When this Winston player heard about an incoming D.Va ultimate, he acted fast to shield his teammates. He successfully jumped into the air and dropped his shield at the perfect moment for it to surround the D.Va bomb as it fell.
This is especially impressive when you realize that the Winston bubble and D.Va shield are not moving at the same rate and the Winston had to time his bubble perfectly while he jumped into the air. You can see him turn around to see if he managed to do it right at the end.
In Overwatch, protecting teammates from an enemy's ultimate is a special skill among tank players. Many people criticize the Winston bubble because it isn't as powerful and a Reinhardt or Orisa shield, but this Winston proves that it can be even better. His shield blocks his teammates anywhere on the map instead of the ones standing behind him.
Not every Winston player can pull off what this one did. Some struggle to even land their jumps correctly.