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There are two main factors that suggest this year’s hurricane season could be busier than usual: warmer-than-average sea surface temperatures in the Atlantic Ocean and low probabilities that a climate pattern known as El Niño will return.

Researchers closely monitor conditions in the tropical and subtropical Atlantic because warm ocean temperatures provide some of the fuel for big storms.

“Warm ocean waters are one of the main ingredients for tropical cyclone development, which refers to both hurricane and lesser storms like tropical depressions and tropical storms,” said Daniel Brouillette, an atmospheric and climate scientist at Pennsylvania State University. “The warmer those waters are, the more likely that tropical cyclones will develop, and also the stronger they may be if they do develop.”

Brouillette was part of a team at Penn State that published a separate early hurricane season forecast April 21. Their models similarly predict an active season, with as many as 20 named storms estimated for the year.

Both the Colorado State and the Penn State forecasts also found that El Niño conditions are unlikely to develop this year. That phenomenon, characterized by unusually warm water in the Pacific Ocean, influences climate patterns around the world and typically increases wind shear in the Atlantic, which can tear hurricanes apart and disrupt major storms as they are forming.

The counterpart of El Niño, known as La Niña, is characterized by unusually cool temperatures in the equatorial Pacific, and also drives global climate patterns. In the case of La Niña, there is typically less wind shear over the Atlantic, making for conditions that are more conducive for tropical cyclone development, Brouillette said.

Though there is strong consensus so far that this year’s hurricane season will be a busy one, Klotzbach said it is still early, and even minor changes in ocean or atmospheric conditions can influence the outcome of the season.

“A lot can happen between April and June,” he said. “There are a lot of signs pointing to an active season, but I wouldn’t say it’s a slam dunk.”

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Still, scientists will be closely monitoring developments in the upcoming hurricane season, which runs until Nov. 30, because it will be unfolding against the backdrop of the coronavirus outbreak.

“The hurricane season is coming whether we want it to or not,” Klotzbach said. “And regardless of the seasonal forecasts, people need to be prepared every year.”

Preparations may be particularly important this year, as emergency resources in many states, and at the federal level, are likely already strained because of the pandemic.

“It would behoove emergency managers, but also the public, to hedge their bets that the pandemic will still be going on later in the summer and fall,” Brouillette said, “and to make as many preparations as possible right now to anticipate difficulties with that.”