MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 28W (TRAMI) WARNING NR 07// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 28W (TRAMI), LOCATED APPROXIMATELY 866 NM SOUTHEAST OF KADENA AB, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A CONSOLIDATING SYSTEM WITH IMPROVED DEEP CONVECTIVE BANDING WRAPPING INTO A MORE DEFINED YET RAGGED LOW-LEVEL CIRCULATION CENTER (LLCC). THIS IMPROVEMENT IS EVIDENT IN A 220633Z MHS 89GHZ IMAGE, WHICH REVEALS DEEP CONVECTIVE BANDING WRAPPING INTO A WEAK MICROWAVE EYE FEATURE. CONSEQUENTLY, THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION. THE INITIAL INTENSITY IS ASSESSED AT 50 KNOTS BASED ON AN AVERAGE OF DVORAK ESTIMATES RANGING FROM T3.0 (45 KNOTS) TO T3.5 (55 KNOTS) WITH A RECENT BYU HIRES ASCAT IMAGE SHOWING 40 TO 45 KNOTS. UPPER-LEVEL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH NEAR-RADIAL OUTFLOW, ENHANCED BY A TUTT CELL TO THE NORTHEAST, AND LOW VERTICAL WIND SHEAR. TS 28W IS TRACKING WEST- NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. THE INITIAL 34-KNOT WIND RADII HAVE BEEN ADJUSTED BASED ON A DETAILED ANALYSIS OF A RECENT ASCAT IMAGE. B. TS TRAMI IS FORECAST TO TRACK WEST-NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE AFOREMENTIONED STR THROUGH TAU 72. NUMERICAL MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT WITH A 100NM SPREAD IN SOLUTIONS AT TAU 72. THE SYSTEM IS EXPECTED TO RAPIDLY INTENSIFY UNDER FAVORABLE CONDITIONS FROM TAU 12 TO TAU 72 WITH AN INTENSITY OF 125 KNOTS ANTICIPATED BY TAU 72. C. AFTER TAU 72, A MIDLATITUDE SHORTWAVE TROUGH WILL DEEPEN OVER THE EAST CHINA SEA AND WESTERN JAPAN CREATING A BROAD, PERSISTENT BREAK IN THE STR. THIS WILL RESULT IN A SLIGHT POLEWARD TURN AND SIGNIFICANT DECREASE IN TRACK SPEEDS AS THE STEERING INFLUENCE ERODES QUICKLY. NUMERICAL MODEL GUIDANCE INDICATES INCREASING SPREAD AND GREATER UNCERTAINTY IN THE EXACT FORECAST TRACK WITH A 250-NM SPREAD IN SOLUTIONS AT TAU 120. FOUR MODELS (NAVGEM, UKMET, AFUM AND JGSM) DEPICT A WESTWARD TRACK WHILE THE BULK OF THE GUIDANCE SHOWS A SLOW WEST-NORTHWESTWARD TO NORTHWESTWARD TRACK TOWARD THE BREAK IN THE STR. THE JTWC OFFICIAL FORECAST FAVORS A SLOW, POLEWARD TRACK AS THE MORE LIKELY SCENARIO CONSIDERING THE STRENGTH / PROXIMITY OF THE SHORTWAVE TROUGH AND THE PRESENCE OF A PERSISTENT BREAK IN THE STR. OVERALL, THERE IS LOW CONFIDENCE IN THE JTWC TRACK DUE TO THE LARGE SPREAD IN SOLUTIONS AFTER TAU 72. TS TRAMI SHOULD REACH SUPER TYPHOON INTENSITY IN THE EXTENDED PERIOD.// NNNN NNNN