Tropical Storm KROSA Advisory 09.08.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (KROSA) WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 11W (KROSA), LOCATED APPROXIMATELY 168 NM SOUTH OF
IWO TO, HAS TRACKED EASTWARD AT 01 KNOT (KT) OVER THE PAST SIX
HOURS. THERE IS HIGH CONFIDENCE IN THE INITIAL POSITION BASED ON A
36 NM RAGGED EYE IN ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI).
ENHANCED INFRARED IMAGERY REVEALS AN AREA OF WARMER CLOUD TOP
TEMPERATURES OVER ABOUT 50 PERCENT OF THE EYEWALL. THE INITIAL
INTENSITY OF 90 KTS IS CONSISTENT WITH A T5.0 (90 KTS) PGTW DVORAK
FIX CURRENT INTENSITY ESTIMATE. THE ENVIRONMENT IS FAIRLY SUPPORTIVE
WITH EXCELLENT EQUATORWARD AND EASTWARD OUTFLOW, MODERATE (10-20 KT)
VERTICAL WIND SHEAR (VWS), AND WARM (29-30 CELSIUS) SEA SURFACE
TEMPERATURE BEING PARTIALLY OFFSET BY SUBSIDENCE ALONG THE NORTHERN
SECTOR DUE TO AN INDUCED UPPER-LEVEL TROUGH. TY 11W IS QUASI-
STATIONARY IN A COMPLEX STEERING ENVIRONMENT WITH A NEAR EQUATORIAL
RIDGE (NER) TO THE SOUTH AND A 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. IN THE NEXT 72 HOURS, PRIMARY STEERING FOR TY 11W WILL
GRADUALLY TRANSITION TO THE STR AND THE TRACK WILL SLOWLY SHIFT
NORTHWESTWARD TOWARD JAPAN, PASSING IWO TO AROUND TAU 36. SLIGHTLY
DIMINISHED OUTFLOW, WEAK ENVIRONMENTAL SUBSIDENCE, AND CONTINUED
MARGINAL VWS WILL MAKE THE ENVIRONMENT SOMEWHAT UNFAVORABLE AND
WEAKENING TO 70 KTS IS ANTICIPATED BY TAU 72. MODEL TRACK GUIDANCE
GENERALLY AGREES WITH THE JTWC FORECAST TRACK FORECAST FOR THIS
PORTION OF THE FORECAST. HOWEVER, GIVEN HIGH UNCERTAINTY WHENEVER
THERE IS A TRANSITION BETWEEN STEERING MECHANISMS, THERE IS LOW
CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.
   C. AFTER TAU 72, TY 11W WILL CONTINUE TRACKING NORTHWESTWARD
UNDER THE INFLUENCE OF THE STR UNTIL TAU 96 WHEN IT SHIFTS
MORE NORTHWARD AS IT BEGINS TO ROUND THE STR AXIS. THE SLIGHT
INCREASE IN INTENSITY AT TAU 120, REFLECTS THE POSSIBILITY THAT
IMPROVED OUTFLOW COULD OCCUR AS TY 11W ROUNDS THE STR AXIS. IN THE
EXTENDED PERIOD, NAVGEM BECOMES AN OBVIOUS EASTERN OUTLIER AND THE
JTWC TRACK FORECAST IS PLACED JUST WEST OF THE CONSENSUS TRACK TO
OFFSET THE OUTLIER. BASED ON HIGH UNCERTAINTY IN THE NEAR TERM
FORECAST, CONFIDENCE IN THE JTWC TRACK FORECAST REMAINS LOW IN THE
EXTENDED PERIOD.//
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