The 2023 Atlantic hurricane season was the fourth-most active Atlantic hurricane season on record with 20 named storms forming, tied with 1933. Among them, 7 became hurricanes, with 3 reaching major hurricane strength. The season also had an above‑normal accumulated cyclone energy (ACE) rating of 148.2, despite the presence of the 2023–24 El Niño event, which typically results in less activity, and had the most storms for an El Niño year on record, largely due to record-warm sea surface temperatures across the Atlantic. The season officially began on June 1 and ended on November 30. These dates, adopted by convention, historically describe the period in each year when most tropical cyclogenesis occurs in the Atlantic. However, the formation of subtropical or tropical cyclones is possible at any time of the year, as demonstrated by the formation of a subtropical storm on January 16, the earliest start of an Atlantic hurricane season since Hurricane Alex in January 2016. Because the system was operationally assessed as non-tropical by the National Hurricane Center (NHC) and designated after the fact, it went without a name.
June saw two tropical storms—Bret and Cindy—form in the tropical Atlantic (south of 23.5°N, east of 60°W) for the first time on record. The former made landfall on Saint Vincent. An unprecedented stretch of activity commenced in late August. Tropical Storm Harold struck southern Texas on August 22, and Hurricane Franklin made landfall in the Dominican Republic as a tropical storm the following day, with the latter reaching peak intensity as a high-end Category 4 hurricane and bringing tropical-storm-force winds to Bermuda. After briefly attaining Category 4 strength on August 30, Hurricane Idalia made landfall in Florida as a Category 3 hurricane. In early September, Hurricane Lee rapidly intensified into a Category 5 hurricane, then later made multiple landfalls in Atlantic Canada as a strong extratropical cyclone. Later that month, Tropical Storm Ophelia made landfall in North Carolina. In October, both Tropical Storm Philippe, the longest-lived tropical cyclone in the Atlantic this year, and Hurricane Tammy made landfall on Barbuda. Also that month, Tropical Depression Twenty‑One made landfall in Nicaragua. With Tammy's dissipation on October 28, the season effectively ended, as no tropical cyclones formed thereafter. The systems of this season collectively produced more than $4.22 billion (USD) in damage, and caused 19 fatalities.
Despite the above-normal activity this season, El Niño‑enhanced wind shear prevented many of the storms from significantly strengthening. Additionally, the El Niño event weakened the Bermuda High, allowing systems to curve northward or take more easterly tracks out to sea, as opposed to being pushed westward towards the continental United States, Mexico, or Central America. As a result, only a few systems impacted land or caused significant damage this season, with just three making landfall in the U.S. For the first time since the 2014 season, no names were retired this year by the World Meteorological Organization (WMO).
Seasonal forecasts
In advance of, and during, the 2023 Atlantic hurricane season, various forecasts of hurricane activity were issued by national meteorological services, scientific agencies, and research groups. Among them were forecasts from the United States National Oceanic and Atmospheric Administration (NOAA)'s Climate Prediction Center, Mexico's Servicio Meteorológico Nacional (SMN), Tropical Storm Risk (TSR), the United Kingdom's Met Office (UKMO), and Colorado State University (CSU). Forecasters track weekly and monthly changes in significant factors that help determine the number of tropical storms, hurricanes, and major hurricanes within a particular year. According to NOAA and CSU, the average Atlantic hurricane season between 1991 and 2020 contained roughly 14 tropical storms, seven hurricanes, three major hurricanes, and an accumulated cyclone energy (ACE) index of 74–126 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 typically categorizes a season as above-average, average, or below-average based on the cumulative ACE index, but the number of tropical storms, hurricanes, and major hurricanes within a hurricane season is sometimes also considered.
