How Unusual Are Hurricanes, Tropical Storms In Hawaii?

On average, four to five tropical cyclones occur in the central Pacific Ocean basin - between 140-180 degrees west longitude - each year, according to Dr. Rick Knabb, Hurricane Expert at The Weather Channel and past director of the National Hurricane Center. About two-thirds of those systems drift west from the eastern Pacific basin.

From 1950 through 2021, around 30 hurricanes have passed within 200 nautical miles of the Big Island, Maui, Honolulu or Kauai, according to NOAA's historical hurricane database.

The last one to do so was Category 4 Hurricane Douglas in July 2020, whose center came just 30 miles north of Oahu on July 26. Douglas' wind gusts downed some trees and produced bands of locally flooding rain in parts of the islands.

As pointed out by University of North Carolina - Charlotte graduate student Eric Webb, there was a case of a major hurricane punching through the Big Island and Maui in August 1871, as a January 2018 study uncovered. 

Part of the reason this doesn't happen that often is just geography.

In the vast Pacific Ocean, Hawaii's total land area is only about 6,400 square miles, the fourth-smallest U.S. state by land area, larger than only Connecticut, Delaware and Rhode Island. 

August is the peak month for tropical cyclones in the central Pacific basin, chalking up twice as many (74) as September (37) from 1971-2013, according to the Central Pacific Hurricane Center. Unlike the Atlantic Basin, July is the second most active month (45) in the central Pacific basin.

Dr. Knabb, also a former deputy director at NOAA's Central Pacific Hurricane Center in Honolulu, points out that there is no meteorological reason why the core of a major hurricane can't directly hit Honolulu, resulting in destructive storm surge flooding, wind damage, and rainfall flooding affecting a metro population (minus tourists) of just under 400,000.

How Hawaii Gets Hit By Hurricanes

Hawaii has been, and will be in the future, hit by hurricanes. The key, at least climatologically speaking, is the direction of the storm's approach.

Most tropical cyclones that reach the 50th state arrive from the east or south, but on occasion, they arrive from the southwest. 

Most years, the water is too cool for most tropical systems to arrive from the due east. This is because water currents bring cooler water from Alaska, down the eastern Pacific Ocean along the U.S. West Coast and into the central Pacific.

Sea-surface temperatures are typically warmer the further south you get in the northern Pacific, which means a tropical cyclone moving toward Hawaii from the south would have a better chance of surviving to the islands.

In El Niño years, this idea changes some.

El Niño allows warmer water to push farther north into the more typical east to west trek of tropical systems from the eastern Pacific. The warmer water also allows for more tropical system formation closer to Hawaii and across the eastern Pacific.

Hurricane expert Michael Lowry says that dating to 1950, there is a 13 percent increase in the chance of a named storm to track within 100 miles of the Hawaii islands during an El Niño year (35 percent chance) than a neutral year (22 percent chance).

Another side effect of El Niño is that the trade winds that sometimes trap tropical cyclones well south of the islands relax, making these lingering storms south of the islands more susceptible to be drawn northward. Of course, an El Niño does not guarantee a hurricane will impact Hawaii. 

One such hurricane formed in an El Niño year: 1992. 

The costliest hurricane in Hawaii's history, Hurricane Iniki, originated in the eastern Pacific as Tropical Depression Eighteen-E on Sept. 5, 1992. The depression then crossed over into the central Pacific Ocean basin to the west of 140W longitude where it became a tropical storm and eventually a powerful hurricane. Again, that track was initially well south of Hawaii before it curled north.

The island of Kauai was especially hard hit by damaging winds. Along the southern coast, many structures were wiped out by storm surge flooding and large, battering waves.

Don't Fear The East Most Of The Time

Virtually every system approaching Hawaii from the east since 1950 tracking at least as far north as the latitude of the Big Island of Hawaii eventually weakened to a tropical storm or depression by the time it reached the islands.

This includes a few Category 4 eastern Pacific hurricanes that fizzled, such as Felicia (2009), Orlene (1992) and Raymond (1983).

There are several reasons why this happens so often.

• Drier, more stable air from the subtropical high to the northeast of Hawaii eventually inhibits thunderstorms from persisting and remaining clustered near the cyclone's center.
• Wind shear (the change in wind speed and/or direction with height) is typically stronger near the Hawaiian islands, acting to displace thunderstorms from the cyclone's center.
• Cooler sea-surface temperatures in the Pacific waters to the east of the Big Island of Hawaii keep the air somewhat cooler above it, increasing the stability of the atmosphere, making it less susceptible to forming and maintaining thunderstorms.

Of course, this doesn't mean every single storm will do that in the future. This is the reality of a meteorological rule of thumb.

Dating to 1950, there is no record of a hurricane landfalling on the Big Island of Hawaii. Tropical Storm Iselle in 2014 became only the second tropical storm, and the strongest, to landfall on the Big Island dating to 1950. The only other storm to do so was in 1958. 

Other Recent Hawaii Hurricanes And Tropical Storms

• Lane, 2018: A Category 5 hurricane that weakened rapidly as it approached Hawaii but still brought flooding to the Big Island where rainfall totals of more than 50 inches ranked the storm among the heaviest for any tropical cyclone in U.S. history.
• Hector, 2018: Weakened from a Category 4 hurricane in the eastern Pacific to a tropical storm as it approached Hawaii. Several dozen people on Oahu were rescued from high surf.
• Lester, 2016: An eastern Pacific Category 4 hurricane weakened as it neared Hawaii. The storm passed well north of the islands as a hurricane. Minor flooding was reported on some islands. 
• Darby, 2016: Darby weakened as it closed in on the island of Hawaii, but brought heavy rain and flash flooding to much of the Big Island. This was the second tropical storm landfall in the Big Island in under 2 years. 
• Iselle, 2014: Made landfall as a moderate tropical storm in far eastern Hawaii. Many spots on the eastern side of the Big Island produced more than 10 inches of rain, which induced moderate flooding. First of two landfalls in two years on the eastern shores of the Big Island. Only one of seven deadly tropical systems in Hawaii. The system caused more than $150 million in damages. 

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