Lightning on the Summit

2014-08-15 19:41:15.000 – Mike Dorfman,  Weather Observer/IT Specialist

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Our shift change on Wednesday was a bit exciting. With torrential downpours in the forecast and winds gusting into the 80 mph range, the drive up was a bit exciting. We received a total of 2.80 inches of rain during the 13th, which totals to over a quarter of our precipitation for the month of August! Towards the tail-end of the storm, we received a strong thunderstorm with several direct strikes to the summit. With the windows cracked to hear the thunder, the summit staff waited with baited breath as the storm moved closer. Suddenly, with a flash of blue-purple, we saw a direct strike to the summit, recognizable by the not-so-thunder-like sound made as the summit was struck. Direct strikes to the summit don’t sound like a deep rumble, but instead a loud crackle, resembling the sound of a rattling metal trashcan, amplified to extreme levels. We received 5 direct strikes in total, with some of the strangest thunderstorm sounds I have ever heard. Between two strikes to the summit, I could even hear a crackling and sparking sound, indicating the charge in the railings along the deck was just about ready to jump through the air to the clouds above.

Along the same line, have you ever wondered why lightning occurs? There are several mechanisms which allow clouds to become either positively or negatively charged. The ground is also full of both negative and positive charges. Opposite charges tend to pull towards each other, so as the charged cloud travels above the ground, the opposite charge in the ground is pulled to the surface of the ground (which is called an induced charge). When the force between the positive and negative charges becomes strong enough, the charge will jump through the air in the form of lightning. If you ever see your hair stand up in a lightning storm, you are in serious trouble since this effect is caused by an intense charge building up in your body, actively pulling your hair towards the opposite-charged cloud!

Lightning rods help to lessen the chance that this dangerous lightning will hit a person or a building, and they achieve this in a couple different ways. First, they act as the most efficient pathway to ground. Since electricity would rather travel through a conductor (such as the lightning rod and the wire to the ground attached to it) than an insulator (such as your wood roof), lightning would be more likely to hit the rod. In addition, pointy objects tend to discharge more easily than blunt objects, a phenomena called Corona Discharge. This allows the air around the rod to be ionized (the air molecules become charged). This allows the charge to disperse into the atmosphere, which in turn may be pulled up into the cloud, partially neutralizing the charge in the cloud. Here is a video of this effect in action. The ionized air surrounding the rod also allows the lightning to travel through an easier path to ground via the rod since the lightning is attracted to the opposite-charged ions cloud.

While it would be interesting to investigate these effects while a thunderstorm passes overhead, always remember that lightning is extremely dangerous and very unpredictable. Whenever a storm is in your area, be sure to lessen your chances of getting struck by seeking shelter inside a building or inside a metal vehicle if there is no building nearby. As the National Weather Service says, ‘When Thunder Roars, Go Indoors.’

Mike Dorfman,  Weather Observer/IT Specialist