Wildfire Outbreak of February 27th, 2011
On Sunday, February 27th, 2011, New Mexico and Texas endured a wildfire outbreak on a grand scale. Wildfires were reported from Dalhart to Ozona, and from Roswell to Cisco. Around one quarter of a million acres were burned, and 80 homes were destroyed along with numerous commercial buildings. One fatality occurred due to an automobile pileup on Interstate 20 near Midland caused by reduced visibilities from wildfire smoke and blowing dust. This outbreak of wildfires was caused by a combination of very strong winds, hot temperatures, dry air and persistent drought conditions.
A powerful upper-level low pressure system moved across the southern Rockies, pushing a dryline through all of west Texas. This resulted in relative humidity values of 10% or less with west winds that helped warm surface temperatures well into the 80s. While the surface pressure gradient was not exceedingly strong, this very dynamic system contained very strong winds throughout the depth of the atmosphere which mixed to the surface supporting sustained winds of 30-45 mph with gusts over 60 mph from the Texas Panhandle south through the plains near Lubbock and into the Permian Basin.
The two images below show atmospheric soundings from Amarillo early in the morning and early in the evening on 27 February 2011. The purpose of these images is to show how strong winds aloft moving over the area were able to "mix down" to the surface. In the first image, there is an inversion near the surface. This inversion acts as a 'lid' in the lower atmosphere. When an inversion is in place, atmospheric conditions above that inversaion are not able to 'mix' down to the surface. And in fact, when looking at the winds, you can see that they are only 10 knots at the surface while they are 25 knots to 40 knots above the inversion. The inversion is preventing those stronger winds from affecting the surface. In the Amarillo sounding below, one can see that this inversion is very shallow, which means that once the heating started to take place, this inversion would be erased quickly, and when it did, the stronger winds above the surface would be able to make their way to the surface. This is why the strong winds started during the morning hours across west Texas. The second image shows the Amarillo sounding at 6 PM. The sounding no longer has the inversion, and you can see that the winds have increased to 35 knots at the surface and are similar in speed and direction to the winds above the surface. The strong winds moving over Amarillo were present across all of west Texas that day.
|Figure 1. Skew T sounding at Amarillo early in the morning on February 27th, showing the inversion. (Click image to enlarge)||Figure 2. Skew T sounding at Amarillo showing a 'freely mixed layer' late in the afternoon on February, 27th. (Click on image to enlarge)|
In addition to the strong winds, visibilities were severely restricted due to blowing dust (especially around recently harvested cotton fields) and smoke from the wildfires. In west central Texas, winds were 30 to 40 mph with gusts near 50 mph. All this wind combined with temperatures warming into the upper 80s and relative humidity values of 5 to 10 percent. The winds, heat, dry air, and abundant fuels all combined to create an explosive environment for wildfire development. The satellite images below show blowing dust and smoke plumes during the afternoon of 27 February 2011.
Figure 3. Smoke Plumes between Lubbock and Amarillo. (Click to enlarge)
Figure 4. Smoke plumes near Midland. (Click to enlarge)
Figure 5. Area of Blowing dust between Midland and Lubbock. (Click to enlarge)
Specifically in west central Texas, we experienced at least 3 separate wildfires. One fire consumed roughly 300 acres near Lake Stamford and destroyed two unoccupied buildings. Another fire occurred in southwestern Irion County and threatened the town of Barnhart. As the fire approached the community of Barnhart, emergency officials placed the village on standby for possibly evacuations, prompting the issuance of a Fire Warning from NWS San Angelo. Fortunately, area firefighters were able to keep the fire from moving into Barnhart, and no evacuations were necessary. The exact acreage on the fire in Irion County is unknown, but was estimated at less than 3,000 acres. The third and largest fire, named the Williams Fire, occurred in northeastern Crockett County. The Williams fire burned 22,958 acres, beginning late in the afternoon on Sunday and continuing into the morning hours on Monday, February 28th. Minimal damage was sustained from the southern fires as they burned mostly in open rangeland. A pipeline was threatened by the Williams fire, but firefighters were able to protect it. The image below shows the fire scars from the two major fires that affect west central Texas.
The wildfire outbreak was a result of a combination of factors. The main factor was of course, the dry, hot, windy conditions. But in addition to the present weather on Sunday, conditions over the last year also contributed. Over the last year, many locations across west Texas were wetter than normal, which was followed by a drier and warmer fall 2010 into winter 2010/2011. This has lead to a significant amount of fine fuels (grasses, shrubs, etc.) for fires to consume. In addition, since we were in late February, most of the vegetation was dormant, which would also lead to conditions conducive to burning.