Above-average rainfall recorded on Kaua‘i despite persistent drought conditions in December statewide

Despite persistent drought conditions within the Hawaiian Islands, all of the gauges on Kauaʻi ended up with near to above-average rainfall for 2023.

In December, windward gauges had near to above-average rainfall, while most of the leeward gages had below-average rainfall.

The U.S. Geological Survey’s rain gauge on Mount Waiʻaleʻale had the highest monthly total of 36.29 inches (121% of average) and the highest daily total of 10.30 inches on Dec. 20. The Poʻipū gauge had its highest December total since 2013.

The Mount Waiʻaleʻale gauge had the highest annual total of 384.06 inches (98% of average). The Kalāheo gauge had its wettest year on record with 75.77 inches (137% of average). Mōhihi Crossing, Puʻu Lua, Port Allen Airport and Waiakoali have relatively short periods of record but their 2023 totals were the highest in over 10 years.

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.

A cold front on Dec. 13 produced 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.