As Hurricane Dora passes south of the Big Island today, there will be what National Weather Service meteorologist Kevin Kodama described as “peripheral effects.”
“The hurricane itself is pretty small,” Kodama told the Tribune-Herald on Monday. “But as it passes south of us, there’s a strong high-pressure system to the north. We’re going to get pretty strong winds — and the surf is related to the strengthening trades, as well. We’re also going to see a slight bump up in the southeast from the hurricane swell.”
A high wind warning is in effect for much of the Big Island until 6 a.m. Wednesday. Affected areas include leeward and mauka regions plus North Hawaii, with easterly winds of 30 mph to 45 mph and gusts over 65 mph expected.
For coastal windward areas of the island, a high wind advisory is in effect until 6 a.m. Wednesday. Expected are northeast winds 20 mph to 35 mph, with gusts over 50 mph.
According to forecasters, damaging winds can blow down trees and power lines and damage roofs. Power outages are possible. Residents are advised to secure loose outdoor items or to bring them inside.
A high surf warning is in effect until 6 p.m. tonight for east-facing shores, due to a combination of strong trades, large seas and a moderately sized easterly swell generated from Dora.
Also posted by forecasters is a relatively rare red-flag warning until 6 a.m. Wednesday for leeward portions of the island due to strong winds and low humidity. A red-flag warning is a public notification that conditions are optimal for wildfires to occur, although its not a prediction the wildfires themselves will happen.
“There are several things that go into that,” said Kodama. “There’s the wind, the (lack of) humidity, the warmth. Maybe a little less so in the South Kona district, but the emphasis is in the North Kona and South Kohala districts, where the winds can get pretty strong.
“A lot of the fuels that can become a wildfire came back because of the wet season, so that whole area around Waikoloa, the upper Hawaii Belt Road and down toward the Kawaihae area — any place that had dry fuels — that’s all going to be pretty vulnerable.”
According to the weather service, humidity has been 35% to 45% during afternoons and evenings in the affected areas, and any fires that develop will likely spread rapidly.
While Dora will have some effect on the Big Island, the former Tropical Storm Eugene, which is still in the Eastern Pacific far to the northeast of Hawaii, has dissipated into a post-tropical cyclone and should have little to no impact on Hawaii.
The combination of Dora and the high-pressure system to the north have accelerated the drier conditions that started last month for much of the island.
July rainfall totals were near to below average at most of the gauges on the Big Island. Most of the above-average totals were along the Hamakua Coast, in part due to rainfall associated with Tropical Storm Calvin.
Some gauges recorded 5 inches to 7 inches of rainfall over the east and southeast flanks of the Big Island during the 24-hour period ending at 8 a.m. July 19. The rapid movement of Calvin toward the west helped mitigate exposure to much higher rainfall totals and more serious flooding.
“Calvin didn’t really do a whole lot,” Kodama said. “It helped a little, of course, but even on the Hilo side, even with the Tropical Storm Calvin rainfall, a lot of the numbers still ended up below average. And my understanding is the benefit of that has gone away already. It’s pretty hot and dry, so the trend for drought is back on track.”
The highest 24-hour total due to Calvin was 7.24 inches at the Honolii Stream rain gauge. Locations in North Kona and South Kohala were quite dry, with several recording July totals at less than 30% of average.
Ellison Onizuka Kona International Airport at Keahole and Hilo International Airport had their lowest July totals since 2008 and 2013, with 0.03 inches and 4.97 inches, respectively.
Kona airport’s total was just 6% of its July average. And Hilo airport checked in at just 54% of its July norm, despite having measurable rainfall on 28 out of 31 days in July, but a daily average of just 0.16 inches.
The long-term July average at Hilo airport is measurable rain on 27 days, and a daily average of 0.3 inches.
Email John Burnett at jburnett@hawaiitribune-herald.com.