Also... that door is really heavy. It’s made of some pretty thick sheet metal welded to angle iron. That green pole holding it open is spring loaded at the bottom, or one person wouldn’t ever get it open by themselves.
I did a (very rough) calculation.
A quick search indicates you could have a delta pressure of about 100 millibars due to the tornado. That’s about 1.5 pounds per square inch. (that’s an extreme assumption but possible).
If the door is 2 ft by 6 feet, that’s 1.5 x 24 x 72 = 2592 pounds force.