Why do the winds gradually get stronger when a gust front passes through?

Question

Why do the winds gradually get stronger when a gust front passes through?

Answer 1

The primary reason is the presence of relatively dry air in the lower atmosphere. This dry air causes some of the rain falling through it to evaporate, which cools the air. Since cool air sinks (just as warm air rises), this causes a down-rush of air that spreads out at the ground. The edge of this rapidly spreading cool pool of air is the gust front. The second reason is that the falling precipitation produces a drag on the air, forcing it downward. If the wind following the gust front is intense and damaging, the windstorm is known as a downburst.  Also it's not uncommon to be able to see the wind on the radar, this is usually because insects have been known to get caught in the colliding winds at the front!

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