WDPN31 PGTW 051500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 19W (VONGFONG) WARNING NR 12//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 19W (VONGFONG), LOCATED APPROXIMATELY 105 NM EAST OF
ANDERSEN AFB, HAS TRACKED WEST-NORTHWESTWARD AT 15 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY
SHOWS THE SYSTEM HAS MAINTAINED TIGHTLY CURVED FEEDER BANDS WITH DEEP
CONVECTIVE TOPS FEEDING INTO A RECURRING PINHOLE EYE. THE INITIAL
POSITION IS BASED ON THE PINHOLE EYE ON THE EIR LOOP AND ON RADAR
FIXES FROM NWS GUAM 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 A FAVORABLE ENVIRONMENT WITH LOW VERTICAL WIND
SHEAR (VWS) AND EXCELLENT RADIAL OUTFLOW WITH AN IMPROVED
NORTHEASTWARD CHANNEL INTO A TUTT CELL. 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 72. FAVORABLE ENVIRONMENTAL
CONDITIONS ARE EXPECTED TO PERSIST, ALLOWING TY 19W TO STEADILY
INTENSIFY, REACHING 130 KNOTS BY TAU 72. DYNAMIC MODEL GUIDANCE
REMAINS IN TIGHT AGREEMENT LENDING HIGH CONFIDENCE TO THE FIRST 72
HOURS OF THE FORECAST.
   C. TY VONGFONG IS EXPECTED TO TRACK ON A MORE POLEWARD DIRECTION
AS THE STR WEAKENS IN RESPONSE TO A MID-LATITUDE TROUGH APPROACHING
FROM THE NORTHWEST. THE SYSTEM WILL BEGIN TO WEAKEN AFTER TAU 96, AS
VWS INCREASES. AVAILABLE MODEL GUIDANCE REMAINS SIGNIFICANTLY SPREAD
DURING THIS PORTION OF THE FORECAST, LENDING LOW CONFIDENCE IN THE
JTWC TRACK FORECAST BEYOND TAU 72.//
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