The 2021 North Indian Ocean cyclone season was an average season, the North Indian Ocean cyclone season has no official bounds, but cyclones tend to form between April and December, peaking between May and November. These dates conventionally delimit the period of each year when most tropical cyclones form in the northern Indian Ocean. The season began on April 2, when a depression designated as BOB 01 was formed in the north Andaman Sea and quickly made landfall in Myanmar. The basin remained quiet for over a month before Cyclone Tauktae formed. It rapidly intensified into an extremely severe cyclonic storm before making landfall in Gujarat, become the strongest storm ever to strike that state since the 1998 Gujarat cyclone. Later that month, BOB 02 formed and later strengthened into Cyclone Yaas. Yaas rapidly intensified into a very severe cyclonic storm before making landfall in northwestern Odisha. The season's strongest tropical cyclone was Cyclone Tauktae, with maximum wind speeds of and a minimum barometric pressure of .

The scope of this article is limited to the Indian Ocean in the Northern Hemisphere, east of the Horn of Africa and west of the Malay Peninsula. There are two main seas in the North Indian Ocean — the Arabian Sea to the west of the Indian subcontinent, abbreviated ARB by the India Meteorological Department (IMD); and the Bay of Bengal to the east, abbreviated BOB by the IMD. The official Regional Specialized Meteorological Centre in this basin is the India Meteorological Department (IMD), while the Joint Typhoon Warning Center releases unofficial advisories. On average, four to six cyclonic storms form in this basin every season. Season summary

No systems formed in the basin until April 2, when a depression near the Myanmar coast in the North Andaman Sea formed, however it dissipated the next day. It was considered rare since the storm formation usually begins from mid-April to May. After a month of inactivity, another depression formed off the coasts of Kerala and Lakshadweep. It intensified into a deep depression on the same day and later into a cyclonic storm, being assigned the name Tauktae by the IMD. It continued intensifying, and on May 17, Tauktae peaked as an extremely severe cyclonic storm before making landfall in Gujarat hours later, dissipating on May 19. A few days after Tauktae dissipated, a depression formed in the Bay of Bengal on May 23. It intensified gradually to a cyclonic storm and assigned the name Yaas. It further intensified into a very severe cyclonic storm on May 25 and made landfall in the state of Odisha by the next day, becoming the second cyclone to hit the nation within a span of ten days.

After a long gap of three and a half months, a depression formed in the Bay of Bengal on September 12, becoming the first system in the monsoon season. Not a week later, another depression formed over the east-central Bay of Bengal, making the second system in the post-monsoon season. It later intensified into a deep depression and on 25 September 2021, it intensified into cyclonic storm which was named Gulab, marking the first named storm in the post-monsoon season. Then, after only two days, the remnants of Cyclonic Storm Gulab entered the Arabian sea and regenerated into a Depression and became ARB 02. ARB 02 intensified into a cyclonic storm and was named Shaheen by the IMD. After an unusual month of inactivity, Depression ARB 03 formed in early November and remained out to sea. A couple of days later, Depression BOB 05 formed in the Bay of Bengal but failed to further intensify due to high wind shear. BOB 05 impacted portions of southern India with flooding, and some areas experienced cyclonic storm sustained winds. A few days later, Depression BOB 06 formed which gave additional rainfall and damages to the same places in southern India which were affected by BOB 05 earlier with the worst damages being in Rayalaseema region of Andhra Pradesh. In the month of December, a low pressure area entered into the Andaman Sea from the West Pacific Ocean and it intensified gradually into a cyclonic storm named as Jawad. Initially expected to make landfall over Odisha but due to extremely high wind shear, it weakened rapidly into a low pressure area without making a landfall.

Systems Depression BOB 01

A tropical wave developed stretching between the Malay Peninsula and the equatorial Indian Ocean. From this wave a cyclonic circulation formed on March 26 over the southeast Bay of Bengal. The strong pulse of the Madden–Julian oscillation, high Tropical Cyclone Heat Potential, moderate sea surface temperatures up to , and moderate wind shear, caused the system intensify into a low-pressure area on March 31. An anticyclonic circulation in southeast Asia and an upper tropospheric ridge in the westerlies caused the system to move north-northeastwards. These conditions influenced the system and its intensification as it became a well-marked low-pressure area on April 1 at 09:00 UTC (14:30 IST), and later becoming a depression on April 2 at 00:00 UTC (05:30 IST). Satellite imagery revealed that during its intensification, the clouds of the system organised and developed a low-level circulation center with intense to very intense convection at its center. It continued to maintain its intensity, however, at 00:00 UTC (05:30 IST) on April 3, vertical wind shear increased, causing the system to weaken slightly and the system's clouds to become disorganised, however, a scatterometer pass revealed that it still maintained its intensity. On April 3, at 03:00 UTC (08:30 IST), the clouds further became disorganised, while maintaining its low-level circulation. The system continued to weaken under similar unfavourable conditions with further disorganising of clouds, and at 06:00 UTC (11:30 IST), the system was downgraded to a well-marked low-pressure area, with the system barely having a circulation.

