A record amount of tornadoes hit northeast WI.
A record amount of tornadoes hit Sunday evening, with the preliminary count of 7 in the northeast, and around 10 statewide. This includes one EF3 tornado with winds to 140 mph. The severe thunderstorms not only produced around 10 tornadoes over WI, they also produced straight line winds of over 80 mph and hail up to 3 inches. This was part of the same weather system that originally looked like it would also hit the greater Chicago metro area. Luckily, the main thunderstorms moved to our north.
Fortunately, no deaths have been reported from the storms due to early warnings from the National Weather Service. You can read further details from the Green Bay NWS office here, and the La Crosse NWS office here.
I have included two radar pictures taken while the storms were moving through WI in the evening. The first picture, base reflectivity, shows a classic supercell thunderstorm (storm with a rotating updraft). The radar picture shows in the inflow area on the south side of the storm, the figure 6 or “hook ehco” look at the southwest part of the storm. This is due the rear flank downdraft coming down and then around back into the storm. This makes a 6 looking pattern.
The next picture is a base velocity pattern. This shows the wind circulation in the storm. Green/blue colors are winds blowing toward the radar to the upper right in the picture, red/orange are winds blowing away from the radar. Where you see bright red next to bright blue, that is the circulation or rotation center in the storm. This tight color pattern is the radar indication of a strong rotation in the thunderstorm cloud. This rotation extends up many thousands of feet into the cloud.
When a meteorologist sees this rotation pattern, or “mesocyclone”, he/she will issue a tornado warning if other certain tornado producing shear patterns are present in the atmosphere. The radar is NOT showing the tornado. The tornado itself is way too small and too far from the radar to be seen. What the radar is showing is the parent cloud circulation (mesocyclone) which is a few miles across. From this parent cloud circulation, a much smaller tornado “may” form if other atmospheric conditions are just right within a few thousand feet of the ground. These critical atmospheric conditions can not be detected by radar.
There is absolutely no guarantee a tornado is present or will form. Less than 40% of these circulations in the cloud lead to tornado formation. Unless a trained spotter is actually reporting a tornado, the meteorologist looking at the radar has no idea if one is actually present or will form. A tornado warning is actually an “educated guess” that one “may” actually form or be present. The exact mechanics of tornado formation, and the exact atmospheric conditions needed in the lowest few thousand feet is still not totally understood or known by scientists, that is why so much research is ongoing. This is a reason trained reliable spotters are so critical to the tornado warning process.
In this case, an actual EF1 tornado was on the ground at the time of the picture. The NWS meteorologist does not actually know this until a spotter reports it. In this case, spotters were close to the storm and reported it to the NWS. Without the NWS warning, there probably would have been a loss of life since no one would know the tornaod was coming. Congress is proposing cuts in funds to support the NWS. Offices may be closed, your life will be threatened if these cuts are made. Something to think about when you hear/read someone say cut spending. Some of that “spending” may save your life.
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