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June juxtaposition: Kona seeing wetter than normal rainy season as rest of island dries out

Ample rainfall continues to fall over much of Kona sparing the area from drought that has taken hold of most the island.

“For two months in a row now, the Kona side has had the most rain on the Big Island. The peak monthly totals are from the Kona side, and for two months in a row now there’s been monthly records broken,” said National Weather Service Senior Hydrologist Kevin Kodama. “It’s interesting.”

Most totals from the Kona slopes region were from 6 inches to more than 10 inches during June, with most of the rainfall likely occurring the afternoon of July 19. That’s when an unusually strong low-pressure system moved closer to the state, weakening the typical tradewinds, allowing land and sea breezes to interact. The rainfall resulted in minor flooding, and a brief partial closure of Queen Kaahumanu Highway.

The morning following the rainfall event, a manually read volunteer network gauge in Holualoa reported the highest daily total at 3.73 inches.

For the month, the same gauge reported 11.22 inches of precipitation, marking the second consecutive month the area reported the highest monthly rainfall total on the island. In May, Holualoa saw 14.99 inches of rain. At nearby Waiaha, the automated gauge recorded 9.78 inches of rain — 185% of the average 5.28 inches seen during June.

Heading south, gauges along the Kona coffee belt recorded monthly totals well over average.

In Kainaliu, 9.54 inches fell, nearly 3.75 inches more rain than the monthly average. Kealakekua saw 167% of its average rainfall for June with 10.11 inches of rain — its highest June rainfall total in a data record going back to 1991. The Honaunau area gauge reported just over average rainfall at 6.58 inches.

The months of above-average rainfall have kept all of those gauge’s yearly totals well above average, with Kealakekua seeing 170% of average rainfall with a whopping 44.02 inches of rain — 18.09 inches — a foot and a half — more than average at the half-way point of the year.

“It’s wetter than the normal wet season, despite everywhere else being dry,” said Kodama, though he’s unsure exactly why, admitting he hasn’t yet had time look at the information in a lot of detail. “Just on face value, the reasoning is not entirely obvious. Especially when the other side of the island has been generally quite dry, and just north of the Kona slopes has been pretty dry.”

More northward areas of Kona didn’t see as much rain during the month of June, with the exception of typically dry Kaloko-Honokohau National Historic Park, which recorded 2.66 inches of rain, 156% of average. Not far north, Kona International Airport reported less than a half inch, or 46% of average, and Puuanahulu nearly an inch, or just 49% of average.

For the first six months of 2021, the Kaloko-Honokohau gauge has recorded 105% of average rainfall at 10.68 inches. Kona International Airport and Puuanahulu have seen 92% and 69%, respectively, of average rainfall.

Heading to South Kohala, Waikoloa saw 141% of average rainfall during June with 0.89 inches falling during the month, bringing to 91% of average rainfall for the year.

But go upcountry, about 10-15 miles north to Waimea, and the average yearly rainfall is down, following a June where the area’s three main gauges saw no more than 73% of average rainfall with the Waimea Plains gauge reporting just 21% of average rainfall for the month. The exception was the Kawainui Stream gauge, above and on the windward side of Waimea, where monthly rainfall was 112% of average at just over 11 inches.

The Waimea Plains gauge during the first six months of the year has reported 9.38 inches, which is just 38% of the average 24.81 inches, while the Kamuela gauge has seen just under 15 inches, about 44% of average. The Kamuela Upper gauge is fairing a little better with nearly 22 inches of rain, about 63% of average. For the year, the Kawainui Stream gauge is at just about average rainfall at 79.33 inches.

Over Kohala Mountain Road, it was a dry June with Upolu Airport in North Kohala recording 0.37 inches of rain, just 13% of average — the lowest June rainfall total since 1991. For the first half of the year, the site on the island’s northern tip has seen less than half of average at 10.38 inches of rain.

Kahua Ranch didn’t do much better, reporting 28% of average rainfall, with 1.13 inches of rain during June; yearly data was not available. An anomaly was Kohala Ranch, where just over 4 inches of rain fell during June, or 573% of average. For the year, Kohala ranch has seen 10.24 inches, or 155% of average.

