Well, it depends on what you mean by probe. If you are wishing to fly FPV (First Person View), then you must stay below 400ft, have eye contact with the drone, and you may not fly near airports. You must follow these laws and register your drone otherwise you could receive up to a $27,000 fine or up to a $250,000 fine if criminal activity is performed. Personally, I believe that you probably could do whatever the drone allows itself to do because the FAA does not have a way of monitoring how high or how far you go, but it still is a big risk to take. There are exceptions if you are a certified pilot and then you could get a 333 exemption. Otherwise the storm itself would probably blow a drone like that all over the place. What you would need would be a large FPV plane. Check out this link of a RC plane dropping probes into a tornado.
. I think this idea is very cool because of all of the photo/video possibilities. You could get angles of a tornado that you have never gotten before because the road networks where you were chasing were bad.
I have looked into this idea extensively and the only real solution around the FAA laws is to get a hot air balloon license. This could cost over $3000 of training and you have to fly once every 90 days otherwise your license expires. The setup for this type of drone is also extremely expensive. For the type of receivers, planes, and other equipment you would need would be well over $1000. However, you may not need to fly out of sight or above 400ft. You can get high enough up and close enough to the tornado that you may be able to drop a probe and let the strong inflow suck it in. It still would be extremely difficult and you would need a large plane to keep from the inflow sucking the craft right into the tornado. There has been a push recently, though, to tone down the FAA rules and we might see changes either way within the next couple years. I personally love the idea as I mentioned before and think if done properly could really obtain a lot of data not just on tornadoes, but on the whole storm structure itself.
