MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 19W (VONGFONG) WARNING NR 09// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 19W (VONGFONG), LOCATED APPROXIMATELY 407 NM EAST- SOUTHEAST OF ANDERSEN AFB, GUAM, HAS TRACKED WEST-NORTHWESTWARD AT 16 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY(EIR) CONTINUES TO SHOW DEEPENED CENTRAL CONVECTION WITH TIGHT-CURVED BANDING WRAPPING INTO THE LOW-LEVEL CIRCULATION, ALSO EVIDENT IN A 041658Z SSMI MICROWAVE IMAGE. THE CURRENT POSITION IS BASED ON THE EIR ANIMATION, TIGHT-GROUPING OF SATELLITE FIXES FROM ALL AGENCIES AND SSMI IMAGE WITH HIGH CONFIDENCE. THE INITIAL INTENSITY OF 65 KNOTS IS BASED ON MATCHING DVORAK INTENSITY ESTIMATES FROM PGTW AND KNES. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM REMAINS IN A FAVORABLE ENVIRONMENT WITH LOW VERTICAL WIND SHEAR AND EXCELLENT RADIAL OUTFLOW. ADDITIONALLY, THERE IS A POINT- SOURCE DIRECTLY OVER THE SYSTEM SUSTAINING THE INCREASED CONVECTION. TY 19W IS CURRENTLY TRACKING ALONG THE SOUTHERN PERIPHERY OF A DEEP- LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. THE EXTENDED TRACK FORECAST HAS CHANGED DUE TO A DISAGREEMENT AMONG MODEL GUIDANCE. SEE PARA 3.C. FOR DETAILS. OTHERWISE, 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 CONTINUE TO PERSIST, ALLOWING TY 19W TO STEADILY INTENSIFY, REACHING 120 KNOTS BY TAU 72. DYNAMIC MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT LENDING HIGH CONFIDENCE TO THE FIRST 72 HOURS OF THE FORECAST. C. BEYOND TAU 72, TY VONGFONG IS EXPECTED TO TRACK ON A MORE NORTHWESTWARD DIRECTION AS THE STR RECEDES SLIGHTLY IN RESPONSE TO A MID-LATITUDE TROUGH APPROACHING FROM THE NORTHWEST. FAVORABLE CONDITIONS ARE EXPECTED TO PERSIST ALLOWING TY 19W TO FURTHER INTENSIFY PEAKING AT 125 KNOTS BY TAU 96. AVAILABLE MODEL GUIDANCE SIGNIFICANTLY DIVERGES AFTER TAU 72. GFS SOLUTION INDICATES THE SYSTEM SHIFTS POLEWARD SOONER THAN THE MAJORITY OF THE AVAILABLE TRACKERS WHICH TAKES TY 19W FURTHER WESTWARD BEFORE TURNING POLEWARD. DUE TO A LARGE SPREAD AND THE UNCERTAINTY IN THE EXTEND OF THE STEERING STR, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE FORECAST PERIOD .// NNNN NNNN