Relatório do Acidente ocorrido no Incêndio Florestal de Yarnel Hill

area at 1604. The red
shape shows the fire
plume. After this
movement, the original
line of storms slowly
began to weaken.
Lightning trends
associated with this
decaying line of storms
showed no change in
location. Skies remained
dark towards the north
and northeast and field
personnel would have had
a harder time gauging
storm movement and the
potential threat to the
Yarnell area.
Figure 10. FAA radar detects an outflow boundary very near the
northern end of the fire area at 1618 MST.
As the outflow boundary approached the fire area, the wind field gradually shifted to the westnorthwest,
pushing the fire towards the east-southeast. At 1618, the FAA radar showed the
outflow boundary nearing the northern most end of the fire area (Figure 10). The boundary had
traveled 16 mph, covering 13.5 miles in 50 minutes. The mid and upper-level winds influencing
the smoke plume had also begun to shift. The red shape in Figure 10 shows the smoke plume.
Two fingers of concentrated smoke had begun to develop by this time.
Around 1620 MST, field personnel near Highway 89 in the Yarnell area began to hear thunder,
and shortly afterward noted
spritzes of rain or mist mixed
with ash. The Earth Networks
Total Lightning Network verified
the thunder, showing two incloud
lightning flashes at 1620
(Figure 11).
Meteorologists use Doppler
radar to detect thunderstorm
height, generating imagery
called echo-top data. The
imagery, which the general
aviation community uses for
monitoring trends in
thunderstorm intensity, can
Figure 11. Earth Network's in-cloud lightning detection on a
Google Earth map at 1620 MST.
Yarnell Hill Fire Serious Accident Investigation 72