It looks like it’s going to be a wet one this winter in
Hawaii — although maybe not for everyone.
The National Weather Service released its annual wet-season forecast Tuesday, saying an above-average rainy season is likely for the windward areas of the islands, while signals remain cloudy as to whether leeward areas will see more rain than usual.
In fact, drought might persist or even worsen in leeward sections this winter, especially on Hawaii island and in Maui County, where some areas are enduring
severe and extreme episodes of drought.
It could all come down to how intense the La Nina weather phenomenon develops in the coming months, said Kevin Kodama, National Weather Service hydrologist.
The National Oceanic and Atmospheric Administration’s Climate Prediction Center has issued a “La Nina Watch,” with a 55 to 65 percent chance of conditions morphing into La Nina during the fall and winter.
La Nina is the polar opposite of El Nino, the global climate phenomenon that causes winter drought in
Hawaii.
Although La Nina historically draws more rainfall to the islands, the amount of precipitation in recent wet seasons depended on how intense the La Nina ultimately became, Kodama said.
A moderate or strong La Nina made for wet conditions over windward slopes but left leeward areas dry. Weaker La Ninas resulted in more rainfall over leeward areas, allowing for more low-pressure systems and Kona storms.
At this point the intensity of the anticipated La Nina is unknown, according to the Climate Prediction Center. While most models point to a weak or moderate La Nina, a few normally reliable models suggest a strong event, Kodama said.
In any case, drought recovery is in the forecast for a state experiencing “abnormally dry” conditions over 96 percent of the islands following a dry summer that was described Tuesday as the 13th-driest dry season in Hawaii over the last
30 years.
According to the Hawaii Drought Monitor, two-thirds of the state is enduring at least moderate drought, but the most severe conditions are found on the leeward side of Hawaii island, with extreme drought also gripping leeward Maui and Molokai.
Ranching and other agricultural concerns are the hardest-hit by the drought on Hawaii island, Kodama said. There even have been reports about drought
issues on the windward side, including stunted taro growth in Waipio Valley and stunted ginger on the
Hamakua Coast.
“It will take quite a bit to pull the Big Island out of drought completely,”
Kodama said.
Kodama said the dry season, from May through September, was made drier in part because anticipated El Nino conditions never developed, and neither did the resulting tropical cyclones that usually bring summer moisture.
Weather officials had predicted five to eight cyclones for the season, but only two storms — Tropical Storm Fernanda and the tropical depression that was formerly Tropical Storm Greg — entered the Central Pacific in July, both losing intensity fast before dying hundreds of miles from the islands.
Hurricane season continues through November.