In the Indian Ocean north of the equator, tropical cyclones can form throughout the year on either side of the Indian subcontinent, although most frequently between April and June, and between October and December.
Tropical cyclones are ranked on one of five tropical cyclone intensity scales, according to their maximum sustained winds and which tropical cyclone basins they are located in. Only a few classifications are used officially by the meteorological agencies monitoring the tropical cyclones, but other scales also exist, such as accumulated cyclone energy, the Power Dissipation Index, the Integrated Kinetic Energy Index, and the Hurricane Severity Index.
Traditionally, areas of tropical cyclone formation are divided into seven basins. These include the north Atlantic Ocean, the eastern and western parts of the northern Pacific Ocean, the southwestern Pacific, the southwestern and southeastern Indian Oceans, and the northern Indian Ocean. The western Pacific is the most active and the north Indian the least active. An average of 86 tropical cyclones of tropical storm intensity form annually worldwide, with 47 reaching hurricane/typhoon strength, and 20 becoming intense tropical cyclones, super typhoons, or major hurricanes.
In the south-west Indian Ocean, tropical cyclones form south of the equator and west of 90° E to the coast of Africa.
The 1986–87 South-West Indian Ocean cyclone season was below average due to an ongoing El Niño and a weak monsoon that suppressed convection and storms. There were only five named storms tracked by the Météo-France office (MFR) on Réunion. The United States-based Joint Typhoon Warning Center (JTWC) followed four other storms in the basin, which is the waters of the Indian Ocean south of the equator and west of 90° E to the coast of Africa. The JTWC tracked a storm on August 1 in the northeastern portion of the basin, unusual for the time of year. The first named storm was Severe Tropical Storm Alinina, which originated from the Intertropical Convergence Zone east of Madagascar in the middle of January. However, there was an unnamed tropical depression that produced heavy rainfall in Réunion and Madagascar, causing two deaths in the latter country.
During 2010, 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 111 tropical cyclones developed, with 64 of them being named by either a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC). The most active basin was the North Atlantic, which documented 19 named systems, while the North Indian Ocean, despite only amounting to five named systems, was its basin's most active since 1998. Conversely, both the West Pacific typhoon and East Pacific hurricane seasons experienced the fewest cyclones reaching tropical storm intensity in recorded history, numbering 14 and 8, respectively. Activity across the southern hemisphere's three basins—South-West Indian, Australian, and South Pacific—was spread evenly, with each region recording 7 named storms apiece. The southern hemisphere's strongest tropical cyclone was Cyclone Edzani, which bottomed out with a barometric pressure of 910 mbar in the South-West Indian Ocean. Nineteen Category 3 tropical cyclones formed, including four Category 5 tropical cyclones in the year. The accumulated cyclone energy (ACE) index for the 2010, as calculated by Colorado State University was 573.8 units.
Throughout 2006, 133 tropical cyclones formed in seven bodies of water known as tropical cyclone basins. Of these, 80 have been named, including two tropical cyclones in the South Atlantic Ocean, and a tropical cyclone in the Mediterranean Sea, by various weather agencies when they attained maximum sustained winds of 65 km/h (40 mph). The strongest storms of the year were Typhoon Yagi in the Western Pacific, and Cyclone Glenda of the Australian region. The deadliest and costliest storms of the year were a series of five typhoons that struck the Philippines and China; Chanchu, Bilis, Saomai, Xangsane, and Durian, with most of the damage being caused by Durian of November. So far, 27 Category 3 tropical cyclones formed, including five Category 5 tropical cyclones in the year. The accumulated cyclone energy (ACE) index for the 2006, as calculated by Colorado State University was 761 units.
The 1993–94 South-West Indian Ocean cyclone season was the most active season in the basin since the start of reliable satellite coverage in 1967, until the record was surpassed 25 years later in the 2018–19 South-West Indian Ocean cyclone season. Activity lasted from mid-November, when Moderate Tropical Storm Alexina formed, until mid-April, when Tropical Cyclone Odille became extratropical. Four tropical cyclones – Daisy, Geralda, Litanne, and Nadia – struck eastern Madagascar, of which Geralda was the costliest and deadliest. With gusts as strong as 350 km/h (215 mph) accompanied by heavy rainfall, Geralda destroyed more than 40,000 homes and left 356,000 people homeless. Geralda killed 231 people and caused more than $10 million in damage. Cyclone Nadia was the second deadliest cyclone, having killed 12 people in northern Madagascar and later severely damaging portions of northeastern Mozambique, killing about 240 people and leaving $20 million in damage in the latter country. In February, Cyclone Hollanda struck Mauritius near peak intensity, causing $135 million in damage and two deaths.
