By COLIN M. STEWART
Tribune-Herald staff writer
The islands of Oahu and Kauai were battening down the hatches Friday in expectation of heavy rains, but East Hawaii can look forward to a sunny weekend, according to the National Weather Service.
A cold front was approaching the state from the west, bringing “unsettled weather” with it, said hydrologist Kevin Kodama with the National Weather Service in Honolulu. But a wall of high pressure to the northeast will likely keep the cold front from moving past Oahu, leaving the Big Island with clear skies.
“Right now, we have a Flash Flood Watch for the Islands of Oahu and Kauai,” he said. “That means the conditions are favorable for heavy rains that could produce flash flooding, but there are no guarantees, of course.”
A Hawaii area synopsis posted at 10 a.m. Friday on the NWS website predicted the possibility of thunderstorms an localized heavy rainstorms in affected areas through early Sunday morning. The cold front was expected to stall over the western half of the island chain and slowly dissipate.
“High pressure will build back in the northeast of the state next week with trade winds returning,” the website read.
The weather service has been monitoring the situation closely all week, Kodama said, something that could not have been done with much precision more than a decade ago.
“Ten or 20 years ago, the models had a hard time figuring out what would be happening in just the next 24 hours,” he said. “On this Flood Watch, we actually started looking at it the end of last week. The (computer) models were starting to give hints that we might be in an unsettled pattern this weekend.”
The science of weather forecasting has long been derided by some members of the public as being an inexact one, but the technology and its resulting forecasting has been improving in recent years, Kodama said.
“Nowadays, the computer models are getting better and better,” he said. “In the past, we wouldn’t go out more than a day or even 12 hours ahead, with a Flash Flood Watch. … But the computers models have gotten so much better, especially the farther you go out in time (ahead of an expected event). We’ve got higher resolution, better computing power, and better data going into the models. And the model equations themselves have been refined.”
Forecasters in the state of Hawaii find themselves in a unique and difficult situation compared to their counterparts on the mainland, Kodama added.
“We just don’t have the data that the mainland has,” he said. “We’re the most geographically separated land mass in the world, so it makes it difficult to make accurate predictions. On the mainland, say you’re in St. Louis, you have the data from surrounding areas, but here we just don’t have the number of surface stations and balloon soundings and aircraft data around us.”
But, he added, while technology is picking up some of the slack, experience still remains one of a forecaster’s most prized tools.
“With operational forecasting, you need experience,” he said. “You develop through your successes and your failures a much better sense, and you learn, hopefully, how to do better each time.”
On the subject of recent rainfall in East Hawaii, the weather service reports that drought conditions continue to persist in the hardest hit regions, although some areas did see some relief as the wet season draws to a close.
“Limited rainfall occurred in late march over the existing extreme drought areas … on the Big Island and the island of Maui,” reads an NWS drought update for the month of March. “Localized showers on the western side of the Pohakuloa region on the Big Island allowed for a small amount of improvement … (but severe drought) areas remained unchanged. On the lower Kona slopes … rainfall activity helped bring severe drought down to the moderate level.
Email Colin M. Stewart at email@example.com.