Although Hurricane Irene and Tropical Storm Lee have dominated weather headlines during the past two weeks, a longer-term disaster has been unfolding in Texas, where the worst single-year drought on record has intensified - leading to a deadly spate of wildfires that erupted over the holiday weekend. The fires, some of which burned close to Austin, the state capital, prompted Governor Rick Perry to leave the presidential campaign trail to coordinate response efforts.

News reports depict chaotic scenes of fast-moving flames and firefighters stretched thin throughout Texas.

Firefighters from Smithville Fire Department battle a large wildfire on Highway 71 near Smithville, Texas, Monday, Sep. 5, 2011. A roaring wildfire raced unchecked Monday through rain-starved farm and ranchland in Texas, destroying nearly 500 homes during a rapid advance fanned in part by howling winds from the remnants of Tropical Storm Lee. (Erich Schlegel/AP)

In the East Texas community of Gladewater, a blaze killed a 20-year-old woman and her toddler daughter who were caught unawares in their mobile home. A longtime Texas sheriff called the Gladewater blaze the fastest-moving fire he has ever seen. Six homes were toppled within minutes, including the mobile home.

“The houses that were in its path on this particular roadway were taken out,” Gregg County Sheriff Maxey Cerliano said. “There were many other houses that the fire got right up to the porch.”

Forest Service officials estimated some 1,400 acres were burned in that area alone, destroying homes, barns and vehicles, and thousands of other acres were scorched in other parts of the state.

“We’ve completely depleted our resources,” Melanie Spradling, a public information officer with the Texas Forest Service, told the Tyler Morning Telegraph. “We’re on every fire we can possibly handle and then some.”

In Central Texas, the wildfire threat was so dire near Austin that the fire department issued a public appeal asking any and all area firefighters to report for duty.

According to a story in the Post yesterday, authorities were bringing in a tanker plane from as far away as South Dakota to help control the blazes.

Describing the dry and windy conditions in Travis County, sheriff’s spokesman Roger Wade told the Austin-American Statesman, “You light a match out here and you’re going to burn down half the county.”

As of August 30, 81 percent of Texas’ land area was classified as being in the grips of “exceptional drought” conditions, which is the direst category on the U.S. Drought Monitor’s scale. At the end of May, only about 51 percent of Texas was in the exceptional category, illustrating just how significantly the drought expanded and intensified during a summer that featured unrelenting heat and very little rainfall.

81% of Texas was in exception drought as of last Thursday, with 99.9% of the state in at least moderate drought. (U.S. Drought Monitor)

July 2011 was Texas’ warmest month on record, and Amarillo, Houston, Lubbock, and San Antonio all had their hottest summers on record. These cities experienced at least 40 days with temperatures at or above 100 degrees. As Jason Samenow wrote last week, Houston “averages just four 100+ degree days, but tallied a remarkable, record-setting 42 such days in 2011 - blowing by the old 1980 record by ten days.”

UPDATE (1:30 p.m.): Texas (at least preliminary) set the record for hottest summer on record in the lower 48 states. State climatologist John Nielsen-Gammon posted the following to his Climate Abyss blog:

The preliminary numbers from the National Climatic Data Center (NCDC) are in: the Texas average temperature in August was 88.1 F, 2.4 F above the previous warmest August (1952).  This also breaks the all-time record for hottest month in Texas history.  The records go back to 1895, but the previous record, 87.1 F, was set just last month.  Whatever the contribution from urban warming and poor station siting, it’s quite small compared to the temperature extremes we’ve been seeing this year.

Combined, the three months June-August averaged 86.8 F.  This sets the all-time record for hottest summer in the lower 48 states.

The latest climate outlooks through November are not encouraging, with above average temperatures and below average precipitation continuing in Texas and southwestern Oklahoma. Consequently, the Seasonal. Drought Outlook released last week projects that the drought conditions will persist across Texas, with some improvement foreseen only in extreme southeastern parts of the state.

Of course, if one or more tropical weather systems were to make landfall in the “Lone Star State”, that might help the situation. But Texas just can’t catch a break. Instead of dropping beneficial rainfall in parched areas near Houston and Austin, Tropical Storm Lee made landfall in Louisiana, bring upwards of 10 inches of rain there. Worse yet, Texas was on the dry and blustery western periphery of the storm, and the combination of Lee plus a dry cold front was enough to ignite 56 separate wildfires on Sunday alone, which burned close to 30,000 acres, according to NPR.

Doppler estimated rainfall over the last week. Large sections of the countryreceived measurable rain while a large chunk of Texas did not record a trace. (National Weather Ser vice)

The extreme drought and related wildfires in Texas are expected to cost at least several billion dollars, mainly in agricultural losses. As a Time Magazine article details, we may soon start seeing its impacts at the grocery store, with escalating prices for beef products, among other ripple effects throughout the global economy.

A hotter drought because of global warming?

The drought, extreme heat, and wildfires are intertwined. For example, the dry conditions that help create dangerous fire weather conditions also make it easier for air temperatures to rise into record territory, since most of the sun’s energy can be directed towards heating the air, rather than evaporating soil moisture and raising temperatures.

It’s unclear exactly what role global warming may be playing in the current Texas drought, but it’s difficult to dismiss it as a contributing factor to the drought’s severity. La Nina, which is a natural source of climate variability, is the primary suspect for reducing precipitation in Texas during the past year. (La Nina was declared “dead” by the end of May this year, but suggestions that La Nina conditions may return this winter aren’t exactly good news for Texas).

Many climate change studies point to an increased likelihood of droughts in coming years, particularly in the Southwestern U.S. As air and sea temperatures warm, there is an increasing amount of water vapor in the air, which can be wrung out in the form of more intense rainfall events in some areas, but that water vapor is also wrung out of the soil through evapotranspiration, and those regions already at the margin of arid conditions are left high and dry, triggering a self-feeding cycle of drier soils and higher temperatures. In general, with precipitation and climate change, a good rule of thumb is that extremes will become more extreme – heavy rainfall and flooding will be exacerbated, but so too will drought events. Another way it is often explained, wet regions are likely to become wetter, dry regions drier.

Indeed, studies have shown that some of these trends are already evident. Given the extreme heat that has accompanied it, the Texas drought has the characteristics  of global warming-influenced drought, even if – as always – it is hard to unravel the human and natural factors causing the particular conditions.

The bottom line is that as average temperatures increase due to climate change, drought impacts are likely to get worse, and we may be seeing this play out in Texas and other hard-hit areas. As NOAA researcher Marty Hoerling told the media in July, drought plus heat “is just going to make a bad situation that much worse,” since higher temperatures dry soils out much more rapidly. “We haven’t necessarily dealt with drought and heat at the same time in such a persistent way.”