Tropical Storm VONGFONG Advisory Pzt, 06.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 19W (VONGFONG) WARNING NR 13//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 19W (VONGFONG), LOCATED APPROXIMATELY 44 NM EAST OF
ANDERSEN AFB, GUAM HAS TRACKED WEST-NORTHWESTWARD AT 17 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY CONTINUES TO SHOW TIGHTLY-CURVED BANDING WRAPPING INTO THE
LOW-LEVEL CIRCULATION CENTER. THE CURRENT POSITION IS BASED 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 AN AREA OF SUBSIDENCE IS LOCATED NORTH OF THE
SYSTEM IMPACTING THE CURRENT DEVELOPMENT. ADDITIONALLY, TY 19W IS
NOW LOCATED IN AN AREA OF MODERATE (10 TO 20 KNOT) VERTICAL WIND
SHEAR (VWS) OFFSET BY EXCELLENT EQUATORWARD OUTFLOW. 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. UPPER-LEVEL CONDITIONS
WILL IMPROVE SLOWLY LEADING TO A GRADUAL INTENSIFICATION AND
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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