MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (ATSANI) WARNING NR 03// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 17W (ATSANI), LOCATED APPROXIMATELY 201 NM NORTH OF ENEWETAK, HAS TRACKED WEST-NORTHWESTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC) WITH IMPROVED DEEP CONVECTIVE BANDING. A 141932Z SSMIS IMAGE REFLECTS THE IMPROVED CONVECTIVE STRUCTURE AND SHOWS TIGHTLY-CURVED CONVECTIVE BANDING WRAPPING INTO A DEFINED BUT BROAD CENTER, THEREFORE, THERE IS FAIR CONFIDENCE IN THE CURRENT POSITION. ANIMATED WATER VAPOR IMAGERY REVEALS RADIAL OUTFLOW ENHNACED BY A STRONG TUTT TO THE NORTHEAST. THE CURRENT INTENSITY IS HEDGED SLIGHTLY HIGHER THAN THE DVORAK INTENSITY ESTIMATES OF T2.0 (30 KNOTS) BASED ON THE RAPIDLY IMPROVING ORGANIZATION. TS 17W IS EMBEDDED WITHIN A COMPETING STEERING ENVIRONMENT BETWEEN A SUBTROPICAL RIDGE (STR) TO THE NORTH AND A NEAR-EQUATORIAL RIDGE (NER) TO THE SOUTH. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. SLOW MOVEMENT IS EXPECTED OVER THE NEXT 36 TO 48 HOURS AS THE SYSTEM REMAINS IN A COMPETING STEERING ENVIRONMENT. DYNAMIC GUIDANCE CONTINUES TO SUPPORT A SLOW, PERHAPS QUASI-STATIONARY MOTION THROUGH TAU 36 DUE TO THE COMPETING STEERING INFLUENCE. AFTER TAU 36, DYNAMIC GUIDANCE IS IN FAIR AGREEMENT. BY TAU 48, THE NER IS FORECAST TO WEAKEN AND SHIFT EASTWARD ALLOWING THE STR TO BUILD AND BECOME THE DOMINANT STEERING INFLUENCE. THIS WILL ALLOW TS 17W TO ACCELERATE WEST-NORTHWESTWARD THROUGH TAU 72. TS 17W IS EXPECTED TO RAPIDLY INTENSIFY AFTER TAU 24 UNDER VERY FAVORABLE ENVIRONMENTAL CONDITIONS TO INCLUDE RADIAL OUTFLOW, WARM SST AND HIGH OCEAN HEAT CONTENT. C. IN THE EXTENDED TAUS, TS 17W WILL MAINTAIN A NORTHWESTWARD TRAJECTORY AS THE SYSTEM TRACKS ALONG THE WESTERN PERIPHERY OF THE STR. AVAILABLE MODEL GUIDANCE REMAINS IN FAIR AGREEMENT, HOWEVER, THERE IS LOW OVERALL CONFIDENCE IN THE FORECAST TRACK DUE TO THE ERRATIC MOTION EXPECTED IN THE SHORT-TERM.// NNNN NNNN