On the one hand, El Niño normally reduces tropical storm activity in the Atlantic. On the other, warmer-than-ever surface waters increase storm activity. Which will prevail?
Warm waters against El Niño
On August 3, Colorado State University released an updated forecast for the 2023 hurricane season. Normally, El Niño is expected to reduce tropical activity in the Atlantic. But despite the development of a fairly robust El Niño, the phenomenon is still modest for the time being. Water surface temperatures in the Pacific remain higher than average.
There is still some uncertainty as to the intensity of El Niño over the coming months. El Niño tends to amplify high-altitude winds from the west towards the Caribbean and the Atlantic Ocean. This increases shear, the difference between the direction and intensity of winds at high and low altitudes. Strong shear is a disadvantage for hurricane formation, tearing tropical storms apart.
Lots of "hot" water
However, water temperatures in the tropical and subtropical Atlantic continue to reach record levels. In some places, it's more than 5 degrees above normal. Warmer water provides energy for hurricanes. The high water temperature in the North Atlantic is the main reason for this more active-than-normal hurricane season forecast.
Forecast: 18 tropical storms
The Tropical Meteorology Project at the University of Colorado predicts that 18 tropical storms will form in 2023. This number includes the five already on record: January, Arlene, Brett, Cindy and Don. This would leave 13 tropical storms by the end of the year.
Fig. 1; Source: Pixabay
Prognosis: four major hurricanes
Of these, the team of experts predicts that nine will become hurricanes, including Don, which has already passed. Four will become major hurricanes, either category 3, 4 or 5 on the Saffir/Simpson scale, with sustained winds of over 178 km/h.
A more active season
Despite the disasters of Fiona and Ian, the 2022 season was almost 25% less active than average in terms of cumulative tropical cyclone energy. But the numbers of named storms and hurricanes were close to normal. The University of Colorado team predicts that the 2023 season will be 30% more active than average.