MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (SONGDA) WARNING NR 04// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 23W (SONGDA), LOCATED APPROXIMATELY 246 NM SOUTHWEST OF MINAMI TORI SHIMA, HAS TRACKED WEST-NORTHWESTWARD AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY INDICATES A CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC) WITH TIGHTLY-CURVED BANDING WRAPPING INTO A DEFINED CENTER. A 082039Z SSMIS 37GHZ IMAGE DEPICTS A DEFINED MICROWAVE EYE FEATURE WITH SPIRAL BANDING WRAPPING INTO THE LLCC. ANIMATED WATER VAPOR IMAGERY REVEALS IMPROVING OUTFLOW WITH ENHANCED POLEWARD OUTFLOW ASSOCIATED WITH THE TUTT TO THE NORTH. ADDITIONALLY, EQUATORWARD OUTFLOW HAS IMPROVED AS THE BROAD UPPER-LOW TO THE SOUTHWEST HAS WEAKENED. THE CURRENT INTENSITY IS ASSESSED AT 45 KNOTS BASED ON DVORAK ESTIMATES OF T3.0 (45 KNOTS) FROM BOTH KNES AND PGTW. TS 23W IS TRACKING ALONG THE SOUTHWEST PERIPHERY OF THE DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 23W IS FORECAST TO TRACK NORTHWESTWARD THROUGH TAU 36 THEN RE-CURVE NORTHEASTWARD AS IT ROUNDS THE WESTERN PERIPHERY OF THE STR. TS SONGDA WILL RAPIDLY INTENSIFY AFTER TAU 12 DUE TO IMPROVING POLEWARD OUTFLOW ASSOCIATED WITH AN APPROACHING MIDLATITUDE SHORTWAVE TROUGH AND IS EXPECTED TO REACH A PEAK INTENSITY OF 90 KNOTS BY TAU 48. C. AFTER TAU 72, TS SONGDA WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) AS IT BEGINS TO INTERACT WITH THE MIDLATITUDE WESTERLIES AND THE ASSOCIATED STRONG BAROCLINIC ZONE. THE SYSTEM IS EXPECTED TO WEAKEN AS IT ENCOUNTERS INCREASING VERTICAL WIND SHEAR AND ACCELERATES NORTHEASTWARD. TS 23W WILL COMPLETE ETT BY TAU 120 AS IT GAINS FRONTAL CHARACTERISTICS AND BECOMES EMBEDDED WITHIN THE MIDLATITUDE WESTERLY FLOW. NUMERICAL MODEL GUIDANCE REMAINS IN GOOD AGREEMENT, THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN NNNN