# The Spotting Distribution of Wildfires
## 1 Introduction
### The Havoc Caused by Spotting
Spotting can also cause an increased rate of spread across a region which might otherwise slow the fire's progress, as might happen if a crown fire front encounters an extended slash region, across which local spread would be much slower. On the other hand, slash is notorious for spotting, which in this case could allow the fire to reach the slash boundary faster relative to local spread alone. When conditions aloft are favorable for strong convection column development [15], or large-scale fire-induced vortices (fire whirls) exist [16], spotting may contribute significantly to a fire's spread. A spot fire 29 km downwind of an existing fire in Victoria, Australia appears to be the longest recorded spot fire event [11]. As reported by [PERSON] [9], the Ash Wednesday fires in Australia, which occurred on the 16 th of February 1983, produced spotting distances of between 5 and 12 km, with the most extreme incident measured being 25 km from the primary fire. While these extreme long-distance dispersal events cannot be seen to drive a front's _rate of spread_, they dramatically increase fire danger. It may take fire suppression crews a long time to reach such fires, increasing their likelihood of growing to a full blaze. Accurate wind-transport models for combusting firebrands, operational in real time and with access to accurate wind information, are in demand to help improve spotting forecasts in such situations. As mentioned above, coupled fire-atmosphere models [2; 17; 18] may provide an improvement to static fluid dynamic computations currently employed in operational front prediction software (for North American examples see [19; 20]). Indeed, Large Eddy Simulations (LES) coupled with firebrand dispersal have shown that the fire plume may be quite different from the plume used in standard models like the Baum and McCaffery plume [21], leading to different firebrand trajectories [22; 23; 24]. In addition, there is an extensive literature covering empirical measurement of plume characteristics; extensive measurement of plume heights and characteristics in [25] compared a variety of plume models (different from Baum and McCaffery) against measurements for approximately 2000 wildfire plumes. The results showed an unexpected importance of the lower limit of the atmospheric boundary layer, as well as a perplexing independence of plume injection heights on wind, but also a non-neglibble fraction of plumes whose structure could not be determined by the models employed. Comparison of model output versus experimental observation, coupled with the development of increasingly sophisticated plume models, provides a promising paradigm involving experiment and modelling which must be further employed in addressing the challenging processes which drive wildfire spread. As a final, very important note, there are examples in the literature, which indicate that spotting can at times lead to the _acceleration_ of a fire's rate of advance. During the Beerburrum Fire No. 48, which occurred in Queensland Australia in 1994, the firefighters observed \"Spotting... accelerated its rate of spread and its advance was halted only by Pumecestone Passage\" [9]. The issue of acceleration in local spread caused by the addition of a non-local spread mechanism is not new in for invasion ecology since the seminal paper by [PERSON] _et al._, [26], but the possibility of acceleration is an important open, unaddressed question in the context of wildfire spreading with spotting.