Impact of the May 16 tornado on the Gateway Arch

ST. LOUIS - The damage at the ground from the May 16 tornado was devastating. The EF3 tornado rampaged across the St. Louis area with winds over 150 miles per hour. But how well would the Gateway Arch stand up to a direct hit?

“Based on calculations when it was built and wind tunnel tests, it was determined that the Arch could withstand a 150-mile per hour wind and it would sway up to 18 inches in an east-west direction,” Pam Sanfilippo, Program Manager of Museum Services and Interpretation at Gateway Arch National Park, said.

There were visitors atop the Arch and others riding the trams when the tornado touched down.

“We typically keep an eye on weather. We knew there was a weather alert for that day,” Sanfilippo said. “It came in so fast. Typically, we would evacuate the top. We had a tram going up at the time that the warning came out and so we were able to get visitors secure up at the top.”

Park rangers generally sweep the grounds to bring visitors inside the underground museum during tornado warnings.

How does the Arch react to normal winds?

“On an average day, it’s not really swaying at all. But once it gets 30-40 mile per hour winds, visitors start to feel that sway just a little bit, maybe an inch or so,” Sanfilippo said.