Calling all meteorologists!
January 16, 2015 1:33 PM   Subscribe

We found lightning damage at our cottage that had occurred sometime in July last year, and I want see if I can figure out the date it most likely happened.

There are two weather stations about a hundred km to the NE and NW of our cottage, which indicated there were three days in July when there was thunderstorm activity around those stations. There's no weather station here. But there are weather radar maps indicating precipitation. On one day it looks like a small little occurrence passing over our area. On another there is a larger thing passing nearby but what is over our area is fairly small and a bit separate. And the third day there is a fairly large weather mass passing through the area, and we're on the edge.

Can anyone explain to me about thunderstorms and what kinds of cloud patterns would indicate a high chance of lightning? Rain doesn't always mean lightning, what other clues can I find to help narrow down what the likely day was?

Wikipedia tells me thunderstorms are associated with cumulonimbus clouds, but I don't necessarily know what I'm looking at, whether that would be a big formation or if lightning could also occur in small cloud formations.
posted by lizbunny to Science & Nature (3 answers total)
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posted by sanka at 1:41 PM on January 16, 2015 [2 favorites]

It's been a few years since I've thought about this - from what I recall - We still don't really understand lightning well:

Lightning occurs when you have a tall enough cloud (so, cumulonimbus, which are very tall) that allows for updrafts and downdrafts due to temperature differentiation. The drafts essentially shave off electrons, which creates a separation of charge - positively charged on the top, and negatively at the bottom. The negative cloud charge attracts positive charges on the ground, and if everything aligns, voila, lightning.

Radar maps show reflectivity - the warmer the colors, the more/larger the water droplets are in the area. In general, cumulonimbus often show warmer colors than smaller clouds. Lightning can occur on the edge of cumulonimbus, including positively-charged lightning. So, without seeing the images, I would hazard a guess that the third day caused your lightning.
posted by umwhat at 4:06 PM on January 16, 2015

Weather underground is a good resource for historical meteorological data. I'd start there.
posted by oceanjesse at 10:00 PM on January 16, 2015

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