Relatório do Acidente ocorrido no Incêndio Florestal de Yarnel Hill

What were they not focused on? Using available information coupled with understanding of
wildland fire culture, we reached the following conclusion:
• In retrospect, the importance of the 1526 weather update is clear. However, the update
appears to have carried less relevance in the crew’s decision-making process, perhaps
due to the wind shift (starting at about 1550) that preceded the outflow boundary, or
perhaps because of the time it took the outflow boundary to reach the south end of the
fire (at 1630). It is possible that they may have interpreted the early wind shift as the
anticipated wind event.
The outflow boundary update that the NWS communicated to FBAN at 1526 seems to have
been relayed efficiently throughout the incident organization. FBAN radioed the update to
Operations, and Operations checked in with the crews to make sure they received the update.
The Granite Mountain IHC affirmed and passed along the information to their lookout. We
considered why this weather update might have carried less relevance with the Granite
Mountain IHC, leading to discussions of desensitization, false alarms, and aging of information.
People in the desert southwest may become desensitized to high temperatures and low relative
humidity during certain times of year. As two SMEs figured, crews in the area likely received
messages over the preceding two months similarly predicting conditions such as hot weather,
dry fuels, and thunderstorms. In other parts of the country, these kinds of predictions are rare;
when they do occur, they constitute “strong signals.” Like car alarms in an urban neighborhood,
repetition of strong signals resets the cognitive baseline for what is “normal.” People
desensitized after repeated warnings start to rely on other cues to identify new and relevant
conditions.
There is also danger that a firefighter may become desensitized to extreme fire behavior, based
on an old mental model that extreme fire behavior is rare. One SME said, “The unusual is now
usual – the scale of fires today is extreme. That’s what’s normal now.” Another said, “This fire
went from wildland to WUI (Wildland-Urban Interface) within a burn period. This is part of the
new reality. The new normal is extreme fire behavior.”
Consider the role of false alarms. If weather conditions described in one update do not occur, or
occur at a diminished level as happened in this case, what will be the level of confidence in the
next weather update? Does that decrease the confidence in future weather updates originating
from the same source? Although we will never know the answer to this question, it is worth
asking: In the absence of observed cloud and column conditions, to what extent did the Granite
Mountain IHC think the weather in the second update was not going to materialize because
weather in the first update occurred on a diminished level?
Regarding aging of information, people process information based on a variety of factors
including perceived timeliness, reliability, and observations. Weather personnel often issue
forecasts covering a set timeframe. If the forecaster considers the update reliable for a finite
period, the recipient may draw conclusions about its window of relevance. The older a weather
Yarnell Hill Fire Serious Accident Investigation 48