1. TROPICAL CYCLONE 17P (IRIS) WARNING NR 021
02 ACTIVE TROPICAL CYCLONES IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
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WARNING POSITION:
040600Z --- NEAR 19.3S 151.0E
MOVEMENT PAST SIX HOURS - 100 DEGREES AT 05 KTS
POSITION ACCURATE TO WITHIN 015 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 - 040 NM NORTHEAST QUADRANT
045 NM SOUTHEAST QUADRANT
065 NM SOUTHWEST QUADRANT
045 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 120 NM NORTHEAST QUADRANT
170 NM SOUTHEAST QUADRANT
145 NM SOUTHWEST QUADRANT
115 NM NORTHWEST QUADRANT
REPEAT POSIT: 19.3S 151.0E
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FORECASTS:
12 HRS, VALID AT:
041800Z --- 19.4S 151.3E
MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 050 KT WINDS - 015 NM NORTHEAST QUADRANT
030 NM SOUTHEAST QUADRANT
035 NM SOUTHWEST QUADRANT
025 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 070 NM NORTHEAST QUADRANT
160 NM SOUTHEAST QUADRANT
135 NM SOUTHWEST QUADRANT
085 NM NORTHWEST QUADRANT
VECTOR TO 24 HR POSIT: 110 DEG/ 02 KTS
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24 HRS, VALID AT:
050600Z --- 19.5S 151.6E
MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 035 NM NORTHEAST QUADRANT
150 NM SOUTHEAST QUADRANT
125 NM SOUTHWEST QUADRANT
065 NM NORTHWEST QUADRANT
VECTOR TO 36 HR POSIT: 120 DEG/ 01 KTS
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36 HRS, VALID AT:
051800Z --- 19.6S 151.8E
MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 020 NM NORTHEAST QUADRANT
150 NM SOUTHEAST QUADRANT
120 NM SOUTHWEST QUADRANT
030 NM NORTHWEST QUADRANT
VECTOR TO 48 HR POSIT: 270 DEG/ 02 KTS
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EXTENDED OUTLOOK:
48 HRS, VALID AT:
060600Z --- 19.6S 151.4E
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
RADIUS OF 034 KT WINDS - 010 NM NORTHEAST QUADRANT
105 NM SOUTHEAST QUADRANT
085 NM SOUTHWEST QUADRANT
015 NM NORTHWEST QUADRANT
VECTOR TO 72 HR POSIT: 295 DEG/ 01 KTS
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72 HRS, VALID AT:
070600Z --- 19.4S 150.9E
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:
040900Z POSITION NEAR 19.3S 151.1E.
TROPICAL CYCLONE 17P (IRIS), LOCATED APPROXIMATELY 330 NM EAST-
SOUTHEAST OF CAIRNS, AUSTRALIA, HAS TRACKED EASTWARD AT 05 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MSI SHOWS A MOSTLY-EXPOSED LLC WITH
THE CENTRAL CONVECTION CONTINUING TO BE DISPLACED SOUTHWARD. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE VISIBLE
LLC IN THE MSI LOOP THAT LINED UP WELL WITH A DEFINED LOW
REFLECTIVITY CIRCULATION FEATURE IN THE 040435Z SSMIS MICROWAVE PASS.
THE INITIAL INTENSITY IS BASED ON AN OVERALL ASSESSMENT OF AGENCY
DVORAK ESTIMATES AND REFLECTS THE SUSTAINED CONVECTIVE SIGNATURE OF
TC 17P. UPPER LEVEL ANALYSIS INDICATES THAT THE CYCLONE IS IN AN AREA
OF MODERATE (15-20 KNOT) VWS THAT IS MOSTLY OFFSET BY AN EXCELLENT
POLEWARD OUTFLOW. ALONG-TRACK SSTS AT 29C ARE ALSO CONDUCIVE. THE
SYSTEM IS TRACKING SLOWLY INTO A COL ALONG THE SOUTHWESTERN PERIPHERY
OF A WEAKENING NER TO THE NORTHEAST. IRIS IS EXPECTED TO ENTER INTO A
QUASI-STATIONARY STATE IN THE COL BETWEEN THE NER AND THE STR TO THE
SOUTHWEST. DURING THIS PHASE, THE CYCLONE WILL SLOWLY RECURVE
NORTHWESTWARD AS THE STR EVENTUALLY DOMINATES AS THE PRIMARY STEERING
MECHANISM. TC 17P IS FORECAST TO GRADUALLY WEAKEN AS VWS INCREASES.
ADDITIONALLY, A MID-LATITUDE TROUGH APPROACHING FROM THE SOUTHWEST
WILL CAUSE SUBSIDENCE AND STEADILY ERODE THE ASSOCIATED CONVECTION.
AVAILABLE NUMERICAL MODEL GUIDANCE REMAINS SIGNIFICANTLY SPREAD AND
TRIFURCATED WITH COAMPS AND NAVGEM SOLUTIONS TRACKING TC 17P
EASTWARD, SEVERAL MODELS INCLUDING GFS AND ECMWF RECURVING IT
EQUATORWARD, AND THE HWRF PREDICTING A WESTWARD TRACK. IN VIEW 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
040600Z IS 14 FEET. NEXT WARNINGS AT 041500Z, 042100Z, 050300Z, AND
050900Z.
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