Tropical Storm GUCHOL Advisory Sat Jun 16

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 05W (GUCHOL) WARNING NR 21//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 05W (GUCHOL), LOCATED APPROXIMATELY 565 NM EAST OF
MANILA, PHILIPPINES, HAS TRACKED NORTH-NORTHWESTWARD AT 09 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) DEPICTS TIGHTLY CURVED CONVECTIVE BANDING WRAPPING INTO THE
LOW LEVEL CIRCULATION CENTER WITH A STRONG BANDING FEATURE OVER THE
SOUTHEASTERN QUADRANT. A 160048Z AMSU MICROWAVE IMAGE ALSO DEPICTS
THE TIGHTLY WRAPPED DEEP CONVECTION. THERE IS GOOD CONFIDENCE IN THE
INITIAL POSITION, WHICH WAS BASED ON THE MSI AND AMSU IMAGERY. THE
INITIAL INTENSITY WAS BASED ON THE PGTW AND KNES DVORAK ESTIMATES OF
100 KNOTS. UPPER LEVEL ANALYSIS INDICATES A TROPICAL UPPER
TROPOSPHERIC TROUGH (TUTT) CELL THAT IS MOVING TO THE NORTH OF THE
SYSTEM AND LIMITING OUTFLOW ALONG THE NORTHERN PERIPHERY.
EQUATORWARD OUTFLOW REMAINS STRONG. TY 05W IS CURRENTLY TRACKING
ALONG THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 05W IS EXPECTED TO CONTINUE TRACKING POLEWARD THROUGH TAU
48. A MID-LATITUDE TROUGH, CURRENTLY DIGGING OVER CHINA, IS FORECAST
TO CONTINUE TO WEAKEN THE STEERING RIDGE TO ALLOW TY 05W TO ROUND
THE NORTHWESTERN PERIPHERY OF THE STR AND BEGIN TO INTERACT WITH THE
MID-LATITUDE WESTERLIES BY TAU 72. TY 05W SHOULD CONTINUE TO
INTENSIFY AS IT TRACKS OVER HIGH OCEAN HEAT CONTENT AND AS OUTFLOW
IMPROVES INTO THE MID-LATITUDE TROUGH. MODEL GUIDANCE IS IN VERY
TIGHT AGREEMENT THROUGH TAU 72. THEREFORE, THERE IS HIGH CONFIDENCE
IN THE INITIAL PORTION OF THE JTWC FORECAST.
   C. IN THE EXTENDED FORECAST, TY 05W SHOULD BECOME FULLY ABSORBED
IN THE BAROCLINIC ZONE BY TAU 96, NEAR TOKYO, JAPAN. TY 05W IS
EXPECTED TO ENCOUNTER HIGH VERTICAL WIND SHEAR (VWS) AND COOLER SST
TO THE NORTH OF OKINAWA AND SHOULD ACCELERATE AS IT BEGINS
EXTRATROPICAL TRANSITION (ETT). THE SYSTEM WILL WEAKEN RAPIDLY DUE
TO THE HIGH VWS AND INTERACTION WITH LAND BUT SHOULD MAINTAIN GALE-
FORCE WINDS AS AN EXTRATROPICAL LOW. NUMERICAL MODELS DIVERGE AROUND
TAU 96 WITH GFS AND GFDN TRACKING THE SYSTEM FARTHER POLEWARD ACROSS
JAPAN. THIS SCENARIO SEEMS UNLIKELY AS THE JET IS FORECAST TO BE
OVER JAPAN BY THAT TIME. THE JTWC FORECAST IS MORE IN AGREEMENT WITH
THE ECMWF, NOGAPS, AND EGRR MODELS THAT TRACK TY 05W OVER THE KANTO
PLAIN REGION AND SOUTH OF JAPAN. THE JTWC FORECAST IS SLIGHTLY
FASTER AND EAST OF MODEL CONSENSUS TO ACCOUNT FOR THE MODELS
TRENDING EASTWARD AND THE MODEL SLOW BIAS. THERE IS SOME UNCERTAINTY
IN THE EXTENDED FORECAST BASED ON THE SPLIT GROUPING, BUT THE JTWC
TRACK FORECAST HAS FAIR CONFIDENCE BASED ON THE IMPROVED MODEL
PACKING AND TRENDS.//
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