During 2018, 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 151 tropical cyclones had formed this year to date. 102 tropical cyclones were named by either a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC).
During 2017 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 146 tropical cyclones had formed. 88 tropical cyclones had been named by either a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC). The strongest and deadliest tropical cyclone was Hurricane Maria with a minimum barometric pressure of 908 mbar and killing 3,000 people in Puerto Rico and Dominica. The costliest tropical cyclone of the year was Hurricane Harvey in the Atlantic, which struck Houston metropolitan area in August causing US$125 billion in damage, tying with Hurricane Katrina as the costliest tropical cyclone worldwide.
During 2015, tropical cyclones formed in seven major bodies of water, commonly known as tropical cyclone basins. Tropical cyclones will be assigned names by various weather agencies if they attain maximum sustained winds of 35 knots. During the year, one hundred thirty-four systems have formed and ninety-two were named. The most intense storm of the year was Hurricane Patricia, with maximum 1-minute sustained wind speeds of 345 km/h (215 mph) and a minimum pressure of 872 hPa (25.75 inHg). The deadliest tropical cyclone was Cyclone Komen, which caused 280 fatalities in Southeast India and Bangladesh, while the costliest was Typhoon Mujigae, which caused an estimated $4.25 billion USD in damage after striking China. Forty Category 3 tropical cyclones formed, including nine Category 5 tropical cyclones in the year. The accumulated cyclone energy (ACE) index for the 2015, as calculated by Colorado State University (CSU) was 1047 units.
During 2019, 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 142 systems formed, with 100 of these developing further and being named by the responsible warning centre. The strongest tropical cyclone of the year was Typhoon Halong, with a minimum barometric pressure of 905 hPa (26.72 inHg). Cyclone Idai became the deadliest tropical cyclone of the year, after killing at least 1,303 people in Mozambique, Malawi, Zimbabwe, and Madagascar. The costliest tropical cyclone of the year was Typhoon Hagibis, which caused more than $15 billion in damage after striking Japan.
During 2014, 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 117 tropical cyclones had formed this year to date. 79 tropical cyclones had been named by either a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC). The most active basin in 2014 was the Western Pacific, which documented 23 named systems, while the Eastern Pacific, despite only amounting to 22 named systems, was its basin's most active since 1992. Conversely, both the North Atlantic hurricane and North Indian Ocean cyclone had a below average season numbering 9 and 3, respectively. Activity across the southern hemisphere's three basins—South-West Indian, Australian, and South Pacific—was spread evenly, with each region recording seven named storms apiece. So far, 26 Category 3 tropical cyclones formed, including ten Category 5 tropical cyclones in the year, becoming as the third-most intense tropical cyclone activity on record, only behind with 1997 and 2018. The accumulated cyclone energy (ACE) index for the 2014, as calculated by Colorado State University (CSU) was 724 units.
Tropical cyclones in 2002 were spread out across seven different areas called basins. To date, 123 tropical cyclones formed in 2002. 80 tropical cyclones had been named by either a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC). The strongest system was Cyclone Zoe, with a central pressure of 890 hectopascals (26 inHg). The costliest and deadliest tropical cyclone of the year was Typhoon Rusa, killing 233 in South Korea and causing $4.2 billion in damages. 26 Category 3 tropical cyclones, including eight Category 5 tropical cyclones formed in 2002. The accumulated cyclone energy (ACE) index for the 2002, as calculated by Colorado State University was 812 units.
Throughout 2013, 139 tropical cyclones formed in seven different areas called basins. Of these, 67 have been named by various weather agencies when they attained maximum sustained winds of 35 knots. The strongest and deadliest tropical cyclone of the year was Typhoon Haiyan, which was estimated to have a minimum barometric pressure of 895 hPa (26.43 inHg) and caused at least 6,300 deaths in the Philippines. The costliest tropical cyclone of the year was Hurricane Manuel, which was responsible for at least $4.2 billion worth of damages in Mexico. 21 major tropical cyclones formed in 2013, including five Category 5 tropical cyclones. The accumulated cyclone energy (ACE) index for the 2013, as calculated by Colorado State University was 618.5 units.
