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31st May 2023

Moody's RMS-The North Atlantic Hurricane Season
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The 2023 North Atlantic hurricane season officially gets underway tomorrow, and runs for six months through to 10th November. Ahead of the start of the season, several forecasting agencies and groups have issued seasonal outlooks that provide a guide to the expected level of activity this year. The forecasts are typically revised in early August ahead of the historically most active months of the season, August, September, and October.
Most forecasting groups and agencies predict near-normal activity in the basin this season, which comprises the North Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico:
-The U.S. National Oceanic and Atmospheric Administration (NOAA) has forecasted 12–17 named storms, of which 5–9 are expected to become hurricanes, and 1–4 of those are forecasted to become major hurricanes(Category 3 or stronger).
-NOAA has a 70% confidence in these ranges.
-On average, the North Atlantic sees 14 named storms, 7 hurricanes, and 3 major hurricanes.
-Outlooks from other meteorological forecast agencies and groups are broadly in line with the guidance issued by NOAA in calling for a near-normal season, however, most forecasts exhibit increased uncertainty compared to normal due to the factors influencing this year’s forecast.
These forecasts reflect the state of the main oceanic and climate factors that historically influence hurricane activity in the basin: the El Niño-Southern Oscillation (ENSO) and sea surface temperatures in the North Atlantic.
A transition from ENSO-neutral conditions to an El Niño phase is expected in the next couple of months, with a greater than 90% chance that El Niño persists until late 2023. El Niño conditions in the Pacific typically increase the vertical wind shear across the North Atlantic, which generally hinders hurricane activity by providing a less favourable atmosphere for storm development and intensification. However, sea surface temperatures in the tropical North Atlantic are expected to remain well above average throughout the season, which would typically result in increased hurricane activity in the basin. These competing factors—some that suppress storm development and some that fuel it—result in NOAA’s overall forecast for a near-normal season. There remains a possibility that the season could conclude with below- or above-normal activity if one of these competing factors exhibits a greater influence over the season.
If the current forecasts verify, 2023 would be a second consecutive near-normal season. However, these forecasts only provide a guide to the anticipated level of activity across the North Atlantic; they do not provide an indication of the expected number of storms to threaten land or make landfall. Although long-term statistics indicate that the probability of a hurricane making landfall in the US increases during more active seasons, there are notable exceptions. 2010 was a particularly active year but only one tropical storm made landfall in the US. Conversely, Hurricane Andrew, one of the most intense and costliest hurricanes in US history, was one of only seven storms to develop during the quiet 1992 season. It can only take one landfalling storm to make the season memorable or costly.
Throughout the season, the Moody’s RMS Event Response team will be closely following all tropical activity in the North Atlantic and can provide insight and comment on hurricane formation, their movements, potential landfalls, and post-landfall industry loss estimates. This includes unique Moody’s RMS HWind analysis that provides detailed storm information and forecast trajectories.
Moody’s RMS will publish a 2023 Northern Hemisphere Tropical Cyclone Outlook later in June.

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