Tropical Storm FENGSHEN Advisory Tue Sep 09

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (FENGSHEN) WARNING
NR 06//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 13W (FENGSHEN), LOCATED APPROXIMATELY 350 NM
SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN, HAS TRACKED EAST-NORTHEASTWARD
AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY (MSI) DEPICTS A SYMMETRIC SIGNATURE WITH TIGHTLY-
CURVED BANDING OVER THE NORTHERN PERIPHERY WRAPPING INTO A WELL-
DEFINED LOW LEVEL CIRCULATION CENTER (LLCC). A 080431Z NOAA-19
MICROWAVE IMAGE ALSO REVEALS A LARGE ROUND MICROWAVE EYE WITH THE
BULK OF THE DEEP CONVECTIVE BANDING OVER THE NORTHERN SEMI-CIRCLE
WRAPPING INTO THE LLCC. THE CURRENT POSITION IS BASED ON THE MSI AND
AFOREMENTIONED MICROWAVE IMAGE WITH HIGH CONFIDENCE. THE INITIAL
INTENSITY OF 55 KNOTS IS BASED ON MATCHING DVORAK INTENSITY
ESTIMATES FROM ALL REPORTING AGENCIES. UPPER-LEVEL ANALYSIS
INDICATES TS FENGSHEN CONTINUES TO HAVE EXCELLENT POLEWARD OUTFLOW
OFFSETTING THE MODERATE TO HIGH LEVELS (15 TO 25 KNOTS) OF VERTICAL
WIND SHEAR (VWS). TS 13W CONTINUES TO TRACK ALONG THE NORTHWESTERN
PERIPHERY OF A DEEP LAYERED SUBTROPICAL RIDGE (STR) TO THE SOUTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 13W IS EXPECTED TO TRACK NORTHEASTWARD ALONG THE STR
THROUGHOUT THE FORECAST PERIOD. DESPITE THE SUBSIDENCE ALONG THE
WESTERN PERIPHERY AND INCREASING VWS, FAVORABLE SEA SURFACE
TEMPERATURES AND STRONG POLEWARD OUTFLOW WILL ALLOW TS 13W TO
INTENSIFY OVER THE NEXT 24 HOURS, LEADING TO A PEAK INTENSITY OF 65
KNOTS. INTERACTION WITH THE BAROCLINIC ZONE AROUND TAU 24 WILL BEGIN
THE EXTRA-TROPICAL TRANSITION PROCESS AND COMPLETE ITS
TRANSFORMATION INTO A STORM-FORCE COLD-CORE LOW BY THE END OF THE
FORECAST. ADDITIONALLY, THE INCREASING INTERACTION WITH THE MID-
LATITUDE WESTERLIES, AS THE SYSTEM BECOMES EMBEDDED, WILL LEAD TO
FASTER TRACK SPEEDS IN THE LATER TAUS. DYNAMIC MODEL GUIDANCE
REMAINS IN GOOD AGREEMENT, LENDING HIGH CONFIDENCE IN THE JTWC
FORECAST.//
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