Hawaiian weather often brings to mind visions of abundant sunshine, but Kona Low storm systems frequently bring tremendous amounts of precipitation to the islands.
HONOLULU – Hawaii’s famed sunshine is taking its own vacation break this week as a dayslong stormy pattern sets up just off the tropical islands, threatening heavy rain and rounds of flash flooding for the end of the week.
“The (forecast) model guidance for this week looks anything typical of mid-May for Hawaii, to say the least,” forecasters with the National Weather Service in Honolulu wrote in their Tuesday morning forecast discussion.
A Kona Low is expected to develop a few hundred miles north of the islands Tuesday evening and is forecast to strengthen and meander just offshore for several days.
Hawaii rainfall forecast
“Kona” comes from the Hawaiian word for “leeward” – the side sheltered from the typical northeasterly trade winds. Kona Lows are problematic as the winds reverse from the typical trade winds, bringing heavy rain to what are normally the wind- and rain-shadowed leeward areas of the islands.
Meanwhile, a large area of deep, tropical moisture sits just southwest of the islands, providing the Kona Low with ample nearby fuel to enhance rainfall.
The combination will bring the potential for prolonged periods of heavy rain and thunderstorms through at least the end of the week.
Flood Watches are in effect for all of Hawaii from May 15-17, 2024.
Flood Watches are in effect for the entire Hawaiian Islands from Wednesday morning through Friday evening.
The NWS warned that significant flooding may occur from the overflow of streams and drainages, and roads in several areas may be closed. Runoff may also cause property damage in urban areas.
“Landslides may also occur in areas with steep terrain,” the NWS said.
It’s already been a very wet week for Hawaii. Flood Watches and Warnings were posted across the islands over the weekend as a slow-moving storm system scraped the islands, with even winter storm conditions atop the Big Island’s mountain peaks.
Even Monday ahead of the Kona Low, Flash Flood Warnings were in effect for eastern Oahu as a strong thunderstorm brought rainfall rates of 2 inches per hour, causing some localized flooding.
Several rain gauges in the higher elevations of Oahu have reported over 8 inches in the past 72 hours, with a gauge at St. Stephens Seminary near Kailua receiving over 18 inches of rain in three days. A gauge in Kaneohe had over 9 inches in 72 hours, while the Marine Corps base at Kaneohe reported 5.01 inches for the same period.
While Wednesday’s flood alerts currently expire on Friday evening, the NWS warned the wet pattern could hold through the weekend.