Seasonal changes in the atmosphere across the Northern Hemisphere bring about asouthward shift in storm tracks crossing North America.During October, the increasing temperature gradient between the fast-coolingNorth and the still warm South quickens the jet stream.
This, in turn, brings the first well-developed autumn storms, which often maketheir way across the northern tier of states and southern Canada.
During November and December, chilly air gives way to bitterly cold air in theArctic, further quickening and relocating the jet stream southward.
At this time, storms tend to be stronger and track still farther south thatthose of early autumn.
The underlying truth here is that storms linked to the jet stream are driven bythe pent-up energy of the north-south temperature gradient. This is unliketropical storms, which derive their energy from the heat stored in the upperwaters of the tropical seas.
Story by AccuWeather.com Senior Meteorologist Jim Andrews
