WDPN32 PGTW 070300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 18W (EIGHTEEN) WARNING NR 02// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION 18W (EIGHTEEN), LOCATED APPROXIMATELY 187 NM SOUTHWEST OF IWO TO, JAPAN, HAS TRACKED NORTH-NORTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE (MSI) IMAGERY SHOWS THE SYSTEM HAS, FOR THE MOST PART, MAINTAINED CONVECTIVE AND BANDING SIGNATURE WITH THE BULK OF THE CONVECTION AMASSED TO THE NORTH OF THE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS BASED ON THE MSI ANIMATION AND ON RECENT MICROWAVE SATELLITE IMAGERY WITH FAIR CONFIDENCE. THE INITIAL INTENSITY OF 30 KNOTS IS BASED ON CONGRUENT DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS WEST OF A SUBTROPICAL HIGH IN AN AREA OF LOW TO MODERATE (10-15 KNOT) VERTICAL WIND SHEAR (VWS). MODERATE RADIAL OUTFLOW IS PARTIALLY OFFSETTING THE VWS AND PROVIDING VENTILATION TO THE ASSOCIATED CONVECTION. THE CYCLONE IS CURRENTLY TRACKING ALONG THE WESTERN EXTENSION OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTHEAST. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD 18W WILL CONTINUE ALONG ITS CURRENT TRACK OVER THE NEXT 48 HOURS. AFTERWARDS, THE STR IS FORECAST TO REORIENT AND CAUSE THE SYSTEM TO TRACK MORE NORTHWESTWARD. TD 18W IS EXPECTED TO SLOWLY INTENSIFY AS POLEWARD OUTFLOW INCREASES, PEAKING AT 55 KNOTS BY TAU 48. AFTER TAU 48, INCREASING VWS AND INTERACTION WITH A FRONTAL BOUNDARY WILL RAPIDLY ERODE THE SYSTEM BEFORE IT MAKES LANDFALL OVER SOUTHERN HONSHU, JAPAN, BEFORE TAU 72. C. AFTER TAU 72, TD 18W WILL DISSIPATE AS IT EXITS THE JAPANESE ISLANDS INTO THE SEA OF JAPAN AS IT GETS EMBEDDED IN THE BAROCLINIC ZONE BEHIND THE AFOREMENTIONED FRONTAL BOUNDARY. THE AVAILABLE NUMERIC GUIDANCE IS IN FAIRLY GOOD AGREEMENT UP TO TAU 36. AFTERWARDS, THE CONSENSUS MEMBERS WIDELY SPREAD. IN VIEW OF THIS, THERE IS AN OVERALL LOW CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN