KAILUA-KONA — A large swath of Hawaii Island emerged from abnormally dry conditions and other areas got some reprieve from drought following above-average rainfall over many areas during July.
However, the northern tip of the state’s southern-most island didn’t fare so well, seeing drought conditions worsen from D1 “moderate” at the start of July to D2 “severe” and D3 “extreme drought” by Thursday, according to the U.S. Drought Monitor and National Weather Service hydrology data released this week.
Big Island rainfall during July reflected a wide range of conditions, according to the July rainfall summary published Wednesday by the National Weather Service’s Senior Hydrologist Kevin Kodama in Honolulu.
Several gauges in Kohala and Hamakua had below-average rainfall during June while locations in South Hilo and Puna recorded near-normal rainfall totals. Kona, Ka‘u and leeward Kohala gauges posted above-average monthly totals.
Kodama noted the below-average rainfall over some areas could possibly be attributed to a shift in trade wind direction. As occurred in June, trade winds were mainly straight from the east, or east-southeast, instead of from the east-northeast. An area of low pressure has been sitting north of the state since about February, resulting in the veering of the winds.
“The slight shift in the prevailing wind direction has shifted rainfall patterns on the islands as well, resulting in persistent dryness over central Oahu, windward West Maui, and the windward Kohala and Hamakua slopes of the Big Island,” Kodama wrote.
Tom Birchard, lead forecaster with the National Weather Service’s Honolulu office, said the trade pattern is expected to persist through next week, though some models are showing trade winds returning to the more typical direction by the end of the week.
“There are some clouds and showers coming in the short term, but the overall look is a relatively settled pattern as far as winds not being very strong and rainfall not being very widespread,” he said.
The highest monthly total rainfall for July was recorded at the Saddle Road Quarry in East Hawaii, where 25.34 inches of rail dropped, or 204% of average. About a third of that fell on one day, July 8, as the remnants of Tropical Cyclone Barbara passed dropping 7.37 inches.
Those remnants also brought precipitation to the west side of the island, and the lingering moisture thereafter helped boost rainfall over leeward areas through July 11.
Honaunau recorded its highest July rainfall total since 1993 with 11.3 inches falling during the 31-day month, Kodama said. Kealakekua saw its highest July total since 2004 with 11.24 inches of rainfall. The percentage of normal rainfall was 169% and 163%, respectively.
North Kona areas recording above-average rainfall during July were Puuwaawaa, which saw 381% of normal rainfall with 6.47 inches dropped; Waiaha, which recorded 251% of normal rainfall with 12.03 inches; and normally dry Kaloko-Honokohau National Historical Park, where gauges recorded 243% of normal rainfall or 4.05 inches of rain.
Even South Kohala areas like Waikoloa, where extreme fire danger signs are posted year-round, saw above-average rainfall during the month. According to the hydrological data, Waikoloa saw 356% of its average rainfall, receiving just over 1.5 inches, during July. The area typically is afforded just 0.43 inches that month.
In Ka‘u, Kahuku Ranch saw 7.34 inches, or 169% or normal, while lower Kahuku recorded 7.16 inches, or 150% of normal rainfall, during July. Gauges at Pahala and Kapapala Ranch all recorded at least 124% of normal rainfall.
Hamakua and areas of North Kohala weren’t so lucky. Honokaa, which typically measures 7.33 inches of rain during July received just 4.37 inches — or 60% of normal rainfall. Laupahoehoe recorded just 39% — 5.18 inches — of its July average of 13.45 inches. Data for Upolu Airport in North Kohala, which falls in the middle of the worst drought conditions on the island, was not available for July.
On the year, rainfall totals are near- to below-average over most Big Island areas, according to Kodama.
Hilo International Airport, which on average sees over 70 inches of rain by the end of July has recorded just 47.99 — or 68% of average. Mountain View has seen just 73% of its average rainfall with 72.73 inches through July 31. Laupahoehoe has recorded 68% of its average rainfall. Waimea and North Kohala areas have seen about 80%-90% of normal rainfall
North Kona and South Kona are exceptions, however, Kodama said noting there were a handful of sites in the two leeward districts that have seen above-average year-to-year totals. Waiaha and Kealakekua have received the most rain, with 157% and 135% of average rainfall, respectively.
Tim Samuel, with Kona Joe Coffee in Kainaliu, where more than 8 inches of rain fell during July, said this year’s harvest appears to be better than last year’s, which was impacted by heavy vog that blanketed the island amid the 2018 Kilauea volcano eruption.
With vog-free conditions this year, the 20-acre farm that grows its coffee on trellis has been receiving ample sunlight, as well as the typical afternoon rains for which the Kona coffee belt is known. To the best of Samuel’s knowledge irrigation hasn’t been used this season.
“In terms of this year, I think there’s been enough rainfall to take care of itself,” Samuel said Friday afternoon. “There’s enough of a rainfall in the later afternoon and evening time that it hasn’t been too much of a problem.”