National Weather Service: October looked like mid-winter, not early fall

Overall, the weather pattern over the main Hawaiian Islands during the month of October looked more like something from mid-winter as opposed to what would be expected in early fall, according to the National Weather Service’s October precipitation summary.

Strong low pressure systems in the North Pacific pushed the low level high pressure ridge southward to just north or even directly over the state. This resulted in most of the days in the month having a stable air mass and light winds, with land and sea breezes dominating the local wind conditions.

There were three weak cold fronts that reached at least a portion of the main Hawaiian Islands. The first moved over Kauaʻi on Oct. 4, then dissipated over the Kauaʻi Channel on October 5. This was the first cold front passage for the 2023 – 2024 Hawaiian Islands wet season, and was earlier than normal by a couple of weeks.

The second front reached Kauaʻi on Oct. 19. Like its predecessor, this front also dissipated over the Kauaʻi Channel.

The third front was the most active, passing over Kauaʻi on Oct. 23, then dissipating over Molokaʻi after moving across Oʻahu on Oct. 24. This frontal system produced several well-defined pre-frontal rain bands that affected Kauaʻi on Oct. 22 and 23, with 48-hour rainfall totals of 3 to 6 inches over the southwestern half of the island. Several streams and rivers on the island had elevated flow levels, but there were no reports of significant flood impacts from this event.

Most of the gages across Kauaʻi posted near to below average rainfall totals for the month of October. Gages on the west side of the island had above average monthly totals as a result of the passage of pre-frontal rain bands on Oct. 23. The U.S. Geological Survey’s gage on Mount Waiʻaleʻale had the highest monthly total of 16.96 inches (50% of average). The U.S. Geological Survey’s gage at Mohihi Crossing had the highest daily total of 3.32 inches on Oct. 23. The gages at Hanalei and Wainiha had their lowest October totals since 2012.

All of the rain gages on Kauaʻi had near to above average rainfall totals for 2023 through the end of October. The Mount Waiʻaleʻale gage had the highest year-to-date total of 301.12 inches (92% of average).