Winds gusting out of the north at over 40 mph spread across the southeast Colorado plains during the morning and early afternoon of 26 April 2017. Given the strong winds, dust was picked up from two separate areas as detected by the GOES-16 10.3 – 12.3 split window difference (Figure 1). Lofted dust detection using GOES-16 has been described in previous blog posts. Using the GOES-16 imagery and burn scar maps, it was quickly determined that the blowing dust was emanating from two very recent burn scars: the 117 fire in southern El Paso County and the Badger Hole fire in eastern Baca County. In this example, the dust signal in the imagery was subtle, but the moving pixels of relatively darker gray, combined with the location relative to the burn scars and confirmation via a webcam, gave us confidence that we were seeing blowing dust. The linear gray color scale was adjusted to make the dust areas more obvious. The dust was not easily apparent in visible imagery or radar imagery (KPUX radar was not available).
Given what was observed in GOES-16 imagery and confirmed in webcams, areas of blowing dust was added to the forecast grids (Figure 2) through the morning into the early afternoon, when wind speeds would begin to subside. The GOES-16 imagery was used to outline the narrow regions where blowing dust was occurring and would likely continue to occur. The AFD was also updated to read: “GOES-16 split-window difference imagery and webcams indicate blowing dust emanating off of the recent 117 Fire burn scar in southern El Paso County and Badger Hole Fire burn scar in eastern Baca county. Winds out of the north are gusting over 40 mph in these areas, carrying dust well south, reducing visibility and air quality in areas. Have added blowing dust to the grids through the early afternoon, after which wind speeds will begin to decrease.”
If someone in eastern Baca County were to check their forecast during this period, it would look like that in Figure 3.
Bill Line, NWS