Tropical Storm Don strengthened into a hurricane on Saturday, making it the first of the 2023 Atlantic hurricane season.
Tropical disturbances that have sustained winds of at least 39 miles per hour earn a name from the National Hurricane Center. Once winds reach 74 m.p.h., a storms is classified as a hurricane; at 111 m.p.h., it becomes a major hurricane. The National Hurricane Center estimated that Don had sustained winds of 75 m.p.h.
Don was about 480 miles from Newfoundland, Canada, as of Saturday afternoon and was moving north at 12 m.p.h. The hurricane was expected to dissipate Monday night or early Tuesday, and it did not pose a threat to land, the Hurricane Center said.
Don is the fifth tropical cyclone to reach tropical storm strength this year. (The Hurricane Center announced in May that it had reassessed a storm that had formed off the coast of the northeastern United States in mid-January, and that it had determined that it was a subtropical storm, making it the Atlantic’s first cyclone of the year.)
But that storm was not given a name retroactively, making Arlene, which formed in the Gulf of Mexico in June, the first named Atlantic storm this year. Bret and Cindy soon followed, making 2023 the first year since 1968 that there have been two named storms in the Atlantic Ocean in June simultaneously, according to Philip Klotzbach, a researcher at Colorado State University who studies hurricanes.
The Atlantic hurricane season starts on June 1 and runs through Nov. 30.
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, the organization said. There were 14 named storms last year after two extremely busy Atlantic hurricane seasons, in which forecasters ran out of human names and had to resort to backup lists of Greek letters. (There were a record 30 named storms in 2020.)
However, NOAA did not express a great deal of certainty in its forecast this year, saying there was a 40 percent chance of a near-normal season, a 30 percent chance of an above-normal season and a 30 percent chance of a below-normal season.
There were indications of above-average ocean temperatures in the Atlantic, which could fuel storms, and the potential for an above-normal West African monsoon season. The monsoon season produces storm activity that can lead to more powerful and longer-lasting Atlantic storms.
This year also features the intermittent climate phenomenon El Niño, which arrived in June. It can have wide-ranging effects on weather around the world, including a reduction in the number of Atlantic hurricanes.
“It’s a pretty rare condition to have the both of these going on at the same time,” Matthew Rosencrans, the lead hurricane forecaster with the Climate Prediction Center at NOAA, said in May.
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.)
But even in average or below-average years for hurricanes, there is still a chance that a powerful storm will make landfall.
As global warming worsens, that chance increases. There is a consensus among scientists that hurricanes are becoming more powerful because of climate change. And though there might not be more named storms overall, the likelihood of major hurricanes is increasing.
Climate change is also affecting the amount of rain that storms can produce. In a warming world, the air can hold more moisture, which means a named storm can hold and produce more rainfall, like Hurricane Harvey did in Texas in 2017, when some areas received more than 40 inches of rain in fewer than 48 hours.
Researchers have also found that storms have slowed down over the past few decades, and that they now remain stationary for longer periods.
When a storm slows down over water, the amount of moisture the storm can absorb increases. When a storm slows over land, the amount of rain that falls over a single location increases; in 2019, for example, Hurricane Dorian slowed to a crawl over the northwestern Bahamas, resulting in total rainfall of 22.84 inches in Hope Town.