Synoptic-scale Water Vapor Imagery

This water vapor image was taken from GOES-9 at 1200 UTC on 31 May 1996. The water vapor channel on the GOES Imager is centered at 6.7 um, which responds to water vapor at middle and upper layers of the atmosphere. Although the pressure level of maximum response varies somewhat with the atmospheric profile, it is typically near 400 mb. Therefore, this channel is useful for analyzing general flow patterns, including upper-level lows and highs, jet streams, shortwaves and areas of upper-level subsidence.
This image is an excellent example of how an upper-level shortwave trough appears in the water vapor channel. Note the comma-shaped feature over the four corners region. The white and purple pixels (see the loop) in western CO are associated with the clouds caused by the upward vertical motion on the northeast side of the shortwave.
Upward vertical motion is a cooling process which can create a steeper lapse rate, which is favorable for thunderstorm formation. The lifting ahead of the shortwave also appears to have aided in the initiation of thunderstorms (one of which was tornadic) in eastern CO later in the day.