Qualitative Surface, Radar and Satellite Data

The following sections provide access to a large amount of radar, satellite, and surface observations for the time period of the Fort Collins flood.



The following image shows the results of an analysis of the motion of the Fort Collins thunderstorm of 28 July, 1997, based on Cheyenne, Wyoming WSR-88D observations ( Landel et al. 1998).  This analysis is overlaid on a digital terrain model.  The highest terrain is yellow, while the lowest terrain is magenta.  The boundary of Spring Creek watershed is outlined in black.

The jagged red line shows the track of the centroid of the storm over time (all times UTC), the location of the centroid at different times is denoted by red arrows.  The four colored ellipses show the approximate extent of the storm at four different times.  From this analysis, it is clear that the rising terrain of the front range of the Rocky Mountains played a very significant role in the motion (temporal evolution) of this storm.  Note: all times are UTC (MDT+6 hours).



Select a date/time from the table below to view WSI Intellicast qualitative national radar summaries (all times UTC).  Notice that there is almost continuous extreme rainfall in northeastern Colorado over this time frame.  The Fort Collins storm does not stand out in these images because of its' small scale.  (Images generated by WSI).

27 July 2200
28 July 0015
28 July 0100
28 July 0300
28 July 0415
28 July 0545
28 July 0600
28 July 0700
28 July 0830
28 July 0900
28 July 1000
28 July 1145
28 July 1200
28 July 1300
28 July 1400
28 July 1500
28 July 1600
28 July 1700
28 July 1800
28 July 1900
28 July 2000
28 July 2100
28 July 2200
28 July 2300
29 July 0000
29 July 0100
29 July 0200
29 July 0345
29 July 0400
29 July 0500
29 July 0600



Select one of the following three animations which cover different time periods.  These animations clearly illustrate the heavy widespread precipitation in northeastern Colorado during the same time-frame as the Fort Collins flood.  (all times UTC).   (Images generated by WSI).
27 July 2200 - 28 July 1145
28 July 2200 - 29 July 0900
29 July 0000 - 29 July 1100




Select the following links to view satellite imagery.  (These images are LARGE)
vi97072822.gif  (823k) GOES-8 Visible 28 July 2200 UTC
vi97072900.gif (503k) GOES-8 Visible 29 July 0000 UTC
ir97072901.gif  (734k) GOES-8 Infrared 29 July 0100 UTC
vi97073000.gif  (510k) GOES-8 Visible 30 July 0000 UTC
wv97073000.gif (167k) GOES-8 Water Vapor 30 July 0000 UTC


Click here to view the surface conditions at the time of the Fort Collins flood (0100 UTC 29 July 1997 or 7:00 p.m. MDT 28 July 1997).  Notice that the temperature/dew point spread in Denver is only 1 degree F, with a dew point of 63 degrees.  This indicates a near-saturated airmass at the surface- a very unusual condition for late July in Colorado.




An animation of Cheyenne, Wyoming, WSR-88D (CYS) Radar Reflectivities (1800-2215 MDT animation),  produced by CSU Atmospheric Science Dept. shows the persistence of rain over Fort Collins. The grid on the animation are the major streets in Fort Collins. The bold line shows the location of Spring Creek.