Hurricane Dorian: What is a Category 5 hurricane — and how strong is it?

The U.S. National Hurricane Center (NHC) is warning of “catastrophic conditions” as hurricane Dorian makes landfall.

The historic storm hit the northern Bahamas on Sunday afternoon with sustained winds of nearly 300 km/h.

It’s been designated a Category 5 hurricane — here’s exactly what that means.

Hurricanes are categorized on what’s called the Saffir-Simpson Hurricane Wind Scale.

The ratings, which range from one to five, are based on sustained wind speeds and potential damage.

“The scale — originally developed by wind engineer Herb Saffir and meteorologist Bob Simpson — has been an excellent tool for alerting the public about the possible impacts of various intensity hurricanes,” the NHC explains on its website.

The examples of damage used in the Saffir-Simpson scale are based on U.S. homes and buildings, but areas with weak infrastructure could face even greater devastation.

The category system also doesn’t take into account other potential damage from hurricanes, such as flooding, the NHC notes.

Category 1 means sustained winds of 119-153 km/h — these “very dangerous winds” will produce some property damage, the NHC said.

Category 2 is more serious, with winds of 154-177 km/h.

A Category 3 (178-208 km/h winds) and higher is considered a major hurricane that will create “devastating” damage.

At the peak of the scale, Category 5 means sustained winds of a jaw-dropping 252 km/h or higher.

The NHC explains that in a Category 5 event, “catastrophic damage will occur.”

For every category increase, the damage level generally increases by about a factor of four.

Global News chief meteorologist Anthony Farnell said that Dorian’s 298 km/h winds are potentially 1,300 times more destructive than a storm with 120 km/h winds — “which is what Dorian was when it moved over the Virgin Islands a few days ago.”

During a Category 5 hurricane, “complete structures are levelled down to their foundation,” he said.

“Complete tree loss occurs. Storm surges can top 20 feet and with waves on top of that, I’m expecting complete devastation for areas that are impacted by the strongest winds around the eyewall.”

Dorian is the second strongest Atlantic hurricane since 1950. The strongest, hurricane Allen in 1980, had peak winds of 306 km/h.

Puerto Rico’s catastrophic 2017 hurricane Maria, as well as hurricane Katrina — which devastated parts of Louisiana in 2005 — were both Category 5 events.

“Dorian joins a select group of only a handful of storms to make landfall with that intensity and such a low pressure (911 mb),” Farnell said.

“For comparison, Dorian’s intensity is slightly stronger than hurricane Irma when it made landfall and basically ravaged the Caribbean island of Barbuda,” he said.

Farnell said Dorian is expected to weaken and linger over the northern Bahamas on Sunday and Monday.

Nonetheless, it’s expected to remain “very dangerous and increasingly large” as it approaches the U.S. east coast early next week.

With a file from the Associated Press

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