North Indian Ocean tropical cyclone facts for kids

This map shows where cyclones traveled in the North Indian Ocean from 1970 to 2005.

Imagine giant spinning storms over the ocean! These are called tropical cyclones, and they form in the northern part of the Indian Ocean. This area is north of the equator, near the Indian subcontinent. While these storms can happen all year, they are most common between April and June, and again from October to December.

Ocean Areas Where Cyclones Form

Very strong cyclones, Luban and Titli, over the Arabian Sea and Bay of Bengal in October 2018.

The North Indian Ocean isn't the busiest place for tropical cyclones, with only about seven percent of the world's storms forming here. However, the cyclones that do form here can be very dangerous. This is because they often hit areas where many people live.

The India Meteorological Department (IMD) is a special weather center. It watches over this ocean area, warns people about storms, and gives names to the cyclones.

This ocean region is split into two main parts: the Bay of Bengal and the Arabian Sea.

The Bay of Bengal

The Bay of Bengal is in the northeast part of the Indian Ocean. The IMD calls it BOB. This area is the most active and has seen some of the deadliest cyclones ever. Countries like India, Bangladesh, Myanmar, Sri Lanka, and Thailand share its coastline. One of the strongest cyclones in this bay was the 1999 Odisha cyclone.

The Arabian Sea

The Arabian Sea is in the northwest of the Indian Ocean. The IMD calls storms here ARB. Countries like India, Yemen, Oman, the UAE, Iran, Pakistan, Sri Lanka, the Maldives, and Somalia are along its coast.

The Arabian Sea is known for its Monsoons, which are strong seasonal winds. These winds bring rain to the Indian subcontinent in the summer. Cyclones are less common here, but they can still be very powerful. Cyclone Gonu was the strongest and most expensive storm recorded in this area.

How We Study Cyclones

Early Studies

Scientists began studying tropical storms in the Bay of Bengal and Arabian Sea in the 1800s. A scientist named Henry Piddington used records from ships to learn about these storms. He wrote many reports between 1839 and 1858, describing individual storms and their paths.

Naming Storms and New Scales

The IMD started naming tropical cyclones in this area in 2004. The first one was Cyclone Onil in September 2004.

In 2015, they updated how they measure storm strength. Now, a storm with very strong winds (between 90 and 120 knots, or about 167 to 222 kilometers per hour) is called an extremely severe cyclonic storm.

Scientists have also found that since 1979, there's been more rain before the monsoon season and stronger cyclones in the Bay of Bengal. This might be because of changes in the monsoon winds. These changes can make more cyclones form and direct them towards Myanmar. Pollution from human activities might be causing these regional climate changes.

Cyclone Weather Patterns

How and When Cyclones Form

On average, only about five to six tropical cyclones form in this ocean area each year. Most of them form between March and June, and again from October to December. The busiest months are May and November.

Most of these storms start in the Bay of Bengal. They often form in the southeastern part of the bay, in the Andaman Sea, or sometimes they are what's left of a typhoon that came from the South China Sea. Warm ocean water and lots of moisture make the Bay of Bengal a good place for cyclones to grow.

In the Arabian Sea, storms usually form in the southeastern part or come from the Bay of Bengal. However, fewer cyclones form here because the water is often cooler and there are stronger winds higher up in the atmosphere. But if the Indian Ocean Dipole (a climate pattern) is strong, more cyclones than usual can form, as seen in the 2019 season.

Very few cyclones develop from June to September. These are the Monsoon months, and strong winds high in the atmosphere can stop storms from getting very powerful. These storms usually stay as weaker systems before hitting land in Odisha or West Bengal.

How Cyclones Move

Most storms in this region first move towards the northwest. Then, they often turn either towards the southwest or, more commonly, towards the northeast.

In the Arabian Sea, storms usually move northwest towards the Arabian Peninsula. But sometimes, they turn northeast after crossing 15°N latitude and hit the Gujarat coast in India. In the Bay of Bengal, storms generally move northwest until they reach the east coast, then they often turn northeast.

