Ahead of the start of the season, several forecasting groups and agencies have issued seasonal outlooks that provide a guide to the expected level of activity this year. The forecasts are revised in early August ahead of the peak period of the season, which occurs between August and October.
Most forecasting groups and agencies are anticipating above-average 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 forecast 13-19 named storms, 6-10 hurricanes, and 3-6 major hurricanes. On average, the Atlantic sees 12 named storms, of which 6 become hurricanes, and 3 of those become major hurricanes. Outlooks from other forecast groups and meteorological agencies are broadly in line with the guidance issued by NOAA in calling for an above-average season.
These forecasts reflect the state of the two main oceanic and climate factors that historically dictate hurricane activity in the basin: the El Niño-Southern Oscillation (ENSO) and sea surface temperatures in the equatorial Atlantic. ENSO is forecast to remain in a cool-neutral phase during the summer with an increasing chance of La Niña conditions later in the fall. If La Niña does develop, it would help reduce the vertical wind shear across the Atlantic, which typically enhances hurricane activity. Moreover, sea surface temperatures in the tropical Atlantic are expected to remain above average throughout the summer, which also typically increases hurricane activity in the basin.
These forecasts only provide a guide to the anticipated level of activity across the 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 U.S. increases during more active seasons, there are notable exceptions. 2010 was a particularly active year in the Atlantic but only one tropical storm made landfall in the United States (Tropical Storm Bonnie). Conversely, Hurricane Andrew, one of the most intense and costliest hurricanes in U.S. history, was one of only seven storms to develop during the quiet 1992 season. It therefore only takes one landfalling storm to make the season a memorable one.
The 2020 season got off to an early start with the formation of tropical storms Arthur and Bertha. Arthur developed off the east coast of Florida on May 17 and bypassed offshore of North Carolina the following day. The system brought heavy rain and strong winds to the Outer Banks of North Carolina but did not cause any significant damage. An area of disturbed weather just offshore of South Carolina organized into Tropical Storm Bertha on May 27 and made landfall several hours later east of Charleston. Bertha brought heavy rainfall to the Carolinas and Virginia.
2020 marked a record sixth consecutive year (2015-20) that at least one storm has been named before the official start of the North Atlantic hurricane season on June 1. 2020 is also only the sixth season on record that two storms had been named before June 1. There’s no historical relationship between the date of the first named storm and the overall seasonal hurricane activity, so the early start to 2020 doesn’t necessarily provide us with any clues as to how the 2020 hurricane season might pan out.
Throughout the season, the RMS Event Response team will be closely following all tropical activity and can provide insight and comment on hurricanes forming, their movements, potential landfalls and industry loss estimates post landfall, including unique HWind analysis giving detailed formations and trajectories.
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