Severe Flooding Threatens Hawaii as Hurricane Nolo Strengthens into a Major Storm

Ryanna Fry takes a picture of clouds in Kona, Hawaii, as Hurricane Nolo approaches on Friday. Heavy rain from Hurricane Nolo is ramping up in southern Hawaii, marking the islands’ third dangerous brush with a hurricane in just six weeks. Potentially life-threatening flooding and mudslides are again possible as the state contends with a Pacific tropical season supercharged by this year’s super El Niño.

Nolo rapidly intensified into a Category 2 hurricane Friday and remained at that strength on Saturday morning. Rapid intensification is an increase in maximum sustained wind speeds of at least 35 mph in 24 hours or less, a phenomenon occurring more frequently in a world warming due to fossil fuel pollution. The Big Island will bear the brunt of Nolo’s impacts as it continues to strengthen and makes its closest approach on Saturday local time. Extreme rain is its most serious threat, though Nolo is also whipping up strong wind gusts and dangerous seas.

Hurricane Lala took a similarly close track to the Big Island in mid-August as a Category 1 storm and unleashed catastrophic flooding there. On the other side of the state, Hurricane Lowell delivered a blow to Kauai and Niihau in early September as a Category 2 storm. Hawaii Gov. Josh Green has declared a state of emergency—the third storm-related emergency declaration this month—in anticipation of the severe weather impacts. Additionally, President Donald Trump approved the state’s request for a pre-landfall Presidential Emergency Declaration, Green confirmed Friday.

Flooding rain, mudslides possible

Nolo is expected to make its closest approach to the Big Island as a high-end Category 2 hurricane or a Category 3 major hurricane. Nolo’s rainbands continue to spin into the Big Island and will spread to Maui, Lanai, and Molokai on Saturday. Although rainfall totals have lowered with the most recent forecast, a dangerous amount remains possible. According to the National Hurricane Center, eight to 12 inches of rain are possible over eastern and southern portions of the Big Island through Sunday, with up to 16 inches in the steepest terrain.

Last month, the Big Island’s steep mountains helped wring more than 40 inches of rain out of Hurricane Lala’s bands, unleashing catastrophic flash flooding from which the island is still recovering. Nolo’s rainfall is expected to be lower, but still significant on the western side of the island, with up to 6 inches possible. In eastern Maui, 4 to 6 inches are possible with isolated amounts up to 8 inches, while about 1 to 3 inches of rain are expected elsewhere on the main islands.

Nolo’s strongest winds will remain offshore since the hurricane is passing well to the south of the Big Island. Still, tropical storm-force winds stronger than 40 mph are likely in areas of steep terrain on Saturday, and hurricane-force gusts exceeding 75 mph cannot be ruled out.

Hawaii battens down — again

State and county offices, public schools, and the University of Hawaii were closed Thursday and Friday on the Big Island and scheduled to close Friday on Maui, Gov. Green announced in a social media post. Approximately 400 National Guard troops are positioned across the state, with 121 on the Big Island. County officials have opened shelters on the Big Island.

“If your home flooded before, or is at risk, consider moving to safer shelter before the full force of the storm hits,” Hawaii County Mayor Kimo Alameda stated in a Wednesday news release. “Because the ground remains saturated, flooding may happen rapidly.”

The state has also secured 100 hotel rooms for Big Island residents wishing to evacuate, Green said at a Wednesday news conference. Statewide, hundreds of people are still being housed in hotels after being displaced by earlier natural disasters, including hurricanes Lala and Lowell, Department of Human Services director Joseph Campos noted at the same conference.

On Maui, officials have prepared emergency generators and storm response equipment while increasing staffing at police and fire departments. Bus service will be suspended intermittently throughout the weekend. Offshore, dangerous seas will build and peak Friday and Saturday, with rough conditions likely persisting through the weekend and into next week as the hurricane tracks west away from the island Sunday night into Monday.

Super El Niño’s dominance

This year’s super El Niño has helped prime the Pacific to generate strong tropical systems, fueled by extremely warm ocean water and a lack of storm-killing wind shear. Nolo is one of 19 named storms—including three Category 5 hurricanes—to roam the eastern and central Pacific with two full months of the season remaining. Seventeen originated in the eastern Pacific basin, which typically sees up to 15 storms in an entire season.

For the second time this month, a trio of hurricanes—Nolo, Odalys, and Polo—are simultaneously churning in the Pacific. Polo, currently roaring off the coast of southern Mexico, is one of five storms this season to meet the criteria for extreme rapid intensification, defined as a wind increase of 58 mph or more in 24 hours.