For much of May, most of Hawaii Island’s rain gauges were measuring near- to below-average amounts of rainfall, as the National Weather Service in Honolulu predicted in its dry season outlook for May through September.
There was one notable exception — the Kona coffee belt, which experiences its wet season in the summer. That said, it was even wetter than usual.
And one coffee belt gauge, Kealakekua, posted its highest May rainfall total on record, 12.86 inches, 240% of its average May rainfall total, and over 3 inches more than the previous May record, 9.76 inches.
“It didn’t just squeak by on the record; it was a significant margin, so it’s pretty notable,” Kevin Kodama, NWS senior service hydrologist, said Thursday. “And it wasn’t just that site. All of the gauges in that area picked up a pretty good amount. You look at the percent of averages, it was all at, above, or just below 200% of average.”
Kealakekua also had the Big Island’s highest one-day rainfall total of 2.28 inches on May 3.
The other three official coffee belt gauges Kodama referred to are: Kainaliu, which registered 10.57 inches, 204% of its May norm; Honaunau, which measure 9.33 inches, or 196% of average; and Waiaha, which had 7.94 inches, 170% of its usual May.
One unofficial leeward gauge, at Holualoa, in upslope North Kona, tallied 14.99 inches.
“May is just getting things started. Actually, the peak doesn’t occur until later,” Kodama said of the summer wet season for leeward slopes. “So it’s pretty early to be ramped up like this. Overall, we’ve had some instability, but they’ve been getting rain, like, everyday — and in decent amounts.”
Not all Kona locations shared in the rainfall bounty, however.
Ellison Onizuka Kona International Airport at Keahole, where tourists on the tarmac are almost always greeted by sunshine, registered just 0.9 inches for the month, 45% of its usual 2 inches. Puuanahulu was even drier at 0.77 inches, just 34% of its May average of 2.25 inches.
Windward monthly totals were mostly in the range of 60% to 100% of average. Glenwood, in the upper Puna rainforest, had the highest monthly total of 13.74 inches, 86% percent of average.
The rain gauge at Hilo International Airport tallied 6.17 inches, just 76% of its May average of 8.12 inches. Due to a wetter-than-average rainy season, however, the airport’s year-to-date total of 69.56 inches is 134% of its average for the year’s first five months, 51.91 inches.
Piihonua, in the foothills above Hilo town, hit double-digit rainfall in May, checking in at 10.78 inches, 80% of its May norm of 13.48 inches. Piihonua also has the distinction of being the first official NWS rain gauge on the Big Island to crack triple digits for the year, with 100.98 inches of rain, 31% above its year-to-date average.
“The trades have been there most of the month but it’s not been super wet. It’s been kind of what we were expecting,” Kodama said. “… The way drought manifests itself on the windward side of the Big Island, windward slopes, anyway, is you’ll get rain every day or almost every day. But it’s just that the amount of rain is lower than what you’d expect normally. And that’s what’s been occurring.”
And while most of East Hawaii has remained green, so far, other parts of the island are slipping into drought conditions. In his last drought statement, dated May 8, Kodama wrote “With the exception of the Kona slopes of the Big Island, leeward areas of the state may see increasing drought conditions during the summer.”
That assessment is borne out in the numbers.
The Waimea Plain gauge received just 0.91 inches for the month, just a third of its usual 2.61 inches, bringing it to 8.8% for the year, just 40% of its norm of 22.08 inches. And Honokaa also got about a third of its normal May rainfall, 2.3 inches, bringing its total for the year to 40.13 inches, almost 20% drier than normal.
“It’s been creeping along in leeward Kohala and up in the Pohakuloa region it’s been drying out,” Kodama said. “I just found out (Thursday) that even the Honokaa area is drying out. Parts of (Hawaii Volcanoes) National Park are getting dry, too — the windward side not so much, but more in the lee of Kilauea volcano it’s been drying out.
“And even on the windward side, stream flows in Honolii Stream and Wailuku River are trending downward.”
Email John Burnett at jburnett@hawaiitribune-herald.com.
