MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 19W (VONGFONG) WARNING NR 14// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 19W (VONGFONG), LOCATED APPROXIMATELY 599 NM SOUTH OF IWO TO, HAS TRACKED WEST-NORTHWESTWARD AT 18 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS BROKEN CONVECTIVE BANDING WRAPPING INTO A RE-CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC). THE SYSTEM HAS STRUGGLED IN DEVELOPMENT DUE TO DEGRADED UPPER-LEVEL CONDITIONS OVER THE PAST 12 HOURS. A 052338Z METOP-B MICROWAVE IMAGE ALSO REVEALS THE BULK OF THE CONVECTIVE BANDING OVER THE SOUTHERN PERIPHERY WRAPPING TOWARDS THE LLCC. THE CURRENT POSITION IS BASED ON THE MSI AND 052308Z ASCAT IMAGE WITH HIGH CONFIDENCE. THE INITIAL INTENSITY HAS DECREASED TO 80 BASED ON AN OVERALL ASSESSMENT OF DVORAK INTENSITY ESTIMATES FROM ALL REPORTING AGENCIES AND CURRENT STRUCTURE. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM REMAINS IN AN AREA OF MODERATE TO STRONG (20 TO 25 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. DUE TO DEGRADED UPPER-LEVEL CONDITIONS AND SYSTEM STRUCTURE, THE FORECAST INTENSITY HAS CHANGED SLIGHTLY THROUGHOUT THE FORECAST PERIOD. OTHERWISE, THERE IS NO SIGNIFICANT CHANGE TO THE TRACK 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 ARE EXPECTED TO IMPROVE SLOWLY LEADING TO A GRADUAL INTENSIFICATION AND REACHING 125 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. DUE TO UNCERTAINTY IN THE STEERING ENVIRONMENT BEYOND TAU 72, THE JTWC FORECAST CONFIDENCE LEVEL FOR THIS PORTION OF THE FORECAST REMAINS LOW.// NNNN NNNN