Thursday, August 13, 2009
Lightning, the "Crouch", and Joan Baez
I got a call yesterday from one of the organizers of the Joan Baez concert at the Woodland Park Zoo that was held tonight in Seattle. He was worried--the National Weather Service was forecasting showers and thunderstorms during the evening. Thousands of people would be out in the open...with the concert venue in a field surrounding by tall trees and the space filled with metal towers for lighting, sound, and other needs. (Sounds like the scene of some disaster movie!).
How could he keep these people safe? How could they tell whether lightning was approaching? The National Weather Service forecast was for showers and some lightning rolled in late in the afternoon. Their forecast was excellent and the concert started out on the damp side with lots of showers.
Here are some of the things I told him. If you are outdoors in lightning and can't get to safety you need to do two things. First, get away from any tall object--it will attract the lighting. Trees, towers, hills, you name it. It doesn't have to be metal. Just tall. Get at least 100 ft away if you can. Why? Well if lightning hits an object..lets say a tree, the current can reach the ground and spread out along the surface..and can kill up to 50-100 ft away if you are laying on the ground. Or the lightning can jump from a branch directly to you. So keep away from trees. (this was made very real to me while I was an undergrad at Cornell. There was a thunderstorm and a bunch of students gathered under its branches. Lightning hit the tree and most were stunned and several were very seriously, if not permanently, injured).
The second thing to do..the LIGHTNING CROUCH (see above figures). You don't want to lie on the ground..that could be deadly if lightning-induced currents are flowing on the surface. So what you do is to crouch down on your knees with your ankles touching. You can understand why you want to be low...less attractive to lightning, which likes high stuff. By keeping your ankles together, lightning currents riding up one foot will probably pass down the other..thus sparing your vital organs.
It is also recommended that you cover your ears to protect them from the loud sound of thunder. (I know this looks kind of ridiculous, but it works). And if you playing golf--PLEASE--get rid of those clubs and your fancy meta- cleated golf shoes.
I told the concert organizer that if I line of thunderstorms approached it would be best if people retreated to their cars. Cars are very safe...and NOT because they have rubber tires. It is because you are in a cage of metal and the lightning currents will pass around you (I would avoid touching the frame during the storm though).
And keep in mind that lightning can, and often does, strike the same place twice.
When in a thunderstorm you can tell how far the lightning bolt is by counting from the time of seeing the lightning to hearing the clap of thunder...for every 5 seconds you count, the lightning is 1 mile away. 20 second..4 miles distant. You see the lighting flash essentially immediately (since the speed of light is so fast), but sound travels much, much slower.
Well, enough weather safety tips... oil on the road with the first rain in my last blog and now lightning. I don't even want to discuss what happens during the first lightning storm after a dry period...just stay under your covers!
Posted by Cliff Mass at 8:31 PM