Thursday, June 2, 2011

05.21.11 Western Twin Cities MN

This day was a totally unexpected for storm chasing.  The severe risk of thunderstorms appeared to be across Iowa, and it was cool and cloudy most of the day here.  The sun did finally break out a bit during the afternoon, but it still appeared the best severe weather dynamics were in the far southwestern part of Minnesota with CAPE approaching 2,000 J/kg and the best lifting of air (most unstable air mass) with an index -6 to –8 as of 1 PM Saturday.

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By 4 PM, the temperatures had risen into the mid-70s with dewpoints near 60 at MSP.  There was a warm front draped just south of the Twin Cities with moist air surging in behind it.  This boundary was the focal point for storm development.

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By 5 PM, strong to severe storms were ongoing just west of the Twin Cities.  Around 5:30 PM, some storms forming near the town of Carver in far eastern Carver County were intensifying rapidly, and it was beginning to catch my interest very quickly.  Since they were just south-southwest of my location, I decided to go after the cell as it raced off to the north through the eastern sections of Carver County into central Hennepin County, around the Lake Minnetonka area.

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I got onto US-169 south from home and took it to Highway 41 in Chaska and drove north to Highway 5 towards Victoria. In Victoria, I took County Road 11 to get me over to Lake Minnetonka near Mound where the road intersects with Highway 7. From Highway 7, I took County Road 44 into Mound to get in position to grab some photos with my cell phone as the storm cell continued to move northward across Lake Minnetonka.

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Just after 6 PM, I stopped at Cooks Bay on the west side of Lake Minnetonka.  This bay is familiar to me as it’s one of the public launches that a friend and I use to go fishing.  Here is the radar image from 6:03 PM, showing the most intense part of the cell just to my northeast.

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At 6:04 and 6:05 PM respectively, I took these photos of what appeared to be a funnel attempting to form to my northeast over southwestern Orono.  Saw pretty rapid rotation with good inflow.  A definite sign of a mature storm.  I sat in the parking lot for a few minutes to see if this would produce a tornado.

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Here’s a closer look showing my vantage point along with NEXRAD from the same time frame – 6:03 PM.  Circled is the area of interest, which was approximately three miles away from my position.

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As the storm left my view, I headed north through Mound to attempt to stay on it through the windy roads around Lake Minnetonka.  While in Mound, I came across some large hailstones on the ground at around 6:15 PM as I took a wrong turn and hit a dead end.  At 6:00 PM, a National Weather Service observer reported two inch hail in Mound.  The hailstone in this photo I never measured, but I estimated it to be about two inches in diameter – matching the hail report sent 15 minutes earlier.  I did not report this hail for two reasons.  First, I was in a hurry to get turned around and back on course to position myself for a possible tornado.  Second, hail of the same size was already reported, which would have just duplicated efforts.

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It was one of the larger hailstones I’ve witnessed ever and thankfully I was not driving underneath this. That’s one reason why I give myself a one or two mile buffer from these storms. I’m not really interested in beating up my car. Also, hail doesn’t interest me as much as cloud formations and tornadoes.  The big pieces are neat to look at, but they’re nothing more than just ice chunks – something you can find in your freezer!

I lost a little bit of time as I was trying to get back on track and headed in the right direction.  I was traveling around the wooded areas of Lake Minnesota, I could see a rather large wall cloud lowered from the cloud base.  It was an amazing site to see.  Unfortunately, I could not find an ideal spot to take a picture of it, and it’s the only part of this chase I regret not having.  I had no idea as to whether a tornado was on the ground, and I could feel my arms shake on the steering wheel as my heart pounded faster not knowing what might be ahead.

This is a photo submitted to KARE11 that was very representative of what I saw as I drove through Orono to get on County Road 15 to eventually get on US-12 East towards I-494.  This was about as much of the wall cloud I saw as I travelled east with the many trees throughout the Lake Minnetonka area.  Only if I had a personal photo of this impressive looking structure!

Photo courtesy of KARE11

Shortly after 6:30 PM, this supercell with the ominous wall cloud moving through the west metro would spawn a brief touchdown according to spotters in the City of Medina at 6:36 PM.  A tornado warning was issued by the National Weather Service in Chanhassen at 6:37 PM:

BULLETIN - EAS ACTIVATION REQUESTED TORNADO WARNING NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 637 PM CDT SAT MAY 21 2011

THE NATIONAL WEATHER SERVICE IN THE TWIN CITIES HAS ISSUED A

* TORNADO WARNING FOR...

SOUTHWESTERN ISANTI COUNTY IN EAST CENTRAL MINNESOTA...

NORTH CENTRAL HENNEPIN COUNTY IN EAST CENTRAL MINNESOTA...

* UNTIL 700 PM CDT

* AT 636 PM CDT...TRAINED WEATHER SPOTTERS REPORTED A TORNADO NEAR NEAR MEDINA... RADAR SHOWED THE TORNADIC STORM MOVING NORTH AT 20 MPH.

Radar image below of when the tornado warning was issued at 6:37PM:

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As I heard the tornado warning issued, I decided to head towards the Maple Grove area in an attempt to intercept the Medina storm as the supercell began to drift further to the east from it’s original northern track as a result of an outflow boundary attempting to push the activity to the east and help fuel the intensity of the storms.  I took Interstate 494 north from Wayzata and exited the highway on Bass Lake Road in southern Maple Grove.  I initially went west from the off-ramp and waited out the storm from a gas station, but then I decided to find an open area to take photos and away from objects that could be projectiles in high winds like pieces of the awning over the gas pumps.  I found an empty office building parking lot (Upsher-Smith Laboratories) northeast of I-494 and Bass Lake Road, and decided to wait it out there.

The storms moved in about 10 minutes later after arriving around 6:50 PM.  Here is the radar image from 6:49 PM:

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Here are some pictures I took from Maple Grove between 6:49 PM and 6:54 PM as the storms rolled through:

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An impressive lowering of the cloud base of a wall cloud attempting to develop west-southwest of Interstate 494 and Bass Lake Road:

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Tail cloud of this whole cloud feature:

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A close up of the radar image at 6:49 PM with my position noted relative to the storm.  I was about 4 miles from the little notch that I highlighted with a black circle.

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As the storms passed to my northwest, I got back on the road and followed the storm in Anoka County along I-694.  I didn’t see anything of interest as the storms sat over the county and decided to call it a day.

This was one of the more interesting chases to date with all the different cloud features and close calls of “catching” a tornado.  Not a bad day considering the notion that I would be chasing this day left my mind at around noon.  In addition, these storms weren’t moving real fast, so it made it a lot easier to get out of the car and take photos without the fear of falling behind the storm.  Very fun chase, and I’m happy to report that there were no major injuries or damage as a result of the storms this day.

RS

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