MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 18W (PHANFONE) WARNING NR 19// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 18W (PHANFONE), LOCATED APPROXIMATELY 374 NM WEST- SOUTHWEST OF IWO TO, HAS TRACKED NORTHWESTWARD AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY INDICATES A SLIGHT IMPROVEMENT WITH A 16-NM RAGGED EYE; HOWEVER, DEEP CONVECTIVE BANDING WEAKENED OVER THE NORTHERN SEMI-CIRCLE. A 030455Z NOAA-19 89GHZ IMAGE DEPICTS A SMALL 210-NM DEEP CONVECTIVE CORE WITH CONVECTIVE BANDING WRAPPING INTO AN OBLONG MICROWAVE EYE FEATURE. OVERALL, THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION AND RECENT MOTION. THE INITIAL INTENSITY REMAINS ASSESSED AT 110 KNOTS, HEDGED SLIGHTLY LOWER THAN DVORAK CURRENT INTENSITY ESTIMATES OF 115 KNOTS. TY 18W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF THE DEEP SUBTROPICAL RIDGE (STR) TOWARD A LARGE BREAK IN THE STR, POSITIONED SOUTH OF WESTERN JAPAN, CAUSED BY A BROAD MIDLATITUDE TROUGH CENTERED OVER THE KOREAN PENINSULA. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING BULLETIN. B. TY 18W IS FORECAST TO TRACK NORTHWARD THROUGH TAU 36 AS IT TRACKS ALONG THE WESTERN PERIPHERY OF THE STR THEN SHOULD TURN SHARPLY NORTHEASTWARD AS IT ROUNDS THE AXIS OF THE STR NEAR TAU 48 AND BEGINS EXTRA-TROPICAL TRANSITION (ETT) AND INTERACTS WITH THE MIDLATITUDE WESTERLIES. DYNAMIC MODEL GUIDANCE CONTINUES TO INDICATE UNCERTAINTY IN THE EXACT RE-CURVE POINT AND TIMING WITH SOME MODELS SHOWING A SLOWER RE-CURVE, FURTHER WEST (NOTABLY JGSM, JENS, ECMWF) WHILE THE REMAINING MODELS INDICATE FASTER TRACK SPEEDS. THERE IS CURRENTLY A 150NM SPREAD IN SOLUTIONS AT THE RE-CURVE POINT NEAR TAU 36. AS TY 18W ACCELERATES EAST-NORTHEASTWARD TOWARD THE KANTO PLAIN, UNDERGOING ETT THEY DIVERGE FURTHER WITH SEVERAL DYNAMIC MODELS TRACKING THE SYSTEM INTO STRONG MIDLATITUDE WESTERLY FLOW, WHICH IS FORECAST TO DEVELOP OVER CENTRAL JAPAN. THE JTWC FORECAST FAVORS A TRACK FURTHER SOUTH RATHER THAN INTO THE STRONG WESTERLIES, WHICH IS UNLIKELY, HOWEVER, TY 18W IS EXPECTED TO RAPIDLY COMPLETE ETT AND GAIN FRONTAL CHARACTERISTICS NEAR THE KANTO PLAIN LENDING INCREASED UNCERTAINTY TO POSITIONING DUE TO A BROADENING LOW PRESSURE AREA. REGARDLESS OF WHETHER THE SYSTEM IS WARM-CORE OR COLD-CORE, STORM FORCE WINDS ARE FORECAST DUE TO THE STRONG PRESSURE GRADIENT ENHANCED BY A STRONG BAROCLINIC ZONE OVER JAPAN. OVERALL, THERE IS LOW CONFIDENCE IN THE JTWC TRACK DUE TO SIGNIFICANT MODEL TRACK SPEED DIFFERENCES AND TRACK UNCERTAINTY ASSOCIATED WITH THE RAPID ETT PROCESS.// NNNN NNNN