Calcutta, India, Cyclone

On October 5, 1864 most of the city of Calcutta, India, was flooded and destroyed by a cyclone. Sixty thousand people were killed at once and many thousands of others died later from the sicknesses and diseases that followed. The cyclone crossed the east coast of India south of the Hooghly River, one of the streams that constitute the delta of the River Ganges, shortly after 10 A.M. As the cyclone entered the narrowing waterway the water level rose until it became a towering forty-foot-high wall. Its height had been raised to a maximum by the arrival of high tide before noon on the same day. Everything was washed away in its path as the water swept inland. In the months that followed, the city, the surrounding area, and the harbor had to be rebuilt.

Different parts of the world have different names and different definitions for the storms they experience. In Asia, a storm with speeds less than 39 mph is called a tropical depression. If the circulating speed is above 39 mph it is named a storm and, if above 73 mph, it is classified as a cyclone. The meteorological conditions in India are very different from the Caribbean. Winds are stronger, rainfall is heavier, and preparations for weather extremes were almost non-existent in the nineteenth century. Hence, there are records of huge losses of life and widespread damage to buildings from that period of history. Even today, as was seen when the Indonesian tsunami of 2004 struck India, many lives can be lost if preparations for coping with disasters are inadequate. A comparison of the Caribbean andSoutheast United States storm environment with that of India helps to explain why India’s storms are enormously destructive. The first thing to note is the temperature difference. India lies south of the Tropic of Cancer while the Southeast United States is north of this line so water temperatures are generally higher in the waters around India. The winds, therefore, are able to carry greater volumes of water vapor at any given time and bring high levels of rain if they are moved over land. In the areas around Calcutta, especially in the mountainous regions north of it, the highest rainfall records in the world are found. Cherrapunji is a community 300 miles northeast of Calcutta and 4,000 feet in elevation, in the country of Bangladesh. It holds the world record for being the wettest place anywhere. Its average annual rainfall is 450 inches but many years have totals far beyond that figure. Calcutta’s rainfall is much less than Cherrapunji, even though it experiences the same winds, because its elevation is close to sea level. The second thing to note is the huge expanse of the Indian Ocean compared with the Caribbean and the equally massive extent of the landmass north of India. The air masses that build up over these areas are larger and denser than we find over either the Caribbean or the United States and, hence, their winds are stronger when storms or cyclones form.