system
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human
How do gusts of wind happen?

As far as I understand it, wind (or storm) happens because of pressure inequalities. As those high-pressure or low-pressure areas don't "suddenly" appear, I would expect the airflow to be more of a constant thing until pressure is equalized. Where do the gusts come from?
gpt
What is a gust front?
A gust front is the leading edge of cool air rushing down and out from a thunderstorm. There are two main reasons why the air flows out of some thunderstorms so rapidly. 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. 

Gusts(sudden increase in wind speed) and lulls(sudden decrease in wind speed) in air flow are caused by turbulence in the atmosphere. 
The atmosphere becomes turbulent when there is mechanical obstruction to the flow of air or when there is marked convection in the atmosphere.

The former is called mechanical turbulence and the latter is called the thermal turbulence. 

In mechanical turbulence,rotating parcels of air called eddies are formed in the vicinity of the ground.The eddies are potent agents in vertical mixing of air layers and it is the movement of these eddies which causes the lulls and the gusts in the atmosphere. 

In thermal turbulence,air layers when they are subjected to intense solar heating close to the ground ,ascend due to buoyancy and convectional currents are set up.If these currents are sufficiently strong ,turbulent fluctuations are produced which appear as gusts and lulls in the horizontal wind particularly in the afternoons of hot summer days.