Tuesday, October 15, 2013

Washington Post: Major disaster averted: 5 reasons why Cyclone Phailin not as bad as feared in India

(WashingtonPost) A catastrophe seemed inevitable as monstrous Cyclone Phailin lumbered towards the northeast coast of India. Less than 15 years before, a similar storm, named Odisha, devastated a nearby part of the country, leading to over 10,000 casualties.

It will be days if not weeks before Phailin’s full toll on life and property is known, but from early accounts, there are no signs of a disaster on the scale of 1999 Odisha cyclone. CNN reports a comparatively low 21 deaths from Phailin.

There are several factors which, together, help explain why disastrous consequences were avoided from Phailin.

1) Effective storm warnings: The Indian Meteorological Department, for several days, provided credible information about Phailin, which helped motivate the preparation and response effort.

2) Evacuations: India conducted its largest storm evacuation ever, re-locating more than 900,000 people from the coast to shelters in schools and government offices.

3) Location of Phailin’s landfall and its geography: Phailin washed ashore near Brahmapur about 100 miles farther south than Odisha did in 1999.  In this region, the continental shelf is steeper, meaning there was less low-lying terrain vulnerable to storm surge (the wall of water pushed ashore by the storm’s winds) flooding.

Elevation of the Odisha region of India, with the track of the 1999 Odisha cyclone and forecast track of Phailin overlaid.  (GlobalWarmingArt.org via Jeff Masters’ blog)
4) The storm substantially weakened prior to and during landfall: At landfall, Phailin’s maximum sustained winds were around 125-140 mph whereas they may been 160 mph or even  higher in the 24 hours preceding.  The storm surge peaked at around 13 feet, not the 20+ feet feared. The storm weakened for three possible reasons.

* Its core was re-organizing (in the midst of an eyewall replacement cycle)

* It was moving slowly enough prior to landfall to stir up cold water from deep water underneath.  This upwelling process caused sea surface temperatures  to cool as much as 8-10 degrees Celsius in the storm’s wake! (The steep shelf discussed above meant the water was deep enough for such a cold layer of water to be tapped.)
 Cold pool or cold wake stirred up by Cyclone Phailin

* Its interaction with land

5) The storm’s intensity may have been overestimated  (by some sources, including some we cited): While the Joint Typhoon Warning Center and other U.S. forecasters estimated the storm’s peak intensity reached category 5 levels, the Indian Meteorological Department did not. While the IMD predicted a serious storm (and its predictions motivated the massive preparation efforts), its forecasts were not as dire as some others. Assessing the intensity of a tropical cyclone in the Indian Ocean (and Bay on Bengal) is different from other ocean basins, and the regional expertise of the Indian Meteorological Department may have proven superior.

“They have been issuing warnings, and we have been contradicting them,” said L.S. Rathore, director-general of the Indian Meteorological Department. “That is all that I want to say.”

“As a scientist, we have our own opinion and we stuck to that. We told them that is what is required as a national weather service — to keep people informed with the reality without being influenced by over-warning,” Rathore added, according to the Associated Press.

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