You could think of the storm powers as a manifestation of his rage bleeding/exploding out from him. He is trying to hold himself back by focusing on healing and buffing his team. But once a storm rolls in, sometimes you just have to wait it out. His arc can be learning to live with the duality of the maelstrom of his soul with the compassion he has for his loved ones (or all of humanity), eventually coming to understand that he can use his weather based powers as a protective shield and not just a whirling battle axe, metaphorically.
The story I've been thinking of is that he was lost in his love for battle and violence until he met a Dragonborn girl who was filled with violent cravings she was terrified of (A Dragonborn Dark Urge I will play at the same time as sort of alternate reality). When he met her he finally snapped out of his cravings and started to help her, support her, give her comfort. Maybe it would work like that whenever she was around a storm would always become calmer and stars could be seen in the sky. Tempest Clerics apparently use fear as one of their tools to make people go into worship and in this case he would try to help another get over their fears and violent cravings. Growing to care for her deeply... Until one day when some pieces of shit attacked them and the violence that ensued turned her into this Slayer thing from the trailer which he ended up killing... And when she turned back he was consumed with rage and self loathing, he tried to forget about it through fighting and worship, but in the end nothing could never sate his self loathing and could never forgive himself, maybe sometimes dreaming of her being out there in the sea, somewhere where he can save her as he couldn't in reality. I was also thinking of making his Guardian be based on her and Dark Urge's on him as she in other timeline ended up killing him and she out of despair isolated herself and turned to worship of Great Old Ones so she could find a way to get away from this violence she struggles with.
I was wondering if this kind of backstory would fit with Tempest cleric. And maybe what God he would worship for it to work.
