WTPS31 PGTW 181500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 05P (YASA) WARNING NR 025// RMKS/ 1. TROPICAL CYCLONE 05P (YASA) WARNING NR 025 01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 181200Z --- NEAR 19.7S 177.9W MOVEMENT PAST SIX HOURS - 160 DEGREES AT 08 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 050 NM NORTHEAST QUADRANT 055 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 040 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 090 NM NORTHEAST QUADRANT 105 NM SOUTHEAST QUADRANT 080 NM SOUTHWEST QUADRANT 065 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 175 NM NORTHEAST QUADRANT 185 NM SOUTHEAST QUADRANT 145 NM SOUTHWEST QUADRANT 125 NM NORTHWEST QUADRANT REPEAT POSIT: 19.7S 177.9W --- FORECASTS: 12 HRS, VALID AT: 190000Z --- 20.8S 177.5W MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT WIND RADII VALID OVER OPEN WATER ONLY BECOMING SUBTROPICAL RADIUS OF 064 KT WINDS - 020 NM NORTHEAST QUADRANT 030 NM SOUTHEAST QUADRANT 020 NM SOUTHWEST QUADRANT 000 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 050 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 050 NM SOUTHWEST QUADRANT 030 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 140 NM NORTHEAST QUADRANT 160 NM SOUTHEAST QUADRANT 130 NM SOUTHWEST QUADRANT 090 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 180 DEG/ 06 KTS --- 24 HRS, VALID AT: 191200Z --- 21.9S 177.5W MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT WIND RADII VALID OVER OPEN WATER ONLY BECOMING SUBTROPICAL RADIUS OF 050 KT WINDS - 030 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 050 NM SOUTHWEST QUADRANT 020 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 120 NM NORTHEAST QUADRANT 140 NM SOUTHEAST QUADRANT 110 NM SOUTHWEST QUADRANT 080 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 205 DEG/ 06 KTS --- 36 HRS, VALID AT: 200000Z --- 22.9S 178.0W MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT WIND RADII VALID OVER OPEN WATER ONLY BECOMING SUBTROPICAL RADIUS OF 050 KT WINDS - 020 NM NORTHEAST QUADRANT 040 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 010 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 090 NM NORTHEAST QUADRANT 130 NM SOUTHEAST QUADRANT 100 NM SOUTHWEST QUADRANT 070 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 210 DEG/ 09 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 201200Z --- 24.4S 179.0W MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT WIND RADII VALID OVER OPEN WATER ONLY SUBTROPICAL RADIUS OF 034 KT WINDS - 080 NM NORTHEAST QUADRANT 120 NM SOUTHEAST QUADRANT 100 NM SOUTHWEST QUADRANT 060 NM NORTHWEST QUADRANT --- REMARKS: 181500Z POSITION NEAR 20.0S 177.8W. 18DEC20. TROPICAL CYCLONE 05P (YASA), LOCATED APPROXIMATELY 231 NM EAST-SOUTHEAST OF SUVA, FIJI, HAS TRACKED SOUTH-SOUTHEASTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP CONVECTION OBSCURING A LOW LEVEL CIRCULATION CENTER WITH POLEWARD OUTFLOW FEEDING INTO AN UPPER LEVEL JET. THE INITIAL POSITION IS PLACED WITH HIGH CERTAINTY BASED ON SPIRAL BANDING WRAPPING INTO THE LOW LEVEL CIRCULATION IN THE EIR LOOP AND AN 181248Z AMSR2 36GHZ IMAGE. THE INITIAL INTENSITY OF 70 KNOTS IS ASSESSED WITH MODERATE CONFIDENCE BASED ON AN AVERAGE OF MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T4.0 (65 KTS, PGTW AND PHFO) AND T4.5 (77 KTS, KNES). ENVIRONMENTAL ANALYSIS REVEALS A MARGINAL ENVIRONMENT CHARACTERIZED BY WARM(26-27C) SEA SURFACE TEMPERATURES (SST) AND ROBUST POLEWARD OUTFLOW ALOFT, OFFSET BY MODERATE (15-25 KTS) VERTICAL WIND SHEAR (VWS), AND CONVERGENT UPPER LEVEL FLOW ALONG THE NORTHERN PERIPHERY OF THE SYSTEM. THE SYSTEM IS TRACKING ALONG THE PERIPHERY OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST. IN THE NEAR TERM, THE STEERING RIDGE WILL REPOSITION DUE TO INTERACTION WITH AN AMPLIFYING MIDLATITUDE TROUGH POSITIONED TO THE SOUTHWEST. THIS INTERACTION, COUPLED WITH THE BUILDING OF A STRONG TRANSITORY RIDGE NORTH OF NEW ZEALAND, WILL CAUSE THE STORM TRACK TO BECOME SOUTHWARD AFTER TAU 12 AND THEN SOUTHWESTWARD AFTER TAU 24. ENVIRONMENTAL CONDITIONS WILL CONTINUE TO DEGRADE THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD WITH VWS INCREASING TO 30+ KTS BY TAU 24 AND COOL (< 26 CELSIUS) SST BY TAU 36. VWS IS THEN FORECAST TO FURTHER INCREASE AS THE SYSTEM TRACKS FURTHER POLEWARD AND UNDERNEATH STRONG WESTERLY FLOW ALOFT. AS A RESULT, TC YASA WILL WEAKEN AND BEGIN SUBTROPICAL TRANSITION BY TAU 12. THEREAFTER, THE SYSTEM WILL CONTINUE TO WEAKEN AS THE WIND FIELD EXPANDS AND BECOMES ASYMMETRIC AND BY TAU 48, TC YASA WILL COMPLETE SUBTROPICAL TRANSITION. NUMERICAL MODEL GUIDANCE HAS CONVERGED OVER THE PAST SIX HOURS AND IS GOOD AGREEMENT THROUGHOUT THE FORECAST PERIOD. THIS LENDS OVERALL FAIR CONFIDENCE IN THE JTWC FORECAST TRACK WHICH IS PLACED SLIGHTLY EAST OF THE MULTI-MODEL CONSENSUS. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 181200Z IS 23 FEET. NEXT WARNINGS AT 182100Z, 190300Z, 190900Z AND 191500Z.// NNNN