Gust fronts: the how and why of thunderstorm winds

A summer afternoon in Texas means heat and humidity and sometimes a thunderstorm to cool everyone off. 

It’s a normal and sometimes wet way to run through the day but did you know those storms can actually help create more thunderstorms? Here’s how.

The thunderstorms are formed by a combination of warm and cool air. The cool air is denser than warm air and will wedge its way underneath if it gets the chance. That lifts the warm air above the ground where, if conditions are right, it can keep rising to form a cloud. When that cloud gets tall enough it will create rain which falls back to earth.

A screenshot showing a gust front, which is the green arc extending from near Creedmoor through Buda to Wimberly.

The falling rain pulls a whole bunch of cool air from the upper levels of the atmosphere down with it. When that cool air hits the ground it spreads out at the base of the cloud around the storm. The process of spreading out is the cool wind we feel when a thunderstorm approaches. That wind is called outflow and the boundary between the cool air in the outflow and warm air surrounding it is called a gust front or outflow boundary

The cool air can act like a cold front and cause more thunderstorms as it forces itself under the warmer air ahead of the parent thunderstorm. Just like in a normal cold front, the warmer air gets forced upwards, creates clouds and if conditions are right, more thunderstorms.

Heavy rain and lightning are the most common threats with these thunderstorms though some can bring strong winds as well. 

In some cases outflow boundaries can bring very strong winds and in desert environments those winds blow dust. These dust storms happen frequently in Arizona and are called haboobs. Gusts in the strongest haboobs can exceed 60mph. 

Track your local forecast for the Austin area quickly with the free FOX 7 WAPP. The design gives you radar, hourly, and 7-day weather information just by scrolling. Our weather alerts will warn you early and help you stay safe during storms.
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