Although it might not appear so, especially in East Hawaii, the annual dry season has begun.
During a press conference Tuesday in Honolulu, Kevin Kodama, the National Weather Service’s senior service hydrologist in Hawaii, predicted a drier-than-normal dry season, which runs from May 1 through Sept. 30.
“Looking forward for the May through September dry season, right now we have probabilities favoring a La Nina developing,” Kodama said. “And that La Nina, once it develops, is expected to persist into the early part of next year, which is what you would expect.”
La Nina conditions means that equatorial waters in the Pacific have a lower-than-normal surface temperature. The forecast is for the current weakening El Nino conditions to rapidly become La Nina over the summer. Forecasters expect the La Nina conditions to persist into 2025, and below-average dry season precipitation is typical for the summer months of a La Nina onset year.
“NOAA’s Climate Prediction Center, their forecast probabilities favor below-average precipitation for the rest of the dry season,” Kodama said. “And I have to stress the rest of the dry season. … The dry season totals will be skewed mainly because of the rainfall we just had in the first half of this month.”
Kodama pointed to the rainfall received this month at Daniel K. Inouye International Airport in Honolulu, where 4.9 inches fell as of Monday. He said rainfall at the Honolulu airport already has exceeded its average of 3.56 inches for the entire dry season.
That’s due to two low-pressure systems that have recently affected Hawaii’s weather, especially a kona low system last week that dumped a lot of rainfall from Maui westward, but had a minimal effect on the Big Island.
“For many areas of the state, the April and May rainfall that we’ve had should delay the development of significant drought. What I mean by significant would be severe or D2 category on the U.S. Drought Monitor map,” Kodama said. “A couple of big exceptions here: One would be the leeward slopes of Haleakala on Maui and also the interior section of the Big Island, because these two areas never quite got the full amount of that rainfall. So, they’re still in severe drought right now. … And things should continue to get worse as we move along in the coming weeks and months.”
Kodama said the early dry-season rainfall should also delay significant wildfire risks that happen in the summer.
“They’re not expected to develop until later than we would normally expect,” he said. “Because normal is usually late July into early August. This may not occur until later on in the summer.
“Again, the couple of exceptions would be those areas I’ve already mentioned … leeward slopes of Haleakala and also, the interior sections of the Big Island.”
Reviewing the just-completed wet season, Kodama said that even though the prediction of near- to below-average in most locations is technically correct, “It was not quite as dry as was anticipated.”
“On the Big Island, the windward areas (were) about 50% to 80% of average, and then the rest of the Big Island, most of the totals were definitely in the below-average category,” Kodama said. “Hilo airport ended up with the seventh-driest wet season in the last 30 years.”
According to Kodama, the dry season started as forecast in October, but took several shifts and turns.
“October and even into November was pretty dry. We had below-average rainfall … through most areas of the state,” he said. “And then, from November through January, we had several rain events that occurred that kind of took the edge off drought, mitigated some of the drought impacts and kind of brought some relief. …
“And then February and March came around, and things dried out again, so this was the time of the wet season where I felt like, ‘See, I told you, here’s the dryness.’ And we actually had severe drought pop up again on portions of Maui and the Big Island. And then, mid-April, right toward the end of the wet season, when things should start calming down, we had a big mid-month heavy rain event. … But that rainfall never reached the east half of the state completely, so we still had some dry conditions on Maui and the Big Island. So, drought persisted in that part of the state.”
Kodama said it was a reminder that meteorology, despite technological advances, is still an inexact science.
“It was one of those things where you think you know, have a pretty good handle on the situation. Our forecasts at the time, we had a high level of confidence. And you think you’ve got things under control, and you know what’s going on. Mother Nature comes around and says, ‘No, you don’t.’”
Email John Burnett at jburnett@hawaiitribune-herald.com.