Tropical Storm VONGFONG Advisory 09 Οκτ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 19W (VONGFONG) WARNING
NR 25//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 19W (VONGFONG), LOCATED APPROXIMATELY 484 NM
SOUTH-SOUTHEAST OF KADENA AB, OKINAWA, JAPAN HAS TRACKED WEST-
NORTHWESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED (EIR) SATELLITE IMAGERY SHOWS THE SYSTEM HAS MAINTAINED A
ROUND 23-NM EYE WITH CONVECTIVE BANDING WRAPPING INTO THE CENTER.
THE CURRENT POSITION IS BASED ON THE EYE FEATURE ON THE EIR
ANIMATION WITH HIGH CONFIDENCE. THE INITIAL INTENSITY OF 145 KNOTS
IS BASED ON AN OVERALL ASSESSMENT OF DVORAK CURRENT INTENSITY
ESTIMATES RANGING FROM T7.0 TO T7.5 (140 TO 155 KNOTS). UPPER-LEVEL
ANALYSIS INDICATES EXCELLENT RADIAL OUTFLOW, ENHANCED BY A TUTT CELL
TO THE EAST, AS EVIDENT ON THE WATER VAPOR IMAGERY. STY 19W IS
CURRENTLY TRACKING ALONG THE SOUTHWEST PERIPHERY OF THE SUBTROPICAL
RIDGE (STR).
3. FORECAST REASONING.
   A. THE TRACK FORECAST HAS CHANGED FROM THE PREVIOUS PROGNOSTIC
REASONING MESSAGE, SHIFTING THE SYSTEM WESTWARD. SEE PARA 3.B. FOR
FURTHER DETAILS.
   B. STY 19W IS EXPECTED TO TRACK WEST-NORTHWESTWARD TO
NORTHWESTWARD OVER NEXT 12 TO 24 HOURS AS IT ROUNDS THE SOUTHWEST
PERIPHERY OF THE STR. AFTER TAU 24, A MIDLATITUDE SHORTWAVE TROUGH
IS FORECAST TO DIG OVER WESTERN JAPAN MODIFYING THE STR, WHICH WILL
SHIFT STY 19W POLEWARD THROUGH TAU 48. AVAILABLE MODEL GUIDANCE HAS
SLIGHTLY IMPROVED, BUT STILL INDICATES A 230-NM SPREAD AT TAU 72.
THE JGSM, JENS AND ECMWF TRACKERS INDICATE A MORE NORTH-
NORTHEASTWARD TRACK WHICH IS UNLIKELY DUE TO THE CURRENT LOCATION
AND ANALYSIS OF THE AFOREMENTIONED SHORTWAVE TROUGH. THEREFORE, JTWC
TRACK FORECAST FAVORS THE GENERALLY NORTHWARD TRACK THROUGH TAU 72
UNDER THE COMPLEX STEERING ENVIRONMENT OF A FAST MOVING WAVE-TRAIN
UPPER-LEVEL PATTERN.
   C. AFTER TAU 72, STY IS EXPECTED TO TRACK ALONG THE NORTHWESTERN
PERIPHERY OF THE ORIENTED STR. ANOTHER MIDLATITUDE TROUGH PASSING
OVER THE KOREA PENINSULA WILL WEAKEN THE STR AND ALLOW THE SYSTEM RE-
CURVE NORTHEASTWARD AS IT BEGINS TO INTERACT WITH THE MIDLATITUDE
WESTERLIES AND BEGIN EXTRA-TROPICAL TRANSITION . INCREASING VERTICAL
WIND SHEAR NORTH OF 28N LATITUDE WILL SERVE TO WEAKEN THE SYSTEM.
DUE TO THE COMPLEX STEERING ENVIRONMENT AND VARYING DEGREES OF
MIDLATITUDE TROUGH INTERACTION, THE JTWC TRACK FORECAST CONFIDENCE
LEVEL REMAINS LOW.//
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