Thursday, October 10, 2013

Tropical Cyclone Phailin will Bring Catastrophic Storm Surge to India

NOAA infrared satellite image of Tropical Cyclone Phailin. Source: The Washington Post Capital Weather Gang:

The Bay of Bengal has been the home of the most catastrophic storm surge disasters on the planet. This basin, which is relatively small by global comparison, has experienced 15 of the 21 tropical cyclones that have killed at least 5,000 people (Dube et al. 1997). Storm surge is the main reason for these high fatality totals. In an 11-year period from 1960-1970, this basin observed seven storm surge events that exceeded the height of Hurricane Katrina's surge in 2005. Storm surges generated from tropical cyclones have killed as many as 300,000 people in 1737 and again in 1970 (Dube et al. 1997).

SCIPP has identified the location and height of 57 peak storm surges in the Northern Indian Ocean, 53 of which occurred along the shores of the Bay of Bengal. This work was conducted as part of a global assessment of surge observations and impacts. The highest surge level occurred in 1876 in Bangladesh, when a surge topped out at around 13.7 meters (45 feet). The area most likely to be impacted by Phailin's surge, along the coast of Odisha, has previously experienced several high surges, including a 7.5 meter surge in October 1999 near Paradip, and a 5 meter storm tide in October 1971.

This region tends to experience so many catastrophic storm surges for several reasons. One reason is that intense tropical cyclones sometimes form in this region, fueled by warm ocean waters, yet far enough from the equator to get the spin needed for tropical cyclone development from the Coriolis Effect. Also, the Bay of Bengal is a shallow water basin with a semi-enclosed shape. These factors exacerbate storm surge heights because water essentially gets trapped and displaced water has no where to go but "up." Another reason these surges are so catastrophic is because of the high population density along the coasts of India and Bangladesh.

Tropical Cyclone Phailin has rapidly intensified as it moves across the Bay of Bengal in the direction of India. According to the Joint Typhoon Warning Center, the storm now has maximum sustained winds of 135 knots, which places it on the cusp of becoming a category-5 hurricane according to the Saffir-Simpson Hurricane Wind Scale. The Joint Typhoon Center anticipates the storm will intensify even more as it tracks towards the northwest. This storm will certainly produce a catastrophic storm surge along the Indian coast.

Check back to this blog in the next few days. I am currently looking at wind and tropical cyclone size forecasts issued by the Joint Typhoon Warning Center and comparing these values with historic storms in other ocean basins to provide some type of context and maybe even a rough estimate of potential surge heights. The work we are doing through SCIPP involves building a storm surge climatology, which can be used to provide context, and in some cases a range of possible surge estimates as storms develop.

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