Hyderabad: The term polar vortex usually refers to the gigantic circular upper air weather pattern in the Arctic region. It is a normal pattern that is stronger in the winter and keeps some of the coldest weather bottled up near the North Pole. But at times some of the vortex can break off or move south, bringing unusually cold weather south and permitting warmer weather to creep up north. This week, parts of the United States are experiencing the 10th and coldest polar vortex event this