Photos courtesy of Bob Olinger
This cloud feature looks a lot like
a large tornado bearing down on Newark. How can we tell that it's not?
There are a few subtle hints. Keep in mind that all funnel clouds and
tornadoes rotate. In fact, most rotate and change shape very
quickly (think of all the tornado videos you've seen). In these photos,
notice that the edge of the cloud feature looks nearly the same in each photo.
This suggests that this cloud is hardly changing shape at all which makes it
unlikely to be a tornado or funnel cloud. Also, notice the little cloud
out ahead of the main cloud line (indicated in pink). Usually, cloud
debris such as this (referred to as scud) will rotate counterclockwise around a
tornado or funnel cloud. In this case, this scud cloud is moving upward,
and slowly at that.
Low hanging clouds like this one are often reported as funnel clouds or tornadoes. These mistakes can be easy to make, but keeping a close eye and looking for signs of rotation will help a spotter distinguish a tornadic feature from a simple ominous lowering. Of course, the National Weather Service encourages reports anytime a spotter sees something that he or she thinks may be tornadic, even if confidence is low!
So what are we seeing in this photo? It's difficult to tell from these photos alone. However cloud lowerings often indicate the base of an updraft or other upward motion. In this case, this cloud feature may have been a weak shelf cloud or non-rotating wall cloud.