Andrew Revering
Owatonna, MN August 21, 2001
Tuesday looked like an on again, off again storm chase day with excellent shear but a very strong cap. My thoughts were best placed over the Marshall and Montevideo areas. Peggy picked me up at about 12:15 and we headed south to Mankato. Seeing a clearing area, some better dew points, lower pressure and whatnot further to our west we decided to head in that direction. From there we went SouthWest and then back north to New Ulm by 3:45 p.m. Unfortunately after looking around for our supposed clear air we found nothing but low stratus and rain showers. A look at data at 5:00 p.m. indicated the whole area was growing in arial coverage with these puny showers. Satellite and radar data suggested we head closer to around Mason City, IA.

Playing phone tag with Kenny, Colin, and Josh we were able to meet up with Colin, Josh and his girlfriend (sorry I forgot her name) in Albert Lea around 5:30 p.m. As always it's great to hook up with chasers and do it as a team.

Still with nothing but strato-cumulus type cloud cover and the occasional spritz we saw no signs of life in the sky. At one point along the road we saw some mammatous and a neat looking low level smooth shelf looking thing that looking like nothing more than some trapped moisture condensing into a smooth cloud, but nonetheless it was neat.

After looking at some satellite, radar, and current condition data we decided to head towards the area between Mason City and Clarion, IA. It was 74-75 degrees the whole way while Clarion which was about 15 miles to our west reported 82 or so with a 75 degree dew point. So there definitely was a boundary in the area. Here is where we sat, about 15 miles due east of Clarion, IA around 7:45 p.m. We thought waiting here would be a good opportunity for a group photo.

Before too long we decided we had about 20 minutes until sunset and opted to follow a developing shower to our north near Mason City. We followed that north but to no avail. It was a bust at this point (or so we thought) so we stopped and had a leisure dinner at Perkins in Albert Lea from roughly 9:00 to 10:00.

Peggy and I went our way heading back home, and the rest of the group went their seperate ways. So from here on out Peggy and I were on our own. About the time we got half way between Albert Lea and Owatonna we began to see some incredible lightning, so I connected to the Internet and downloaded radar. This is when we found a nice sized cell had developed over Steele county around 10:30 p.m. and was moving at a pretty good clip to the ENE.

We went into Owatonna and headed east on 14. Here we tried to head north on I believe it was 56 but ran into construction. So we maneuvered around the construction the best we could and while doing so we were able to spot several very distinct wall clouds near the town of Claremont, MN in western Dodge county around 11:18 p.m.

Of course all of our storm structure is being defined by waiting for lightning strikes to light up the structure. Fortunately for us the lightning was absolutely incredible. One bolt after another, cloud to cloud, cloud to ground, anvil zits, etc. The entire area was lit up with a constant barrage of lightning strikes. It was wonderful.

As we moved further east we were able to catch 57 north which took us through Dodge and into SW Goodhue county. While traveling this stretch we noticed a nice downburst causing a very distinct rain foot on a cell to our north. We were afraid we would run into this and hit some high winds but we were spared. The city of Wannamingo, MN was not. When we rolled through the downburst left a trail behind it of flash flooding. Rapidly moving street flooding at least 6" deep filled the edges of the streets and covered at least one intersection with ponding water.

Further down the road as we stopped near the town of Hader at the 57/52 junction we watched the spectacular lightning show and also watched what I have never seen before... wet microbursts, at least two from the same cell i n a row. The first one we could see in the middle of the rain shaft it bowed outward... the "water balloon" effect as the gush of rain dropped out of the storm like... um... a water balloon. Minutes later it happened again. It was an incredible thing to watch and even more incredible that the lightning was still constant enough for us to view the whole thing.

After a bit of attempting to video tape the storm, we decided that our chase had been taking its toll on us and opted to head further north towards home. While doing so we ran into the core of another developing cell to add to the cluster. Pea to marble sized hail fell for a short time as waves of intense rain pounded Peggy's vehicle limiting visibility to about 100 feet or so for a few seconds. We got through that ok and headed back.

All told we drove around 600 miles and 14 hours just to end up 1 county south of where I live for the storm. It was well worth it I think as yet another seemingly bust chases turns out to be one of the better ones. We saw just about everything there is to see, except a tornado, all in the dark. You can't ask for much more than that (except maybe a tornado, and sunlight).


The storms formed north of the warm front in an area blanketed by clouds all day long, far east of the low in temperatures around 70-75 and dew points in the upper 60s. They key ingredients for these storms were intense directional shear. The following are the 00z 8/22 sounding parameters from Minneapolis. * indicates "good" values:

CAPE: 594
Lifted Index: -1.51
EHI: 0.59
BRN: 6
Sweat: 303
Thompson Index: 36
Showalter 0.19
*Vertical Totals 31.3
Cross Totals 17.3
Total Totals 48.6
Energy Index -0.07
*K Index 34.7
Temperature 70
Convective Temperature 97
*Precipitable Water 1.61
*Surface Dew Point 68
*850 MB Dew Point 47
Low Level Humidity 66
Upper Level Humidity 83
*Wet Bulb Zero 13,456'
*LFC 647
CCL 733
*LCL 842
*EL 37,493'
*Helicity 167
Maximum UVV 34
*Low Level Shear 50
*Mid Level Shear 85
Upper Level Shear 5
Surface Speed 6
850mb Speed 15
500mb Speed 23
300mb Speed 38
Lapse Rate 6.51
CIN 411
Cap Strength 7.40

To me what this is saying is that an intense amount of moisture (see precipitable water & dew point) was lifted a ways (see low level and mid level shear) and just dropped. Thus the downbursts, flooding & hail. Of course other items such as dry upper air helped the formation of hail and other features of this system. The strong cap is what prevented the cells from developing before dark.