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Stoughton Tornado - Radar

The National Weather Service used two different kinds of radar images to identify a tornado near Stoughton on August 18, 2005. "Reflectivity" radar is the kind you are used to seeing on your local television news to point out where the rain is. "Relative velocity" radar is the kind used to figure out which winds are travelling how fast toward or away from the station.

Reflectivity Radar

One of the things that suggests a tornado may be present in a thunderstorm is a "hook" of high reflectivity located away from the main body of the storm, often south-west of the storm. As seen below, the Stoughton tornado displayed such a hook.


(National Weather Service - Milwaukee/Sullivan Weather Forecast Office)

Several other storms in the area on August 18, 2005 also displayed similar hooks and spawned smaller tornados, as indicated below.


(National Weather Service - Milwaukee/Sullivan Weather Forecast Office)

Relative Velocity Radar

Relative velocity radar images make it easy to spot rotation. Where colors are bright, the wind is blowing fast. If there is a lot of one bright color (red or green) in an area, that could indicate damaging "straight line" winds. If, however, two bright colors are right next to each other (red and green), that indicates that the winds are blowing fast in multiple directions. The most likely explanation of this behavior involves a tornado. The bright red and green image below clearly displays the Stoughton tornado kicking off fast winds in all directions.


(National Weather Service - Milwaukee/Sullivan Weather Forecast Office)

That was easy, but the next image suggests why your local news affiliate doesn't usually display the "relative velocity" radar image during the newscast. To the trained eye (to the person who circled them anyway), three suspicious bright green and red spots stand out, indicating three tornados. To my untrained eye, however, there seem to be many more likely red/green candidates. (This is why it's good that I work with computers, not weather forecasts!)


(National Weather Service - Milwaukee/Sullivan Weather Forecast Office)


"www.StoughtonTornado.org" is owned by Jonathan G. Lampe This not-for-profit web site hosts a scrapbook covering the August 18, 2005 Stoughton area tornado. The photo of the tornado in the header was taken by Jerry Currie and is used with his permission. Copyright is claimed only to protect my right to publish my own (rather sparse) original content; you are free to make copies of my original content. Archived and attributed content (e.g., images and articles) may be subject to individual copyrights. Sources, attribution and original publisher are listed to the best of my ability. This site is not an official publication nor am I officially connected to the Stoughton Area Tornado Relief Fund or the Long Term Recovery Board , although I consider myself a "booster".