Storms.

Early this morning (read 3:45 am) I awoke to something that looked like this...

Photo courtesy of the Weather Network..
last night's storm, but I didn't grab my camera.

Obviously my view was a little different (a mostly empty field out to the highway), but the lightning and thunder were intense! The entire house would rattle almost immediately after lightning illuminated the entire room through the tiny gaps in my curtains. Rain was thundering down. There was even some hail, which devastated my poor herbs (mostly the oregano and basil.. the mint and bergamot seem to be okay).

At one point, I was sitting on my living room couch looking out the window (sleep was clearly not an option) when a huge branch of lightning crashed down, hitting something on the other side of the highway (maybe 1 km away) and almost immediately there was bone-rattling thunder and all the street lights went out.

One of the things I love about those kind of power outtages is that they eliminate a lot of light pollution, and allow you to see the weather for what it really is.

Lightning is caused by a build up in electrical charge in the atmosphere. Storms contain high winds that circulate air quickly, causing air molecules and small hail and water drops to rub against each other, charging them. Air is a very good insulator (doesn't allow current to flow), so good in fact that a huge amount of charge can build up before it releases. When it does release, the lightning doesn't go directly down. Since the air is still an insulator, the lightning first moves down in small steps, seeking the path of least resistance. This is what gives lightning it's jagged appearamce (the branches are called stepped leaders). However, since electricity moves at approximately 50,000 km per second, and the speed of light is 300 000 km per second, it appears to the human eye as an instantaneous process.

Thunder, on the other hand, often has a noticable delay (depending on how far away you are). When lightning strikes, it heats the air up to temperatures that can exceed the surface of the sun, and when air is heated, it expands. The expansion of air causes a pressure wave, which we preceive as sound (a nice deep boom). This pressure wave travels at a much slower speed than the lightning strike (the speed of sound is a much more sedate 350 metres per second), so we see that nice delay. Just like dominoes have a delay when the first is pushed to the last falling down, air molecules take time to bump into each other, and the distance to the lightning strike can be roughly measured by counting the time between the lightning and the thunder.

The storm last night offered very few opportunities to count... you'd barely get to the "one" in "one one thousand" before the reverberating boom!

Numbers referenced from my University text: Weather Studies: Introduction to Atmospheric Science, by Joseph M. Moran.