Using the Average Image Product
Average imaging can be used to identify persistent features such as convective cloudiness which
occurs in the same place day after day due to terrain forcing. These two figures show the results
of averaging visible images over a 15 day period, for two different times of day, during the first two weeks
of June 1996. The average is centered over Colorado where terrain plays a key role in cloud formation.
The extremely white features in central and western Colorado are snow-lined peaks along the
Continental Divide. The light areas in the western half of the state are caused by clouds which
typically form early each day over the high terrain of the Rocky Mountains. The first image is from
1900 UTC, the second from 2200 UTC. Note how the cloudiness moves out over the Plains of
eastern Colorado by later in the day.
Click on any of the following images to view in their original 640 x 480 resolution
Average imaging can also be used to track short term events, such as heavy rain storms where
the rain is persistent over an area for some time. Here, an easterly wave, interacting with an
upper level trough, brought heavy rain and flooding to the southern Windward Islands on
October 26, 1996. As much as 250 mm (10 inches) of rain fell on the island of St. Lucia
in the 6 hour period from 1200 to 1800 UTC. This image is an average of all the GOES-8,
10.7 Ám images received over the 12-hr period from 9:15 UTC to 21:15 UTC on 26 October.
The color table shows the coldest cloud tops are between -63C and -65 C. The arrow
points to St. Lucia where the heaviest rains fell.
|15-Day VIS Image Average from 1900 UTC||15-Day VIS Image Average from 2200 UTC
12-Hour 10.7 Ám Image Average
This concludes the presentation of the material in this learning module.
We appreciate your interest and hope you benefitted from it.