WDPN31 PGTW 061500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 19W (VONGFONG) WARNING NR 16//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 19W (VONGFONG), LOCATED APPROXIMATELY 886 NM
SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED WEST-
NORTHWESTWARD AT 21 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED 
INFRARED SATELLITE IMAGERY SHOWS THE SYSTEM HAS MAINTAINED DEEP 
CONVECTIVE TOPS AND COMPACT SPIRAL BANDS. THE INITIAL POSITION IS 
BASED ON A MICROWAVE EYE FEATURE ON A 061132Z AMSU-B PASS WITH HIGH 
CONFIDENCE. THE INITIAL INTENSITY OF 90 KNOTS IS BASED ON AN OVERALL 
ASSESSMENT OF DVORAK INTENSITY ESTIMATES FROM ALL REPORTING 
AGENCIES. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM REMAINS IN AN
AREA OF LIGHT TO MODERATE (10 TO 20 KNOT) VERTICAL WIND SHEAR (VWS).
HOWEVER, THE VWS IS OFFSET BY EXCELLENT EQUATORWARD OUTFLOW.
ADDITIONALLY, A POLEWARD OUTFLOW CHANNEL IS BECOMING APPARENT ON
ANIMATED WATER VAPOR IMAGERY. TY 19W IS CURRENTLY TRACKING ALONG THE
SOUTHERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE
NORTH.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 19W WILL CONTINUE TRACKING WEST-NORTHWESTWARD UNDER THE 
STEERING INFLUENCE OF THE STR THROUGH TAU 48. AFTERWARDS, IT IS
EXPECTED TO TRACK MORE POLEWARD AS THE STR WEAKENS IN RESPONSE TO A
MID-LATITUDE TROUGH APPROACHING FROM THE NORTHWEST. UPPER-LEVEL
CONDITIONS ARE EXPECTED TO FURTHER IMPROVE LEADING TO RAPID
INTENSIFICATION, PEAKING AT 130 KNOTS BY TAU 48.
   C. TY VONGFONG IS EXPECTED TO TRACK POLEWARD ALONG THE WESTERN
EDGE OF THE AFOREMENTIONED STEERING STR. INCREASING VWS WILL
GRADUALLY WEAKEN THE CYCLONE AS IT GETS ABSORBED INTO THE
MID-LATITUDE WESTERLIES. DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT
FOR THE FIRST HALF OF THE FORECAST THEN SIGNIFICANTLY SPREADS. IN
VIEW OF THIS, THERE IS HIGH CONFIDENCE IN THE FIRST HALF BUT LOW
CONFIDENCE IN THE SECOND HALF OF THE JTWC TRACK FORECAST.//
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