State, Big Island February Rainfall Summary
Shifts in the North Pacific weather pattern produced unsettled conditions across the main Hawaiian Islands during the first half of February.
The initial bout of inclement weather arrived on Feb. 5 in the form of a cold front. Moist post-frontal northerlies produced heavy rainfall along the north-facing slopes of Kaua‘i on Feb. 6. This caused Hanalei River to overflow its banks and inundate Kuhio Highway near the Hanalei Bridge for several hours. Rainfall associated with the cold front’s cloud band also produced minor flooding over portions of Oahu, Molokai, and Maui as it moved eastward slowly across the state.
While cool low-level winds swept across the state, a reinforcing disturbance dropped in from the northwest and strengthened the area of low-pressure northeast of the state. Strong northwest winds developed over the island chain on Feb. 10 with embedded heavy rainfall areas moving toward the southeast. The rapid movement of these areas helped limit rainfall accumulations and resulted in only minor flooding problems.
The close proximity of the low-pressure system’s cold core to the state lowered the snow level to just over 8,000 feet and produced wintry conditions over the upper slopes of Haleakala on Maui, and Mauna Kea and Mauna Loa on the Big Island. An interesting side note to this event is that a similar low-pressure system developed a year ago to the day in the same general area and produced similar types of impacts.
After the anomalous low-pressure system dissipated on Feb. 12 and 13, the rest of the month was dominated by periods of strong trade winds across the island chain. While these trade winds contained embedded shower areas, the resultant rainfall along the windward slopes occurred in generally small amounts with no significant flooding.
February totals from rain gauges in the North and South Kohala Districts, the North and South Kona Districts and the Hāmakua District were mostly near to above average. Most of the February totals across the rest of the Big Island were near to below average.
The USGS’ rain gauge at Kawainui Stream had the highest monthly total of 13.94 inches — 146% of average. The Kamuela Upper gauge, which recorded 4.76 inches on Feb. 10, had the Big Island’s highest daily total for the month. This is a rare distinction for this site. Its monthly total of 8.89 inches — 182% of average — was also its highest February total since 2002.
Most of the Big Island’s rain gauges had above average rainfall totals for 2020 through the end of February. The USGS’ Saddle Road Quarry gage had the highest year-to-date total of 65.62 inches — 315% of average.