1. TROPICAL CYCLONE 17P (IRIS) WARNING NR 024
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:
050000Z --- NEAR 19.5S 152.3E
MOVEMENT PAST SIX HOURS - 070 DEGREES AT 06 KTS
POSITION ACCURATE TO WITHIN 020 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 015 NM NORTHEAST QUADRANT
050 NM SOUTHEAST QUADRANT
125 NM SOUTHWEST QUADRANT
040 NM NORTHWEST QUADRANT
REPEAT POSIT: 19.5S 152.3E
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FORECASTS:
12 HRS, VALID AT:
051200Z --- 19.4S 152.4E
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 040 NM NORTHEAST QUADRANT
065 NM SOUTHEAST QUADRANT
135 NM SOUTHWEST QUADRANT
040 NM NORTHWEST QUADRANT
VECTOR TO 24 HR POSIT: 335 DEG/ 01 KTS
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24 HRS, VALID AT:
060000Z --- 19.2S 152.3E
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 035 NM NORTHEAST QUADRANT
080 NM SOUTHEAST QUADRANT
080 NM SOUTHWEST QUADRANT
030 NM NORTHWEST QUADRANT
VECTOR TO 36 HR POSIT: 325 DEG/ 02 KTS
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36 HRS, VALID AT:
061200Z --- 18.8S 152.0E
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
100 NM SOUTHWEST QUADRANT
010 NM NORTHWEST QUADRANT
VECTOR TO 48 HR POSIT: 320 DEG/ 04 KTS
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EXTENDED OUTLOOK:
48 HRS, VALID AT:
070000Z --- 18.2S 151.5E
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:
050300Z POSITION NEAR 19.5S 152.3E.
TROPICAL CYCLONE 17P (IRIS), LOCATED APPROXIMATELY 402 NM EAST-
SOUTHEAST OF CAIRNS, AUSTRALIA, HAS TRACKED EAST-NORTHEASTWARD AT
06 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL (MSI)
SATELLITE IMAGERY SHOWS A FULLY EXPOSED LLCC TO THE NORTH OF
STRUGGLING, PERIODICALLY FLARING CONVECTION. THE INITIAL POSITION
IS BASED ON THE LLCC EVIDENT IN THE MSI LOOP AND THE PGTW 00Z FIX
POSITION. A 042325Z AMSU-B 89GHZ MICROWAVE IMAGE REVEALS DEEP
CONVECTION ISOLATED TO THE SOUTH OF THE LLCC. THE INITIAL INTENSITY
IS BASED ON OBSERVATIONS OVER 100NM TO THE SOUTHWEST BETWEEN 34-37
KTS, AS WELL AS A 042127Z SATCON ESTIMATE OF 42 KTS. THIS ESTIMATE
IS SLIGHTLY ABOVE THE PGTW AND KNES 00Z FIXES OF CURRENT INTENSITY
(CI) T2.5 (35 KTS) BUT BELOW THE ABRF CI OF T3.0 (45 KTS). A
042326Z BULLSEYE ASCAT PASS REVEALS A PATCH OF 35-39 KT WINDS TO
THE SOUTHWEST, AND A BROAD SWATH OF 30-34 KT WINDS SURROUNDING TC
17P WITH THE EXCEPTION OF THE NORTHWEST SECTOR. UPPER LEVEL
ANALYSIS INDICATES THAT THE CYCLONE IS NOW IN AN AREA OF
UNFAVORABLE (20-30 KNOTS) NORTHERLY VWS, WHICH IS PARTIALLY OFFSET
BY EXCELLENT POLEWARD OUTFLOW. ALONG-TRACK SSTS REMAIN CONDUCIVE
(27 TO 28 CELSIUS). THE SYSTEM IS TRACKING SLOWLY EAST-
NORTHEASTWARD ALONG THE PERIPHERY OF A NEAR-EQUATORIAL RIDGE
EXTENSION TO THE NORTHEAST, WHICH IS RECEDING AS A MIDLEVEL TROUGH
MOVES THROUGH THE AREA. TC 17P IS EXPECTED TO GRADUALLY WEAKEN DUE
TO THE UNFAVORABLE VWS AND AN UPPER LEVEL LOW THAT WILL LIMIT
CONVECTION, DROPPING BELOW 35 KTS AFTER 36 HOURS. AS TC 17P IS
SHEARED FROM THE TOP DOWN, IT IS EXPECTED TO TURN NORTHWESTWARD
UNDER THE STEERING INFLUENCE OF A 700 MB STR TO THE SOUTHWEST,
WHICH WILL BECOME THE PRIMARY STEERING MECHANISM. AVAILABLE
NUMERICAL MODEL GUIDANCE HAS CONVERGED OVER RECENT RUNS TO AGREE
UPON A GENERAL U-TURN AND THEN NORTH OR NORTHWESTWARD SOLUTION, BUT
WITH REMAINING DIFFERENCES IN HOW TIGHTLY TC 17P TURNS NORTHWARD
AND THE TRACK SPEED. THE JTWC FORECAST TRACK IS SLIGHTLY EASTWARD
OF MODEL CONSENSUS AND FOR THIS REASON TGERE IS OVERALL LOW
CONFIDENCE IN THE JTWC TRACK FORECAST. MAXIMUM SIGNIFICANT WAVE
HEIGHT AT 050000Z IS 15 FEET. NEXT WARNINGS AT 050900Z, 051500Z,
052100Z AND 060300Z.
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