WILDFIRE: LATEST LEARNINGS- v01.6

WILDFIRE: LATEST LEARNINGS

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General learning outcome:

SPECIFIC HIGH COUNTRY WEATHER:

Specific learning outcome:

When prevailing winds exceed 25km/hr lee-eddy winds may become important.

Topic:

The conditions for dominance of lee-slope eddies.

Operational Awareness for Advanced Firefighters & Fire Behaviour Analysts


During operations on the lee-side of landforms, operations staff must monitor the wind field. This is because sudden changes in winds may occur.
The critical factor is whether the prevailing wind speed exceeds 25 km/hr. This may happen because of the diurnal cycle of wind speed, especially when the overnight inversion boils off. It may also happen due to synoptic freshening, or under the influence of approaching weather systems. Extra care is required if a wind change is part of such a system. It is feasible that on a windward site, for example, a reversal of the prevailing wind direction accompanied by a freshening of the wind speed could result in an additional switch to a lee-eddy field and no overall change in wind direction on the ground, but major changes in plume behaviour and spotting footprint.
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This website is dedicated to bringing forward the latest research findings. They are provided to allow firefighters to be made aware of critical safety issues ahead of the material being included in the national training curriculum.
Material prepared by Rick McRae for AFAC Research Dissemination Pilot Study, March 2012.