MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 30W (THIRTY) WARNING NR 04// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 30W (THIRTY), LOCATED APPROXIMATELY 177 NM SOUTH-SOUTHEAST OF ANDERSEN AFB, GUAM, HAS TRACKED NORTHWESTWARD AT 23 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS A BROAD AREA OF CONVECTION WITH LIMITED FORMATIVE BANDING SLIGHTLY OFFSET OF AN OBSCURED LOW LEVEL CIRCULATION (LLC). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A PARTLY EXPOSED LLC FEATURE IN THE 281728Z SSMI MICROWAVE IMAGE. THE INITIAL INTENSITY OF 35 KNOTS IS BASED ON EQUIVALENT DVORAK ESTIMATES OF T2.5/35 KNOTS FROM PGTW AND KNES. ENVIRONMENTAL ANALYSIS SHOWS TS 30W IS IN A FAVORABLE AREA WITH LOW (05-10 KNOT) VERTICAL WIND SHEAR (VWS) AND GOOD DUAL OUTFLOW. SEA SURFACE TEMPERATURES ARE ALSO FAVORABLE AT 30-31 DEGREES CELSIUS. THE CYCLONE IS TRACKING ALONG THE SOUTHWESTERN EDGE OF THE SUBTROPICAL RIDGE (STR) TO THE NORTHEAST. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 30W WILL CONTINUE TO TRACK NORTHWESTWARD UNDER THE INFLUENCE OF THE STR THROUGHOUT THE FORECAST, PASSING APPROXIMATELY 70 NM TO THE SOUTH OF GUAM NEAR 290300Z. THE FAVORABLE CONDITIONS WILL PERSIST AND FUEL GRADUAL INTENSIFICATION TO 105 KNOTS BY TAU 72. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT WITH GRADUAL SPREADING TO 150-NM BY TAU 72. THERE IS FAIR CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK THAT IS LAID NEAR THE CONSENSUS. C. AFTER TAU 72, TS 30W WILL CONTINUE ON A NORTHWESTWARD TRACK AND BY TAU 120, WILL BE APPROXIMATELY 225 NM SOUTH-SOUTHEAST OF OKINAWA, JAPAN. THE FAVORABLE ENVIRONMENTAL CONDITIONS WILL CONTINUE AND ALLOW TS 30W TO REACH A PEAK INTENSITY OF 120 KNOTS (POSSIBLY HIGHER) BY TAU 96 BEFORE WEAKENING MAINLY DUE TO INCREASING VWS. AFTER TAU 96, TS 30W WILL BEGIN TO ROUND THE WESTERN EDGE OF THE STR AXIS AND TURN SLIGHTLY NORTHWARD. DYNAMIC MODEL GUIDANCE SIGNIFICANTLY SPREADS OUT WITH ECMWF AS THE NOTABLE LEFT OUTLIER AND CTCX ON THE RIGHT MARGIN OF THE MODEL ENVELOPE. IN VIEW OF THE LARGE SPREAD (OVER 700 NM AT TAU 120), THE CONFIDENCE IN THE EXTENDED PORTION OF THE JTWC FORECAST TRACK REMAINS LOW.// NNNN NNNN