Saturday , 17 November 2018

Preparing for Cyclone Season

Nandkumar Kamat


From Arabian Sea we need to worry about cyclones before monsoon and from Bay of Bengal during October to December. ‘Cyclone’ was a term coined in 1848 by Henry Piddington, British meteorologist. Its origin lies in Greek word ‘kuklos’ i.e. the coil of a snake as the air flow of the storm resembles it. In different areas of the globe different nomenclature is used. In the Atlantic and eastern Pacific, they are known as ‘hurricanes’ and in western Pacific as ‘typhoons’. In the Indian region, they are simply known as ‘tropical cyclones’.

Almost all these storms form within 25° latitude on both sides of the equator except over the 5 °N to 5 °S equatorial  region. Officially south-west monsoon ends on September 30. But it is observed that rainfall continues and counted as post monsoon rainfall. The Canacona flash floods which occurred on October 2, 2009 was an anomaly-almost half a metre rainfall in a day. There is a direct connection between rise in surface temperature (SST) of the sea and development of cyclones.

India was closely watching the development of hurricane system in north Atlantic which created Hurricane Harvey, Irma and Jose. It was amazing to see the path of these hurricanes which had developed thousands of kilometres away before making landfall. Although India Meteorological Department (IMD) has now much better system to monitor development of cyclones and predict their path, there is always a degree of uncertainty. When a cyclone develops in Bay of Bengal and begins to approach the land we can see here in Goa the extension of its arms. Fortunately as compared to much more vulnerable states on India’s east coast, the western seaboard is insulated from Bay of Bengal cyclones.

The new cyclone season begins from next month and we need to assume on basis of past data that chances of development of cyclones in Arabian Sea would be negligible. But in case such a system develops then it would have devastating effect on highly urbanised, densely populated west coast. Already we have seen how Mumbai faced extreme weather events. Rainfall equivalent to full month fell on a single day. Due to unsustainable urbanisation Mumbai has lost the capacitance to face extreme weather events.

In Goa village communities had done thoughtful plantations of coconut trees along the coastal belt followed by raising of bamboo groves. This was aimed to break the wind speed. The energy of cyclonic winds dissipates after encountering such natural barriers.

What we know about Bay of Bengal cyclones? Indo US Science and Technology Forum had made a study of cyclones from Bay of Bengal coastal region based on 120 years of track and intensity data ranging from 1891 to 2010. They found that a total of 606 cyclonic disturbances formed in the Bay of Bengal. Out of 606 cyclones, 325 (54 per cent) crossed India, 95 (16 per cent) Bangladesh, 61 (10 per cent) Myanmar, 25 (4 per cent) Sri Lanka and as many as 100 (17 per cent) dissipated over the sea without making landfall on any of the above countries. Again with respect to the total number of severe cyclonic storms crossing different countries of the region, out of 197 severe cyclonic storms, 109 (55 per cent) crossed the Indian coast, 47 (24 per cent) to Bangladesh, 23 (11 per cent) to Myanmar, 9 (5 per cent) to Sri Lanka and 9 (5 per cent) dissipated over the ocean without making landfall.

The picture is changing due to climate change precipitated by global warming. What happens if higher SST in Bay of Bengal creates conditions from next month favourable for genesis of cyclones. Would India’s eastern seaboard face impacts similar to hurricane Harvey, Irma and Jose? That depends on developments in next few weeks to be closely watched by Indian meteorologists. India has now developed a much improved early warning system to alert the people and administration. But people don’t understand the importance of weather bulletins and alerts raised during cyclonic circulation. Many fishermen have lost their lives in the past due to this.

We have to keep our fingers crossed in the coming weeks – whether west coast would witness extreme weather phenomena, whether cyclonic disturbance from Bay of Bengal would spill over to west coast. So far the district administration has not created any worst case scenarios to deal with such situations. As compared to all the states in India Goa with more geographical area vulnerable to sea level rise is more vulnerable to cyclones or cyclonic disturbances. All our coastal embankments have been built for tidal amplitude of six metres and any increase in this would wash out these bunds and cause massive flooding in flood plains of Mandovi and Zuari estuary.

Panaji a low lying city on low lying island has no capacity to handle cyclones. So people would have to be on alert and need to monitor the weather bulletins. IMD Goa is doing splendid job with the new Doppler Radar system and any disturbance within 150 kilometres radius can be detected. IMD is geared for cyclone season 2017.

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