MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (LEKIMA) WARNING NR 21// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 10W (LEKIMA), LOCATED APPROXIMATELY 236 NM WEST OF KADENA AB, HAS TRACKED NORTHWESTWARD AT 14 KNOTS (KTS) OVER THE PAST SIX HOURS. A 5-10 NM ROUND EYE IN ANIMATED MULTISPECTRAL SATELLITE IMAGERY PROVIDES HIGH CONFIDENCE IN THE INITIAL POSITION. DESPITE THE EYE REMAINING SMALL AND ROUND, ANIMATED ENHANCED INFRARED SATELLITE IMAGERY REVEALS THE SURROUNDING CONVECTION HAS BECOME ASYMMETRIC WITH WARMER CLOUD TOP TEMPERATURES ON THE NORTHERN SIDE. THE INITIAL INTENSITY OF 115 KTS IS BETWEEN CURRENT INTENSITY ESTIMATES FROM T5.5-6.5 (102-127 KTS). THE ENVIRONMENT WITH GOOD POLEWARD OUTFLOW, FAIR EQUATORWARD OUTFLOW, LOW (10-15 KT) VERTICAL WIND SHEAR (VWS), AND WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURE IS SUPPORTIVE BUT THERE DOES APPEAR TO BE SOME COMPARATIVELY DRY AIR ENTRAINING IN FROM THE WEST THAT IS LIKELY CONTRIBUTING TO THE WEAKENING SEEN OVER THE PAST 12 HOURS. TY 10W IS TRACKING ALONG THE SOUTHWEST PERIPHERY OF A SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. SHORTLY AFTER MAKING LANDFALL ABOUT 140 NM SOUTH OF SHANGHAI, CHINA AROUND TAU 18, TY 10W WILL BEGIN TRACKING NORTHWARD AS THE STR REORIENTS AND RECEDES SLIGHTLY TO THE EAST. THE SYSTEM SHOULD PASS NEAR SHANGHAI ON A NORTHWARD TRACK AROUND TAU 40 AND PASS BRIEFLY OVER THE YELLOW SEA ON A NORTH-NORTHWESTWARD TRACK BEFORE MAKING SECOND LANDFALL NEAR QINGDAO, CHINA PRIOR TO TAU 72. LAND INTERACTION IS EXPECTED TO WEAKEN THE SYSTEM TO 50 KNOTS BY TAU 72. THE INTENSITY FORECAST IS VERY UNCERTAIN BECAUSE SMALL SHIFTS IN THE TRACK COULD SIGNIFICANTLY IMPACT THE AMOUNT OF WEAKENING DUE TO LAND INTERACTION. NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT FOR THIS PORTION OF THE FORECAST, LENDING TO GOOD CONFIDENCE IN THE JTWC TRACK FORECAST THROUGH TAU 72. C. BETWEEN TAU 72 AND 120, TY 10W IS EXPECTED TO CONTINUE TRACKING NORTH-NORTHWESTWARD AND BEGIN ROUNDING THE STR AXIS. HIGH VWS AND LAND INTERACTION ARE EXPECTED TO CONTINUE WEAKENING THE SYSTEM, HOWEVER UNCERTAINTY IN THE INTENSITY FORECAST REMAINS HIGH DUE TO UNCERTAINTY IN THE AMOUNT OF LAND INTERACTION. NUMERICAL MODEL SPREAD INCREASES SIGNIFICANTLY AS SEVERAL MODELS (ECMWF, GALWEM, UKMET) FOLLOW THE RECURVE SCENARIO WHILE THE OTHER MEMBERS SHOW THE SYSTEM TURNING SOUTHWARD, POSSIBLY DUE TO DIRECT CYCLONE INTERACTION WITH TY 11W. THE JTWC TRACK FORECAST FAVORS THE RECURVE SCENARIO WITH LOW CONFIDENCE DUE TO MAJOR DIFFERENCES IN THE TRACK BETWEEN THE TWO FEASIBLE FORECAST SCENARIOS.// NNNN NNNN