Was this mixing of higher wind speeds from just 100 m above the ground?
19.02.2026 02:57
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Was this mixing of higher wind speeds from just 100 m above the ground?
20 m/s effective shear supported elevated mesocyclones today. Interestingly, there were easterly wind gusts (56 km/h) with the storms that approached from the west.
Lots of time to search for the largest hail stone tomorrow morning!
Superimposed to a warm air advection regime at 850 hPa, a strong low-level jet transports subfreezing air into southern Ontario today.
The temperature zone in which the storms formed (around freezing at the level of free convection, close to -40°C at the equilibrium level) is almost the same. The European storms were surface-based (600 m - 5600 m above the ground level), the Canadian storms were elevated (2200 m - 6800 m).
Afternoon thunderstorms in north-west mid-level flow today across western Europe and Lake Huron, Ontario. Stretching possibly lead to increasing lapse rates in both situations; however, across Canada, the low-level air mass is too cold and stretching affects the air mass above the stable layer.
A narrow frontal snow band including some embedded vortices crossed the region west of London, ON. At 4 pm, London got a brief period of snow at the eastern edge. Guess is was more intense further west.
A mid-level trough axis crosses southern Ontario right now. Low-level stretching results in a well-mixed air mass and -30°C at 700 hPa. Some showers with gusts are possible even outside of snow squall paths.
The cold season progresses, but some brave Alberta storms formed despite strong vertical wind shear. CAPE in the right temperature zone and almost saturated air above the level of free convection helped.
Recipe for today's showers: Temperature -13°C / dewpoint -21°C, -36°C @ 700 hPa + one mid-level trough axis. Pretty chilly in London, ON.
In some parts of the city 45 cm snow cover. The main difference to the December squalls is the temperature. -10°C at noon. Wonderful!
The mid-level front is also impressive, with a tropopause fold (2 PVU) at 750 hPa just upstream of the vortex. Nice response at low levels.