Tropical Storm KROSA Advisory Tue Aug 13

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (KROSA) WARNING NR
027//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 11W (KROSA), LOCATED APPROXIMATELY 212 NM WEST
OF IWO TO, JAPAN, HAS TRACKED NORTHWESTWARD AT 06 KNOTS OVER THE PAST
SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS A VERY
EXPANSIVE SYSTEM SPANNING OVER 600NM WITH DEEP BUT WIDELY FRAGMENTED
CONVECTIVE BANDS SPIRALING AROUND A LARGE, RAGGED AND FULLY EXPOSED
LOW-LEVEL CIRCULATION (LLC). THE INITIAL POSITION IS PLACED WITH FAIR
CONFIDENCE BASED ON THE CENTER OF THE LLC. THE INITIAL INTENSITY OF
55KTS IS AVERAGED FROM AGENCY DVORAK ESTIMATES RANGING FROM
T3.5/45KTS TO T4.0/65 KTS AND REFLECTS THE SUSTAINED CONVECTIVE
SIGNATURE. UPPER LEVEL ANALYSIS INDICATES A MARGINAL ENVIRONMENT WITH
A LOW DIRECTLY OVER THE LLC THAT IS CAUSING SUBSIDENCE. HOWEVER,
AROUND THE LOW IS A BROAD ANTICYCLONIC OUTFLOW THAT IS PROVIDING
VENTILATION TO THE OUTER CONVECTIVE BANDS. ALONG-TRACK SST AT 30C
REMAINS CONDUCIVE. THE CYCLONE IS TRACKING ALONG THE SOUTHERN
PERIPHERY OF A BUILDING SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. OVER THE NEXT 48 HOURS, TS 11W WILL CONTINUE ON ITS CURRENT
TRACK UNDER THE STR. AFTERWARD, IT WILL TURN POLEWARD AND CREST THE
STR AXIS, MAKING LANDFALL OVER EASTERN KYUSHU AROUND SHORTLY BEFORE
TAU 72. THE MARGINAL CONDITIONS WILL SUSTAIN THE CURRENT INTENSITY AT
BEST UP TO TAU 24. AFTERWARD, INCREASING POLEWARD OUTFLOW AHEAD OF A
MID-LATITUDE TROUGH WILL PROMOTE INTENSIFICATION TO A PEAK OF 65
KNOTS BY TAU 48. NUMERICAL MODELS ARE IN GOOD AGREEMENT, LENDING HIGH
CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST.
   C. AFTER TAU 72, LAND INTERACTION, INCREASING VWS, AND COOLER SSTS
IN THE SEA OF JAPAN (SOJ) WILL COMBINE TO GRADUALLY WEAKEN THE SYSTEM
DOWN TO 50KTS AS IT EXITS INTO THE SOJ THEN DOWN TO 30KTS BY TAU 120
AS IT LANDS OVER THE SAKHALIN ISLAND. CONCURRENTLY, BY TAU 96, TS
KROSA WILL BEGIN EXTRA-TROPICAL TRANSITION AS IT ENTERS THE
BAROCLINIC ZONE, BECOMING A COLD CORE LOW BY TAU 120. NUMERICAL
MODELS SPREAD OUT TO OVER 600 NM BY TAU 120 WITH NAVGEM AND JGSM AS
NOTABLE RIGHT OUTLIERS. THERE IS OVERALL MODERATE CONFIDENCE IN THE
JTWC FORECAST TRACK THAT IS LAID JUST TO THE LEFT OF CONSENSUS TO
OFFSET THE UNLIKELY NAVGEM/JGSM SOLUTION THAT DRIVES THE VORTEX INTO
THE STR.//
NNNN
NNNN