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LightningStrikes an Odd Pattern Over the Plains

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see captionJan 4, 2000: Where there's lightning, many people worry that tornadoes may follow. Lightning is associated with energetic storms since it takes large upward movements of air - plus water in various forms including raindrops and ice crystals - to produce a large electric potential.

Right: This map depicts the ratio of cloud-to-cloud lightning to cloud-to-ground lightning over the continental United States. The red areas show where the ratio is as high as 10 cloud-to-cloud strikes for every ground strike. Blue areas indicate ratios as low as 1:1. Links to 911x650-pixel, 300KB JPG. Or, click here for 212KB Acrobat PDF version that can be edited in Illustrator. Credit: Dennis Boccippio, NASA/Marshall.

When the potential becomes great enough, electricity punches its way through air that normal insulates and builds a narrow bridge of electrified gas or plasma. The current burrows its way in search of an oppositely charged region where the imbalance can be relieved. When the two are joined, current flows freely and ionizes even more air on its path, thus creating the glowing hydra

that we see as a lightning bolt. The heated air expands and, when the discharge is suddenly stopped, it slams back together to produce the thunderclap.

The feeling that many people have about lightning and tornadoes is gradually getting scientific support. The latest find is that storms with far more cloud-to-cloud lightning than cloud-to-ground are more energetic and are more likely to produce violent storms.

"The really interesting area is the Great Plains region where the ratio goes as high as 10-to-1," said Dr. Dennis Boccippio of the Global Hydrology and Climate Center, affiliated with NASA's Marshall Space Flight Center in Huntsville, Ala.

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