1. TROPICAL CYCLONE 17P (IRIS) WARNING NR 027
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:
051800Z --- NEAR 20.4S 153.5E
MOVEMENT PAST SIX HOURS - 090 DEGREES AT 03 KTS
POSITION ACCURATE TO WITHIN 040 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 - 085 NM NORTHEAST QUADRANT
140 NM SOUTHEAST QUADRANT
115 NM SOUTHWEST QUADRANT
070 NM NORTHWEST QUADRANT
REPEAT POSIT: 20.4S 153.5E
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FORECASTS:
12 HRS, VALID AT:
060600Z --- 19.9S 153.2E
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 000 NM NORTHEAST QUADRANT
105 NM SOUTHEAST QUADRANT
130 NM SOUTHWEST QUADRANT
025 NM NORTHWEST QUADRANT
VECTOR TO 24 HR POSIT: 320 DEG/ 04 KTS
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24 HRS, VALID AT:
061800Z --- 19.2S 152.6E
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 000 NM NORTHEAST QUADRANT
055 NM SOUTHEAST QUADRANT
075 NM SOUTHWEST QUADRANT
005 NM NORTHWEST QUADRANT
VECTOR TO 36 HR POSIT: 335 DEG/ 03 KTS
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36 HRS, VALID AT:
070600Z --- 18.6S 152.3E
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 000 NM NORTHEAST QUADRANT
030 NM SOUTHEAST QUADRANT
070 NM SOUTHWEST QUADRANT
010 NM NORTHWEST QUADRANT
VECTOR TO 48 HR POSIT: 335 DEG/ 04 KTS
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EXTENDED OUTLOOK:
48 HRS, VALID AT:
071800Z --- 17.8S 151.9E
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
020 NM SOUTHEAST QUADRANT
045 NM SOUTHWEST QUADRANT
035 NM NORTHWEST QUADRANT
VECTOR TO 72 HR POSIT: 345 DEG/ 04 KTS
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72 HRS, VALID AT:
081800Z --- 16.1S 151.4E
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:
052100Z POSITION NEAR 20.3S 153.4E.
TROPICAL CYCLONE 17P (IRIS), LOCATED APPROXIMATELY 433 NM NORTH
OF BRISBANE, AUSTRALIA, HAS TRACKED EASTWARD AT 03 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY
REVEALS AN EXPOSED LOW LEVEL CIRCULATION CENTER WITH DEEP
CONVECTION SHEARED APPROXIMATELY 30 NM TO THE SOUTHEAST. THE
INITIAL POSITION IS PLACED WITH MODERATE CONFIDENCE DUE TO THE
SLIGHTLY ELONGATED AND OBSCURED NATURE OF THE LLCC OBSERVED IN THE
EIR LOOP. THIS POSITION IS SUPPORTED BY A 051741Z SSMI/S 91 GHZ
MICROWAVE IMAGE SHOWING CLOUD BANDING WRAPPING INTO THE CIRCULATION
CENTER. THE INITIAL INTENSITY OF 45 KNOTS IS BASED ON A 051800Z
DVORAK ESTIMATE FROM PGTW USING THE SHEAR METHOD. ENVIRONMENTAL
ANALYSIS SHOWS MODERATE NORTHWESTERLY VERTICAL WIND SHEAR (20 TO 25
KNOTS) WHICH IS OFFSET BY EXCELLENT POLEWARD OUTFLOW. SEA SURFACE
TEMPERATURES REMAIN FAVORABLE, BETWEEN 27 AND 28 DEGREES CELSIUS.
TC 17P IS CURRENTLY IN ITS QUASI-STATIONARY (QS) STATE DUE TO A
WEAK STEERING ENVIRONMENT. AS THE SYSTEM GRADUALLY WEAKENS DUE TO
VWS, IT IS EXPECTED TO TRACK TO THE NORTHWEST UNDER THE INFLUENCE
OF THE MID LEVEL STEERING FLOW BEFORE DISSIPATING BY TAU 72.
DYNAMIC MODEL TRACK GUIDANCE REMAINS IN GOOD AGREEMENT ON POSITION
BUT WITH SIGNIFICANT DIFFERENCES IN SPEED AS TC 17P EXITS ITS QS
STATE. THE JTWC FORECAST TRACK IS LAID JUST WESTWARD AND SLOWER
THAN CONSENSUS, FAVORING THE GFS AND ECMWF SOLUTIONS. DUE TO THE
UNCERTAINTY IN TRACK SPEED, THERE IS OVERALL LOW CONFIDENCE IN THE
JTWC FORECAST TRACK AND INTENSITY. MAXIMUM SIGNIFICANT WAVE HEIGHT
AT 051800Z IS 16 FEET. NEXT WARNINGS AT 060300Z, 060900Z, 061500Z
AND 062100Z.
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