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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999

FROM VOLUME 12, NUMBER 5, MAY 1999

La Nina-Tornado Link

Item #d99may52

According to a May 7, 1999, story by Joseph B. Verrengia carried on the AP wire, the National Weather Service has established a statistical link between La Niña and the incidence of tornadoes on the central Plains. By early May, Nebraska and Iowa had already experienced 17 tornadoes, 5 more than normal. La Niña produced a stronger, colder jet stream in the upper atmosphere. At the same time, warm, wet low-level air was pulled up into the Plains states from the Gulf of Mexico, an unstable combination. Most La Niñas last only a couple of months, but this one has persisted for nearly a year. During the most recent El Niño, the incidence of tornadoes was reduced by up to 24% in some regions, according to some studies.