Can I overlap multiple cataclysms?

When using cooldown reduction, flickerstep, and calm before the storm, it’s possible to basically eliminate ultimate cooldowns. My question is this: Is it possible to overlap multiple cataclysms, or does each cast just replace the previous cast?

I’m pretty sure you can’t have mutiple cataclysms.
I had continuous Cataclysm with flickerstep in a previous season.

This is correct, just like you can’t have multiple hurricanes