WTPS31 PGTW 170900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 05P (YASA) WARNING NR 020// RMKS/ 1. TROPICAL CYCLONE 05P (YASA) WARNING NR 020 01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 170600Z --- NEAR 16.5S 178.8E MOVEMENT PAST SIX HOURS - 115 DEGREES AT 12 KTS POSITION ACCURATE TO WITHIN 020 NM POSITION BASED ON EYE FIXED BY A COMBINATION OF SATELLITE AND RADAR PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 130 KT, GUSTS 160 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 055 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 045 NM SOUTHWEST QUADRANT 045 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 105 NM NORTHEAST QUADRANT 090 NM SOUTHEAST QUADRANT 080 NM SOUTHWEST QUADRANT 085 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 180 NM NORTHEAST QUADRANT 160 NM SOUTHEAST QUADRANT 145 NM SOUTHWEST QUADRANT 150 NM NORTHWEST QUADRANT REPEAT POSIT: 16.5S 178.8E --- FORECASTS: 12 HRS, VALID AT: 171800Z --- 17.7S 179.5W MAX SUSTAINED WINDS - 115 KT, GUSTS 140 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 040 NM NORTHEAST QUADRANT 030 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 030 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 070 NM NORTHEAST QUADRANT 070 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 060 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 170 NM NORTHEAST QUADRANT 160 NM SOUTHEAST QUADRANT 140 NM SOUTHWEST QUADRANT 130 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 145 DEG/ 09 KTS --- 24 HRS, VALID AT: 180600Z --- 19.2S 178.3W MAX SUSTAINED WINDS - 100 KT, GUSTS 125 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 030 NM NORTHEAST QUADRANT 030 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 030 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 060 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 050 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 160 NM NORTHEAST QUADRANT 160 NM SOUTHEAST QUADRANT 140 NM SOUTHWEST QUADRANT 110 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 150 DEG/ 07 KTS --- 36 HRS, VALID AT: 181800Z --- 20.4S 177.6W MAX SUSTAINED WINDS - 085 KT, GUSTS 105 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 020 NM NORTHEAST QUADRANT 020 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 010 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 060 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 050 NM SOUTHWEST QUADRANT 050 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 150 NM NORTHEAST QUADRANT 160 NM SOUTHEAST QUADRANT 140 NM SOUTHWEST QUADRANT 100 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 175 DEG/ 07 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 190600Z --- 21.7S 177.5W MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 010 NM NORTHEAST QUADRANT 020 NM SOUTHEAST QUADRANT 020 NM SOUTHWEST QUADRANT 010 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 050 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 050 NM SOUTHWEST QUADRANT 040 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 140 NM NORTHEAST QUADRANT 150 NM SOUTHEAST QUADRANT 130 NM SOUTHWEST QUADRANT 090 NM NORTHWEST QUADRANT VECTOR TO 72 HR POSIT: 205 DEG/ 04 KTS --- 72 HRS, VALID AT: 200600Z --- 23.2S 178.3W MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 050 KT WINDS - 010 NM NORTHEAST QUADRANT 030 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 020 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 090 NM NORTHEAST QUADRANT 130 NM SOUTHEAST QUADRANT 120 NM SOUTHWEST QUADRANT 070 NM NORTHWEST QUADRANT VECTOR TO 96 HR POSIT: 230 DEG/ 05 KTS --- LONG RANGE OUTLOOK: --- 96 HRS, VALID AT: 210600Z --- 24.6S 180.0E MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT WIND RADII VALID OVER