There's a NASA report on the two launches. It has some pictures, but the on-web copy of them has poor scan quality:
But there's a lot of interesting discussion of what's happening.
There's extensive discussion of both radio and radar observations. Although the press coverage mentioned "lightning", the result of the analysis differs:
The injection of the water created a large perturbation of the Ionosphere. This perturbation produced extensive electromagnetic effects. These effects include both emissions of electromagnetic radiation at selected frequencies and attenuations of transmitted signals. No evidence was obtained of any significant (lightning-like) electrical discharges or other broad bandwidth emissions.
Perhaps more unexpected:
The combined optical, ELF-VLF and radar data provides conclusive evidence that a fire developed aboard the tankage section of the SA-3 vehicle fol!owing Project High Water.
The vehicle was carrying water, not fuel or oxidizer, and still managed to catch fire after it was blown up. Unfortunately, there's not much more detail on the fire itself, just the evidence for it.