19 April 2014

What is the difference between a storm and a tornado?

A column of spinning air that moves underneath a heavy thunderstorm like a hose
Aarnout van Delden
Dr. Aarnout van Delden
Institute for Marine and Atmospheric Research (IMAU)
Tornado

Storms and tornadoes

Storms and tornadoes are both related to wind, but are two different phenomenons. A storm is a very hard wind over an area the size of the Netherlands. A storm is officially a violent storm when the wind has a speed of at least 90 kilometres per hour.

A column of spinning  

A tornado, or cyclone as it can also be called in the Netherlands, is a local phenomenon: a column of spinning air that moves underneath a heavy thunderstorm like a hose and sucks up everything on and above the ground. In the middle of the United States, the circumstances are perfect for the formation of tornadoes: from the Rocky Mountains, a hard, cold westerly wind blows in from a great height, while at ground level, a southerly wind carries in warm, humid air from the Gulf of Mexico. This difference in wind directions causes the thunderstorm to twirl, which can result in a tornado.

Tornadoes occur in the Netherlands as well

Tornadoes occur in the Netherlands as well. On 3 November 2013, tornadoes moved over Wijk bij Duurstede and Arnhem. In the Netherlands, however, they are less frequent and less heavy because the European differences in temperature and humidity are rarely as big as in the United States. On top of that, the Alps often stop the warm, humid air flowing in from the Mediterranean Sea, preventing it from reaching the Netherlands.