Despite dry November, 2018 still a wet year in East Hawaii

  • HOLLYN JOHNSON/Tribune-Herald Flood waters make the intersection of Kamehameha Avenue and Pauahi Street impassable Aug. 23 in Hilo.

Although most Big Island rain gauges posted near-to-below average monthly totals for November, the wetter-than-normal year continues into its final three weeks, according to data released Thursday by the National Weather Service in Honolulu.

Hilo International Airport measured 11.45 inches of rain last month, 75 percent of its November average of 15.5 inches. The rainfall total for the first 11 months of 2018, however stood at 165 inches, a whopping 43 percent higher than the norm of 115.15 inches.

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With less than a month left in the year, Hilo already had its sixth-wettest year on record, dating back to 1949, and by year’s end could well have its second- or third-wettest year, according to NWS hydrologist Kevin Kodama.

In his monthly precipitation summary, Kodama said that a wet weather pattern that began in late October continued through November’s first 10 days, producing “several episodes of heavy rain which resulted in flash flooding … across the state.”

“These wet conditions are not unusual given that the month of November, on average, has the highest frequency of flash flood events,” Kodama noted.

The weather dried out for most of the island for the remainder of the month, according to Kodama, who has predicted a drier-than-normal wet season.

Some spots in East Hawaii already have tallied more than 200 inches of rain in 2018.

Despite a November rainfall total of 12.18 inches — less than half its usual total — normally wet Glenwood had 235.88 inches of rain at month’s end, 10 percent above its yearly norm. Papaikou Well had 15.92 inches for the month, only 75 percent of average, but its year-to-date total stood at 229.25 inches, 23 percent higher than normal. And Waiakea Uka totaled just under 11 inches for November, barely half its average rainfall, but its total of 237.77 inches for the first 11 months was 31 percent above the norm.

Much of the rainfall can be attributed to Hurricane Lane in August, which dumped as much as 50 inches of rain in some East Hawaii locations, Tropical Storm Olivia in September, and other weather systems that brought heavy rain to the island’s already soaked windward side.

In November, the highest daily total was 8.03 inches at Laupahoehoe on Nov. 10. The North Hilo village had a wetter-than-average November with 18.35 inches, bringing its year-to-date rainfall to 161.65 inches, 22 percent higher than usual.

Saddle Road Quarry, which averages 127.9 inches of rain a year, received an eye-popping 350.62 inches this year, despite getting less than 10 inches of rain in September.

Some West Hawaii gauges saw above normal rainfall totals, mostly attributable to the flash flood events alluded to by Kodama.

On Nov. 3, a thunderstorm caused by a low-pressure system northeast of the Big Island “became anchored over the Kohala Mountains” and “created very unstable conditions that helped initiate thunderstorms and intense rainfall,” according to Kodama.

That was the day 13 stranded hikers from Kona’s University of the Nations were rescued by firefighters from Anna’s Pond in Waimea.

Kealakekua measured 4.81 inches of rain last month, almost 50 percent above its norm of 3.25 inches for November. Kodama said that “was mainly due to 3.71 inches recorded during the flash flood event of Nov. 6,” when “unstable conditions helped induce thunderstorms along the Kona slopes.”

The deluge aside, Kealakekua’s year-to-date total of 42.59 inches is only 80 percent of normal.

Waiaha, also in Kona’s coffee belt, received 4.25 inches, 58 percent above its normal November total.

Some Big Island areas already are seeing the prediction of a dry wet season come to fruition.

November was especially arid in the Ka‘u district, with all rain gauges totaling “below 50 percent of average,” Kodama said.

Kapapala Ranch received just 1.33 inches of rain, less than a fifth of its usual 7.18 inches.

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It was even drier in Pahala, where the rainfall tally of 0.83 inches was only a tenth of its 7.93 inches norm.

Email John Burnett at jburnett@hawaiitribune-herald.com.