Tropical Storm LIONROCK Advisory Sat Aug 27

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (LIONROCK) WARNING NR 34//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 12W (LIONROCK), LOCATED APPROXIMATELY 279 NM SOUTHEAST OF
KADENA AB, OKINAWA, JAPAN, HAS TRACKED EASTWARD AT 04 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS
A SYSTEM WITH A WELL-DEFINED 6-NM EYE AND EXCELLENT DUAL OUTFLOW.
BASED ON THE EYE-MOVEMENT, THE SYSTEM HAS BEEN QUASI-STATIONARY AND
HAS, OVERALL, MAINTAINED CONVECTIVE DEPTH. THE INITIAL POSITION IS
BASED ON THE EYE FEATURE IN THE MSI ANIMATION WITH HIGH CONFIDENCE.
THE INITIAL INTENSITY OF 105 KNOTS IS BASED ON CONGRUENT DVORAK
ESTIMATES FROM PGTW, KNES, AND RJTD. UPPER LEVEL ANALYSIS INDICATES
TY 12W IS UNDER A RIDGE AXIS IN AN AREA OF LOW (05-10 KNOT) VERTICAL
WIND SHEAR (VWS). THE CYCLONE IS IN A WEAK STEERING ENVIRONMENT
BETWEEN TWO REFLECTIONS OF THE  SUBTROPICAL RIDGE (STR) - ONE TO THE
NORTHWEST AND THE OTHER TO THE EAST-SOUTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY FROM THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 12W WILL BEGIN A SLOW NORTHEAST POLEWARD TRACK AS THE STR TO
THE EAST-SOUTHEAST ASSUMES PRIMARY STEERING. ALTHOUGH SEA SURFACE
TEMPERATURES (SSTS) AT 30 DEGREES CELSIUS AND OUTFLOW REMAIN ROBUST,
INCREASING VWS WILL OFFSET THESE FAVORABLE DYNAMICS AND RESULT IN AN
INTENSITY STAGNATION IN THE NEAR TERM. HOWEVER, BY TAU 36, INCREASED
POLEWARD OUTFLOW DUE TO THE INITIAL EXPOSURE TO THE STRONG WESTERLIES
ASSOCIATED WITH AN APPROACHING MID-LATITUDE TROUGH WILL CAUSE A SMALL
REBOUND IN THE INTENSITY TO 110 KNOTS.
   C. IN THE EXTENDED TAUS, TYPHOON LIONROCK WILL BEGIN TO TRACK MORE
NORTHWARD 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 40 KNOTS BY TAU 120. AT TAU 96, 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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