MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (KROSA) WARNING NR 018// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 11W (KROSA), LOCATED APPROXIMATELY 126 NM SOUTH OF IWO TO, JAPAN, HAS TRACKED NORTHWARD AT 03 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS SLIGHTLY IMPROVED CONVECTIVE BANDING WRAPPING INTO A DEFINED LOW- LEVEL CIRCULATION CENTER (LLCC). HOWEVER, DEEP CONVECTION OVER THE CORE AND NORTHWEST QUADRANT REMAIN WEAK DUE TO THE PRESENCE OF CYCLONIC FLOW AND CONVERGENCE ALOFT WHILE STRONG DIFFLUENCE OVER THE EASTERN AND SOUTHERN FLANK CONTINUE TO FUEL DEEP CONVECTIVE BANDING. A 092130Z SSMIS 91GHZ IMAGE INDICATES TIGHTLY-CURVED BANDING WRAPPING INTO A DEFINED, BROAD LLCC, WHICH SUPPORTS THE INITIAL POSITION WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 70 KNOTS, HEDGED SLIGHTLY BELOW DVORAK CURRENT INTENSITY ESTIMATES OF 4.5 (77 KNOTS), BASED ON A 092054Z SMAP ESTIMATE OF 71 KNOTS (1- MINUTE AVERAGE). WITH THE EXCEPTION OF THE COMPLEX, MARGINALLY- FAVORABLE OUTFLOW, VERTICAL WIND SHEAR AND SST VALUES REMAIN FAVORABLE. TY 11W IS LOCATED WITHIN A WEAK STEERING ENVIRONMENT WITH A NORTH-SOUTH SUBTROPICAL RIDGE POSITIONED TO THE EAST, A WEAK STR OVER WESTERN JAPAN AND A BREAK TO THE NORTH. THEREFORE, TY 11W IS TRACKING SLOWLY POLEWARD (AND ERRATICALLY). 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. IN THE NEXT 72 HOURS, THE PRIMARY STEERING FOR TY 11W WILL GRADUALLY TRANSITION TO THE BUILDING STR TO THE NORTH OF TY 11W AND THE TRACK WILL SLOWLY SHIFT NORTHWESTWARD TOWARD JAPAN, PASSING SOUTHWEST OF IWO TO AROUND TAU 24. SLIGHTLY DIMINISHED OUTFLOW, WEAK SUBSIDENCE AND POSSIBLE UPWELLING COOLER WATER WILL MAKE THE ENVIRONMENT SOMEWHAT UNFAVORABLE THROUGH TAU 48 WITH GRADUAL WEAKENING TO ABOUT 60 KNOTS. AFTER TAU 48, AS THE SYSTEM BEGINS TO ACCELERATE WEST-NORTHWESTWARD TO NORTHWESTWARD OVER WARM SST, SLIGHT INTENSIFICATION IS EXPECTED. C. AFTER TAU 72, TY 11W WILL RECURVE POLEWARD ALONG THE SOUTHWEST PERIPHERY OF THE STR, WHICH IS EXPECTED TO WEAKEN AND REORIENT WITH THE APPROACH OF A DEEP MIDLATITUDE SHORTWAVE TROUGH. TY 11W SHOULD RE-INTENSIFY TO A PEAK INTENSITY OF 70 KNOTS AS POLEWARD OUTFLOW IMPROVES. SST VALUES WILL REMAIN CONDUCIVE (28-29C) DURING THIS EXTENDED PERIOD. NUMERICAL MODEL GUIDANCE DIVERGES SLIGHTLY BUT REMAINS IN GOOD AGREEMENT WITH A 95NM SPREAD IN SOLUTIONS AT TAU 120. BASED ON THE ERRATIC SHORT-TERM MOTION AND UNCERTAINTY IN THE LATER TAUS, THERE IS OVERALL MODERATE CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN NNNN