Dry conditions across Hawaii could persist during the wet season as La Nina is expected to continue.
The National Weather Service in Honolulu on Wednesday presented its outlook for the state’s wet season, which goes from October until April. But even though the wet season is expected to bring above-average rainfall to some parts of the state, it may not end the drought conditions that struck other parts — particularly West Hawaii and Maui — during the dry season.
Hydrologist Kevin Kodama said this year’s dry season was the 16th-driest in the last 30 years, with records set at several sites on the Big Island in June and August.
The dry conditions coincide with the current La Nina phenomenon. La Nina is the colder half of the El Nino Southern Oscillation climate pattern and has been occurring in Hawaii for the past two years, and Kodama said it is expected to continue at least into spring. During Hawaii’s wet season, La Nina typically means more rainfall, but Kodama said not all parts of the state could see it.
“The climate models favor above-average precipitation across the region around the Hawaiian Islands,” Kodama said. “But because of our terrain, that rainfall distribution really depends on how the strength of the La Nina shapes out.”
For example, Kodama explained, if a stronger La Nina brings more persistent trade winds, windward slopes throughout the state will receive increased rainfall, but leeward slopes will stay dry. But vice-versa, a weaker La Nina means more intermittent trade winds, and a more egalitarian distribution of rainfall on both sides of the islands.
Kodama said that a weak to moderate La Nina is forecasted for the winter, but he added that “a lot can change between now and April.”
“If this sounds familiar, it’s because it’s very similar conditions to last year,” Kodama said. “We’re going into … potentially our third year in a row of La Nina conditions during the wet season. This has only happened twice before since 1950.”
The last time Hawaii had a three-year La Nina was also marked by a widespread drought, Kodama said. Between 1997 and 1998, there was a strong El Nino which began drought conditions in various parts of the state, but by mid-1998, the climate pattern had shifted to La Nina, which kept the drought going until 2002.
Kodama added that farmers affected by the current drought have said that it will take multiple years of rainy wet seasons to restore moisture to the soil in some places.
Kodama also said that the La Nina conditions led to a notably mild hurricane season, with only one storm, Hurricane Darby, particularly impacting the state. Darby, which passed south of Hawaii in mid-July, brought some additional rain to the Big Island, but rainfall totals for that month were still below average.
It is still far too early to predict the intensity of 2023’s hurricane season, Kodama said, but he did explain that La Nina is conducive to a milder season, so if La Nina conditions persist throughout next year, the season could remain weak.
As the wet season approaches, Kodama warned residents to be aware of flood warnings and to not attempt to cross any flood waters.
“You can have flooding even in a drought,” Kodama said. “In Hawaii, these events can happen so quickly.”
Email Michael Brestovansky at mbrestovansky@hawaiitribune-herald.com.