Tropical Storm KROSA Advisory 8月9日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (KROSA) WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 11W (KROSA), LOCATED APPROXIMATELY 169 NM SOUTH OF
IWO TO, HAS TRACKED EASTWARD AT 03 KNOTS (KTS) OVER THE PAST SIX
HOURS. THERE IS HIGH CONFIDENCE IN THE INITIAL POSITION BASED ON A
25 NM RAGGED EYE IN ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY. THE EIR ALSO REVEALS AN AREA OF WARMER CLOUD TOP
TEMPERATURES COVERING 25-50 PERCENT OF THE EYEWALL. THE INITIAL
INTENSITY OF 95 KTS FALLS BETWEEN DVORAK FIX INTENSITIES OF T5.0-5.5
(90-102 KTS) FROM PGTW AND RJTD, RESPECTIVELY. UPPER LEVEL ANALYSIS
INDICATES EXCELLENT EQUATORWARD AND EASTWARD OUTFLOW AND MODERATE
(10-20 KT) VERTICAL WIND SHEAR (VWS) IS BEING PARTIALLY OFFSET BY
SUBSIDENCE ALONG THE NORTHWEST SECTOR DUE TO AN INDUCED UPPER-LEVEL
TROUGH. SEA SURFACE TEMPERATURE (30C) IS CONDUCIVE. TY 11W IS
TRACKING SLOWLY ALONG THE NORTHERN PERIPHERY OF A NEAR EQUATORIAL
RIDGE (NER).
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 11W WILL CONTINUE ON A SLOW NORTHEASTWARD TRACK UNDER THE
INFLUENCE OF THE NER. AROUND TAU 24, A SUBTROPICAL RIDGE (STR) TO
THE NORTH WILL BEGIN TURNING THE SYSTEM NORTHWESTWARD TOWARD JAPAN.
SLIGHTLY DIMINISHED OUTFLOW, WEAK ENVIRONMENTAL SUBSIDENCE, AND
CONTINUED MARGINAL VWS WILL MAKE THE ENVIRONMENT SOMEWHAT
UNFAVORABLE AND SOME WEAKENING IS ANTICIPATED TO 70 KTS BY TAU 72.
THE TRACK GUIDANCE HAS COME INTO BETTER AGREEMENT THIS CYCLE AND THE
JTWC TRACK FORECAST HAS SHIFTED WEST WITH A WESTWARD SHIFT IN THE
CONSENSUS TRACK. GIVEN HIGH UNCERTAINTY INHERENT 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 MAKING A SLIGHT NORTHWARD TURN
AS IT BEGINS TO ROUND THE STR AXIS. AT TAU 120, THE INTENSITY IS
EXPECTED TO INCREASE SLIGHTLY AS OUTFLOW SHOULD IMPROVE WHILE
ROUNDING THE STR AXIS. IN THE EXTENDED PERIOD, NAVGEM BECOMES AN
OUTLIER AS IT TURNS THE SYSTEM NORTHEASTWARD SHORTLY AFTER TAU 72.
THE OTHER MEMBERS ALIGN FAIRLY WELL WITH THE JTWC TRACK FORECAST,
BUT BASED ON HIGH UNCERTAINTY IN THE NEAR TERM, CONFIDENCE IN THE
JTWC TRACK FORECAST REMAINS LOW FOR THIS PORTION OF THE FORECAST.//
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