Tropical Cyclone Heat Pumps Drive Extreme Heat Spikes

By Wesley Roberts •  Updated: 11/22/22 •  3 min read

According to a new study, above-average temperatures almost always follow tropical cyclones and can reach nearly 10 degrees Fahrenheit above average. The scientists say that their estimates of how quickly temperatures can rise after tropical cyclones, which by definition include tropical storms and hurricanes, are probably on the low side.

Hurricane Fiona hit Puerto Rico in the middle of September. Three days later, the National Weather Service issued a warning about extreme heat, saying that the heat index, which takes humidity into account to calculate how hot it feels, could reach 109 degrees.

“Multiple extreme events happening within a very short window of time can complicate disaster recovery. To medical providers, heat is a concern. Our results suggest that tropical cyclone preparednessshould also include public information about heat risk,”

said lead author Zackry Guido. Guido is an assistant research professor at the University of Arizona’s School of Natural Resources and Environment and the Arizona Institutes for Resilience: Solutions for Environment and Societies, or AIRES.

Heat Indexes And Tropical Cyclones

Between 1991 and 2020, the research team examined 53 tropical cyclones in the eastern Caribbean, as well as 205 interactions between the cyclones and 14 Caribbean cities. They discovered that the cities’ heat index values were always higher than average following 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,”

Guido said.

Hurricanes are like enormous heat pumps. They recirculate heat over a wide area around the center of the storm. They leave behind a trail of devastation that can bring down an electrical grid, and the combination is risky since it can slow recovery efforts, putting people’s health at risk.

In order to estimate how hot it would feel if the relative humidity in the shade were another value, the heat index (HI) combines air temperature and relative humidity in shaded areas. The comparable humidex is used in Canada in place of the heat index.

Greater Hurricane Impacts Ahead

While the paper does not investigate how climate change may be influencing the phenomenon, the authors believe that high heat index values following tropical cyclones will become more common in the future. It’s not hard to see the climate change impacts.

“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 said.

The cyclone research is part of a larger effort to improve Puerto Rico’s climate resilience. The researchers held workshops in the Caribbean with people who study public health and work in metrology. These people stressed how important it was to learn more about how heat affects people after tropical storms and hurricanes. The researchers want to raise awareness of this heat phenomenon as a new risk.

“We worked with the National Weather Service in Puerto Rico, and part of the work, not discussed in the paper, was to build awareness about heat impacts. Puerto Rico has a heat awareness week from May 11 through 15, and we are working to help advance public education and establish a heat awareness day,”

Guido explained.

Reference: Guido, Z., Allen, T., Mason, S., & Méndez-Lázaro, P. (2022). Hurricanes and anomalous heat in the Caribbean. Geophysical Research Letters, 49, e2022GL099740

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