LOL... that was written in 1973!
I think I read that in either a Mother Earth News book or a Farmer's Almanac way before I'd even heard of cable tv.
I always remembered it as being good for determining if there was a severe storm nearby (as if the booming thunder wasn't a warning). This was before we had weather radios or doppler radar.
It does work for severe storms if I remember correctly, but I've never tried while under a tornado warning. The thing is, you need to use an antenna, not cable or satellite. Plus, you really don't want to get hit by a power surge on your gazillion dollar plazma tv (which wouldn't work anyway since you need a NTSC receiving tv, not a ATSC because digital tvs don't actually have snow.)
Basically, if you want to try it, you'll need a portable b&w analog tv (not plugged in so you don't risk frying it on a lightning bolt). If you have an analog crt tv plugged into a good surge suppressor and bunny ears or an outdoor antenna you could try that.
From NOAA:
You may have read about a technique called "the Weller Method" of tornado detection. The idea was to be able to use your TV as a lightning detector to detect the radio waves emitted by a lightning flash, with the assumption that tornadic thunderstorms were very active lightning producers. But, not all tornadic storms produce large amounts of lightning. And, TV's are all different and have different sensitivities, and some are even made to filter out lightning signals. Plus, if you are connected to cable, it won't work. The method was found to be completely unreliable and it has mostly been abandoned.