So this was a weird day! The models had hinted at some week storms the day or two prior. I thought to myself that I would keep today in mind for a local chase. It was looking rather blah as a cold front sinking south pushed up against a very weak warm front.
There were some weak storms that started to fire as early as 12 noon but they looked really poor. Then around 1PM a more dominant cell seemed to fire near Grand Valley and track east-southeast. I headed off to intercept it once I was convinced it was going to hold together for a few scans.
I was really not paying a ton of attention to the velocity data but boy I sure should have been! There was a nice couplet visible!!
The storm near Caledon East came into view once I was just south of Bolton. I was shocked to see a large, ground hugging wall cloud with slow but very visible rotation!
The wall cloud was almost textbook in nature, the only problem was rain from another storm impending on the western most side of it.
This is a better shot of the rain on the western flank from a secondary cell. You can also see the beginning of an outflow driven shelf cloud.
This was the sounding at the time which makes it very clear what the atmosphere was doing. The biggest problem was the nominal convective energy. The storm was working with very little CAPE, barely anything at 400 j/kg!
It was really nice to be able to just stay in one spot and watch the storm slowly creep over. These things are usually cranking in Southern Ontario and moving at 30 - 40 knots. This was a very plains like 10 - 15 knots.
There was plenty of low scud getting drawn in and lofted upwards but I never did see anything really tighten up and threaten to drop a funnel.
I wish the contrast was better! By this point rain from the neighbouring storm was starting to come down steadily and I knew it was a matter of time before this storm ran out of inflow.
This shot looking due west shows the neighbouring storm starting to really darken and now the outflow shelf / gust front is really visible.
The corn gave a really cool twisted effect.
This was my last photo before the wall cloud became buried in rain and the parent storm died. Not bad for only having to drive 10 minutes from home.
After re-positing south I snapped this quick photo of the gust front over Brampton before heading south into Toronto and calling it a day.
Here is a sequence from the King City radar showing the path of the velocity couplet from just south of Orangeville to Bolton.
Here are a couple GIF loops showing the storm and the associated velocity couplet. You’ll also find a time-lapse video at the bottom showing the supercell mesocyclone and associated wall cloud in motion with clear rotation.