An area of thunderstorms over southern Montana was examined using OCTANE and other satellite imagery.

Of interest in particular is the storm over western Big Horn County. The day cloud phase loop (bottom right) shows that this is a slow-moving thunderstorm, but there is also a bunch of patchy/streaky high cirrus moving much faster over top of it. Looking at the OCTANE speed sandwich (top left), it appears that the convective updraft was assigned the speed of the faster cirrus (yellow/orange, ~80kts). In reality, this updraft is moving much slower. For the sake of comparison and verification, notice the two updrafts over Stillwater County. These updrafts appear similar in nature based on the day cloud phase imagery, but the Stillwater County storms do not have any high cirrus contaminating the signal. As such, they are assigned a proper velocity on the OCTANE speed sandwich (green, ~30kts). There are also some artifacts in the divergence (bottom left) with the Big Horn County storm.

–Insolation