WDPN33 PGTW 260300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (SAOLA) WARNING NR 26// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 27W (SAOLA), LOCATED APPROXIMATELY 589 NM SOUTH- SOUTHEAST OF KADENA AB, HAS TRACKED NORTH-NORTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY ILLUSTRATES THAT THE SYSTEM IS STRUGGLING TO CONSOLIDATE, WITH FLARING DEEP CONVECTION COALESCING INTO WELL-DEFINED BANDS ON THE SOUTHWEST SIDE, WITH LITTLE TO NO CONVECTIVE ACTIVITY ON THE NORTH SIDE. THE LOW LEVEL CIRCULATION CENTER (LLCC) IS WELL-DEFINED BY THE LOW LEVEL CLOUD LINES BUT IS PARTIALLY EXPOSED ALONG THE NORTHERN PORTION OF THE CIRCULATION. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE ANIMATED IMAGERY AND EXTRAPOLATION FROM A 252152Z 37GHZ SSMIS MICROWAVE FIX POSITION. HINTS OF A MICROWAVE EYE SEEN IN EARLIER IMAGERY APPEARS TO HAVE DISSIPATED OR WEAKENED AND IS NO LONGER EVIDENT IN AVAILABLE MICROWAVE IMAGERY. THE INITIAL INTENSITY IS ASSESSED AT 45 KNOTS BASED ON MULTI-AGENCY DVORAK INTENSITY OF ESTIMATES OF T3.0 (45 KTS), SATELLITE CONSENSUS (SATCON) ESTIMATES OF 46 KNOTS AND AUTOMATED DVORAK ESTIMATES OF T2.2 (32 KTS). ENVIRONMENTAL ANALYSIS INDICATES MARGINALLY FAVORABLE CONDITIONS WITH LOW TO MODERATE (10-15 KNOTS) VERTICAL WIND SHEAR (VWS) AND HIGH SEA SURFACE TEMPERATURES (31 CELSIUS). THESE FAVORABLE CONDITIONS ARE BEING OFFSET BY WEAK, THOUGH IMPROVING, EQUATORWARD OUTFLOW, PROVIDED BY A WEAK POINT SOURCE NEAR THE SYSTEM WHICH IS ITSELF BEING OFFSET BY A STRONG ANTICYCLONE TO THE NORTH, LIMITING CONSOLIDATION OF THE SYSTEM ON THE NORTHERN PERIPHERY. THE SYSTEM IS ALSO TRANSITING OVER A POOL OF LOW OCEAN HEAT CONTENT (OHC) VALUES, WHICH IS SERVING TO HINDER INTENSIFICATION. TS SAOLA IS TRACKING TO THE NORTHWEST ALONG THE SOUTHWESTERN EXTENT OF A DEEP LAYERED SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTHEAST. 3. FORECAST REASONING. A. THIS FORECAST REPRESENTS A SHIFT IN THE OVERALL TRACK PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. THE TRACK HAS SLOWED SIGNIFICANTLY AFTER TAU 72 AND SHIFTED SOUTHWARD IN RESPONSE TO A ROBUST COLD SURGE ASSOCIATED WITH PASSAGE OF A STRONG COLD FRONT ACROSS JAPAN NEAR TAU 96. B. TS 27W IS FORECAST TO CONTINUE TO TRACK WEST-NORTHWEST THEN NORTHWESTWARD THROUGH TAU 48, ALONG THE SOUTHWESTERN PERIPHERY OF THE STR. TS 27W WILL BEGIN TO SLOW ITS FORWARD SPEED AFTER TAU 36, AS IT ENTERS A COMPETING STEERING ENVIRONMENT AND APPROACHES THE RIDGE AXIS, IN THE VICINITY OF OKINAWA. THE SYSTEM WILL ROUND THE RIDGE AFTER TAU 48 AND BEGIN TO TRACK EAST-NORTHEASTWARD BY TAU 72. SLOW INTENSIFICATION IS FORECAST THROUGH TAU 36 AS THE MARGINALLY FAVORABLE ENVIRONMENT PERSISTS. THE SYSTEM WILL UNDERGO A BRIEF SPURT OF INTENSIFICATION NEAR TAU 48 AS IT NEARS THE RIDGE AXIS AND TAPS INTO DUAL CHANNEL OUTFLOW, PEAKING AT 75 KNOTS. