The final month of 2021 was “one of the wettest Decembers in the last 50 years,” according to Kevin Kodama, senior hydrologist for the National Weather Service in Honolulu.
In January, however, it was like some unseen hand turned off the spigot in the sky over Hawaii.
Not a single official rain gauge on the Big Island recorded above-average rainfall last month. Only Puu Waawaa’s total of 2.6 inches — 86% of average — managed to approach near-average territory.
And the majority of the Big Island’s monthly rainfall totals were less than 30% of average in January.
With 0.18 and 0.52 inches, respectively, the Kamuela and Kamuela Upper gauges recorded their lowest January totals on record. And the 1.2 inches of rainfall at Hilo International Airport marked its lowest January total since 2010, just 15% of its average for the month.
In fact, January’s aridity is a far cry from what was forecast in a NWS media briefing in mid-October about the outlook for the wet season — which is October through April for most of Hawaii.
“This is not what we were anticipating — certainly not with what the guidance was showing,” Kodama told the Tribune-Herald on Tuesday. “Even in December, after all that rain, we thought, ‘Wow, we’ve gotten more than what we were expecting.’ … The longer-range (computer) models were still showing above-average rainfall for January, February and March. And then, January rolls around, and that whole wet pattern goes away … and the medium-range models started to back off on above-normal rainfall.”
For the second straight wet season, Hawaii is in a La Nina weather cycle, which Kodama described as an “unusual or anomalous cooling” in equatorial Pacific waters. It’s the opposite of El Nino, and both have an impact on weather.
“It’s been an interesting pattern, to say the least, because the way the dryness has set in, it looked like a El Nino rainfall pattern — but it’s not El Nino, it’s La Nina,” Kodama said. “In recent years, La Ninas have been drying up, but its been more of a regional dryness. And what I mean by that is, when we’ve had a La Nina, we’ve had a moderate-to-strong tradewind pattern. So the windward slopes get wet but the leeward sides stay dry, because it’s trades.”
This year, thus far, looks “really different,” according to Kodama.
“It’s a statewide dry pattern, ever since Jan. 3 — and earlier for the Big Island,” he said. “The sudden shift to a persistent dry pattern has already resulted in moderate drought conditions in Maui County and the Big Island due to low rainfall and stream flow conditions.”
Even Glenwood, in the upper Puna rainforest, had an unseasonably dry January, with just 2.16 inches of rain, 11% of its January norm of 19.45 inches.
On the leeward side, Ellison Onizuka Kona International Airport at Keahole kept the sunshine coming for Big Island visitors, with 0.02 inches of rain for the month, a paltry 1% of the usual January rainfall.
Of the four Kona coffee belt gauges, Waiaha was the only one to record more than 1.5 inches of rain, less than half its usual January total.
A dry month means less water in the catchment systems of residents who aren’t on county water.
Aileen Andaya, who operates Alaloa Water Hauling in Hilo with her husband, Domingo, described January as “very busy.”
“When it hasn’t been raining for a week straight, that’s when people start calling,” Andaya said.
Andaya said much of the company’s business is in Puna, up to Volcano.
“We would do Hamakua, but because of the Kolekole Bridge, we cannot. The farthest (north) we can go now is Pepeekeo,” she said, noting a truck with 1,000 gallons of water is heavier than the 12 tons currently allowed on the bridge, which is undergoing emergency structural repairs.
Asked when rainfall might again pick up, Kodama said computer models are “still showing March is going to be wet.”
“In more recent times, March has been pretty wet consistently. And, in fact, it’s become the month with the highest frequency of flash flooding,” he said. “It used to be that November was the No. 1 month for flash flood frequency and October was No. 2, but over the course of the last 10 years or so, it’s kind of shifted. In 2020, March took over from November for highest flash flood frequency.
“So, we’ll see what it does.”
Email John Burnett at jburnett@hawaiitribune-herald.com.