{"id":6638,"date":"2022-03-10T00:00:00","date_gmt":"2022-03-09T23:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/?post_type=purple_issue&p=6638"},"modified":"2022-03-23T10:21:18","modified_gmt":"2022-03-23T09:21:18","slug":"the-explainer-tornados","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/2022\/03\/10\/the-explainer-tornados\/","title":{"rendered":"The Explainer: Tornados"},"content":{"rendered":"\n
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THE EXPLAINER: <\/span>
TORNADOES<\/span><\/h3>\n\n\n\n
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WHAT IS A TORNADO AND HOW DOES IT FORM?<\/span><\/strong><\/h4>\n\n\n\n

Tornadoes, sometimes called twisters or whirlwinds, are intense vortices stretching from the Earth\u2019s surface to the base of stormy, cumulonimbus clouds \u2013 these clouds extend deeply in the vertical and often have an anvil-shaped top. Typically, tornadoes measure around 100 metres in diameter, travelling on average around five kilometres before they dissipate. Tornadoes form from mesocyclones, large-scale regions of rapidly rotating air that flow within the cumulonimbus clouds. Cool, dry air can wrap around these mesocyclones, creating a strong temperature contrast which intensifies the spinning, drops the central pressure and extends the vortex to the ground, thus the tornado is born. As tornadoes are made up of air, they are invisible to the naked eye unless they are transporting some other material, such as condensed water in the form of water vapour, dust, or larger debris, so more often than not take on a dark appearance. Given the chaotic nature of tornadoes, they are a nightmare to predict, so often it is the original mesocyclone that will start to alert the forecasters on where to look.<\/span><\/p>\n\n\n\n

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WHAT ARE THE DIFFERENT TYPES OF TORNADO?<\/span><\/strong><\/h4>\n\n\n\n

Weather agencies around the world include different phenomena in their classification of tornadoes. So for instance, intense waterspouts, which form over water from a mesocyclone, often only officially count as a tornado if they make landfall. An extremely rare subset of these are known as snowspouts \u2013 essentially the same type of circulation but formed in regions of snow. There are also a number of other tornado-like vortices, for instance dust- or fire-devils. The former being a small vortex consisting of dust that can form from updraughts without the need for storm clouds. The latter being a small vortex funneling fire, often formed in large wildfires. While these phenomena typically look much like tornadoes, they are generally not considered part of the grouping, because their formation is so different, and the vortex itself does not usually extend from the Earth\u2019s surface to a cloud base.<\/span><\/p>\n\n\n\n