During 2023, tropical cyclones formed in seven major bodies of water, commonly known as tropical cyclone basins. They were named by various weather agencies when they attained maximum sustained winds of . Throughout the year, a total of 115 systems formed, with 79 of them being named. The most intense storm of the year was Typhoon Mawar, which had a minimum pressure of . The deadliest tropical cyclone of the year was Storm Daniel, which killed at least 5,591 people in Libya, Greece, Turkey, and Bulgaria. Meanwhile, the costliest tropical cyclone was Typhoon Doksuri which caused at least $28.4 billion (USD) worth of damage in China, the Philippines and Taiwan, becoming the costliest on record outside the Atlantic Ocean basin. Among this year's systems, thirty became major tropical cyclones, of which nine intensified into Category 5 tropical cyclones on the Saffir–Simpson scale (SSHWS), the most since 2018. The accumulated cyclone energy (ACE) index for 2023 across all seven basins, as calculated by Colorado State University (CSU), was 857.4 units, which was above the 1991–2020 mean of 770.2 units.
The most active basin in the year was the North Atlantic Ocean, which had 20 named systems. The Eastern Pacific Ocean had an above-average and destructive season, with 17 named storms forming; 10 of those became hurricanes, of which 8 strengthened into major hurricanes – double the seasonal average. The Western Pacific Ocean had a total of 17 named storms, making it the second least active season in the basin, tying with 1998. The North Indian Ocean was unusually active, with six named storms forming, producing the second-most accumulated cyclone energy in this basin on record, only behind 2019. Activity across the southern hemisphere's three basins (South-West Indian, Australian, and South Pacific) was fairly significant, with the regions recording 17 named storms altogether, with the most intense Southern Hemisphere cyclone of the year, Cyclone Kevin in the South Pacific basin, peaking with a central pressure of 913 hPa (26.96 inHg).
Tropical cyclones were primarily monitored by ten warning centers across the world, which are designated as a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC) by the World Meteorological Organization (WMO). These ten centers are the National Hurricane Center (NHC) and the Central Pacific Hurricane Center (CPHC), Japan Meteorological Agency (JMA), Indian Meteorological Department (IMD), Météo-France (MFR), Indonesia's Meteorology, Climatology, and Geophysical Agency (BMKG), the Australian Bureau of Meteorology (BoM), Papua New Guinea's National Weather Service (PNGNWS), the Fiji Meteorological Service (FMS), and New Zealand's MetService. Unofficial, but still notable, warning centres include the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), the United States's Joint Typhoon Warning Center (JTWC), and the Brazilian Navy Hydrographic Center.
Global atmospheric and hydrological conditions
On February 9, the NOAA made a new ENSO forecast stating that the La Niña is still ongoing but will transition into an ENSO-Neutral soon. It says that there is around a 5% chance that the La Niña persists throughout March and around a 95% chance of an ENSO-Neutral in March. NOAA announced an El Nino later in the year.
Summary
North Atlantic Ocean
The season was the fourth-most active Atlantic hurricane season on record with 20 named storms, tied with 1933. Among them, 7 became hurricanes, with 3 reaching major hurricane strength. The season also had an abovenormal accumulated cyclone energy (ACE) rating of 146, despite the presence of El Niño, 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, 2023, and ended November 30. Nontherless, it unexpectedly commenced 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, however a post-storm evaluation of the system to determine its proper classification was conducted by a team of forecasters from the NHC and Ocean Prediction Center (OPC). As a result, it was re-designated as subtropical prior to the official start of the season. Tropical Storm Arlene began as a tropical depression on June 1, in the Gulf of Mexico, and became the season's first named storm on June 2. Later that month, when Tropical Storm Bret and Tropical Storm Cindy formed, there were two Atlantic tropical cyclones active simultaneously in June for the first time 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 have 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.
Following a lull in activity, tropical cyclogenesis picked up drastically in late August. Within a span of 39 hours during August 20–22, four tropical storms formed: Emily, Franklin, Gert, and Harold. This marked the fastest time four storms were named within the Atlantic basin, surpassing the previous mark of 48 hours, set in 1893 and matched in 1980. Emily formed in the eastern Atlantic, lasting only 24 hours before dissipating. Franklin moved across the Dominican Republic, before intensifying into a Category 4 hurricane in the western Atlantic. Gert became a remnant low on August 22, but regenerated into a tropical cyclone ten days later, on September 1. 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 31.
The quick pace of storm formation continued into September, the climatological peak of the hurricane season. On September 1, Tropical Storm Katia formed northwest of Cabo Verde in the far eastern Atlantic. After Gert and Katia dissipated, Tropical Storm Lee formed in the central tropical Atlantic on September 5. It became a hurricane a day later, then rapidly intensified to Category 5 strength, with its winds increasing by during the 24hour period ending at 06:00 UTC on September 8. This made Lee the fourthfastest intensifying Atlantic hurricane on record, behind only Milton, Felix and Wilma. Lee later made multiple landfalls in Atlantic Canada as an extratropical cyclone. Tropical Storm Margot formed next, and strengthened into the season's fifth hurricane on September 11. They were joined by Tropical Depression Fifteen, later Hurricane Nigel, which formed midway between the Lesser Antilles and Cabo Verde Islands on September 15. Nigel remained far from any land masses, and became extratropical on September 22. That same day, Tropical Storm Ophelia formed offshore of North Carolina. The storm moved inland the following morning at near-hurricane strength. Also on September 23, Tropical Storm Philippe formed in the eastern tropical Atlantic. Right behind Philippe came Tropical Storm Rina five days later. At that time, Philippe and Rina were approximately apart, which is close enough to influence each other's movement and development.
After a brief letup in activity, Tropical Storm Sean formed on October 11, in the eastern tropical Atlantic. Later, on October 18, Hurricane Tammy formed. It made landfall on Barbuda, the second system in three weeks to do so, in addition to Philippe. A few days later, short-lived Tropical Depression Twenty-One formed offshore Nicaragua, moved inland, and soon dissipated. The season effectively ended when Tammy dissipated on October 29. No tropical cyclones formed in the Atlantic in the month of November for the first time since 2018, though a disturbance over the Caribbean Sea was briefly designated as a potential tropical cyclone during the month, but it did not organize into a tropical cyclone.
Despite the above-normal activity this season, El Niñoenhanced wind shear prevented most storms from strengthening. The El Niño event also 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. The systems of this season collectively produced at least $3.09 billion (USD) in damage, and caused 16 fatalities.
Eastern and Central Pacific Ocean
Overall, 20 tropical cyclones formed, of which 17 reached tropical storm intensity and were named. A total of 10 of these storms became hurricanes, and eight became major hurricanes. The season was very active compared to the previous below-to-normal seasons since 2019. Despite this, no tropical cyclones formed in the Central Pacific for the fourth consecutive year. At least 66 fatalities were recorded and damage totaled US$16.87 billion, mostly due to Hurricane Otis which was the first Pacific hurricane to make landfall at Category 5 intensity, surpassing Hurricane Patricia as the strongest landfalling Pacific hurricane on record. The season's activity, east of 140°W, was reflected with an above-average cumulative accumulated cyclone energy (ACE) rating of 164, roughly 115% of the 30-year median. The season officially began on May 15 in the Eastern Pacific, and on June 1 in the Central Pacific; both ended officially on November 30. The above-average activity levels were largely attributed to the strong El Niño event, which brought anomalously high sea surface temperatures and low vertical wind shear to western parts of the basin.
The first several weeks of this Eastern Pacific hurricane season were quiet, as the first system, Hurricane Adrian, did not develop until June 27. Typically, the first named storm forms around June 10. Two days later, as Adrian moved out into the open Pacific, Hurricane Beatriz formed near and tracked parallel to the Mexican coast. Next came Hurricane Calvin, which formed off the southwestern coast of Mexico during the second week of July and became the first major hurricane of the season as it moved steadily west-northwestward toward Hawaii. Hurricane Dora ushered in August by rapidly intensifying to a Category 4 hurricane, while also tracking toward Hawaii. On August 11, Dora crossed the International Dateline to become only the second tropical cyclone on record to be at hurricane strength in the Eastern, Central and Western Pacific basins, the other being John in 1994. Additionally, Dora maintained Category 4 intensity longer than any Pacific hurricane on record.