By Amanda Delaney
As we enter the Atlantic Hurricane Season, which officially commences June 1 and lasts through November 30, how will it compare to previous seasons? The 2024 Atlantic Hurricane Season was very active, with 18 named tropical cyclones and Hurricane Beryl becoming the earliest and strongest hurricane to develop in the Caribbean at the end of June last year.
Meteorologists can determine how active a tropical cyclone season is by using the Accumulated Cyclone Energy (ACE) index. This is a summation of maximum sustained velocities when tropical cyclones are of tropical storm force or stronger. Climatologically (between 1991-2020), the ACE index averages near 121 at the end of the season, with anything over 160 registering as extremely active. The 2024 Atlantic tropical cyclone season ended at 161.
So how does this year look so far? Each year, Colorado State University issues a prediction for the upcoming tropical cyclone season in early April, which can be found here: https://tropical.colostate.edu/forecasting.html. The National Hurricane Center also issues a forecast in May. Several factors determine how active the hurricane season will be. One is the current status of El Niño/La Niña and how long this phase will last. Another is the sea surface temperatures in the Caribbean Sea, Gulf of Mexico and tropical Atlantic, and if they are above or below normal.
Although El Niño and La Niña are a reversal of sea surface temperatures in the Pacific Ocean, these phases can have impacts over the tropical Atlantic Ocean. During El Niño, the sea surface temperatures over the central and eastern tropical Pacific Ocean rise, while sea surface temperatures usually lower over the western tropical Pacific Ocean. Winds aloft usually weaken over the eastern Pacific Ocean but will strengthen over the tropical Atlantic Ocean. The strong winds aloft do not favor a buildup of thunderstorms over the tropical Atlantic Ocean and this can hinder tropical cyclone development. Therefore, El Niño can suppress tropical cyclone development over the Atlantic Ocean.
During La Niña, the opposite occurs. The sea surface temperatures rise in the western Pacific Ocean and lower over the central and eastern Pacific Ocean. La Niña has an opposite effect on the winds aloft as well: these winds will be stronger over the eastern Pacific Ocean and weaken over the Atlantic Ocean. During La Niña phases, the tropical cyclone season is generally more active as thunderstorms can strengthen without any hindrance and tropical cyclone development is more likely.
Currently, we are in a La Niña phase. However, the Climate Prediction Center is forecasting La Niña to diminish through the Spring and transition into a neutral phase between July through September. A neutral phase is basically when sea surface temperatures over the tropical Pacific Ocean are near normal and do not indicate either El Niño or La Niña. So winds aloft over the tropical Atlantic Ocean may be weak initially during June but this may slowly increase to normal levels as we progress through summer if La Niña weakens.
Last year, the sea surface temperatures over the Gulf of Mexico, Caribbean Sea and tropical Atlantic Ocean were abnormally warm by as much as 1-3°C above average (please refer to the first map below). Near mid-March, the Caribbean Sea and Gulf of Mexico are approximately 1-2°C above normal. The western tropical Atlantic Ocean is approximately 1 degree above normal. However, the eastern tropical Atlantic Ocean is 1-2°C below normal (as displayed in the second map below).
In Spring 2024, La Niña was in place, and the sea surface temperatures were abnormally warm across much of the tropical Atlantic Ocean. Therefore, it was no surprise that an active hurricane season was predicted and did occur. This year, though, with La Niña forecast to weaken to a neutral phase during the season and sea surface temperatures warmer than normal over the Caribbean Sea and Gulf of Mexico, tropical cyclone activity may have an early start towards these regions. However, if the neutral phase develops by mid to late summer and if the sea surface temperatures remain near normal over the eastern Atlantic Ocean, the Cape Verde (Eastern Atlantic) season of the tropics may have a slower start. Therefore, Weather Routing Inc. predicts a possibly more normal to slightly above normal tropical cyclone season in the Atlantic Ocean. Please refer to the table of our predicted numbers and the average statistics of tropical cyclones in the Atlantic.
| Average statistics (from 1990-2020) for the Atlantic Ocean | WRI Prediction | |
| Number of Named Tropical Cyclones | 14 | 13-16 |
| Number of Hurricanes | 7 | 4-6 |
| Number of Major Hurricanes | 3 | 2-3 |
Please note that a major hurricane is a Category 3 or higher hurricane on the Saffir Simpson Scale. We’ll see how the forecast trends continue to pan out later in the tropical cyclone season.
Caribbean Compass contributor Amanda Delaney is a senior meteorologist with
