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Will climate change make tropical storms in Southern California more common?

Tropical Storm Hilary brought plenty of rain and wind across Southern California. With a changing climate, many wonder if we'll see more frequent storms like this.

SAN DIEGO — On the heels of Tropical Storm Hilary arriving, many Southern Californians are left wondering whether climate change could make hurricanes and tropical storms more common in the area.

The rain that Hilary brought was enough to break records for the most amount of rain recorded in the month of August in a few local cities. It was more rain than the city of San Diego had seen in a single day in more than 6 years. Palm Springs saw nearly their total annual rainfall in just 48 hours. So could climate change and global warming increase the likelihood of these storms making landfall?

Research scientists and the National Oceanic and Atmospheric Administration agree: No, climate change is not likely to increase the frequency of tropical cyclones making landfall in San Diego or anywhere in the world for that matter. But, it could increase the intensity of cyclones that develop, leading to more destruction when they do arrive. 

In other words, the number of storms making landfall isn’t expected to increase – in fact, some models show the number of cyclones actually dropping slightly. But the intensity of rain and wind within the lifetime of a cyclone could rise by about 5 percent in the 21st century. Beyond that, rising sea levels increase the likelihood of life-threatening storm surge, especially across coastal communities in the United States. 

A couple other factors that could lead to more intensity and severity are the speed the storms move at and increased urbanization.

There is also some evidence to suggest that cyclone movement is slowing down. This can particularly increase devastation when storms essentially stall over cities, drenching them in one place and inducing flash flooding, rather than the fast speeds that other storms move through with. But, there’s still more research that needs to be done on weather this change is caused by humans. 

One factor that is definitely caused by humans.. Urbanization. Cities are growing in size, especially along coastal communities. That means more pavement that isn’t able to soak in rain, making urban areas more susceptible to flash flooding. Beyond that, researchers have also shown urban heat islands around downtown areas tend to increase thunderstorm intensity, meaning not only could future storms bring more rain, but that rain could be left with nowhere to go. 

Here in San Diego, that means the frequency of tropical storms or hurricanes arriving wouldn’t necessarily increase. But when they do, whether that's every century or more, they could become increasingly devastating for our communities. 

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