HONOLULU — Hawaii can expect above average rainfall during the upcoming wet season and potentially have more floods like last winter, the National Weather Service said Friday. Even so, Maui County and the Big Island may remain in drought and at greater risk for wildfires because the leeward sides of their islands won’t get as much rain.
The strength of this year’s La Nina weather event will likely influence rainfall patterns across the island chain. La Nina is a cooling of Pacific Ocean sea surface temperatures near the equator and the flip side of a warmer El Nino pattern.
Kevin Kodama, the weather agency’s senior service hydrologist in Honolulu, said La Nina is expected to be moderate this year. That will mean heavy rainfall on the windward sides of the islands and drier leeward sides during the wet season, which runs from this month through April. That’s similar to the last wet season.
Under this scenario, Kauai and Oahu, which have some areas of moderate drought, will likely recover, but drought is expected continue on Maui County and the Big Island.
Ranchers in leeward Maui County — areas currently in extreme and severe drought — have recently lost cattle due to the dry conditions. A lack of vegetation in the forests has pushed invasive Axis deer into farms, leading to agricultural losses.
On the Big Island in August, one of the largest fires ever recorded in Hawaii burned 65 square miles (168 square kilometers) of mostly grassy ranchland on the slopes of Mauna Kea. Wildfires are not part of the natural life cycle in Hawaii’s environment, and blazes can take out valuable native forests and make room for invasive grasses to grow.
Kodama said the risk for wildfires will depend on the intensity of La Nina. A weaker La Nina would generate more significant rainfall on leeward sides which would alleviate the drought.
“Right now, based on the outlook, there’s a risk for the drought to persist into next dry season. And so, if that happens then we’re going to see wildfire risk through not only wet season, but just increase next summer,” he said. “Hopefully that won’t be the situation.”
The forecast for heavy rain on the windward sides of the island means residents should also be ready for significant flooding events, Kodama said.
He said rain patterns would be similar to the last wet season, which was also a La Nina year. In March, intense heavy rainfall ( one official called it a “heavy rain bomb” ) prompted Maui authorities to evacuate areas downstream of an old, soon-to-be dismantled reservoir they feared might breach, while Oahu officials evacuated parts of Haleiwa town because of a swollen stream.
Scientists say Hawaii can expect similar more intense rainstorms as the climate changes. Researchers have documented that Hawaii’s overall rainfall has declined in recent decades, but rain events with the heaviest downpours have increased.
