Historical trivia quiz

Everybody knows that the B-29 that dropped the atomic bomb on Hiroshima was the Enola Gay, named for the mother of its pilot, Paul Tibbets. But flying ahead of the Enola Gay was another B-29, a weather reconnaissance plane. It found that the weather was perfect, and OK'ed the attack on the primary target. Had it been too cloudy for accurate targeting, they would have diverted to a secondary target.

What was the name of that aircraft?

First correct answer in the comments wins the internets for today.

Hint: This is a poker blog.