WTPS31 PGTW 182100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 05P (YASA) WARNING NR 026// RMKS/ 1. TROPICAL CYCLONE 05P (YASA) WARNING NR 026 01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 181800Z --- NEAR 20.3S 178.0W MOVEMENT PAST SIX HOURS - 180 DEGREES AT 08 KTS POSITION ACCURATE TO WITHIN 030 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 050 KT WINDS - 080 NM NORTHEAST QUADRANT 095 NM SOUTHEAST QUADRANT 075 NM SOUTHWEST QUADRANT 055 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 150 NM NORTHEAST QUADRANT 170 NM SOUTHEAST QUADRANT 145 NM SOUTHWEST QUADRANT 110 NM NORTHWEST QUADRANT REPEAT POSIT: 20.3S 178.0W --- FORECASTS: 12 HRS, VALID AT: 190600Z --- 21.5S 178.0W MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT WIND RADII VALID OVER OPEN WATER ONLY BECOMING SUBTROPICAL RADIUS OF 050 KT WINDS - 020 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 020 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 120 NM NORTHEAST QUADRANT 150 NM SOUTHEAST QUADRANT 130 NM SOUTHWEST QUADRANT 080 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 195 DEG/ 06 KTS --- 24 HRS, VALID AT: 191800Z --- 22.7S 178.4W MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT WIND RADII VALID OVER OPEN WATER ONLY BECOMING SUBTROPICAL RADIUS OF 050 KT WINDS - 010 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 000 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 100 NM NORTHEAST QUADRANT 130 NM SOUTHEAST QUADRANT 120 NM SOUTHWEST QUADRANT 070 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 210 DEG/ 06 KTS --- 36 HRS, VALID AT: 200600Z --- 23.7S 179.0W MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT WIND RADII VALID OVER OPEN WATER ONLY BECOMING SUBTROPICAL RADIUS OF 050 KT WINDS - 030 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 010 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 090 NM NORTHEAST QUADRANT 130 NM SOUTHEAST QUADRANT 110 NM SOUTHWEST QUADRANT 070 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 210 DEG/ 06 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 201800Z --- 24.7S 179.7W MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT WIND RADII VALID OVER OPEN WATER ONLY SUBTROPICAL RADIUS OF 034 KT WINDS - 070 NM NORTHEAST QUADRANT 130 NM SOUTHEAST QUADRANT 100 NM SOUTHWEST QUADRANT 060 NM NORTHWEST QUADRANT --- REMARKS: 182100Z POSITION NEAR 20.6S 178.0W. 18DEC20. TROPICAL CYCLONE (TC) 05P (YASA), LOCATED APPROXIMATELY 243 NM EAST-SOUTHEAST OF SUVA, FIJI, HAS TRACKED SOUTHWARD AT 08 KNOTS OVER THE PAST SIX HOURS. TC 05P HAS CONTINUED TO INTERACT WITH A BROAD UPPER-LEVEL TROUGH WITH STRONG (25 KNOTS) VERTICAL WIND SHEAR (VWS), WHICH HAS CONTRIBUTED TO THE STEADY WEAKENING. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS AN OBLONG AREA OF DEEP CONVECTION OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC) WITH WARMING CLOUD TOPS. AN 181845Z SSMIS 37V GHZ MICROWAVE IMAGE INDICATES A WELL-DEFINED LLCC WITH TIGHTLY-CURVED SHALLOW BANDING OVER THE NORTHERN SEMICIRCLE AND LIMITED DEEP CONVECTIVE BANDING OVER THE SOUTH QUADRANT. THIS IMAGE SUPPORTS THE INITIAL POSITION WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 60 KNOTS BASED ON THE LOWER END OF DVORAK CURRENT INTENSITY ESTIMATES RANGING FROM 3.5 TO 4.5 (55-77 KNOTS) AND AN ADT ESTIMATE OF 3.8 (60-65 KNOTS). TC 05P WILL TRACK SOUTHWARD TO SOUTH-SOUTHWESTWARD ALONG THE PERIPHERY OF THE SUBTROPICAL RIDGE TO THE NORTHEAST BUT WILL REMAIN EMBEDDED WITHIN THE DEEP UPPER-LEVEL TROUGH WITH INCREASING VWS (40- 60 KNOTS) AND COOLING SST VALUES (25C) AFTER TAU 18. TC 05P WILL BEGIN SUBTROPICAL TRANSITION NEAR TAU 12 AS IT APPROACHES THE SUBTROPICAL JET AND IS FORECAST TO COMPLETE SUBTROPICAL TRANSITION BY TAU 48 AS IT TRACKS UNDER THE AFOREMENTIONED JET AND THE WIND FIELD EXPANDS AND BECOMES HIGHLY ASYMMETRIC. STEADY WEAKENING IS ANTICIPATED, HOWEVER, THE SYSTEM WILL REMAIN A STRONG COLD-CORE LOW WITH 45-50 KNOT WINDS NEAR TAU 48. NUMERICAL MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT THROUGH TAU 24. AFTER TAU 24, NUMERICAL MODEL GUIDANCE DIVERGES WITH INCREASING UNCERTAINTY IN THE JTWC FORECAST TRACK DUE TO THE COMPLEX TRANSITION AND MERGER WITH THE UPPER-LEVEL TROUGH / LOW. THEREFORE, THERE IS MODERATE OVERALL CONFIDENCE IN THE JTWC FORECAST TRACK. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 181800Z IS 22 FEET. NEXT WARNINGS AT 190300Z, 190900Z, 191500Z AND 192100Z.// NNNN