Dynamic Fire Weather Associated with the June 2011 New Mexico (USA) Las Conchas Fire

The Las Conchas Fire began around 1300 MDT June 26th, 2011 on the Santa Fe National Forest west of Los Alamos, New Mexico. The fire was ignited by an aspen tree being blown into a powerline. During the initial 14-hour burn period, the fire grew to around 43,000 acres in mainly timber. Sixty three homes and forty nine outbuildings were destroyed. The fire's astounding rate of spread during the first burn period averaged an acre of forest every 1.17 seconds. The fire continued to grow during the next week before the wet phase of the North American Monsoon set in. The fire was eventually contained on August 11th at 156,593 acres (245 square miles).

The large growth and extreme fire behavior observed on the 26th was the result of several converging weather and fuel variables. Adequate soil moisture during the 2010 growing season provided large amounts of wildland fuel growth. The heavier fuel carried over into 2011. La Nina conditions across portions of the equatorial Pacific helped intensify drought conditions during the winter and spring of 2011 and put stress on the wildland fuels. The fuels became additionally stressed a few days leading up to the start of the wildfire due to abnormally warm and dry conditions associated with a strong mid-level dry intrusion and atmospheric ridging. The energy release component (ERC) value, which is an output of the National Fire Danger Rating System (NFDRS), increased to a record high level. Weather conditions on the 26th were primarily driven by a slight break-down of the upper ridge. A shortwave embedded within a larger long wave Pacific trough translated over the area and brought increased atmospheric instability and upper level winds. The unusually high mixing heights and strong winds led to significant amounts of turbulence and loft for fire brands spotting ahead of the main fire front. Air tanker support to the emerging wildfire was shut down early due to safety concerns. A northerly wind shift tied to a weak cold frontal passage during the overnight of the 26th/27th led to a change in fire spread thus exposing additional areas to fire growth. A Red Flag Warning, which highlights conditions suitable for large fire growth and heightened fire behavior, had been issued by the National Weather Service in Albuquerque. Red Flag Warning issuances are unusual for late June in New Mexico. The Storm Prediction Center and Southwest Coordination Center meteorologists had also highlighted the area for critical fire weather and fuel conditions.

Several datasets will be used to explain the set-ups and extreme conditions observed on June 26th-27th, 2011.