WTPS32 PGTW 040300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE WARNING// RMKS/ 1. TROPICAL CYCLONE 17P (IRIS) WARNING NR 020 01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 040000Z --- NEAR 19.3S 150.4E MOVEMENT PAST SIX HOURS - 150 DEGREES AT 04 KTS POSITION ACCURATE TO WITHIN 040 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 050 KT WINDS - 055 NM NORTHEAST QUADRANT 065 NM SOUTHEAST QUADRANT 050 NM SOUTHWEST QUADRANT 040 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 110 NM NORTHEAST QUADRANT 155 NM SOUTHEAST QUADRANT 130 NM SOUTHWEST QUADRANT 090 NM NORTHWEST QUADRANT REPEAT POSIT: 19.3S 150.4E --- FORECASTS: 12 HRS, VALID AT: 041200Z --- 19.6S 150.8E MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 050 KT WINDS - 035 NM NORTHEAST QUADRANT 035 NM SOUTHEAST QUADRANT 045 NM SOUTHWEST QUADRANT 040 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 115 NM NORTHEAST QUADRANT 135 NM SOUTHEAST QUADRANT 135 NM SOUTHWEST QUADRANT 095 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 090 DEG/ 01 KTS --- 24 HRS, VALID AT: 050000Z --- 19.6S 151.0E MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 080 NM NORTHEAST QUADRANT 140 NM SOUTHEAST QUADRANT 140 NM SOUTHWEST QUADRANT 075 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 155 DEG/ 01 KTS --- 36 HRS, VALID AT: 051200Z --- 19.8S 151.1E MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 075 NM NORTHEAST QUADRANT 150 NM SOUTHEAST QUADRANT 150 NM SOUTHWEST QUADRANT 080 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 270 DEG/ 01 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 060000Z --- 19.8S 150.9E MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 065 NM NORTHEAST QUADRANT 135 NM SOUTHEAST QUADRANT 105 NM SOUTHWEST QUADRANT 060 NM NORTHWEST QUADRANT VECTOR TO 72 HR POSIT: 310 DEG/ 01 KTS --- 72 HRS, VALID AT: 070000Z --- 19.5S 150.5E 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 - 000 NM NORTHEAST QUADRANT 115 NM SOUTHEAST QUADRANT 080 NM SOUTHWEST QUADRANT 030 NM NORTHWEST QUADRANT VECTOR TO 96 HR POSIT: 300 DEG/ 02 KTS --- LONG RANGE OUTLOOK: --- 96 HRS, VALID AT: 080000Z --- 19.2S 149.9E MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT WIND RADII VALID OVER OPEN WATER ONLY DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER --- REMARKS: 040300Z POSITION NEAR 19.4S 150.5E. TROPICAL CYCLONE 17P (IRIS), LOCATED APPROXIMATELY 299 NM EAST- SOUTHEAST OF CAIRNS, AUSTRALIA, HAS TRACKED SOUTH-SOUTHEASTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS DIMINISHING CONVECTIVE BANDING WRAPPING INTO THE CENTER, PARTIALLY COVERING THE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH GOOD CONFIDENCE BASED ON THE MSI LOOP AND 00Z PGTW FIX, SUPPORTED BY A 032010Z SSMIS 37GHZ MICROWAVE IMAGE SHOWING A PARTIALLY CLOSED LOW REFLECTIVITY DIMPLE AT THE CENTER. THE INITIAL INTENSITY IS BASED ON A 032249Z ASCAT PASS REVEALING SEVERAL 50 KT WINDS BARBS CLOSE TO THE CENTER, AND IS SUPPORTED BY A 46 KT SUSTAINED OBSERVATION FROM 68NM AWAY, IMPLYING HIGHER WINDS CLOSER TO THE CENTER. THE INTENSITY AGREES WITH THE PGTW CURRENT INTENSITY (CI) ESTIMATE OF T3.5 (55 KTS) AND IS SLIGHTLY ABOVE THE KNES CI OF T3.0 (45 KTS). UPPER LEVEL ANALYSIS INDICATES TC 17P IS IN AN AREA OF MODERATE TO HIGH (15-25 KT) VERTICAL WIND SHEAR (VWS) AND THERE IS CONVERGENCE ALOFT TO THE NORTHWEST, BOTH OF WHICH ARE SUPPRESSING CONVECTION. THESE UNFAVORABLE INFLUENCES ARE SOMEWHAT OFFSET BY A POLEWARD OUTFLOW CHANNEL. ALONG-TRACK SSTS REMAIN FAVORABLE AT 27C. TC 17P HAS BEGUN TO INGEST DRY AIR FROM THE WEST, DIMINISHING ITS CONVECTIVE SIGNATURE BUT NOT YET LEADING TO WEAKENING. TC IRIS IS TRACKING ALONG THE SOUTHWEST PERIPHERY OF THE NEAR EQUATORIAL RIDGE EXTENSION TO THE NORTHEAST, AND IS EXPECTED TO CONTINUE TO THE SOUTHEAST ON THIS TRACK UNTIL TAU 36 AND GRADUALLY WEAKEN DUE TO DRY AIR ENTRAINMENT AND INCREASING VWS. AT TAU 36, A DEEP TROUGH MOVES INTO THE AREA FROM THE WEST, INCREASING VERTICAL WIND SHEAR FURTHER, AND THE NEAR EQUATORIAL RIDGE TO THE NORTHEAST RECEDES, LEADING TO A QUASISTATIONARY PERIOD. AS TC 17P DEGRADES, IT WILL BECOME SUBJECT TO MID-LAYER AND SHALLOW STEERING FLOW FROM THE TROUGH, AND TC 17P IS FORECAST TO MOVE TO THE NORTHWEST. AVAILABLE NUMERICAL MODEL GUIDANCE IS SIGNIFICANTLY SPREAD AND TRIFURCATED AFTER TAU 24, WITH COAMPS AND NAVGEM SOLUTIONS TRACKING TC 17P OVER OCEAN TO THE EAST, MANY MODELS INCLUDING GFS AND ECMWF EXECUTING A LOOP AND MOVING TC 17P EITHER NORTH OR NORTH-NORTHEASTWARD, AND THE WESTERN OUTLIER HWRF PREDICTING A LOOP AND THEN WESTWARD TRACK. IN LIGHT OF THIS, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC TRACK FORECAST THAT IS LAID SLIGHTLY SLOWER AND WESTWARD OF MODEL CONSENSUS TO OFFSET THE EASTWARD OUTLYING TRACKS. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 040000Z IS 14 FEET. NEXT WARNINGS AT 040900Z, 041500Z, 042100Z AND 050300Z.//