2015 Western Pacific typhoon season
Typhoon Atsani 2015
Atsani developed near the Marshall Islands and strengthened into a powerful offshore typhoon. Its track curved northeastward as dry air and increasing wind shear weakened the core.
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161 mph
Aug 19, 2015 during the tropical stage
Full archive record, including non-tropical stages if present
Along the recorded center positions
STORM HISTORY
A well-organized offshore peak
Atsani's precursor was monitored north-northwest of Wotje Atoll before becoming a depression and named storm on August 14. A developing eye marked its transition to a typhoon on August 16. Over the following days, the rainbands tightened and the central thunderstorms deepened.
Very low wind shear and strong outflow supported further intensification. Archived sustained winds reached 140 knots on August 19, when Atsani had a broad, sharply defined eye. The cyclone then weakened while continuing northwestward.
Dry air and a northeastward turn
An eyewall replacement cycle changed the core as dry air entered the circulation and wind shear increased. Atsani turned northeastward, falling below typhoon strength on August 24. It became extratropical northeast of Japan on August 25. No archived position places the center over land, and the later track continues into August 29.
Further reading
QUICK ANSWERS
Atsani in brief
What was Typhoon Atsani's highest wind speed?
161 mph, the highest one-minute sustained wind in its tropical stage, recorded on Aug 19, 2015, 12:00 PM UTC.
What category was Typhoon Atsani?
Category 5 at its peak on the Saffir–Simpson one-minute wind scale, first reaching Category 5 on Aug 19, 2015, 09:00 AM UTC. Other agencies classify storms differently.
What was Typhoon Atsani's lowest pressure?
918 mb, the minimum central pressure recorded during its tropical stage, on Aug 19, 2015, 12:00 PM UTC.
When did Typhoon Atsani occur?
The archived track runs from Aug 14, 2015, 12:00 AM UTC to Aug 29, 2015, 06:00 AM UTC, with the tropical stage from Aug 14, 2015, 12:00 AM UTC to Aug 24, 2015, 09:00 PM UTC.
Where did Typhoon Atsani form?
In the Western Pacific basin, in the 2015 season. Its first archived position is 14.8°N, 163.5°E on Aug 14, 2015, 12:00 AM UTC.
Did Typhoon Atsani make landfall?
No archived position places Typhoon Atsani's center over land, but positions are six-hourly and a brief landfall can fall between them.
METHODOLOGY
Data sources and limitations
The map and summary are generated from NOAA's IBTrACS v04r01 archive. Wind and category use US-agency records; minimum pressure is calculated during the tropical stage, with the archive's pressure source retained. Category 5 refers to the Saffir–Simpson one-minute wind scale; local agencies may use different classifications. Coastlines use Natural Earth's 1:10m land data.
Track distance adds great-circle distances between consecutive observations, excluding gaps over 12 hours. This track has no gaps over 12 hours. The line shows the storm's center, not its size, rainfall or flood extent. Converted wind speeds are rounded to the nearest whole unit.
Archive retrieved
NOAA IBTrACS archive and Field documentation
Sources & methodology