Kevin Kodama, senior service hydrologist with the National Weather Service in Honolulu, outlines predictions for Hawaii’s wet season that runs from October through April. The Maui News screenshot
A “pretty unusual” stretch of three straight La Nina seasons could mean that drought may not let up in Maui County and Hawaii island, even with above-average rainfall predicted for the upcoming wet season, a hydrologist said.
“We’re going into potentially our third year in a row of La Nina conditions in the wet season,” said Kevin Kodama, senior service hydrologist with the National Weather Service in Honolulu. “This has only happened twice before since 1950, so it’s a pretty unusual situation. So unfortunately for areas that are in significant drought right now in Maui County and the Big Island, there’s a chance that this drought can actually persist through the coming season.”
Oahu and Kauai in the west half of the state have a better chance of drought recovery, Kodama said during a news conference Wednesday while outlining the predictions for the wet season.
Three straight years of La Nina, the cyclical weather pattern of cooler sea-surface temperatures that alternates with the warmer ocean conditions of El Nino, is unusual but not unprecedented. When it happened in the past, it prolonged drought, just as is predicted to happen in Hawaii now.
“Back in ’97, ’98, we had a really strong El Nino,” Kodama recalled. “That started drought conditions. We had statewide drought and then after that, La Nina quickly developed, so by mid-1998 it flipped around from El Nino to La Nina and we stayed in drought all the way into I think 2002, when we finally recovered and we had a wet season. So yeah, it’s happened before.”
La Nina conditions could also be part of what contributes to large rain dumps instead of more measured showers. Kodama explained that the upper-level lows that forecasters have been seeing “make conditions really unstable for intense rainfall.”
He warned of the potential for flash flooding in March, which has recently seen an increase in such incidents, a switch from previous years when November and October used to be the first and second-most active months, respectively, for flash flooding.
Rainfall spread out over a period of time, instead of all at once, is what will truly help the soil recover from drought, according to Kodama.
“It’s not just one event that can solve it all,” he said. “You talk to ranchers, and they say, we need multiple events to get the soil moisture, for the water to percolate down and restore the soil moisture. And sometimes numbers can be deceiving, because you can have a really big rain event, and ah, the statistics say hey, you’re in good shape. But a lot of that just goes to runoff, goes out to the ocean, if it’s too much at one time.”
Under the current drought, some pastures across the state “are just dirt. It’s in really bad shape,” Kodama said.
During the dry season from May to September, multiple parts of the state reached the second-highest level of drought — with leeward areas of Maui County getting hit the worst.
This year’s dry season was the 16th driest in the last 30 years, based on rankings from eight key sites. But this was “a little deceptive, because the worst drought impacts were in areas where we weren’t sampling that rainfall,” Kodama explained. Some windward areas of Hawaii island, for example, recorded their lowest September rainfall since 2010.
Any relief the islands will experience during the wet season depends on the strength of La Nina, which is expected to be weak to moderate.
“If you have a stronger La Nina event where you have more persistent trade wind conditions, you end up having wet conditions over the windward slopes, and the leeward areas remain dry,” Kodama explained. “Now if you have a weaker La Nina, then you have a better chance of having more widespread rainfall.”
With the wet season now in swing, the National Weather Service advises people to:
• Avoid driving on roads with fast-flowing water. Just 1 to 2 feet can sweep away most vehicles or severely undercut roads.
• Avoid walking across flooded streams. Stranded hikers should wait for the water to recede, which generally happens quickly in Hawaii.
• Expect more rainy weather impacts, including increased travel times, possible detours due to flooding or landslides or changes and cancellations to outdoor activities.
• Be prepared for increased potential for lightning strikes as well as power outages, especially when thunderstorms are forecast. Move indoors at the sound of thunder or flash of lightning, as strikes can occur even in areas where it is not raining.
• Identify alternate routes ahead of time if traveling through a flood-prone area.
• Have an evacuation plan if living in a flood-prone area in case floodwaters threaten your home.
• Stay informed of conditions that could change rapidly by checking out the latest forecasts, watches, warnings and advisories via the media, NOAA weather radio, the internet or weather apps. Wireless emergency alerts on mobile phones can also notify users when they are in a significant, life-threatening flash flood warning area.
* Colleen Uechi can be reached at cuechi@mauinews.com.
Kevin Kodama, senior service hydrologist with the National Weather Service in Honolulu, outlines predictions for Hawaii’s wet season that runs from October through April. The Maui News screenshotToday's breaking news and more in your inbox
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