| August 19th, 2009: Minneapolis Tornado |
 |
 |
 |
|
On August 19th, 2009, our very own meteorologist Kristin Clark managed to capture amazing footage of a tornado in the Minneapolis metro area. She was at her Uptown apartment at the time this video was taken. Her parents, who are both meteorologists as well, were in town at the time. The Clarks witnessed their very first tornado together as a family of meteorologists.
It wasn’t your typical severe weather day. All morning skies were mostly cloudy with steady rain and temperatures in the 60’s. Usually, the sun needs to be out for a time to help destabilize the lower levels of the atmosphere eventually leading to strong tornado supercell storms. The Twin Cities had neither that day but there was enough rotation through a deep enough layer of the atmosphere to spin up this small, short-lived tornado. This small scale rotation in the atmosphere resulted from a little wave of low pressure (i.e. shortwave) that passed directly over the Twin Cities. The tornado touched down around 2 o’clock in the afternoon with no tornado watches/warnings issued or tornado sirens sounding. What’s the deal? Here’s the thing: Doppler radar typically has a hard time displaying smaller tornadoes. On this particular day, very heavy rain over a good portion of the area shielded any form of a classic ‘hook echo’ signature on radar. The numerous tornadoes that occurred on this day were rain-wrapped tornadoes meaning that the tornado itself was almost entirely wrapped by a shield of rain. By the way, rain-wrapped tornadoes are the most dangerous simply because you can’t see them!
If you look at the Storm Relative Velocity (SRV) above, however, the storm did indeed have good rotation. The green (or teal in the image above) colors indicate where air is moving toward the radar and red (or rose, in this case) colors where air is moving away from radar. This image shows a perfect ‘couplet’ of fast rotation within the storm.
|
It’s troubling how close this tornado came to passing through downtown Minneapolis. It certainly sends home the message that metropolitan areas aren’t immune to tornadoes. This particular tornado that ripped through south Minneapolis was rated EF 0, the weakest rating on the Enhanced Fujita Scale, and it still caused considerable damage. It just goes to show that any tornado, weak or strong, is a big deal especially when it hits a very well populated area such as the Twin Cities.