Pre-season forecasts
On December 6, 2022, TSR released the first early prediction for the 2023 Atlantic season, predicting a slightly below average year with 13 named storms, 6 hurricanes, and 3 major hurricanes. Their updated prediction on April 6, 2023, called for a similar number of hurricanes, but reduced the number of named storms and major hurricanes by one. The following day, the University of Arizona (UA) posted their forecast calling for a very active season featuring 19 named storms, 9 hurricanes, 5 major hurricanes, and an ACE index of 163 units. On April 13, CSU researchers released their prediction calling for 13 named storms, 6 hurricanes, 2 major hurricanes, and an ACE index of 100 units. On April 27, University of Missouri (MU) issued their predictions of 10 named storms, 4 between categories one and two, and 3 major hurricanes. On May 1, University of Pennsylvania (UPenn) released their forecast for 12 to 20 named storms. On May 4, SMN issued its forecast for the Atlantic basin, anticipating 10 to 16 named storms overall, with 3 to 7 hurricanes, and 2 to 4 major hurricanes. On May 25, NOAA announced its forecast, calling for 12 to 17 named storms, 5 to 9 hurricanes, and 1 to 4 major hurricanes, with a 40% chance of a near-normal season and 30% each for an above-average season and a below-average season. One day later, UKMO issued its forecast calling for an extremely active season, with 20 named storms, 11 hurricanes, 5 major hurricanes, and an ACE index of 222 units.
There was a wide range of conclusions among the groups making pre-season forecasts. With regard to number of hurricanes, projections ranged from 5 by SMN to 11 by UKMO. This reflected an uncertainty on the part of the various organizations about how the expected late-summer El Niño event and near record-warm sea surface temperatures would together impact tropical activity.
Mid-season forecasts
On June 1, CSU issued an updated forecast, now expecting a near-average season with 15 named storms, 7 hurricanes, 3 major hurricanes, and an ACE index of 125 units, due to a rise in main development region sea surface temperatures to near record-highs, which, they reasoned, could offset increased wind shear from the impending El Niño. On June 16, UA updated its seasonal prediction, which indicates a very active hurricane season, with 25 named storms, 12 hurricanes, 6 major hurricanes, and an ACE index of 260 units. On July 6, CSU issued an updated forecast increasing their numbers, predicting a very active season; they now expect 18 storms, 9 hurricanes, and 4 major hurricanes, with an ACE index of 160 units. The following day, TSR released the first seasonal prediction, predicting a slightly above average year with 17 named storms, 8 hurricanes, and 3 major hurricanes and an ACE index of 125. UKMO updated their forecast on August 1, slightly decreasing the number of tropical storms and hurricanes to 19 and 9, respectively, while increasing the number of major hurricanes from 5 to 6. On August 3, CSU issued their final prediction, with no changes to the amount of tropical storm, hurricanes, and major hurricanes. TSR's last forecast, published on August 8, only adjusted the number of major hurricanes from two to three. Citing record-warm sea surface temperatures, a warm phase of the Atlantic multidecadal oscillation, and El Niño, NOAA's second prediction, released on August 10, called for 14 to 21 tropical storms, 6 to 11 hurricanes, and 2 to 5 major hurricanes.
Seasonal summary
Background
Officially, the 2023 Atlantic hurricane season ran from June 1 to November 30. A total of 21 tropical cyclones formed, 20 of which intensified into nameable storms, ranking the season as the fourth-most active in terms of number of tropical or subtropical storms, tied with 1933. Of those, seven strengthened into a hurricane, with three systems reaching major hurricane intensity. Thus, the season was above-average compared to NOAA's 1991–2020 mean of fourteen named storms, while equaling the normal number of hurricanes and major hurricanes, seven and three, respectively. NOAA attributed the abnormally high number of named storms to record-warm sea surface temperatures across the Atlantic, mostly offsetting the effects of a strong El Niño event, which typically limits activity in the basin. In fact, the season had the most tropical or subtropical storms for a year with El Niño conditions present since records began. Meteorologists such as Jonathan Belles and Phil Klotzbach argued that El Niño impacted the season by significantly weakening and shifting the Bermuda high-pressure system eastward, causing several storms to recurve out to sea much farther east than usual or drift aimlessly over the central Atlantic, rather than being pushed westward towards the continental United States, Mexico, or Central America. Consequently, only three systems made landfall in the United States.