OPEN WATER ONLY BECOMING SUBTROPICAL RADIUS OF 034 KT WINDS - 090 NM NORTHEAST QUADRANT 150 NM SOUTHEAST QUADRANT 120 NM SOUTHWEST QUADRANT 080 NM NORTHWEST QUADRANT VECTOR TO 120 HR POSIT: 240 DEG/ 07 KTS --- 120 HRS, VALID AT: 220600Z --- 26.0S 177.5E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY SUBTROPICAL RADIUS OF 034 KT WINDS - 090 NM NORTHEAST QUADRANT 150 NM SOUTHEAST QUADRANT 120 NM SOUTHWEST QUADRANT 080 NM NORTHWEST QUADRANT --- REMARKS: 170900Z POSITION NEAR 16.8S 179.2E. 17DEC20. TROPICAL CYCLONE 05P (YASA), LOCATED APPROXIMATELY 99 NM NORTH-NORTHEAST OF SUVA, FIJI, HAS TRACKED EAST-SOUTHEASTWARD AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) REVEALS DEEP CONVECTIVE BANDS WRAPPING INTO A 12 NM EYE, MAKING LANDFALL AT THIS HOUR ON THE NORTHWEST COAST OF VAUA LEVU. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE WELL DEFINED 12NM EYE IN THE IR AND MSI IMAGERY, SUPPORTED BY RADAR DATA FROM FIJI. THE INITIAL INTENSITY OF 130 KTS IS ASSESSED WITH MODERATE CONFIDENCE, BASED ON AN AVERAGE OF DVORAK CURRENT INTENSITY ESTIMATES OF T6.5-7.0 (127-140 KTS, KNES AND PGTW) AND AN ADT OF 6.0 (115 KTS). ENVIRONMENTAL ANALYSIS REVEALS AN OVERALL FAVORABLE ENVIRONMENT CHARACTERIZED BY WARM (28-29 CELSIUS) SEA SURFACE TEMPERATURES (SST), MODERATE TO HIGH (20-25 KTS) WESTERLY VERTICAL WIND SHEAR (VWS), AND ROBUST POLEWARD OUTFLOW ALOFT OFFSETTING THE VWS SOMEWHAT. THE SYSTEM IS TRACKING SOUTHEASTWARD ALONG THE WESTERN PERIPHERY OF AN UPPER-LEVEL RIDGE PATTERN EXTENDING FROM NEAR THE EQUATOR TO 20 DEG SOUTH LONGITUDE. AFTER MAKING LANDFALL AND TRANSITING ACROSS VANUA LEVU, THE SYSTEM IS FORECAST TO CONTINUE TRACKING SOUTHEASTWARD WHILE STEADILY WEAKENING DUE TO TERRAIN INTERACTION AND DISRUPTION OF THE LOW-LEVEL INFLOW, COMBINED WITH THE MODERATE VWS. BETWEEN TAUS 24-36, A DEEP MIDLATITUDE TROUGH APPROACHES FROM THE WEST, AND ERODES THE SOUTHERN PORTION OF THE STEERING RIDGE, CAUSING TC 05P TO SLOW AND TRACK GENERALLY SOUTHWARD THROUGH TAU 48. AS THE TROUGH PASSES TO THE SOUTH, A STRONG TRANSITORY RIDGE DEVELOPS JUST NORTH OF NEW ZEALAND, AND BECOMES THE DOMINATE STEERING MECHANISM, SHIFTING TC 05P ONTO A SOUTHWESTWARD COURSE THROUGH THE REMAINDER OF THE FORECAST PERIOD. AT THE SAME TIME, A 200MB TROUGH MOVES IN OVER TOP OF THE SYSTEM, WHICH WILL PROVIDE A KICK OF POLEWARD OUTFLOW, BUT WILL BE OFFSET BY DRAMATICALLY HIGHER VWS, SERVING TO STEADILY WEAKEN THE SYSTEM, REACHING 40 KNOTS BY TAU 120. BY TAU 96, THE SYSTEM WILL BE OVER COOL (24-25C) WATERS, AND AS IT MOVES UNDER THE 200MB TROUGH, WILL START THE TRANSITION TO A SUBTROPICAL SYSTEM, COMPLETING THE TRANSITION BY TAU 120. NUMERICAL GUIDANCE IS IN POOR AGREEMENT OVERALL, WITH ALL MODELS AGREEING ON THE TRACK THROUGH TAU 36, WITH SIGNIFICANT UNCERTAINTY AND BIFURCATION THEREAFTER. THE ECMWF AND NAVGEM SOLUTIONS REMAIN THE EASTERN OUTLIERS, TAKING THE SYSTEM EAST TO THE SOUTH OF TONGA AFTER TAU 72, WITH THE ECMWF SHOWING THE SYSTEM BECOMING QUASI-STATIONARY AFTER TAU 72. MEANWHILE, THE GFS, GALWEM AND THEIR ENSEMBLES TAKE THE SYSTEM RAPIDLY WEST AFTER TAU 96, ALONG THE SOUTHERN PERIPHERY OF THE AFOREMENTIONED TRANSITORY RIDGE, GENERATING A 620NM SPREAD AT TAU 120. THE JTWC FORECAST LIES CLOSE TO THE CONSENSUS TRACK THROUGH TAU 36, THEN JUST WEST AND SLIGHTLY SLOWER THAN THE CONSENSUS THROUGH THE REMAINDER OF THE FORECAST, FAVORING THE GFS SOLUTION IN THE LATER TAUS. DUE TO VERY HIGH UNCERTAINTY AND BIFURCATION IN THE MODEL GUIDANCE IN THE LATER TAUS, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK THROUGH TAU 36, AND LOW CONFIDENCE THROUGH THE REMAINDER OF THE FORECAST. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 170600Z IS 38 FEET. NEXT WARNINGS AT 171500Z, 172100Z, 180300Z AND 180900Z.// NNNN