There is any number of reason he could have had to turn around. I would guess weather wasnt the issue. These guys have dispatchers would take care of the weather checks, and they could have avoided storms and held to wait for better landing conditions at the destination or proceeded on to the alternate.

My guess is a maintenance issue. I have had it happen on multiple occasions... take off, see something isnt right and simply request vectors back to the airport. You dont need a change in flight plan, you simply need to ask the current controller for vectors to where you need to go. They will probably ask if you have an emergency and need assistance, but you can tell em no if you dont need it.