Rochester, NY (WROC) — Wind, from a slight breeze on a summer’s day to the roaring gusts of the winter time, it’s hard to escape in Western New York. While it may seem like a simple everyday occurrence, how a windy day comes together can be a lot more complicated than you think.
A sense of scale
As we break down what causes wind below, it’s important to talk about the scale of the moving pieces in this blog. For the most part, were focusing on what is known as the ‘synoptic scale’, or areas covering over 600 miles in distance. For reference, that’s further than if you were to fly from Rochester, NY to Charlotte, NC!
What causes wind?
In its most basic form, wind is the process of air being moved, or advected, from an area of higher pressure to one of lower pressure. The greater the difference in pressure between those two areas the stronger the flow, and therefore the wind, will be. This concept is called the ‘Pressure Gradient Force’ or PGF for short. It applies to pretty much any fluid, and yes air despite not being a liquid is considered a fluid.
So, why is it so windy in the Fall in Western New York?
The short answer is bigger differences in pressure are more common during the fall and winter, so we see more wind. For a more detailed answer keep reading:
Fall is considered a transition season, we get some summer warmth and some winter chill, sometimes even on the same day if a front is passing through. Much like when there’s a large difference in pressure over an area, a large difference in temperature can also have an effect on the wind. This is because of two things:
- The atmosphere doesn’t like being unstable so it tries to balance the temperatures on either side. To do this, warmer air needs to be moved into the area of cooler air, and vice versa. To put it another way, it needs to be pushed by the wind to one place or another.
- Differences in density, warm air is less dense than cold air. Density and pressure share a simple relationship, Pressure = Density * Gravity * Height.
- Gravity is a constant on Earth and doesn’t change so we can more or less ignore it, we’ll also assume the height of what we’re measuring doesn’t change enough to impact the outcome so we can drop that too. This leaves us with the basic idea that as the density of air changes, so can the pressure.
Now that it’s established that drastic changes in temperatures are more or less related to large changes in pressure over an area the concept that these can influence the wind becomes a bit clearer. To circle back, when do we tend to see the biggest temperature differences over a large area? During a transition season like fall or the beginning of winter.
Keep in mind, this is just scratching the surface, literally, of why it can get so windy towards the end of the year. The atmosphere extends for hundreds of miles above our heads, and while we focus on only the lowest part of it called the troposphere, even that can still extend to an altitude of over 6 miles above us! One of the big things in this layer is the jet stream, a band of stronger winds usually located near the top of the troposphere.
The jet stream exists because of the same concepts as any other wind, air is flowing from high to low pressure, and its strength can also be influenced by large-scale differences in temperature. In this case, we’re taking on an even larger scale than before, think of the difference in temperature from the equator to the poles, this is referred to as ‘planetary scale’.
During the fall and winter, as cold air pushes south, the strength of the jet stream increases over the United States as the difference in temperatures increases from north to south. A stronger jet stream can help to create stronger areas of low pressure, which are usually associated with storm systems. In this case, the stronger the storm system the lower the pressure it has. So, applying what we know already, the lower the pressure, the greater the difference in pressure between the center of the storm, and the surrounding area, and thus the stronger the winds that get produced.
There are truly a hundred different answers to this question. But without writing out a few semesters’ worth of math and science notes. This is a solid look at some of the basic forces at work during those blustery days.