MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (SAOLA) WARNING NR 25// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 27W (SAOLA), LOCATED APPROXIMATELY 642 NM SOUTH-SOUTHEAST OF KADENA AB, HAS TRACKED NORTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SLOWLY CONSOLIDATING LOW-LEVEL CIRCULATION CENTER WITH IMPROVED DEEP CONVECTIVE BANDING WRAPPING INTO A MORE DEFINED CENTER. THE INITIAL POSITION IS BASED ON ANIMATED EIR AND A TIMELY 251800Z SSMI 37GHZ IMAGE, WHICH SHOWS TIGHTLY-CURVED BANDING WRAPPING INTO A MICROWAVE EYE FEATURE. THE INITIAL INTENSITY IS ASSESSED AT 50 KNOTS, HEDGED SLIGHTLY HIGHER THAN DVORAK ESTIMATES OF T3.0 (45 KNOTS) FROM RJTD AND PGTW, BASED ON A RECENT SATCON ESTIMATE OF 50 KNOTS AS WELL AS THE MICROWAVE EYE FEATURE. UPPER- LEVEL ANALYSIS DEPICTS A DEVELOPING POINT SOURCE OVER THE SYSTEM AND IMPROVED OVERALL OUTFLOW, ESPECIALLY OVER THE EAST AND SOUTHEAST QUADRANTS. TS 27W IS TRACKING POLEWARD ALONG THE WESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TOWARD A BREAK SITUATED NEAR OKINAWA. 3. FORECAST REASONING. A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. THE 34-KNOT WIND RADII HAVE BEEN ADJUSTED BASED ON A DETAILED ANALYSIS OF THE 251203Z ASCAT IMAGE. B. WITH THE EXCEPTION OF NAVGEM, DYNAMIC MODEL GUIDANCE REMAINS IN FAIR AGREEMENT WITH A 225NM SPREAD IN SOLUTIONS AT THE RECURVE POINT NEAR OKINAWA. TS 27W IS FORECAST TO TRACK NORTH-NORTHWESTWARD TO NORTHWARD THROUGH TAU 72 AND IS EXPECTED TO RECURVE JUST EAST OF OKINAWA WHILE BEGINNING EXTRA-TROPICAL TRANSITION (ETT). NAVGEM REMAINS THE SOLE OUTLIER INDICATING A SLOW NORTHWESTWARD TO WESTWARD TRACK (THROUGH TAU 120) OVER TAIWAN. ANALYSIS OF NAVGEM FIELDS INDICATES AN ERRONEOUS TRACK DUE TO EXCESSIVE DIRECT CYCLONE INTERACTION THEN A QUASI-STATIONARY TRACK AFTER TAU 72 AS THE SYSTEM GETS TRAPPED WITHIN A STRONG COLD SURGE FORECAST TO BUILD IN TO THE EAST CHINA SEA. TS 27W WILL CONTINUE TO INTENSIFY TO A PEAK INTENSITY OF 85 KNOTS BY TAU 72 AS POLEWARD OUTFLOW IMPROVES SIGNIFICANTLY WITH VENTING INTO THE MIDLATITUDE WESTERLIES. C. IN THE EXTENDED PERIOD, TS 27W IS FORECAST TO ACCELERATE NORTHEASTWARD WITHIN THE MIDLATITUDE WESTERLIES. THE SYSTEM WILL COMPLETE ETT NEAR TAU 96 AS IT GAINS FRONTAL CHRACTERISTICS AND BECOMES EMBEDDED WITHIN THE MIDLATITUDE WESTERLIES. THE GLOBAL MODELS INDICATE AN ARCTIC COLD SURGE OVER JAPAN NEAR TAU 120, WHICH COULD AFFECT BOTH TRACK SPEED AND INTENSITY, HOWEVER, IT'S TOO EARLY TO ACCURATELY ASSESS THE IMPACT OR TO JUSTIFY CHANGING THE FORECAST PHILOSOPHY. DUE TO THE UNCERTAINTY IN MODEL GUIDANCE AFTER TAU 72, THERE IS LOW OVERALL CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN NNNN