Very Weak Tornado Near Germantown and A Microburst Near Union Grove Monday Afternoon (updated 1:30 pm Tue)

The showers and thunderstorms that developed along and ahead of a cold front Monday afternoon produced isolated severe weather.   

After reviewing video, in addition to a discussion with the local Germantown Police Chief and a review of witness reports on social media, we are confirming that an EF0 tornado occurred about 3 miles northeast of Germantown in Washington County, or about 18 miles north northwest of Milwaukee.  It likely developed around 2:12 PM Monday and ended just a few minutes later, or around 2:15 PM.  It appears to only be about 50 feet wide.  These are all very preliminary estimates.  NWS Warning Coordination Meteorologist Tim Halbach visited the site many times earlier today and found some broken tree branches and uprooted trees. Below are images of the damage path. The damage path for this tornado is approximately 1 mile in length. Click on the below images to view them in higher resolution.

No damage or injuries were reported.  No warnings were issued and sirens were not sounded. This tornado was extremely small and was not life threatening.

Below is what radar looked like around the time of the tornado:

At 2:09 PM: for reference, the radar is off to the bottom left of the image.  Green colors are winds moving toward the radar, red is away.  When the two colors are side by side, they indicate rotation.  In this case, the rotational velocity is only about 16kts (18 mph).  Very weak, and it's something we see frequently with many storms.  In most cases, nothing happens.

The image below is the corresponding reflectivity at 2:09 PM.  This represent the energy returned to the radar due to the intensity of the precipitation.  This storm does exhibit weak rear inflow with a trailing outflow stretching off to the north northwest. 

This is the velocity and reflectivity about 3 minutes later at 2:12 PM.  From witnesses, this was about the time the tornado touched down. Again, it lasted just a few minutes.

At 11:25 AM, 1.75 inch hail was reported from a different thunderstorm 2 miles northwest of Germantown.  No warnings were in effect when that occurred, but it prompted the issuance of a severe thunderstorm warning.

We had a report of one inch hail in Milwaukee county, 2 miles south southeast of Milwaukee at 12:15 PM.  A severe thunderstorm warning was in effect when that occurred.

A microburst took down trees and power lines in the Union Grove and Yorkville areas around 3:55 PM.  A severe thunderstorm warning was in effect. The microburst is shown in the circled area below. A microburst is a strong, localized downdraft in a thunderstorm. It can cause damage comparable to, or in some cases worse, than tornadoes. Red colors are wind away from the radar, and green colors are wind toward the radar. Notice how the red and green areas diverge over time. This indicates the strong downdraft winds are hitting the ground and then spreading outward in a circular pattern.

Davis/Marquardt