Storm Data and Unusual Weather Phenomena - CIG

2. F4 TORNADO TOUCHES DOWN IN SOUTH CENTRAL MINNESOTAIn an area not known for early spring tornadoes, seven tornadoes including a powerful F4 tornado, (windspeed of 207 - 260 mph on the Fujita Scale) struck the northern plains. On March 29, 1998, a surface lowpressure area was located in eastern South Dakota with an associated warm front extending eastward intoWisconsin. A thunderstorm complex developed near Sioux Falls, SD during the early afternoon hours andmoved east into Minnesota, producing large hail. The thunderstorm cells produced a series of smalltornadoes prior to producing an F3 tornado at 3:50 PM CST, 7 miles east of Avoca, MN. The tornadomoved east-northeast through Cottonwood County, damaging rural farms, small towns and devastating muchof the town of Comfrey, MN. The tornado reached F4 strength before dissipating at 5:15 PM CST. Anothertornado touched down at 5:18 PM CST, producing F3 damage to the city of St. Peter and GustaviusAdolphus College. There were 2 fatalities and 21 injuries.Below Left:Left:This radar image shows a perfectexample of a well defined “hookecho”. The WSR-88D Doppler Radaridentifies the heaviest or most denserainfall with darker shades. The“hook” is a signature used by theNWS to identify possible tornadicthunderstorm cells. Tornado warningsare issued based on the hook echosignature. The NWS recorded thisimage of the hook echo on March 29at 5:22 PM CST (22:42 UTC).(Radar image courtesy of the NWS,Chanhassan, MN)Volunteer rescue workers and residents of the town of Comfrey, MN inspect the tornadodamage, shortly after the tornado passed.Below Right: A resident of the town of St. Peter, MN sifts through the debris for personal belongings.Ninety percent of the towns homes were damaged and 25% were destroyed.(All southern Minnesota tornado photographs are courtesy of the Star-Tribune, Minneapolis, MN. ©1998Special Thanks to Todd Krause, NWS, Chanhassen, MN for contributing to this story)6