The National Hurricane Center early Saturday declared the arrival of Subtropical Storm Ana, making 2021 the seventh year in a row that a named storm has developed in the Atlantic Ocean ahead of the official June 1 start of hurricane season.

Scientists say the recent tendency for preseason storms is another sign of the effects of climate change on tropical weather systems.

The storm was named at 5 a.m. Eastern time, and as of 8 a.m., Ana was centered 180 miles northeast of Bermuda, drifting west-southwest at 3 mph. Because of its proximity to the island, which may get grazed by some showers and gusty winds, a tropical storm watch is in effect Saturday. By Saturday night, Ana is forecast to zip away to the northeast while slowly weakening. The Hurricane Center predicts it will dissipate by Monday.

Classified as a subtropical storm, Ana features a mix of tropical and midlatitude characteristics. Subtropical storms often form along decaying cold fronts at the center of nontropical low-pressure systems, when warm ocean waters sustain more vigorous shower and thunderstorm activity.

Brian McNoldy, a tropical weather expert at the University of Miami, has documented a trend toward earlier tropical storm formation at the same time climate change has exerted a warming effect on the oceans.

Some of the increase in preseason storm activity, McNoldy tweeted, is related to increased storm detection due to improved monitoring from weather satellites. “But the expansion of favorable ocean temperatures earlier in the season is allowing this activity to happen too,” he wrote.


The preseason storm activity “seems to be, certainly, very attached to sea surface temperature,” Jim Kossin, an atmospheric scientist with the National Oceanic and Atmospheric Administration, told the Capital Weather Gang last July. “There’s no question about that.”

Subtropical storm Ana formed in an ocean zone where a preseason storm hasn’t developed since at least 1950.

Due to this tendency for more preseason storms, the Hurricane Center has been conferring with the World Meteorological Organization to consider moving the nominal start of Atlantic hurricane season up to May 15. Just over a week ago, the east Pacific observed its earliest named storm on record.

Ana comes just two days after the NOAA released its 2021 Atlantic hurricane season outlook calling for above normal storm activity for the sixth straight year. The agency is calling for a 60 percent likelihood of an above-average season, with a 70 percent probability of 13 to 20 named storms. Six to 10 of them should be hurricanes.

This marks the third time a preseason storm named Ana has formed in the past 20 years in the Hurricane Center’s rotating list of storm names. The next storm to be named will be known as Bill.

Ana formed early Saturday as another system being monitored by the Hurricane Center moved ashore along the coast of southeastern Texas. That system did not sufficiently organize to earn a name but is predicted to produce heavy rainfall in coastal Texas and Louisiana on Saturday.

“Given the complete saturation of soils with ongoing river flooding along the Texas and Louisiana coastal areas, these rains could lead to flash, urban, and additional riverine flooding across this region,” the Hurricane Center wrote.

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The Washington Post’s Matthew Cappucci contributed to this article.