LIHUE — Officials are forecasting above average rainfall for the Aloha State through April, according to a report from the National Oceanic and Atmospheric Administration.
The Wet Season Rainfall Outlook for the State of Hawaii calls for normal to above-average rainfall for the wet season, which spans from October 2016 to April 2017. According to the outlook, which was released Thursday, rain during that time period may assist with the drought conditions on Kauai.
“It’s been interesting because windward side has been wet, but the pastures out in Hanapepe and extending out to Waimea side have been dry,” said Kevin Kodama, service hydrologist with the Honolulu National Weather Service. “That’s coming from not just the rainfall data, but the USDA Farm Service agency.”
“Those areas with lingering drought — like Hanapepe on your island and Kihei area in Maui — I fully expect by the end of April there going to be recovered,” Kodama added. “They’re going to see rain events in the next several months that will restore vegetation conditions back to what they should be.”
The outlook is also predicting a 55 percent chance of La Nina to transition from the current ENSO-neutral conditions.
ENSO-neutral (El Nino/Southern Oscillation) is is the period between El Nino and La Nina. During these periods, ocean temperatures, tropical rainfall patterns and atmospheric winds are near the long-term average, according to the NWS Climate Prediction Center.
“With recent weak La Nina, which is expected, the rainfall across the state tends to be around average,” Kodama said. “With ENSO-neutral, we tend to be wet. Because it’s transitioning into La Nina and and transitioning out, it makes it harder to nail down which identity it latches on to. That’s why the forecast calls for near to above. There’s a lot of uncertainty there.”
Indicators for La Nina include above-average rainfall over the far west Pacific over Indonesia, above-average sea levels in the western Pacific and above-average east winds over the western Pacific.
“The circulation is shifting westward, which is one of the ways La Nina defined,” Kodama said. “We’re starting to see these signs, so that’s why the center came up with La Nina watch. La Nina may be developing pretty soon.”
Long-range climate models are also favoring wet conditions, Kodama said.
“It looks like if it forms, it will be weak,” he said. “The early part of early 2017, it might be transitioning back out of La Nina into ENSO-neutral. That makes the forecast harder, too. You’re in these transitioning stages and you don’t know which way to go.”
The summary for the dry season — May through September 2016 — had the second wettest dry season in the last 30 years for the islands, based on rankings from eight key sites in the state.
“It would have broken a lot records, but last year was the record breaker,” Kodama said. “Some places were the wettest. It wasn’t even close. On Kauai, I’m using Lihue Airport as an indicator site. It’s been dry. It was dry at Lihue Airport. It ranked 27 out of 30 with one being wet and 30 being driest. The other sites like Manoa, Lyon Arboretum, Honolulu Airport, Manoa had its wettest dry season in 30 years. Honolulu Airport, Kahului Airport and Ulupalakua Ranch on Maui had their second wettest.”
Even with Lihue being dry, other places around the state leaned toward wet, he said.
“You can just tell without looking at the rankings the number of events that you guys had,” he said. “Pretty much everything was Oahu and eastward. You guys didn’t have too much (wet conditions).”
Tropical cyclones and other tropical weather brought associated rain bands over the islands and increased and enhanced moisture in Hawaii during the dry season. These factors as well as above-average sea surface temperatures have helped to increase rainfall.
Officials are advising members of the public to be aware of the changing weather conditions.
“You guys know about the risk over there ( with Hanakapiai),” Kodama said. “With this time of year, you’re going to have higher chance of flood events along the Na Pali coast, especially Hanakapiai Stream — just because of the time of year and we’re projecting wetter than normal conditions. If you do go hiking and you get stranded, don’t attempt to cross. Just wait it out. You might be wet and miserable, but at least you’ll be safe.”
In Hawaii, Kodama said, streams come up very quickly, but also water levels can go down very quickly.
“If you just wait it out, you’re much better off,” he said.