An air burst can happen on a tower. You can see it is a tower shot by the bulges in the fireball because the charge runs faster down the supporting cables. The useful feature of an airburst is the shockwave and its reflection from the ground should combine just above the ground to form a Mach stem. This gives a single, horizontally moving nearly-cylindrical shockwave with more oomph to it for knocking over buildings. If you were going to have a fifties’-style city-leveller, then that’s how it works.
The fireball will typically detach and rise in a suitably photogenic manner. However, if it touches the ground, it is unlikely to find anything it can damage any further. I don’t think touching the ground is a big deal. But, I don’t claim to know.
