Thunder and Lightning

[Terry B]

Dear All
We had a big thunder storm tonight (with 13ml of rain) but I had an unusual experience during it.
On 3 occasions we had lightning very close to our house and sparks occurred inside the house. 2 lots occurred near my wife. She was cooking and sparking seemed to come from the range hood. This has a flu that goes up through our metal roof.
The 3rd episode I was just in our hall and heard an arc and a general flash. Not sure where it came from. This was not the actual lightning as this was obviously inside. Each occasion was accompanied by a sound like an arc welder. The thunder from the actual lightning occurred about 1/2 sec later.
So was my roof getting some of the lightning?
Was it dangerous?
Any ideas?

[Krazee]

Terry,

Not sure I have an explanation but a few things to think about. Old Rule of thumb: Sound travels approx 1000ft/sec (roughly 300m/s) so you should be able to get an idea of how far away the strike was. My guess it was not your house. The likely possibilities are:
(1) that lightning hit the power or phone lines and went to ground at your house via an earthed appliance
(2) or the strike was very close to your house. This raises the voltage of the earth around the strike and can cause a discharge to a remote earth, typically provided by a telephone line. This is one of the reasons that you are advised not to use a fixed line phone during a thunderstorm, especially if you are in contact with an earthed appliance.

My guess would be 1.

Geoff

[Iain]

Sounds more like a high incidence of static that can occur within an area of a storm,I have seen this occur during electric storms (no rain or clouds) in the high country.
Edit, when we lived near Beechworth we got clobbered by lightning, it appeared that it was not a direct strike but conducted through the basalt that we sat on, the strike was about 1km away but took out our phones, fax, modem etc (except the crappy Telstra cordless)

[Cliff Rogers]

I have seen this before too, not in the house but in the shed.
I would say that it wasn't hitting the power lines 'cos that causes dips in the power & if it is that close can damaged appliances & lights that are connected at the time.

Several years ago (~30) I was moving the 4wd into Dad's shed 'cos it looked like it was going to hail. I had a good view out the back door of the shed & saw the lightning bolt hit the ground less than a kilometre away.
The crash of thunder was only a fraction of a second after the flash.
My Dad & 2 of my brothers were standing on a slab of concrete in the shed & Dad was wearing boots but my brothers weren't.
One of Dad's sheep dogs was trying to climb through a hole in a wire netting fence nearby.
Both of the brothers received shocks up their legs & the dog was also shocked & flung off the fence. Dad didn't feel the shock so we are guessing that it was travelling through the ground away from the strike.(or towards it. Conventional current theory joke. )
The were lengths of steel & light railway line lying on the dirt in the shed & blue sparks jumped between them.
All the lights that were on at the time blew.
The strike did not hit the power lines, it was just close enough to induce current in metal objects.

[Ianab]

1/2 second between flash and boom means the actual bolt was within 150m of you

Just before a lightning hit there is a high static potential between the cloud and the ground, 1,000s of volts per inch! So it is likely there was a voltage potential between your roof and the ground. Range hood connects to the roof, stove connects to the ground.

The discharges you saw are not likely to be big enough to hurt you, but they are an indication that you are likely to be hit by lightning in the next few second. Luckily the main cloud charge found an easier path to ground someplace nearby and didn't hit your house.

If you notice it again it's a good indication that you should unplug your computers and other electical equipment.. and I wouldn't use the phone while it was happening either.

Going outside with an umbrella, golf club or kite is probably unwise as well

Cheers

Ian

[Terry B]

1/2 second between flash and boom means the actual bolt was within 150m of you

Just before a lightning hit there is a high static potential between the cloud and the ground, 1,000s of volts per inch! So it is likely there was a voltage potential between your roof and the ground. Range hood connects to the roof, stove connects to the ground.

The discharges you saw are not likely to be big enough to hurt you, but they are an indication that you are likely to be hit by lightning in the next few second. Luckily the main cloud charge found an easier path to ground someplace nearby and didn't hit your house.

If you notice it again it's a good indication that you should unplug your computers and other electical equipment.. and I wouldn't use the phone while it was happening either.

Going outside with an umbrella, golf club or kite is probably unwise as well

Cheers

Ian

The storm was very close. Our house is surrounded by big trees for about 50 acres and these are regularly hit. I haven't been to look yet as I am at work but I'm sure the strikes were within 150m. The computers ets were turned off and seem to be OK. I think it was just induced charge and the house was not hit.

[Rossluck]

Gerday Terry. I spent a night in Armidale at Easter. Nice town; one of my favourites in Oz.

I experienced something similar in Mt Isa when I was mowing a lawn. There was a storm building, and I suddenly felt as if I was in a vacuum of silence, and I had a feeling of being "electric". Not being a drug taker, I knew that a lightning strike must have hit nearby, but I had this concussed feeling of silence and didn't hear any thunder. Being a basically dull sort of a person, I just kept on mowing.

Later I discovered that all of our circuit breakers had tripped. I checked with our neighbours and they told me that their power was OK, but that they'd heard a HUGE clap of thunder directly overhead.