Tornadoes - Severe Convective Storms and Tornadoes: Observations and Dynamics - page 312

Figure 6.7. Tornado damage track (horizontal brown swath surrounded by greenery from
vegetation) over Massachusetts from a tornado on June 1, 2011, as seen by the Landsat 5
satellite.
cycloidal damage marks indicative of smaller scale vortices rotating around a
common axis ( Figure 6.11 ). They typically do revolve all the way around the
common axis, but rather appear in one location with respect to the larger vortex,
rotate part way around, and dissipate. They often lean outwards with height from
the central axis of rotation ( Figure 6.10a ).
When a rotating column of air is visualized as a condensation funnel that does
not appear to be making contact with the ground (i.e., it visibly terminates well
above the ground and no surface debris cloud is apparent), then the feature is
referred to as a ''funnel cloud'' ( Figure 6.12 ). It is not always clear whether or not
a funnel cloud is associated with a strong circulation at the ground, especially if
the ground surface does not contain material that is easily swept airborne.