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No Lightning
Tue Nov 30, 2004
Listen in RealAudio 
The West Coast states Washington and Oregon are renowned for rain, and most of
California, of course, for just the opposite -- but one meteorological feature common to
all three West Coast states is a scarcity of lightning. Hi, I'm Bryan Yeaton and this is
The Weather Notebook.
Let's compare the amount of thunderstorms and lightning in the three West Coast
states to the state with the most thunderstorms, Florida. In Florida, on average, there's
a thunderstorm somewhere in the state 200 days every year. Washington, Oregon and
California, have only about 5 or 10 days reporting a thunderstorm with lightning. Why is
this? Well, to brew a decent thunderstorm you need three key ingredients -- a source of
moisture, cold airway up high, so that warm air near the surface can rise, and a
mechanism that forces that air to rise rapidly -- and seldom do these conditions
coincide on the West Coast. Blame it on the Pacific Ocean.
Pacific water temperatures are too cool, even at the height of summer, to allow air
masses passing over to pick up all that much moisture -- so that kills the first
ingredient in the stew. The Pacific also puts a damper on the ability for air to rise by
breeding a shallow layer of cool, stable air that hovers near the surface, with no hope
of rising quickly. Even when thunderstorms do hit the West Coast -- most commonly in
the fall and spring -- they tend to be wimpy, one-clap affairs with cloud tops max-ing out
at 15 to 20 thousand feet, whereas a classic Midwestern thunderhead can tower to 60
thousand feet, punching clear into the stratosphere.
Thanks to Seattle writer David Laskin. The Weather Notebook is underwritten by
Subaru of America. We are a program of the Mount Washington Observatory, online at
www.mountwashington.org.
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