A cyclone at the Cyclone game on Nov. 12 2005 -- a near-miss worst case scenario

On November 12, 2005, a series of tornadic supercells developed in central Iowa only a few hours preceding the 6 pm kickoff of a college football game between the Iowa State Cyclones and the Colorado Buffaloes. Early forecasts indicated a risk of severe weather, but a relatively low threat of tornadoes. However, the tornado threat appeared to be enhanced by a differential heating gradient that developed during the afternoon between an overcast region in central Iowa that was affected by showers through the early afternoon and an area of clear skies that developed near the dry line to the west. High resolution (4 km) WRF runs support the idea that this differential heating gradient enhanced the backing of surface winds in central Iowa, allowing for the touchdown of several F2 tornadoes.

In addition to the interesting role of mesoscale features in the tornado outbreak, the event was noteworthy because it posed a difficult challenge for emergency management officials as over 50,000 fans were already tailgating outside the football stadium as the tornadoes began touching down less than 20 miles upstream. The Iowa Environmental Mesonet played a crucial role in conveying the seriousness of the situation, with web cameras at two different sites offering live footage of two different tornadoes to television and internet viewers. Emergency planning and procedures implemented by officials throughout the day will be discussed. On the positive side, safety personnel printed up 6,000 fliers that morning which were distributed to tell fans about the severe weather risk and the procedures to follow should severe weather occur. Also, several large buildings within a 10 minute walk of the rather isolated stadium were unlocked early in the day to serve as possible shelters. An estimated 15,000 or more fans took shelter in these buildings when the stadium was evacuated 70 minutes prior to kickoff as a tornado passed 3 miles northwest. On the negative side, the evacuation was ordered only 10 minutes before the closest encounter of the tornado, and the vast majority of fans remained unsheltered outdoors.