WTXS31 PGTW 012100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 18S (EIGHTEEN) WARNING NR 006// RMKS/ 1. TROPICAL CYCLONE 18S (EIGHTEEN) WARNING NR 006 01 ACTIVE TROPICAL CYCLONE IN SOUTHIO MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 011800Z --- NEAR 21.5S 117.1E MOVEMENT PAST SIX HOURS - 245 DEGREES AT 10 KTS POSITION ACCURATE TO WITHIN 025 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: 21.5S 117.1E --- FORECASTS: 12 HRS, VALID AT: 020600Z --- 22.3S 115.3E MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY VECTOR TO 24 HR POSIT: 245 DEG/ 06 KTS --- 24 HRS, VALID AT: 021800Z --- 22.8S 114.1E MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY VECTOR TO 36 HR POSIT: 270 DEG/ 03 KTS --- 36 HRS, VALID AT: 030600Z --- 22.8S 113.4E MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 000 NM NORTHEAST QUADRANT 010 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 010 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 295 DEG/ 03 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 031800Z --- 22.6S 112.9E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 070 NM NORTHEAST QUADRANT 020 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 060 NM NORTHWEST QUADRANT VECTOR TO 72 HR POSIT: 235 DEG/ 03 KTS --- 72 HRS, VALID AT: 041800Z --- 23.3S 111.9E MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 050 KT WINDS - 040 NM NORTHEAST QUADRANT 040 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 040 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 090 NM NORTHEAST QUADRANT 070 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 100 NM NORTHWEST QUADRANT VECTOR TO 96 HR POSIT: 180 DEG/ 04 KTS --- LONG RANGE OUTLOOK: --- 96 HRS, VALID AT: 051800Z --- 24.9S 111.9E MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 050 NM NORTHEAST QUADRANT 130 NM SOUTHEAST QUADRANT 110 NM SOUTHWEST QUADRANT 060 NM NORTHWEST QUADRANT VECTOR TO 120 HR POSIT: 165 DEG/ 09 KTS --- 120 HRS, VALID AT: 061800Z --- 28.5S 113.0E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 090 NM NORTHEAST QUADRANT 170 NM SOUTHEAST QUADRANT 140 NM SOUTHWEST QUADRANT 070 NM NORTHWEST QUADRANT --- REMARKS: 012100Z POSITION NEAR 21.7S 116.7E. 01FEB21. TROPICAL CYCLONE 18S (EIGHTEEN), LOCATED APPROXIMATELY 174 NM EAST-NORTHEAST OF LEARMONTH, AUSTRALIA, HAS TRACKED WEST- SOUTHWESTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. A 12-HR ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE SYSTEM CONTINUED TO MAINTAIN ITS CONVECTIVE STRUCTURE AS IT TRACKED OVER LAND ALONG THE COAST SOUTHWEST OF PORT HEADLAND AND TOWARD LEARMONTH. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A LOW LEVEL CIRCULATION FEATURE EVIDENT ON A COMPOSITE RADAR LOOP PORT HEDLAND THAT ALSO SHOWED MULTIPLE CONVECTIVE BANDS WRAPPING INTO THE WELL- DEFINED CENTER. THE INITIAL INTENSITY REMAINS ASSESSED AT 30 KNOTS BASED ON THE SUSTAINED EIR STRUCTURE AND EXTRAPOLATED FROM MULTIPLE SURFACE OBSERVATIONS ALONG THE COAST. UPPER-LEVEL ANALYSIS INDICATES NEAR-RADIAL OUTFLOW AND LOW VERTICAL WIND SHEAR (VWS). TC 18S WILL CONTINUE ON ITS CURRENT TRACK THROUGH TAU 24 UNDER THE STEERING INFLUENCE OF A LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) TO THE SOUTH, PASSING APPROXIMATELY 34NM SOUTH OF LEARMONTH AROUND 021500Z. AFTERWARD, AS THE TC EXITS INTO THE INDIAN OCEAN, THE STEERING PATTERN WILL BECOME MORE COMPLEX AS A SECONDARY STR BUILDING TO THE SOUTHWEST COMPETES FOR STEERING RESULTING IN A MOMENTARY WESTWARD TRACK TO TAU 48. AFTER TAU 48, THE PRIMARY STR RESUMES STEERING AS THE SECONDARY STR WEAKENS AND DRIVES THE TC SOUTHWESTWARD THEN SOUTHWARD. TC 18S IS EXPECTED TO MAINTAIN INTENSITY WHILE IT TRACKS OVER LAND BUT WILL INTENSIFY TO 35 KNOTS AFTER IT EXITS INTO THE WARM (28C) INDIAN OCEAN. THE WARM SST PLUS LOW VWS WILL PROMOTE STEADY INTENSIFICATION TO A PEAK OF 50 KNOTS BY TAU 72. AFTERWARD, COOLING SST AND INCREASING VWS WILL GRADUALLY ERODE THE SYSTEM DOWN TO 40KTS BY TAU 120. NUMERICAL MODELS ARE IN FAIRLY GOOD AGREEMENT WITH MINIMAL SPREADING TO 180NM BY TAU 120, LENDING FAIR CONFIDENCE TO THE JTWC TRACK FORECAST. NEXT WARNINGS AT 020300Z, 020900Z, 021500Z AND 022100Z.// NNNN