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 24, BUT SHOWS INCREASING SPREAD THEREAFTER, WITH A 350NM SPREAD IN SOLUTIONS AT THE RECURVE POINT NEAR OKINAWA. SINCE THE PREVIOUS FORECAST, THE NAVGEM, GFS, JGSM AND GALWEM TRACKERS HAVE ALL SHIFTED WEST, NOW SHOWING EITHER LANDFALL AT OKINAWA OR A TRACK TO THE WEST OF OKINAWA BY TAU 48 AND A SHARP SHIFT TO THE EAST BY TAU 72 AHEAD OF THE PREVIOUSLY MENTIONED COLD FRONT. NAVGEM SHOWS THE SYSTEM BECOMING QUASI-STATIONARY IN THE EAST CHINA SEA THROUGH THE END OF THE FORECAST. THE REMAINDER OF THE MODELS INDICATES A MORE RAPID RECURVE AND ACCELERATION ALONG THE JAPANESE COAST. THE WESTERN GROUPING OF MODEL TRACKERS HAS BEEN CONSISTENT OVER THE PAST THREE MODEL RUNS, LENDING INCREASING CONFIDENCE IN THIS SOLUTION, THOUGH THE SCENARIO REMAINS HIGHLY UNCERTAIN. THE JTWC TRACK HAS BEEN ADJUSTED TO REFLECT THE INCREASING CONFIDENCE, SLOWING THE SYSTEM AND TAKING IT MORE WESTWARD TOWARDS OKINAWA. WITH THE LARGE AMOUNT OF UNCERTAINTY IN THE TIMING AND STRENGTH OF THE APPROACHING COLD FRONTAL SYSTEM AND LARGE SPREAD IN THE MODELS, THERE IS LOW CONFIDENCE IN THE JTWC TRACK FORECAST. C. AFTER TAU 72, THE FORECAST HAS BECOME HIGHLY UNCERTAIN. THE WESTERN GROUPING OF MODELS ALL INDICATE A SHARP TURN TO A SLOW, NEARLY DUE EAST TRACK AFTER TAU 72, DISSIPATING THE SYSTEM TO THE WEST OF IWO TO BY TAU 120 IN RESPONSE TO THE STRONG SURGE OF COLD, DRY AIR FROM THE NORTH, BLOCKING ANY NORTHWARD MOVEMENT. THE REMAINDER OF THE MODELS (ALL SECOND INTERPOLATIONS) TO INCLUDE THE UKMET, EGRR, ECMWF AND HWRF, CONTINUE WITH A TRADITIONAL RECURVE SCENARIO AND RAPIDLY TRACK THE SYSTEM NORTHEAST ALONG THE COAST OF JAPAN, AHEAD OF THE COLD SURGE. THESE MODELS HAVE, HOWEVER, SIGNIFICANTLY SLOWED FORWARD TRACK SPEED SINCE THE PREVIOUS RUN, WHICH MAY INDICATE A GRADUAL DRIFT MORE TOWARDS THE OTHER MODELS. BEYOND TAU 72, THE JTWC TRACK HAS BEEN SLOWED SIGNIFICANTLY, WITH THE TAU 120 POSITION NOW PLACED NEAR THE SAME LATITUDE AS THE PREVIOUS TAU 96 POSITION AND SHIFTED SOUTH. IN EITHER SCENARIO, THE SYSTEM WILL BEGIN TO UNDERGO EXTRA-TROPICAL TRANSITION (ETT) NEAR TAU 72, AS IT BEGINS TO INTERACT WITH UPPER-LEVEL WESTERLY FLOW AND THE BAROCLINIC ZONE ASSOCIATED WITH THE APPROACHING COLD FRONT. ETT SHOULD BE COMPLETE BY TAU 120 AS THE SYSTEM MOVES OFF THE EAST COAST OF JAPAN, BECOMING A COLD CORE LOW WITH AN EXPANSIVE GALE FORCE WIND FIELD. DUE TO THE HIGH DEGREE OF UNCERTAINTY ASSOCIATED WITH THE MULTIPLE MODEL SOLUTIONS THERE IS OVERALL LOW CONFIDENCE IN JTWC TRACK FORECAST.// NNNN