Monday, June 26, 2017

Brian Head Fire Satellite Imagery

As of yesterday, the Brian Head in southern Utah was the 8th largest fire in the state since 2003.

The National Interagency Fire Center reports that the fire started approximately 12:13 PM on Saturday June 17th and that the cause is still under investigation.  Their situation report issued at 5:30 MDT this morning reports a size of 42,800 acres, with 1,140 personnel working on the fire, plus 11 helicopters.  Twenty six structures have been lost.

Images below are provided by the MODIS imager on NASA's TERRA satellite, which flies over the area in the early afternoon each day.  One can see a smoke plume, likely associated with the nascent fire, on 17 June.  Media reports suggest that increased wind from the southwest winds caused the fire to jump a line on the evening of the 20th, after which the fire grew rapidly.  An impressive smoke plume is evident on subsequent days.

15 June
17 June
18 June
20 June
22 June
24 June
If you click on the image for the 22nd of June, you can see the top of a distinct pyrocumulus cloud, a cumulus cloud produced by the release of both heat and moisture into the atmosphere by the fire.

Apparently some progress was made by firefighters yesterday, but today looks challenging, with above average temperatures and increasing southwesterly flow.  The NAM forecast for 0000 UTC (1800 MDT) this afternoon shows 700-mb (10,000 ft) temperatures above 16ºC, which is probably 3-5ºC above average, and moderate southwesterly flow in advance of a trough over central Nevada.

The expected outlook this morning states that "in the next 24 hrs could have active crown fire along northern flank with the return of the southerly winds. Potential spread distance 2-3 miles."

More info is at


  1. I was a little suprised that the vegetation was so dry already at that elevation, considering how much snow fell this season. The lower elevations are very dry, though, especially in southern Utah but in the north now also.

    1. I don't know where to access fuel moisture information, but I can comment on the snowpack and antecedent weather.

      Although the peak snowpack in the Brian Head region was above median, the snowpack melt this year was quite rapid. For example, here are traces from two SNOTELs just south of Brian Head:

      They show that the timing of the end of snowpack, at upper elevations, was about median. Willing to bet at lower elevations it was earlier than median.

      Data from the Cedar City municipal airport shows that the first 25 days of June ranked as the 7th warmest on record. Additionally, there has been no recorded precipitation so far this month.

      Soil moisture data is very tricky to interpret, but the nearby Circleville site (6120 feet) shows values at 2 to 8 inches depth that are actually quite low (< 10%). The Panguich site shows values near or below 15%.

      My take on this is that we're at best at climatological moisture conditions in the upper 15-20 cm of the soil.

      What all that means for fuel moisture I leave to those who know more about these things.


    2. Exciting, just what the forest needed!!!! Hopefully, it will knock the Dendroctonus populations down to a manageable level.

    3. The reason for the fire being so bad even with a good snow year is that the trees throughout the area were killed by bark beetles that moved through the area. It was just a matter of time before the place went up in flames due to lots of dead trees that weren't removed ahead of time.

  2. Spencer, that's not really the case based on our current understanding of wildfire. As a rule, fine fuels carry fire forward. In the initial red attack stage of beetle kill there's a lot of dry fine fuel, but what's left in the area of this fire is standing dead trunks. These large diameter fuels do little to promote fire spread.
    The impacts of beetle kill after needles and small branches have fallen are complex. The thinner canopies can allow higher wind speeds closer to the forest floor (this is called a boundary layer effect), and regrowth of vegetation adds a new fuel layer with different properties compared to a mature forest.