A tropical cyclone is a rotational low pressure system in tropics when the central pressure falls by 5 to 6 hPa from the surrounding and maximum sustained wind speed reaches 34 knots (about 62 kmph). It is a vast violent whirl of 150 to 800 km, spiraling around a centre and progressing along the surface of the sea at a rate of 300 to 500 km a day.
Cyclone Prone Areas in India
India has a coastline of about 7,516 km of which 5,400 km is along the mainland. The entire coast is affected by cyclones with varying frequency and intensity. Although the North Indian Ocean (the Bay of Bengal and Arabian Sea) generates only about 7% of the world's cyclones (5 to 6 Tropical Cyclones per year) their impact is comparatively high and devastating, especially when they strike the coasts bordering the North Bay of Bengal.Thirteen coastal states and Union Territories (UTs) in the country are affected by tropical cyclones. Four states (Tamil Nadu, Andhra Pradesh, Orissa and West Bengal) and one UT (Puducherry) on the east coast and one state (Gujarat) on the west coast are more vulnerable to cyclone hazards.
The India Meteorological Department (IMD) is the nodal government agency that provides weather services related to cyclones in India.
Classification of Cyclones in India: The criteria followed by Meteorological Department of India (IMD) to classify the low pressure systems in the Bay of Bengal and in the Arabian Sea as adopted by World Meteorological Organisation (WMO) are as under:
Type of Disturbances
|
Associated Wind Speed in the Circulation
|
Low pressure Area
|
Less than17 knots (<31 kmph)
|
Depression
|
17 to 27 knots (31 to 49 kmph)
|
Deep Depression
|
28 to 33 knots (50 to 61 kmph)
|
Cyclonic Storm
|
34 to 47 knots (62 to 88 kmph)
|
Severe Cyclonic Storm
|
48 to 63 knots (89 to 118 kmph)
|
Very Severe Cyclonic Storm
|
64 to 119 knots (119 to 221 kmph)
|
Super Cyclonic Storm
|
120 knots and above (222 kmph and above)
|
Recent Cyclones of Andhra Pradesh
| Name of the Cyclone | Year of Occurrence |
| Hudhud | 12 October 2014 |
| Lehar | 25 November 2013 |
| Helen | 21 November 2013 |
| Nilam | October 2012 |
| Laila | May 2010 |
| Khai-Muk | November 2008 |
| Yemyin | June 2007 |
The recent deadly cyclones that hit Indian coastCyclone Phailin (2013) – The Cyclone Phailin is a category 5 storm that struck the Odisha and Andhra coast on 11 October 2013 causing massive destruction in the region- affecting 12 million people. Phailin is a Thai word which means Sapphire. This cyclone prompted India's biggest evacuation in 23 years with more than 5,50,000 people being moved from the coastline in Odisha and Andhra Pradesh to safer shelters. Phailin brought very heavy rain of over 600 mm at many stations of Odisha. It also damaged crops worth Rs 2,400 crore and claimed over 40 lives. Loses due to Cyclone Phailin were estimated to be around rupees 420 crore.
Cyclone Nilam (2012) - Cyclonic Storm Nilam was the deadliest tropical cyclone to directly affect south India that made landfall near Mahabalipuram on October 31 as a strong cyclonic storm with peak winds of 85 kmph. Nilam caused economic losses of around Rs 100 crore because of torrential rain.
Cyclone Thane (2011) - Thane was the strongest tropical cyclone of 2011 that became a very severe cyclonic storm on December 28, as it approached the Indian states of Tamil Nadu and Andhra Pradesh and made landfall at north Tamil Nadu coast between Cuddalore and Puducherry on December 30. Thane left at least 46 people dead in Tamil Nadu and Puducherry. Cuddalore and Puducherry were the worst affected areas.
Cyclone Laila (2010) - Severe cyclonic storm Laila made a landfall in Andhra Pradesh on the 20 May 2010 and caused major flooding and damage along its path. Ongole in Andhra Pradesh recorded heavy rainfall of about 460 mm in just two days. Another town Addanki received the highest rainfall of 522 mm. The state government faced a loss of over Rs 500 crore due to Cyclone Laila.
