Woodlands, MB July 14, 2017 Lake-Breeze Storm

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July 14th was one of those classic southern Manitoba chase days where frontal interactions with Lake Manitoba just worked out perfectly to create a nice high-based supercell.

21Z (4:00 pm CDT) surface analysis

A warm front was extending into south-central Manitoba with a cold front swinging through the western part of the province and a low pressure system occluding over Lake Manitoba. The occluded front was going to be the primary forcing mechanism to trigger thunderstorms with the help of a lake-breeze boundary off Lake Manitoba.

21Z NAMNEST sounding for Winnipeg, MB

Soundings from the 3km NAM had a pretty strong cap and generally unimpressive wind profile. Basically, at 4:00 pm, no storms were expected to form. However, around 7:00 pm, the front began crossing Lake Manitoba and the sounding changed dramatically:

00Z NAMNEST sounding for Winnipeg, MB

Above you can see the cap has been removed completely, decent lapse rates, moderate CAPE, decent shear and an interesting hodograph. My target was Woodlands, to the northwest of Winnipeg. This is where I believed storms would initiate, primary high-based in nature and then move east-southeast and become surface-based.

This is exactly what happened as a very high-based storm began forming between the 7-8 pm time frame. Important to note that a lake-breeze boundary had developed off the southeastern side of Lake Manitoba and extended toward the west. I was counting on this boundary to enhance low-level shear in the lower levels for preexisting storms, while a few other chasers were betting on the south side of it for storm initiation. The timelapse video below gives a good picture of the storms forming:

The storm continued to be very high-based just west of the Woodlands radar:

But as it moved east-southeast toward Woodland, the storm became surface-based:

At this stage, there was a shelf cloud developing, but it did not last very long. In a matter of perhaps 10-20 minutes the storm fell apart. However, I was able to capture some amazing sights of it:

Truly amazing low-precipitation supercell. As it began moving quickly east, the storm recycled and developed a hook-echo:

At this stage, the storm developed a wall cloud. When I got in cellphone range, I called Environment Canada to report a rotating wall cloud. The storm had already been tornado-warned, but since I did not have data at the time, I didn’t even know it was!!

Near the end of the video above, you can see the rotating wall cloud sped up so to be able to notice the rotation a bit better. All in all, very happy with my forecast and pinpointed perfectly the storm that would have produced a tornado on this day. No other storms developed in Manitoba that day, so I know a few people busted, but it was a tricky forecast for sure. Happy with the shelf cloud I got!



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