Thunderwaves

This is a term used for any natural disasters that have something to do with water getting out of hand and destroying anything in its path. It can encapsulate everything from a simple rain getting a little bit too intense, or intense hurricane type of storms that can level a homestead in a couple of seconds, or massive coastal waves that can do the same to any fishing village nesting nearby.
Water is seen as a vengeful force of nature. While it is essential to have it around to fascilitate the continuation of human (and animal and plant and basically almost all) life, it can also take it away at any moment it seems just a little bit displeased. And thunderwaves are seen as an expression of such displeasure. Events and disasters associated with them are considered by the new church to be the main driving force behind people still putting their faith into nature and the old gods associated with it. Some priests are trying to fight it with knowledge and teaching people that there is no reason to fear scientific and logical things that are out there, but anyone would be afraid if a giant tsunami is heading their way even if they do understand how they are formed.
There might be some other names associated with these severe and volatile weather conditions. Different regions of Avalonia might have local river or cloud dieties that are still revered and at least have a little shrine hidden somewhere deep in the forest above a little spring, to make sure that even if maybe gods are not real, they will not unleash their storms above someone still bringing them honey cakes from now and then would they?
Storms and floods, and all that they take with them, are seen by everyone as great tragedies and are among the most feared life events that may happen to anyone out there.