Friday, May 13, 2011

05.10.11 Twin Cities MN

The Twin Cities metro area was affected by severe weather after a very unseasonably warm and record setting day for humidity readings.  This helped fuel the atmosphere for thunderstorm development.  A tornado watch was issued just before 6 PM.  I was a little surprised the Storm Prediction Center went with a tornado watch since I didn’t think the wind shear parameters were all that great near the metro.  Because it wasn’t looking like a huge outbreak, I decided not to go through the trouble of setting up a live chase stream.  In fact, I decided to chase light on the gear.  Along with my DSLR and Handycam cameras, I used a cell phone for radar, and as my primary means for submitting storm reports.


I started my chasing journey around 6:30 PM headed south on Highway 13 to catch up with some cells developing near New Prague in Scott County.  The storms were just beginning and were not really showing anything interesting other than some rain.  Headed east on Highway 19 towards Interstate 35 to head back north.  As I was traveling north on I-35 near Lakeville, there was a severe thunderstorm warning issued for the cell in Scott County for possible quarter size hail at 7:25 PM. Making my way through Scott County, all was quiet. Just some heavy rains and some small hail mixed in.  The storm was still trying to get organized from what I could see on radar and I was a little surprised to see a SVR warning on this cell.  It was one of the few SVR warnings issued by the National Weather Service (NWS) in Chanhassen that did not verify that evening – storm reports did not meet severe criteria for that particular warning.  As the cell traveled north through Shakopee into extreme eastern Carver County and western Hennepin County, the cell merged with another cell near Deephaven and traveled east through the northwest side of Eden Prairie.


In was in Eden Prairie where things began to get interesting.  This is where the larger hailstones started to fall.  Hail greater than one inch poured from the sky and laid on the road.  Vehicles stopped underneath overpasses to get out of the hail.  I stopped at a gas station off of Highway 5 and Mitchell Road to get a better look at the storms.  Here is a photo from Eden Prairie at 8:16 PM looking northeast shortly after the storm went tornado warned at 8:10 PM.  There were some low hanging clouds in the distance, but nothing that appeared to be a funnel cloud or tornado.  Saw one inch hail at this location and reported it to the National Weather Service via eSpotter.


I followed this tornado warned storm through Eden Prairie into Bloomington and eventually St. Louis Park on Interstate 494 and Highway 100.  Traveling north on Highway 100, I saw a funnel to the northwest of my location shortly after 8:30 PM as I was on the off-ramp to Excelsior Blvd.  At 8:30 PM, a spotter reported a funnel cloud near Highway 169 and Excelsior Blvd and I believe this was the same funnel I was looking at.  Unfortunately, I was stuck at a long stop light trying to get onto a side street where I could stop and take photos.  The joy of storm chasing in the Cities!  By the time I got stopped and got the camera ready, the funnel was out of my view.  Here are some photos of the tail end of an apparent wall cloud over St. Louis Park from 8:32 PM where I saw the funnel minutes earlier.  If something was going to drop from the clouds, it was going to be at this spot.  In the foreground is Highway 100.  The storm also produced some of the most beautiful mammatus clouds I’ve ever seen, which is seen here on the far right side of the first photo.


I continued to follow the storm north on Highway 100 to Highway 55 east into Minneapolis towards Target Field, home of the Minnesota Twins.  The Twins were hosting the Detroit Tigers and this was setting up to be a dangerous situation with 40,000 fans inside the ballpark.  I was behind the storm and could not see any more evidence of a severe storm, but large hail, nearly half dollar size, was witnessed at Target Field around 8:35 PM.  Once I reached Target Field, I decided to call it a day and head home as the storm cell began to weaken as it moved northeastward and I was losing daylight.

I did not notice a lot of wind associated with the storm cell that tracked over Minneapolis from Eden Prairie.  This storms were inflow dominate and produced towering vertical cumulonimbus clouds.  The strength of the updraft is tied to the size of the hail.  The longer the updraft keeps the hail floating aloft, the larger the hail gets before the updraft can no longer support the weight of the hail and falls towards the ground.  The NWS put together hail tracks from the storms that moved over the Twin Cities metro based on radar reflectivity.  There are two distinct storm tracks.  One from Chanhassen to downtown Minneapolis, and a second from near St. Michael over to Isanti.  The St. Michael storm did produce a brief tornado three miles long from Hanover to St. Michael, rated an EF-1 with top winds at 90 MPH.  One neighborhood suffered damage west of downtown St. Michael.


Additional text listing of storm reports from the day can be found here.  Here is a graphical depiction of storm reports.  As you can see, the hail reports match the estimated hail track from NWS radar.


Here is a GPS summary of my storm chasing journey for the day.  Starting from my home in Shakopee and finishing in Minneapolis.  It was a nice local chase that materialized based on my forecast of storm development around 7 PM for the Twin Cities.  Being close to home made it easier to stomach the price of gas versus my previous chase in Wisconsin a month ago, which was a disappointing bust.


We had our first severe weather outbreak across the Twin Cities metro and surrounding areas, our first tornado watch, and our first tornado report for the year.  I’m just grateful the storms were not worse over Minneapolis. That could have been a terrible situation with all the people at Target Field to watch the baseball game.  Had the storm that tracked from across the southwest metro been tornadic, downtown Minneapolis as well as Target Field would have taken a direct hit.  That was the biggest positive that came out of this for me.

Total Reports: 1 (1” hail in Eden Prairie)


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