Question about thunderstorm winds

[MatthewCarman]

A friend of mine had a question I could not answer and he could not find the answer online so I told him I would post his question over here.

I have a question, why don't the winds always reach the ground with elevated thunderstorms? I will have east winds at the surface becoming calm then a wind shift with the gust front and shelf cloud, other times, no shelf cloud, no gust front , just east winds through the storms.

Is there also a reason why some thunderstorms in general ( surface or elevated) have winds blowing in the opposite direction on the backside while other times its from one direction the whole time?

 

[Paul Knightley]

It depends on whether the precipitation is heavy enough to bring air from aloft down with it. But more specifically, it depends on the moisture profile. If the air is rather moist, there may not be too much evaporation of the descending rain, and so not much cooling, and so the descending air does not accelerate. At other times, if there is dry air at mid levels, or sub-cloudbase levels, the precip will evaporate some, and this will cause the surrounding air to cool, and thus descend, bringing air with the momentum of the winds aloft down.

 

[MatthewCarman]

Thankyou Paul. I will let my friend know.