WTXS31 PGTW 072100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 21S (IKOLA) WARNING NR 005// RMKS/ 1. TROPICAL CYCLONE 21S (IKOLA) WARNING NR 005 02 ACTIVE TROPICAL CYCLONES IN SOUTHIO MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 071800Z --- NEAR 20.4S 96.0E MOVEMENT PAST SIX HOURS - 135 DEGREES AT 17 KTS POSITION ACCURATE TO WITHIN 040 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 080 KT, GUSTS 100 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 020 NM NORTHEAST QUADRANT 025 NM SOUTHEAST QUADRANT 025 NM SOUTHWEST QUADRANT 020 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 035 NM NORTHEAST QUADRANT 045 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 035 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 095 NM NORTHEAST QUADRANT 115 NM SOUTHEAST QUADRANT 110 NM SOUTHWEST QUADRANT 095 NM NORTHWEST QUADRANT REPEAT POSIT: 20.4S 96.0E --- FORECASTS: 12 HRS, VALID AT: 080600Z --- 23.1S 99.2E MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 050 KT WINDS - 035 NM NORTHEAST QUADRANT 040 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 035 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 095 NM NORTHEAST QUADRANT 110 NM SOUTHEAST QUADRANT 110 NM SOUTHWEST QUADRANT 095 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 135 DEG/ 20 KTS --- 24 HRS, VALID AT: 081800Z --- 25.8S 102.3E MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 090 NM NORTHEAST QUADRANT 105 NM SOUTHEAST QUADRANT 105 NM SOUTHWEST QUADRANT 090 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 135 DEG/ 21 KTS --- 36 HRS, VALID AT: 090600Z --- 28.6S 105.8E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER RADIUS OF 034 KT WINDS - 070 NM NORTHEAST QUADRANT 080 NM SOUTHEAST QUADRANT 080 NM SOUTHWEST QUADRANT 070 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 140 DEG/ 24 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 091800Z --- 32.3S 109.3E MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER --- REMARKS: 072100Z POSITION NEAR 21.1S 96.8E. TROPICAL CYCLONE (TC) 21S (IKOLA), LOCATED APPROXIMATELY 1017 NM WEST OF LEARMONTH, AUSTRALIA HAS TRACKED SOUTHEASTWARD AT 17 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A RAPIDLY DETERIORATING STRUCTURE WITH THE BULK OF CONVECTION DISPLACED SOUTHEAST OF A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC). A 071626Z TRMM 85GHZ MICROWAVE IMAGE FURTHER DEPICTS THE PARTIALLY EXPOSED LLCC WITH THE WEAKENING CONVECTION SHEARED TO THE SOUTHEAST. THE INITIAL POSITION IS BASED ON THE PARTIALLY EXPOSED LLCC IN THE AFOREMENTIONED IMAGERY AND FURTHER REFINED AFTER CONDUCTING AN AMBIGUITY ANALYSIS OF A 071550Z SCATTEROMETER PASS WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS BASED ON AN ASSESSMENT OF DVORAK INTENSITY ESTIMATES FROM ALL REPORTING AGENCIES AND REPRESENTS THE WEAKENING NATURE OF THE CYCLONE. UPPER LEVEL ANALYSIS INDICATES A POOR ENVIRONMENT WITH THE SYSTEM UNDER THE MID-LATITUDE TROUGH; ADVECTING DRY AIR INTO THE CIRCULATION AND PRODUCING HIGH (30-40 KNOT) NORTHWESTERLY VERTICAL WIND SHEAR (VWS). IN ADDITION, TC 21S HAS MOVED INTO SEA SURFACE TEMPERATURES (SSTS) BELOW 26 CELSIUS. TC IKOLA IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF THE NEAR EQUATORIAL RIDGE TO THE NORTHEAST. TC 21S WILL REMAIN ON A SOUTHEASTWARD TRAJECTORY UNDER THE INFLUENCE OF THIS STEERING RIDGE. THE COMBINED EFFECTS OF INCREASING VWS AND FURTHER DECREASING SSTS WILL CONTINUE TO RAPIDLY WEAKEN THE SYSTEM, LEADING TO COMPLETE DISSIPATION BY TAU 48. DYNAMIC MODEL GUIDANCE REMAINS IN VERY TIGHT AGREEMENT LENDING TO HIGH CONFIDENCE IN THE JTWC FORECAST. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 071800Z IS 32 FEET. NEXT WARNINGS AT 080900Z AND 082100Z. REFER TO TROPICAL CYCLONE 22S (JOALANE) WARNINGS (WTXS32 PGTW) FOR TWELVE-HOURLY UPDATES.//