Posts Tagged: squall line
April 18th 2013
On July 19, 2016
- 2013 Storm Chases
Surface analysis 18Z Thu Apr 18 2013
Hard to believe that less than a week after the ice storm I was out chasing a large ragged bowing squall line with temperatures around 25 Celsius. April is really a month of extremes!
Storm motion with this bowing segment was 59 degrees (Northeast) at 57 knots (105 km/h)
You'll see how the storm progressively bows as it progresses north along the line
Here's a quick screen grab from my tablet showing the radar at the end of my storm chase day. You'll notice the a large bowing segment heading off towards Uxbridge, that there is the storm which bowed out right over my head in Bolton/Caledon.
July 8th 2016
On July 10, 2016
- 2016 Storm Chases
The first really active chase day of the year for Southern Ontario that was not a bust with widespread convection and severe weather ranging to hail to wind and even some local flooding. The entire day basically focus around an incoming low pressure system from Michigan with a trailing cold front that was crashing into very hot and humid air as a 500mb shortwave scooted past to the north.
After a quiet May and June, the storms were welcomed and helped to ease the drought conditions imparted across much of Southern Ontario thanks to a very dry and storm free spring and early summer.
Surface analysis 21Z Fri Jul 8 2016
I started the chase day in Woodstock Ontario around 2PM as I focused on two possible targets eventually narrowing it down to the area around Goderich. As with every storm chase, looking at the surface observations and being in position early rather than late is always important and critical! Playing catchup or being unaware of the atmospheres potential is never a good thing and can really make or break a chase day.
This was one of those days, plenty of potential with clearing skies and otherwise good timing for the storms. A cold front was swooping in from Michigan while a warm front lifted through Southern Ontario bringing in hot humid air!
TD's jumped significantly just behind the warm front and boundary layer moisture was aided by rainfall overnight from a weak MCS that pushed through.
I stopped in Woodstock and eventually Mark Robinson (a fellow chaser) met up with me. We then headed off to intercept a storm that was slowly coming across the lake. This was the view over an hour before the storm was due to arrive.
Long before the storm arrived this shelf feature was visible on the southern periphery of the storm.
What was interesting with this storm was that it was sitting in the center of a meso low, perhaps thermally induced? Whatever the case, it was in an area of enhanced vorticity and there were winds curving into the storm from the Southeast. This was very interesting to observe, especially since the night prior the WRF-NAM basically forecasted this and was spot on!
The favourable low level winds were also effectively pushing the supercell composite index up ahead of the storm. At one point there was a strong TVS signature visible over the waters of Saginaw Bay. So there was definitely verifiable rotation occurring and all the dynamics were drifting east with the storm.
Mark with his periscope feed running!
The shelf from the storm was slowly getting closer and strong knuckle convection could be seen above the shelf feeding from left to right (south to north) into the storms dominant cell.
The storm at this time was now about 50 kilometers away and beginning to pickup forward velocity.
The latest radar scan had the storm taking on a bowing appearance with a persistent pocket of rotation in the NW quadrant where you would normally find a bookend vortex signature.
These little fingers of moisture were getting lifted all along the edge of the forward flank downdaraft.
As the storm continued to close in the structure now becoming visible was just awesome!
At this point in time the rotation in the northern portion of the storm seemed to simmer down somewhat. I'm not sure if that's due to the storms distance from the radar increasing or if the rotation was actually falling off, but whatever the case, the storm still had a very impressive radar signature.
Believe it or not, this is a single 11mm image. I cropped out the shoreline (didn't like the look of the grass). The storm was much closer than it looks in this image!
At this time the storm is about 10 kilometers away!
This is one of those moments where breaking out the 70-200mm lens was a good idea! It's hard to explain, but sometimes you just need to zoom in and focus on the key points of structure that are just amazing.
The structure on this storm was more reminiscent of a high plains supercell or a moisture packed HP storm roaring through Nebraska, but this was Canada over Lake Huron.
Despite this storm having a more linear and bowing appearance on radar, the curvature literally bent around into the primary updraft giving it that power high precipitation supercell look. The shear values were right, so this storm was definitely a super cellular hybrid of sorts.
