MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 28W (TRAMI) WARNING NR 18/ RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUPER TYPHOON (STY) 28W (TRAMI), LOCATED APPROXIMATELY 423 NM SOUTH OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED WEST-SOUTHWESTWARD AT 03 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE SYSTEM HAS MAINTAINED A HIGHLY SYMMETRIC EYEWALL SURROUNDING AN ENLARGED 39-NM EYE. THE MSI ANIMATION ALSO SHOWS THE SYSTEM HAS SIGNIFICANTLY SLOWED DOWN. THE INITIAL POSITION, PLACED WITH HIGH CONFIDENCE, IS ADJUSTED SLIGHTLY FROM THE EYE FEATURE TO ACCOUNT FOR TILT AND LINED UP WITH A WELL-DEFINED MICROWAVE EYE IN THE 242145Z 37 GHZ SSMIS PASS. THE INITIAL INTENSITY OF 140 KNOTS IS BASED ON EQUIVALENT DVORAK FIXES OF T7.0/140 KTS FROM PGTW AND RJTD. STY 28W IS IN AN AREA OF LOW VERTICAL WIND SHEAR AND ROBUST RADIAL OUTFLOW WITH A STRONG POLEWARD CHANNEL INTO A DEEP UPPER-LEVEL SHORTWAVE TROUGH OVER THE EAST CHINA SEA. ADDITIONALLY, SEA SURFACE TEMPERATURES IN THE PHILIPPINE SEA ARE HIGHLY CONDUCIVE AT 30 CELSIUS. THE CYCLONE IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. STY 28W IS FORECAST TO TRACK VERY SLOWLY NORTHWARD OR EVEN BECOME QUASI-STATIONARY IN A COL AREA AS THE STEERING STR IS NOW BEING ERODED BY THE AFOREMENTIONED MIDLATITUDE SHORTWAVE TROUGH. AFTER TAU 48, THE STR IS EXPECTED TO SLOWLY REBUILD AND DRIVE THE SYSTEM BACK TO A NORTHWESTWARD COURSE. THE FAVORABLE ENVIRONMENT WILL PREVAIL IN THE NEAR-TERM AND MAINTAIN THE INTENSITY OF 140 KNOTS UP TO TAU 12. AFTERWARD, DECREASING OUTFLOW WILL PRIMARILY CAUSE A GRADUAL WEAKENING, DOWN TO 105 KNOTS BY TAU 72. NUMERICAL MODEL GUIDANCE IS BIFURCATED WITH THE MAJORITY INDICATING THE POLEWARD TURN AND JGSM AND NVGM OFFERING A STRAIGHT WEST-NORTHWESTWARD SOLUTION. ADDITIONALLY, THERE ARE SIGNIFICANT DIFFERENCES IN TRACK SPEEDS AND A NOTABLE SPREAD IN THE POLEWARD TRACK AMONG THE MAJORITY MEMBERS. IN VIEW OF THESE, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST THAT IS LAID TO THE RIGHT OF CONSENSUS TO OFFSET THE UNLIKELY JGSM/NVGM SOLUTION. C. AFTER TAU 72, STY TRAMI WILL CONTINUE ON A NORTHWESTWARD TRACK UNDER A REBUILT STR, AND AFTER TAU 96, WILL CREST THE STR RIDGE AND RECURVE NORTHEASTWARD. AFTER TAU 96, A RESURGENCE IN THE POLEWARD OUTFLOW ASSOCIATED WITH THE PREVAILING WESTERLIES WILL FUEL A SECONDARY INTENSIFICATION PHASE, REACHING 115 KNOTS BY TAU 120. NUMERICAL MODEL GUIDANCE SPREADS OUT EVEN MORE IN THE EXTENDED TAUS, LEADING TO LOW CONFIDENCE IN THE LATTER PORTION OF THE JTWC TRACK FORECAST, AS WELL.// NNNN NNNN