MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (LEKIMA) WARNING NR 06// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 10W (LEKIMA), LOCATED APPROXIMATELY 456 NM SOUTH-SOUTHEAST OF KADENA AB, HAS TRACKED NORTHWESTWARD AT 05 KNOTS 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 050649Z 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 MODERATE (15-20 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. RIDGING BUILDING IN FROM THE NORTHEAST LATE IN THE FORECAST HAS BECOME THE DOMINANT STEERING FEATURE, PULLING THE EXTENDED TRACK SIGNIFICANTLY FURTHER WEST OVER EASTERN CHINA. 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 HIGH AS THERE IS A 220NM SPREAD AT TAU 72 WITH THE MOST SIGNIFICANT VARIABILITY BETWEEN NVGM AND JGSI TRACKS. C. BEYOND TAU 72, TS 10W IS EXPECTED TO GRADUALLY TURN MORE POLEWARD AS IT ROUNDS THE STR AXIS AROUND TAU 96. ASSUMING THE SYSTEM FOLLOWS THE FORECAST TRACK, THE ENVIRONMENT WILL REMAIN FAVORABLE UNTIL LAND INTERACTION EFFECTS ARE INTRODUCED AS IT BEGINS TRACKING OVER TAIWAN AROUND TAU 90. TRACK SPREAD AT TAU 120 HAS BEEN SIGNIFICANTLY REDUCED WITH UNCERTAINTY BETWEEN POSITION OVER COASTAL CHINA OR FURTHER INLAND. 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 HIGH SPREAD IN THE MODEL GUIDANCE, THERE IS LOW CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN NNNN