During 2005, tropical cyclones formed within seven different tropical cyclone basins, located within various parts of the Atlantic, Pacific and Indian Oceans. During the year, a total of 141 systems formed with 94 of these developing further and were named by the responsible warning centre. The strongest tropical cyclone of the year was Hurricane Wilma, which was estimated to have a minimum barometric pressure of . 2005 was above-average in terms of the number of storms. The most active basin in the year was the North Atlantic, which documented 28 named systems.
The Western Pacific had a near-average season with 23 named storms. The Eastern Pacific hurricane season experienced an above-average number of tropical storm intensity systems, numbering 15. Activity across the southern hemisphere's three basins – South-West Indian, Australian, and South Pacific – was fairly significant, with the regions recording 23 named storms altogether, with the most intense Southern Hemisphere cyclone of the year, Cyclone Percy from the South Pacific Ocean basin peaking at and 900 millibars. Throughout the year, 28 Category 3 tropical cyclones formed, including eight Category 5 tropical cyclones in the year. The accumulated cyclone energy (ACE) index for the 2005 (seven basins combined), as calculated by Colorado State University was 899.6 units.
The deadliest tropical cyclone of the year was Hurricane Stan in the North Atlantic Ocean, which killed more than 1,600 people in Central America. Hurricane Katrina, also in the North Atlantic Ocean, was the costliest tropical cyclone of the season and all time (tied with Hurricane Harvey in 2017), causing more than $125billion in damage after striking the United States, especially New Orleans and its surrounding areas.
Global atmospheric and hydrological conditions
The 2005 tropical cyclone season was marked by record-breaking activity, particularly in the North Atlantic, which saw 28 named storms, 15 hurricanes, and 7 major hurricanes, including Hurricane Katrina. This was driven by unusually warm sea surface temperatures, low wind shear, and favorable atmospheric pressure patterns. Globally, the Western Pacific and Indian Oceans experienced near-average activity, while the Eastern Pacific was slightly below average due to cooler waters. The season was shaped by neutral ENSO conditions, warm ocean temperatures, and high ocean heat content, contributing to cyclone intensity in several regions.
A strong La Niña existed throughout 2005.
Summary
North Atlantic Ocean
The activity was the most active Atlantic hurricane season in recorded history at the time, shattering numerous records, with 31 tropical or subtropical cyclones recorded. The United States National Hurricane Center named 27 storms, exhausting the annual pre-designated list and resulting in the usage of six Greek letter names. A record 15 storms attained hurricane status, with maximum sustained winds 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 season's impact was widespread and catastrophic. Its storms caused an estimated 3,468 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 (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 in July inflicted heavy damage to Cuba. Hurricane Stan 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 – formed in late December and lasted until January 6, 2006.
Eastern Pacific Ocean
The activity continued the trend of generally below-average activity that began a decade prior. The season's first tropical cyclone, Adrian, developed on May 17 and reached its peak as a Category 1 hurricane. Named storms are infrequent in May, with one tropical storm every two years and a hurricane once every four years. At the time, Adrian was the fourth earliest tropical cyclone to form in the eastern Pacific since reliable record-keeping began in 1971. Activity throughout the remainder of the season was far less notable, with 16 tropical cyclones, 15 named storms, 7 hurricanes, and 2 major hurricanes. The long-term 1971–2004 average suggests an average season to feature 15 named storms, 9 hurricanes, and 4 major hurricanes. October, in particular, was notably quiet, with the formation of only one tropical depression; only three other seasons, 1989, 1995, and 1996, ended the month without the designation of a named storm.
Western Pacific Ocean
Although the season was quiet, some typhoons caused extensive damages in many places, especially in China where eight typhoons struck the country. First, Typhoon Haitang became the strongest storm in the basin this year and caused about $1.1 billion in damages in Taiwan and China in mid July. In August, Typhoon Matsa made landfall in Eastern China and caused about $2.23 billion in damages. Later that same month, two powerful typhoons made landfall, causing extreme damage and some casualties.
Similar to Haitang, Typhoon Longwang made landfall in Taiwan and China at a strong intensity causing damages. The season also marked the first time the Atlantic hurricane season was more active than the Pacific typhoon season (the others being 2010 and 2020). However, the 2005 Atlantic hurricane season featured record high activity while the Pacific typhoon season featured near average activity.
North Indian Ocean
There were a total of 12 depressions during the year, three less than normal, although the highest since 1992. The IMD named four cyclonic storms, a process they initiated in 2004, which was also below normal. No systems strengthened beyond cyclonic storm status. The season was the sixth in a row with below normal activity, based on the seasonal accumulated cyclone energy. Storms generally develop when the monsoon trough is located over tropical waters, with a peak from May to June and another peak in November. The monsoon developed 11 distinct low-pressure areas by the end of September, including five monsoon depressions, and the monsoon season was more active than usual.
