A downpour lasting several days late last month got much of Hawaii Island off to a wetter-than-normal start in January 2021.
According to the monthly rainfall report from the National Weather Service in Honolulu, a number of rain gauges in both East and West Hawaii recorded above average rainfall, with some measuring double the January norm, or more.
According to Kevin Kodama, NWS Honolulu senior hydrologist, a rainstorm Jan. 24-25 that dumped between 4 inches and 10 inches on a “large swath … along the southeast-facing slopes” of the Big Island was caused by a low-pressure system “combined with enhanced moisture in the low-level east-southeasterly winds.”
The rain caused brief closures due to flooding of secondary roads in South Hilo, Puna and Ka‘u, and a closure lasting several hours in the flood-prone Kawa Flats area of Ka‘u, bringing vehicular traffic to a standstill on Highway 19.
The precipitation in the last couple of weeks of January kept much of the island on par with Kodama’s prediction of a wetter-than-normal rainy season for the Big Island — which, for most of the island, runs from the beginning of October through the end of April.
Hilo International Airport had its highest January rainfall total since 2002, Kodama said, measuring 17.47 inches of rain, almost double its January norm of 9.26 inches.
The wettest populated spot on the island was Mountain View, which received 23.26 inches, 172% its January average of 13.54 inches.
Glenwood, in the upper Puna rainforest, was doused with 21.82 inches of rain, but that’s just 12% above its average of 19.45 inches for the first month of the year.
Other windward spots receiving significant January rainfall include Hakalau, with 14.65 inches — more than 2 1/2 times its norm — and Pahoa, with slightly more than 17 inches, almost 6 inches above its January norm.
Three of the four official rain gauges in the Kona coffee belt received above-average rainfall, with Kealakekua at 5.13 inches, Honaunau at 5.06 inches and Waiaha at 4.68 inches — all more than 140% of average January totals. For Kealakekua and Honaunau, those totals represent the wettest January since 2005.
The fourth gauge, at Kainaliu, measured 3.49 inches of rain, just below the January norm of 3.61 inches. It’s the dry season for the coffee-producing South Kona slopes, which has its wet season in the summer.
The slopes of the North Kona and North Kohala districts tallied mostly below-average rainfall totals for the month, with Kohala Ranch receiving 1.74 inches, 73% of norm.
Ellison Onizuka Kona International Airport and Kaloko-Honokohau National Historical Park registered slightly above-average January rainfall totals, with 2.46 and 2.34 inches, respectively.
Email John Burnett at jburnett@hawaiitribune-herald.com.