The strength of the El Niño or La Niña weather phenomenon in December can help predict the frequency of tornadoes and crop-damaging hailstorms in the southern and central Plains and parts of the South, says the Earth Institute at Columbia University. In a paper, scientists say a moderately strong La Niña, created by cooler than normal waters in the equatorial Pacific Ocean, leads to more tornadoes and hailstorms over Oklahoma, Texas and Kansas and parts of the South. El Niño, the result of warmer than normal Pacific waters, reduces the number of storms.
“We can forecast how active the spring tornado season will be based on the state of El Niño or La Niña in December or even earlier,” said lead author John Allen of the International Research Institute for Climate and Society.
Weather scientists say this is an El Niño year, “which implies that this spring will be a relatively quiet one for severe storms in the southern United States,” said the Earth Institute report. El Niño/La Niña already was known to influence rainfall and temperatures in the United States, “but spring — when most tornadoes occur in the southern United States — remained an enigma until now,” said Allen. Researchers say there are many factors involved in severe storms, not just El Niño/La Niña.