WDXS33 PGTW 080900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 14S (TALIAH) WARNING NR 015// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 15.8S 95.9E INITIAL INTENSITY: 50 KTS GEOGRAPHIC REFERENCE: 224 NM SOUTH-SOUTHWEST OF THE COCOS ISLANDS MOVEMENT PAST 6 HOURS: WESTWARD AT 06 KTS SIGNIFICANT WAVE HEIGHT: 24 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TROPICAL CYCLONE (TC) 14S (TALIAH) CONTINUES TO STRUGGLE AGAINST PERSISTENT MODERATE EASTERLY SHEAR BUT THERE ARE EARLY SIGNS OF A CHANGE FORTHCOMING. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS CYCLING CONVECTION, WITH A DISSIPATING CONVECTIVE MASS TO THE EASTERN SIDE OF THE CIRCULATION BEING REPLACED BY A NEWLY DEVELOPING MASS OF CONVECTION OVER THE WESTERN SIDE. WHILE THE CONVECTIVE STRUCTURE REMAINS DISORGANIZED, THE LOW LEVEL CIRCULATION (LLC) REMAINS WELL-DEVELOPED, AS DEPICTED IN A 080253Z AMSU-B 89GHZ MICROWAVE IMAGE. THE MSI ALSO DEPICTS A BROAD REGION OF RELATIVELY DRY AND STABLE LOW-LEVEL STRATOCUMULUS CLOUDS ACROSS THE SOUTHERN AND WESTERN PERIPHERY OF THE LLC. THESE FEATURES ARE DEPICTED QUITE WELL BY THE 0800Z HAFS-A RUN AS WELL. THE INITIAL POSITION IS ASSESSED WITH LOW CONFIDENCE DUE TO THE LACK OF RECENT HIGH-RESOLUTION MICROWAVE IMAGERY AND OBSCURATION OF THE LLCC BY THE CONVECTIVE ACTIVITY. THE INITIAL INTENSITY IS BASED ON THE SUBJECTIVE AND OBJECTIVE ESTIMATES ABOVE, BUT WITH MEDIUM CONFIDENCE DUE THE CURRENT INTENSITY BEING IN THE RANGE WHEN DVORAK-BASED ESTIMATES OFTEN STRUGGLE AND THE LACK OF WIND SPEED MEASUREMENTS. THE ENVIRONMENT IS MARGINALLY FAVORABLE, WITH MODERATE EASTERLY SHEAR, MODERATE POLEWARD OUTFLOW AND WARM SSTS. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: NORTHEASTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED TO THE SOUTHWEST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.5 - 55 KTS KNES: T3.5 - 55 KTS DEMS: T3.5 - 55 KTS APRF: T3.0 - 45 KTS CIMSS ADT: 57 KTS AT 080600Z CIMSS AIDT: 45 KTS AT 080600Z CIMSS D-PRINT: 49 KTS AT 080600Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 15-20 KTS SST: 27-28 CELSIUS OUTFLOW: MODERATE POLEWARD OTHER FACTORS: RELATIVELY DRY, STABLE AIRMASS FLOWING NORTHWARD ALONG THE WESTERN AND SOUTHERN PERIPHERY OF THE CIRCULAION. ANALYSIS CONFIDENCE: INITIAL POSITION: LOW INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 14S WILL CONTINUE TO TRACK TOWARDS THE WEST FOR THE NEXT 12 TO 24 HOURS, THOUGH TRACK SPEEDS WILL BEGIN TO SLOW DOWN AS THE STR TO THE SOUTHWEST BUILDS NORTHWARD. AROUND TAU 24, TC 14S WILL BEGIN TO TRACK MORE