A one-of-a-kind combination of weather factors make the United States the twister capital of the world, with the ominous funnels 10 times more common in the states than anywhere else on the planet, scientists say and NBC News reports.
America has a permanent hold at No. 1 among tornado counters, averaging about 1,000 twisters per year, while Canada ranks second with about 100 annually, experts say.
The four main ingredients all are geographical, all unique to America's borders: a massive mountain wall to the west, a warm ocean to the southeast, a cold-air “shield” to the north – and above these particular latitudes, a narrow river of wind, the jet stream, that surges eastward at hundreds of miles per hour.
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