Multiple consecutive days of tornado activity spawn worst events

April 30, 2014 by Elizabeth K. Gardner
Credit: Lyndon State College from VORTEX2

Significant tornado outbreaks and especially strong tornadoes are more likely occur within periods of activity lasting three or more days, according to a Purdue University tornado expert.

Jeff Trapp, a professor of earth, atmospheric and planetary sciences, examined 30 years of U.S. weather records and found that an outbreak of 20 or more reported tornadoes had a 74 percent probability of occurring during a period of tornado activity lasting three or more days. During those same periods, a tornado rated 3 or higher on the Enhanced Fujita scale had a 60 percent probability of hitting.

The Enhanced Fujita scale rates tornadoes from EF0 to EF5 with damage rated as "light," including broken branches and windblown signs, to "incredible," including leveling of strong-frame houses.

"Two extreme tornado events last year led to 32 deaths, injured more than 377 and cost $2 billion in damage and inspired this study," Trapp said. "Unfortunately, the devastating tornadoes these past few days, tragically, seem to be bearing out the results."

Tornadoes swept through Arkansas, Oklahoma, Kansas, Missouri, Nebraska, Iowa and Mississippi on Sunday (April 27); Mississippi, Alabama and Tennessee on Monday (April 28); and North Carolina on Tuesday (April 29). The National Weather Service received 100 preliminary tornado reports for April 27 and 28, and multiple deaths have been attributed to the violent storm system.

Trapp also found the multiple-day periods were more likely to occur during the warm months of April through July.

"The encouraging news is that the larger, more slowly evolving and moving systems that appear to contribute to multiple-day tornado periods may be more predictable," he said. "The weather system responsible for the tornadoes this week falls in this category and was revealed in the forecast models at least five days in advance with good fidelity."

Trapp examined tornado activity entered into the National Oceanic and Atmospheric Administration's historical record of in the United States from 1983-2012, which included 3,129 tornado days and 1,406 unique periods of . Multiple-day periods made up 24 percent of the unique periods of activity.

A paper detailing his study and the results was published in the April issue of the journal Monthly Weather Review and is available online.

The idea for the research began while Trapp was participating as a lead investigator in the National Science Foundation's Mesoscale Predictability Experiment (MPEX), a national field project to improve predictions of severe .

Explore further: Landscape 'transition zones' may influence where tornadoes strike

More information: On the Significance of Multiple Consecutive Days of Tornado Activity, by Robert J. Trapp, Monthly Weather Review , 2014.

Related Stories

NWS: New tool confirmed Miss. tornado

February 16, 2013

(AP)—Officials say new technology allowed forecasters in Mississippi to quickly confirm the tornado that tore through Hattiesburg this week and alert the public.

Satellite movie shows US tornado outbreak from space

April 28, 2014

NASA has just released an animation of visible and infrared satellite data from NOAA's GOES-East satellite that shows the development and movement of the weather system that spawned tornadoes affecting seven central and southern ...

Recommended for you

Land-based microbes may be invading and harming coral reefs

March 24, 2017

A new study suggests that coral reefs—already under existential threat from global warming—may be undergoing further damage from invading bacteria and fungi coming from land-based sources, such as outfall from sewage ...

Managing bushfires for safety and biodiversity

March 24, 2017

People have long used planned fires as a tool to open up access to hunting grounds, to encourage new plant growth, and to cultivate plants for cooking, heating and spiritual purposes.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.