Tropical Storm LIONROCK Advisory Mi, 24.08.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (LIONROCK) WARNING
NR 25//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 12W (LIONROCK), LOCATED APPROXIMATELY 274 NM EAST-
SOUTHEAST OF KADENA AB, HAS TRACKED SOUTHWESTWARD AT 08 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
DEPICTS A WELL DEFINED EYE FEATURE WITH A SPIRAL BANDING WRAPPING
INTO THE LOW LEVEL CIRCULATION CENTER. THE POSITION IS BASED ON
SATELLITE FIXES FROM PGTW WITH GOOD CONFIDENCE. THE INITIAL
INTENSITY IS ASSESSED AT 75 KNOTS AND IS BASED ON OBJECTIVE DVORAK
ESTIMATES FROM ALL AGENCIES REPORTING T4.0 (75 KNOTS). UPPER-LEVEL
ANALYSIS INDICATES THE PRESENCE OF RADIAL OUTFLOW THAT HAS IMPROVED
SOME IN THE LAST SIX HOURS DUE TO OPENING DISTANCE FROM THE
ANTICYCLONE POSITIONED SOUTH OF THE SYSTEM. VERTICAL WIND SHEAR
VALUES ARE CURRENTLY VERY FAVORABLE DIRECTLY OVER THE SYSTEM. TY 12W
IS LOCATED WITHIN A WEAK STEERING ENVIRONMENT BETWEEN THE DOMINANT
WESTERN SUBTROPICAL RIDGE (STR) AND EASTERN STR, AND IS DRIFTING
GENERALLY SOUTHWESTWARD.
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 SOUTHWESTWARD THROUGH
TAU 36. BEYOND TAU 36 THE EASTERN STEERING RIDGE WILL BUILD IN FROM
THE SOUTH AND SHIFT THE TRACK ABRUPTLY TO THE NORTHEAST. TS 12W IS
FORECAST TO GRADUALLY INTENSIFY UNDER
FAVORABLE CONDITIONS TO A PEAK OF 85 KNOTS BY TAU 24. HOWEVER,
OCEANIC HEAT CONTENT IS LOW AND UPWELLING DUE TO A PERIOD OF QUASI-
STATIONARY MOTION AS THE STEERING RIDGES SHIFT WILL PREVENT FURTHER
INTENSIFICATION.
   C. IN THE EXTENDED TAUS, THE NEAR-EQUATORIAL RIDGE WILL KEEP TY
12W TRACKING NORTHEASTWARD AS A DEEP MIDLATITUDE
TROUGH DEEPENS OVER JAPAN, PROVIDING AN EXHAUST MECHANISM ALLOWING
THE SYSTEM TO BRIEFLY INTENSIFY AS IT MOVES INTO WARMER WATERS.
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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