When Cyclone Thane hit the eastern coast of India, not many could have predicted the extent of damage it would leave behind. While it was expected to cause some destruction, few expected Thane to take more than 40 lives in Tamil Nadu alone and leave some districts utterly devastated. While Chennai escaped with some strong winds and rain, for those living in other coastal districts it meant a nasty end to 2011.
The East-West divide
India has a history of violent cyclones. The earliest recorded storm hit in 1737, on the east coast, killing close to 3,00,000 people. This throws light on an interesting characteristic of tropical cyclones that hit India. It has been found that cyclones that form over the Bay of Bengal are much stronger than the ones which form over the Arabian Sea. For example, the Orissa cyclone of 1999 remains one of the most devastating storms to date.
These storms start as minor depressions and pick up speed as they come closer to the coast. These cyclones may not be ferocious on their own — had the same cyclones hit some other part of the world, the aftermath would have been less devastating. But owing to the special nature of tides on India’s east coast, and the shallow sea coast topography, the final disaster caused by a cyclone remains unmatched.
Storms on the Southeast Asian coast are the most disastrous, in the world. Of course, the lack of preparedness, infrastructure, and disaster management awareness also play a part in managing the disaster.
Further since the Arabian Sea is lower in temperature than the Bay of Bengal, the storms that form on the west coast are less intense.
How is a tropical cyclone formed?
A cyclone is formed by a combination of warm ocean water, low pressure and the earth’s rotation between the Tropic of Cancer and the Tropic of Capricorn. Warm ocean water vapours rise, while the low pressure over the ocean pulls them inward forming a cycle of winds. Since these winds are formed on a much larger scale on a bigger surface, the earth’s rotation makes these winds turn clockwise in the southern hemisphere and anti clockwise in the northern hemisphere. However, these winds lose their intensity by the time they reach land, due to the lack of moisture and ocean heat. Still they are capable of gaining speeds of up to 500 kmph.
How are cyclones named?
When a depression is anticipated to become a cyclone, seen with a steady wind speed of over 65 kmph, the National Oceanic and Atmospheric Administration’s National Weather Service in India names the cyclone based on a list that was prepared in 2000-2004 by eight nations, though official naming started in 2004. Once named, the cyclone is never renamed. Thane figured in Myanmar’s list.
The Orissa cyclone
The Orissa cyclone of 1999 is to date the worst to hit India in the last 15 years. It was a category five storm, also called a Super Cyclone. It started as a small depression over the Malay peninsula, and slowly progressed towards the Indian subcontinent, gathering speed and force, hitting Orissa on October 27, 1999. The cyclone dumped heavy torrential rains in south-west India hitting land at a speed of 250 kmph. Several coastal districts were asked to evacuate before the storm struck, but the death toll still reached 15,000.
It caused a record flooding in low-lying areas, with the storm surge (offshore rise of water due to strong winds) rising up to 8 metres.
Cyclone Laila was the worst storm to hit Andhra Pradesh in 14 years. It developed over the Bay of Bengal and hit Andhra Pradesh on May 20, 2010 at a speed of 129 kmph. Around mid-May, a storm was starting to build in the middle of the Bay of Bengal south of Kolkata in West Bengal, and was seen approaching Chennai from the southeast direction. It was also the first and the deadliest cyclone of the year. Though the death toll from the storm was comparatively low — 36 people still lost their lives. The State government estimated the damages due to the storm at Rs 500 crore.
Cyclone Thane was a Very Severe Cyclone Storm. It crossed Cuddalore with a speed of 140 kmph and left trees uprooted amidst other destruction. Around 49 people died in Cuddalore and Puducherry, the two worst affected areas, with 39 reported dead in Cuddalore. Roads to Cuddalore were blocked by trees, making the district inaccessible for relief operations.