Mesoscale model simulations of the meteorological conditions during the 2 June 2002 Double Trouble State Park wildfire Joseph J. CharneyA,C and Daniel KeyserB A USDA Forest Service, 1407 S. Harrison Road, Room 220, East Lansing, MI 48823, USA. B Department of Earth and Atmospheric Sciences, University at Albany, State University of New York, Albany, NY 12222, USA. C Corresponding author. Email: firstname.lastname@example.org Abstract. Late in the morning on 2 June, 2002, an abandoned campfire grew into a wildfire in the Double Trouble State Park in south-central New Jersey. The wildfire burned 1,300 acres, forced the closure of the Garden State Parkway, and caused an estimated $400,000 in property damage. Although there were dead fuels on the ground at the time of the fire, due to a late spring frost, the meteorological conditions at the time of the fire were conducive to erratic fire behavior and rapid fire growth. Surface meteorological observations indicate a profound change in surface atmospheric conditions between morning and early afternoon of 2 June, resulting in a substantial drop in relative humidity accompanied by an increase in surface wind speed in the vicinity of the wildfire. Atmospheric conditions aloft indicate a synoptic-scale trough and an upper level jet streak moving through the eastern United States during the time period. Satellite imagery diagnoses the presence of a ribbon of middle-tropospheric dry air, skew T–log p soundings suggest a deepening mixed layer, and wind profiler observations reveal mixedlayer wind variability. The surface drying and wind variability is hypothesized to result from coupling between a deepening mixed layer and dry, high-momentum air in the middle troposphere that leads to the downward mixing of dry air and high momentum into the mixed layer, which in turn contribute to the observed erratic fire behavior. A mesoscale numerical weather prediction model (MM5) is employed to resolve the meteorological conditions at the wildfire location, as well as the features that precede and accompany the observed weather and fire behavior. The simulation reveals a series of episodes wherein dry, high momentum air aloft mixes down to the ground and contributes to sudden drying and wind variability at the surface. The transitory nature of the features diagnosed in the simulation suggests that coupling between the surface and dry air aloft can have considerable spatial and temporal variability. Maps of the Haines Index and Ventilation Index show that the above-ground processes associated with the erratic fire behavior in this case are not detected by either index, suggesting that new fire weather indices that are sensitive to the meteorological conditions documented in this case could improve fire weather forecasts of similar events. Additional keywords: fire weather, fire weather forecasting, wildfire.