Climate change intensified the rainfall and winds of Hurricane Helene – Study

By the Climate Centre

Less than two weeks after Hurricane Helene swept away entire communities, more than 2,000 Red Crossers are working 24/7 to support families uprooted by the storm, while also preparing for Hurricane Milton’s landfall in Florida expected later today, the American Red Cross said.

Even with another potentially lethal hurricane just over the horizon, Red Cross teams are on station across the south-east United States, “committed to providing safe shelter, food, water, and recovery support to families facing unimaginable loss,” the National Society says.

The Red Cross is supporting over 100 evacuation shelters in Florida ahead of Hurricane Milton’s landfall.

The Central Florida and US Virgin Islands Red Cross chapter detailed in a post on X/Twitter Tuesday how it had pre-positioned relief supplies “across the state to make sure as soon as it is safe we can respond to help those in need”.

With the help of partners, the American Red Cross has provided nearly 34,000 overnight stays in more than 200 emergency shelters and at least 435,000 meals and snacks to affected people.

“We’re able to continually respond to large climate disasters like this because of the hundreds of trained disaster volunteers, response vehicles and prepositioned supplies in warehouses that stand ready to deploy to any disaster that comes our way,” the Red Cross adds.

Turbocharged by a warm sea

The climate science behind Hurricane Helene, meanwhile, was spelled out today in a rapid analysis by World Weather Attribution scientists from universities and meteorological agencies in the Netherlands, Sweden, the UK and the US.

Initially turbocharged by a warm Gulf of Mexico, some 2°C above average and a factor made very much more likely by climate change, the hurricane intensified rapidly to a Category 4 storm a few hours before landing on the west coast of Florida.

The team estimated its windspeed was 13 per cent higher due to climate change, and (emphasis added) the “huge amounts of rainfall inland” that caused unprecedented flooding in Georgia, the Carolinas, Tennessee and Virginia some 10 per cent more intense.

Hilly terrain funnelled the exceptional rainwater into rivers and streams, leading to very sudden flash floods up to rooftop level and making evacuation impossible in many areas.

Extraordinary video from The Nature’s Power in east Tennessee is one example of many that graphically reveal what US Secretary of Homeland Security Alejandro Mayorkas called the historic “strength, reach, and devastation of Hurricane Helene”.

Poor phone-signal and internet connectivity, “limited experience with hurricanes and more limited evacuation infrastructure have been reported in the media as leaving people feeling caught off-guard,” the WWA team note. 

“The US needs to plan for floods hitherto regarded as unimaginable – not just on the coast,” they add.

‘Once-in-a-lifetime events’

Julie Arrighi, Climate Centre Director of Programmes and one of the joint authors said today: “Our hearts go out to everyone affected by Hurricane Helene.

“It’s another warning that the effects of climate change are already here. We need to accelerate our preparedness for once-in-a-lifetime weather events and ensure our communities are adapted and able to withstand the unprecedented.”

Overall, the WWA conclusion is that while events like Helene might once have been expected once every 130 years, with climate change they will now be two and a half times more frequent.

Princeton University’s Professor Gabriel Vecchi said today: “Helene is a tragic reminder that it is not just coastal areas that are vulnerable to the impacts of tropical cyclones and hurricanes – wetter and stronger storms pose a growing threat far inland.

“As human-induced warming of the oceans continues to make tropical storms wetter and more likely to rapidly intensify, our infrastructure must meet this growing challenge – and adapt to our changing climate.”

Hurricane Milton seen from the International Space Station as it is intensified over the southern Gulf of Mexico yesterday. (Video grab: NASA)