Blame slow jet stream for US deep freeze - environment - 07 January 2014 - New Scientist
Don't blame the polar vortex.
The real reason for the cold snap paralysing North America this week is a slow jet stream.
The cold is extreme, and deadly. In Minnesota, the wind chill was down to minus 51 °C. Chicago (pictured) hit a record low of minus 27 °C on Monday, and ice built up along Lake Michigan. TV weather channels warned that frostbite could set in after just 5 minutes of exposure, planes have been grounded after fuel froze, schools have closed and Indianapolis banned driving. Key crops like wheat are also at risk.
It has been 20 years since the entire mainland US was affected like this, says forecaster Brian Korty of the National Oceanic and Atmospheric Administration's Weather Prediction Center in College Park, Maryland.
As temperatures fell, some blamed a mysterious polar vortex, but this is a system of winds in the stratosphere that spins around the Arctic and Antarctic during their respective winters, many kilometres above the weather. There is nothing unusual about the polar vortex, according to the UK Met Office. Instead, cold Arctic air has reached North America thanks to a weakened jet stream – the continent's atmospheric conveyor belt.
No comments:
Post a Comment