NWS storm reports show severe weather events clustered around the Twin Cities.
They don’t teach you this stuff in meteorology school.
Wednesday’s severe weather and tornado event was highly unusual. This was far from your classic textbook severe weather day. Here’s why.
-A potent upper level low was producing rain in the area. A smaller mini low or “vortex” rotated around the larger parent low right over the Twin Cities around 2pm. This mini vortex triggered the tornadoes that hit the metro.
-This was a “non-supercell” type event. There were not classic individual supercell thunderstorms marching toward the metro as is usually the case with tornado outbreaks.
-There was no clearing to cause surface heating.
-There was very little lightning with these storms.
The unusual synoptic situation did not signal a classic severe weather day. As a result there was:
-No Storm Prediction Center (SPC) risk area for the metro. That means the best severe weather minds in Norman, Oklahoma did not see this one coming.
-No severe thunderstorm or tornado watch was posted for the area.
-No warnings issued before the first (likely to be confirmed today) tornado touchdown in south Minneapolis.
-No sirens sounded in Minneapolis before the first twister.
The Twin Cities NWS did do an excellent job of reacting once the first tornado was sighted. I believe all subsequent tornado touchdowns were covered by tornado warnings after the first event.
The event then evloved into a non-tornadic high wind event for Duluth. It was remarkable in that the system resembled a mini hurricane at times. NWS Duluth even noted an “eye-like structure” and “spiral rain bands” in the description of the high wind warning.
In 25 years of watching weather professionally I have never seen a day exactly like Wednesday. It’s amazing how things can come together in unusual ways to trigger severe weather events. Wednesday was likely a once in a lifetime severe weather event.