SCOTS VALLEY, Calif. –

A rare tornado touched down in Scott’s Valley Saturday afternoon. It came after a night of strong winds and heavy rain, as well as a passing cold front.

By early Saturday morning, wind speeds of over 80 miles per hour had reached parts of the Santa Cruz Mountains. In Monterey, wind gusts even reached speeds of 78 miles per hour, proving that it was a very strong wind event.

This content is imported from Twitter. You may be able to find the same content in another format, or you may be able to find more information, at their web site.

For a tornado to form, there must be not only strong winds at the surface, but also strong winds aloft moving in a different direction. This is called wind shear.

In order for wind shear to affect a storm and produce a tornado, the position of the updraft must shift vertically rather than horizontally. The difference between the wind direction on the surface and in the air must be about 90 degrees.

This was the case this afternoon with a supercell (or strong thunderstorm) that moved across the Pacific Ocean and into the Santa Cruz mountains around 1:15 p.m.
Looking at surface and high-altitude air data at the time of the tornado at 1:40 p.m., winds were blowing primarily from the south at about 30 miles per hour. At the same time, rain and clouds quickly moved in from the west.

This resulted in 90 degrees of wind shear, allowing the supercell’s updraft to shift vertically and trigger a tornado.

Although rare, tornadoes do form on the Central Coast. However, they typically develop in valleys or as waterspouts off the coast.

In today’s case, it was likely the steep terrain of the Santa Cruz Mountains that increased the strength and speed of the tornado formation.