A new study led by Newcastle University using satellite data shows that tropical cyclones and their post-tropical cyclone counterparts are responding quite differently to surface warming. The findings reveal that during the tropical cyclone phase, warmer and more humid conditions are causing storm slowdown and strongly increasing rainfall intensity.

Tropical cyclones are a major driver of very heavy rainfall in warm parts of the world. They can bring huge downpours that not only significantly add to total seasonal rainfall but also increase the risk of flash flooding. In the North Atlantic, these storms are especially important during the peak hurricane season (Aug-Oct), with tropical cyclones producing as much as 30–40% of all rainfall in some regions during that season.

Published in the journal npj Climate and Atmospheric Science, the study shows that storm precipitation is rising rapidly with temperature, with median increases of about 21% per degree increase in local dewpoint temperature, while the area of heavy rainfall expands by roughly 12.5% per degree of warming. At the same time, the overall size of the cyclone tends to shrink slightly with warming, although this process becomes weaker and can even reverse, causing larger tropical cyclones, when sea surface temperatures are very high, particularly in the Caribbean. In these warmer regions, tropical cyclones often move more slowly and last longer, producing more rainfall in one place, especially near to the centre of the storm, causing damaging floods.

In contrast, once storms transition into the post-tropical phase, losing their tropical characteristics as they move across the Atlantic towards Europe, they tend to expand in size but are less strongly affected by temperature changes. Rainfall concentrates to the northeast of the storm centre and over a wider area, often because the storm is moving faster and is driven by different (baroclinic) weather systems.

An increased risk of flooding in parts of the North Atlantic

Study lead author, Dr Haider Ali, Senior Research Associate, at Newcastle University’s School of Engineering said: “The findings show that global warming is increasing both the intensity and area of rainfall from tropical cyclones, especially in warm, low-latitude regions. Because some storms may also move more slowly, this could greatly increase the risk of flooding in parts of the North Atlantic. This trend will likely continue with increased warming.”

Previously, storm size was typically treated as a fixed radius around the storm centre. In contrast, this study adopts a dynamic definition, allowing storm size to vary along the cyclone’s lifetime. Using observational data from satellites, the team examined how storm size, heavy precipitation metrics, and translation speed change with warming for North Atlantic tropical cyclones from 2001 to 2024. This approach provides a consistent framework for analysing storm evolution and assessing how heavy precipitation responds to a warming climate.

Professor Hayley Fowler, Professor of Climate Change Impacts at Newcastle University, and one of the study authors, said: “Tropical cyclones appear to be causing increasing damages from widespread damaging floods from persistent extreme rainfall events, such as in Hurricane Helene. Our study shows that this increase in extreme rainfall is directly linked to our warming climate, caused by our continued societal reliance on fossil fuels. These storms will continue to get wetter, producing more persistent and more intense rainfall and consequent flooding, until we reduce the concentration of greenhouse gases in the atmosphere.”

Looking ahead, the next step is to shift the research focus from storms in the atmosphere to floods on the ground. The goal is to understand whether the most intense rainfall events lead to the most damaging river flooding. This causal link isn’t straightforward, since flood impacts depend on where rain falls, how long it lasts, and how wet catchments are prior to the rainfall event. By combining climate data with hydrological models, we can follow the full pathway from storm structure to rainfall to river flow. This helps identify not just heavy rain events, but the storms that truly translate into real flood risk for people and infrastructure.

Reference

Ali, H., Fowler, H. J., Reed, K. & Prein, A. F. (2026). Warmer temperatures lead to wetter tropical cyclones in the North Atlantic. npj Climate and Atmospheric Science. https://doi.org/10.1038/s41612-026-01363-2