Ag Weather Forum

A recent blog post on NOAA's climate.gov website by Matthew Rosencrans of the NOAA Climate Prediction Center (CPC) has some points on the United States tropical weather outlook for this 2024 season that bear amplifying. Matthew Rosencrans is the CPC's lead hurricane season forecaster. The 2024 hurricane season began on June 1 and will run through Nov. 30. NOAA/CPC places the odds of above-average tropical storm and hurricane formation this season at 85%. A total of 17 to 25 named tropical storms are expected to form (average is 14). The number of hurricanes expected is eight to 13 (average is 7). The number of major hurricanes predicted is four to seven (average is three).

Already we're seeing the first named one of the season: The extremely dangerous Category 4 Hurricane Beryl is hitting the southeast Caribbean on Monday. It went from a tropical depression to a major hurricane in only 42 hours during the weekend, according to the National Hurricane Center.

The post by Rosencrans highlights what might be described as a trifecta of large-scale factors for the season. They include:

-- La Nina and its supportive circulation pattern for tropical storm development. Over North America, the large-scale atmospheric flow with La Nina leads to weaker crosswinds in the atmosphere from the surface to about 7 miles above the ground. These weaker crosswinds allow tropical storms and hurricanes to build higher and higher. Conversely, El Nino results in stronger tropical-latitude winds, which can tear apart tropical systems and inhibit their growth.

-- Warm Atlantic Ocean waters. Rosencrans noted that the tropical Atlantic Ocean region where most tropical storms form, is already very warm. "The ocean temperatures in the Atlantic Basin are at record-warm levels. In fact, the temperatures in May were closer to what we would expect in late August, when we are approaching the traditional peak of the hurricane season! Approximately 90% of Atlantic tropical storm and hurricane activity happens during August through October," Rosencrans noted.

Even before it makes landfall Monday morning, Hurricane Beryl has been already called historic -- it's the earliest Category 4 hurricane on record.

-- Robust Africa monsoon flow. The third member of this tropical trifecta is the monsoon flow from the African continent, known as the West African Monsoon. This year's monsoon, with winds blowing toward the Atlantic off the African continent, is expected to be stronger than usual. That enhances the activity of disturbances called African easterly waves that develop across the African continent and over the Atlantic. These disturbances often form the beginnings of tropical storms and hurricanes.

The tropical season has already put its stamp on Midwest weather. Some moisture from Tropical Storm Alberto, which formed in the Gulf of Mexico on June 19, flowed northward around the edge of a strong southeastern U.S. heat dome and was included in the so-called "ring of fire" cluster of thunderstorms which brought heavy, flooding rain to the Upper Midwest during the weekend of June 21-23.

The full article by Rosencrans is available here: https://www.climate.gov/…

Bryce Anderson can be reached at Bryce.Anderson@dtn.com

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