Of the cyclones hitting the coastal regions of the country, on average four out of five stampede the eastern shores of peninsular India.
According to the India Meteorological Department, this is because in addition to the storms that originate in the southeast Bay of Bengal and the adjoining Andaman Sea, breakaway typhoons over the Northwest Pacific move across the South China Sea into the Bay of Bengal, intensifying into cyclones.
As the frequency of typhoons over the Northwest Pacific is about 35% of the global annual average, the Bay of Bengal is affected.
“In contrast, Arabian Sea cyclones are mostly their own formations and they also generally move north-west, away from India’s west coast,” said Narasimha Rao, assistant meteorologist, Met Centre, Hyderabad.
Besides, the Arabian Sea is colder than the Bay of Bengal, which inhibits the formation and intensification of the cyclonic system in the former. Warm sea surface temperature is an ideal platform for cyclones.
While the incidence of cyclones is the highest on the Odisha coast, it is Andhra Pradesh that has suffered more.
During the period from 1891 to 2012, Phailin is the 74th cyclone to hit Andhra Pradesh. Of the 73 earlier cyclones, 30 hit the state in October, followed by 19 in November and nine in May.
No cyclones crossed the Andhra coast in January, February, March and April.
Apart from the cyclone of November 1977, when about 15,000 people died, the storm of May 9, 1990, killed around 1000 people. In the storm that struck on November 6, 1996, about 1,500 people died. Severe cyclones hit Odisha in 1971, 1977, 1990, 1996 and 1999.
Fifty years' cyclones in a nutshell
[hindu]
Some cyclones originating over the Bay of Bengal have attained the intensity of super cyclones. And they hav claimed lives and caused destruction to property on a large scale, severest among them being the Orissa super cyclone of October 29, 1999. A look at data of the last 50 years for insights into the vagaries of our cyclones.
Interactive chart
cyclones plus severe cyclones per year1234567810>Number of years of such occurrence between 1963 and 201214101078811>Charts: TR Data source: IMD
Even as the country braces itself to face a cataclysmic storm, data of the past half century seems to suggest that the frequency of cyclones have been on the lower side in recent years.
As many as 74 cyclonic storms occurred between 1993 and 2012, but the number is lower than the 126 seen between 1963 and 1982 .
For context consider what the India Meterological Department (IMD) says about cyclonic storms based on the available dataset stretching back to a longer period: that their average annual frequency in the north Indian Ocean (covering both the Bay of Bengal and Arabian sea) is about 5, which constitutes about 5 to 6 per cent of the global annual average. More cyclones happen in the Bay of Bengal than in the Arabian Sea; the ratio is 4:1. And the most intense cyclones occur during October-November and May-June.
Cyclonic storms are categorised as severe when the wind speed is in the 90 to 119 kmph range and very severe when in the 119-220 kmph range and a super cyclone when it exceeds 220 kmph.
The number of cyclones and severe cyclones India has faced from 1963 to 2012 every year ranges from 1 to 10 (except for the figure 9) and a total of 236 of those have been experienced during this period, based on historical IMD cyclone data covering the Bay of Bengal and Arabian sea. In 1986 there was only one cyclone as against the maximum of 10 recorded in 1976. The IMD says that as many as 10 yearly cylcones have occured only four times over the past century or so: 1893,1926,1930 and 1976.
A NASA Terra satellite image shows cyclone Phailin positioned over the Bay of Bengal on October 11. Photo: AFP/ NASA
During the 50 year period, 143 severe cyclones had occurred with as many as 7 of them being experienced a single year: 1976.
If there are numbers the weather gods seem to particularly favour, these are 3 and 4: these are the number of cyclones (including severe cyclones) recorded per year most during the past 50 years - the frequency being 10 years each.
February and March are months when a cyclone is least likely to happen - only one each have been recorded in those months between 1951 and 2012. That said, cyclones including severe ones have been witnessed in all months during this period - there has never been an instance of a particular month being skipped altogether.
It is Andhra Pradesh that is likely to be most hit by severe cyclones in terms of numbers, while Odisha experiences more cyclones overall. More cyclones occur along the East cost than on the West coast, where Gujarat is vulnerable to them.
