How pressure changes create powerful winds that fuel extreme weather

Windstorms can seem like they come out of nowhere, hitting with a sudden blast. They might be hundreds of miles long, stretching over several states, or just in your neighborhood.

But they all have one thing in common: a change in air pressure.

Just like air rushing out of your car tire when the valve is open, air in the atmosphere is forced from areas of high pressure to areas of low pressure.

The stronger the difference in pressure, the stronger the winds that will ultimately result.

On this forecast for March 18, 2025, from the National Oceanic and Atmospheric Administration, L represents low-pressure systems. The shaded area over New Mexico and west Texas represents strong winds and low humidity that combine to raise the risk of wildfires. [Image: NOAA Weather Prediction Center]

Other forces related to the Earth’s rotation, friction and gravity can also alter the speed and direction of winds. But it all starts with this change in pressure over a distance—what meteorologists like me call a pressure gradient.

So how do we get pressure gradients?

Strong pressure gradients ultimately owe their existence to the simple fact that the Earth is round and rotates.

Wind speed and direction in the upper atmosphere on March 14, 2025, show waves in the jet stream. Downstream of a trough in this wave, winds diverge and low pressure can form near the surface. [Image: NCAR]

Because the Earth is round, the sun is more directly overhead during the day at the equator than at the poles. This means more energy reaches the surface of the Earth near the equator. And that causes the lower part of the atmosphere, where weather occurs, to be both warmer and have higher pressure on average than the poles.

Nature doesn’t like imbalances. As a result of this temperature difference, strong winds develop at high altitudes over midlatitude locations, like the continental U.S. This is the jet stream, and even though it’s several miles up in the atmosphere, it has a big impact on the winds we feel at the surface.

Because Earth rotates, these upper-altitude winds blow from west to east. Waves in the jet stream—a consequence of Earth’s rotation and variations in the surface land, terrain and oceans—can cause air to diverge, or spread out, at certain points. As the air spreads out, the number of air molecules in a column decreases, ultimately reducing the air pressure at Earth’s surface.

The pressure can drop quite dramatically over a few days or even just a few hours, leading to the birth of a low-pressure system—what meteorologists call an extratropical cyclone.

The opposite chain of events, with air converging at other locations, can form high pressure at the surface.

In between these low-pressure and high-pressure systems is a strong change in pressure over a distance—a pressure gradient. And that pressure gradient leads to strong winds. Earth’s rotation causes these winds to spiral around areas of high and low pressure. These highs and lows are like large circular mixers, with air blowing clockwise around high pressure and counterclockwise around low pressure. This flow pattern blows warm air northward toward the poles east of lows and cool air southward toward the equator west of lows.

A map illustrates lines of surface pressure, called isobars, with areas of high and low pressure marked for March 14, 2025. Winds are strongest when isobars are packed closely together. [Image: Plymouth State University, CC BY-NC-SA]

As the waves in the jet stream migrate from west to east, so do the surface lows and highs, and with them, the corridors of strong winds.

That’s what the U.S. experienced when a strong extratropical cyclone caused winds stretching thousands of miles that whipped up dust storms and spread wildfires, and even caused tornadoes and blizzards in the central and southern U.S. in March 2025.

Whipping up dust storms and spreading fires

The jet stream over the U.S. is strongest and often the most “wavy” in the springtime, when the south-to-north difference in temperature is often the strongest.

Winds associated with large-scale pressure systems can become quite strong in areas where there is limited friction at the ground, like the flat, less forested terrain of the Great Plains. One of the biggest risks is dust storms in arid regions of west Texas or eastern New Mexico, exacerbated by drought in these areas.

When the ground and vegetation are dry and the air has low relative humidity, high winds can also spread wildfires out of control.

Even more intense winds can occur when the pressure gradient interacts with terrain. Winds can sometimes rush faster downslope, as happens in the Rockies or with the Santa Ana winds that fueled devastating wildfires in the Los Angeles area in January.

Violent tornadoes and storms

Of course, winds can become even stronger and more violent on local scales associated with thunderstorms.

When thunderstorms form, hail and precipitation in them can cause the air to rapidly fall in a downdraft, causing very high pressure under these storms. That pressure forces the air to spread out horizontally when it reaches the ground. Meteorologists call these straight line winds, and the process that forms them is a downburst. Large thunderstorms or chains of them moving across a region can cause large swaths of strong wind over 60 mph, called a derecho.

Finally, some of nature’s strongest winds occur inside tornadoes. They form when the winds surrounding a thunderstorm change speed and direction with height. This can cause part of the storm to rotate, setting off a chain of events that may lead to a tornado and winds as strong as 300 mph in the most violent tornadoes.

Tornado winds are also associated with an intense pressure gradient. The pressure inside the center of a tornado is often very low and varies considerably over a very small distance.

It’s no coincidence that localized violent winds from thunderstorm downbursts and tornadoes often occur amid large-scale windstorms. Extratropical cyclones often draw warm, moist air northward on strong winds from the south, which is a key ingredient for thunderstorms. Storms also become more severe and may produce tornadoes when the jet stream is in close proximity to these low-pressure centers. In the winter and early spring, cold air funneling south on the northwest side of strong extratropical cyclones can even lead to blizzards.

So, the same wave in the jet stream can lead to strong winds, blowing dust and fire danger in one region while simultaneously triggering a tornado outbreak and a blizzard in other regions.

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Chris Nowotarski is an associate professor of atmospheric science, Texas A&M University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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