The Tropical Storm Risk (TSR) April forecast has predicted North Atlantic hurricane activity in 2023 will be 25-30% below the 1991-2020 30-year norm, and around 20% below the long-term 1950-2022 norm.
Hurricane Ian – Source: Nasa Earth Observatory/AFP
TSR attributes its forecast for the below-norm activity to the weak El Nino conditions expected through the summer and autumn of 2023.
The firm suggests that these conditions favour enhanced trade wind strength, reduced vorticity and higher vertical wind shear over the tropical North Atlantic and Caribbean Sea where hurricanes form.
However, TSR notes, “Despite the expectation for a below-norm hurricane season in 2023, large uncertainties remain.
“These include the forecast strength of El Niño Southern Oscillation, the strength and sign of the North Atlantic Oscillation through Spring, and how warm the tropical Atlantic will be in August-September.
“Also, variance exists in the level of hurricane activity possible from the same climate factors and due to potential influences from variables which cannot be predicted, such as Saharan air outbreaks over the tropical Atlantic.”
TSR has given 2023 an ACE (Accumulated Cyclone Energy) value of 84, compared to the 1991-2020 30-year norm of 122.
The forecasting group sees only a 14% probability of an above-normal North Atlantic ACE in 2023, with a 43% likelihood of a near-normal ACE, and a 43% chance of a below-normal ACE season.
It expects 2 intense hurricanes, 6 hurricanes and 12 tropical storms. This compares to the 1991-2020 30-year norms of 3, 7 and 14 respectively.
