MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (LEKIMA) WARNING NR 05// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 10W (LEKIMA), LOCATED APPROXIMATELY 479 NM SOUTH-SOUTHEAST OF KADENA AB, HAS TRACKED NORTH-NORTHWESTWARD AT 06 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) REVEALS AN EXPOSED, BROAD LOW LEVEL CIRCULATION (LLC) WITH DEEP CONVECTION WRAPPING INTO THE CENTER FROM THE SOUTH. THERE IS FAIR CONFIDENCE IN THE INITIAL POSITION PLACED USING THE MSI AND SHALLOW BANDING IN A 042238Z SSMIS 91 GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY OF 35 KTS IS CONSISTENT WITH MULTI-AGENCY DVORAK ESTIMATES OF T2.5 (35 KTS). THE ENVIRONMENT IS FAVORABLE WITH RADIAL OUTFLOW, WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURE, AND LOW (10-15 KT) VERTICAL WIND SHEAR (VWS). TS 10W IS TRACKING SLOWLY ALONG THE SOUTHWEST PERIPHERY OF A SUBTROPICAL RIDGE (STR) THAT IS BEING DISTORTED BY TS 09W. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE OVERALL FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. THROUGH TAU 48, TS 10W IS EXPECTED TO CONTINUE TRACKING NORTHWESTWARD AND SLOWLY ACCELERATE AS TS 09W MOVES AWAY AND THE STR BUILDS BEHIND IT. THE FAVORABLE ENVIRONMENT SHOULD SUPPORT STEADY INTENSIFICATION TO 65 KTS BY TAU 72. UNCERTAINTY IN THE MODEL TRACK GUIDANCE FOR THIS PORTION OF THE FORECAST IS VERY HIGH AS THREE OUTLIERS (UKMET AND GALWEM TO THE NORTH, NAVGEM TO THE SOUTH) DIFFER SIGNIFICANTLY FROM THE REMAINING MEMBERS AND THE JTWC TRACK FORECAST. AT TAU 72, SPREAD IS OVER 230 NM RESULTING IN LOW CONFIDENCE IN THE FORECAST TRACK THROUGH TAU 72. C. BEYOND TAU 72, TS 10W IS EXPECTED TO GRADUALLY TURN MORE POLEWARD AS IT ROUNDS THE STR AXIS. ASSUMING THE SYSTEM FOLLOWS THE FORECAST TRACK, THE FAVORABLE ENVIRONMENT SHOULD CONTINUE AND ALLOW INTENSITY TO REACH 90 KTS BY TAU 120. TRACK SPREAD EXCEEDS 950 NM BY TAU 120, WITH MEMBERS PLACING THE CENTER BETWEEN CENTRAL CHINA AND JUST SOUTH OF JAPAN. THE HIGH UNCERTAINTY IN THE TRACK GUIDANCE COULD GREATLY AFFECT THE ENVIRONMENTAL AND LAND INTERACTION EFFECTS, RESULTING IN HIGH UNCERTAINTY IN THE INTENSITY FORECAST. BASED ON THE VERY HIGH SPREAD IN THE MODEL GUIDANCE, THERE IS LOW CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN NNNN