What is a tropical wave and how do they turn into hurricanes?

They don’t have names and rarely make headlines, but tropical waves are the first spark behind many of the Atlantic’s most powerful storms.

Before a hurricane earns a name and threatens land, it often begins as something smaller and lesser-known: a tropical wave.

What exactly is a tropical wave and why does it matter?

Tropical waves are clusters of showers and thunderstorms that are the seedlings of many of the storms that develop throughout the Atlantic hurricane season.

"Tropical waves originate over Africa as hot, dry air from the north clashes with moist, cooler air from the jungles in central Africa to create a jet stream of winds over portions of the continent," AccuWeather Lead Hurricane Expert Alex DaSilva said.

They roll off the coast of Africa near the Cabo Verde Islands and track over the Atlantic Ocean every few days, typically from May to November, like a conveyor belt of storms that is most active as the hurricane season approaches its peak in September.

With around 60 tropical waves documented across the Atlantic in a typical hurricane season, DaSilva notes that not every tropical wave becomes a threat. However, some can rapidly intensify under the right conditions.

"While many tropical waves move harmlessly out to sea, some tropical waves turn into the fiercest Atlantic hurricanes we see, such as Category 5 Hurricanes Andrew, Irma and Maria," DaSilva said. "About 80% of all major hurricanes in the Atlantic can trace their roots to a tropical wave."

It can take up to two weeks for a tropical wave to travel from Africa to the coast of North America, allowing time for development over warm ocean water. However, there is a wide range of potential tracks for the fledgling storm, meaning landfall is far from a guarantee.

Some of the longest-lived hurricanes of the entire Atlantic season start off as tropical waves near Africa and spend most or all of their life over the open waters of the Atlantic.

Hurricane Lorenzo from 2019 is a prime example of such a storm, as it was a major hurricane for three days and peaked as a Category 5 storm. It never made landfall, but after it lost hurricane status, it impacted the British Isles and western Europe.

Benefits of tropical waves

While tropical waves can pose a threat during hurricane season, they are also important for the Caribbean.

"During the early summer months, dry, dusty air typically moves across the Atlantic from Africa. It's these tropical waves that bring most of the summer rainfall to the islands of the Caribbean," DaSilva said. "Without these valuable tropical waves, many of these islands would receive little to no rainfall during the summer."

While most tropical waves never make headlines, the few that do can become historic storms. Understanding where they begin helps meteorologists stay one step ahead during the Atlantic hurricane season.

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