The 2023 Atlantic Hurricane Season: An Above-Normal Season Despite Strong El Nino Conditions

The 2023 Atlantic hurricane season was above normal, with 20 named storms, 7 hurricanes, 3 major hurricanes and Accumulated Cyclone Energy that exceeded the 1991-2020 average. The most impactful storm of the season was Hurricane Idalia, which made landfall as a Category 3 hurricane in the Big Bend of Florida, resulting in five direct fatalities and $2.5 billion USD in damage.

The above-normal 2023 hurricane season occurred during a strong El Niño event with an August-October-averaged Oceanic Nino Index of 1.5°C. El Niño events tend to be associated with increased vertical wind shear across the Caribbean and tropical Atlantic, yet vertical wind shear during the peak hurricane season months of August-October was well below normal. The primary driver of the above-normal season was likely the record warmth in the tropical Atlantic Ocean, which effectively counteracted some of the canonical impacts of El Niño. The subtropical North Pacific was also much cooler than normal for an El Niño event, potentially also reducing El Niño’s impacts.

The drivers of the 2023 Atlantic hurricane season will be discussed in detail, including causes of the extreme anomalous warming that occurred across the tropical Atlantic and Caribbean during the boreal spring and summer. We will also test the sensitivity of the atmospheric circulation to sea surface temperatures in both the tropical and subtropical Pacific and the Atlantic using the atmospheric component of the Community Earth System Model version 6.