Congestion collapse.
Our decision to stick around is looking better and better as time goes on. Not in terms of the hurricane’s strike probability, of course; the storm track has bent northward again, sending the eye over the ship channel (pretty much the worst case for Houston). However, the highways leading out of Houston are now so full of cars that the drive is taking hours and hours (24h at last report to Dallas), causing almost all motorists to run out of fuel and become stalled, causing the roadway to move even slower. In computer networks, we call this scenario congestion collapse: without any kind of organized back-off protocol, links can become so bogged down that the utility of the link goes exponentially to zero. [Note that reverse flow is being implemented—too late, perhaps.]