September 13, 2012

Lightning is frightening

LIGHTNING IS ONE of the most frightening things I’ve faced at sea. For me, it’s the equivalent of instantaneous death. From the first sight of those ominous cumulus clouds piling up on the windward horizon, it’s all angst and high drama. I know there will be no escaping from screaming wind, high waves, stinging rain, the crash of thunder, and lightning bolts crackling like the furnace of hell. The air will be filled with the smell of ozone. If it’s night--and thunderstorms are frequent at night on the deepsea tradewind routes--the stark outlines of strobe-like flashes will turn everything into blinding whiteness or stygian black in turns, and my night sight will be destroyed. I hate thunderstorms.

There is a lot that we still don’t understand about lightning, but it’s generally agreed that it’s the discharge of static electricity from one part of the thundercloud to another, between different clouds, or between a cloud and the Earth or a terrestrial object.

How does static electricity build up in clouds? They say  it’s just particles rubbing against each other, just as you can build up a static charge by scuffing your socks across an acrylic carpet. Enormous energy is created in cumulus clouds. They rise to great heights, creating areas of positive and negative ions separated by vast distances.

Air normally doesn’t conduct electricity, but when the potential voltage rises high enough, lighting will force its way through. A lightning flash may have an electrical potential of 30 million volts and a current flow of 100,000 amps. It’s hard even to begin imagining the sort of destructive power those figures represent.

Sometimes 100 or more individual discharges may be needed to find a path between areas of opposite polarity, and when this “leader stroke” reaches its destination, the heavy “main stroke” flashes off in the opposite direction--that’s the visible lightning.

When you’re on land, they warn you not to take shelter under a tree during a thunderstorm. That’s a dangerous place to be in, because the tree’s height makes it more likely to be struck. So what are your chances when you’re on the water, with a metal mast sticking up higher than anything else around?

Well, according to claims made to the insurance department of the BoatU.S. organization, an auxiliary sailboat has a 6-in-1,000 chance of being hit by lightning in a thunderstorm in any given year. Here are the odds for other types of boats: multihull sailboats, 5 in 1,000; trawlers, 3 in 1,000; pure sailboats, 2 in 1,000; cruisers, 1 in 1,000; runabouts, 1 in 5,000.

About 100 people are killed by lightning annually in the United States, and many are injured. Lightning starts some 75,000 forest fires a year in this country, and maybe more in this year of extra-dry weather.

Lightning is a weather phenomenon I could well do without.

Today’s Thought
I saw the lightning’s gleaming rod
Reach forth and write upon the sky
The awful autograph of God.
--Joaquin Miller, The Ship in the Desert.

The luckiest man is the one who has a wife and an outboard motor that both work.

(Drop by every Monday, Wednesday, Friday for a new Mainly about Boats column.)

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