The National Weather Service said Monday “a band of deep moisture” is bringing with it the potential for thundershowers islandwide at least through tonight and possibly through Wednesday night in East Hawaii.
A flash flood watch remains in effect until 6 p.m. tonight for Hawaii Island and Maui.
“The moisture is being pulled from the south, and the band is moving from the east to the west, along with the low-pressure system,” said Vanessa Almanza, a National Weather Service meteorologist, on Monday afternoon. “We’re anticipating heavy rainfall and thunderstorms. And because this band is potentially going to stall out over Hawaii (Island) and Maui, the rainfall could be pretty sustained and flash flooding could ensue.”
The band is expected to move eastward tonight and Wednesday, though the flash flood watch might need to be extended if heavy rains linger, forecasters said. A flash flood watch could also potentially lead to a flash flood warning if flooding is imminent or occurring.
What started as a sunny Presidents Day in Hilo on Monday became increasingly cloudier and darker during the afternoon. According to the hourly rainfall totals for 3:30 p.m., Hakalau, north of Hilo, received 0.15 inches of rain in an hour.
It also was raining in usually arid West Hawaii. Kealakekua in the South Kona coffee belt received 0.12 inches, according to the 4:30 p.m. hourly rainfall totals Monday, while Kahuku Ranch in Ka‘u tallied 0.32 inches.
Colin John, a Kona-based musician, said Monday afternoon he and his partner, singer “Long Tall Deb” Landolt, were in Puako, where rainfall averages less than 2 inches a year, “and it was raining.”
“It never rains down there, in the Kawaihae, Puako area. And it was raining,” John said. “When we were coming back, we said let’s take the upper road (Highway 190) because there are probably going to be a lot of disappointed tourists driving from the Kohala Coast back into Kona. So we drove up, and it appeared to be clearer in Waimea than it did in Puako and Kawaihae. It was raining really hard down there.”
According to the National Weather Service, the chance of rain today in Hilo and Kona is 90 percent, with an 80 percent chance tonight in both locations. Chances of rainfall Wednesday are 80 percent in Hilo, 70 percent in Kona, the weather service predicted.
Hilo Bayfront Highway remained closed Monday.
County Civil Defense Administrator Talmadge Magno advised residents to monitor weather forecasts and be prepared to take action if a flash flood warning is issued.
In addition, a winter storm warning is in effect for the summits of Maunakea and Mauna Loa until 6 a.m. Wednesday.
“There’s an upper level trough that’s bringing cold air down to the higher altitudes,” Almanza said.
Heavy snow is expected, and the accumulation could be between 5 and 10 inches.
According to forecasters, the winter storm warning also is a product of the moisture band.
The Maunakea Access Road was closed at the Visitor Information Station “due to thick fog causing poor visibility of less than 50 feet making for unsafe driving conditions,” according to the Maunakea Observatories Support Services phone message recorded at 1:45 p.m. Monday.
Email John Burnett at firstname.lastname@example.org.