Sandeep Mishra
Post News Network
Bhubaneswar, Oct 10: It is October. It is that time of the year which marks the coming of the cyclones and keeps the meteorology department on its toes, bracing against the worst.
But what drives these rough winds up the state’s coast this month? The Indian Meteorological Department (IMD) has already declared October as the “cyclone month” for the state. Orissa POST spoke to experts for the low-down on the intricate relations between this time of the year, the state and the aerial phenomena that lead to cyclones.
The withdrawal of southwest monsoons, favorable wind, moisture in the air and certain other supporting phenomena facilitate the formation of cyclones. These are generally available in October, according Sarat Sahu, the director of meteorological department.
Orissa attracts cyclonic systems towards it from the northern reaches of the Bay of Bengal. High surface temperature in the Bay of Bengal facilitates the formation of such systems.
“In the past, cyclones which hit Orissa sprang from the northern reaches of Bay of Bengal after originating in the Andaman Sea or thereabouts. Such systems move to Bay of Bengal and become giant cyclones. They move northwest and make landfall over the state,” Sahu said.
The pressure over the sea falls if surface temperature of the sea remains in the vicinity of 25 degrees Celsius. Moist air begins to rise from the sea surface, supported by divergence in upper reaches of the atmosphere and convergence in the lower reaches.
Moisture condenses when it reaches higher in the atmosphere and gives out heat in the process. This heat warms the air and lowers pressure further. In due course the low pressure intensifies into a cyclonic storm.
According to IMD data 1,999 super cyclones have hit the region over the past century. One of the more recent super cyclones, one that wreaked much damage October 29, 1999, clocked wind speeds of 260 kmph.
Phailin in 2013 and Hud Hud in 2014 hit Orissa October 12 in the respective years.
Data also reveals that the three cyclones were formed in the northern region of Bay of Bengal — 1999 super cyclone and Phailin formed near the Tanasserim coast while Hud Hud made its base over the Andaman Sea.
UC Mohanty, professor at Indian Institute of Technology Bhubaneswar’s earth, ocean and climate science department, said the location of Orissa and the characteristics of Bay of Bengal play a key role in attracting cyclones to the state.
“We have two periods in a year when cyclones can occur — pre monsoon and post monsoon. Favorable winds and sea surface temperature help formation of cyclones and make them deadly particularly during this time of the year,” Mohanty said.
He added that northwesterly winds in the period push cyclones towards Orissa or north Andhra Pradesh. “Distance from the equator also makes Orissa a favorite destination for cyclones,” Mohanty said.
