  The current WRF-Fire model starts the fire from a given ignition point at a
given time. We want to start the model from a given fire perimeter at a given
time instead. However, the fuel balance and the state of the atmosphere depend
on the history of the fire. The purpose of this work is to create an
approximate artificial history of the fire based on the given fire perimeter
and time and an approximate ignition point and time. Replaying the fire history
then establishes a reasonable fuel balance and outputs heat fluxes into the
atmospheric model, which allow the atmospheric circulation to develop. Then the
coupled atmosphere-fire model takes over. In this preliminary investigation,
the ignition times in the fire area are calculated based on the distance from
the ignition point to the perimeter, assuming that the perimeter is convex or
star-shaped. Simulation results for an ideal example show that the fire can
continue in a natural way from the perimeter. Possible extensions include
algorithms for more general perimeters and running the fire model backwards in
time from the perimeter to create a more realistic history. The model used
extends WRF-Fire and it is available from openwfm.org.
