Current Affairs

Issue

A record-breaking tornado storm caused destruction in USA, killing hundreds of people and destroying infrastructure.

 

Background

Tornadoes are common in US during spring-time but occur rarely in December. The event was fuelled by La Nina weather pattern and moist weather.

 

Details

• If confirmed that the twister was singular one, it will break a 100-year old record for how long a tornado stayed on the ground in a path of destruction.

• Atmospheric conditions that create tornadoes are intensifying in recent times, which may be as a result of climate change.

 

Causes of tornado

• Tornadoes are swirling vertical air-columns made of thunderstorms. They stretch from clouds to the ground and move along a path, destroying everything that comes in between.

• Thunderstorm occur through a condition known as atmospheric instability in which  denser, drier cold air is pushed over warmer, humid air.

• A condition known as updraft will start occurring when winds vary in speed or direction at different altitudes.

• The wind changes allow the spin necessary for a tornado. Changes in wind’s speed and direction are needed for strong tornadoes.

• They usually do not occur in winters because of big difference in temperature and air pressure. This time the situation was different.

 

Conditions

• The warm, moist air in mid-west helps formation of tornadoes. This time around, La Nina conditions created warmer conditions.

• Thunderstorms updraft needs to be sustained for tornado to strengthen. Usually they lose energy in a matter of minutes but in this case it sustained for hours.

 

Climate change and tornado outbreaks

• The La Nina event may have been responsible for this storm but scientists say that warm conditions in December may become norm in future as planet starts warming.

• However, every thunderstorm event cannot be attributed to climate change as only 10% of thunderstorms lead to tornadoes.

• Long-term estimates say that US may see more tornadoes occurring in December, which earlier was not the case.

• The tornado area has shifted eastwards in recent times due to increasing temperature and air moisture. People living in Mississippi River Valley and Ohio River Valley are becoming increasingly vulnerable.