Tropical Storm Tammy Forms in the Atlantic

Tropical Storm Tammy formed in the North Atlantic Ocean Wednesday afternoon, according to the National Hurricane Center.

The tropical storm had sustained wind speeds of 40 miles per hour, and was expected to reach the Leeward Islands in the Caribbean later this week.

When will damaging winds arrive?

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.

Tammy is the 19th 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.