Atlantic Hurricane Season Forecast 2021

August 2021: Hurricane Season is Ramping Up

The 2020 Atlantic season ended with a record total of 30 named storms, 13 of which became hurricanes. For 2021, initial indications were that the tropics would be just as favorable for development as they were last season.

While it may seem like this season has been relatively quiet, as of August 4, we've seen five named storms (including Category 1 Hurricane Elsa) putting the basin “above-normal” in terms of activity.

A calm and quiet July and first week of August is normal, even in an active season, as dry, sinking Saharan air dominates the Tropical Atlantic. Any tropical wave moving off the west coast of Africa quickly dissipated in the unfavorable environment.

Tropical activity typically begins to increase around the second week of August, reaching a peak around September 10th and steadily decreasing through the third week of October. Our tropical meteorologists are seeing signs pointing to increased tropical activity associated with the Madden-Julien Oscillation (MJO). As the MJO moves into the Atlantic Basin by mid-August, the Caribbean Sea should become a more favorable environment for storm development, though the Tropical Atlantic east of the Caribbean may remain hostile toward development, as it was last season.

Water temperatures across the Tropical Pacific also play a part in storm activity in the Atlantic Basin. With water temperatures currently trending cooler than normal, a moderate La Niña may develop by late fall, which would generate warm, rising air east of Mexico and Central America, enhancing storm development in the Atlantic Basin.

In summary, a slowly developing La Niña plus an MJO pulse moving into the Atlantic Basin will likely lead to a burst of storm activity, which could last into early November. For this reason, our forecast released in May remains true—19 named storms, 9 hurricanes and 5 intense hurricanes. This means that the remainder of the season could see an additional 14 named storms, 8 hurricanes and 5 intense hurricanes.

If you haven’t made all of your business preparations, now is the time. Scroll down for details on the long-range patterns that help to identify where and how many storms may develop this season.

The Atlantic Hurricane Season Risk Map above shows areas with above normal risk for impact and the predicted number of storms.

El Niño or La Niña

One important signal that we closely monitor prior to the start of and during the hurricane season is sea surface temperatures across the Tropical Pacific. Warming waters there would suggest the formation of an El Niño, a pattern that would enhance hurricane development in the East and Central Pacific but would inhibit development in the Atlantic Basin. Cooling waters across the Tropical Pacific would suggest that a La Niña could be forming. A La Niña would result in fewer hurricanes in the East and Central Pacific and enhanced hurricane activity across the Atlantic.

Water temperatures across the Eastern Pacific have remained cooler than normal through mid-May. Subsurface water is also cool. Models indicate that there is only a low chance of an El Niño by the peak of the season. While this may not necessarily be an enhancing factor, it will not likely inhibit development in the Atlantic Basin.

Atlantic Water Temperatures

Water temperatures across most of the Atlantic Basin remain above normal this spring. In addition, oceanic heat content remains above normal across the Caribbean Sea and the southern Gulf of Mexico. Since hurricanes require a deep layer of warm water to become strong, the increased oceanic heat content will provide the necessary energy for strong hurricanes in the Caribbean Sea and the Gulf of Mexico this season.

One area that may remain less than favorable for development is the Main Development Region east of the Caribbean. Water temperatures are cooler than normal there, and the atmosphere is not very favorable for strong hurricanes to develop, as was the case in 2020.

Analog Seasons

An analog season is a past season with a similar setup of ocean temperatures and atmospheric flow patterns to current conditions. The general thinking is that if the current state of the tropics closely matches a previous year, then seasonal activity during this season could be somewhat similar to the activity in the analog seasons. Our analog seasons for this season are 1996, 2001, 2005, 2008 and 2011. On average, these analog seasons produced 18 named storms, 9 hurricanes and 5 major hurricanes. Our analog years suggest another active season this year.

What to Expect Based on Current Conditions

The tropics appear set for another active season. An El Niño appears unlikely. Oceanic heat content remains high. Analog years suggest an active season. The greatest uncertainty concerns the favorability of the Main Development Region which stretches from the eastern Caribbean to the coast of Africa. Early indications are that this area may remain rather unfavorable for development, as it was last season. If that is the case, then activity may be focused north of the Caribbean and from the western Caribbean into the Gulf of Mexico.

The average number of named storms in the Atlantic over the past 30 years is 14, with 7 of those becoming hurricanes and 3 becoming major hurricanes. Since we see no strong inhibiting factors as far as development this season, we are forecasting another active hurricane season. For 2021, we are forecasting a total of 19 named storms, with 9 hurricanes and 5 major hurricanes. Most land areas will have an above-normal risk of a landfalling hurricane. The primary exception may be the islands of the eastern Caribbean from the Dominican Republic to Trinidad. With a less-than-favorable Main Development Region, there may be fewer hurricane threats to this area.

Changes for 2021

Outlooks will begin earlier on May 15 this year. This change reflects the number of tropical and subtropical storms which formed prior to June 1 in seven of the past 10 years. Another change comes from the World Meteorological Organization, the group in charge of hurricane names worldwide. The WMO has announced that it will retire the naming convention of using the Greek alphabet when a hurricane season runs out of names, as happened in 2005 and 2020. Instead, a supplemental list of names will be used.

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