WDXS32 PGTW 152100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 06S (SIX) WARNING NR 002// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 9.5S 93.9E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 240 NM NORTHWEST OF COCOS ISLANDS MOVEMENT PAST 6 HOURS: EASTWARD AT 02 KTS SIGNIFICANT WAVE HEIGHT: 17 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL CYCLONE (TC) 06S (SIX) CONTINUING TO DEVELOP AS IT VERY SLOWLY TRACKS EASTWARD OVER THE PAST 12 HOURS. CENTRALIZED DEEP CONVECTION PERSISTS AND FORMATIVE SPIRAL BANDS OF DEEP CONVECTION ARE OBSERVED THROUGHOUT THE NORTHERN PERIPHERY OF THE SYSTEM. OUTFLOW ALOFT REMAINS CONDUCIVE FOR DEVELOPMENT, WITH EVIDENCE OF CIRRUS FILAMENTS DRIFTING BOTH EQUATORWARD AND POLEWARD ON ANIMATED EIR SATELLITE IMAGERY. WIND SHEAR IS FORECAST TO REMAIN LOW TO MODERATE (10-20 KTS) THROUGH TAU 96, WITH SUPPORTIVE SEA SURFACE TEMPERATURES (28-29 C) OVER THE SAME INTERVAL. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON A 151544Z METOP-B SCATTEROMETER IMAGE. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED SCATTEROMETRY IMAGE, AS WELL AS THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: WEAK NEAR-EQUATORIAL RIDGE (NER) TO THE NORTH AND A WEAK SUBTROPICAL RIDGE (STR) TO THE SOUTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS KNES: T3.0 - 45 KTS DEMS: T2.5 - 35 KTS APRF: T3.0 - 45 KTS CIMSS SATCON: 50 KTS AT 151700Z CIMSS DPRINT: 51 KTS AT 151800Z CIMSS ADT: 34 KTS AT 151730Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE POLEWARD AND EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 06S HAS BEGUN AN EASTWARD JAUNT AND WILL CONTINUE TO TRACK EASTWARD AT VERY SLOW TRACK SPEEDS OVER THE NEXT 12 TO 24 HOURS DUE TO A COMPETING STEERING ENVIRONMENT WITH RIDGING PREVALENT TO BOTH THE NORTH AND SOUTH. NEAR TAU 24, THE TC IS FORECAST TO SLOWLY TRACK SOUTHEASTWARD THROUGH TAU 36, AND EVENTUALLY COME TO A SOUTHWARD TRACK BY TAU 48. THE INTERVAL BETWEEN TAU 24 AND TAU 72 OFFERS THE MOST FAVORABLE CONDITIONS FOR TC INTENSIFICATION TO OCCUR, WITH INTENSITY PEAKING NEAR 65KTS AROUND TAU 60. FOLLOWING THE INTENSITY PEAK (TAU 72), SEA SURFACE TEMPERATURES BEGIN TO DROP AND VERTICAL WIND SHEAR INCREASES TO MODERATE LEVELS (20-25KTS) THROUGH TAU 120. AT TAU 72, AND AS ALLUDED TO IN THE MODEL DISCUSSION, A BIFURCATION BECOMES EVIDENT IN MODEL GUIDANCE. PRIMARILY, THIS IS DUE TO HOW DIFFERENT MODELS ARE RESOLVING THE WEAK STR TO THE SOUTH. SOME MODEL SOLUTIONS, SUCH AS ECMWF, SUGGEST THE RIDGE PROPAGATES EASTWARD, ALLOWING TC 06S TO TRACK ALONG THE WESTERN PERIPHERY OF THE RIDGE, RESULTING IN A SOUTHWESTWARD TRACK. OTHERS, LIKE THE GFS SOLUTION, KEEP THE STR QUASISTATIONARY TO THE SOUTH-SOUTHWEST OF TC 06S, RESULTING IN A MORE SOUTH-SOUTHEASTWARD TRACK THROUGH TAU 120. MODEL DISCUSSION: GLOBAL NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THAT TC 06S (SIX) WILL CONTINUE TO GRADUALLY AND SLOWLY TRACK EASTWARD OVER THE NEXT TWELVE HOURS. OVER THIS PERIOD, THE GFS AND HAFS-A SOLUTIONS EXHIBIT A SLIGHTLY FASTER TRACK SPEED, BRINGING THE LLCC AS FAR EAST AS 95E. AT THIS POINT (TAU 24), MODELS INDICATE THE SYSTEM WITH SLOWLY TURN TO A SOUTHEASTWARD COURSE (TAU 24 TO TAU 36) FOLLOWED BY A SOUTHWARD TRACK (TAU 48 TO TAU 27). BETWEEN TAU 24 AND TAU 72 IS WHEN INTENSITY GUIDANCE SUGGESTS INTENSIFICATION WILL STEADILY OCCUR, PEAKING NEAR TAU 60 AT 65KTS. HOWEVER, THERE IS A LARGE SPREAD (30 KTS) IN INTENSITY GUIDANCE AT TAU 60, LEAVING MODERATE (MEDIUM) UNCERTAINTY IN THE FORECAST. AFTER TAU 72, MODELS CONTINUE TO DIVERGE AND CREATE A BIFURCATION. THE GFS AND UKMET DETERMINISTIC AND ENSEMBLE MEAN SOLUTIONS SUGGEST THE TRACK WITH STEER SOUTHEASTWARD TO EASTWARD FORWARD OF TAU 72, WHILE THE REMAINING MEMBERS OF THE JTWC CONCENSUS STEER THE SYSTEM SOUTHWESTWARD TO WESTWARD. DUE TO THE LARGE UNCERTAINTY PRESENTED, THE FORECAST CONFIDENCE OF THE LATER INTERVAL IS LOW. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN