The 2005 Atlantic hurricane season was the most active Atlantic hurricane season in history, until the record was broken 15 years later in 2020. The season broke numerous records at the time, with 28

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

or subtropical storms recorded. The United States

National Hurricane Center The National Hurricane Center (NHC) is the division of the United States' NOAA/ National Weather Service responsible for tracking and predicting tropical weather systems between the Prime Meridian and the 140th meridian west poleward to the 3 ...

named 27 storms, exhausting the annual pre-designated list and resulting in the usage of six

Greek letter The Greek alphabet has been used to write the Greek language since the late 9th or early 8th century BCE. It is derived from the earlier Phoenician alphabet, and was the earliest known alphabetic script to have distinct letters for vowels as ...

names, and also identified an additional unnamed storm during a post-season re-analysis. A record 15 storms attained hurricane status, with

maximum sustained winds The maximum sustained wind associated with a tropical cyclone is a common indicator of the intensity of the storm. Within a mature tropical cyclone, it is found within the eyewall at a distance defined as the radius of maximum wind, or RMW. U ...

of at least 74 mph (119 km/h); of those, a record seven became major hurricanes, which are a Category 3 or higher on the

Saffir–Simpson scale The Saffir–Simpson hurricane wind scale (SSHWS) classifies hurricanes—which in the Western Hemisphere are tropical cyclones that exceed the intensities of tropical depressions and tropical storms—into five categories distinguishe ...

. Four storms of this season became Category 5 hurricanes, the highest ranking on the scale. The four Category 5 hurricanes that developed during the season were:

Emily Emily may refer to: * Emily (given name), including a list of people with the name Music * Emily (1964 song), "Emily" (1964 song), title song by Johnny Mandel and Johnny Mercer to the film ''The Americanization of Emily'' * Emily (Dave Koz son ...

, Katrina, Rita, and Wilma. In July, Emily reached peak intensity in the

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

, becoming the first Category 5 hurricane of the season, later weakening and striking Mexico twice. In August, Katrina reached peak winds in the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United S ...

but weakened by the time it struck the U.S. states of

Louisiana Louisiana , group=pronunciation (French: ''La Louisiane'') is a U.S. state, state in the Deep South and South Central United States, South Central regions of the United States. It is the List of U.S. states and territories by area, 20th-smal ...

and

Mississippi Mississippi () is a state in the Southeastern region of the United States, bordered to the north by Tennessee; to the east by Alabama; to the south by the Gulf of Mexico; to the southwest by Louisiana; and to the northwest by Arkansas. Mis ...

. The most devastating effects of the season were felt on the Gulf Coast of the United States, where Katrina's

storm surge A storm surge, storm flood, tidal surge, or storm tide is a coastal flood or tsunami-like phenomenon of rising water commonly associated with low-pressure weather systems, such as cyclones. It is measured as the rise in water level above the ...

crippled

New Orleans, Louisiana New Orleans ( , ,New Orleans

costliest U.S. hurricane, leaving $125 billion in damage and 1,836 deaths. Rita followed in September, reaching peak intensity in the Gulf of Mexico before weakening and hitting near the border of

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

and Louisiana. The season's strongest hurricane, Wilma, became the most intense Atlantic hurricane on record, as measured by

barometric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibar ...

. Lasting for ten days in October, Wilma moved over

Cozumel Cozumel (; yua, Kùutsmil) is an island and municipality in the Caribbean Sea off the eastern coast of Mexico's Yucatán Peninsula, opposite Playa del Carmen. It is separated from the mainland by the Cozumel Channel and is close to the Yucatán ...

, the

Yucatán Peninsula The Yucatán Peninsula (, also , ; es, Península de Yucatán ) is a large peninsula in southeastern Mexico and adjacent portions of Belize and Guatemala. The peninsula extends towards the northeast, separating the Gulf of Mexico to the north ...

, and

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, a ...

, causing $19 billion in damage and 48 deaths. The season's impact was widespread and catastrophic. Its storms caused an estimated 3,912 deaths and approximately $171.7 billion in damage. It was the costliest season on record at the time, until its record was surpassed 12 years later. It also produced the second-highest

accumulated cyclone energy Accumulated cyclone energy (ACE) is a metric used by various agencies to express the energy released by a tropical cyclone during its lifetime. It is calculating by summing the square of a tropical cyclone's maximum sustained winds, measured ever ...

(ACE) in the Atlantic basin, surpassed only by the 1933 season. The season officially began on June 1, 2005, and the first storm – Arlene – developed on June 8.

Hurricane Dennis Hurricane Dennis was an early-forming major hurricane in the Caribbean and Gulf of Mexico during the record-breaking 2005 Atlantic hurricane season. Dennis was the fourth named storm, second hurricane, and first major hurricane of the season. ...

in July inflicted heavy damage to Cuba.

Hurricane Stan Hurricane Stan was a relatively weak but deadly tropical cyclone that affected areas of Central America and Mexico in early October 2005. The eighteenth named storm and eleventh hurricane of the 2005 Atlantic hurricane season, Stan formed from ...

in October was part of a broader weather system that killed 1,668 people and caused $3.96 billion in damage to eastern Mexico and Central America, with Guatemala hit the hardest. The final storm –

Zeta Zeta (, ; uppercase Ζ, lowercase ζ; grc, ζῆτα, el, ζήτα, label=Demotic Greek, classical or ''zē̂ta''; ''zíta'') is the sixth letter of the Greek alphabet. In the system of Greek numerals, it has a value of 7. It was derived fr ...

– formed in late December and lasted until January 6, 2006.

Seasonal forecasts

Ahead of the formal start of the season, various groups issued forecasts for the number of named storms, hurricanes, and major hurricanes in the upcoming season, including Colorado State University (CSU), the Cuban Institute of Meteorology (InsMet), Tropical Storm Risk (TSR), and the United States

National Oceanic and Atmospheric Administration The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditi ...

(NOAA). Some forecasts predicted how many tropical cyclones would affect a particular country or territory.

Pre-season forecasts

The first of these forecasts was issued by CSU, which predicted on December 5, 2004 that the season would be above average and feature 11 named storms, 6 hurricanes and 3 intense hurricanes. They also noted that the Caribbean and the entire United States coastline faced an increased risk of a major hurricane making landfall. TSR issued its first forecast a few days later and predicted that the season would feature 9.6 tropical storms, 5.7 hurricanes, 3.3 major hurricanes, and predicted that the

(ACE) rating would be 145. During January 2005, TSR increased its forecast to 13.9 tropical storms, 7.8 hurricanes, 3.6 major hurricanes, and predicted that the ACE rating would be 157. CSU issued its first updated forecast on April 1, increasing their prediction to 13 tropical storms, 7 hurricanes, and 3 major hurricanes, with a continued risk of a major hurricane landfall in the Caribbean or United States. The increase was based on the Atlantic continuing to warm and a strong belief that El Niño conditions would not persist into the hurricane season. On May 2, the Cuban Institute of Meteorology (InsMet) issued their seasonal forecast, which predicted that the season would feature 13 tropical storms and 7 hurricanes. This was followed on May 16 by NOAA, who predicted a 70% chance of above normal activity, with 12–15 tropical storms, 7–9 hurricanes, and 3–5 major hurricanes. CSU issued its second forecast update on May 31, revising its forecast to 15 named storms, 8 hurricanes and 4 major hurricanes; by this point, the group believed El Niño conditions were unlikely.

Midseason outlooks

In their July forecast update, TSR anticipated that the season would be exceptionally active and well above average; the group increased their forecast to 15.3 tropical storms, 8.8 hurricanes, and 4.1 major hurricanes, with an ACE rating of 190. By the end of July, seven tropical storms and two major hurricanes had developed within the basin, which prompted CSU, InsMet, NOAA and TSR to significantly increase their seasonal forecasts at the start of August. In their August 5 update, CSU predicted that 13 more storms would form, with seven more hurricanes and three more major hurricanes. At the start of September, CSU updated their forecasts and predicted that eight more storms would form, with six more hurricanes and three major hurricanes. By the end of September, 17 named storms had developed, of which nine had developed into hurricanes and four had become major hurricanes. Within their final update for the year, CSU predicted that October would feature three named storms, two hurricanes and one major hurricane.

Seasonal summary

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With 28 storms (27 named storms and one unnamed), the 2005 Atlantic hurricane season set a new single-year record for most storms, surpassing the total of 20 from

1933 Events January * January 11 – Sir Charles Kingsford Smith makes the first commercial flight between Australia and New Zealand. * January 17 – The United States Congress votes in favour of Philippines independence, against the wis ...

. This record stood until surpassed by the 2020 season, which had 30 storms. A total of 7 named storms formed before August 1, which exceeded the record of 5 set in

1997 File:1997 Events Collage.png, From left, clockwise: The movie set of ''Titanic'', the highest-grossing movie in history at the time; ''Harry Potter and the Philosopher's Stone'', is published; Comet Hale-Bopp passes by Earth and becomes one of ...

; this record stood until 2020. The fourth named storm developed at a then-record early date, surpassed in

2012 File:2012 Events Collage V3.png, From left, clockwise: The passenger cruise ship Costa Concordia lies capsized after the Costa Concordia disaster; Damage to Casino Pier in Seaside Heights, New Jersey as a result of Hurricane Sandy; People gather ...

. The fifth though eleventh and the thirteenth and onward named storms developed at then-record early dates that were later surpassed in 2020. Further, the months of July and November set records for number of named storms, with 5 and 3, respectively. The 2005 season featured 15 hurricanes, surpassing the previous record of 12, set in

1969 This year is notable for Apollo 11's first landing on the moon. Events January * January 4 – The Government of Spain hands over Ifni to Morocco. * January 5 ** Ariana Afghan Airlines Flight 701 crashes into a house on its approach to ...

. Of the 15 hurricanes, 5 formed in September, with the season becoming only the sixth to feature 5 in that month. The 2005 season also featured a record seven major hurricanes, one more than the previous record, set in

1926 Events January * January 3 – Theodoros Pangalos (general), Theodoros Pangalos declares himself dictator in Greece. * January 8 **Abdul-Aziz ibn Saud is crowned King of Kingdom of Hejaz, Hejaz. ** Bảo Đại, Crown Prince Nguyễn P ...

, 1933,

1950 Events January * January 1 – The International Police Association (IPA) – the largest police organization in the world – is formed. * January 5 – Sverdlovsk plane crash: ''Aeroflot'' Lisunov Li-2 crashes in a snowstorm. All 19 ...

1996 File:1996 Events Collage.png, From left, clockwise: A bomb explodes at Centennial Olympic Park in Atlanta, set off by a radical anti-abortionist; The center fuel tank explodes on TWA Flight 800, causing the plane to crash and killing everyone on b ...

, and

2004 2004 was designated as an International Year of Rice by the United Nations, and the International Year to Commemorate the Struggle Against Slavery and its Abolition (by UNESCO). Events January * January 3 – Flash Airlines Flight 60 ...

. The four Category 5 hurricanes were also a record. The season's activity was reflected with an ACE rating of 250, the second-highest value on record in the Atlantic basin, after the 1933 season. The extremely active 2005 hurricane season was a continuation of an extended sequence of active years for tropical activity in the Atlantic. Tropical cyclone activity in the Atlantic Ocean between

1995 File:1995 Events Collage V2.png, From left, clockwise: O.J. Simpson is acquitted of the murders of Nicole Brown Simpson and Ronald Goldman from the year prior in "The Trial of the Century" in the United States; The Great Hanshin earthquake strike ...

and

was more active than any other decade in reliable record. With the exception of two years in which

El Niño El Niño (; ; ) is the warm phase of the El Niño–Southern Oscillation (ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific (approximately between the International Date ...

conditions were prevalent (

and

2002 File:2002 Events Collage.png, From left, clockwise: The 2002 Winter Olympics are held in Salt Lake City; Queen Elizabeth The Queen Mother and her daughter Princess Margaret, Countess of Snowdon die; East Timor gains independence from Indonesia and ...

), all hurricane seasons were individually above average. This was associated with an active phase of the Atlantic multidecadal oscillation (AMO), with a similar period of elevated tropical activity occurring between 1950 and 1969. The anomalously frequent formation of tropical storms and hurricanes reflected the emergence of unusually warm

sea surface temperature Sea surface temperature (SST), or ocean surface temperature, is the ocean temperature close to the surface. The exact meaning of ''surface'' varies according to the measurement method used, but it is between and below the sea surface. Air ma ...

s across the

tropical Atlantic The Tropical Atlantic realm is one of twelve marine realms that cover the world's coastal seas and continental shelves. The Tropical Atlantic covers both sides of the Atlantic. In the western Atlantic, it extends from Bermuda, southern Florida, ...

. The

Climate Prediction Center The Climate Prediction Center (CPC) is a United States federal agency that is one of the National Centers for Environmental Prediction, which are a part of the National Oceanic and Atmospheric Administration's National Weather Service. CPC is he ...

