Tropical Storm VONGFONG Advisory Çar, 08.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 19W (VONGFONG) WARNING
NR 21//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 19W (VONGFONG), LOCATED APPROXIMATELY 612 NM
SOUTH-SOUTHEAST OF KADENA AB, OKINAWA, HAS TRACKED WEST-
NORTHWESTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED SATELLITE IMAGERY (EIR) REVEALS STY 19W HAS CONTINUED TO
INTENSIFY WITH AN INTENSE RING OF SYMMETRIC CONVECTION SURROUNDING A
DEFINED 17 NM EYE AND MULTIPLE CONVECTIVE BANDS IN THE OUTER
PERIPHERIES FEEDING IN THE SYSTEM. A 071751Z SSMI IMAGE ALSO DEPICTS
AN INTENSE, CONSOLIDATED STRUCTURE WITH IMPROVED BANDING FEATURES,
SPECIFICALLY IN THE NORTHEAST AND SOUTHWEST QUADRANTS. THERE IS HIGH
CONFIDENCE IN THE INITIAL POSITION BASED ON THE DEFINED EYE FEATURE
IN THE EIR LOOP. THE INITIAL INTENSITY HAS INCREASED TO 155 KNOTS
BASED ON DVORAK INTENSITY ESTIMATES FROM PGTW AND RJTD THAT HAVE
INCREASED TO T7.5 (155 KNOTS) AND THE IMPROVED STRUCTURE OBSERVED IN
THE AFOREMENTIONED SATELLITE IMAGERY. UPPER-LEVEL ANALYSIS INDICATES
LOW VERTICAL WIND SHEAR (VWS) AND STRONG POLEWARD AND EQUATORWARD
OUTFLOW CHANNELS WHILE ADDITIONAL VENTING IS BEING INDUCED BY A TUTT
CELL POSITIONED TO THE EAST. STY 19W IS TRACKING GENERALLY WESTWARD
ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE
POSITIONED TO THE NORTHEAST AND HAS NOTICEABLY SLOWED OVER THE PAST
12 HOURS, INDICATIVE OF A WEAKENING STR.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. STY 19W WILL CONTINUE TRACKING WEST-NORTHWESTWARD UNDER THE
STEERING INFLUENCE OF THE WEAKENING STEERING RIDGE THROUGH TAU 12.
AFTER TAU 12, A MID-LATITUDE TROUGH PASSING TO THE NORTH IS EXPECTED
TO BREAK THE STEERING RIDGE, CAUSING THE SYSTEM TO MAKE A SHARP
POLEWARD TURN. STY 19W WILL THEN TRACK GENERALLY POLEWARD ALONG THE
WESTERN PERIPHERY OF THE STEERING RIDGE FROM TAU 24 THROUGH TAU 72.
CONTINUED FAVORABLE UPPER-LEVEL CONDITIONS AND PASSAGE OVER VERY
WARM SEA SURFACE TEMPERATURES SHOULD ALLOW THE SYSTEM TO REACH PEAK
INTENSITY OVER THE NEXT DAY WITH INTERACTION WITH THE AFOREMENTIONED
TUTT CELL AND INNER-CORE DYNAMICS (EYEWALL REPLACEMENT CYCLE) BEING
THE ONLY LIMITING FACTOR. A SLOW WEAKENING IS FORECAST AFTERWARDS AS
VWS BEGINS TO INCREASE. MODEL GUIDANCE IS IN GOOD AGREEMENT WITH
THE SLOW DOWN AND POLEWARD TURN THROUGH TAU 36. AFTER WHICH, THE
MODEL TRACKERS AND ENSEMBLE DATA INDICATE A WIDE SPREAD OF SOLUTIONS
WITH A SPREAD OF 300 NM AT TAU 72. DUE TO THIS, THERE IS HIGH
CONFIDENCE THROUGH TAU 36 AND LOW CONFIDENCE THERE AFTER.
   C. STY 19W WILL CONTINUE POLEWARD ALONG THE WESTERN EDGE OF THE
STEERING RIDGE DURING THE EXTENDED FORECAST PERIOD. A TRANSIENT
RIDGE IS EXPECTED TO BUILD TO THE NORTH OF THE SYSTEM LATE IN THE
FORECAST PERIOD, INDUCING A SLIGHT WESTWARD TRACK DEFLECTION BETWEEN
TAU 96 AND TAU 120. STY 19W IS EXPECTED TO WEAKEN SLOWLY IN THE
EXTENDED PERIOD AS UPPER-LEVEL OUTFLOW BECOMES LESS FAVORABLE AND
ALONG-TRACK OCEAN HEAT CONTENT DECREASES. DYNAMIC MODEL GUIDANCE
SUPPORTS THIS FORECAST SCENARIO, BUT DEPICTIONS OF THE WESTWARD
TRACK DEVIATION AND THE EXTENT OF THE TRANSITORY RIDGE VARY. GIVEN
THIS UNCERTAINTY, THE CURRENT EXTENDED FORECAST TRACK IS POSITIONED
CLOSE TO THE MULTI-MODEL CONSENSUS WHICH HAS BEEN FAIRLY STABLE OVER
THE PAST 24 HOURS GIVEN THE WIDE RANGE OF SOLUTIONS. OVERALL, THERE
IS LOW CONFIDENCE IN THE FORECAST TRACK.//
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