1. TROPICAL CYCLONE 17P (IRIS) WARNING NR 031
01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
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WARNING POSITION:
061800Z --- NEAR 18.3S 153.1E
MOVEMENT PAST SIX HOURS - 330 DEGREES AT 08 KTS
POSITION ACCURATE TO WITHIN 030 NM
POSITION BASED ON CENTER LOCATED BY A COMBINATION OF
SATELLITE AND SYNOPTIC DATA
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
REPEAT POSIT: 18.3S 153.1E
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FORECASTS:
12 HRS, VALID AT:
070600Z --- 17.3S 152.7E
MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
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REMARKS:
062100Z POSITION NEAR 18.0S 153.0E.
TROPICAL CYCLONE (TC) 17P (IRIS), LOCATED APPROXIMATELY 426 NM EAST-
SOUTHEAST OF CAIRNS, AUSTRALIA, HAS TRACKED NORTH-NORTHWESTWARD
AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY DEPICTS AN EXPOSED, DEFINED LOW-LEVEL CIRCULATION
CENTER WITH NO SIGNIFICANT DEEP CONVECTION. A 061728Z SSMIS 37GHZ
IMAGE INDICATES LIMITED, SHALLOW CONVECTIVE BANDING OVER THE
SOUTHWEST QUADRANT, ASSOCIATED WITH A BAND OF 25-30 KNOT GRADIENT
WINDS, AND WEAK, FRAGMENTED BANDING ELSEWHERE. SURFACE OBSERVATIONS
FROM MARION REEF VERIFY THE 25-30 KNOT SOUTH-SOUTHEASTERLY WINDS
WHILE LIHOU REEF AND A RECENT SHIP OBSERVATION SUPPORT MUCH WEAKER
WINDS (10-15 KNOTS) OVER THE NORTHERN AND EASTERN SEMICIRCLES. THE
INITIAL INTENSITY IS ASSESSED AT 30 KNOTS BASED ON THE OVERALL WIND
STRUCTURE AS DEPICTED IN RECENT ASCAT. TC 17P IS FORECAST TO TRACK
NORTH-NORTHWESTWARD THROUGH THE FORECAST PERIOD WHILE SLOWLY
WEAKENING. AS SHOWN IN THE NAVGEM MODEL, THERE IS SOME POTENTIAL FOR
THE SYSTEM TO REGENERATE IN 3-4 DAYS AS IT TRACKS EQUATORWARD OVER
WARMER WATER. OVERALL, THERE IS LOW CONFIDENCE IN THE EXACT FORECAST
TRACK DUE TO THE SHALLOW NATURE OF THE SYSTEM AND THE LOW-LEVEL
STEERING INFLUENCE (SUBTROPICAL RIDGE POSITIONED TO THE WEST). THIS
IS THE FINAL WARNING ON THIS SYSTEM BY THE JOINT TYPHOON WRNCEN
PEARL HARBOR HI. THE SYSTEM WILL BE CLOSELY MONITORED FOR SIGNS OF
REGENERATION. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 061800Z IS 12
FEET.
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