Possible easing La Niña and late spring rains could dampen drought

Brazos River, photo submitted by Shaun Holloway

As this past winter has proven, Texas weather can unpredictable, extreme and confusing.

It was anticipated that the beginning of 2021 would continue to have above-normal temperatures and below-normal precipitation through late winter and early spring. That trend may have been the case for most of early 2021, but a week in February took a sharp turn and became one of the most significant weather disasters in Texas' history.

Snow- and ice-covered roads and homes, temperatures across the state hit record lows, millions of people were left without power and water. After a week of unprecedented winter weather in the Lone Star State, temperatures returned to the 50s and 60s the very next week.

But how did all of this happen?

"It started with some cold air sitting over the Arctic in early February," said John Nielsen-Gammon, the state's climatologist and professor at Texas A & M University. "Eventually, the weather pattern set up, so that cold air was continuously being drawn southward from Canada for a couple of weeks.”

Then, Nielsen-Gammon said that the last straw that created this winter storm was a weather disturbance that was strong enough to dislodge and drive the cold air from Canada all the way into Texas.

After February's winter rollercoaster, March weather was relatively stress-free, but the month did not bring the rain needed to relieve the state's drought conditions. In fact, even after February's snow event, precipitation levels mostly remained below normal for most of the Brazos River basin.

According to the National Weather Service West Gulf River Forecast Center, precipitation has been below normal over most of the WGRFC region during the winter months. Only areas across Northeast Texas, the Texas Panhandle, South Central Texas and a small portion of Southwest Texas experienced above-normal precipitation during the winter season.

Looking forward into spring and summer, the consistent trend of above-average temperatures with below-average precipitation is expected over all of Texas. Warmer temperatures and low precipitation levels will likely cause drought conditions to worsen and expand.

"Precipitation, temperature and drought condition forecasts all suggest an expansion and intensification of drought conditions are likely over the next three months," the NIDIS said in a recent report.

As of April 9, 2021, about 91.5% of Texas was experiencing abnormally dry conditions, 74.5% of Texas was experiencing moderate drought, 38.5% of Texas was experiencing severe drought, 23.6% of Texas was experiencing extreme drought, and 8.5% of Texas was experiencing exceptional drought. 100% of the Brazos River basin experienced some sort of drought status as of that date.

Drought can have a severe impact on agriculture, recreational activities, water supply and more. If drought conditions continue to worsen, many aspects of Texans' daily lives will be altered. When severe drought conditions form, pasture conditions become poor, crop yields decrease, and wildlife moves into populated areas. At drought's worst stage, exceptional drought, the seafood, forestry, tourism and agriculture sectors report financial losses, water levels drop significantly, and water quality suffers.

However, Nielsen-Gammon says it's too early to be pessimistic about late spring rains that could relieve the state's drought conditions.

The upcoming months of May and June are typically the wettest months of the year, and even with the possibility of below-normal precipitation levels, there is a good chance that the Brazos River basin will experience rainfall events.

The El Niño-Southern Oscillation (ENSO), the recurrent weather patterns in the central and eastern tropical Pacific that often influence whether Texas will enjoy heavy rainfall or prolonged drought conditions, is currently still in a La Niña status. A La Niña forms when waters in the tropical Pacific Ocean are much cooler than normal, which typically results in warmer and drier weather for Texas.

However, the La Niña weakened through February and March, according to climate.gov. The forecast predicts a transition to ENSO-neutral conditions by the end of spring, although there is a chance that conditions may revert to La Niña later in 2021. ENSO-neutral conditions mean that Texas' weather could tip in either direction.

"As we get into spring, the influence of La Niña weakens, so the weather patterns will stop favoring below-normal rainfall. At the same time, it looks like La Niña will be weakening too," Nielsen-Gammon said. "This basically means that we have no clue what's going to happen to rainfall in Texas from May onward. The dry soils in many areas will inhibit the development of thunderstorms while also making it harder for heavy rain to produce flash flooding. During April and May, in particular, weather systems are strong enough to generate their own rainfall, no matter what's happening on the ground."

Aaron Abel, the Water Services Manager at the Brazos River Authority, said in the recent virtual public meeting that regardless of the continuation of drought conditions and lack of significant rainfall, the BRA's Water Supply System stays in good shape heading into late spring and early summer.

As of April 7, the BRA system is 97% full and storing about 1.87 million acre-feet of water. Lake Georgetown and Lake Somerville remain under Stage 1 Drought Watch, which are in place to raise customer and public awareness of drought conditions.

"We’re in a good position right now,” Abel said. “Everyone is hoping for some rain, and I think we’ll get it.”

The above-normal temperatures will persist for the foreseeable future due to the long-term warming trend. In fact, Nielsen-Gammon said that due to this persistent warming trend, the definition of “normal” temperatures will no longer be based on average conditions in 1981-2010 and instead be updated to average conditions in 1991-2020.

“Since the last decade was warmer than temperatures in the 1980s, the new normal will be warmer too,” Nielsen-Gammon said.

The combination of warmer temperatures, statewide drought conditions and lingering La Niña conditions could lead to an early, intense wildfire season. A bad wildfire season requires wet conditions followed by dry conditions. The other thing you need is a day of bad fire weather—strong winds with very low humidity.

“Until the rains come and the grasses green-up, every dry and windy day means a risk of fires starting and rapidly spreading. So far, areas from I-35 southeast have greened up nicely, but northwest of there, the wildfire risk is still present,” Nielsen-Gammon said.

You can stay up to date with rainfall, streamflow and reservoir elevation data within the Brazos River basin by clicking here. For helpful resources about dealing with drought, click here.