Question:I am having a dispute with a friend. I always believed that the time between lighting and thunder could determine the approximate distance of the storm
front. Can you tell me if this is true. Also, I am correct to believe the distance is from the "storm front?" In other words, is storm front where the lighting is coming from?
You can determine the distance lightning is from you to some degree of accuracy
by counting the time between lightning seen and thunder heard (assuming the
thunder is unique to that lightning stroke). The reason it works is that light
moves almost instantaneously from the lightning to your eye (at the speed of
light which for most distances is in microseconds) while the thunder moves at the
speed of sound (around 770 mph). It takes about five seconds for sound to travel
a mile. Thus, counting the seconds from the time you see the lightning until hear
the thunder and dividing by five will give you the distance of the bolt in miles
(divide by 3 for distance in kilometres).
This gives you the location of that bolt which may or may not come from the
"weather front" but is a good indication when it is a line of advancing thunderstorms
replacing clear skies. If the lightning stroke is coming from high in the cloud,
the thunderhead may be closer than indicated by the counting method.
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