June 10th, 2015 Large Hail and Supercell

A "day before the day" that ended up being "the day" across portions of Illinois. The event wasn't very highly anticipated even with extreme CAPE values because of lacking wind shear.

Tornadoes: 0

Largest Hail: 2"

Highest Wind Gust: 30-40 mph (estimated)

SPC went with a Slight Risk through the day, with 15% wind/hail probabilities and less than 2% tornado probs.

Lots of instability was in place this day, with surface based CAPE values exceeding 5000 j/kg in many areas. Shear was lacking, which was expected to be the main limiting factor of the day. There was a front coming in from the north, which had lots of agitated cumulus along it for much of the afternoon.

At about this time SPC put out an MD but didn't end up issuing a watch. I stood outside my house watching the cu field to see if anything got going. Indeed it did. Explosively, in fact, and I had a front row seat.

A (VERY) cool 1 minute high resolution satellite loop of the rapid development of these storms is available HERE.

It didn't take more than 30 minutes for it to go from TCu to severe thunderstorm dropping severe hail. Several reports of quarter to half dollar sized hail started coming in near Hennepin, about 7 miles to my west, as I took these photos:

That's the power of extreme instability. We headed out the door with intentions to drive right into the core of the beast. VIL was maxed out.

We headed west from McNabb into the core. A very notable increase in CGs was noted and I was afraid our vehicle would get struck. In between loud CRACKs of thunder, we heard the first bang on the roof of the car. Hail. It become more and more frequent until we pulled into a farm driveway to stop. Many of those things were golf ball sized, some larger. This was my first time seeing hail nearly that large. In the middle of the hailstorm I decided I wanted to grab a couple of the biggest stones before they melted, so I ran out into the grinder and picked two up. Very luckily, the biggest stones to hit me were about quarter or half dollar sized (which still hurt). Here's a photo of the two biggest stones I could find that were within a reasonable distance of the vehicle. I knew there had to be some bigger ones out there, but I enjoy having my skull intact. The bigger one was about 2" in diameter and had melted a little bit.

We followed the core into McNabb where it finally dropped its last hail as the storm fell prey to another cell to its south. Noting that cell had some decent rotation, we raced south ahead of its core. At one point radar looked like there could be up to maybe tennis balls in the core, and I didn't want to be there. The storm also went tornado warned as we approached. We headed west from Washburn as a nice wall cloud was very evident. Sirens were wailing as this photo was taken.

This wall cloud very quickly dissipated and the tornado warning was dropped. Radar presentation was less than impressive, but a new less well-defined circulation showed up on radar to the west of the old one. This developed into a wall cloud with some impressive rising motion at times and broad rotation. The structure though was amazing, especially for Illinois.

Also shot some cell phone video of it.

Eventually this weakened and became a big rainy mess. We headed home from there. There were some neat mammatus, and it would've been an awe-inspiring display had low clouds not been in the way. Still, there were some neat views underneath the anvil through the evening.

The anvil crawler display was also amazing. It was so frequent I was able to capture some less than impressive bolts on my phone's camera. My Canon camera died before I could get any really good shots, but I did get some anvil crawlers in the frame.

Overall it was a very satisfying day. I never expected anything very organized to develop and what did end up happening was a very pleasant surprise. Got some great action, some great storms, and some great photos/video. And a few hail dents to boot!