If they are not entirely an act of punishment, then either the tornados are sent as a reward or they are an act of chance. Which?
Logical fallicy. Simply because there is no discernable cause for punishment, does not mean that weather is not simply behaving as intended (see volcano reference above).
If God sends a tornado as punishment to a deserving crowd, then those who die were given opportunity to repent. This does not preclude people from dying as a result of natural disaster simply because they happened to be in the road of bad weather. The two are not connected. However, we as limited humans cannot directly tell the difference.