Hurricane season is June 1 to Nov. 30 in Hawaii, and AccuWeather — a commercial weather forecasting service — is predicting a relatively quiet season for tropical cyclones in the Central Pacific basin.
“The last couple of seasons were pretty inactive across the Central Pacific and we’re predicting a less active season,” Alex DaSilva, AccuWeather lead hurricane forecaster, told the Tribune-Herald Tuesday. “We’re forecasting one to three named storms to make it into the Central Pacific this year. Last year, we had three that crossed the line to make it in there. The average is four, so we’re predicting a below average season in the Central Pacific — with zero to two hurricanes. There might not even be a hurricane. The average number of hurricanes there is three, and we’re forecasting zero to two, and then zero to one major hurricane, with the average being two.”
The vast majority of tropical cyclones in the Pacific are spawned in the Eastern Pacific, although they can develop in any tropical waters. Of the three that moved westward across the 140-degree West longitude line into the Central Pacific, only one, Dora was a hurricane. Dora was a major hurricane, Category-4 at the height of its power, and passed well south of Hawaii.
That said, Dora had a major impact on the islands, especially on Maui and the Big Island.
Dora generated winds of 60 mph-plus well away from its center that whipped up wildfires in West Hawaii and West Maui, fueling the Lahaina blaze on Aug. 8 that claimed more than 100 lives while leaving thousands of Mauians homeless. Here on the Big Island, there were no reported injuries or deaths, but at least seven structures in West Hawaii were damaged or destroyed by the wildfires.
“Even though that system was hundreds of miles away, there was still some impact,” DaSilva said.
Dora was small but powerful, and made it not only into the Central Pacific, but crossed the International Date Line as a hurricane, where it became Typhoon Dora.
Veteran Big Island storm watchers are familiar with the concept of storms hundreds of miles away causing extreme weather changes that result in damage. That was driven home in the summer of 2018.
In late August that year, Lane, a former tropical cyclone, had already passed the Big Island and was being torn to remnants by wind shear when the storm’s outer rain bands dropped a deluge of historic proportions on East Hawaii.
Mountain View received 51.5 inches of rain in a four-day period. Damage to county facilities totaled about $20 million, and an estimated 152 homes were damaged, with 59 sustaining major damage from Lane.
According to DaSilva, another reason he and his colleagues are predicting a milder hurricane season is a predicted shift from El Nino to La Nina conditions. El Nino refers to the above-average sea-surface temperatures that periodically develop across the east-central equatorial Pacific. It represents the warm phase of the El Nino Southern Oscillation, or ENSO cycle. The other side of the ENSO coin, La Nina refers to the periodic cooling of sea-surface temperatures across the east-central equatorial Pacific.
“Sometime this summer, La Nina should kick in, and La Ninas are not favorable for tropical (storm) development in the Pacific Basin, as we would see more wind shear in the basin, which would certainly limit the tropical (storm) development,” DaSilva said. “All things considered, it looks like water temperatures are going to be near to below average during the hurricane season with increased wind shear throughout the season, especially later in the season.”
DaSilva cautioned against AccuWeather’s prediction causing complacency among Hawaii residents.
“Even though we’re calling for a lower-than-average hurricane season this year, you still want to follow the weather closely during hurricane season because things can still happen,” he said. “I think it anything is going to happen, it will be in the first half of the season. And the reason is as we transition to La Nina, that is going to increase wind shear across the basin. That would make it more difficult in the middle to later portions of the hurricane season to see (a tropical cyclone) make it to you guys.”
And although Lane was blamed for only one fatality, a man who drowned on Kauai after jumping into a swollen stream in an attempt to save a dog, DaSilva pointed to the example of Hurricane Harvey in 2017, in which at least 68 people, mostly in and around Houston, died directly — all but three from flooding.
“Flooding from rain and storm surge is the biggest killer in hurricanes. It’s not wind,” he said. “They say you can hide from the wind but you have to run from the water. That’s why we’re always concerned about coastal areas.”
Email John Burnett at jburnett@hawaiitribune-herald.com.