Tropical cyclones fuel extreme heatwaves in their wake

Three days after hurricane Fiona struck Puerto Rico in mid-September 2022, the National Weather Service issued an extreme heat warning stating that the heat index – a measurement incorporating humidity to calculate perceived temperatures – could reach up to 109 degrees Fahrenheit. According to a new study led by the University of Arizona, such phenomena are not an exception. In fact, above-average temperatures almost always follow tropical cyclones (which include tropical storms and hurricanes) and may rise up to 10 degrees Fahrenheit higher than average.

While tropical cyclones frequently cause major damage from strong winds, storm surges, massive rainfall, and flooding, extreme heat is an additional hazard that can occur days after the cyclones, and even in nearby areas which were not directly impacted by the storms. “Multiple extreme events happening within a very short window of time can complicate disaster recovery,” said study author Zackry Guido, an assistant professor of Natural Resources and the Environment at the University of Arizona. “To medical providers, heat is a concern. Our results suggest that tropical cyclone preparedness should also include public information about heat risk.”

The scientists analyzed 53 tropical cyclones in the eastern Caribbean between 1991 and 2020 and 2005 interactions between these cyclones and 14 Caribbean cities, and found that the cities’ heat index values were always higher than average after the storm. “Everyone’s focus is on the destructive power of tropical storms and hurricanes – the storm surge, winds, flooding – and that’s obviously quite substantial, but our focus is on the combined hazard of storm and subsequent heat,” Professor Guido explained.

“Hurricanes are massive heat pumps, redistributing heat for a large spatial distance around the center of the storm, and they leave massive destruction in their wake that can knock out the energy grid. That combination is often dangerous because it slows recovery and poses risks to human health.”

Although this study does not explore how climate change may impact this phenomenon, the researchers expect that high heat index values following tropical cyclones will likely increase in the future. “It’s very easy to understand the climate change impacts of this. Our future will likely have hurricanes dropping more intense rain and have more people in harm’s way. Then, if you drape on top of that a hotter environment, you will therefore expect a greater overall impact,” Guido concluded.

The study is published in the journal Environmental Research Letters.

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By Andrei Ionescu, Earth.com Staff Writer