Dry Intrusions, Dry Slots, and High Nighttime Temperatures Influenced the Extreme Fire Behavior on the June 2012 Little Bear Fire in New Mexico

The lightning-ignited Little Bear Fire began June 4, 2012 on the Lincoln National Forest (LNF)in south central New Mexico in the Sierra Blanca mountains within the White Mountain Wilderness above the town of Ruidoso. The fuels were mixed conifers and thick, high elevation mountain grasses and the topography was very steep, rocky terrain. After several days of mostly steady, successful fire suppression by ground forces, the fire exhibited extreme fire behavior and large fire growth on June 8, 2012. Due to high nighttime temperatures, abrupt surface drying, and strong, gusty winds, the fire escaped their control lines by means of single tree and group torching lobbing hot embers into receptive unburned fuel beds, in spite of aggressive suppression actions to contain these spot fires. The author hypothesizes that the dramatic and intense downhill and downslope fire behavior that followed was the result of lee slope eddying and fire channeling as described in Australian fire weather literature.

Some dynamic dry intrusions and dry slots were clearly visible on the satellite water vapor imagery (WVI)both preceding the fire's escape and all throughout its dramatic intense downslope fire behavior. Dry intrusions and dry slots are fairly well known to cause abrupt surface to near-surface drying and strong gusty winds as well as Haines 5 and 6. The Southwest area had experienced a prolonged drought in spite of some fairly decent winter moisture.

On June 8th, a NOAA National Weather Service (NWS)Fire Weather Outlook had called for 'critical fire weather' in the Southwest with an approaching lee surface trough accompanied by a dry cold front.

The nearby ROMAN RAWS readings, atmospheric skew-T soundings, NOAA/NCEP/NCAR Reanalysis, and HYSPLIT backward trajectories not only verify the satellite WVI but also reveal a history of high nighttime temperatures, low relative humidity and dew points, and strong, gusty winds that contributed to the extreme downslope fire behavior.

From the perspective of a wildland fire supervisor, satellite WVI is discussed and emphasized as a valuable tool in the realm of operational wildland fire weather forecasting and fire suppression. The first of ten Standard Fire Orders is "Recognize current weather conditions and obtain forecasts." The concept of the 'alignment of forces' of wind, terrain, preheating,and relative humidity espoused in the Campbell Prediction System (CPS)is examined. Also discussed is the 1962 theory that attributes high nighttime temperatures for extreme wildland fire behavior.