MUST SEE: Extremely rare tornado sighting in B.C.
Tuesday, September 18, 2018, 4:25 PM - According to Environment Canada, B.C. possibly had its fifth tornado over the past fifteen years, and even more shocking, its location was in the Lower Mainland.
Normally, the Pacific Ocean acts like a layer of stability; its cooler sea surface temperatures mitigate extreme amounts of instability from building in. Another factor, British Columbia's mountainous terrain. The higher up you go in elevation, the less moisture is available to build the necessary ingredients to permit the formation of a tornado. The larger the spread between temperature and the dew point, the less likely a tornado can develop.
In this case, the tornado may have been enhanced by some local convergence of winds, with the help of the topography from the North Shore mountains.
The environmental conditions and atmospheric soundings on Sunday showed surface based instability available for thunderstorms and decent amount of low level moisture. The trough aloft was very unstable and cool, and some local pockets of rising air with the trough (vorticity) likely contributed to the intensity of some of the thunderstorms in the area.