Many of the monthly totals for June from the windward districts, including Hamakua, Hilo and Puna, were in the range of 2 to 6 inches. Honokaa reported 2.45 inches of rain, 53% of average for the month, while the Hilo Airport area saw rainfall for the month at just 31% of average or 2.26 inches. Mountain View, Pahoa and Kulani gauges each saw rainfall less than 50% of average for the month.

On the year, Honokaa’s seen 42.58 inches of rain — 79% of average — while the Hilo Airport area gauge reported 121% of average rainfall at just under 72 inches. The gauges at Mountain View, Pahoa and Kulani are all over 119% of the average for the first six months of the year.

Things aren’t forecast to get much better for leeward areas with dry conditions expected to persist possibly longer than the typical dry season, which began in April and normally runs through September for areas outside Kona. On June 28, the U.S. Department of Agriculture declared Hawaii County to be a natural disaster area due to the drought, making farm operators here eligible for Farm Service Agency assistance.

Areas of South Kohala, extending from Kawaihae up into the dry side of Waimea, already experiencing severe drought could see extreme or even the worst category or drought — exceptional — take hold, said Kodama.

East Hawaii areas currently seeing moderate drought could see severe drought set in. Most of Ka‘u, like Kona, is not experiencing drought, with just a strip along the southeastern coast near South Point, which has seen 131% of average rainfall so far this year with 21.72 inches recorded, being listed as abnormally dry.

“Exceptional drought” is classified by the National Drought Mitigation Center when there is widespread crop/pasture losses; as well as shortages of water in reservoirs, streams, and wells creating water emergencies.

“There’s still potential for that, especially if we get a late start to the wet season or even if ends up being primarily on the windward side and the leeward side stays dry which is also a possibility because there’s a decent chance we might get a repeat of La Nina,” said Kodama.

The National Weather Service’s Climate Prediction Center in its Thursday update forecast a La Nina to potentially emerge sometime between September and November and last through January 2022. A La Nina is identified by colder than normal water along the equatorial Pacific, and is the opposite of El Nino. During La Nina, Hawaii tends to see above-normal rainfall during the winter months, or the wet season.

“Depending on how strong that La Nina is, we could end up with the Leeward side staying dry during the wet season,” Kodama explained. “That’s what happened in the 98-2001 drought we ended up with three years in a row of La Nina but leeward areas stayed generally dry that hole time. It ended up being a pretty persistent drought.”

All in all, “it’s just going to get worse, barring a tropical cyclone or something, but even with one, the rainfall tends to be on the east side still,” said Kodama, pointing people to look back to Hurricane Lane in 2018 that dumped over windward areas, dropping 3 to 4 feet of rain, but leaving leeward Kohala areas relatively dry.

The most likely outcome is “not real good for the leeward Kohala slopes.”

“And we’re talking all the way through the summer and into the early fall because initial indications are that we might have a late start to the wet season — so even October into November might be dry too,” continued Kodama. “It’s kind of problematic. I’ve seen pictures from the slope between Waimea and Kawaihae, and I know it’s normally dry that time of year, but it looks pretty bad out there.”

Ranchers and agriculture officials reported continued poor foraging conditions in the Waimea, Mana, and Hamakua regions of the Big Island during June, according to Kodama. Satellite-based vegetation health data also showed deteriorating rangeland conditions in the Saddle area.

“It becomes an impact financially — it’s just expensive to have to supplement feed and haul water. I don’t know if they’re already thinning their herds, but that’s another possible impact as well,” Kodama said, noting one rancher on the southeast flank of Haleakala on Maui has reported having to thin his cattle and goat herds.

“That’s the kind of thing that they do when the pastures can’t support the size of the herd. I haven’t heard of that going on on the Big Island — I’m not saying that’s not occurring, but I haven’t heard anything about that yet,” he added.

Fire is also a major concern.

“Especially the areas that haven’t had a fire recently and the fuels have grown — they have an increased, bigger vulnerability,” said Kodama, noting things will continue to be hot and dry with “nothing significant coming our way” over the next couple of weeks. “As we get toward August, things are going to be pretty crispy and hotter.”

Email Chelsea Jensen at
Source: Hawaii Tribune Herald

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