Sean was a tropical storm in the North Atlantic Ocean Wednesday afternoon Eastern time, the National Hurricane Center said in its latest advisory.
The tropical storm had sustained wind speeds of 40 miles per hour.
Tropical-storm-force winds, with sustained speeds of at least 39 miles per hour, typically arrive as weather conditions begin to deteriorate, and experts say their estimated arrival time is a good deadline for completing storm preparations and evacuating if asked to do so.
Arrival times and likelihood of damaging winds
Tropical-storm speeds or greater
Sean is the 18th named storm to form in the Atlantic in 2023. After a review of an unnamed January storm, Hurricane Center officials said it also would have qualified for a name.
In late May, the National Oceanic and Atmospheric Administration predicted that there would be 12 to 17 named storms this year, a “near-normal” amount. On Aug. 10, NOAA officials revised their estimate upward, to 14 to 21 storms.
There were 14 named storms last year, after two extremely busy Atlantic hurricane seasons in which forecasters ran out of names and had to resort to backup lists. (A record 30 named storms formed in 2020.)
This year features an El Niño pattern, which arrived in June. The intermittent climate phenomenon can have wide-ranging effects on weather around the world, and it typically impedes the formation of Atlantic hurricanes.
In the Atlantic, El Niño increases the amount of wind shear, or the change in wind speed and direction from the ocean or land surface into the atmosphere. Hurricanes need a calm environment to form, and the instability caused by increased wind shear makes those conditions less likely. (El Niño has the opposite effect in the Pacific, reducing the amount of wind shear.)
At the same time, this year’s heightened sea surface temperatures pose a number of threats, including the ability to supercharge storms.
Sources and notes
Tracking map Source: National Hurricane Center | Notes: Map shows probabilities of at least five percent.The forecast includes the five days starting up to three hours before the storm’s latest reported time and location. Wind speed probability data is not available north of 60.25 degrees north latitude.
Arrivals table Sources: New York Times analysis of National Hurricane Center data (arrival times); U.S. Census Bureau and Natural Earth (geographic locations); Google (time zones) | Notes: The table shows predicted arrival times of tropical-storm-force winds at selected cities if there is a chance such winds could reach those locations. “Earliest possible” times are times when, if tropical-storm-force winds do arrive, there is at least a 10 percent chance they will arrive at the time shown. “Most likely” times are times when, if tropical-storm-force winds do arrive, there is an equal chance that such winds will arrive before and after the time shown.
