Central Michigan University meteorologist Leigh Orf was one of four researchers nationwide, selected from among 200 teams, invited to speak at the National Center for Supercomputing Applications conference celebrating the second birthday of its Blue Waters supercomputer.
Waters is one of the most powerful supercomputers in the world. Orf and his
research team used Blue Waters to create a first-of-its-kind, spectacular 3-D
simulation of a long-track EF5 tornado and the supercell thunderstorm that
"While our ability to predict tornadoes has improved, we still need to understand more about how storms form so that meteorologists can issue more accurate tornado warnings," Orf said. "We want to have fewer false alarms, more targeted warnings and more saved lives."
When Orf and his research colleagues examined the inner structure of the simulated thunderstorm, they discovered flow structures that had never been seen in previous simulations.
A stream of storm-generated cooled air, created primarily by the evaporation of rain, was recycled back into the storm. This persistent current of rotating air may help explain why some supercell thunderstorms spawn massive, devastating tornadoes.
"It's as if the storm generated energy from its own exhaust," Orf said. "What makes our simulation especially compelling is that the simulation bears interesting similarities to an actual storm that was observed, including tornado track length, direction, intensity and evolution, lending more credence to our result."
Orf's simulated storm produces a tornado with winds exceeding 300 miles per hour near the ground. The storm, which remains on the ground for 65 miles, was 'grown' in the same environment as that of a storm that produced a long-track EF5 tornado in Oklahoma on May 24, 2011.
Orf's research partners are Robert Wilhelmson from NCSA, Louis Wicker from the National Severe Storms Laboratory, and Bruce Lee and Catherine Findley from Windlogics.
Tornadoes are compact, powerful whirlwinds produced by differences in wind, moisture and temperature. Rated zero through five in intensity on the Enhanced Fujita Scale, or EF scale for short, EF5 tornadoes are rare. Long-track EF5 tornadoes do damage for dozens of miles and account for less than a fraction of 1 percent of all tornadoes. They are the longest-lived and most violent, packing wind speeds of more than 200 miles per hour.
Determining which storms will generate monster tornadoes, or any tornadoes at all, remains a challenge for weather forecasters, who know that better prediction will give people more time to seek shelter when a tornado is bearing down. According to the U.S. National Oceanic and Atmospheric Administration, the current average lead time for tornado warnings is 13 minutes.
"The overarching goal of this line of research is to help meteorologists better understand the mechanics of these types of devastating storms in order to ultimately get people out of their way in a more effective manner than we are able to do today," Orf said.
It took 100 terabytes of data to create visualizations in such a way that comparisons could be made to similar storms observed in the field.
"You can't do this kind of simulated research without supercomputers," Orf said. "The 20,000-core simulation that produced 100 terabytes of data couldn't have happened on other supercomputers. Blue Waters is the only one powerful enough to handle this volume of data, and to the best of our knowledge, we have created the first simulation of a supercell producing a long-track EF5 tornado because of it."
As another severe weather season approaches, Michigan Gov. Rick Snyder has declared April 12 through 18, 2015, as Severe Weather Awareness Week in Michigan. During this week, the National Weather Service is encouraging residents to review severe weather safety procedures, stay informed and be prepared.
Tornado alerts: Warnings and Watches – What's the difference?
tornado watch is issued by the National Weather Service Storm Prediction Center when weather conditions are ripe for tornadoes. When a watch is issued, residents in the affected watch area should be prepared and aware to find a sheltered location, listen for announcements, and prepare to act. Under a tornado watch, residents may get little warning of an actual funnel cloud.
tornado warning is issued when a tornado has been sighted, visually or on radar. When a warning is issued, residents in the affected area should immediately seek shelter, turn on a battery-powered radio or mobile device, and wait for additional information or an all-clear alert.