2020 was regarded as the most active tropical cyclone year on record, documenting 106 named tropical systems. During the year, 143 tropical cyclones formed in bodies of water known as tropical cyclone basins. Of these, a record-high of 106, including three subtropical cyclones in the South Atlantic Ocean and three tropical-like cyclones in the Mediterranean, were named by various weather agencies when they attained maximum sustained winds of (though one storm was a crossover storm that received two names). The most intense storm of the year was Typhoon Goni, peaking with a pressure of . The deadliest storm of the year was Hurricane Eta which caused 175 fatalities and another 100+ to be missing in Central America and the US, while the costliest storm of the year was Hurricane Laura, with a damage cost around $19.1 billion in the Greater Antilles, The Bahamas, and the Gulf Coast of the United States.
2020 featured a very high amount of tropical cyclones forming in the year. It was dominated by a strong La Niña, that led to significant ramifications in tropical cyclone formations across the world. For instance, the most active basin of the year was the North Atlantic, which documented a record 30 named storms, the most storms ever recorded in the basin. This was only one of four known years where the North Atlantic was more active than the West Pacific, the others being 2005, 2010, and 2023. The West Pacific, in fact, had a below average season, with only 23 named storms forming. The Eastern Pacific similarly was below average, with 17 named storms, and the lowest hurricane count seen since 2010. The North Indian basin featured relatively average season, with 5 named storms, but became the costliest season in the basin’s history, due to the onslaught of Cyclone Amphan in early May. The Southern Hemisphere overall had relatively average activity throughout much of the year. The Australian region remained below average in activity because of positive IOD, while the South-West Indian Ocean had average activity. The South Pacific basin featured a slightly above-average season, and had Cyclones Harold and Yasa both attaining Category 5 intensity, and affecting a large swathe of the South Pacific. Two other Category 5 tropical cyclones formed globally, totaling to four which formed during 2020. The twenty four major tropical cyclones which formed throughout the year constituted an average amount. The accumulated cyclone energy (ACE) index for the 2020 (seven basins combined), as calculated by Colorado State University (CSU) was 599.1 units, which was below the 1981–2010 mean of 770.2 units.
Global atmospheric and hydrological conditions
As 2020 began, sea surface temperatures were above normal in the eastern Pacific Ocean near the equator, which had the potential to develop into El Niño conditions. On January 9, a group of climate scientists writing for ENSO Blog published their forecast for atmospheric conditions. They believed that there was a 60% chance that the environment would remain in neutral conditions related to the El Niño–Southern Oscillation (ENSO); this was based on the expectation that the above normal water temperatures would return to normal. By March, there was little evidence of increased rainfall near the equator. Trade winds were enhanced in the central and tropical Pacific Ocean, and water temperatures remained above normal. On April 9, ENSO Blog reaffirmed their belief that environmental conditions would remain neutral. However, the sea surface temperatures near the equatorial pacific began to cool well below average, indicating a developing La Niña. As a result, the ENSO Blog issued La Niña watch, stating a 50–55% chance of a strong La Niña. In September, NOAA confirmed that the environment shifted to a La Niña pattern, based on lower than normal water temperatures in the eastern Pacific Ocean near the equator. The ENSO Blog estimated a 75% chance that La Niña conditions would persist through the end of the year, in part due to a strengthening Walker circulation.
Meanwhile, in the Atlantic, sea surface temperatures were near normal in the early parts of the year. However, they began to warm up significantly that Spring, with the Caribbean, Gulf of Mexico and the Main Development Region all having well above-average sea surface temperatures. This was mainly due to the developing La Niña.
The COVID-19 pandemic disrupted the response to tropical cyclones during the year. In the South Pacific island nation of Vanuatu, COVID-19, travel and social distancing restrictions associated with the pandemic were lifted for those seeking safe houses and evacuation shelters during Cyclone Harold. When Typhoon Vongfong struck the Philippines in May, evacuation shelters were filled to half-capacity to comply with social distancing guidelines, requiring more evacuation centers to house refugees. As a result of the use of schools as quarantine facilities for COVID-19, some schools could not be used as evacuation shelters. When Cyclone Amphan was approaching India in May, shelter capacity in West Bengal was reduced from 500,000 people to 200,000 people due to social distancing restrictions. Movement restrictions in El Salvador were temporarily lifted to allow people to purchase supplies ahead of Tropical Storm Amanda.
