2009 Western Pacific typhoon season
Typhoon Choi-Wan 2009
Choi-Wan passed through the Northern Mariana Islands during rapid intensification. The small island of Alamagan suffered extensive destruction even though no casualties were reported.
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161 mph
Sep 15, 2009 during the tropical stage
Full archive record, including non-tropical stages if present
Along the recorded center positions
STORM HISTORY
Strengthening through the Marianas
The cyclone developed east of Guam on September 11 and became Tropical Storm Choi-Wan the following day. It moved westward and intensified quickly, crossing the Northern Mariana Islands on September 15. The archive records its peak sustained winds of 140 knots later that day.
On Alamagan, the storm destroyed all but one structure and felled most trees. The United States Navy judged the island uninhabitable after the passage. Residents were evacuated to Saipan, despite the absence of reported storm deaths or injuries.
Loss of strength over open water
Choi-Wan remained powerful into September 17, when weakening outflow reduced support for its thunderstorms. An eyewall replacement cycle also altered the inner core. Stronger wind shear then accelerated weakening on September 19, and the storm became extratropical on September 20 over open water.
Further reading
QUICK ANSWERS
Choi-Wan in brief
What was Typhoon Choi-Wan's highest wind speed?
161 mph, the highest one-minute sustained wind in its tropical stage, recorded on Sep 15, 2009, 06:00 PM UTC.
What category was Typhoon Choi-Wan?
Category 5 at its peak on the Saffir–Simpson one-minute wind scale, first reaching Category 5 on Sep 15, 2009, 03:00 PM UTC. Other agencies classify storms differently.
What was Typhoon Choi-Wan's lowest pressure?
918 mb, the minimum central pressure recorded during its tropical stage, on Sep 15, 2009, 06:00 PM UTC.
When did Typhoon Choi-Wan occur?
The archived track runs from Sep 11, 2009, 12:00 PM UTC to Sep 20, 2009, 06:00 PM UTC, with the tropical stage from Sep 12, 2009, 12:00 AM UTC to Sep 20, 2009, 03:00 AM UTC.
Where did Typhoon Choi-Wan form?
In the Western Pacific basin, in the 2009 season. Its first archived position is 13.4°N, 155°E on Sep 11, 2009, 12:00 PM UTC.
Did Typhoon Choi-Wan make landfall?
No archived position places Typhoon Choi-Wan'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