Dry conditions persist in July for Ka‘ū, Hāmākua Districts, according to monthly rain summary report

Last month was one of the driest Julys for East Hawai‘i in 15 years.

Most windward and interior sites on Hawai‘i Island were below average for June, the worst of which were in the Kaʻū and Hāmākua Districts, as well as leeward lower elevations of the Kohala District. This continued into July where areas failed to exceed 25% of their July averages, according to the monthly rain summary report by the National Weather Service.

Waiākea Exp. Station and Hilo Airport had their driest July since 2010. It was Hakalau’s driest July since 2011, according to the report.

Last month recorded the second driest July for Kealakomo and Saddle Quarry since 2010. In Kamuela, it was second driest July since 1991.

Despite the dry conditions, the Hilo and North Kohala Districts were able to tally up to 1.25 inches on July 7 in a few spots.

The Waiʻaha, and Kawainui Stream gauges did manage to come in above average. The highest monthly total again came from the USGS gauge at Kawainui Stream with 15.72 inches, according to the report. This site also recorded the highest daily total for the month of 1.37 inches on July 7.

July began with a typical summer trade wind pattern dominated by high pressure to the north and stable conditions aloft, the monthly report indicated. Moderate to locally breezy trades brought generally dry weather through July 4, with only modest windward and mauka showers.

A surface trough passed through the state from July 14 to 15, temporarily lifting the inversion and allowing for some enhanced shower activity, mainly over windward higher terrain and portions of the North Kohala coast and windward slopes between Pololū Valley and Waipiʻo Valley on the Big Island.

A mid-level ridge returned through July 18, stabilizing the atmosphere and generally reducing rainfall. However, a moisture surge on the 17th brought increased windward and upslope showers, especially for Maui and the Big Island, where the Kona slopes between Kailua-Kona and Kealakekua received 0.75 to 1.5 inches of rain, according to the report.

The most notable rain event occurred on the 19th and 20th due to a combination of above-average moisture and instability from a weak mid-level low northwest of Kauaʻi, where there was significant flooding, including road closures and elevated river levels, easily verifying the Flash Flood Warning issued the morning of the 20th. Mount Waiʻaleʻale recorded nearly 8 inches of rain in 24 hours.