Description

The 24- to 72-hour fire-weather predictions for different regions of the United States are now readily available from the regional Fire Consortia for Advanced Modeling of Meteorology and Smoke (FCAMMS) that were established as part of the U.S. National Fire Plan. These predictions are based on daily real-time MM5 model simulations of atmospheric conditions and fire-weather indices over specific modeling domains. Included in the suite of fire-weather indices provided by the FCAMMS is the well-known Haines Index (HI), an operational 'mesoscale-type' index that characterizes the atmospheric risk of extreme fire behavior based solely on stability and moisture conditions in the lower to middle troposphere. However, there are other atmospheric variables that also influence the risk of extreme fire behavior, especially those that characterize conditions in the atmospheric boundary layer where small-scale fire-atmosphere interactions are so important. One of those variables is atmospheric turbulence (that is, wind gustiness), as measured by turbulent kinetic energy (TKE). TKE can be classified as a 'boundary-layer-type' index, with its generation and dissipation dependent on wind shear and buoyancy conditions near the surface. Like the HI, predictions of TKE are available from the daily FCAMMS MM5 model simulations. This study examines the utility of combining the HI with TKE to assess potential atmospheric risk of extreme fire behavior. Output from the FCAMMS - Eastern Area Modeling Consortium (EAMC) MM5 simulations of fire-weather conditions over the western Great Lakes region is used to identify regional patterns of HI and TKE on a daily basis. A comparison of the patterns of the two indices allows for an assessment of whether large HI values typically occur with large near-surface TKE values, a potentially dangerous fire-weather condition.