The 2020 Atlantic hurricane season was the most active Atlantic hurricane season in recorded history in terms of the total number of tropical and subtropical cyclones, with 31 such systems forming throughout the season and all but one becoming a named storm, breaking the previous record set in 2005. Of the 30 named storms, 14 developed into hurricanes, and a record-tying seven further intensified into major hurricanes. It was, after the aforementioned 2005 season, the second and final season to use the Greek letter storm naming system. 11 of the 30 named storms made landfall in the contiguous United States, breaking the record of nine set in 1916. During the season, 27 tropical storms established a new record for earliest formation date by storm number. This season also featured a record ten tropical cyclones that underwent rapid intensification, tying it with 1995, as well as tying the record for most Category 4 hurricanes in a singular season in the Atlantic basin. This unprecedented activity was fueled by a La Niña that developed in the summer months of 2020, continuing a stretch of above-average seasonal activity that began in 2016. Despite the record-high activity, this was the first season since 2015 in which no Category 5 hurricanes formed.
The season officially started on June 1 and officially ended on November 30. These dates, adopted by convention, delineate the period of the calendar year during which tropical cyclogenesis most often occurs. However, the formation of tropical and subtropical systems 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.
The 2020 Atlantic hurricane season was the most active Atlantic hurricane season in recorded history in terms of the total number of tropical and subtropical cyclones, with 31 such systems forming throughout the season and all but one becoming a named storm, breaking the previous record set in 2005. Of the 30 named storms, 14 developed into hurricanes, and a record-tying seven further intensified into major hurricanes. It was, after the aforementioned 2005 season, the second and final season to use the Greek letter storm naming system. 11 of the 30 named storms made landfall in the contiguous United States, breaking the record of nine set in 1916. During the season, 27 tropical storms established a new record for earliest formation date by storm number. This season also featured a record ten tropical cyclones that underwent rapid intensification, tying it with 1995, as well as tying the record for most Category 4 hurricanes in a singular season in the Atlantic basin. This unprecedented activity was fueled by a La Niña that developed in the summer months of 2020, continuing a stretch of above-average seasonal activity that began in 2016. Despite the record-high activity, this was the first season since 2015 in which no Category 5 hurricanes formed.
The season officially started on June 1 and officially ended on November 30. These dates, adopted by convention, delineate the period of the calendar year during which tropical cyclogenesis most often occurs. However, the formation of tropical and subtropical systems 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.
Seasonal summary
Background
Overall, the Atlantic tropical cyclones of 2020 collectively resulted in 416 deaths and more than $51.114 billion in damage, making the season one of the costliest on record. The 2020 Atlantic hurricane season officially began on June 1 and ended on November 30. However, tropical cyclogenesis began in the month of May, with tropical storms Arthur and Bertha, marking the sixth consecutive year with an off-season storm. It was the first year with two pre-season storms since 2016, and the first to have two named storms in May since 2012. The season featured 31 tropical depressions, 30 of which became tropical or subtropical storms. The latter total surpassed the previous record of 28 set in 2005. There were 14 hurricanes, which was the second most for a season, behind only 2005. Seven of the hurricanes intensified into major hurricanes, tying 2005 for the most in one season. It was the fifth consecutive Atlantic hurricane season with above average activity, exceeding the previous longest streak of four years between 1998 and 2001. A total of 10 tropical cyclones underwent rapid intensification, tying the record set in 1995.
The season extended the warm phase of the Atlantic multidecadal oscillation ongoing since 1995. The warm AMO tends to produce tropical cyclones that are more intense and have longer durations. The presence of a La Niña contributed to the unprecedented amount of activity. Sea surface temperatures across the Atlantic basin were warmer-than-average. A strong west African monsoon, favorable wind patterns from Africa, weaker vertical wind shear all aided in the formation of tropical cyclones. The ACE index for the 2020 Atlantic hurricane season was 180 units, reflecting the season's well-above-average activity. Climate change likely played a role in the record-breaking season. Scientific American noted that "As the oceans absorb more and more of the excess heat trapped by greenhouse gases, waters will get warmer earlier in the season, which could help set new records in the future." A formal attribution study showed that the extreme rainfall was higher than in a counterfactual without climate change, especially for high-intensity storms. Matthew Rosencrans, the lead forecaster at the National Weather Service, emphasized that climate change has been linked to the intensity of storms and their slow movements, but not to the amount of activity, which might instead be increasing due to improvements in technology.
The season occurred during the COVID-19 pandemic. Early in the year, officials in the United States expressed concerns the hurricane season could potentially exacerbate the effects of the pandemic for U.S. coastal residents. As expressed in an op-ed of the Journal of the American Medical Association, "there exists an inherent incompatibility between strategies for population protection from hurricane hazards: evacuation and sheltering (i.e., transporting and gathering people together in groups)", and "effective approaches to slow the spread of COVID-19: physical distancing and stay-at-home orders (i.e., separating and keeping people apart)." A study published by GeoHealth in December 2020 confirmed a correlation between destination counties (a county in which an evacuee flees to) and an increase in COVID-19 cases.