EQUATORWARD, JUST HOW MUCH SO WILL DEPEND ON HOW FAR THE STR PUSHES NORTHWARD AND THE EXACT ORIENTATION OF THE RIDGE. REGARDLESS, TC 14S IS FORECAST TO TRACK SLOWLY EQUATORWARD FROM TAU 24 THROUGH TAU 48. AFTER TAU 48, THE STR TO THE SOUTHWEST BEGINS TO RAPIDLY WEAKEN AND MOVE WEST-SOUTHWESTWARD, INDUCING TC 14S POLEWARD. BY TAU 72, A NEW STR IS EXPECTED TO DEVELOP WEST OF LEARMONTH, AUSTRALIA, WHICH WILL ACCELERATE TC 14S TOWARDS THE WEAKNESS IN THE RIDGING PATTERN TO THE SOUTHWEST. IN TERMS OF INTENSITY, THE PRESENCE OF THE DRY, RELATIVELY STABLE AIRMASS TO THE WEST AND THE PERSISTENT MODERATE EASTERLY SHEAR WILL INHIBIT SIGNIFICANT INTENSIFICATION FOR THE NEXT 12-24 HOURS. DEEP-LAYER SHEAR IS FORECAST TO DROP-OFF SIGNIFICANTLY AFTER TAU 24, AND THE ATMOSPHERE IS EXPECTED MOISTEN, WHICH WILL ALLOW TC 14S TO STEADILY, AND POTENTIALLY RAPIDLY, INTENSIFY AFTER TAU 24. THE SYSTEM TAPS INTO A STRONG POLEWARD OUTFLOW CHANNEL AFTER TAU 72, WHICH WILL ALLOW FOR ADDITIONAL INTENSIFICATION FOR ABOUT 24 HOURS, BEFORE DECREASING SSTS, STRONG SHEAR AND DRY AIR ENTRAINMENT WILL BEGIN TO RAPIDLY WEAKEN THE SYSTEM. MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GENERAL AGREEMENT ON THE OVERALL TRACK SCENARIO BUT DIVERGES IN BOTH CROSS- AND ALONG-TRACK TERMS EARLY IN THE FORECAST RUN. THE GFS AND GEFS ARE THE SLOWEST AND MOST SOUTHERN OF THE AIDS THROUGH TAU 48, WHILE UKMET AND THE ENSEMBLE MEAN ARE THE MOST NORTHERN AND FASTEST. THE ECMWF, EEMN ENSEMBLE MEAN AND MULTI-MODEL CONSENSUS ARE GROUPED ROUGHLY IN THE MIDDLE OF THE EXTREMES TO TAU 48. ALL OF THE AIDS AGREE THAT THE SYSTEM TURNS POLEWARD BY TAU 60, BUT THEN SPREAD OUT RAPIDLY IMMEDIATELY THEREAFTER. CROSS-TRACK SPREAD IS 130NM AT TAU 72 AND INCREASES TO 340NM BY TAU 120, WITH NAVGEM ON THE EASTERN SIDE AND EGRR ON THE WEST. ENSEMBLE (GEFS AND ECENS) GUIDANCE SHOWS A HIGH DEGREE OF UNCERTAINTY THROUGHOUT THE FORECAST PERIOD, ESPECIALLY AFTER THE SYSTEM TURNS POLEWARD, WITH WELL OVER 1000NM SPREAD BETWEEN MEMBERS BY THE END OF THE FORECAST PERIOD. THE JTWC FORECAST MOST CLOSELY TRACKS THE ECMWF SOLUTION THROUGH THE ENTIRE FORECAST PERIOD WITH LOW CONFIDENCE DUE TO THE HIGH UNCERTAINTY IN BOTH THE DETERMINISTIC AND ENSEMBLE GUIDANCE. INTENSITY AIDS ALL INDICATE INTENSIFICATION AFTER TAU 12 TO TAU 24, WITH THE BULK OF THE GUIDANCE PEAKING BETWEEN 75-80 KNOTS BY TAU 96. THERE IS A 25 PERCENT CHANCE OF RAPID INTENSIFICATION IN THE NEXT 24-36 HOURS BASED ON THE CURRENT FRIA OUTPUT. FORECAST CONFIDENCE: TRACK 0 - 72 HR: LOW TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN