Tropical Storm KROSA Advisory 8月12日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (KROSA) WARNING NR
025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 11W (KROSA), LOCATED APPROXIMATELY 711 NM
SOUTH-SOUTHEAST OF IWAKUNI, JAPAN, HAS TRACKED NORTHWESTWARD AT 06
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICTS DEEP CONVECTIVE BANDING WRAPPING INTO A BROAD LOW-
LEVEL CIRCULATION CENTER (LLCC). AN 111637Z AMSR2 37GHZ IMAGE DEPICTS
CONVECTIVE BANDING WRAPPING TIGHTLY INTO A BROAD LLCC WITH SOME
WEAKER INNER BANDING, WHICH SUPPORTS THE INITIAL POSITION WITH GOOD
CONFIDENCE. IN GENERAL, DVORAK INTENSITY ESTIMATES ARE TOO LOW
BECAUSE THE CONVECTIVE STRUCTURE IS UNUSUALLY BROAD DUE TO A
PERSISTENT, COMPACT UPPER LOW OVER THE CORE. HOWEVER, A RECENT SMAP
IMAGE (110825Z) INDICATES 55-60 KNOT WINDS DISPLACED OUTWARD FROM
THE CENTER, WHICH SUPPORTS THE CURRENT INTENSITY ASSESSMENT OF 55
KNOTS. WITH THE EXCEPTION OF THE SUBSIDENCE OVER THE LARGE CORE,
ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE WITH LOW VERTICAL WIND
SHEAR AND WARM SST (28-29C). TS 11W IS TRACKING SLOWLY ALONG THE
SOUTHERN FLANK OF A SUBTROPICAL RIDGE (STR) POSITIONED OVER JAPAN.
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 TO TRACK
NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF THE STR, HOWEVER, BY
TAU 72 THE SYSTEM SHOULD TURN POLEWARD AS IT BEGINS TO RECURVE ALONG
THE SOUTHWEST PERIPHERY OF THE STR. THE UPPER LOW OVER THE CENTER IS
FORECAST TO GRADUALLY WEAKEN AFTER TAU 24, WHICH WILL ALLOW THE
SYSTEM TO GRADUALLY INTENSIFY AS IT APPROACHES WESTERN JAPAN. AFTER
TAU 48, POLEWARD OUTFLOW SHOULD IMPROVE AS IT TAPS INTO THE DEEP
MIDLATITUDE SHORTWAVE TROUGH DIGGING OVER THE EAST CHINA SEA, WHICH
WILL ALLOW THE SYSTEM TO INTENSIFY TO TYPHOON STRENGTH. NUMERICAL
MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT WITH THE MODELS SPREAD
FROM EASTERN KYUSHU TO CENTRAL SHIKOKU. ADDITIONALLY, THE ECMWF
ENSEMBLE'S STRIKE PROBABILITY PRODUCT IS ALSO INDICATING HIGH
PROBABILITY OF THE SYSTEM TRACKING IN THIS SAME REGION. THEREFORE,
THERE IS HIGH CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.
   C. AFTER TAU 72, TS KROSA WILL TRACK NORTHWARD OVER WESTERN
HONSHU THROUGH TAU 96. TS 11W REMAINS A VERY LARGE, 7-8 DEGREE
DIAMETER, SYSTEM AND IS EXPECTED TO REMAIN VERY LARGE THROUGH TAU 96
WITH AN EXPANSIVE AREA OF GALE-FORCE WINDS. DUE TO THE COMPLEXITY OF
THE UPPER-LEVEL FLOW OVER THE SYSTEM, THERE IS SOME UNCERTAINTY IN
THE JTWC INTENSITY FORECAST. TS 11W IS FORECAST TO BEGIN EXTRA-
TROPICAL TRANSITION (ETT) OVER THE EAST SEA BY TAU 96. IT WILL
COMPLETE ETT BY TAU 120 AS IT ACCELERATES NORTH-NORTHEASTWARD
RETAINING AN EXPANSIVE AREA OF GALE-FORCE WINDS WHICH COULD IMPACT
NORTHERN JAPAN. OVERALL, THERE IS HIGH CONFIDENCE IN THE JTWC
FORECAST TRACK.//
NNNN
NNNN