Question: When was the catastrophic EF5-rated multiple-vortex tornado struck after which the Missouri Militia members have been active in disaster relief?
Sentence (from "2011 Joplin tornado"): The 2011 Joplin tornado was a catastrophic EF5-rated multiple-vortex tornado that struck Joplin, Missouri, late in the afternoon of Sunday, May 22, 2011.
Relevant evidence: Yes