Summary
North Atlantic Ocean
An average Atlantic hurricane season features 14 tropical storms, 7 hurricanes, and 3 major hurricanes, and features an Accumulated Cyclone Energy (ACE) count of 110. This is according to the new 30-year averages from 1991 to 2020. In 2020 in the North Atlantic basin, all of the statistics fell well above listed, featuring a record-breaking 30 tropical storms, 14 hurricanes, and 7 major hurricanes, with an ACE total of 182.
After fifteen years, the 2020 Atlantic hurricane season has surpassed record high activity in terms of named storms. The season produced thirty-one tropical cyclones, of which thirty developed into named storms; thirteen became hurricanes, and seven attained major hurricane status. The season's first cyclone developed on May 16, and activity was unprecedented after Arthur formed, with an additional off-season storm forming having been named Tropical Storm Bertha. In July, five individual storms (most notably Hurricane Isaias, which spawned a damaging tornado outbreak in the United States) formed and tied the record with 2005 as the most active July on record. The month of August also included Hurricanes Laura and Marco, which both impacted the United States and the former becoming the costliest of the year. Afterwards, a record-breaking ten storms developed in the month of September. Afterwards, October featured little relief with 3 hurricanes and 4 named storms forming all and all. The catastrophic season ended on November 18, after Hurricane Iota dissipated. Iota was also the most intense hurricane of the season with a minimum central pressure of 917 mbar. Iota was also the strongest storm in terms of wind speed, peaking with a strength of 155 mph or as a Category 4 hurricane on the Saffir–Simpson scale. Many records were broken throughout the season, including the extreme rate of tropical cyclone formations, the second time on record that the Greek naming system for named storms was used, and the strength of the storms which formed in the months of October and November.
The season was very destructive, causing an estimated $51.146 billion (2020 USD) in damage and more than four hundred fatalities. Most destruction was due to Laura, which caused about $19.1 billion (2020 USD) in damage and killed seventy people in Louisiana. Hurricane Eta in early November also caused $7 billion (2020 USD) in damage and was the deadliest storm of the season, causing over two hundred deaths as it crossed the vast majority of Central America and eventually made three more landfalls: one in Cuba, and two in Florida.
Eastern and Central Pacific Oceans
An average Pacific hurricane season features 15 tropical storms, 9 hurricanes, and 4 major hurricanes, and features an Accumulated Cyclone Energy (ACE) count of 132. In 2020 in the Eastern and Central Pacific basins, most of the statistics fell below the above list. The exception was the number of tropical storms, featuring 17, which was slightly above average for the basin.
The season as a whole, however, was below average. Featuring only seventeen tropical storms (sixteen received names), four hurricanes, and three major hurricanes, the 2020 Pacific hurricane season was the least active season in exactly a decade. Despite the inactivity, an unusual tropical depression formed on April 25 – the record earliest start to an Eastern Pacific hurricane season since reliable records began in 1966. The strongest storm in the basin this year was Hurricane Marie, which reached low-end Category 4 strength on the Saffir–Simpson scale and it did not impact land. Elsewhere, Tropical Storm Amanda was the costliest storm of the season after its El Salvador landfall. Hurricane Douglas caused minor damage to the Hawaiian Islands as it passed north as a Category 1, and Hurricane Genevieve nearly became the strongest landfalling system of the season, but failed to do so as it passed southwest of the Baja California Peninsula. The season concluded on November 19 with the dissipation of Tropical Storm Polo, which briefly existed for around 2 days prior.
Each individual storm generated very low ACE counts throughout the season, ending at a total of just 73 units. These statistics are typical of a La Niña that has been persisting since the beginning of the year. In addition, no storms formed in the Central Pacific Ocean this year – the first such occurrence since 2017.
Western Pacific Ocean
The average typhoon season lasts year-round, with the majority of the storms forming between May and October. An average Pacific typhoon season features 26 tropical storms, 16 typhoons, and 9 super typhoons (unofficial category). It also features an average Accumulated Cyclone Energy (ACE) count of approximately 294; the basin is typically the most active basin for tropical cyclone formation. For only the third time ever and the first in a decade, the 2020 Atlantic hurricane season surpassed the 2020 Pacific typhoon season in named storms, which had below-average statistics, especially in the count of super typhoons. This was only the third time ever that the typhoon season wasn't the most active season; two times (2005 and 2010) it was the Atlantic hurricane season, and the fourth (and only time the most active season wasn't in the Northern Hemisphere) being the 1973 Australian cyclone season.