This funny image (though what it depicts isn't funny for people who live in the US) from Greg Laden's blog
shows how a portion of the polar vortex broke off and moved over
to the US, bringing ultra-low temperatures and snow to the Midwest and Northeast.
Andrew Freedman wrote over at Climate Central a couple of days ago:
"The cause of the Arctic outbreak can be traced to northeastern Canada and Greenland, where an area of high pressure and relatively mild temperatures is set to block the eastward progression of weather systems, like an offensive lineman protecting the quarterback from the other team."
Frigid air drove southward from the Canadian Arctic brought the coldest temperatures in at least 20 years to a huge
swath of the U.S. The Midwest, Great Lakes, Ohio Valley, Northeast, and
Mid-Atlantic were the most severely impacted, but even
parts of the South had unusually cold temperatures in January.
This map shows a large
area of much below average temperatures (in blue and purple) across the
lower 48 states. At the peak of the Arctic outbreak, temperatures were between 20°F
and 40°F below average in large parts of the continental U.S., with
dangerous wind chills affecting cities like Minneapolis, Chicago,
Cleveland, St. Louis, Washington, D.C., New York, and Boston. The U.S.has the dubious distinction of experiencing the largest cold
temperature anomalies of any land area in the Northern Hemisphere during
the height of the biting cold. By comparison, temperatures across
Greenland and much of the Arctic will be above average for this time of
year, albeit still frigid.
According to the National Weather Service,
the “epicenter” of the bitter cold was the Ohio Valley, where
temperatures were 40°F below average. A storm system drove the Arctic cold front along the East Coast, spreading snow and strong winds across the Lower
Mississippi Valley, Appalachians, and New England.
The cause of the Arctic outbreak can be traced to northeastern Canada
and Greenland, where an area of high pressure and relatively mild
temperatures is set to block the eastward progression of weather
systems, like an offensive lineman protecting the quarterback from the
other team.