How Cyclones Get Stronger

Cyclones are most likely to get much stronger in April, May, and November. During these months, more than half of the weaker storms (called depressions) turn into full cyclonic storms. About a quarter of them become even stronger cyclones.

Where Cyclones Hit Land

In the Arabian Sea, many storms weaken and disappear over the ocean without hitting land. But a good number of them do hit the west coast of India, especially the states of Gujarat and Maharashtra. About 11 percent of these storms hit the Arabian Peninsula, the Horn of Africa, or Pakistan. Rarely, some storms even hit Iran, like Cyclone Gonu in 2007. Other storms like Cyclone Yemyin and Kyarr also caused damage in Iran.

In the Bay of Bengal, most storms hit the Indian states of Odisha or West Bengal. Many also hit Andhra Pradesh and Tamil Nadu. About 30 percent of the cyclones hit Bangladesh, Sri Lanka, and Myanmar. The remaining 13 percent just disappear over the ocean without reaching land.

Climate Change and Cyclones

After many powerful cyclones in recent years (like in 2018, 2019, 2020, and 2021), many weather experts believe that climate change is playing a role.

Normally, about five strong cyclones form in the Arabian Sea each year. But in 2019, there were eight, which tied the record from 1902! Studies show that in recent decades, the Arabian Sea's surface temperature has gone up by about 1.2 to 1.4 degrees Celsius.

During Cyclone Amphan's rapid strengthening, the Bay of Bengal's water temperature was as high as 33 degrees Celsius. Parts of the Arabian Sea reached 32 degrees Celsius before Cyclone Nisarga formed.

According to India's Ministry of Earth and Science, the number of very severe cyclonic storms has increased by one per decade in the last twenty years. Even though the total number of cyclones might have gone down, the ones that do form are becoming more powerful. Higher temperatures make cyclones stronger and help them form faster. Rising sea levels also cause bigger storm surges, which means more severe flooding and damage to coastal towns. Experts predict that cyclones will continue to be more dangerous and stronger as ocean temperatures keep rising.

Recent Cyclone Seasons

Over the years, the North Indian Ocean has seen many cyclone seasons. Here's a look at the most recent ones:

Cyclone Records

• Strongest Cyclone: The 1999 Odisha Cyclone was the most intense tropical cyclone in this basin. It hit the Indian state of Odisha with winds up to 260 kilometers per hour.
• Costliest Cyclone: Cyclone Amphan caused the most damage, costing an estimated $13.2 billion when it hit the West Bengal coast in May 2020. This broke the record held by Cyclone Nargis, which cost $4 billion.
• Deadliest Cyclone: The 1970 Bhola Cyclone caused the most deaths, with over 500,000 people losing their lives in the Ganges-Brahmaputra delta region. It hit land in Tazumuddin Upazila in what is now Bangladesh.
• Smallest Cyclone: Cyclone Ogni was the smallest, with a diameter of only 100 kilometers. It hit the Andhra Pradesh coast on October 30, 2008.
• Largest Cyclone: The 1999 Odisha Cyclone was also the largest tropical cyclone to hit the coast of Odisha.
• Wettest Cyclone: Severe Cyclonic Storm ARB 01 (2004) brought the most rain. One weather station recorded 184 centimeters of rain between May 5 and 7, 2004.

Images for kids

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  This ESSA 3 satellite image was taken on November 3, 1966, at 0819 UTC of a tropical cyclone striking Madras, India

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  The 1999 Odisha Cyclone making landfall over Odisha in 1999.

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  Cyclone Gonu at its peak in 2007.

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  Cyclone Kyarr was the first super cyclone since 2007.

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  Amphan was the costliest cyclone in the basin to strike land.

See Also

• Tropical cyclone
• Atlantic hurricane season
• Pacific hurricane season
• Pacific typhoon season
• South-West Indian Ocean tropical cyclone
• Australian region tropical cyclone
• South Pacific tropical cyclone
• South Atlantic tropical cyclone
• Mediterranean tropical-like cyclone