Super Outbreak |
 Dave Thurlow, Host |
Twenty-five years ago this Saturday, America was winding up the Vietnam War when a different kind of attack occurred. The nation was bombarded by the biggest army of twisters in history. Hi, I'm Dave Thurlow from the Mount Washington Observatory and this is The Weather Notebook.
148 tornadoes touched down on April 3, 1975, between the Mississippi River and the Appalachians. All the way from Alabama to Indiana to Ontario, twister after twister dropped from the skies. North America had never seen anything like it. At the time, we didn't have Doppler radar to track this onslaught. Only conventional radar was in place around the country, and it detects rainfall, not winds. But many of these tornadoes were so potent that they wrapped curtains of rain around them. This produced what's called a hook echo that was clearly visible even on old-fashioned radar.
No matter how you slice it, this was a record-setting outbreak. If you put all of that day's tornadoes end to end, they would extend more than 2000 miles. The good news is that in 1974, we already had a high-quality warning system in place. So the death toll fell short of several other tornado outbreaks that occurred in the days before television warnings. Still, more than 300 people lost their lives on that April day in 1974. Tomorrow, we'll learn about an important finding that emerged out of the country's biggest tornado outbreak, the fact that big tornadoes can be made up of several smaller tornadoes, something called multiple vortices.
Thanks today to contributing writer Robert Henson whose work often appears in Weatherwise magazine. Call us at 888-rain-001 for more information. Our show is underwritten by Subaru, the beauty of all wheel drive, with major support provided by the National Science Foundation.