WTXS31 PGTW 312100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 18S (EIGHTEEN) WARNING NR 002// RMKS/ 1. TROPICAL CYCLONE 18S (EIGHTEEN) WARNING NR 002 01 ACTIVE TROPICAL CYCLONE IN SOUTHIO MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 311800Z --- NEAR 21.3S 119.8E MOVEMENT PAST SIX HOURS - 275 DEGREES AT 12 KTS POSITION ACCURATE TO WITHIN 050 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY REPEAT POSIT: 21.3S 119.8E --- FORECASTS: 12 HRS, VALID AT: 010600Z --- 21.5S 117.7E MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY VECTOR TO 24 HR POSIT: 255 DEG/ 09 KTS --- 24 HRS, VALID AT: 011800Z --- 22.0S 115.8E MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY VECTOR TO 36 HR POSIT: 250 DEG/ 08 KTS --- 36 HRS, VALID AT: 020600Z --- 22.6S 114.1E MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY VECTOR TO 48 HR POSIT: 245 DEG/ 06 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 021800Z --- 23.1S 112.9E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 080 NM NORTHEAST QUADRANT 010 NM SOUTHEAST QUADRANT 010 NM SOUTHWEST QUADRANT 090 NM NORTHWEST QUADRANT VECTOR TO 72 HR POSIT: 275 DEG/ 04 KTS --- 72 HRS, VALID AT: 031800Z --- 22.9S 111.2E MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 050 KT WINDS - 020 NM NORTHEAST QUADRANT 040 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 030 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 100 NM NORTHEAST QUADRANT 050 NM SOUTHEAST QUADRANT 050 NM SOUTHWEST QUADRANT 130 NM NORTHWEST QUADRANT VECTOR TO 96 HR POSIT: 240 DEG/ 04 KTS --- LONG RANGE OUTLOOK: --- 96 HRS, VALID AT: 041800Z --- 23.6S 109.8E MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 030 NM NORTHEAST QUADRANT 070 NM SOUTHEAST QUADRANT 080 NM SOUTHWEST QUADRANT 050 NM NORTHWEST QUADRANT VECTOR TO 120 HR POSIT: 185 DEG/ 05 KTS --- 120 HRS, VALID AT: 051800Z --- 25.6S 109.6E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 070 NM NORTHEAST QUADRANT 140 NM SOUTHEAST QUADRANT 120 NM SOUTHWEST QUADRANT 080 NM NORTHWEST QUADRANT --- REMARKS: 312100Z POSITION NEAR 21.4S 119.3E. 31JAN21. TROPICAL CYCLONE (TC) 18S (EIGHTEEN), LOCATED APPROXIMATELY 90 NM SOUTHEAST OF PORT HEDLAND, AUSTRA, HAS TRACKED WESTWARD AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS SPIRAL BANDS OF CONVECTION WRAPPING INTO A WELL DEFINED MID-LEVEL CIRCULATION CENTER. THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON THE CONVECTIVE FEATURES IN THE EIR LOOP AND BANDING FOUND IN THE 311728Z ATMS 88GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY IS ASSESSED AT 30 KTS BASED ON MULTIPLE SURFACE OBSERVATIONS, RANGING FROM 996MB-999MB, SURROUNDING THE SYSTEM CENTER. TC 18S IS TRACKING OVER LAND THROUGH WESTERN AUSTRALIA, HOWEVER, THE ENVIRONMENT IS OVERALL MARGINALLY FAVORABLE WITH LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS) AND MODERATE UPPER LEVEL OUTFLOW ALOFT. THE PRIMARY STEERING MECHANISM IS A SUBTROPICAL RIDGE (STR) POSITIONED TO THE SOUTHWEST, IN ADDITION TO A SECONDARY STR TO THE SOUTHEAST. TC 18S IS FORECAST TO CONTINUE TRACKING OVER WESTERN AUSTRALIA, PASSING WITHIN 22NM OF LEARMONTH, AUSTRALIA, AND INTENSIFY TO 40 KTS BY TAU 48 WHEN IT HAS MOVED INTO THE INDIAN OCEAN. THE SYSTEM IS EXPECTED TO INTENSIFY UP TO 50 KNOTS BY TAU 72 DUE TO WARM (27-28 DEGREES CELSIUS) SEA SURFACE TEMPERATURES, COUPLED WITH CONTINUED LOW VWS AND MODERATEALY FAVORABLE UPPER LEVEL SUPPORT. THEREAFTER, MODERATE TO HIGH (20-25 KTS) VWS AND COOLER (25- 26 DEGREES CELSIUS) SST WILL LEAD TO A GRADUAL WEAKENING TREND WITH TC 18S, TRACKING SOUTHWARD AFTER TAU 96 ALONG THE WESTERN PERIPHERY OF THE STEERING STR TO THE EAST. NUMERICAL MODEL SOLUTIONS ARE IN GOOD AGREEMENT, ON THE GENERALLY WESTWARD TRACK THROUGH TAU 96 BUT DIVERGE SLIGHTLY ON THE TIMING OF THE SOUTHWARD TURN THEREAFTER. THIS GOOD AGREEMENT IN NUMERICAL MODEL SOLUTIONS LENDS OVERALL HIGH CONFIDENCE IN THE JTWC FORECAST TRACK WHICH IS PLACED ON THE MULTI- MODEL CONSENSUS. NEXT WARNINGS AT 010300Z, 010900Z, 011500Z AND 012100Z.// NNNN