The 2024 tropical storm and hurricane season has recently slowed down

The official start of the tropical storm and hurricane season in the Atlantic and Caribbean for the 2024 season did get off to a fast start. At the end of last June, a very rare Category 5 hurricane, Beryl, formed that made landfall in Carriacou, Grenada, with sustained winds of 150 miles per hour July 1. The storm eventually made another landfall near Matagorda, Texas, with winds around 80 miles per hour.

Tropical Storm Chris hit eastern Mexico resulting in widespread flooding June 30. Hurricane Debby made landfall in Florida as a Category 1 and then a second landfall in South Carolina in early August. In mid-August, Hurricane Ernesto formed and brushed the eastern coastline of Canada’s Newfoundland.

From all indications, it was looking like a big season for tropical storm and hurricane activity in the Atlantic and Caribbean waters. However, as of the weekend, near the peak of the season, only five named storms had formed. There is the possibility of additional named storms this week as activity is showing signs of increasing.

Based on the 30-year average from 1991 to 2020, there is an average of about 14 named storms. Seven of 14 storms, on average, will form as hurricanes with three of them becoming major hurricanes. Sept. 10 is the approximate peak of the tropical storm and hurricane season which officially begins June 1 and ends Nov. 30.

Early predictions for the number of named storms by hurricane scientists were at least 20 named storms before the season ended. This was primarily based on the cooling of sea-surface temperatures along the equatorial regions, the above-normal readings of ocean waters in the Atlantic and Caribbean, and high humidity levels in regions where activity will often begin.

Typically, for tropical storms and hurricanes to form in the Atlantic and Caribbean waters, as well as the Gulf of Mexico, ocean temperatures need to be at least 80 degrees Fahrenheit. During the summer season in 2023, average sea-surface temperatures across these regions were at record levels. In some areas of the Atlantic, readings were in the mid-to-upper 80s.

For the 2024 season, ocean waters along the equatorial regions are still cooling down and the Atlantic, the Caribbean waters continue to be much warmer than normal, along with high humidity levels in the Atlantic. Despite some of the best conditions for tropical storm formation, it has been very calm since the middle of August. As of the weekend, this is the longest streak of calm, in terms of tropical storm formation, in over 50 years.

During an active season, most hurricanes will form off the coast of Central Africa and will originate from developing storms, or a complex of thunderstorms, in that region. This year, most of the systems that were forming were directed farther to the north than usual, which is near the Sahara Desert, away from the high-humidity regions. With the dry air and dusty conditions of the nearby desert, the storms were not able to form properly.

By contrast, during El Niño years, especially strong ones, the formation of tropical storms and hurricanes in the Atlantic and Caribbean waters was often limited due to increased wind shear. However, the record warmth of the Atlantic sea-surface temperatures in 2023 helped to create an above-average 20 named storms, which was the fourth highest since 1950. Therefore, we can get above-average named storms with less-than-ideal conditions.

Although tropical storm formation has been limited, conditions can change very quickly. Based on climatology, approximately 40% of the season’s named storms will form after the climatological peak of tropical storms and hurricane formation after Sept. 10.

For example, major hurricanes have also formed in October and November. In October 2018, Hurricane Michael hit the Florida Panhandle as a devastating Category 5 storm Oct. 10. In November 2022, Hurricane Nicole, a Category 1 storm, made landfall twice in Florida on Nov. 10.

In terms of our local weather, the hot temperatures early this week will come to an end. However, another warm spell may return in several weeks. For the first week of September, the average high in Coeur d’Alene was a hot 91 degrees, compared to a normal of 78 degrees. By the end of the week, readings are expected to cool into the 60s and 70s in most areas.

The long-range computer models are indicating a chance of rainfall later this week. As I mentioned earlier, since June 20, the first day of “astronomical summer” only 0.82 inches of rain was measured in Coeur d’Alene. With the unlikely chance that we don’t see any additional moisture between now and Sept. 22, this would be the driest astronomical summer season since 2006 when we had 0.83 inches of moisture. According to Cliff’s records, this would be the third driest period since 1895. However, we do expect conditions to flip to the wetter side later in the fall season.

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Contact Randy Mann at randy@longrangeweather.com.