WTXS31 PGTW 010900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 18S (EIGHTEEN) WARNING NR 004// RMKS/ 1. TROPICAL CYCLONE 18S (EIGHTEEN) WARNING NR 004 01 ACTIVE TROPICAL CYCLONE IN SOUTHIO MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 010600Z --- NEAR 20.6S 119.0E MOVEMENT PAST SIX HOURS - 285 DEGREES AT 04 KTS POSITION ACCURATE TO WITHIN 015 NM POSITION BASED ON CENTER LOCATED BY A COMBINATION OF SATELLITE, RADAR AND SYNOPTIC DATA PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY REPEAT POSIT: 20.6S 119.0E --- FORECASTS: 12 HRS, VALID AT: 011800Z --- 21.0S 116.9E MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY VECTOR TO 24 HR POSIT: 250 DEG/ 08 KTS --- 24 HRS, VALID AT: 020600Z --- 21.6S 115.2E MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY VECTOR TO 36 HR POSIT: 240 DEG/ 05 KTS --- 36 HRS, VALID AT: 021800Z --- 22.1S 114.2E MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 030 NM NORTHEAST QUADRANT 035 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 030 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 255 DEG/ 06 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 030600Z --- 22.4S 113.0E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 030 NM NORTHEAST QUADRANT 035 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 030 NM NORTHWEST QUADRANT VECTOR TO 72 HR POSIT: 275 DEG/ 04 KTS --- 72 HRS, VALID AT: 040600Z --- 22.2S 111.3E MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 020 NM NORTHEAST QUADRANT 070 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 020 NM NORTHWEST QUADRANT VECTOR TO 96 HR POSIT: 200 DEG/ 04 KTS --- LONG RANGE OUTLOOK: --- 96 HRS, VALID AT: 050600Z --- 23.6S 110.7E MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 050 KT WINDS - 000 NM NORTHEAST QUADRANT 020 NM SOUTHEAST QUADRANT 020 NM SOUTHWEST QUADRANT 000 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 040 NM NORTHEAST QUADRANT 110 NM SOUTHEAST QUADRANT 110 NM SOUTHWEST QUADRANT 050 NM NORTHWEST QUADRANT VECTOR TO 120 HR POSIT: 165 DEG/ 04 KTS --- 120 HRS, VALID AT: 060600Z --- 25.3S 111.2E MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 050 KT WINDS - 000 NM NORTHEAST QUADRANT 020 NM SOUTHEAST QUADRANT 020 NM SOUTHWEST QUADRANT 000 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 050 NM NORTHEAST QUADRANT 160 NM SOUTHEAST QUADRANT 150 NM SOUTHWEST QUADRANT 070 NM NORTHWEST QUADRANT --- REMARKS: 010900Z POSITION NEAR 20.7S 118.5E. 01FEB21. TROPICAL CYCLONE (TC) 18S (EIGHTEEN), LOCATED APPROXIMATELY 29 NM SOUTHEAST OF PORT HEDLAND, AUSTRALIA, HAS TRACKED WEST- NORTHWESTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS LOW-LEVEL CLOUD LINES WRAPPING INTO A WELL-DEFINED, EXPOSED LOW-LEVEL CIRCULATION CENTER. ANIMATED RADAR IMAGERY FROM THE PORT HEDLAND RADAR INDICATES A WELL- ORGANIZED SYSTEM WITH MULTIPLE CONVECTIVE BANDS WRAPPING INTO THE WELL-DEFINED CENTER. THUS, THERE IS HIGH CONFIDENCE IN THE INITIAL POSITION AND RECENT TRACK MOTION. A 010619Z PARTIAL AMSR2 89GHZ MICROWAVE IMAGE INDICATES FORMATIVE DEEP CONVECTIVE BANDING WRAPPING AROUND THE PERIPHERY. THE INITIAL INTENSITY REMAINS ASSESSED AT 30 KNOTS BASED ON THE CONVECTIVE STRUCTURE AND SURFACE OBSERVATIONS FROM PORT HEDLAND, WHICH IS REPORTING GUSTS OF 20-25 KNOTS WITH A SLP VALUE OF 994MB. UPPER-LEVEL ANALYSIS INDICATES NEAR-RADIAL OUTFLOW AND LOW VERTICAL WIND SHEAR. TC 18S IS FORECAST TO TRACK WEST-SOUTHWESTWARD THROUGH TAU 36 UNDER THE STEERING INFLUENCE OF A LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED OVER SOUTHWESTERN AUSTRALIA. AFTER TAU 36, THE STEERING PATTERN IS EXPECTED TO BECOME MORE COMPLEX WITH ANOTHER STR BUILDING WEST OF THE SYSTEM. CONSEQUENTLY, TC 18S SHOULD SLOW SIGNIFICANTLY UNTIL A BROAD TROUGH FORMS WEST OF AUSTRALIA, WHICH SHOULD DRIVE THE SYSTEM SLOWLY SOUTHWARD AFTER TAU 72. NUMERICAL MODEL GUIDANCE SUPPORTS THIS SCENARIO WITH FAIR CONFIDENCE AND WHILE ALL TRACKERS DEPICT THE SOUTHWARD TURN THERE ARE MAJOR DIFFERENCES IN THE TIMING AND LOCATION OF THIS SOUTHWARD TURN. DUE TO THIS COMPLEX, EVOLVING STEERING PATTERN, THERE IS MODERATE CONFIDENCE IN THE OVERALL JTWC FORECAST TRACK. TC 18S IS EXPECTED TO MAINTAIN INTENSITY WHILE IT TRACKS OVER LAND ALONG THE COAST BUT WILL INTENSIFY TO 35 KNOTS AS IT APPROACHES THE EXMOUTH PENINSULA AND LEARMONTH SOLAR OBSERVATORY. AFTER TAU 48, THE SYSTEM SHOULD GRADUALLY INTENSIFY TO A PEAK INTENSITY OF 50 KNOTS BY TAU 96 WITH FAVORABLE ENVIRONMENTAL CONDITIONS AND WARM SST. NEXT WARNINGS AT 011500Z, 012100Z, 020300Z AND 020900Z.// NNNN