Waterfall in the cabin

Yesterday it was raining steady, not hard, out here on the East Cost. When I got into my '99 DII, I noticed water dripping down from the left rear of the driver's sun visor. When I hit the gas to move forward, streams of water came down into the cabin through both front seatbelt pillars (where they can be adjusted). Not so much on the passenger side, but enough on the driver's side to get the carpet quite damp.
I checked the pillars, door seals, roof rack seals, even the windscreen seals (the windscreen was replaced three weeks ago) and I cannot find any leaks. Even the headliner is bone dry.
The sunroofs were and are closed, and no leaks there either. I am completely stumped, as this is the first time this has happened and I am quite concerned.
If anyone has any idea what this could be from, please let me know ASAP, as I would like to be able to continue driving without donning a wetsuit.
Thanks.

Thor - I recently had my windscreen replaced and experienced the same thing. Turned out that the seal had a small air hole which let the rain water through. I took it back to where I had it installed and they used air compression to find it, then fixed it. I'd bet that's what's going on. Or, if you have sunroofs, the seal around the front one may be bad. Water would collect that way too.

Or you have a sunroof drain hose leaking (or it has come loose or plugged up, but that would cause a leak out of the sunroof opening), there is a drain on all 4 corners of each sunroof that connect to hoses that run down the pillars and drain onto the ground. The sunroof "seal" doesn't really seal anything, it just kinda slows the leak down so the drains can get rid of the water.

Thanks for the info, I'll check out both issues later this afternoon. First, though, I will call my dealer who installed it and ask that they look into it. If, however, it is because one of the sunroof drain hoses got loose, how do I even fix such a thing? No clue.

You can access the drain tubes by dropping the headliner (don't need to take it all the way out, it's even possible to replace the sunroofs this way. (did a bunch of them when I worked at the dealer)