ETV10, which covers news for Carbon, Emery, and Grand County, posted on their web site a Forest Service Press Release dated June 5th, prior to the fire breaking containment. The release notes that crews had a successful test burn on June 4th and on June 5th were igniting mixed conifer forest and hoping to burn 4,000 acres. Beetle kill had left dead trees in the area and the fire was intended to "stimulate aspen generation and reduce hazardous fuels."
In a report posted on KUTV.com yesterday, Brandon Jensen, a Forest Fire Prevention Officer stated that "we had a wind event come in, a storm come in and settled right over top of the fire." "Very rarely does this happen we lose very few of them." When asked why the Forest Service was doing prescribed burns in summer, he noted, "Up where we are burning, we are buning up high elevation, it's basically spring up high." He also added "If it's a very hot dry day no we do not burn, that's a big no no."
Data from the Salt Lake City International Airport, however, shows that the period beginning on the 4th of June was remarkably warm. Minimum temperatures from the 4th through the 9th were 62, 71, 62, 69, 62, and 68. This yields an average of 66, which is very close to the average not for June, but July (65). Maximum temperatures were 97, 92, 94, 94, 92, and 96. This yields an average of 93, which is consistent with the average for July (93).
A portable weather station positioned near the burn area at 9535 feet elevation shows minimum temperatures in the 50s and maximum temperatures in the 70s on the afternoons of the 3rd, 4th, 5th, and 6th.
We do not have long-term records for that location, but those numbers are probably consistent with averages for July for that altitude.
Bottom line: Temperatures appear to have been summer like.
Regular soundings are not available for the burn area, but soundings from the Salt Lake City International Airport also showed remarkably dry conditions. Soundings collected on the afternoon of the 4th, 5th, and 6th (local time) all show a very hot, dry, boundary layer with large dewpoint depressions and low relative humidities.
Bottom line: It was also dry.
Now, the real fly in the ointment for this burn was the convection that developed along the Wasatch Plateau in the vicinity of the fire on the afternoon of the 6th, when it is reported that the fire broke containment.
Given the soundings that day, one would expect conditions to be ripe for dry microbursts should those clouds generate precipitation aloft.
The wind data plotted above for the portable weather station shows a peak gust on the afternoon of the 6th of about 31 mph. Microburst winds can be quite localized, so it is possible that winds were stronger at other nearby locations.
Further investigation is needed to understand the circumstances leading to the "escape" of the prescribed burn. Hindsight is of course 20/20. However, all indicators suggest that we are in for a very long fire season in which vulnerability is high and rapid fire growth is likely. Sadly, another example of this happened in Moab last night, with several homes destroyed.
The comment below is from Chad Julian, Watershed Coordinator for the Little Thompson Watershed Coalition. It could not be embedded with figures through typical comment channels.
Hi Jim, thanks for providing your insight above. I am a fire-weather expert on the Colorado Front Range and your comment section wouldn't allow an answer this long to your blog post about the escaped Rx burn in Utah.
I am going to forward your blog link to a large collaborative group on the Colorado Front Range to help us with some discussion on this topic. I would agree with your perspective, I thought I would add some additional thoughts to compliment it.
The first thing that caught my eye, was the following statement: In a report posted on KUTV.com yesterday, Brandon Jensen, a Forest Fire Prevention Officer stated that "we had a wind event come in, a storm come in and settled right over top of the fire." "Very rarely does this happen we lose very few of them." When asked why the Forest Service was doing prescribed burns in summer, he noted, "Up where we are burning, we are burning up high elevation, it's basically spring up high."
What the Burn Boss did not consider here is that this is not a "normal" spring. If you look at melt-out for the closer snotel sites, it appears melt-out this year was much earlier than normal in that area. Quite a few of the snotel sites melted out in early-mid April in the surrounding area at similar elevations. That led to the surface fuels being exposed to sun and drying air earlier than normal. The winter also produced a pretty significant precipitation deficit. All of those things do affect the live-tree fuel moisture and the ability for crown-fire to occur. I'm not sure how they took all of this into account. The image below is from the Red Pine Ridge Snotel Site at almost 9000' for this year.
The final and most major point is that there is a predictable window that I would not apply Rx fire in UT, CO, NM and AZ. I have some unpublished data and analysis that shows a clear pattern in our most extreme conditions as to when our largest uncharacteristic fire occurs in those states. This data/analysis would also support planning and decisions to avoid burning in this window. Using the ONI for ENSO, the window occurs right after a La Nina Minimum, as the ONI trends towards neutral conditions. That window occurs between February and late June with June being the peak of the window. The 2011 Lower North Fork Rx burn was ignited during one of those windows, and this burn as well. When I was a fire and forest manager, I used this data/analysis to plan for Rx burns outside of this predictable window, so that your burning in neutral, or El Nino conditions. If your objective was to find a window to ignite an Rx burn to maximize your chance at escape, the window post-La Nina minimum in the spring would be it, with June giving you the best shot to meet that objective.
Lastly, the fire service and the National Weather Service just do not have the best relationship and it is difficult at best to get really good forecasting at a finer scale in these remote areas for these types of Rx projects. That is a major problem someone needs to take on, as the soundings for the day clearly show a high potential for micro-bursts. With better site-specific information that shouldn't have been a surprise to the burn team.
We as experts, researchers are not doing the best job we could be doing of working on the knowledge and technology transfer to these fire managers. Hopefully we can all learn from this and strive to do a better job of working together across disciplines and it could spark us to find a way to include climate and meteorology experts to our discussion of how we safely apply fire to our fire-driven landscapes.