The official hurricane season in the Atlantic began on June 1st, and the scientists expect increased activity in 2024. Discover why nearly all hurricanes form between June and November and why this year’s risk is classified as particularly high.

Tropical cyclones in the Atlantic and northeast Pacific are known as hurricanes. These storms are characterised by a closed circulation around a pronounced low-pressure system. Hurricanes can span several hundred kilometres and often feature a cloud-free eye at their centre. According to the Saffir-Simpson scale, hurricanes are classified into five categories based on wind speed. Hurricane Beryl, which reached the eastern Caribbean on 2 July 2024 and made landfall over the Gulf coast of Texas on 8 July 2024, is noted as the first category 5 hurricane of this year, setting the record for the earliest category 5 hurricane since records began.

How does a hurricane develop?

Hurricanes are extremely complex systems that require certain conditions to develop. Hurricanes, typhoons, and tropical cyclones form over warm ocean waters as they need a continuous supply of heat and moisture. The following conditions are essential for their development:

1. The uppermost ocean layer (approx. 50 metres) must have a temperature of at least 26.5°C (determined by statistical analysis) at the place of formation
2. The middle troposphere must be as moist as possible, so the mixing of the ambient air (entrainment) has as little influence on the hurricane as possible. If the air is too dry, this can reduce the buoyancy and contribute to the weakening of the system.
3. The Coriolis force, which is stronger with increasing distance from the equator, is necessary for the storm’s rotation. Thus, the potential development area is typically at least 5° north or south of the equator.
4. Vertical wind shear is minimal. If winds blow at different heights with varying strengths (wind shear) or in different directions (turning wind shear), it can significantly weaken the storm.
5. Existing disturbance zones in the atmosphere are favourable. Such disturbance zones (e.g. tropical easterly waves) often serve as the starting point for the formation of tropical cyclones.

If all these conditions are met, there is a good chance that an initial tropical disturbance will develop into a tropical depression. If this intensifies further, a tropical storm develops. If the tropical storm reaches wind speeds of over 33m/s (119km/h), the storm is categorised as a tropical cyclone (= hurricane).

When does a hurricane end?

The video shows our wind animation with a view of the tropical cyclone Biparjoy in the Indian Ocean. Clearly recognisable: Immediately after the cyclone made landfall, it weakened and reverted to a depression. The same applies to hurricanes in the Atlantic. When they make landfall, their destructive force causes significant damage. However, various factors ensure that the hurricane weakens. Firstly, the primary energy source—the warm ocean—is missing over land. Secondly, dominant friction effects due to topography disrupt the vertical air currents, increasing wind shear, which negatively impacts the hurricane. Additionally, dry air layers over land can infiltrate the storm, reducing humidity and contributing to the storm’s weakening. A hurricane can also weaken over the ocean if it crosses areas with lower sea surface temperatures.

What is expected for this year’s hurricane season?

Based on historical data, meteorologists know that a particularly large number of tropical storms form in the Atlantic from July 1st to the end of November. This period is known as the "hurricane season” due to optimal atmospheric conditions, high ocean temperatures, and strong solar radiation favouring the rise of air masses (convection).
Experts expect an above-average number of hurricanes this year. One reason is the high temperatures in the Atlantic since January 2024. Another reason is the transition from El Niño to La Niña conditions in the Pacific. La Niña conditions affect the trade winds in the Atlantic, reducing wind shear and favouring tropical storm development.

What meteoblue offers to detect and follow tropical storms

With the help of our weather maps, you can stay informed at all times. Even before a hurricane occurs, the tropical depression can be seen on our satellite or wind maps. Furthermore, our wind animation map, for example, offers a 7-day outlook, allowing you to forecast the future course of a storm. You also have the option of displaying our weather maps using a weather model of your choice. Many different models are available, for instance from DWD (ICON), meteoblue (NEMS), ECMWF (IFS), NOAA (GFS, NAM), UK MetOffice (UKMO) etc. In addition, we recommend consulting our global weather warning map, the current water surface temperature map and, of course, our forecasts (meteograms, MultiModel etc.) for any location in the world.

Stay safe!