WDPN31 PGTW 080300
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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