MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (NANGKA) WARNING NR 14// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON 11W (NANGKA), LOCATED APPROXIMATELY 652 NM EAST-SOUTHEAST OF SAIPAN, HAS TRACKED WEST-NORTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. RECENT ANIMATED ENHANCED SATELLITE INFRARED IMAGERY DEPICTS A WELL DEVELOPED SYSTEM WITH A 10 NM EYE AND ROBUST OUTFLOW. A 061806Z GPM MICROWAVE IMAGE REVEALS THE STRUCTURE OF THE EYEWALL HAS IMPROVED OVER THE PAST 6 HOURS AS IT IS SMALLER AND LESS RAGGED. THE INITIAL POSITION IS BASED ON THE EIR ANIMATION AND AFOREMENTIONED MICROWAVE IMAGE WITH HIGH CONFIDENCE. THE INTENSITY HAS BEEN ASSESSED AT 85 KNOTS BASED ON AN AVERAGE OF DVORAK INTENSITY ESTIMATES FROM PGTW AND RJTD. UPPER LEVEL ANALYSIS INDICATES AN ENVIRONMENT CHARACTERIZED BY RADIAL OUTFLOW AND 10-20 KNOT NORTHWESTERLY VERTICAL WIND SHEAR. TY 11W IS CURRENTLY TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 11W WILL CONTINUE TRACKING TO THE NORTHWEST UNDER THE EXTENSION OF THE STR THROUGH TAU 72. THE UPPER LEVEL ENVIRONMENT WILL REMAIN FAVORABLE OVER THE NEXT 48 HOURS WITH TY NANGKA PEAKING AT 115 KNOTS BY TAU 48 AND MAINTAINING THROUGH TAU 72. C. IN THE EXTENDED TAUS TY 11W WILL BEGIN TO SLOW AS AN APPROACHING MID-LATITUDE TROUGH WEAKENS THE EXTENSION OF THE STR CREATING A WEAKER STEERING ENVIRONMENT AND ALLOWING THE SYSTEM TO BEGIN MOVING POLEWARD. ALTHOUGH NANGKA WILL HAVE GOOD POLEWARD OUTFLOW, SSTS AND OHC VALUES DECREASE POLEWARD OF 19 NORTH AND VWS SHEAR WILL BEGIN TO INCREASE AS WELL. AFTER TAU 72, DYNAMIC MODEL GUIDANCE IS IN DISAGREEMENT WITH THE TIMING AND OVERALL EFFECT OF THE MID-LATITUDE TROUGH BREAKING DOWN THE STR RESULTING IN UNCERTAINTY IN THE EXTENDED TAUS. HOWEVER, THE MODEL GUIDANCE IS IN VERY GOOD AGREEMENT THROUGH TAU 72 LENDING HIGH CONFIDENCE TO THE JTWC FORECAST WHICH IS LAID CLOSE TO THE MULTI-MODEL CONSENSUS.// NNNN NNNN