During 2000, tropical cyclones formed in seven different areas called basins, located within various parts of the Atlantic, Pacific, and Indian Oceans. A total of 140 tropical cyclones formed within bodies of water known as tropical cyclone basins, with 81 of them being further named by their responsible weather agencies when they attained maximum sustained winds of 35 knots. The strongest storm of the year was Cyclone Hudah, peaking with a minimum pressure of 905 hPa (26.72 inHg), and with 10-minute sustained winds of 220 km/h (135 mph). The highest confirmed number of deaths from a storm was from Typhoon Kai-tak, which killed 188 people, however, Leon–Eline may have killed up to 722 people. The costliest storm was Saomai, which caused $6.3 billion in damage. The accumulated cyclone energy (ACE) index for the 2000, as calculated by Colorado State University was 677.3 units.
During 1999, tropical cyclones formed within seven different bodies of water called basins. To date, 142 tropical cyclones formed in bodies of water known as tropical cyclone basins, of which 72 were given names by various weather agencies. The strongest tropical cyclone of the year was Gwenda, attaining maximum sustained winds of 120 knots and a pressure of 900 hPa (26.58 inHg), later tied with Inigo in 2003. Floyd was the costliest tropical cyclone of the year, with around $6.5 billion worth of damages as it affected the Bahamas, the East Coast of the United States, and the Atlantic Canada. The deadliest cyclone of this year was the 1999 Odisha cyclone, which was blamed for over 9,667 deaths as it devastated India. It was also the strongest Northern Hemisphere cyclone of the year with the pressure of 912 hPa (26.93 inHg) and third most intense tropical cyclone worldwide next to Cyclone Gwenda and Cyclone Vance. Three Category 5 tropical cyclones were formed in 1999. The accumulated cyclone energy (ACE) index for the 1999, as calculated by Colorado State University was 606.4 units.
During 1998, tropical cyclones formed within seven different tropical cyclone basins, located within various parts of the Atlantic, Pacific, and Indian Oceans. A total of 125 tropical cyclones formed, with 72 of them being named by various weather agencies when they attained maximum sustained winds of 35 knots. The strongest tropical cyclones were Zeb, Ron and Susan which peaked with a pressure of 900 hPa (26.58 inHg). Hurricane Mitch of late October was the deadliest tropical cyclone, killing 11,000 people as it catastrophically affected Central America, and Mexico as a Category 5 major hurricane. Meanwhile, Georges became the costliest, with the damages amounting to $9.37 billion, which also became the costliest in the history of the Dominican Republic and the country of Saint Kitts and Nevis. Throughout the year, four Category 5 tropical cyclones formed. The accumulated cyclone energy (ACE) index for the 1998, as calculated by Colorado State University was 773.1 units.
Throughout 2008, 124 tropical cyclones have formed in bodies of water known as tropical cyclone basins. Of these, 83 have been named, by various weather agencies when they attained maximum sustained winds of 35 knots. The strongest storm of the year was Typhoon Jangmi in the Western Pacific Ocean. The deadliest storm of the year was Cyclone Nargis, which caused devastating and castatrophic destruction in Myanmar with 138,373 fatalities. The costliest storm of the year was Hurricane Ike, which wreaked havoc thorough Cuba and Texas, with $38 billion in damage. Throughout the year, 24 Category 3 tropical cyclones formed, including one Category 5 tropical cyclone in the year. The accumulated cyclone energy (ACE) index for the 2008, as calculated by Colorado State University was 613.9 units.
In 2024, tropical cyclones will form in seven major bodies of water, commonly known as tropical cyclone basins. Tropical cyclones will be named by various weather agencies when they attain maximum sustained winds of 35 knots. So far, 69 systems have formed, with 48 of them being named. The most intense storm of the year so far is Typhoon Yagi, with a minimum barometric pressure of 915 hPa (27.02 inHg).Among this year's systems, so far, eleven have intensified into major tropical cyclones. Two systems, that being Hurricane Beryl and Typhoon Yagi, became Category 5 tropical cyclone on the Saffir–Simpson scale (SSHWS), with Beryl intensifying a Category 5 tropical cyclone on the Saffir–Simpson scale (SSHWS) with one-minute sustained winds of 270 km/h (165 mph). The ACE index for 2024 so far, as calculated by Colorado State University (CSU), is approximately 203 units. 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 equivalent intensity, divided by 10,000.
