Driest March in Texas history fueling huge fires

Windy, dry and unstable weather conditions are expected for eastern Colorado and New Mexico, eastward to western Kansas, Oklahoma and Texas today--perfect weather for fires. Massive fires continue to rage out of control over large areas of Texas today. Over the past week, the fires scorched hundreds of square miles of rural Texas, destroyed dozens of homes, and sent one fire fighter to the hospital in critical condition. According to the National Interagency Fire Center, 898,000 acres have burned in the U.S. so far this year. This is the 3rd highest burned acreage of the past decade; the record was set in 2006, when a remarkable 2 million acres had burned by April 12.


Figure 1. The Rock House Fire was burning out of control when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite acquired this image on April 10, 2011. Red boxes mark the location of active fires, and brown, charred land shows the fire.s path. A thin plume of smoke streams northeast from the fire front. The burn scar shows that the fire burned around the town of Fort Davis. As of April 12, the National Interagency Fire Center reported that this fire was 80,000 acres and was 0% contained. MODIS also detected a fire immediately northeast of the town of Alpine, in Brewster County, Texas. This fire was 25,000 acres and 0% contained on April 12. Image credit: NASA.


Figure 2. The history of March drought conditions in Texas since 1895, as computed using the Palmer Drought Severity Index (PDSI). The PDSI factors in both precipitation and temperature to come up with a measure of drought severity. Values of the PDSI below -3 are classified as "extreme" drought, and below -4 is the highest classification of drought, "exceptional." This year's drought is the 16th worst March drought in Texas history. Image credit: NOAA/NCDC.

This year's fires caused by heat, drought, and La Niña
When the remains of Hurricane Alex drenched Texas last June, the welcome rains helped fuel a luxurious growth of vegetation across much of Texas during the summer. However, a very cold and dry winter killed off much of that vegetation, leaving plenty of fuel for this spring's fires. With Texas now experiencing the two highest categories of drought, extreme and exceptional, over 60% of its area, conditions are ripe for a record fire season. The percent of the contiguous U.S. covered by extreme and exceptional drought has more than tripled since the beginning of the year, and was near 9% on April 5, according to the U.S. Drought Monitor. An extreme drought is declared when major damage to crops or pasture occurs or widespread water shortages and restrictions. Much of the blame for the drought conditions can be given to the La Niña event occurring the Eastern Pacific. La Niña deflects the jet stream such that the prevailing storm track misses the Southern U.S., leading to dryer and warmer conditions than average during winter and spring. According to the National Climatic Data Center, March 2011 was the driest March and 17th warmest March in Texas since 1895. Temperatures averaged 2 - 6°F above average over most of the state, but over the western portion of the state, where the worst wildfires are burning, temperatures averaged between 6 - 10°F above average. Del Rio has reported only 0.31 inches of precipitation for October - March, the 2nd driest since 1906. Austin reported its 5th driest October - March since 1856, and San Antonio came in as the 12th driest October - March since 1871. Over the last 198 days, from September 26 - April 11, Midland, TX has had measurable precipitation on just five days. Midland's precipitation so far this year stands at just 0.11", compared to a normal of 1.70".


Figure 3. Drought map for April 7, 2011. Image credit: drought.gov.


Figure 4. Winter wheat production for 2010 was heavily concentrated in northern Texas, western Oklahoma, western Kansas, and eastern Colorado, areas strongly impacted by this year's drought. Image credit: U.S. Department of Agriculture.

Drought threatens the winter wheat crop
This spring's drought is heavily impacting the U.S. winter wheat crop, which is concentrated in much of the drought-stricken region (Figure 4.) Winter wheat, which is planted in the fall and harvested in June, accounts for 70% of all wheat plantings in the U.S. The Food and Agriculture Organization (FAO) of the United Nations estimated in March that the 2011 U.S. wheat crop would be 56.6 million tons, 6% less than last year, and the smallest crop since 2007, thanks to the drought. The U.S. wheat crop represents about 8% of the world's total, so a significant reduction of the wheat crop in the U.S. due to a continuation of the spring drought could cause a several percent reduction in the world's wheat supply. Global food prices fell slightly in March, according to the FAO, but still remained among the highest levels since 1990. The drought in the winter wheat areas of the U.S. will create added pressure to this year's high global food prices.


Figure 5. The drought forecast for April, May, and June 2011, issued by NOAA on April 7, calls for drought to spread northwards into all of Kansas and most of Nebraska, and also westwards into most of Arizona and Colorado. Image credit: drought.gov.

A dry forecast
The drought in Texas is likely to get much worse and spread northwards and westwards over the coming months, and will probably rank as one of the top five droughts in Texas history by the time summer arrives. The latest 2-week forecast from the GFS model shows little or no precipitation for the drought region over the next week, with the next chance of significant rains coming April 19 - 20. The latest 1-month and 3-month outlooks from the NOAA Climate Prediction Center show above-average chances for warm and dry conditions over the drought region extending into summer. La Niña conditions are expected to wane and become neutral by June, but the influence of La Niña on the atmosphere will stay strong through June, keeping the preferred storm track north of Texas and causing below-average rains to the drought region. Real relief from the drought of 2011 will likely only occur when hurricane season starts to get going, bringing moisture-laden tropical disturbances or tropical cyclones to the Texas coast in June and July.

I'll have a new post Thursday or Friday.

Jeff Masters