Is there really a rain dome blocking storms over Austin?

Austin's rain forecasts can be off at times. Folks on social media regularly report similar experiences — rain and storms in the forecast for what ends up being a beautiful sunny day.

This discrepancy has become a part of the Austin experience and has led to the conspiracy theory that there's an invisible dome over the city blocking any rain that might fall on it.

It's a favorite of one of Austin’s top conspiracy theorists — no, not Alex Jones; Evil MoPac. The X persona birthed out of a citywide hatred of a maligned freeway regularly posts theories online about a dome that covers the city and repels inbound storms.

The idea of a rain dome sounds like something straight out of The Simpsons, but the truth might be stranger than fiction. The inconsistent rain has to do with a large piece of exposed bedrock that has been in Central Texas long before people started gathering around Barton Springs.

What rocks have to do with it

The rock in question is the Balcones Escarpment, the long ridge west of Austin, sitting beneath Mount Bonnell and forming the eastern boundary of the Texas Hill Country. Peter Hennings, a geology professor at UT Austin, said the escarpment was formed by the same geological event that causes earthquakes.

Michael Minasi

/

KUT News

“In Central Texas, we see evidence of ancient tectonic processes like the fault zone that forms the Balcones Escarpment,” he said.

The escarpment formed about 20 million years ago. The fault line that formed it hasn’t moved much since then, potentially being the cause of only two minor earthquakes in the last 130 years.

The edge of the fault sits about 700 feet higher than the land to the east, where Austin sits.

“This is a pretty distinct topographic rise, which is the first rise as we come off of the coastal plains and the Blackland Prairie into the Hill Country of Texas,” Hennings said.

This sudden elevation change happens in the same place many meteorologists have noticed something odd about Austin-bound storm systems.

The invisible dome

Spectrum meteorologist Dan Robertson said he has long noticed a pattern when observing storms headed to Austin from the west.

"It’s quite clear that the storms often come tearing up to the Balcones fault zone and then immediately fall apart as they continue eastward and then flare up again just as you get to the eastern part of Travis County into Bastrop County,” he said. “I’ve seen it dozens of times, and it's one of those things as a forecaster that makes you just want to tear your hair out.”

Robertson said the sudden change in elevation can impact a storm system as it moves over the escarpment on the way to Austin.

“As the storms track eastward and then pass over the Balcones fault, all of a sudden, those storms are now much higher off the ground than they were, and that's going to disrupt the inflow to the storms,” he said.

The inflow of a storm sucks up the warm air and moisture that help power it. The sudden elevation change disrupts inflow and causes the storm to break up as it approaches Austin.

“It's like the bottom falls out," Robertson said, "and what happens is those storms have to reorganize their inflow."

The storms reorganize east of Austin, making for some infuriating storm radar images for rain lovers in the city. Austin is in the Goldilocks zone of storm disruptions.

The legend grows

The fault’s impact on eastbound storms may have led to residents' distrust of weather forecasts. Another local meteorologist, Avery Tomasco, said he believes there’s a psychological factor that builds on that distrust.

“Everyone seems to think they have their own personal rain dome," he said. "In their house, on their neighborhood, in their city. It can be big, it can be small, but everyone is convinced they have a rain dome."

While local weather forecasts aren't always wrong, Tomasco said, they're wrong enough to be noticeable.

“The guy said on TV, ‘Oh, it's gonna rain at your house,’ and then it doesn't. Well, that’s gonna stand out,” he said. “If that happens more than once, then suddenly it becomes a tradition. ‘Oh, there's a dome at my house. There's a dome in my neighborhood. Shun the meteorologist!’”

So, the truth sounds like its own conspiracy theory. A large rock that was formed by a now-dormant fault line causes storms to break up for long enough to skip over Austin, driving rain lovers and local meteorologists a little crazy.