Drought conditions persist after a dry December on the Big Island

Drought conditions in Hawai‘i persist as Big Island rainfall totals were near to below average for December.

The Kaʻū District and the Humuʻula Saddle region were dry with most of the totals at less than 20% of average. The U.S. Geological Survey’s rain gauge at Kawainui Stream had the highest monthly total of 20 inches (149% of average).

The highest daily total of 8.93 inches was logged on Dec. 1 at a manually read Community Collaborative Rain, Hail and Snow volunteer network gauge a few miles southeast of Pāhoa. According to the National Weather Service, most of this daily total may have occurred on Nov. 30.

Among the automated sites, Honokaʻa had the highest daily total of 4.28 inches on Dec. 14. The Pali 2 gage in the Kaʻū District had its lowest December total in a data record going back to 2003.

The Kealakomo and PTA Kīpuka ʻAlalā sites had their lowest December totals since 2009 and 2012, respectively.

Overall, rainfall totals for 2023 were near to below average at most of the gauges on the Big Island. The U.S. Geological Survey’s rain gauge at Honoliʻi Stream had the highest annual total of 186.87 inches (81% of average).

To see more rainfall totals for the month, click here.

Trade winds did return to the main Hawaiian Islands after a Kona Low system developed hundreds of miles northwest of Kauaʻi, producing rainy conditions in late November but quickly dissipated on Dec. 2.

The trade wind intensities were mainly light to moderate, though there was a brief episode of fresh to locally strong trades on Dec. 6.

Rain that did fall in December came during a cold front on Dec. 13 producing several hours of rainfall that eventually caused Hanalei River to overflow its banks. The flooding resulted in the closure of Kūhiō Highway for several hours.

Cool northeasterly winds at moderate to fresh speeds persisted over the island chain through Dec. 18 and produced daily rainfall along the windward slopes.

The trade winds reached fresh to strong levels from Dec. 19 through 24. The increased forcing of moist air up the slopes, combined with a low-pressure trough aloft, resulted in enhanced rainfall along the windward slopes of the state on Dec. 20.

But this rainfall was concentrated over Kauaʻi and Oʻahu, with large areas of 2 to 6 inches over the slopes, and peak 24-hour totals over 10 inches. Kūhiō Highway in north Kauaʻi closed for the second time in just over a week due to the Hanalei River overflowing its banks.

Persistent heavy rainfall along the windward slopes of Oʻahu’s Koʻolau Range resulted in flash flooding that closed Kamehameha Highway at Waikāne Stream.

A drier pattern settled in on Christmas Day and remained in place for the rest of the month. A weak cold front reached the main Hawaiian Islands on Dec. 28 but did not produce significant rainfall or flooding problems.