Dozens of reports came in Wednesday regarding funnel clouds across California. The one above was captured by Doug Debruhl in Santa Maria, California. This is a classic case of a cold air funnel cloud, also known as a cold core funnel.
First, a funnel cloud is a vortex of air suspended in the air until it touches down on the ground. If it touches down on the ground then it’s classified as a tornado. In this case in Santa Maria, the funnel cloud did not become a tornado. But it was considered something different; a cold air funnel. Cold air funnel clouds are unique, but not totally rare. They occur in colder scenarios (hence the name) usually behind cold fronts, where the air mass is still unsettled (a.k.a. unstable) but is much weaker than an environment that would produce a normal funnel cloud/tornado.
In this case in California Wednesday, a surface cold front recently passed and temperatures were around 50 degrees. Colder air aloft (between 5,000 and 20,000 feet) was moving in from the west and northwest. This helped to create a more unstable environment where a growing cumulonimbus cloud was able to produce a funnel cloud.
Most cold air funnel clouds do not touch down as tornadoes, but some do. If it happens the tornado is usually weaker as an EF0 or EF1, but can still produce wind damage. Between 1991 and 2010, California has averaged 11 tornadoes per year. The state averages 0 “strong to violent” tornadoes, classified as EF3-EF5’s each year. California’s tornadoes usually hit in winter or spring, and usually in the north central valley.
For WeatherNation, Meteorologist Steve Glazier