Tropical Storm VONGFONG Advisory mer, 08.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 19W (VONGFONG) WARNING
NR 22//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 19W (VONGFONG), LOCATED APPROXIMATELY 571 NM
SOUTH-SOUTHEAST OF KADENA AB, OKINAWA, HAS TRACKED WEST-
NORTHWESTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED SATELLITE IMAGERY (EIR) ALONG WITH MULTISPECTRAL SATELLITE
IMAGERY REVEALS STY 19W HAS MAINTAINED A DEFINED 17 NM EYE WHILE THE
CONVECTIVE RING AROUND THE EYE HAS SLIGHTLY WARMED. A 072246Z SSMIS
IMAGE ALSO REVEALS THE SYSTEM HAS MAINTAINED STRUCTURE AND HAS NOT
CHANGED OVER THE PAST SIX HOURS. THERE IS HIGH CONFIDENCE IN THE
INITIAL POSITION BASED ON THE DEFINED EYE FEATURE IN THE EIR LOOP.
THE INITIAL INTENSITY REMAINS ASSESSED AT 155 KNOTS BASED ON DVORAK
INTENSITY ESTIMATES FROM PGTW AND RJTD AND THE UNCHANGED 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 (STR) POSITIONED TO THE NORTHEAST.
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 FROM 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 350 NM AT TAU 72 DUE TO A LARGE DISAGREEMENT OF THE
EXTENT OF THE STR AS IT REACTS TO THE TROUGH. 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 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 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 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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