Science: Jump-Line Warning

Tornadoes are notoriously unpredictable. It is impossible to tell, just by looking, whether a tall black cloud will merely drop a shower, or whether it will lash out with a twister. Last week the U.S. Weather Bureau was on the trail of a promising way of telling in advance which of the tall black clouds are apt to be pregnant with tornadoes.

According to Meteorologist Morris Tepper, the thing for tornado predictors to watch for is a "pressure jump." When conditions are right, as they all too frequently are in tornado regions, the air contains an "inversion," a layer whose temperature...

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