First, even though this approach presumes the atheist would be open to believing in God if there were sufficient evidence, I’ve never been convinced that such a person would actually believe in God even if their condition was surprisingly met. I suspect they would rationalize the phenomenon away. Perhaps they would think they were on candid camera or there was some geo-gravitational anomaly that occurred that day. Either way, they’d try to find an alternative explanation. Jesus Did Many Miracles Second, Jesus performed many miracles in His day — many of them in front of His skeptics — and they still didn’t believe His claims. It’s quite possible that a modern skeptic would obstinately reject miraculous evidence today, as well. https://stream.org/must-god-prove-exists/ This article discusses what it would take for an atheist to believe that God exists. It is of the opinion that no matter the miracle or event, the atheist would look for any other possible explanation for what happened except for God. It mentions that Jesus performed many miracles when He was here and still the skeptics of His day did not believe in Him.