Record activity
The season featured activity at a record pace. The third named storm and each one from the fifth onwards formed on an earlier date in the year than the corresponding storm in any other season since reliable records began in 1851. In late July, Hanna struck South Texas as the first hurricane of the season. It was followed by the second hurricane of the season, Isaias, which moved through the Caribbean and eastern United States. July 2020 tied 2005 for the most active July on record in the basin, with five named storms. Laura and Marco formed toward the end of August, and the former became the first major hurricane of the season. Laura made landfall in southwest Louisiana on August 27 at Category 4 strength with 150 mph (240 km/h) winds. September featured the formations of nine named storms, coinciding with the peak of the hurricane season and the development of La Niña conditions. Hurricane Nana hit Belize in early September. Paulette was the first hurricane to hit Bermuda since Gonzalo in 2014. Hurricane Sally hit the Gulf Coast of the United States as a slow-moving Category 2 hurricane. Teddy, the season's eighth hurricane and second major hurricane formed on September 12, while Vicky formed two days later. With the formation of the latter, five tropical cyclones were simultaneously active in the Atlantic basin for the first time since 1971. Alpha developed atypically far east in the Atlantic and became the first tropical cyclone on record to strike Portugal. Beta's intensification into a tropical storm made September 2020 the most active month on record, with 10 named storms. Beta went on to make landfall in Texas and impact the Deep South before dissipating, marking an abrupt end to the heavy peak season activity.
October and November were extremely active, with seven named storms developing, five of which intensified into major hurricanes – more than twice the number recorded during this period in any previous season. Hurricane Gamma hit the Yucatán Peninsula in early October before being absorbed by Hurricane Delta, which hit the region a few days later. Delta struck Louisiana as a hurricane on October 9. Hurricane Epsilon became a major hurricane near Bermuda. Toward the end of the month, Hurricane Zeta struck the Yucatán Peninsula and later Louisiana, becoming the latest landfall for a major hurricane in the continental United States. In November, two Category 4 hurricanes hit Nicaragua within a two-week period. Hurricane Eta moved from Central America to the Greater Antilles and southeastern United States. The season's final hurricane was also its strongest. Hurricane Iota attained maximum sustained winds of 155 mph (249 km/h) and a minimum barometric pressure of 917 mbar (27.1 inHg), before hitting Nicaragua. The 2020 season became the first with two major hurricanes in the month of November.
A total of eleven named storms made landfall in the United States, breaking the previous record of nine in 1916. Six hurricanes hit the country, tying 1886 and 1985 for the most hurricane landfalls in a single season. Eight of the eleven named storms struck the Gulf Coast of the United States. Damage throughout the season totaled about $37 billion, including six hurricanes that inflicted at least $1 billion in damage; this was two more than the previous record of four in 2004 and 2005. Nearly the entire coastline from Texas to Maine was placed under some form of a watch or warning in relation to a tropical system, with only Florida's Jefferson and Wakulla counties being the exception. Only five counties along the East Coast or Gulf Coast of the United States did not experience tropical storm-force winds. Louisiana in particular was heavily impacted in 2020, with the state recording four landfalls – three hurricanes and one tropical storm – tying the record set in 2002. Outside the United States, a record 13 landfalls occurred. The two November hurricanes in Central America set back economic development in Honduras by 22 years.
Systems
Tropical Storm Arthur
The first tropical depression of the season formed on May 16 about 125 mi (200 km) east of Melbourne, Florida. It quickly intensified into Tropical Storm Arthur, reaching peak winds of 60 mph (95 km/h) and a minimum barometric pressure of 990 mbar (29 inHg) on May 19. A day later, Arthur interacted with a non-tropical front and became an extratropical cyclone. The low turned southeast before dissipating near Bermuda a day later. The precursor of Arthur dropped heavy rainfall over portions of the Bahamas, Cuba, and Florida, reaching 9.95 in (253 mm) near Marathon, Florida. The storm caused $112,000 in damage. Arthur later produced rainfall and storm surge flooding across North Carolina.
Tropical Storm Bertha
Tropical Storm Bertha developed off the northeast coast of Florida on May 27, reaching peak winds of 50 mph (80 km/h) and a central pressure of 1,005 mbar (29.7 inHg). That day, the storm made landfall near Isle of Palms, South Carolina, and quickly weakened into a tropical depression. Early on May 28, Bertha transitioned into an extratropical cyclone over western Virginia, before dissipating over the Northern Panhandle of West Virginia. In Florida, the precursor of Bertha brought up to 15 in (380 mm) of rainfall and localized flooding to the Miami area. One person drowned in South Carolina due to rip currents generated by the storm. Overall, Bertha left at least $133,000 in damage.