1971 Western Pacific typhoon season
Typhoon Irma 1971
Typhoon Irma intensified at a remarkable rate over the Philippine Sea in November 1971. It remained at sea, with shipping and western Pacific islands affected before the storm curved northeast south of Japan.
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178 mph
Nov 11, 1971 during the tropical stage
Full archive record, including non-tropical stages if present
Along the recorded center positions
STORM HISTORY
An exceptionally rapid pressure fall
Irma developed south of Guam and initially moved northeast before turning northwest into the Philippine Sea. Its pressure then fell dramatically as the storm strengthened. The archive records peak one-minute winds of 155 kt and a minimum central pressure of 885 hPa late on 11 November.
Irma's deepening set a contemporary record for the largest pressure fall in 24 hours. That record was later surpassed by Typhoon Forrest in 1983. The strongest phase remained offshore, east of the Philippines.
Curving away from land
After its peak, Irma weakened and turned north east of Taiwan. It then accelerated northeast south of Japan, with its tropical stage ending on 16 November. The archive continues east across the Pacific through the next day.
Irma caused minor damage on western Pacific islands and affected shipping, but its center remained over water. None of the archived positions records a landfall.
Further reading
QUICK ANSWERS
Irma in brief
What was Typhoon Irma's highest wind speed?
178 mph, the highest one-minute sustained wind in its tropical stage, recorded on Nov 11, 1971, 06:00 PM UTC.
What category was Typhoon Irma?
Category 5 at its peak on the Saffir–Simpson one-minute wind scale, first reaching Category 5 on Nov 11, 1971, 03:00 PM UTC. Other agencies classify storms differently.
What was Typhoon Irma's lowest pressure?
885 mb, the minimum central pressure recorded during its tropical stage, on Nov 11, 1971, 06:00 PM UTC.
When did Typhoon Irma occur?
The archived track runs from Nov 7, 1971, 12:00 AM UTC to Nov 17, 1971, 12:00 PM UTC, with the tropical stage from Nov 7, 1971, 12:00 AM UTC to Nov 16, 1971, 09:00 AM UTC.
Where did Typhoon Irma form?
In the Western Pacific basin, in the 1971 season. Its first archived position is 6.1°N, 140.9°E on Nov 7, 1971, 12:00 AM UTC.
Did Typhoon Irma make landfall?
No archived position places Typhoon Irma'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