Researchers found that hurricanes developing over localised regions of higher sea surface temperatures were more likely to grow quickly and cover larger areas. These so-called ocean "hot spots" appear to fuel storms differently than broader global warming trends.

"A larger storm has a wider swath of destructive winds, higher storm surge and heavier rainfall over a broader area—all of which increase risks to society," said Danyang Wang, postdoctoral researcher at Purdue University and lead author of the study.

Why size matters in hurricanes

The intensity of hurricanes is usually defined by the Saffir-Simpson scale, which ranks them from Category 1 to 5 based on wind speed. But storms of similar intensity can vary dramatically in size, making some far more destructive than others.

Analysing decades of observational data, the researchers found that ocean hot spots were strongly correlated with rapid storm expansion. This helps explain cases such as Hurricane Helene, which ballooned in size before striking land last year and became the third-deadliest US hurricane of the modern era.

Interestingly, the study suggests that while global warming makes hurricanes more intense overall, it has less effect on their growth rates than localised ocean heat anomalies.

Forecasting the future

The findings come as the Atlantic hurricane season intensifies, with Hurricane Gabrielle currently strengthening near Bermuda. Scientists say that factoring in ocean hot spots could make short-term forecasts more accurate and improve long-term risk models used by governments and insurers.

"This discovery can be applied both in daily forecasting and in long-term modelling of hurricane impacts," Wang said. "Recognising the role of sea surface warming is essential to better prepare communities for the risks these storms bring."