURN EASTWARD, THE TRACKERS ALL SHOW AN EASTWARD TURN
WITH DIFFERENT TRACK SPEEDS. DUE TO THE COMPLEXITY OF THE STEERING
ENVIRONMENT AND UNCERTAINTY IN THE EASTWARD TURN, THERE IS LOW
CONFIDENCE IN JTWC FORECAST TRACK.//
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