Most of East Hawaii experienced above average rainfall in May, easing what has been a drier-than-normal year. But above-average rainfall has been an even bigger boon to portions of the island’s leeward side, which is experiencing a drought.
According to Kevin Kodama, senior service hydrologist for the National Weather Service in Honolulu, rainfall in the first half of last month “helped to produce some drought relief.”
“The lower leeward slopes of the Kohala Mountains that were in exceptional drought, or the D4 category on the U.S. Drought Monitor map, have improved slightly,” Kodama said Thursday in a drought statement. “The area is now considered to be in extreme drought, or the D3 category. The extreme drought area between Kawaihae and Waimea has also eased to severe drought, or the D2 category. The severe drought area in the Pohakuloa region … has eased to moderate drought, or the D1 category.”
Nowhere on the island’s leeward side was the easing of the drought more apparent than at Kohala Ranch, which received 4.11 inches of rain in May, more than six times its average total for the month.
Despite the improvement, the drought is still very much a fact of life on much of the Big Island, Kodama said.
“Ranchers reported that pastures to the east of Waimea town improved following the early to mid-May rainfall, but have started drying out again,” he said. “Pastures along and above the Hawaii Belt Road between Waimea and the Waikoloa Junction have been very dry. A rancher operating in the leeward side of the North Kohala district reported that the May rainfall helped a bit, but … his pastures have been de-stocked for the last 12 to 14 months.”
The lack of rainfall also was apparent in the populated areas of Ka‘u, with Pahala measuring 1.94 inches of rain.
Kapapala Ranch and Kahuku Ranch tallied 1.54 and 1.28 inches, respectively, and South Point received just 0.88 inches — all well below the usual May rainfall totals.
“Kapapala Ranch had its lowest May total since 2012,” Kodama noted.
May is the beginning of the dry/warm season for most of the Big Island, with the exception of the Kona coffee belt slopes, which experiences its wet season in the summer.
Three of the four official rain gauges in the coffee belt area experienced slightly above-average rainfall, with Kealakekua recording 5.51 inches, followed by Honaunau with 5.24 inches and Waiaha with 4.77 inches. The other coffee belt gauge, Kainaliu, checked in at 4.86 inches, 94% of its May norm.
Other West Hawaii gauges also reflect a wetter-than-normal May, with Kaloko-Honokohau National Historical Park receiving more than twice its average rainfall for the month, at 3.83 inches. Also receiving above-normal May totals were Kaupulehu, with 2.39 inches, and always arid Ellison Onizuka Kona International Airport at Keahole, with 0.81 inches.
That said, Waiaha is the only gauge in a populated area of West Hawaii that’s measured above-average rainfall for the year-to-date, at 20.67 inches. The other coffee belt gauges are at 85%-90% of their average total for the first five months of the year, and the remainder of the leeward gauges are between 24%-73% of their average year-t0-date totals.
Rainfall was plentiful on the Big Island’s windward side. Waiakea Uka recorded 19.16 inches and Hilo International Airport reported 12.65 inches, the highest May total since 2006 for both spots. In upper Puna, Glenwood tallied 18.5 inches and Mountain View 17.99 inches, both wetter-than-average for May.
East Hawaii’s bountiful rainfall was fueled by heavy rains the first four days of May that caused flash flooding in some areas, Kodama said.
“Four-day rainfall totals of 10 to 15 inches were recorded in portions of the South Hilo and Puna districts, with 5 to 10 inches in the North Hilo and Hamakua districts,” he said.
While flooding occurred on the Big Island, no significant damage was reported.
Email John Burnett at jburnett@hawaiitribune-herald.com.