Tropical Storm LIONROCK Advisory Fri Aug 26

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (LIONROCK) WARNING NR 35//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 12W (LIONROCK), LOCATED APPROXIMATELY 307 NM SOUTHEAST OF
KADENA AB, OKINAWA, JAPAN, HAS TRACKED EAST-NORTHEASTWARD AT 09 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY SHOWS THE SYSTEM RETAINED A WELL-DEFINED 12-NM EYE AND
EXCELLENT DUAL OUTFLOW. HOWEVER, SUBSIDENCE HAS BEGUN TO ERODE SOME
OF THE CONVECTION ALONG THE NORTHERN PERIPHERIES. THE INITIAL POSITION IS
BASED ON THE EYE FEATURE IN THE EIR ANIMATION, WHICH LINES UP WELL
WITH A LOW REFLECTIVITY MICROWAVE EYE IN THE 260935Z 37GHZ SSMIS,
WITH HIGH CONFIDENCE. THE INITIAL INTENSITY OF 95 KNOTS IS BASED ON
AN OVERALL ASSESSMENT OF AGENCY AND OBJECTIVE DVORAK ESTIMATES AND
REFLECTS THE WEAKENED STATE OF THE CYCLONE. UPPER LEVEL ANALYSIS
INDICATES TY 12W IS UNDER A RIDGE AXIS IN AN AREA OF LOW TO MODERATE
(10-15 KNOT) VERTICAL WIND SHEAR (VWS). A TROUGH TO THE NORTH IS
CAUSING THE AFOREMENTIONED SUBSIDENCE. THE CYCLONE IS NOW BEING
STEERED BY THE SUBTROPICAL RIDGE (STR) TO THE SOUTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY FROM THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 12W WILL TRACK MORE NORTHEASTWARD AS THE STR TO THE
SOUTHEAST BOLSTERS UP PRIMARY STEERING. ALTHOUGH SEA SURFACE
TEMPERATURES (SSTS) AT 30 DEGREES CELSIUS AND OUTFLOW REMAIN ROBUST,
INCREASING VWS AND THE SUBSIDENT EFFECT OF THE TROUGH WILL PREVAIL
AND RESULT IN FURTHER WEAKENING IN THE VERY NEAR TERM. HOWEVER, BY
TAU 24, INCREASED POLEWARD OUTFLOW DUE TO THE INITIAL EXPOSURE TO THE
STRONG WESTERLIES
ASSOCIATED WITH THE PREVAILING WESTERLIES WILL CAUSE A SMALL REBOUND
IN THE INTENSITY TO 100 KNOTS.
   C. IN THE EXTENDED TAUS, TYPHOON LIONROCK WILL BEGIN TO TRACK
NORTHWESTWARD AS ANOTHER REFLECTION OF THE STR ANCHORED AT 45N JUST
SOUTH OF KAMCHATKA BUILDS AND ASSUMES STEERING. INCREASING VWS, COOLING
SSTS, AND TRACK ACROSS THE ISLAND OF HONSHU WILL GRADUALLY WEAKEN THE
CYCLONE DOWN TO 35 KNOTS BY TAU 120. AT TAU 72, THE CYCLONE WILL
ENTER THE BAROCLINIC ZONE AND BEGIN EXTRA-TROPICAL TRANSITION AND
BECOME A COLD-CORE LOW IN THE SEA OF JAPAN BY END OF FORECAST.
NUMERIC GUIDANCE REMAINS WIDELY SPREAD ACROSS THE MODEL ENVELOPE AND
IN THE LATERAL SPEEDS OF EACH SOLUTION. IN VIEW OF THESE, THE
CONFIDENCE IN THE JTWC TRACK FORECAST REMAINS LOW.//
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