Here’s a basic weather-related question that has always bothered me.
I understand what causes wind… the result of high and low pressure systems… but in layman’s terms, what causes a gust of wind?
I live in the Rocky Mountains and severe wind storms are not uncommon. But as I watched the trees on my property today I noticed the wind would kick up for a few minutes, and then die down for a few minutes, and then kick up again.
What causes the wind to gust like that? Does it have to do with the immediate topology of my property (trees and mountains etc.), or is it because of upper level “disturbances”? Meteorologists please explain to me what causes wind gusts?
It’s probably easiest to imagine air moving like water moves. They are both fluids after all.
Imagine you can pour a sheet of water along a flat concrete surface. At low volumes, a long way from the source of the flow the water will flow as a nice flat sheet, However where the water is pouring onto the concrete you will get splashes and waves. At higher flow rates the water will start to form rills and finally eddies and waves even at great distances from the source, because the energy is so high that tiny imperfections are amplified out into large effects on flow.
Winds are analogous. Steady winds result from a nice stable, linear flow of fluid from high to low pressure. They almost always occur either a long way form the “source” of the wind or at low wind speeds.
Gusty winds are the equivalent of turbulence in water. Just as you can get water that runs smoothly along a course and you can get water that churns up into rills or rapids and whirlpools. Gusts usually occur at higher wind speeds or close to the source but can also be caused by topography.
As you guessed, being adjacent to mountains helps. The mountains cause eddies (both horizontal and vertical) that go spinning off, leading to gusts of wind.
Turbulence can also be the result of the weather patterns that cause the wind in the first place. When a cold front moves it displaces warmer air, pushing it out of the way as wind. That doesn’t usually occur in a nice linear fashion of course, the air mixes together, causing it to rise and fall unpredictably creating gusts of wind.
Pressure systems can create a similar effect. Where the pressure gradient is small or a long way away the flow is fairly laminar and stable. However where the gradient is high or the pressure centre is close by, the air starts to roll over itself and form waves and eddies, and those waves and eddies are what we experience as wind gusts.