Tropical Storm IN-FA Advisory Seg, 23-11

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W (IN-FA) WARNING NR 27//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 27W (IN-FA), LOCATED APPROXIMATELY 734 NM SOUTHWEST
OF IWO TO, JAPAN HAS TRACKED NORTH-NORTHWESTWARD AT 04 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY DEPICTS A LARGE CENTRAL DENSE OVERCAST FEATURE OBSCURING THE
LOW LEVEL CIRCULATION CENTER. THE SYSTEM CONTINUES TO BE ELONGATED
TO THE NORTHEAST ALONG THE LEADING EDGE OF AN APPROACHING MID-
LATITUDE TROUGH. THE WATER VAPOR LOOP SHOWS A STRONG POLEWARD
OUTFLOW CHANNEL THAT IS ENHANCED BY THE MID-LATITUDE WESTERLY FLOW
AND IS SUSTAINING THE CENTRAL CONVECTION. THE CURRENT INTENSITY IS
MAINTAINED AT 90 KNOTS BASED ON THE CONVECTIVE STRUCTURE AND IS
SUPPORTED BY AGENCY DVORAK INTENSITY ESTIMATES OF T5.0 (90 KNOTS)
AND A SATCON INTENSITY ESTIMATE OF 87 KNOTS. THE INITIAL POSITION IS
BASED ON THE EIR LOOP WITH FAIR CONFIDENCE. SOUTHWESTERLY VERTICAL
WIND SHEAR (VWS) REMAINS MODERATE AT 15 TO 20 KNOTS. TY 27W HAS
CONTINUED TO SLOW AS IT APPROACHES THE DEEP LAYERED SUB-TROPICAL
RIDGE (STR) AXIS.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 27W WILL CONTINUE TO ROUND THE STR AXIS OVER THE NEXT 12 TO
24 HOURS. INCREASING INTERACTION WITH THE APPROACHING MID-LATITUDE
TROUGH WILL LEAD TO A NORTHEASTWARD ACCELERATION INTO THE BAROCLINIC
ZONE. ENVIRONMENTAL CONDITIONS WILL CONTINUE TO DETERIORATE AS VWS
RAPIDLY INCREASES DUE TO THE STRONG WESTERLY WINDS FROM THE
APPROACHING TROUGH. TY IN-FA WILL BEGIN EXTRA- TROPICAL TRANSITION
(ETT) NEAR TAU 72.
   C. IN THE EXTENDED FORECAST, TY 27W WILL CONTINUE TO ACCELERATE
NORTHEASTWARD ALONG THE NORTHWESTERN PERIPHERY OF THE STEERING STR.
TY 27W WILL CONTINUE ETT AS IT EMBEDS DEEPER INTO THE MID-LATITUDE
WESTERLY FLOW AND WILL COMPLETE ETT BY THE END OF THE FORECAST
PERIOD. DYNAMIC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT, LEADING TO
HIGH CONFIDENCE IN THE JTWC TRACK FORECAST.//
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