After the second-wettest dry season in three decades, Hawaii is expected to see below average rainfall in the coming months, according to the National Oceanic and Atmospheric Administration’s wet season rainfall outlook that was released Friday.
Kevin Kodama, senior hydrologist with the National Weather Service in Honolulu, said the beginning part of the dry season, which runs from May through September, brought some droughts in leeward areas.
Droughts developed in Maui County early this summer, as well as leeward areas of the Big Island and Oahu, according to the outlook, and reached severe levels in small portions of the Big Island and Maui.
Then came the rains.
With Hurricane Lane in August, Tropical Storm Olivia in September and other weather systems that also produced heavy rain, Kodama said droughts were “pretty much eliminated across the state by early October.”
Throughout a four-day period in August, Hurricane Lane dumped as much as 50 inches of rain in some areas of East Hawaii.
“Rainfall totals were above average pretty much everywhere on the east half of the Big Island,” down to Pahala, said Kodama.
Heading into the wet season, which runs from October to April, however, Kodama said an El Nino system is developing. The outlook says there is a 70 percent to 75 percent chance of El Nino forming in the coming months.
“It’s not quite formed yet, but the Climate Prediction Center expects in the next couple of months it will be a mature El Nino event,” he said. “So what that means for the state is we anticipate a below average rainfall.”
According to Kodama, El Nino is an abnormal warming of sea surface temperatures near the equator, while La Nina is the opposite — an abnormal cooling of sea surface temperatures.
El Nino causes a shift in the weather circulation patterns in the Pacific, which translates to below average rainfall in areas around the Hawaiian Islands during winter in the northern hemisphere, he explained. These weather systems can occur every two to seven years.
Kodama said different climate models show a “weak” El Nino event, which means “we could see some rain events still able to make it to the Hawaiian Islands region.”
There could be some above average rainfall in the early parts of the wet season, he said.
“But once December rolls around, it’s going to dry out quite a bit. For the rest of the wet season into the spring, we’re expecting below average rainfall for that time frame,” Kodama said. “The whole wet season numbers, I think, will end up being below average.”
The outlook also anticipates possible drought development along lower leeward slopes by the end of February — mainly moderate, but some severe — with main impacts to agriculture and homes on rainfall catchment systems.
Email Stephanie Salmons at ssalmons@hawaiitribune-herald.com.