2 Former Tropical Cyclones Bring Moisture to Kauaʻi

The leeward side of the Garden Island was hit with above-average rainfall in the month of August with hikers reporting a rapid rise of water levels in the Kapaʻa Stream.

The state experienced remnant moisture from two tropical cyclones last month, according to the National Weather Service monthly rain summary report. As a result, Kauaʻi’s windward gages had mostly below-average rainfall totals, and leeward gages had mostly above-average totals.

The report indicated the above-average leeward totals were mainly due to afternoon showers during the two periods of the month where the trade winds were disrupted by remnants of rain from former tropical cyclones Jimena and Linda.

Rain from former Tropical Cyclone Jimena embedded within the trades moved across the state on Aug. 10-11. During that time, Kauaʻi was hit with brief bursts of heavy rainfall over the eastside.

According to the report, the most significant rain event of the month occurred from Aug. 22 through the morning of Aug. 24 during the passage of the remnants of former Tropical Cyclone Linda. The initial rain bands affected the northeast-facing slopes of the Big Island and Maui County on August 22, then spread westward to Oʻahu and Kauaʻi on Aug. 23.

Peak rainfall totals of 3 to 7 inches were recorded along the windward slopes of the main Hawaiian Islands. There were no reports of significant flood-related damage from this event.

All of the gages on Kauaʻi continued to have near to above-average rainfall for 2021 through the end of August. Mount Waialeale had the state’s highest year-to-date total of 342.62 inches (131% of average).

The US Geological Survey’s (USGS) rain gage on top of Mount Waialeale also had the highest monthly total of 24.95 inches (72% of average) and the highest daily total of 4.22 inches on Aug. 23.

August closed out with another weak surface trough passing westward to the north of the state, which once again disrupted the trade winds. Afternoon showers were able to develop over some of the leeward and interior sections of the state, but the rainfall amounts were less than an inch.

Monthly totals in these areas were less than 2 inches, but because the August averages were mostly less than an inch, even relatively modest amounts of rainfall can push the totals into above-average territory.