Extreme freeze coming to an end across America

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  • A visualisation of the contrast in conditions across North America. The barrier of cloud across Florida shows the contrast of conditions. To the north is cold, frigid air, while in the south, there is milder tropical air. Photo courtesy NASA.

  • Extreme freeze coming to an end across America
    09.01.2014 16:14

    The recent freezing temperatures have been going on for over a week now. With such a persistent cold period, there has been mass disruption across the northern and mid-western states. However, the end of the extreme freeze is in sight.

    The cold outbreak in North America has yielded some startling images in the past week or so. Pictures of a frozen Lake Michigan and Niagara Falls, frozen fire-hoses, and feet of snow have become quite common. The phrase ‘polar vortex’ has also been bandied around too. This is essentially an upper-atmospheric flow of air that moves west to east across the Arctic latitudes. On occasion, this vortex weakens, allowing for freezing air to invade into North America. Eastern Europe is another location that is susceptible to these cold outbreaks. When much milder air comes into contact with this cold air, it results in quite widespread and persistent snowfall, as seen across many of the eastern states. 

    Exacerbating these freezing conditions is the wind, which makes the air feel much colder than it actually is. On January 6, the average temperature across the whole United States was minus 4.9 degrees Celsius (22.7 degrees Fahrenheit). On January 5, the National Weather Service (NWS) of the U.S. issued a PDS (particularly dangerous situation) warning for the Minneapolis – St. Paul region in Minnesota. Here, the temperature dropped, with the help of the wind chill effect, to 50-65 degrees Fahrenheit below zero (minus 45 to minus 54 degrees Celsius). Warnings were issued to wrap up well, because exposing parts of the human body to the air would result in frostbite in a matter of minutes. States as far south as Alabama and Georgia, places where it generally stays mild throughout the winter, had frosty nights. 

    Forecast for the coming days

    Some relief is in sight for the North Americans, as milder air is set to arrive from the south during Thursday and Friday. As this milder air from the south comes into contact with the frigid air from the north, another snow event is forecast to take places across many of the northern states, while heavy and potentially torrential outbreaks of rain are forecast for the eastern states. The arrival of the milder air will likely result in another snow event for many of the northern states, but maximum daytime air temperatures are expected to be on the plus side of zero. These milder conditions are likely to cause disruption in some places, as snow and ice melt away, resulting in a lot of surface run-off in a short amount of time and a significant rise in river levels. 

    By: Seán Penston