So pretty much anywhere from 50 degrees north or south of the equator," Wysocki told Insider. "If you can get yourself a strong thunderstorm or line of thunderstorms will develop. In fact, shelf clouds are quite common and can develop just about anywhere there's a thunderstorm brewing, said Mark Wysocki, a senior lecturer at Cornell's Earth and Atmospheric Sciences Department and New York State climatologist. Video shows the cloud moving through the city, bringing strong winds up to 60 mph with it.Īt first glance, the shelf cloud that passed through the skies of Chicago on Wednesday morning looked like something out of "Independence Day." But don't worry - this ominous-looking formation isn't signaling the end of the world. The cloud is a sign of severe thunderstorms and you should take shelter if one is coming your way. It does not occur commonly, but with bow echoes it is possible for tornadoes to occur under shelf clouds.An imposing, ominous shelf cloud was spotted in the skies above Chicago. This event was not a gustnado, but a true tornado, with rotation detectable on radar. Between my disbelief, the congested location I was in, and the quickness of the event, I got no photos or video. Wrong! A tornado touched down briefly in that location, and radar documented rotation in the storm. I thought, no, it looks like a funnel but in that location it has to be a scud finger. I was in a congested area a short distance from my home when I saw what looked like a funnel cloud under the shelf cloud to my SE shortly after it passed over me. It had been a bow echo for at least a half hour before the experience I am about to describe. I was actually on the way home from a chase as I had been ovetaken by a cluster of supercells that had quickly morphed into a bow echo. I saw an example of this last July 5 in southwest Illinois. In many of these cases, it is likely that the tornado would form under the shelf cloud on the leading edge of the bow echo. Scroll about halfway down and follow the links to the case studies. Examples of research documenting this can be found at: Most often the tornadoes occur from the apex of the bow echo northward. Often this occurs when the bow echo interacts with some boundary, such as an outflow boundary from earlier convection. It has been well-documented by the BAMEX study and others that tornadoes do occur along the leading edge of bow echoes. I too, am too chicken to answer that question. So could a true tornado (not a gustnado or rising smoke) occur under a shelf. This obviously is another example that is NOT a tornado. This causes the air within this boundary (gust front) to rise to the nose of the shelf. Or perhaps you'll get a 'smokenado' like the one I took in the picture below where the smoke is caught at the intersection of the outflow speeding out from the left and meeting the rising inflow from the right which is heading into the shelf aloft. What you often get are gustnadoes or spinups simply caused by the strong outflow - NOT rooted into any cloud base. So for the vast majority of the time, a tornado here is quite unlikely. Therefore, with this cold and strong outflow (which as a rule does not get caught back into the updraft by going up through the underbelly of the shelf cloud), nothing of any significant buoyancy is able to get rooted below the shelf to create. This undercuts anything that is trying to get surface based. The problem with tornadoes in these situations is that you generally have the strong outflow at the surface. That's because the inflow is coming in through the shelf cloud and the updraft is on the front side of the storm. There may be a great shelf out front, and the reflectivity has the deepest reds on the "eastern" side of an eastbound squall line. This air rides up above the surface outflow and enters the storm and rises once it gets to the tower. Sure you have the outflow below at surface level, but what makes a shelf cloud a shelf cloud is the fact that there is this inflow aloft, just above the surface which gives it the shelfy appearance. Something that a lot of people don't really comprehend is that a shelf cloud itself is an updraft area. Well I tend to be a bit rash in my comments, so I'll bite and get the heat for it. 151 views of this post and nobody wanted to bite. Well this post was overlooked, and I'm sure on purpose! Nobody wants to say that they believe a tornado can come out of a shelf cloud.
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