[Alneyan]

Do I really want to answer this question, or am I shooting myself in the leg? Hmm...

Storm damage seems to stack: a vessel with 300/350 hitpoints was destroyed in a sector with two storms (400 total damage). Storm damage is also applied all at once, so there is no "cap" on it. My vessel had a 250kt component, impossible to destroy by a single storm dealing 200 damage points, but the vessel was nonetheless destroyed. So, the damage was not 200 and then 200, but 400.

There is a probability of being damaged by storms, but I do not know how high (or how low) it is. For what it is worth, my vessel was either damaged by both storms or by neither of them, so I am thinking all storms deal damage if you are hit; it would also make more sense given the "all damage dealt by storms stack" approach. So no second saving throw if you have failed your first I guess.