Much of the Big Island received normal to near-normal rainfall totals in November. In some areas, however, especially in East Hawaii, much, if not most fell on Nov. 4.
That’s according to the monthly precipitation report prepared by Kevin Kodama, senior service hydrologist for the National Weather Service in Honolulu.
“And since then, it’s been pretty dry,” Kodama told the Tribune-Herald Tuesday. “We’re in this sort of dry spell in the North Pacific right now, at least in our area. It’s not quite expected, but it’s looking like rainfall should pick up, at least, in January onward, so luckily, we got what we did in November.”
On Nov. 4, a low-level trough with deep tropical moisture moved over the Big Island from the east. That combined with unstable conditions aloft and mountainous terrain to produce a prolonged period of heavy rainfall. More than 5 inches of rain covered the eastern third of the island, with bias-adjusted radar estimates indicating more than 15 inches of rain over the slopes northwest of Hilo.
The U.S. Geological Survey rain gauge at Honolii Stream north of Hilo had the highest monthly total of 31.66 inches — 129% of average — and the highest daily total of 11.47 inches on Nov. 4. That location has recorded an eye-popping year-to-date total of 221.87 inches, the highest total on the island and slightly above its year-to-date norm.
Waiakea Uka, in the Mauna Loa foothills above Hilo, received 24.74 inches of rain in November, with 10.63 inches of it occurring on Nov. 4.
Hakalau, north of Hilo, had 12.81 inches, 21% above its monthly average, with 7.3 inches coming on Nov. 4. Pahoa was doused with 18.58 inches in November, more than 2.5 inches above its norm, with just 5 inches falling on Nov. 4. And the official gauge at Hilo International Airport tallied 13.36 inches for the month, 93% of norm, with 4.1 inches on Nov. 4.
It also was wet in Ka‘u that day, with Kapapala Ranch recording 8.5 inches, almost twice its monthly norm, and 6.91 inches that day. Pahala’s monthly total of 6.96 inches was only 88 percent of its November average, but 5.8 inches of it fell on Nov. 4.
The resultant flooding that day closed several roads in South Hilo, Puna, and Ka‘u, including Highway 11 near Kawa Flats southwest of Pahala.
In West Hawaii, most locations in North Kona and North and South Kohala experienced below average rainfall for the month.
Ellison Onizuka Kona International Airport at Keahole, where sunshine almost always greets visitors during daylight hours, registered just 0.48 inches, just 58 percent of its November norm, but more than half of that total, 0.31 inches, fell Nov. 4.
The Kona coffee belt experiences its rainy season in the summer and is currently in its dry season, but all four of its gauges measured at least 30% more than its November norm. Waiaha led the way with 5.46 inches, followed by Kainaliu with 4.75 inches, Kealakekua with 4.28 inches and Honaunau with 4.05 inches.
“Most of that rain came early in the month,” Kodama said. “But since then, they’ve been pretty dry, also. It’s been a uniform dryness. And when we have had trade winds, they haven’t been getting them.
“And on the Hilo side, even though you’ve been getting rain the last couple of nights — some trade wind showers — overall, for the month, we’re kind of way behind at Hilo airport compared to normal for this month.
“You know, December’s supposed to be one of the wetter months of the year in Hilo. And even though you’ve gotten some rain, it’s still pretty dry. You’re behind the pace, right now.”
In fact, the National Weather Service posted a red flag warning Wednesday for the leeward side of all Hawaiian Islands, including the Island of Hawaii, until 6 p.m. tonight, as the combination of dry fuels, low relative humidity, and strong trade winds have brought critical fire weather conditions for leeward sections of the state, including the Big Island.
Kodama, however, stood firmly behind NWS’s forecast, made in October, for a wetter-than-normal rainy season for the Big Island.
“The prediction, at this point, is for January onward to be pretty wet,” he said. “Sometimes, these subseasonal anomalies happen. When you have a weak La Nina or weak El Nino event, it’s not dominant enough so you can drown out everything else. There are all these climate cycles — and sometimes, they reinforce each other, sometimes they compete against each other. So when your El Nino or La Nina is weak or you have neutral conditions, other cycles can come in and play a role. I think that’s what we’re seeing here.”
The prediction also was for La Nina to take effect during this wet season — which hasn’t yet happened.
“It’s still trying and it’s kind of stalling,” he said. “And that’s what it’s been looking like for a little bit, even though the Climate Prediction Center is still favoring La Nina development. … The La Nina watch is still in effect, but the window is closing and we’re not there yet.”
And although parts of other islands are in severe and even extreme drought, the early November drenching on the Big Island resulted in the drought monitor showing only part of the northwestern portion of the island as abnormally dry, with an even smaller sliver in moderate drought.
“That’s as of last Thursday,” Kodama said. “We’ll see what happens (today), when it gets updated. It’s been dry now consistently and the upstream numbers from the USGS are coming down, so I wouldn’t be surprised if on the drought monitor, at least the … abnormally dry section expands when the new update comes out.”
Email John Burnett at jburnett@hawaiitribune-herald.com.
