INTERPRETATION
NOAA
NESDIS
Regional
and Mesoscale
Meteorology
Team
Cooperative Institute for Research in the
Atmosphere (CIRA)
Colorado State University
Fort Collins, Colorado
April 5, 1999
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Figure 1 0645 UTC 10.7 µm image from GOES-8 Click on image to enlarge |
Figure 2 0645 UTC fog product image Click on image to enlarge |
Around midnight MST, 1 April 1999, a cold front moved southeast along the front range of the Rockies and over central Nebraska. The temperature gradient and wind shift associated with the cold front are evident from the surface data overlaid on the 0645 UTC 10.7 µm image from GOES-8 (Fig. 1). Not evident, however, are any low level clouds that may have accompanied the front. The fog product is often helpful in locating such clouds.
As the name implies, the fog product was designed for
the purpose of nighttime fog detection. However, any liquid water
cloud (with no clouds above) may be detected using the fog product.
A cold frontal stratus deck associated with this front, for example, is
likely to be seen in the fog product. Figure 2 shows the 0645 UTC
fog product image. A liquid water cloud or fog deck is evident over
northwestern Nebraska in this image, along with other liquid water clouds/fog
over most of the eastern edge of the image.
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The contrast in the two products' abilities to monitor the movement of the cold frontal cloudiness is also seen in the loops provided. Because the cloud top temperatures of the fog/clouds behind the front were similar to the ground temperature, the clouds are not distinguished from the land at 10.7 µm (Loop 1). On the other hand, the fog product allows one to track to the movement of the frontal fog/clouds (Loop 2).
Although the fog product is useful for tracking low-level liquid water clouds and fog, it is not possible to distinguish between the two. Ancillary data such as surface reports are needed.
For more information on the fog product, visit the 3.9 µm tutorial (http://www.cira.colostate.edu/ramm/goes39/cover.htm ) off of RAMM/CIRA's home page.