Most Big Island Rain Gauges Record Below Average Totals for March

The near constant rainy conditions in Hilo and parts of East Hawai’i as of late are not a reflection of how the Big Island faired as far as precipitation levels went in March.

According to the monthly rainfall summary prepared by Kevin R. Kodama, senior service hydrologist for the National Oceanic and Atmospheric Administration and National Weather Service Weather Forecast Office in Honolulu, most rain gauges around the island posted below average rainfall totals last month.

“Many of these were in the range of 30%-70% of average,” Kodama said in his report. “The main outliers came from the slopes of the South Kona district, where several gauges recorded above average totals.”

The highest rainfall total for March, 16.67 inches, was recorded by the U.S. Geological Survey rain gauge at Honoliʻi Stream, north of Hilo.

The highest daily total recorded by automated gauges was 2.52 inches on March 23 by the USGS gauge at Kawainui Stream in North Hawaiʻi. The highest overall daily total was just a bit more, 2.60 inches, recorded March 31 by a manual gauge in the Wainaku area of Hilo provided by the Community Collaborative Rain, Hail and Snow Network, or CoCoRaHS.

“Big Island rainfall totals for 2022 through the end of March were below average at most of the gauges,” Kodama’s report said. “The rain gauge at Honoliʻi Stream had the highest year-to-date total of 22.95 inches among the automated sites. However, the Wainaku CoCoRaHS gauge had the highest year-to-date total among all sites, with a manually read 28.23 inches.”

For more specific rain gauge data from March, click here.

Kodama explained in his monthly summary that the central North Pacific weather pattern that has produced generally dry conditions over the main Hawaiian Islands since early January continued into the first half of last month. A weak large-scale surface pressure pattern resulted in light winds, mainly from the east to east-southeast.

“A couple of weak cold fronts, one on March 2 and another on March 7, got close to the state but never reached any of the islands,” the summary said. “Light wind patterns like these allow land and sea breezes to dominate the local conditions. Stable conditions aloft also prevented significant rainfall on most of the days.”

Exceptions occurred March 8-9, when a shower area within the easterly low level flow moved over windward slopes of the state. An upper tropospheric trough over the area provided some instability to enhance the showers, resulting in 1-2 inches of rainfall along the slopes of the Big Island’s Hāmākua district.

The large-scale weather pattern over the North Pacific finally shifted during the second half of March, resulting in an increase in rainfall over the state.

“This period featured stronger trade winds than earlier in the month, and a resultant increase in windward showers,” the summary said.

A low pressure system aloft over the state provided enough instability to support thunderstorm activity March 30-31 over portions of the Big Island and Maui, with the most intense rainfall over the West Maui Mountains on March 30, where radar and rain gauges observed totals of 5-8 inches in a five-hour period.
Unfortunately, dry weather in the first part of March only made drought conditions worsen for portions of the state.

“The prolonged dryness from early January through mid-March has intensified drought over portions of Maui County and the Big Island,” Kodama’s report said.

For more details about drought conditions, refer to the Drought Information Statement online.

Click here to read the full rainfall summary for March.