FORT COLLINS, Col. — Colorado State University (CSU) continues to call for an above-normal Atlantic hurricane season on Thursday.
Colorado State University says sea surface temperatures averaged across the tropical and subtropical Atlantic are at record warm levels. Normally El Niño reduces Atlantic hurricane activity, while an extremely warm Atlantic increases hurricane activity, so how these diametrically opposing factors interact will determine exactly how much activity occurs in 2023.
The tropical Pacific currently has weak El Niño conditions – that is, water temperatures are somewhat above normal across the eastern and central tropical Pacific. This El Niño is likely to continue to intensify as the Atlantic hurricane season progresses. However, there is still uncertainty as to how strong El Niño will be.
El Niño tends to increase upper-level westerly winds across the Caribbean into the tropical Atlantic. The stronger upper-level winds result in increased vertical wind shear, which is the difference in direction and strength of winds from the lower to the upper levels of the atmosphere. Strong wind shear tears storms apart as they form.
Waters across the tropical and subtropical Atlantic continue to be near or at record levels across most of the basin. Warmer-than-normal waters in the tropical Atlantic provide more fuel for hurricanes. The extreme warmth that is currently observed across most of the North Atlantic is the primary reason for the above-average seasonal hurricane forecast, despite the El Niño.
Given the conflicting signals between a likely moderate/strong El Niño and a much warmer-than-normal tropical and subtropical Atlantic, the team stresses that there is more uncertainty than normal with this outlook.
The CSU Tropical Weather and Climate Research Team is predicting 18 named storms in 2023, including the five named storms that have already formed (an unnamed subtropical storm in January, Arlene, Bret, Cindy and Don). Of those, researchers expect nine (including Don) to become hurricanes and four to reach major hurricane strength (Saffir/Simpson categories 3-5) with sustained winds of 111 miles per hour or greater.
The team bases its forecasts on two statistical models, as well as four models that use a combination of statistical information and forecasts from dynamical models from the UK Met Office, the European Centre for Medium-Range Weather Forecasts, the Japan Meteorological Agency, and the Euro-Mediterranean Center on Climate Change. These models use 25-40 years of historical hurricane seasons and evaluate conditions including: Atlantic sea surface temperatures, sea level pressures, vertical wind shear levels, El Niño and other factors.
So far, the 2023 hurricane season is exhibiting characteristics similar to 1951, 1969, 1987, 2004, 2005, 2006, and 2012. The team predicts that 2023 hurricane activity will be about 130% of the average season. By comparison, 2022’s hurricane activity was about 75% of the average season.
The 2022 hurricane season will be most remembered for its two major hurricanes: Fiona and Ian. Fiona brought devastating flooding to Puerto Rico before causing significant surge, wind and rain impacts in the Atlantic Provinces of Canada as a post-tropical cyclone. Ian made landfall as a Category 4 hurricane in southwest Florida, causing over 150 fatalities and $113 billion in damage.
Colorado State University will issue a verification of all 2023 seasonal Atlantic hurricane forecasts in late November.