WTPS32 PGTW 262100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE WARNING// RMKS/ 1. TROPICAL CYCLONE 17P (IRIS) WARNING NR 009 01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 261800Z --- NEAR 18.7S 158.1E MOVEMENT PAST SIX HOURS - 170 DEGREES AT 07 KTS POSITION ACCURATE TO WITHIN 045 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 100 NM NORTHEAST QUADRANT 090 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 035 NM NORTHWEST QUADRANT REPEAT POSIT: 18.7S 158.1E --- FORECASTS: 12 HRS, VALID AT: 270600Z --- 20.1S 158.4E MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 135 NM NORTHEAST QUADRANT 120 NM SOUTHEAST QUADRANT 050 NM SOUTHWEST QUADRANT 015 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 165 DEG/ 06 KTS --- 24 HRS, VALID AT: 271800Z --- 21.3S 158.8E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 155 NM NORTHEAST QUADRANT 145 NM SOUTHEAST QUADRANT 090 NM SOUTHWEST QUADRANT 005 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 150 DEG/ 04 KTS --- 36 HRS, VALID AT: 280600Z --- 22.0S 159.2E MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER RADIUS OF 034 KT WINDS - 130 NM NORTHEAST QUADRANT 200 NM SOUTHEAST QUADRANT 145 NM SOUTHWEST QUADRANT 005 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 280 DEG/ 04 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 281800Z --- 21.9S 158.4E MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER --- REMARKS: 262100Z POSITION NEAR 19.0S 158.2E. TROPICAL CYCLONE (TC) 17P (IRIS), LOCATED APPROXIMATELY 494 NM WEST-NORTHWEST OF NOUMEA, NEW CALEDONIA, HAS TRACKED SOUTHWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED SHORTWAVE INFRARED SATELLITE IMAGERY SHOWS FLARING CONVECTION OVER A WEAK, PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED ON THE 261800Z PGTW DVORAK FIX WITH FAIR CONFIDENCE. THE INITIAL INTENSITY IS CONSISTENT WITH THE PGTW DVORAK CURRENT INTENSITY OF T2.5 (35 KNOTS) AND SLIGHTLY ABOVE KNES AND OBJECTIVE INTENSITY ESTIMATES OF T1.5 TO T2.0. ENVIRONMENTAL ANALYSIS REVEALS MARGINAL CONDITIONS WITH LOW VERTICAL WIND SHEAR (VWS), GOOD POLEWARD OUTFLOW, POOR EQUATORWARD OUTFLOW, AND SEA SURFACE TEMPERATURES OF 27 TO 28 CELSIUS. TC 17P WILL CONTINUE TO TRACK ALONG THE WESTERN PERIPHERY OF THE NEAR EQUATORIAL RIDGE TO THE EAST UNTIL TAU 36. AT THAT POINT, A SUBTROPICAL RIDGE TO THE SOUTH WILL BECOME THE PRIMARY STEERING INFLUENCE AND THE CYCLONE WILL BEGIN A WESTWARD TRACK. THE SYSTEM WILL INTENSIFY SLIGHTLY UNDER MARGINALLY FAVORABLE CONDITIONS UNTIL TAU 24 WHEN CONVERGENCE IN THE UPPER LEVELS FROM AN APPROACHING UPPER LEVEL TROUGH CAUSES THE CYCLONE TO WEAKEN AND DISSIPATE BY TAU 48. NUMERICAL MODEL GUIDANCE GENERALLY AGREES ON THE SYSTEM TRACK BUT VARIES SIGNIFICANTLY IN THE TIMING AND SPEED OF THE WESTWARD TRACK SHIFT. THIS UNCERTAINTY LENDS LOW CONFIDENCE IN THE JTWC TRACK FORECAST. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 261800Z IS 14 FEET. NEXT WARNINGS AT 270300Z, 270900Z, 271500Z AND 272100Z.//