August 2024 Seasonal Hurricane Forecast

By Philip J. Klotzbach, Michael M. Bell, Alexander J. DesRosiers, and Levi G. Silvers

With Special Assistance from Carl J. Schreck III

In Memory of William M. Gray

We have maintained our forecast for an extremely active Atlantic hurricane season in 2024. We have reduced our forecast number of named storms slightly but have maintained all other numbers from our July update. 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 continue to anticipate cool neutral ENSO (El Niño Southern Oscillation) or La Niña during the peak of the Atlantic hurricane season, resulting in reduced levels of tropical Atlantic vertical wind shear. 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. 

1. Entire continental U.S. coastline - 56% (full-season average from 1880–2020 is 43%)
2. U.S. East Coast Including Florida Peninsula (south and east of Cedar Key, Florida) - 30% (full-season average from 1880–2020 is 21%)
3. Gulf Coast from the Florida Panhandle (west and north of Cedar Key, Florida) westward to Brownsville - 38% (full-season average from 1880–2020 is 27%)

1. 61% (full-season average from 1880–2020 is 47%)

Low-level trade wind flow has been utilized as a predictor in seasonal forecasting systems for the Atlantic basin ( Saunders and Lea 2008 ). When the trades are weaker-than-normal, sea-surface temperatures (SSTs) across the tropical Atlantic tend to be elevated, and consequently a larger-than-normal Atlantic Warm Pool (AWP) is typically observed ( Wang and Lee 2007 ). A larger AWP also correlates with reduced vertical shear across the tropical Atlantic. Weaker trade winds are typically associated with higher pressure in the tropical eastern Pacific (a La Niña signal) and lower pressure in the Caribbean and tropical Atlantic. Both of these conditions generally occur when active hurricane seasons are observed.

A similar predictor was utilized in earlier August seasonal forecast models ( Klotzbach 2007 ,  Klotzbach 2011 ). Anomalously warm SSTs in the subtropical North Atlantic are associated with a positive phase of the Atlantic Meridional Mode (AMM), a northward-shifted Intertropical Convergence Zone, and consequently, reduced trade wind strength ( Kossin and Vimont 2007 ). Weaker trade winds are associated with less surface evaporative cooling and less mixing and upwelling. This results in warmer tropical Atlantic SSTs during the August–October period.

Anomalous easterly flow at upper levels over the eastern Atlantic and northern tropical Africa provides an environment that is more favorable for easterly wave development into TCs. This anomalous easterly flow tends to persist through August–October, which reduces shear over the Main Development Region (MDR). This predictor also correlates with sea-level pressure (SLP) and SST anomalies over the tropical eastern Pacific that are typically associated with cool ENSO conditions.

The tropical Pacific is currently characterized by ENSO neutral conditions, with below-average SSTs in the eastern portion of the basin and near-average SSTs in the central portion of the basin (Figure 4). Over the past several weeks, SST anomalies across the eastern and central tropical Pacific have changed little, although there has been an anomalous reduction of upper ocean heat content anomalies. This reduction in upper ocean heat content is likely driven by anomalously strong trade winds which have tended to predominate across this portion of the basin. The Climate Forecast System is also calling for these enhanced trade winds to likely continue for the next several weeks, heralding a potential trend towards La Niña conditions. 

The North Atlantic remains extremely warm, with current Main Development Region (MDR; 10–20°N, 85–20°W) SSTs about 1.1°C warmer than normal and July-averaged MDR SSTs the second warmest on record (since 1979), trailing only 2023 by <0.1°C) (Figure 2). July MDR SSTs from 1979 to 2023 correlate with seasonal ACE at 0.59. Prior to 2024, the five warmest July-averaged SSTs were: 2023, 2010, 2005, 1998, and 2020. All but 2023 ended up hyperactive Atlantic seasons. The 2023 season still ended up with above average Atlantic hurricane activity despite strong El Niño conditions. 

The recent SST anomaly pattern matches quite well with the historical SST pattern in August that has correlated with active Atlantic hurricane seasons. Current SSTs in the MDR are tracking well above a typical hyperactive season. 

We will be issuing two-week forecasts for Atlantic TC activity during the climatological peak of the season from August–October, beginning today, Tuesday, 6 August and continuing every other Tuesday (20 August, 3 September, etc.) A verification and discussion of all 2024 forecasts will be issued on Tuesday, 26 November. All forecasts and verifications are available on our  website .  

We are frequently asked this question. Our answer is that it is possible to say something about the probability of the coming year’s hurricane activity which is superior to climatology. The Atlantic basin has the largest year-to-year variability of any of the global tropical cyclone basins. People are curious to know how active the upcoming season is likely to be, particularly if you can show hindcast skill improvement over climatology for many past years.  

Everyone should realize that it is impossible to precisely predict this season’s hurricane activity in early August. There is, however, curiosity as to how global ocean and atmosphere features are presently arranged with respect to the probability of an active or inactive hurricane season for the coming year. Our early August statistical and statistical/dynamical hybrid models show evidence on ~25–45 years of data that significant improvement over a climatological forecast can be attained. We would never issue a seasonal hurricane forecast unless we had models developed over a long hindcast period which showed skill.

We issue these forecasts to satisfy the curiosity of the public and to bring attention to the hurricane problem. There is a general interest in knowing what the odds are for an active or inactive season. One must remember that our forecasts are based on the premise that those global oceanic and atmospheric conditions which preceded comparatively active or inactive hurricane seasons in the past provide meaningful information about similar trends in future seasons.  

It is also important that the reader appreciate that these seasonal forecasts are based on statistical and dynamical models which will fail in some years. Moreover, these forecasts do not specifically predict where within the Atlantic basin these storms will strike. The probability of landfall for any one location along the coast is very low and reflects the fact that, in any one season, most U.S. coastal areas will not feel the effects of a hurricane no matter how active the individual season is.