The influence of the system caused light to moderate rainfall in most places of Andaman Islands and heavy rainfall in few places. The system's remnant low caused isolated rainfall over the Myanmar coast. Estimated winds of up to gusting up to were recorded on the island. The first tropical depression of the basin, it was also a rare disturbance since it formed in early April while the most cyclogenesis occurs during mid-April or throughout May.

Extremely Severe Cyclonic Storm Tauktae

On May 14, a depression formed in the Arabian Sea off the coast of Kerala. The JTWC began monitoring the depression, and designated it as Tropical Cyclone 01A. The system gradually intensified, before intensifying into a Deep Depression by 12:00 UTC (17:30 IST) that day. Around 18:00 UTC (23:30 IST) that day, the system intensified into a Cyclonic Storm, and it was given the name Tauktae by the IMD. It later intensified into a Severe Cyclonic Storm at 15:00 UTC (20:30 IST) in May 15. Tauktae's intensification was unusual as it intensified from a depression to a severe cyclonic storm over a period of just two days, with equivalent storms generally taking four to five days to intensify into a severe cyclonic storm. Three hours later, the JTWC upgraded Tauktae to a Category 1-equivalent tropical cyclone on the Saffir–Simpson scale. Tauktae further intensified into a Very Severe Cyclonic Storm at 00:00 UTC (05:30 IST) May 16. At 06:00 UTC (11:30 IST) that day, the JTWC upgraded the storm further to a Category 2 tropical cyclone. INSAT imagery showed that the cyclone had developed an eye by 09:00 UTC (14:30 IST). However, the eye had started to degrade by 15:00 UTC (20:30 IST), according to INSAT imagery, and remained ragged for the rest of the storm's lifetime.

At 03:00 UTC on May 17, Tauktae intensified into an Extremely Severe Cyclonic Storm on 03:00 UTC (08:30 IST) of May 17, which was unexpected since many forecaster predicted that it would be a very severe cyclonic storm. The JTWC upgraded Tauktae to a Category 4-equivalent tropical cyclone soon afterward. However, Tauktae quickly weakened into a Category 3-equivalent tropical cyclone later that day. The cyclone made landfall in the region of Saurashtra between Diu and Una at around 15:30 UTC (21:00 IST). After landfall, Tauktae weakened to a Very Severe Cyclonic Storm. Wind speeds of approximately were recorded at the district of Diu in the union territory of Dadra and Nagar Haveli and Daman and Diu. It became one of strongest tropical cyclone to make landfall in the Indian state of Gujarat since the 1998 Gujarat cyclone. Meanwhile, the JTWC issued their last tropical cyclone warning on the storm at 21:00 UTC (02:30 IST) on May 17. The weakening trend although slower than usual due to the brown ocean effect mostly because of the influence of a western disturbance, which continued as it moved further inland until 14:00 UTC (19:30 IST) on May 19, when it was downgraded to a well-marked low pressure area over Eastern Rajasthan and adjoining west Madhya Pradesh, later dissipating. The combination of a western disturbance and the remnants of Cyclone Tauktae have also caused heavy rainfall in Northwestern India.

A total of 174 people were confirmed to have been killed by the storm, and 81 others are still missing. Heavy rainfall was reported over areas of Kerala, causing flash floods and waterlogging soil; fishing was temporarily banned in the area due to rough seas. Parts of Kerala and Lakshadweep were placed under a red alert on May 14. The second state experienced heavy rainfall as the cyclone tracked west of the Indian coast. In Chellanan, a village in Ernakulam district, homes were submerged underwater due to unexpected rain and coastal erosion. Agricultural losses statewide was ₹828 crore (US$113 million). The administration opened up a relief camp at the local St. Mary's School for the inhabitants of low-lying areas. Due to the ongoing second wave of the COVID-19 pandemic in India, isolated testing facilities were arranged. The most severe effects of Cyclone Tauktae occurred in the states of Maharashtra and Saurashtra in Gujarat. The latter state reported the losses of ₹10,000 crore (US$1.37 billion). The city of Mumbai experienced heavy rainfall, very strong trees and waves crashed the shores. Trees were uprooted and streets were waterlogged. It was the strongest cyclone since Cyclone Nisarga in 2020. As a precaution, flight operations at Chhatrapati Shivaji Maharaj International Airport were temporarily halted before resuming hours later. The cyclone also affected neighbouring countries like Pakistan, Maldives and Sri Lanka. In the Sindh province of Pakistan, four people died due to a roof collapse caused by strong winds.

Very Severe Cyclonic Storm Yaas