Meteorological Drivers of Rapid Wildfire Growth in Alaska's Boreal Forest

Hundreds of thousands of acres of the boreal forest of Alaska’s Interior burn each summer. In big fire years, a few hundred thousand acres can burn in a single day. Rapid wildfire growth events such as those, defined in this study as days where acreage burned exceeded a prescribed number of standard deviations above the daily mean, have historically been difficult to forecast from a fire weather perspective. North American Regional Reanalysis (NARR) data were utilized to identify synoptic patterns associated with rapid wildfire spread events in Alaska and that show semblance of forecastability. It was found, unsurprisingly, that a pattern of anomalously high temperatures and low relative humidity tends to be present during days of rapid wildfire growth. Such conditions prime the coniferous fuels, turning black spruce stands into matchsticks. More surprisingly however, a weak pressure pattern consistently appears during rapid fire growth events, leading to the supposition that more than just pressure-gradient-driven winds propel wildfires through the primed fuels. Daily indices of teleconnection patterns, obtained from the Climate Prediction Center, were tested for the emergence of forecastable phase biases during and prior to events of rapid fire spread. Statistically significant phase biases of the North Atlantic Oscillation, Pacific North American Pattern, and Arctic Oscillation, but not the Madden-Julian Oscillation were found to be present prior to and during days of rapid fire growth when compared to climatology, implying a degree of forecastibility. Further, quantitative, synoptic analyses were also performed.