Systems January
January was above average featuring thirteen tropical cyclones, of which ten of them being named. The month started off with a tropical low which was short lived in the Mozambique Channel. The month's first named storm Cyclone Sally formed on the 7th in the Australian basin, however it dissipated two days later. The South-West Indian Ocean basin also had two notable storms Cyclone Ernest and Tropical Storm Felapi which both impacted Madagascar. The North Indian Ocean had an early start with a depression and Cyclone Hibaru forming. The Northwest Pacific basin also had an early start with Tropical Storm Kulap forming near the Caroline Islands. + Tropical cyclones formed in January 2005 Storm name Dates active Max windmph Pressure(hPa) Areas affected Damage(USD) Deaths Refs07January 4–5Mozambique, MadagascarNoneNoneSallyJanuary 7–995 (60)985NoneNoneNone01BJanuary 8–1055 (35)1000NoneNoneNoneKerryJanuary 8–14140 (90)955 NoneNoneNone10SJanuary 11–1755 (35)998NoneNoneNoneHibaruJanuary 13–1765 (40)1000NoneNoneNoneKulapJanuary 13–1995 (50)985Caroline IslandsNoneNoneErnestJanuary 16–23165 (105)950MadagascarMinimal78DarenJanuary 17–2395 (60)986NoneNoneNoneTimJanuary 23–2585 (50)990NoneNoneNoneFelapiJanuary 26 – February 365 (40)995MadagascarNoneNoneLolaJanuary 26–February 275 (45)990NoneNoneNoneGerardJanuary 29 – February 5115 (70)973NoneNoneNone
February
February was slightly below-average featuring nine tropical cyclones, of which seven were named. The Australian region featured Cyclone Harvey and Tropical Low Vivienne. Harvey formed in the Gulf of Carpentaria before making landfall on Queensland and the Northern Territory while Vivienne caused minor oil and gas disruptions in the Timor Sea. The Southern Pacific basin featured seven cyclones of which three of them became Category 5 cyclones. Cyclones Meena, Olaf, Nancy, and Percy all affected the Cook Islands with Percy becoming the strongest storm of the month. + Tropical cyclones formed in February 2005 Storm name Dates active Max windkm/h (mph) Pressure(hPa) Areas affected Damage(USD) Deaths RefsMeenaFebruary 1–8215 (130)915Cook Islands$20 millionNoneHarveyFebruary 3–8140 (90)967Northern Territory, Queensland$797 000None VivienneFebruary 4–965 (40)990NoneNoneNoneOlafFebruary 10–20215 (130)915Samoan Islands, Cook Islands$10 millionNone NancyFebruary 10–17175 (110)935Samoan Islands, Cook IslandsNoneNonePercyFebruary 24 – March 5230 (145)900Tokelau, Samoan Islands, Cook Islands$25 millionNone 11FFebruary 26–2755 (35)998French PolynesiaNoneNoneRaeFebruary 27 – March 675 (45)990NoneNoneNone13FFebruary 27 – March 4Not specified1001NoneNoneNone
March
March was very inactive, featuring five tropical cyclones with all of them being named. The month started off with Cyclone Ingrid, which formed north of the Gulf of Carpentaria. Ingril was a erratic cyclone which effected much of Northern Australia as a Category 4 tropical storm. The storm made landfall on the town of Nhulunbuy as a Category 5 on the Australian scale. It then made a slow approach on Kimberley before dissipating. While Ingril was a Category 5 cyclone, another storm named Cyclone Willy formed northwest of Australia. Willy only caused minor oil distruption in the Timor Sea but had no effect on land.
The Western Pacific basin featured its second storm Tropical Storm Roke. Roke struck the Philippines as a minimal typhoon killing 7 people. The South-West Indian Ocean featured two storms named Hennie and Isang. Hennie caused minor damage on Mauritius, and Réunion before accelerating towards the southeastern Indian Ocean. Isang on the other hand took a similar route with Hennie but had no effect on land. + Tropical cyclones formed in March 2005 Storm name Dates active Max windkm/h (mph) Pressure(hPa) Areas affected Damage(USD) Deaths RefsIngridMarch 4–16230 (140)924Papua New Guinea, Northern Australia$14.4 million5 WillyMarch 8–14140 (85)960NoneNoneNoneRoke (Auring)March 13–19100 (65)980Caroline Islands, Philippines$166 thousand7 HennieMarch 19–26100 (65)978Mauritius, RéunionNoneNoneIsangMarch 29 – April 6115 (75)970NoneNoneNone
April
April was average featuring eight tropical cyclones, of which three were named. The month started off with Cyclone Adeline-Juliet which became the strongest storm of the month. The storm was first noted near the Cocos Islands and was upgraded into Tropical Storm Adeline. It then entered the South-West Indian Ocean basin where the storm was renamed Juliet. It then intensified into an Intense Tropical Cyclone until the system weakened and became extratropical. Later 11U formed over the Arafura Sea and made landfall on Papua New Guinea.
11U was the last storm of the 2004–05 Australian region cyclone season. The second named storm was Cyclone Sheila which formed over Fiji. The storm then curved away from Fiji where the storm dissipated shortly after being named. The third named storm was Typhoon Sonca which formed in the Western Pacific. It then intensified into a Category 4 typhoon. Despite its strength, the typhoon stayed at sea and dissipated. The other unnamed storms were rather weak and short-lived as not much information is known.