Hurricane Ian hit Florida last Wednesday as one of the strongest storms in state history — leaving dozens of people dead, with survivors facing months or years of rebuilding.
But the storm’s strength didn’t slowly build over time. Instead, Hurricane Ian quickly grew from a small tropical depression into a massive hurricane, in a process meteorologists call “rapid intensification.”
This kind of rapid storm growth has been getting more common over the past few decades, likely due to human-driven warming.
As the climate crisis gets worse over the coming decades, hurricanes could experience a lot more rapid intensification. Potentially, this will lead to immensely strong storms that build within days, posing a huge threat to life and coastal communities.
On Friday, 23 September, Ian formed as a tropical depression in the Caribbean, with wind speeds up to 35 miles per hour (56 kilometres per hour). By Sunday it had strengthened into Tropical Storm Ian. Then the real power surge came.
Between Sunday morning and Tuesday morning, the storm’s winds grew from 50 mph (80 kph) to 115 mph (185 kph) — 65 mph of growth in just 48 hours. Just between Monday and Tuesday morning, the storm grew 35 mph faster.
The National Hurricane Center defines “rapid intensification” as an increase in wind strength of at least 30 knots, or about 34 mph, in 24 hours.
After the hurricane whacked into Cuba, the storm hit that benchmark again, growing from a Category 3 hurricane with 115 mph winds on Tuesday morning to a near-Category 5 hurricane with 155 mph winds on Wednesday morning.
That strength comes in part from a warm ocean. Hurricanes are powered by ocean heat, which sends more water into their clouds and strengthens the wind power of the gigantic tropical cyclones as they make their way toward land.
When Ian hit the Caribbean, it encountered a lot of warm water, both south of Cuba and off the coast of Florida, which helped give the storm a ton of power very quickly. The Associated Press reports that the water in the Caribbean that Hurricane Ian passed over were about 1.8 degrees Celsius warmer than normal.
As the climate gets warmer, future hurricanes may encounter a lot more warm water, with a lot more potential energy to absorb on their way into land. Overall, the surface of the world’s oceans has warmed about 0.8C since the start of the 20th century, according to the Woods Hole Oceanographic Institute.
There are now 25 per cent more storms that exhibit rapid intensification than there were 40 years ago, AP reports. Additionally, one 2019 study found that tropical cyclones in the Atlantic Ocean have generally been intensifying more quickly since the early 1980s.
A hotter planet isn’t just making storms get stronger, faster. It’s also making these storms stronger — period. Over the past four decades, the percentage of tropical cyclones that reach Category 3 or higher has been increasing, according to the United Nations’ Intergovernmental Panel on Climate Change, a leading global authority on climate science.
As the planet heats up even further, these trends are only likely to grow.