Forecasters predict above-average rain for Hawaii this winter

Above-average rainfall is being predicted for Hawaii’s wet season — good news for a state locked in a prolonged drought.

But National Weather Serv­ice forecasters on Wednesday warned that drought relief might not occur evenly across the state.

Kevin Kodama, National Weather Service hydrologist, said the amount of rain that reaches leeward areas could depend on the severity of the La Nina weather pattern expected to persist into its third year.

If La Nina is strong, higher-­than-normal tradewinds will focus rainfall on windward sides, leaving less moisture for leeward sides of the islands, he said.

A weaker La Nina, by contrast, is more likely to allow for weather systems that produce significant leeward rainfall, including the kind of severe Kona-low storm that raked the islands last December.

Kodama said a consensus of climate models favors a weak to moderate La Nina that will produce above-average, large-scale rainfall, especially from December through April.

“But it’s pretty early, and a lot can change between now and April. So we’ll want to see how it all pans out,” Kodama said at a Honolulu news conference.

Honolulu Board of Water Supply spokeswoman Kathleen Elliott-Pahinui said the NWS wet season outlook is good news for an agency that has been asking its Oahu customers to voluntarily cut back water use 10% to make up for wells taken out of commission due to the Red Hill water crisis.

“We’re happy and thrilled,” she said.

Customer conservation helped the agency endure the dry summer months, Elliott-Pahinui said, and soon the board will consider formally dropping the standing request for voluntary conservation.

“We hope and pray it is indeed a wet winter,” she said. “But we’ll always ask for conservation. Water is precious and we don’t want to take it for granted.”

The current U.S. Drought Monitor indicates that nearly 90% of the state is still affected by some form of drought.

While the drought is likely to ease in many areas around the state in the coming months, including Kauai and Oahu, that might not be the case in some leeward areas, Kodama said. Drought could very well persist over parched regions of leeward Maui County and the Big Island, where some agricultural concerns have been hard hit by drought.

“Some of the pastures are in really bad shape,” he said. “It’s not just one (storm) that will solve it all. You talk to ranchers and they say they need multiple events to get the rainwater to percolate down and restore the soil moisture.”

The National Weather Serv­ice’s Climate Prediction Center this month is calling for a 75% chance of La Nina continuing this winter with a 54% chance of a transition to neutral conditions sometime from February to April.

La Nina, the polar opposite of El Nino, is tied to cooler-than-normal sea surface temperature in the tropical central and eastern Pacific and affects weather around the world, including helping to suppress Hawaii’s hurricane season.

“We’re potentially going into our third year in a row of La Nina conditions during the wet season,” the forecaster said. “This only happened twice before since 1950, so it’s a pretty unusual situation.”

As for the 2022 dry season, most areas across the state saw near- to below-­average rainfall this summer during a dry season that started early.

Extreme drought was seen on Hawaii island and Maui as early as mid-May, Kodama said, and conditions only worsened across the rest of the state into August.

Significant brush fires affected the Big Island and Maui County, while drought led to calls for water conservation on Maui and contributed to severe crop and pasture losses caused by a proliferation of axis deer on Maui and Molokai.

“It really put farmers there in a tough situation,” Kodama said.

While 2022 was officially the 16th-driest dry season in the past 30 years — based on rankings from eight key rain gauge sites — the ranking is somewhat deceptive, he said, because there were record dry conditions in Oahu’s Koolau range in June and record dry conditions in windward Hawaii island in August.