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The climatic setup for the 2024 hurricane season in the North Atlantic indicates a highly active season ahead. According to current forecasts, the number of tropical cyclones could be significantly higher than the long-term average. It is difficult to predict how many will make landfall – or where. But a greater number of storms means a higher probability of multiple landfalls. In addition, there could be a higher risk of storms in the Gulf of Mexico and Caribbean Sea this year, which in turn means a higher risk of storms making landfall in these regions.
In figures
Based on the climatological conditions, Munich Re expects an above average hurricane activity in 2024. In terms of expected numbers in tropical cyclones, leading research institutes1 anticipate approximately 23 named cyclones in the tropical North Atlantic for the 2024 season. Roughly eleven of these could develop into hurricanes, of which five might become severe hurricanes with wind speeds of over 110 mph (177 km/h).
These estimates are significantly higher than the long-term average between 1950 and 2023 (12.0 named storms, of which 6.4 were hurricanes, with 2.8 severe hurricanes). The forecasts are also well in excess of storm activity in the cyclical warm phase in the North Atlantic since the mid-1990s (15.7 tropical storms, of which 7.5 were hurricanes, with 3.3 severe hurricanes).
The hurricane season officially begins on 1 June and continues until the end of November, since outside this period the probability of tropical cyclone developments is generally much lower.
Background
Sea surface temperatures in the tropical North Atlantic are currently at record high levels, between 0.5 and 1.0°C higher than the long-term average, and are expected to remain high throughout the peak of the hurricane season. Meanwhile, the natural climate oscillation ENSO (El Niño/Southern Oscillation) in the Pacific will very likely switch to the so-called La Niña phase, whose long-distance effects also favour the development of severe hurricanes in the North Atlantic.
Atlantic hurricane activity in 2024 will be heavily influenced by these two factors: It is well known that warmer oceanic temperatures in the tropical North Atlantic, such as those currently prevailing, provide more fuel for the potential development and intensification of tropical cyclones. The ENSO cycle in 2023 was characterised by strong El Niño conditions – the opposite of the La Niña phase that is expected to develop this year. El Niño years are typically accompanied by strong winds at high altitude over the North Atlantic. This is known as vertical wind shear, which inhibits tropical cyclone development because it literally tears storm systems apart. Under La Niña conditions, high altitude wind shear is reduced, making it easier for tropical cyclones to develop.
A further possible effect of La Niña influences the tracks of the storms. There is typically a large high-pressure area between the Azores and Bermuda. Its intensity influences how far west individual storms will track before drifting away north. During a La Niña phase, this high-pressure area is often more pronounced, so storms can move further to the west, thereby potentially increasing the risk to the Caribbean and the Gulf of Mexico.
Hurricanes and climate change
Researchers believe that climate change is contributing to a higher proportion of especially severe hurricanes and storms with extreme rainfall, but not necessarily to a higher number of storms overall. However, most climatologists believe that climate change is playing a significant role in the exceptionally high water temperatures in the North Atlantic.
Anja Rädler, meteorologist and climate expert at Munich Re, says: “Forecasts of storm activity in the hurricane season should always be treated with caution. However, this year we have two important factors that will probably favour cyclones – the development of a La Niña phase in conjunction with very high water temperatures in the tropical North Atlantic, the formation area for the hurricanes. For that reason, the forecasts seem to be more reliable this time.”
Devastation and storm surges: Hurricanes cause billions of dollars in losses
If severe hurricanes make landfall on the US coast, they frequently leave behind many billions of dollars in losses. Further inland, the storm surges and floods that typically accompany hurricanes heavily influence the scale of damage. Hurricanes affect not just the southern and southeastern states of the USA, but also the northeast coast of North America including Canada. Accordingly, in order to minimise losses and protect human life, prevention in the form of robust buildings and optimal early-warning systems is particularly important.
The forecasts for the hurricane season send a clear signal: loss prevention is crucial. Needless to say, it is impossible to predict months in advance where and when a hurricane will make landfall. But investing in more stable structures always makes sense, since it prevents losses and can save human lives. That is why Munich Re has for many years been supporting the Insurance Institute for Business & Home Safety (IBHS) in the USA. This organisation tests the stability of full-size houses in a wind tunnel and makes recommendations on more robust construction methods.
In 2023, 20 tropical cyclones were recorded in the North Atlantic, of which seven were hurricanes, three of which in turn developed into severe hurricanes in the highest 3–5 category. The losses caused by the storms remained relatively low despite the landfall of Hurricane Idalia, a major hurricane that fortunately came ashore along a sparsely populated stretch of the coast. Most other storms in 2023 developed in the open Atlantic, veering north and east without making landfall.
On the other hand, Hurricane Otis devastated the holiday resort of Acapulco on the Pacific coast of Mexico in October 2023 with wind speeds of 265 km/h. Otis was the most severe cyclone ever to hit the Pacific coast of Mexico, a landfall of unprecedented severity along the Mexican coast that will likely bring significant changes to building construction along a coastline that builds primarily to reduce seismic risk.
In the western part of the Northern Pacific, ENSO conditions also influence the typhoon season in the region, but with roughly the opposite effect to that on cyclones in the North Atlantic: La Niña is often associated with typhoon activity that is below the long-term average. In the period 1980 to 2023, this region experienced an average of 25.3 named storms, 15.9 typhoons and 8.8 major typhoons in category 3–5 each year.
1 Colorado State University, Tropical Storm Risk, University of Arizona
