WESTERN PACIFIC · 1971 SEASON
Typhoon Irma (1971)
Recorded track and intensity · 7 Nov 1971–17 Nov 1971
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Wind speed & pressure
11 Nov, 18:00 UTCForward speed & ACE
11 Nov, 18:00 UTCHover or tap either graph to follow the track. The slider controls both graphs. Each line uses its matching colored axis.
Forward speed measures the center’s motion. ACE accumulates squared one-minute winds at 00, 06, 12 and 18 UTC during tropical or subtropical stages at 34 kt or above. Missing observations make ACE partial. Missing measurements remain gaps.
178 mph / 287 km/h
11 Nov 1971 · tropical stage
Full archive record, including non-tropical stages if present
Along the recorded center positions
STORM HISTORY
Track and intensity summary
Irma is listed in the Western Pacific basin for the 1971 season. Its archived track begins on 7 Nov 1971, 00:00 UTC at 6.1°N, 140.9°E. US-agency wind is not available for this first observation. These dates describe the available observations, which may include stages before and after the tropical cyclone phase.
The first Category 5 observation appears on 11 Nov 1971, 15:00 UTC. The highest recorded tropical-stage one-minute sustained wind is 155 knots (178 mph / 287 km/h), first recorded on 11 Nov 1971, 18:00 UTC at 16°N, 131.5°E. The minimum recorded tropical-stage central pressure is 885 hPa on 11 Nov 1971, 18:00 UTC.
The full record spans 249 hours and approximately 8,190 kilometers along the recorded center positions. The last recorded position is 32.4°N, 178.1°E on 17 Nov 1971, 09:00 UTC. The final tropical-stage observation is earlier, on 16 Nov 1971, 09:00 UTC.
This summary is calculated from the NOAA IBTrACS archive. Category 5 describes the storm’s peak recorded wind intensity, not its intensity at landfall or the severity of impacts at any location. Landfall times, damage and casualties have not been independently reviewed for this page.
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 · Field documentation
Sources & methodology