Florida floods: How much rain has fallen and could it happen again?

Heavy rain has deluged elements of southern Florida, forcing the US National Weather Service to declare a flash flood emergency and triggering the overall shutdown of Fort Lauderdale airport. Road, rail and air connections have been minimize off and emergency providers have been working by means of the evening to rescue individuals stranded by rising waters.

Meteorologists say the rainfall is more likely to have smashed native data and to have been pushed partially by escalating local weather change.

Here’s what we find out about what has occurred and whether or not such occasions could be predicted.

How a lot rain has fallen in Florida?

Over 50 centimetres of rain fell on Fort Lauderdale in southern Florida within the house of simply 6 hours on 12 April, in response to the US National Weather Service, greater than one-third of town’s annual rainfall and equal to the annual rainfall of London.

The whole rainfall over the day could be even greater. A WeatherSTEM station at Fort Lauderdale airport confirmed that just about 66cm of rain fell on the station within the 24 hours as much as 7am native time on 13 April.

The intense downpours come after days of moist climate in Florida, which remains to be purported to be in its eight-month dry season the place common rainfall is about 7.6cm per 30 days.

Niklas Boers on the Potsdam Institute for Climate Impact Research in Germany stated the acute rain was a “very, very, highly unusual event to happen [for Florida], particularly in the dry season”.

Which areas have been affected by the rain in Florida?

The heavy rains rapidly overwhelmed metropolis drainage programs within the area, turning roads into rivers and flooding houses. Some 22,000 residents have been with out electrical energy at one level on 12 April.

The worst of the injury has been round Fort Lauderdale, the place transport networks have been successfully shut down. Fort Lauderdale airport has been closed for the reason that afternoon of 12 April and can stay so till a minimum of noon native time on 13 April. Meanwhile, South Florida’s high-speed commuter rail service Brightline can also be shut down.

Some 330 faculties throughout Broward County, which covers Fort Lauderdale and elements of Miami, have been closed on 13 April because of the “hazardous conditions”.

Further showers and thunderstorms are forecast for 13 April, with an extra 5 to 10cm of rain potential, in response to the US National Weather Service.

There could be very little metropolis officers can do to minimise disruption when big rainstorms like this deluge a metropolis, says Boers. “If you have very high amounts of water coming down in a very short space of time, then it’s very difficult for those water amounts to infiltrate the soil,” he says. “It’s the nightmare for climate impact adaptation planners, because there’s basically nothing you can do.”

How does a lot rain fall in such a concentrated space?

The rain was attributable to a set of slow-moving thunderstorms that gathered over Florida on 12 April. Such excessive rainstorms have gotten more and more widespread because the local weather adjustments. In 2021, an intense rainstorm stalled over Germany and Belgium for 2 days, inflicting catastrophic flooding. China, Italy and New York have additionally skilled comparable floods from excessive rainfall lately.

The improve in rainfall depth is because of climate-induced rising temperatures, says Hayley Fowler at Newcastle University within the UK. Warmer atmospheres maintain extra moisture, growing the frequency and depth of storms. “The capacity to have those bigger downpours is there, in terms of increased ability of the atmosphere to hold moisture,” she says.

There can also be some proof to recommend that local weather change is making storms extra more likely to “stall”, main them to deposit their rain in concentrated areas, elevating the chance of flash flooding.

Can we forecast these occasions?

The probability of maximum rainfall is without doubt one of the trickiest climate occasions for local weather scientists and meteorologists to forecast. One drawback is that local weather fashions appear to underestimate the potential elevated severity of rainfall because the local weather warms.

Researchers modelling local weather change’s affect on rainfall depend on the Clausius-Clapeyron equation, which calculates that each diploma of warming within the environment ought to lead to a 7 per cent improve within the depth of rainfall.

But latest excessive rainfall occasions appear to be releasing extra water than that, says Fowler, suggesting that one thing is amiss with local weather modelling on this space.

For instance, a examine in 2022 discovered that local weather change elevated rainfall through the strongest North Atlantic hurricane of 2020 by 11 per cent – virtually twice what can be anticipated from the Clausius-Clapeyron equation.

“The sort of downpours that we are seeing seem to show much bigger changes than that [the Clausius-Clapeyron equation], potentially,” says Fowler. “So there’s something else going on that we are not able to capture in our weather forecast models or our climate models.”

Fowler is amongst groups of scientists now finding out the right way to tweak local weather fashions so that they don’t underestimate the potential severity of future rainstorms. “I think we are missing something important,” she says.

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