LIHUE — It’s going to be a rainy wet season across Hawaii, and Hanalei could be looking at potential flooding throughout the season.
The National Oceanic and Atmospheric Administration released its annual wet season outlook for Hawaii on Thursday, which gives the state an idea of what to expect in the coming months.
Hawaii’s wet season runs from October through April, and the dry season goes from May through September.
In the 2019-2020 Wet Season Rainfall Outlook, NOAA predicts ENSO-neutral conditions are likely to continue through the spring of 2020, and that will likely trigger more rain for the state.
ENSO is El Nino Southern Oscillation. It’s a cyclical weather pattern that affects rainfall and involves changes in the temperature of waters in the central and eastern Pacific Ocean.
According to the National Weather Service, it “directly affects rainfall distribution in the tropics and can have a strong influence on weather across the United States and other parts of the world.”
“In the last 30 years, eight out of the top 10 rainiest wet seasons have had ENSO-neutral conditions,” said Kevin Kodama, NWS hydrologist. La Nina is sometimes called the cold phase of ENSO and El Nino is known as the warm phase, according to NOAA.
El Nino describes the conditions that produce periodic warming in sea surface temperatures in the Pacific. The reverse is La Nina, which represents periods of below-average sea-surface temperatures.
ENSO-neutral refers to the period when there is neither an El Nino nor a La Nina present. Ocean temperatures, rainfall patterns and atmospheric winds are typically closer to the long-term average during these times.
Kodama pointed out the last wet season was on the dry side, with a weak La Nina, and the 2017-2018 wet season was a bit on the wet side, with a weak El Nino. Right at the end of that wet season, April 2018, is when record-breaking rains flooded parts of Kauai.
With ENSO-neutral conditions in the 2019-2020 wet season, wet conditions are forecasted to prevail, but those conditions should be somewhere in between those in the last several years.
“Last year I was talking about dryer conditions,” Kodama said. “This year we’re not expecting that.”
The outlook projects the possibility of cutoff low-pressure systems that can produce intense rainfall, especially when combined with expected above-average sea-surface temperatures.
“Hanalei will probably have impacts, and to some extent Wainiha as well,” Kodama said. “If this plays out as it looks like it will, you’ll see impacts up north.”
That’s mainly because of Kuhio Highway, the artery that spans half the island. Kodama said to prepare for closures of the highway at Hanalei Bridge, something that’s part of regular life on rainy days for residents.
Throughout the wet season, the public is reminded to drive slowly, especially in fast-flowing water. Just two feet of fast-flowing water can move most vehicles off the road, according to NOAA.
NOAA also advises to stay informed of conditions by checking latest forecasts, watches, warnings and advisories.
Looking into the weekend for Kauai, however, it’s light trades and scattered showers, according to NWS’s forecast.
“(We’re forecasting) just some trade wind weather, usual trade showers, nothing out of the ordinary,” Kodama said.
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Jessica Else, environment reporter, can be reached at 245-0452 or jelse@thegardenisland.com.
