Earth- and Storm-relative Imagery Loops

Satellite imagery sequences are usually presented in an earth-relative reference frame, wherein atmospheric features move with respect to the earth's surface. However, satellite imagery animated in a storm-relative sense can offer additional insight into the nature of a moving feature (the term "storm-relative" includes any moving feature, not just storms). In a storm-relative loop, a constant motion vector is calculated from the individual earth-relative images. This vector is used, along with the image times, to reregister the images such that the feature which was moving relative to the earth remains stationary.
Earth-relative Imagery

The first loop is a series of earth-relative images of the severe and tornadic thunderstorms over western KS from 2230 to 2325 UTC, on 31 May 1996. Apart from the line of thunderstorms itself, other features which may be important to storm evolution are visible. Some of these are the southerly low-level flow to the south of the line of thunderstorms (as seen by the motion of the cumulus clouds) and cloud top features such as overshooting tops and cirrus wakes.

The loop animated in the storm-relative sense is centered on a storm which produced a tornado near Ness City, KS around 2300 UTC. Storm-relative loops may make additional features stand out that are not immediately seen in earth-relative animation. Some examples seen here include an apparent circulation near the overshooting top, a low-level outflow boundary exiting the storm to the southwest, a region of rapidly developing towers beneath the anvil on the southeast flank of the storm and cirrus dissipation southwest of the growing anvil. Additionally, it can be seen from the motion of the cumulus clouds to the south of the thunderstorm line, that the low-level flow relative to the storm is southeasterly. So, although the low-level winds (as seen in the earth-relative loop) are from the south, when the motion of the storm is accounted for, it can be seen that the airmass feeding the storm is located to its southeast.