Pacific Ocean Temperatures Influence Strength and Location of Tornadoes

The temperature of the Pacific Ocean could help researchers predict where tornados are likely to spring up throughout the United States, researchers from the University of Missouri found.

The scientists surveyed more than 56,000 tornado-like events that occurred between 1950-2011 and found that when the Pacific Ocean was warmer than average, the United States experienced 20 percent more EF-2 and EF-5 tornadoes. EF refers to the Enhanced Fuijta scale, which rates tornadoes from zero to five based on the damage they cause.

They also discovered that when surface sea temperatures were above average, the tornados were usually located to the west and north of the area in the Midwestern part of the US known as tornado alley. When the temperatures were cooler, more tornadoes occurred in the southern states, including Alabama, Tennessee, Illinois and Indiana.

"Differences in sea temperatures influence the route of the jet stream as it passes over the Pacific and, eventually, to the United States," Laurel McCoy, an atmospheric science graduate study, said in a statement. "Tornado-producing storms usually are triggered by, and will follow, the jet stream. This helps explain why we found a rise in the number of tornados and a change in their location when sea temperatures fluctuated."

McCoy and Tony Lupo, a professor and chair of atmospheric science in the College of Agriculture, Food and Natural Resources, studied the link between tornados and the Pacific Decadal Oscillation, a climate phenomenon in which long term temperature trends can last up to 30 years.

"PDO cool phases are characterized by a cool wedge of lower than normal sea-surface ocean temperatures in the eastern Pacific and a warm horseshoe pattern of higher than normal sea-surface temperatures extending into the north, west and southern Pacific," McCoy said. "In the warm phase, which lasted from 1977 to 1999, the west Pacific Ocean became cool and the wedge in the east was warm."

More than 550 people died in 2011 due to tornados, which caused more than $28 billion in property damage, according to the National Oceanic Atmospheric Administration. Knowing where tornados are likely to strike and with what amount of force, McCoy says, could help save lives.

"Now that we know the effects of PDO cool and warm phases, weather forecasters have another tool to predict dangerous storms and inform the public of impending weather conditions," he said.