First of all, you may want to get her checked by a vet to make sure the problem isn’t an organic one-- that is, a problem with her digestive tract. You may also want to consider getting her medication for her storm anxiety. My dog has it, and it can trigger behavior problems. My vet prescribed Valuim, which I give to her before storms start. It’s done her a world of good.
If neither seems to fix the problem, then it may be a behavioral issue. Are you correcting her while she’s pooping? Rubbing her nose in it and punishing her after the fact does nothing but confuse her. It can make the problem worse in some dogs: they think you’re punishing them for defecating (regardless of location) and will try to go somewhere to hide it.
Start re-training her just like she was a puppy. Take her out frequently, praising her and giving her treats when she eliminates outdoors. Crate her when you’re not at home, or constrict her to certain rooms where you know she won’t go.
She may not consider the basement part of the house if she doesn’t spend much time down there. If she’s been kenneled lately, or learned to go on cement, she may think that’s an okay place.
Be sure to clean the spot well with bleach to remove traces of smell, because that’s one reason dogs will go back to the same spot.