Calvin: A Brush for Hawaii After Becoming Season's First Pacific Major Hurricane

Tropical Storm Calvin brushed by Hawaii in mid-July, in a much weaker state compared to its peak as a major hurricane in the eastern Pacific.

C​alvin history. After first becoming a tropical depression on July 11, then a tropical storm the following day, Calvin rapidly intensified into the Western Hemisphere's first major hurricane of 2023 by July 14.

F​ortunately, it did so over the Eastern Pacific Ocean far from land, more than 1,000 miles from Cabo San Lucas, Mexico.

Calvin then tracked over much cooler water than it did when it rapidly intensified into a major hurricane. That's because ocean currents bring cooler water southward off the West Coast of California then southwestward to an area of the Eastern Pacific Basin east of Hawaii.

T​he less ocean warmth, the less potential energy is available for a tropical storm to feed off.

Calvin also became embedded in a drier, sinking, more stable air mass as it moved toward Hawaii.

This weakens tropical storms and hurricanes because more stable air suppresses convection that sustains their existence. Dry air eats away at the core of tropical cyclones.

C​alvin approached Hawaii from the east on July 19th and then passed by on July 20th.

A​s Calvin passed by Hawaii to the south, it brought winds gusts up to 70 mph to the volcanic peaks of the Big Island and more than 2 inches of rain to the windward side of the eastern Hawaiian islands.

Since 1971, 17 Eastern Pacific hurricanes made it as far west as Hawaii, but weakened to either tropical depressions or storms by the time they arrived, a​ccording to NOAA's historical database.

T​here were a few exceptions.

I​n July 2020, Hurricane Douglas held onto Category 1 status as it brushed Hawaii, the closest hurricane to pass near Oahu in 61 years.

I​n general, Hawaii hurricanes are quite rare, but especially so if they come from the Eastern Pacific.

O​f nine hurricanes that have passed within 60 nautical miles of Hawaii in NOAA's database since 1971, only two of those, Douglas in 2020 and Fico in 1978, were also Eastern Pacific hurricanes before they arrived.

Hurricane Iselle weakened to a tropical storm before it arrived on the Big Island in August 2014 and therefore wasn't counted in that statistic.

Another, 2018's Hurricane Lane, tracked a bit too far south to be picked up by NOAA's 60 nautical-mile search criterion.

Despite that, Lane managed to dump prolific rainfall in parts of the islands. A 58-inch total at Kahuna Falls on the Big Island was not only a state all-time record for a tropical cyclone, but was also second highest only to 2017's Hurricane Harvey (60.58 inches) for heaviest rainfall from any U.S. tropical cyclone.

Jonathan Erdman is a senior meteorologist at weather.com and has been an incurable weather geek since a tornado narrowly missed his childhood home in Wisconsin at age 7. Follow him on Twitter and Facebook.

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