Here's a panorama stitched together from three separate images. What a beast of a storm, just beautiful!
Around this time, the couplet was back on radar and the storm was looking even more powerful with higher dBz values showing up in the strongest portions of the storms core.
What not a true mothership in the classic sense (that's reserved for LP supercell storms) this stacked shelf really had a nice curl looked to it that had that mothership type look. If you look near the edge of the leading shelf, thanks to light refraction, you can see a thin dark line marking the edge of the marine layer. You'll not the storm bends it upwards and eats it!
I zoomed right in to show just how green the area inside one of the folds along the stacked shelf cloud was becoming. There was definitely some hail growing but the 30C air at the surface with the very high humidity was ensuring that most, if not all of it, would melt before reaching the ground.
The storm was probably only 3 kilometres away at this point. The air was still calm if not blowing slightly towards the storm at the lookout location I was perched upon.
This was the last image I took before packing up and heading out. Again, this is super wide at 11mm, but rest assured, the storm was virtually on my head and I had very little time to spare.
There were many lightning bolts crashing all around me which was the other reason for the rapid retreat. Lightning is the biggest danger, you can't predict it and don't see it coming until it's too late and I don't mess around, it's a killer.
I'm not sure how far away this strike was but it must have been no more than a few hundred meters at most. There was no delay between the sound and flash. A few other chasers were just getting in their car when this struck.
While less dramatic than the first frame of video, this gives a better idea of what was getting struck, and I'm still not sure? Was it a tree? Rock? Dock? Whatever got zapped sure felt it though!
Mark, John and myself bolted east to try and get ahead of the storm. This part of the province is pretty wide open and flat with only the occasional row of trees to obscure the view!
Dashcam Video from Exeter with strong winds blasting in.
May 11th 2015
On June 1, 2015
- 2015 Storm Chases
On this day a messy warm front which was severely stunted by the cold water of the great lakes struggled to make it into Southern Ontario. Shear profiles supported a linear squall line at best along a trof line and energy was very weak with peak cape around 800 j/kg.
So there was plenty over hyped optimism about today's potential storms. Heck, even the SPC had a 5% chance of a tornado!
Despite all the optimism, I was more pessimistic. I had been in downtown Toronto most of the day and it was dreary! I was watching my home weather station and it was a sunny 28C, meanwhile 22km to the south it was 12C and cloudy. The problem was lake moderation from the frigid waters of Lake Erie and Ontario.
This map from Wunderground shows exactly what was going on. You can see the single digit temperature air near the Lake Ontario shoreline, the location of the now stationary warm front and the super warm air to the west.
I was really concerned that nothing of any substance would make it east of Hamilton, but everything west of Woodstock looked like it was washed out by rain. I gambled that the trof pushing east would do something in the small pocket of warm air south of Cambridge and a squall line began to form.
Because moisture was abundant and there was lots of potential for scud and stuff due to pockets of lake moderate air mixing in here and there I thought that maybe a shelf would be possible. Unfortunately this part of the Niagara Escarpment is a terrible area to find clearing! The blossoms on the trees however did look beautiful!
I found one area with a little bit of clearing but was not satisfied it would be good enough.
I eventually found a hill in St. George and parched myself atop it. Then slowly a shelf formed as the squall line drew closer. BINGO! Success!
The shelf began to really begin looking pretty. There were these neat striations all throughout the clouds upper deck.
On radar the growing squall line was quickly intensifying.
By now the shelf cloud was really coming together and looking cool!
While not severe, it sure had a cool mean look to it!
I'm trying to get the St. George watertower in with the squall line.
By now the squall line was almost above my head and closing in quickly. My very brief chase would be coming to an end soon!
Not sure what to make of those turbulent waves near the top right? Cool though.
This was how things were progressing on radar with the strongest part of the line now bearing down on me.
I decided to break out my Fish-eye lens and grab some cool 180 degree images.
This was my last photo. The winds were now picking up and drops of rain were falling but you'd never know with just how wide the fish-eye lens is. Fun little chase for early May in Southern Ontario.
