Thats what we call them here in Texas dust devils mini tornadoes caused by the heat. I was filming so stuff on a big wide open area when I saw the drones altitude dropping rapidly. Looked up from the screen and saw the funnel about where the drone was It took it all the way down to the ground even with me giving it full throttle up. No damage the drone landed almost perfect with full up throttle. The funnel dissipated the drone went right back up no issues.