Tropical Storm KROSA Advisory Fri Aug 09

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (KROSA) WARNING NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 11W (KROSA), LOCATED APPROXIMATELY 167 NM SOUTH-
SOUTHWEST OF IWO TO, JAPAN, HAS TRACKED NORTHEASTWARD AT 01 KNOT
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
SHOWS THE SYSTEM HAS BECOME QUASI-STATIONARY (QS) AS IT RAPIDLY
INTENSIFIED (RI) AND MAINTAINED A 14-NM EYE. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE EYE FEATURE. THE INITIAL
INTENSITY OF 100KTS IS BASED ON THE DVORAK ESTIMATES OF T5.5/102KTS
FROM PGTW AND RJTD AND REFLECT THE RI. ENVIRONMENTAL ANALYSIS
INDICATES EXCELLENT EQUATORWARD AND EASTWARD OUTFLOW (TEMPERED ONLY
BY SUBSIDENCE ALONG THE NORTHWEST SECTOR), LOW VERTICAL WIND SHEAR
(VWS) AND WARM SST (30C). TY 11W IS IN A COL BETWEEN A WEAKENED
SUBTROPICAL RIDGE (STR) TO THE EAST AND A BUILDING NEAR EQUATORIAL
RIDGE (NER) TO THE SOUTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 11W WILL REMAIN QS IN THE COL UP TO TAU 12. AFTERWARD, THE
NER WILL SLOWLY STEER IT NORTHEASTWARD. AROUND TAU 36, THE STR WILL
REBUILD AND RESUME STEERING AND DRIVE THE SYSTEM NORTH-NORTHWESTWARD
TOWARD JAPAN. INCREASING VWS AND REDUCED POLEWARD OUTFLOW WILL
GRADUALLY WEAKEN THE SYSTEM DOWN TO 70KTS BY TAU 72. THE NUMERICAL
MODELS ARE IN OVERALL GOOD AGREEMENT; HOWEVER, GIVEN THE UNCERTAINTY
 IN THE TRANSITION BETWEEN THE STEERING MECHANISMS, THERE IS LOW
CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.
   C. AFTER TAU 72, TY KROSA WILL CONTINUE TRACKING
NORTH-NORTHWESTWARD UNDER THE INFLUENCE OF THE STR. COOLING SSTS, IN
ADDITION TO THE INCREASING VWS, WILL CONTINUE TO ERODE THE SYSTEM
DOWN TO 65KTS BY TAU 120. THE NUMERICAL MODELS SPREAD OUT TO OVER
400 NM BY TAU 120, LENDING TO LOW CONFIDENCE IN THE EXTENDED PORTION
OF THE JTWC FORECAST TRACK.//
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