Few tropical cyclones in the Atlantic in 2023 left significant impacts. The most destructive storm, Idalia, caused 12 deaths and approximately $3.6 billion in damage in August despite making landfall in Florida at Category 3 hurricane intensity, due to crossing mostly rural areas. During the same month, Franklin rendered at least $90 million in damage and three deaths, all in the Dominican Republic, which it struck as a weak tropical storm. Although Lee remained offshore while a tropical cyclone, rough seas generated by the storm drowned four people, while the remnants resulted in about $50 million in damage, mostly in Maine and Atlantic Canada. In September, Ophelia caused approximately $450 million in damage along the East Coast of the United States. Overall, the storms of the 2023 season collectively inflicted more than $4.22 billion in damage and 19 fatalities.
This season's ACE index was approximately 148.2 units, roughly 21% above average. This number represents sum of the squares of the maximum sustained wind speed (knots) for all named storms while they are at least tropical storm intensity, divided by 10,000. Therefore, tropical depressions are not included.
In 2023, NOAA logged 468 flight hours for their Hurricane Hunter missions in the Atlantic. The aircraft deployed more than 1,400 scientific instruments and conducted 120 entries into the eye of a storm. NOAA launched several drones, including Black Swift drone for the first time into Tammy, both for obtaining observations and evaluating the efficiency of this method of collecting data. Additionally, NOAA used their aircraft to assist with emergency response to Idalia and Lee, conducting a combined 28 flight hours to obtain aerial imagery. The National Ocean Service, an agency of NOAA, surveyed just over 42 mi (68 km) of coastline, including identifying 29 potential marine obstructions, in the aftermath of Idalia.
Early activity
The 2023 Atlantic hurricane season commenced unexpectedly on January 16, when an unnamed subtropical storm formed off the northeastern U.S. coast then moved over Atlantic Canada. Operationally, the NHC considered the storm to be non-tropical, with minimal likelihood of transitioning into a subtropical or tropical cyclone. A few months later, however, following a post-storm evaluation of the system, it was redesignated as subtropical, but intentionally left unnamed. No additional tropical or subtropical activity occurred in the basin prior to the official start of the season on June 1. Tropical Depression Two formed on opening day in the Gulf of Mexico. It became the season's first named storm, Arlene, on June 2. Later that month, tropical storms Bret and Cindy formed, becoming the first instance of two Atlantic tropical cyclones active simultaneously in June since 1968. The two developed in the Main Development Region (MDR) from successive tropical waves coming off the coast of West Africa. Their formation also marked the first time on record that two tropical storms formed in the MDR during the month of June. Next, Subtropical Storm Don formed over the central Atlantic on July 14. A long-lived storm, it later became fully tropical and strengthened into the season's first hurricane as it meandered around the ocean far from land.
Peak to late activity
Following a lull in activity, tropical cyclogenesis increased to an unprecedented level in late August. Between August 19 and 21, four depressions formed, which quickly intensified into named storms: Emily, Franklin, Gert, and Harold. Emily formed in the eastern Atlantic, lasting only about 24 hours before dissipating. Franklin moved across the Dominican Republic as a tropical storm, before intensifying into a Category 4 hurricane in the western Atlantic. Gert became a remnant low on August 22, but regenerated into a tropical depression at the end of the month. Tropical Storm Harold affected south Texas and brought much needed rainfall to the region. Those four were followed by two more systems during last week of the month: Idalia and Jose. Idalia formed on August 26 in the northwestern Caribbean, intensified into a Category 4 hurricane, then made landfall in the Big Bend region of Florida at Category 3 strength. Tropical Storm Jose formed in the open Atlantic on August 29 and remained far from land.