(CPC) predicted in May 2005 that the conditions associated with this active multi-decadal signal would continue into the 2005 hurricane season, providing favorable conditions for

tropical cyclogenesis Tropical cyclogenesis is the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which temperate cyclogenesis occurs. Tropi ...

in the tropical Atlantic.

Record activity

Chylek and Lesins (2008) determined that the likelihood of a season generating as much tropical activity as 2005 was less than 1 percent. The consecutive occurrence of hurricane seasons as active as 2004 and 2005 in the Atlantic was unprecedented. While environmental conditions favorable for the development of tropical cyclones were analogous to other active seasons, they were more pronounced and encompassed larger areas in 2005. The CPC determined that this environmental enhancement was primarily driven by four factors: the Atlantic multidecadal oscillation, the reduction of

atmospheric convection Atmospheric convection is the result of a parcel-environment instability, or temperature difference layer in the atmosphere. Different lapse rates within dry and moist air masses lead to instability. Mixing of air during the day which expands the ...

in the tropical Pacific, record-high sea surface temperatures in the tropical Atlantic and Caribbean, and conducive wind and pressure patterns across the western Caribbean and

. The multidecadal oscillation increased the potency of conducive environmental factors for tropical development, including the increased strength of

subtropical ridge The horse latitudes are the latitudes about 30 degrees north and south of the Equator. They are characterized by sunny skies, calm winds, and very little precipitation. They are also known as subtropical ridges, or highs. It is a high-pressu ...

s in the northern and southern Atlantic and the eastern Pacific. This amplified the African easterly jet and enhanced upper-level easterlies, attenuating

wind shear Wind shear (or windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizon ...

detrimental to tropical cyclogenesis across the central tropical Atlantic and the Caribbean. Frequent lulls in convection over the tropical Pacific also contributed to the strength of these ridges, focusing hurricane activity in the Atlantic. Most of the tropical storms and all major hurricanes in the Atlantic in 2005 formed when a lack of convection was present near the

International Dateline The International Date Line (IDL) is an internationally accepted demarcation on the surface of Earth, running between the South and North Poles and serving as the boundary between one calendar day and the next. It passes through the Pacific ...

, while a brief uptick in storms near the International Dateline led to a lull in tropical cyclogenesis in the Atlantic for the first half of August. The Gulf of Mexico saw record levels of tropical activity in 2005, with 11 named storms entering the basin. The unusual activity was attributed to a persistent

high pressure area A high-pressure area, high, or anticyclone, is an area near the surface of a planet where the atmospheric pressure is greater than the pressure in the surrounding regions. Highs are middle-scale meteorological features that result from interpl ...

over the

Southeastern United States The Southeastern United States, also referred to as the American Southeast or simply the Southeast, is a geographical region of the United States. It is located broadly on the eastern portion of the southern United States and the southern po ...

, the northeastward displacement and amplification of the Intertropical Convergence Zone (ITCZ) over the eastern Pacific, and above average sea surface temperatures in the Gulf of Mexico. These factors reduced vertical wind shear and favored cyclonic flow, creating an environment highly supportive of tropical development. The high pressure area also steered incoming storms into the Gulf of Mexico. In addition, the

El Niño–Southern Oscillation El Niño–Southern Oscillation (ENSO) is an irregular periodic variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean, affecting the climate of much of the tropics and subtropics. The warming phase of the sea te ...

(ENSO) was in a neutral phase, lowering the likelihood of storms making

landfall Landfall is the event of a storm moving over land after being over water. More broadly, and in relation to human travel, it refers to 'the first land that is reached or seen at the end of a journey across the sea or through the air, or the fact ...

on the

East Coast of the United States The East Coast of the United States, also known as the Eastern Seaboard, the Atlantic Coast, and the Atlantic Seaboard, is the coastline along which the Eastern United States meets the North Atlantic Ocean. The eastern seaboard contains the ...

and leading to a concentration of impacts farther west. This focusing mechanism led to a complementary reduction in storms

developing Development or developing may refer to: Arts *Development hell, when a project is stuck in development *Filmmaking, development phase, including finance and budgeting *Development (music), the process thematic material is reshaped * Photograph ...

close to

Cape Verde , national_anthem = () , official_languages = Portuguese , national_languages = Cape Verdean Creole , capital = Praia , coordinates = , largest_city = capital , demonym ...

. During the peak of the 2005 season, the