CYCLONE AILA : An Introduction

Introduction

In the year 2009, a relatively strong tropical storm caused extensive damage to coastal areas of India and Bangladesh. This was the second tropical Cyclone of the 2009 North Indian Ocean cyclone season.

It was known as severe cyclonic storm Aila or simply Cyclone Aila.

About 330 people were killed and ~8000 went missing after the storm. Most affected were people living very near to the coast and who were dependent on the sea for earning their livelihood. Villages in the Indian and Bangladeshi Sundarbans were badly damaged. Winds upto 12 kmph blew away the thatched huts.

1 million people were homeless and estimated 20 million were at a  risk of post disaster diseases. Total damage caused was estimated to be ~$ 552.6 million.

Path of Cyclone Aila

Before we go ahead and talk further about this particular cyclone, we should understand about basics of cyclones. Lets try to understand it with a few simple questions. 

What exactly is a Cyclone??

A tropical cyclone is a rapidly-rotating storm system characterized by a low-pressure center, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain. Tropical cyclones typically form over large bodies of relatively warm water. They derive their energy from the evaporation of water from the ocean surface, which ultimately re-condenses into clouds and rain when moist air rises and cools to saturation.

Anatomy of a hurricane.

How do these form ??

Cyclones develop over warm seas near the Equator. Air heated by the sun rises very swiftly, which creates areas of very low pressure. As the warm air rises, it becomes loaded with moisture which condenses into massive thunderclouds. Cool air rushes in to fill the void that is left, but because of the constant turning of the Earth on its axis, the air is bent inwards and then spirals upwards with great force. The swirling winds rotate faster and faster, forming a huge circle which can be up to 2,000 km across. At the center of the storm is a calm, cloudless area called the eye, where there is no rain, and the winds are fairly light.

This is how a tropical Cyclone looks from above.

As the cyclone builds up it begins to move. It is sustained by a steady flow of warm, moist air. The strongest winds and heaviest rains are found in the towering clouds which merge into a wall about 20-30 km from the storm's centre. Winds around the eye can reach speeds of up to 200 km/h, and a fully developed cyclone pumps out about two million tonnes of air per second. This results in more rain being released in a day than falls in a year in a city like London.

Where do these Cyclones occur ??

Cyclones begin in tropical regions, such as northern Australia, South-East Asia and many Pacific islands. They sometimes drift into the temperate coastal areas, threatening more heavily populated regions to the South. Northern Australia has about four or five tropical cyclones every year during the summertime wet season. For a cyclone to develop, the sea surface must have a temperature of at least 26ºC. Tropical Regions of the world impact of cyclone  The main effects of tropical cyclones include heavy rain, strong wind, large storm surges at landfall , and tornadoes. The destruction from a tropical cyclone depends mainly on its intensity, its size, and its location. Tropical cyclones act to remove forest canopy as well as change the landscape near coastal areas, by moving and reshaping sand dunes and causing extensive erosion along the coast. Even well inland, heavy rainfall can lead to mudslides and landslides in mountainous areas. Their effects can be sensed over time by studying the concentration of the Oxygen-18 isotope within caves within the vicinity of cyclones' paths.

After the cyclone has passed, devastation often continues. Standing water can cause the spread of disease, and transportation or communications infrastructure may have been destroyed, hampering clean-up and rescue efforts. Nearly two million people have died globally due to tropical cyclones. Despite their devastating effects, tropical cyclones are also beneficial, by potentially bringing rain to dry areas and moving heat from the tropics poleward. Out at sea, ships take advantage of their known characteristics by navigating through their weaker, western half.

        precautionary measures to be taken before a cyclone occur

1.       Before the cyclone season, check with your local council if your home has been built to cyclone     standards.
2. ·    Check that the walls, roof and eaves of your home are secure.
3. ·    Trim treetops and branches well clear of your home (get council permission).
4. ·    Fit shutters, or at least metal screens, to all glass areas.
5. ·    Clear your property of loose material that could blow about and possibly cause injury or damage  during extreme winds.
6.      In case of a storm warning or other flooding, know your nearest safe high ground and the safest access   route to it.
7. ·    Prepare an emergency kit to take with you and keep a list of emergency numbers on display.
8. ·     When a cyclone watch is issued, fill your car's fuel tank. Ensure that your family members know which is  the strongest part of your house. 
9. ·     Listen continuously to your local radio/TV for further warnings.
10. ·     When the cyclone strikes, disconnect all electrical appliances. Listen to your battery radio for updates.
11. ·     Stay indoors (unless you are asked to evacuate) in the strongest part of the building, i.e. cellar, internal hallway or bathroom. Keep evacuation and emergency kits with you.
12. ·     Protect yourself with mattresses, rugs or blankets under a strong table or bench if the building starts to break up.
13.      Drive carefully as roads may be filled with debris                                                                                 

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d                                              What should the government do?

1. ·         Provide better health facilities at locations prone to such calamities.
2. ·         Provide funds for welfare of the survivors.
3. ·         Have a pre-planned strategy and should also conduct mock drills on how to handle these       circumstances.
4. ·         Spread awareness among people by conducting free workshops.
5. ·         Co-ordinate with the Meteorological department  and have a better early warning system in  place. 
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Forecasting of cyclone by Meteorological Department

The India meteorological department maintains a countrywide network of observational station where weather reports are received at Pune through the Regional Telecommunication Hub (rth) based at New Delhi. With the help of these reports and other observations from the globe, the Pune office issues the All India Daily Weather Bulletin and Weather Forecasts for the entire country     

      For improving the accuracy of cyclone warnings to ports and coastal areas, the department has set up Cyclone Warning Radars along the east coast at Calcutta, Para-deep  Vishakhapatnam, Machilipatnam, Madras and Karaikal and along the west coast at Bhuj, Bombay, Goa and Kochi. These radars can detect and follow cyclones 400 km off the coast. There are 3 Area Cyclone Warning Centers at Calcutta, Madras and Bombay and 3 Cyclone Warning Centres at Vishakhapatnam, Bhubaneshwar and Ahmedabad. The Cyclone Warning and Research Centre at Madras conducts research on cyclones. The complete cyclone warning work is supervised and co-ordinated on real time basis by the Weather Central in the Office of DDGM (WF), Pune. A Cyclone Warning Division at HQrs, has been set up to co-ordinate and supervise the totality of cyclone warning programme in the country. Information received at Pune from the INSAT and Polar Orbiting Satellites of USA and USSR are utilised particularly when cyclones are in the ocean areas beyond the range of the radars. The INSAT system is also used to activate the Disaster Warning System (DWS) network along the coast whenever a tropical cyclone is predicted to strike a district.