A broad sweep of colour over North America gives this January 5, 2014 visualisation its impact. Credited to meteorologist Anthony Sagliani using the Living Earth app, it places a major Arctic-air outbreak within a globe-wide view. It is a picture of a weather pattern during a particular winter event, rather than a live map of temperatures today.
Photo: Meteorologist Anthony Sagliani, using the @livingearthhd app.
Check the variable, units and timestamp
Read a weather graphic in three steps: identify the variable, check the units and find the time. A temperature layer is different from a wind-chill layer, and a forecast is different from an observation. Colours help the eye recognise a pattern, but a dark purple patch has no exact numerical meaning unless the map's scale defines it.
The polar vortex and the January 2014 outbreak
The January 2014 cold outbreak was part of the episode that brought the term polar vortex into widespread conversation. The National Weather Service explains that the vortex is a large area of low pressure and cold air around Earth's poles. It is not a newly created storm that suddenly appeared over one town, and southward outbreaks of Arctic air have happened in other winters too. [1]
Explore more: New York during that winter’s storm; air temperature and wind chill explained separately.
What regional reports add to the globe view
A regional weather summary adds detail that the globe cannot show. National Weather Service reporting from northern Indiana describes a sharp drop in temperature between January 5 and 6 as Arctic air followed the departing winter storm. That gives the coloured pattern a sequence in time: a storm passage, a change in air mass and a period of severe cold, with local effects varying across the region. [2]
A continent-wide image is not a local forecast
For a particular street, house or journey, local observations still matter. The broad view is useful for seeing where the cold lies relative to the continent, but it cannot supply an exact reading at a neighbourhood address. Reports from January 2014 provide the context for this graphic. For present-day winter conditions, a current local forecast is the relevant guide.
Sources, photography and further reading
Original feature and image attributions:
- Anthony Sagliani
- livingearthhd
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- New York during that winter’s storm
- air temperature and wind chill explained separately
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