Also from South Louisiana, worst storms for my area as far as power loss/ water, were Juan, Andrew, Rita, and then several others scattered in there. Parents lost power w Andrew for 6 days. we lost for 4, many others I knew lost it for 2 wks. The reason Juan was so bad, is because just before it, we'd had Danny, and Elena, back to back. Happened like that this past year in the Lake Charles region.
In general, I'd plan on about a week without power. That also might mean that local business don't have power, so cant' use credit card machines, so have cash. Same with gas. sometimes trucks can't make it in for refills, so have gas on hand for generators. have a generator if possible.
As far as supplies: yes, water for about a week, or gatorade, or the like. Any drink that you're ok with that doesn't need refrigeration. same with food. Couple loaves of bread, whatever you can eat that doesn't need heating up or refrigeration. And for several days, not just like 2 or 3, dont' assume fast food or local places will be up and running. Just get the food y'all can tolerate for several days, that can be eaten straight from the can, or stuff like peanut butter, crackers, etc.
I agree with others, to stock the freezer with frozen jugs of ice, or something. and then don't open. Also agree to fill up bathtub with water. Often if the the power is out at water treatment plants, or for whatever reason, you can't get water, you'll need some place to draw from (not nec for drinking) for stuff like flushing toilets, or washing up.
Batteries, flashlights, etc. now have some way to charge phones, battery packs or plan to use the car. We had a small camp stove, refill or buy propane ahead of time. and prescription or whatever OTC meds you might need. and whatever pets might need. AND try and put important papers in some waterproof container. After Katrina, I knew so many folks who just put items up on furniture, but what happened during the flooding, was it either got that high, or the furniture topped over. Water proof bags, safe, etc.
My dad also had pieces of wood that fit all of our windows, stored in garage, and labeled, like 'main bathroom window,' or whatever.
They're really rare, but if I lived in So Florida, I'd be prepared.