FACT CHECK: Is Hurricane Irma The ‘Most Powerful’ Atlantic Storm On Record?

David Sivak | Fact Check Editor

As Hurricane Irma – a Category 5 cyclone – made its way through the Caribbean Wednesday, some media outlets claimed that Irma is the “most powerful” Atlantic storm on record.

Verdict: True

When looking at Irma’s sustained intensity, it qualifies as the most powerful Atlantic hurricane on record. The tropical storm is not, however, the strongest when judged by common measures like wind speed and minimum central pressure.

Fact Check:

According to Philip Klotzbach, a meteorologist at Colorado State University, Irma sustained winds of 185 mph for at least 33 hours, the longest of any tropical storm in the world since satellite records began in 1966.

Irma also set the record for the most Accumulated Cyclone Energy (ACE) of any Atlantic hurricane over a 24-hour period, with more ACE than the first eight named Atlantic storms of 2017 combined – including Hurricane Harvey. Meteorologists use ACE to measure both the intensity and duration of a cyclone.

Irma has become this powerful in part because it developed over warmer-than-usual waters and didn’t encounter strong high-altitude winds, which can lessen the intensity of tropical cyclones.

Although Irma has set several records, it does not have the highest recorded wind speeds. That record goes to Hurricane Allen, which reached sustained winds of 190 mph in 1980. Irma ties for second place with three other Atlantic hurricanes that sustained wind speeds of 185 mph.

Some media outlets incorrectly reported that Irma was the strongest Atlantic storm on record based on wind speeds, but that’s only true if you exclude records set in the Gulf of Mexico and the Caribbean Sea.

If judged by minimum central pressure, another common metric of hurricane intensity, Irma makes the top 10, but ranks at the bottom of the list.

By some standard measures, Irma might not be considered the most powerful Atlantic storm on record, but given that it has broken records using measures that account for both intensity and duration, we rate the claim as true.

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David Sivak

Fact Check Editor


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