Colorado State University

Seasonal Hurricane Forecasting

Atlantic Seasonal Hurricane Activity

Forecast for 2024 Hurricane Activity

Forecast Parameters CSU Forecast for 2024* Average for 1991-2020
Named Storms 25 14.4
Named Storm Days 120 69.4
Hurricanes 12 7.2
Hurricane Days 50 27.0
Major Hurricanes 6 3.2
Major Hurricane Days 16 7.4
Accumulated Cyclone Energy (ACE)+ 230 123
ACE West of 60 degrees longitude 140 73
*CSU released its first seasonal forecast for 2024 on Thursday, April 4th, and an updated forecast on July 9th.
+A measure of a named storm’s potential for wind and storm surge destruction defined as the sum of the square of a named storm’s maximum wind speed (in 104 knots2) for each 6-hour period of its existence.

We anticipate an extremely active 2024 hurricane season in the Atlantic basin.

We have slightly increased our forecast and continue to call for an extremely active Atlantic hurricane season in 2024. Sea surface temperatures averaged across the hurricane Main Development Region of the tropical Atlantic and Caribbean remain near record warm levels. Extremely warm sea surface temperatures provide a much more conducive dynamic and thermodynamic environment for hurricane formation and intensification. We anticipate cool neutral ENSO or La Niña during the peak of the Atlantic hurricane season, resulting in reduced levels of tropical Atlantic vertical wind shear. Hurricane Beryl, a deep tropical Category 5 hurricane, is also a likely harbinger of a hyperactive season. This forecast is of above-normal confidence. We anticipate a well above-average probability for major hurricane landfalls along the continental United States coastline and in the Caribbean. As with all hurricane seasons, coastal residents are reminded that it only takes one hurricane making landfall to make it an active season. Thorough preparations should be made every season, regardless of predicted activity.

Read the full forecast here

Check the latest tropical cyclone impact probabilities here

2024 CSU Tropical Meteorology Project Forecast Schedule

Two-week Forecasts of North Atlantic Tropical Cyclone Activity


Forecast Factors

In 1984, Dr Bill Gray at Colorado State University documented that Atlantic hurricane activity responded to a variety of large-scale atmospheric and oceanic parameters spanning various portions of the globe. These large-scale factors interact with the global climate system in such a way that then alter the environment of the tropical Atlantic, where most major hurricanes develop and intensify. For example, hurricanes are more likely to develop when they traverse through an environment of low vertical wind shear (the change in wind direction and speed with height in the atmosphere), high sea surface temperatures and high mid-level moisture. Several parameters that have been documented to impact Atlantic hurricanes are discussed here in more detail.

Atlantic Ocean Thermodynamics

A warmer-than-normal tropical North Atlantic Ocean is known to typically create conditions more favorable for hurricane formation and intensification. In addition to enhancing latent and sensible heat fluxes that fuel tropical cyclones, a warmer tropical North Atlantic also drives lower pressures and reduced low-level trade winds, which also feed back to a more conducive environment for hurricanes.

It is important to note that the warming of the tropical North Atlantic Ocean also be measured relative to warming in other areas. One frequently utilized metric is relative sea surface temperature, which measures the difference between tropical North Atlantic Ocean sea surface temperatures and sea surface temperatures in the rest of the tropics (Vecchi et al. 2008). This index is important because it dictates where anomalous rising and sinking motion is likely to occur. When the tropical North Atlantic Ocean is anomalously warmer than the remainder of the tropics, anomalous rising motion is likely in this area, favoring enhanced tropical cyclone activity.

Averaged sea surface height anomalies measured by Jason 2 in the Pacific Ocean, observed at the beginning of October 2015. Credit: NASA

An additional index that is often utilized to assess the favorability of the tropical North Atlantic Ocean is the Atlantic Meridional Mode (AMM) (Kossin and Vimont 2007). The AMM assesses both the thermodynamic and dynamic state of the tropical North Atlantic Ocean through analysis of low-level winds as well as sea surface temperatures. A positive phase of the AMM is associated with a warmer tropical North Atlantic relative to the tropical South Atlantic, as well as with reduced trade winds in the tropical North Atlantic. Positive phases of the AMM are generally characterized by above-normal Atlantic hurricane activity.

El Niño Southern Oscillation

At the interannual timescale, the prime driver of Atlantic tropical cyclone variability is generally considered to be El Niño Southern Oscillation (ENSO). ENSO is driven by changes in ocean temperature in the tropical Pacific, where above average conditions (El Niño) in the Central and Eastern Pacific shift the convective activity in the tropical Pacific eastward, and modify the Walker cell throughout the tropics. The influence of ENSO on Atlantic tropical cyclone activity is well documented and is understood to occur mainly through local changes in vertical wind shear: during El Niño (La Niña) conditions, the eastward (westward) shift in convection in the tropical Pacific leads to anomalous upper-level westerlies (easterlies) over the Atlantic, which then increases (decreases) the vertical wind shear, thus decreasing (increasing) tropical cyclone activity.

Dust streaming from Mauritania, Senegal, western Sahara and maybe other countries farther East, and heading West toward South America and the Gulf of Mexico. Composite image made with data from VIIRS acquired by Aqua/MODIS on June 24, 2014. Credit: NASA

Sahel Precipitation

Changes in convective precipitation over the Sahel region has been shown to impact zonal winds in the upper-troposphere, which in turn modulate vertical wind shear over the Main Development Region and influence the conditions of cyclogenesis over the tropical Atlantic. It is possible that changes in the nature of the African Easterly Waves coming off the African continent might also be playing a role. Years with higher Sahel rainfall tend to be associated with more active hurricane seasons. The influence of the Sahel precipitation is mostly felt when the thermodynamical conditions over the tropical Atlantic are not conducive to hurricane formation.

Saharan Dust

Dust outbreaks from West Africa impact tropical cyclone activity by reducing Atlantic tropical sea surface temperatures ahead of the hurricane season. Episodes of dust outbreak are also associated with extremely dry air coming from the Sahara, another factor detrimental to cyclone formation.

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