WTPS32 PGTW 041500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE WARNING// RMKS/ 1. TROPICAL CYCLONE 17P (IRIS) WARNING NR 022 01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 041200Z --- NEAR 19.5S 151.4E MOVEMENT PAST SIX HOURS - 120 DEGREES AT 04 KTS POSITION ACCURATE TO WITHIN 020 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 120 NM NORTHEAST QUADRANT 155 NM SOUTHEAST QUADRANT 135 NM SOUTHWEST QUADRANT 115 NM NORTHWEST QUADRANT REPEAT POSIT: 19.5S 151.4E --- FORECASTS: 12 HRS, VALID AT: 050000Z --- 19.7S 151.9E MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 065 NM NORTHEAST QUADRANT 145 NM SOUTHEAST QUADRANT 130 NM SOUTHWEST QUADRANT 070 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 090 DEG/ 00 KTS --- 24 HRS, VALID AT: 051200Z --- 19.7S 152.0E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 035 NM NORTHEAST QUADRANT 135 NM SOUTHEAST QUADRANT 140 NM SOUTHWEST QUADRANT 065 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 315 DEG/ 01 KTS --- 36 HRS, VALID AT: 060000Z --- 19.6S 151.9E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 045 NM NORTHEAST QUADRANT 110 NM SOUTHEAST QUADRANT 080 NM SOUTHWEST QUADRANT 090 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 305 DEG/ 03 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 061200Z --- 19.2S 151.3E 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 - 050 NM NORTHEAST QUADRANT 090 NM SOUTHEAST QUADRANT 095 NM SOUTHWEST QUADRANT 055 NM NORTHWEST QUADRANT VECTOR TO 72 HR POSIT: 335 DEG/ 03 KTS --- 72 HRS, VALID AT: 071200Z --- 18.1S 150.7E MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER --- REMARKS: 041500Z POSITION NEAR 19.6S 151.5E. TROPICAL CYCLONE (TC) 17P (IRIS), LOCATED APPROXIMATELY 355 NM EAST- SOUTHEAST OF CAIRNS, AUSTRALIA, HAS TRACKED EAST-SOUTHEASTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED EIR SATELLITE IMAGERY SHOWS A BROAD BUT PARTLY-EXPOSED LLC WITH THE CENTRAL CONVECTION NOW WEAKER AND DISPLACED MORE SOUTHWARD. THE INITIAL POSITION IS PLACED WITH MODERATE CONFIDENCE BASED ON EXTRAPOLATION FROM LOW CLOUD BANDS FEEDING INTO AN OBSCURED LLCC. THE BROAD LLC AND STARKLY DISPLACED CONVECTION ARE MATCHED IN THE 040843Z COLORIZED 91 GHZ SSMIS MICROWAVE PASS. THE INITIAL INTENSITY IS BASED ON AN OVERALL ASSESSMENT OF AGENCY DVORAK ESTIMATES FROM PGTW (T3.0), KNES (T2.5), AND ABRF (T3.0) THAT ARE VALIDATED BY A 041118Z PARTIAL ASCAT PASS SHOWING A FEW 45-KNOT WIND BARBS ALONG THE WESTERN FLANK, AND REFLECTS THE WEAKENED STATE OF TC 17P. UPPER LEVEL ANALYSIS INDICATES THAT THE CYCLONE IS IN AN AREA OF MODERATE (15-20 KNOT) VWS THAT IS MOSTLY OFFSET BY AN EXCELLENT POLEWARD OUTFLOW. ALONG-TRACK SSTS AT 29C ARE ALSO CONDUCIVE. THE SYSTEM IS TRACKING SLOWLY BUT IMMINENTLY INTO A COL ALONG THE SOUTHWESTERN PERIPHERY OF A WEAKENING NER TO THE NORTHEAST. IRIS IS EXPECTED TO ENTER INTO A QUASI-STATIONARY (QS) STATE IN THE COL BETWEEN THE NER AND THE STR TO THE SOUTHWEST. DURING THIS PHASE, THE CYCLONE WILL SLOWLY RECURVE NORTHWESTWARD AS THE STR EVENTUALLY DOMINATES AS THE PRIMARY STEERING MECHANISM. TC 17P IS FORECAST TO GRADUALLY WEAKEN AS VWS INCREASES IN THE NEAR TERM AND IN ADDITION, A MID-LATITUDE TROUGH APPROACHING FROM THE SOUTHWEST WILL CAUSE SUBSIDENCE AND FURTHER ERODE THE ASSOCIATED CONVECTION. AVAILABLE NUMERICAL MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT WITH THE EVENTUAL U-TURN POLEWARD BUT WITH NOTABLE DIFFERENCES IN TRACK SPEED. NAVGEM IS NOW THE SOLE EASTWARD OUTLIER. IN VIEW OF THIS, AND GIVEN THE UNCERTAINTY OF A QS STATE, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC TRACK FORECAST THAT IS LAID JUST SLIGHTLY SLOWER AND A BIT WESTWARD OF MODEL CONSENSUS TO OFFSET THE EASTWARD PULL OF NAVGEM. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 041200Z IS 13 FEET. NEXT WARNINGS AT 042100Z, 050300Z, 050900Z AND 051500Z.//