The Storms of May 2008

May 2008 will go down in history as a prolific month for severe weather, and in particular, tornadoes. During the month there were three tornado outbreaks, hundreds of confirmed tornado reports, and at least 42 directly related fatalities. Tornadic storms marched across much of the eastern two-thirds of the nation, and repeatedly across the Great Plains and Upper Midwest, with reports from Texas to Minnesota and Wyoming to Virginia. There was even one confirmed EF5 – the strongest rating currently given by the National Weather Service (NWS) – occurring on May 25th in Iowa, which swept through the towns of Parkersburg and New Hartford. A radar image and photograph of this tornado are pictured above. In this month’s article, we’ll take a look back at the stormy month of May, and some of the meteorological reasons behind the wind and the fury we witnessed.

The tornadic activity during May 2008 occurred largely with three major weather events: a low pressure system that passed over the Southeast on May 1-2, a series of storms that moved over the Southern Plains and Mid-Atlantic region between May 7 and May 15, and a series of storms associated with an active weather pattern over the Great Plains and Upper Midwest between May 22 and the end of the month. Combined with an already active winter and spring, the past month has put 2008 well along the path to being a record-setting year for tornado activity. The chart below (courtesy of the SPC) shows confirmed tornado totals from the past three years and the average 10 year trend, as well as preliminary and confirmed reports thus far during 2008. The 1258 preliminary reports received as of late May already put 2008 near the 10 year annual average, with a full seven months left in the year.

May 2008 has also been a prolific month for killer tornadoes – according to the SPC, 42 tornado-related deaths were reported within the United States during the month of May, associated with 11 different storms. The deadliest of these tornadoes occurred on May 10 in far northeastern Oklahoma and southwestern Missouri, as a supercell spawned tornadoes that caused 21 confirmed fatalities as it tracked through Ottawa, Newton, and Barry counties. Another notable killer tornado, this one an EF5, killed 7 as it tracked through the towns of Parkersburg and New Hartford, IA, but mercifully missed the major metropolitan area of Waterloo and Cedar Falls by less than a mile. It was the first F5 or EF5 tornado recorded in Iowa in more than thirty years (for those of you interested in storm trivia, the previous was the F5 Jordan tornado of 1976).

Despite the destruction and loss of life it caused, the abundance of tornadoes has provided the scientists who study tornadoes a chance to see many of them up close and personal. During these outbreaks, many teams of research meteorologists traveled throughout the plains with mobile radars, sensors, and video cameras, observing and recording tornadic storms in an effort to better understand and predict them. One such team was led by Dr. Howie Bluestein of the University of Oklahoma. Along with an entourage of graduate students, Dr. Bluestein and his mobile doppler radar traveled throughout the Great Plains this month, gathering valuable tornado observations. A photo, taken by OU graduate student Robin Tanamachi, of some of the research team and their radar truck is shown above. Mobile radar trucks, such as this one, are vital for allowing scientists to see inside tornadoes and come to understand the processes which trigger tornadoes and dictate their inner workings.

And while May 2008 was a big month for tornadoes, rain and hail also wreaked havoc over much of the central United States. Hail to the size of softballs damaged cars and windows in association with several storms during May, and copious rainfall produced major flooding. In Ames, IA (pictured above), 3 to 5 inches of rain on May 29 and 30 sent rivers and creeks more than six feet above flood stage. The flooding inundated much of the town and closed US highways 30 and 69. Looking ahead, we should, locally, be able to look forward a breather from the repeated bouts of severe weather. Climatologically speaking, June is a less active month than May in terms of tornadoes and rainfall for central Oklahoma. Still, it is not unusual to see major severe weather outbreaks in Oklahoma at any time during the summer months, so stay alert and pay attention to NWS and SPC forecasts when severe weather threatens.

Story is © Nate Snook, 2008