METEOROLOGIST JEFF HABY
The terms tornado and funnel are two terms that have similarities and differences. Sometimes the two terms are used improperly or the context
is uncertain. This may have to do with the similarities that they have. Both a tornado and a funnel extend below a cloud. Typically a
thunderstorm needs to be present or a significant cloud development. They can both extend below a cumulonimbus cloud. They are both a
relatively strong spinning of the air.
The main difference between a tornado and a funnel is that a tornado must be in contact with the ground. To be in contact with the ground
means that the circulation is having a significant interaction with the ground. Typical signs of this interaction at the ground include
debris from the ground being brought aloft, a dust circulation on the ground, and the condensation cloud with debris visually being seen
as extending from the cloud to ground level. Thus, the funnel becomes a tornado at the moment it interacts with the ground. Another
difference is that a funnel can also be seen below relatively smaller clouds and non-thunderstorm clouds, such as the case with
cold air funnels and funnels extending below cumulus clouds. Tornadoes on the other hand are typically, but not always (i.e. some
land spouts), associated with a strong thunderstorm cloud (i.e. cumulonimbus) or a grouping of strong thunderstorm
clouds (i.e. squall line).
Some related terms that can be heard that combine these two words include “tornado funnel”, “funnel cloud”, “tornadic circulation”, and
“condensation funnel”. When these terms are used it helps when a description is added since the context can be confusing. Basically
though, it is either a tornado or it is funnel. The funnel can become a tornado and a tornado can revert back to being a funnel.
Sometimes the tornadic interaction with the ground will not be visible. In these cases it is a tornado since it is interacting
with the ground, but from a distance it may be unclear. A sign that the circulation is interacting with the ground is any sort of
dust and debris that is seen being blown aloft from the ground.
It can be more difficult to detect a ground interaction when there is a condensation funnel that does not extend to the ground. This is
sometimes the case with weak tornadoes. Significant tornadoes tend to have significant dust and debris circulating around the tornado
and a large condensation funnel and thus it is obvious the circulation is on the ground.
The main point is that a tornado is interacting with the ground (such as a circulation that will be rated F0 or higher) while the funnel
is aloft and not significantly interacting with the ground yet as shown with a weak attempt at showing my artistic talents below :) .