1. TROPICAL CYCLONE 17P (IRIS) WARNING NR 010
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:
270000Z --- NEAR 19.5S 158.2E
MOVEMENT PAST SIX HOURS - 175 DEGREES AT 09 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 - 065 NM NORTHEAST QUADRANT
070 NM SOUTHEAST QUADRANT
000 NM SOUTHWEST QUADRANT
000 NM NORTHWEST QUADRANT
REPEAT POSIT: 19.5S 158.2E
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FORECASTS:
12 HRS, VALID AT:
271200Z --- 20.7S 158.5E
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 080 NM NORTHEAST QUADRANT
085 NM SOUTHEAST QUADRANT
000 NM SOUTHWEST QUADRANT
000 NM NORTHWEST QUADRANT
VECTOR TO 24 HR POSIT: 160 DEG/ 05 KTS
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24 HRS, VALID AT:
280000Z --- 21.6S 158.9E
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 - 085 NM NORTHEAST QUADRANT
105 NM SOUTHEAST QUADRANT
000 NM SOUTHWEST QUADRANT
000 NM NORTHWEST QUADRANT
VECTOR TO 36 HR POSIT: 210 DEG/ 02 KTS
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36 HRS, VALID AT:
281200Z --- 21.9S 158.7E
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:
270300Z POSITION NEAR 19.8S 158.3E.
TROPICAL CYCLONE (TC) 17P (IRIS), LOCATED APPROXIMATELY 470 NM WEST-
NORTHWEST OF NOUMEA, NEW CALEDONIA, HAS TRACKED SOUTHWARD AT 09
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY SHOWS FLARING CONVECTION TO THE EAST OF A PARTIALLY EXPOSED
LOW LEVEL CIRCULATION CENTER. THE INITIAL POSITION IS PLACED WITH
FAIR CONFIDENCE NEAR THE PGTW AND KNES DVORAK FIX POSITIONS. THE
INITIAL INTENSITY IS SLIGHTLY ABOVE THE PGTW AND KNES T2.0 (30
KNOTS) DVORAK INTENSITY ESTIMATES BUT IS CONSISTENT WITH A 272231Z
OSCAT PASS SHOWING 30-35 KNOT WINDS ON THE EAST SIDE OF THE CYCLONE.
ENVIRONMENTAL ANALYSIS REVEALS LOW TO MODERATE VERTICAL WIND SHEAR
(VWS), GOOD POLEWARD OUTFLOW, POOR EQUATORWARD OUTFLOW, AND SEA
SURFACE TEMPERATURES OF 27 TO 28 CELSIUS. TC 17P WILL TRACK SOUTH-
SOUTHEASTWARD ALONG THE WESTERN PERIPHERY OF THE NEAR EQUATORIAL
RIDGE TO THE EAST UNTIL TAU 12. AFTER TAU 12, A SUBTROPICAL RIDGE TO
THE SOUTH BECOMES THE PRIMARY STEERING INFLUENCE, CAUSING THE
CYCLONE TO SLOW DOWN AND TURN WESTWARD. BY TAU 36, THE SYSTEM WILL
DISSIPATE OVER WATER AS CONVERGENCE ALOFT FROM AN UPPER LEVEL TROUGH
SUPPRESSES CONVECTION. NUMERICAL MODEL GUIDANCE IS HIGHLY UNCERTAIN
OF THE TIMING OF THE TURN TO THE WEST, LEADING TO LOW CONFIDENCE IN
THE JTWC TRACK FORECAST. SOUTHEASTWARD ALONG THE WESTERN PERIPHERY
OF THE NEAR EQUATORIAL RIDGE TO THE EAST UNTIL TAU 12. AFTER TAU 12,
A SUBTROPICAL RIDGE TO THE SOUTH BECOMES THE PRIMARY STEERING
INFLUENCE, CAUSING THE CYCLONE TO SLOW DOWN AND TURN WESTWARD. BY
TAU 36, THE SYSTEM WILL DISSIPATE OVER WATER AS CONVERGENCE ALOFT
FROM AN UPPER LEVEL TROUGH SUPPRESSES CONVECTION. NUMERICAL MODEL
GUIDANCE IS HIGHLY UNCERTAIN OF THE TIMING OF THE TURN TO THE WEST,
LEADING TO LOW CONFIDENCE IN THE JTWC TRACK FORECAST. MAXIMUM
SIGNIFICANT WAVE HEIGHT AT 270000Z IS 15 FEET. NEXT WARNINGS AT
270900Z, 271500Z, 272100Z AND 280300Z.
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