Chase Logs 2007: May 23

At 10:00am, I began tracking a line of showers developing just east of Mankato, moving slowly northeastward towards the Cities. This line gradually grew in coverage area and strength as the morning wore on, and by 1:30pm was near the Jordan/Shakopee area. Shortly before 2:00pm the NWS posted a severe thunderstorm warning for Hennepin County, and I moved outside to watch the storm cell as it skirted my work. Only seeing a fuzzy black line through the afternoon haze, I decided to run over to Dan's computer to see how the storm was progressing. As the 2:16pm reflectivity radar image came up, we spotted a possible small hook echo near Medicine Lake; velocity imagery confirmed our suspicion. After once again running outside to check on the storm, I came back in just as the NWS issued a tornado warning for Hennepin and Anoka Counties. Below are close-ups of the 2:16pm (left two images) and 2:21pm CDT reflectivity and velocity radar images from the MPX radar.

As 2:30 rolled around the skies finally darkened over Arden Hills as the anvil of the storm obscured the sun. In the distance, scud clouds emerged from the haze, racing northeastward.

Within minutes, a gust front-like feature raced overhead from the west, bring with it strong westerly winds and sporadic rain showers. The sequence of photos below document the advancement of the gust front from 2:35-2:39pm CDT. All of the photos are looking west.

A heavy squall forced Dan and I inside, but we were right back out in the thick of the storm within minutes, still looking for any signs of the Doppler detected rotation. Scouring the northwestern horizon, I spotted what looked to be an isolated rain squall over Spring Lake Park. Since this was roughly in the area of possible rotation, I snapped half a dozen photos of it before rain once again forced us into the building.

Another rain squall crept up on us and we fled inside another building on the complex, only to wander out again five minutes later. This process repeated itself several times over the course of the next hour as wave after wave of scud filled storms raced through. The next ten photos highlight two of the storms; the top five photos depict an advancing scud base around 2:50pm while the bottom five photos show more scud and a stratified base feature to the north of us just after 3:00pm.

As I drove home that afternoon between 4:30 and 5:00pm, I got to watch as lines upon lines of scud clouds were sucked up into the retreating storm complex off to the northeast. At times it was an eerie sight. The photos below were taken starting at my work in Arden Hills and ending in Coon Rapids, MN.

Of course, the day would not be complete without an awesome sunset. As the sun neared its cradle in the west the last of the storm clouds broke and cast a purple glow on the landscape (pictures taken at the Anoka County Fairgrounds in Anoka).

After reviewing the storm reports from MPX the next day and learning that a downburst had occurred in Plymouth, I searched through the photos and found what appeared to be an isolated rainshaft located ahead of the main precipitation field (an example photo is below) that looked like a downburst. Upon further review of radar data and the photos themselves, I decided to forward them onto the NWS for their opinion. They said that there was a possibility of this column being the dying remains of the downburst, but there was no definitive way to tell. Oh well, onto the next storm chase. . .