MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (LIONROCK) WARNING NR 21// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 12W (LIONROCK), LOCATED APPROXIMATELY 362 NM EAST-NORTHEAST OF KADENA AB, HAS TRACKED SOUTHWARD AT 05 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS TS 12W CONSOLIDATING INTO A WELL DEFINED SPIRAL BANDED SYSTEM IN THE LAST SIX HOURS. A TIGHTLY WOUND LOW LEVEL CIRCULATION CENTER IS VISIBLE IN A 230101Z MHS 89 GHZ IMAGE GIVING HIGH CONFIDENCE TO THE INITIAL POSITION. THE INITIAL POSITION IS ASSESSED AT 45 KNOTS AND IS BASED ON THE IMPROVING CONVECTIVE STRUCTURE AND OBJECTIVE DVORAK FIXES FROM ALL AGENCIES REPORTING A CURRENT INTENSITY OF T3.0 (45 KNOTS). UPPER-LEVEL OUTFLOW HAS IMPROVED SLIGHTLY IN BOTH THE POLEWARD AND EQUATORWARD CHANNELS, AND VERTICAL WIND SHEAR REMAINS MODERATE NEAR 15 TO 20 KNOTS. SEA SURFACE TEMPERATURES ARE WARM NEAR 30 CELSIUS, BUT AVAILABLE OCEAN HEAT CONTENT IS RATHER LOW. TS 12W IS CURRENTLY QUASI-STATIONARY DRIFTING TO THE SOUTH IN THE ABSENCE OF A DOMINANT STEERING MECHANISM. 3. FORECAST REASONING. A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. IN THE NEAR FORECAST TS 12W WILL REMAIN QUASI-STATIONARY AS TWO BUILDING RIDGES COMPETE AS THE DOMINANT STEERING RIDGE. A SUBTROPICAL RIDGE (STR) TO THE NORTHWEST WILL HAVE MORE INFLUENCE IN THE NEXT 48 HOURS TRACKING THE SYSTEM SOUTH AND EVENTUALLY SOUTHWEST. A NEAR-EQUATORIAL RIDGE (NER) IS POSITIONED TO THE SOUTHEAST AND WILL COUNTER THE INFLUENCE OF THE SUBTROPICAL RIDGE. INTENSIFICATION IS FORECAST TO BE GRADUAL AS OUTFLOW IS EXPECTED TO IMPROVE AS THE TROUGH MOVES EAST. HOWEVER, ENHANCED OUTFLOW WILL BE OFFSET BY THE LOW OCEAN HEAT CONTENT AS THE SYSTEM CHURNS UP WATER UNDER ITS QUASI-STATIONARY TRACK. C. IN THE EXTENDED TAUS, THE NER WILL EVENTUALLY BUILD IN FROM THE SOUTH-SOUTHEAST BECOMING THE DOMINANT STEERING RIDGE AROUND TAU 72 DRIVING THE SYSTEM ON A NORTHEAST TRACK. SIMULTANEOUSLY A MIDLATITUDE TROUGH WILL MOVE INTO THE REGION ENHANCING OUTFLOW AND TS 12W IS EXPECTED TO REACH TYPHOON STRENGTH BY TAU 72 REACHING A PEAK INTENSITY OF 75 KNOTS. DYNAMIC MODEL GUIDANCE IS IN AGREEMENT THAT THE SYSTEM WILL REMAIN QUASI-STATIONARY OVER THE NEXT FEW DAYS AND EVENTUALLY TAKE A NORTHEASTWARD TRACK DUE TO THE ESTABLISHMENT OF THE NER. HOWEVER, THE SOLUTIONS ARE IN SHARP DISAGREEMENT AS TO THE EXACT POSITION AND TIMING OF THE TRACK SHIFTS. DUE TO THE COMPLEXITY OF THE STEERING ENVIRONMENT, THERE IS LOW CONFIDENCE IN FORECAST TRACK.// NNNN NNNN