Cyclone Jal (2010) - Cyclone Jal killed at least 54 people in India alone. About 300 thousand hectares of cropland was devastated by the cyclone. The remnants of Jal continued to move northwest, brought light to moderate spells of rain in India's warmest state of Rajasthan and also in Gujarat.
Cyclone Phyan (2009) - Cyclonic Storm Phyan developed as a tropical disturbance in the Arabian Sea to the southwest of Colombo in Sri Lanka on November 4, 2009 and made landfall in south India on November 7. Massive damage to property was reported in coastal districts of Maharashtra, such as Ratnagiri, Raigad, Sindhudurg, Thane and Palghar.
Cyclone Nisha (2008) - Over 180 people were killed in Tamil Nadu alone due to heavy rain and floods caused by the cyclone. Orathanadu, in Thanjavur District in Tamil Nadu received over 990 mm of rain within 24 hours. The total amount of rainfall received from Nisha was about 1280 mm. The damage caused by the cyclone was estimated to be about 3789 crores.
The 30 Deadliest Tropical Cyclones in World History
Rank
|
Name / Areas of Largest Loss
| Year |
Ocean Area
|
Deaths
|
| 1. | Great Bhola Cyclone, Bangladesh | 1970 | Bay of Bengal | 500,000 |
| 2. | Hooghly River Cyclone, India and Bangladesh | 1737 | Bay of Bengal | 300,000 |
| 3. | Haiphong Typhoon, Vietnam | 1881 | West Pacific | 300,000 |
| 3. | Coringa, India | 1839 | Bay of Bengal | 300,000 |
| 5. | Backerganj Cyclone, Bangladesh | 1584 | Bay of Bengal | 200,000 |
| 6. | Great Backerganj Cyclone, Bangladesh | 1876 | Bay of Bengal | 200,000 |
| 7. | Chittagong, Bangladesh | 1897 | Bay of Bengal | 175,000 |
| 8. | Super Typhoon Nina, China | 1975 | West Pacific | 171,000 |
| 9. | Cyclone 02B, Bangladesh | 1991 | Bay of Bengal | 140,000 |
| 9. | Cyclone Nargis, Myanmar | 2008 | Bay of Bengal | 140,000 |
| 11. | Great Bombay Cyclone, India | 1882 | Arabian Sea | 100,000 |
| 12. | Hakata Bay Typhoon, Japan | 1281 | West Pacific | 65,000 |
| 13. | Calcutta, India | 1864 | Bay of Bengal | 60,000 |
| 14. | Swatlow, China | 1922 | West Pacific | 60,000 |
| 15. | Barisal, Bangladesh | 1822 | Bay of Bengal | 50,000 |
| 15. | Sunderbans coast, Bangladesh | 1699 | Bay of Bengal | 50,000 |
| 15. | India | 1833 | Bay of Bengal | 50,000 |
| 15. | India | 1854 | Bay of Bengal | 50,000 |
| 19. | Bengal Cyclone, Calcutta, India | 1942 | Bay of Bengal | 40,000 |
| 19. | Bangladesh | 1912 | Bay of Bengal | 40,000 |
| 19. | Bangladesh | 1919 | Bay of Bengal | 40,000 |
| 22. | Canton, China | 1862 | West Pacific | 37,000 |
| 23. | Backerganj (Barisal), Bangladesh | 1767 | Bay of Bengal | 30,000 |
| 24. | Barisal, Bangladesh | 1831 | Bay of Bengal | 22,000 |
| 25. | Great Hurricane, Lesser Antilles Islands | 1780 | Atlantic | 22,000 |
| 26. | Devi Taluk, SE India | 1977 | Bay of Bengal | 20,000 |
| 26. | Great Coringa Cyclone, India | 1789 | Bay of Bengal | 20,000 |
| 28. | Bangladesh | 1965 (11 May) | Bay of Bengal | 19,279 |
| 29. | Nagasaki Typhoon, Japan | 1828 | Western Pacific | 15,000 |
| 30. | Bangladesh | 1965 (31 May) | Bay of Bengal | 12,000 |
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