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2020 Atlantic hurricane season

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This map shows the tracks of all tropical cyclones in the 2020 Atlantic hurricane season . The points show the location of each storm at 6-hour intervals. The colour represents the storm's maximum sus
MarioProtIV · Public domain

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Through Atlantic Ocean, El Niño–Southern Oscillation and Portugal

The season officially started on June 1 and officially ended on November 30. However, tropical cyclogenesis is possible at any time of the year, as demonstrated by the early formation of Tropical Storms Arthur and Bertha, on May 16 and 27, respectively. This was the sixth consecutive year with a pre-season system and the second of these seasons to have two, with the other being 2016. The first hurricane, Hurricane Hanna, made landfall in Texas on July 25. Hurricane Isaias formed on July 31, and made landfall in the Bahamas and North Carolina in early August, both times as a Category 1 hurricane; Isaias caused $4.8 billion in damage overall. In late August, Laura made landfall in Louisiana as a Category 4 hurricane, becoming the strongest tropical cyclone on record in terms of wind speed to make landfall in the state, alongside the 1856 Last Island hurricane and Ida. Laura caused at least $19 billion in damage and 77 deaths. September was the most active month on record in the Atlantic, with ten named storms. Slow-moving Hurricane Sally impacted the United States Gulf Coast, causing severe flooding. The Greek alphabet was used for only the second and final time, starting on September 17 with Subtropical Storm Alpha, which made landfall in Portugal on the following day.

Hurricane Zeta struck Louisiana on October 28, becoming the fourth named storm of the season to make landfall in the state, tying the record set in 2002. Zeta also struck the United States later in the calendar year than any major hurricane on record. On the last day of October, Hurricane Eta formed and made landfall in Nicaragua at Category 4 strength on November 3. Eta ultimately led to the deaths of at least 175 people and caused $8.3 billion in damage. Then, on November 10, Tropical Storm Theta became the record-breaking 29th named storm of the season and, three days later, Hurricane Iota formed in the Caribbean. Iota rapidly intensified into a high-end Category 4 hurricane, which also made 2020 the only recorded season with two major hurricanes in November. Iota ultimately made landfall in the same general area of Nicaragua that Eta had just weeks earlier and caused catastrophic damage. Overall, the tropical cyclones of the 2020 Atlantic hurricane season collectively caused at least 432 deaths and over $55.4 billion in damage.

All forecasting agencies predicted above-average activity, some well-above-average, citing factors such as the expectation of low wind shear, abnormally warm sea surface temperatures, and a neutral El Niño–Southern Oscillation or La Niña. Climate change likely played a role in the record-breaking season, with respect to intensity and rainfall. However, each prediction, even those issued during the season, underestimated the actual amount of activity. Early in 2020, officials in the United States expressed concerns the hurricane season could exacerbate the effects of the COVID-19 pandemic for coastal residents due to the potential for a breakdown of safety protocols such as social distancing and stay-at-home orders.

Seasonal forecasts

Forecasts of hurricane activity are issued before each hurricane season by noted hurricane experts, such as Philip J. Klotzbach and his associates at Colorado State University (CSU), and separately by NOAA forecasters. Klotzbach's team (formerly led by William M. Gray) defined the average (1981 to 2010) hurricane season as featuring 12.1 tropical storms, 6.4 hurricanes, 2.7 major hurricanes (storms reaching at least Category 3 strength in the Saffir–Simpson scale), and an accumulated cyclone energy (ACE) index of 106 units. Broadly speaking, ACE is a measure of the power of a tropical or subtropical storm multiplied by the length of time it existed. It is only calculated for full advisories on specific tropical and subtropical systems reaching or exceeding wind speeds of 39 mph (63 km/h). NOAA defines a season as above normal, near normal or below normal by a combination of the number of named storms, the number reaching hurricane strength, the number reaching major hurricane strength, and the ACE Index.

The first seasonal forecast was released on December 19, 2019, by Tropical Storm Risk (TSR), a public consortium consisting of experts on insurance, risk management, and seasonal climate forecasting at University College London, anticipating a slightly above-average hurricane season. This forecast was based on the prediction of near-average trade winds and slightly warmer than normal sea surface temperatures as well as a neutral El Niño–Southern Oscillation (ENSO) phase in the equatorial Pacific. In April and May 2020, various agencies issued forecasts for the season, with a hyperactive season predicted by the University of Arizona (UA) and North Carolina State University. The CSU anticipated heightened probabilities for hurricanes striking the Caribbean and the United States. On May 20, the UK Met Office predicted average activity with 13 tropical storms, 7 hurricanes, and 3 major hurricanes. A day later, NOAA released their forecast for an above-normal season, citing the continued ENSO-neutral or even La Niña conditions during the peak of the season.

After the season began, agencies updated their forecasts and generally anticipated an active year. The Atlantic experienced anomalously low wind shear and surface pressures during the month of July, leading to forecasts for a near-record-breaking season. The CSU and TSR predicted a total of 24 named storms, and NOAA predicted between 19 and 25 named storms. This was one of the most active forecasts ever released by NOAA for an Atlantic hurricane season.

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