Wisconsin Weather Update

Doppler Tornado Prediction
There are maps Meteorologists can use to determine the potential of tornado formation hours before it hits, which is when a Tornado Watch is issued, but to actually see it develop and issue a Tornado Warning, we use something called a storm relative mean radial velocity map. View the two images below to see one from August 3, 2004 when the Dells and Columbus had a brief Tornado Warning issued, and another during an Iowa tornado. The red and green on the map does not represent Christmas, as nice of a thought as that is, but it symbolizes wind speed either toward or away from the radar, which in this case is located in Green Bay. Green indicates winds coming toward the radar, and red is winds going away from the radar, which clears up the big red/green line you'll see running north/south near Green Bay.

Now, check out where both the Wisconsin Dells and Columbus are on the radar - look just northwest and northeast of Madison, which is in the southern part of the map. To determine rotation within a thunderstorm, you look for a pixel (dot) of a strong wind (color) going one way, then another pixel right next to it with a strong wind going the other way. In other words, if you can find a dark red pixel next to a dark green pixel, that indicates rotation within a thunderstorm over a small area, and a good chance a tornado may form at any time. So now when you hear a tornado warning issued from the National Weather Service, pay attention to whether they say "a tornado has been spotted" or "Doppler radar has indicated a possible tornado." If you hear the later, you now know what they've seen!