Description

The six standard relative numerical ratings of the Canadian Forest Fire Weather Index (FWI) System associated with a prescribed fire previously reported on in the literature (Woodard, P.M., Bentz, J.A., Van Nest, T., 1983. Producing a prescribed crown fire in a subalpine forest with an aerial drip torch. Fire Management Notes 44(4), 24-28.) have been recomputed based on all the available weather data, in addition to being updated in terms of the current edition of the FWI System. This case study approach has been taken in order to illustrate the importance that fire danger rating information should play in the formal prescribed burn documentation process. A key feature in this particular retrospective analysis was the manner in which the previous day's fuel moisture codes, which are required as starting values for FWI System calculations, were estimated (in the absence of pre-burn fire weather monitoring) for the actual site using the observations from nearby fire weather network stations. This information was combined with the on-site fire weather observations on the day the prescribed fire took place in order to quantify the burning conditions in terms of past and present weather influences that prevailed just prior to and/or during the ignition phase of the prescribed burning operation according to the three fuel moisture codes and three fire behavior indexes comprising the FWI System.