Why do some storms stand still?


Stationary thunderstorms have caused flooding again in recent days. In Somme this Tuesday, a slow-moving storm dropped a large amount of rain, creating an impressive mudslide in the streets of the city. But why do some storms stop?

Stationary storms have been responsible for much of the storm damage we’ve experienced in recent weeks torrential rain. Storm intensity is not the only parameter that leads to damage, its SpeedSpeed also travel.

A strong storm that moves over an area very quickly will sometimes cause less damage than a moderate storm that stays stuck over a city. The main reason that makes a storm stop is often related to the relief: it is huge in the south of France massesmasses There are cloudy thunderstorms between the reliefs, and 50 to 100 mm of rain may fall in a few hours. It is in this situation when floods occur.

The question of wind and humidity

But there are few storms in the north of France mobilemobile for other reasons: low wind at altitude (which meteorologistsmeteorologists call the situation weather reportweather report not very dynamic at altitude), or a headwind that blocks them. A stationary storm can then begin to feed: the rain it generates to make the atmosphere moist, which gives even moreenergyenergy to the storm. Thus, heavy rains can last more than an hour, instead of 15 to 20 minutes for a passing thunderstorm.

Large bodies of water such as a lake or sea can also play the same role in a stationary storm.



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