Buckle up for a hot, dry summer

2020 has been quite an unpredictable year, and the weather of the Brazos River basin has proven to be no different.

The upper and central portions of the basin saw abundant rainfall during the winter and the beginning of spring, while the lower region experienced below-normal precipitation and moderate to severe drought. In early May, only 2% of the Brazos River basin was experiencing dry conditions. About a month later, some 56% of the basin was reporting drought conditions with moderate to severe drought conditions in the upper areas of the basin and abnormally dry conditions forming in the central portion of the basin.

The basin’s current drought conditions and precipitation levels are completely different from what we saw in the winter and spring. Throughout June, most of Texas experienced below-normal precipitation levels, with some portions of west Texas having no reported rainfall at all. However, southern parts of Texas experienced 4 to 5 inches above normal rainfall in June.

“The winter and spring were reasonably wet in most of the Brazos River Basin, but the entire spring was dry in the headwaters region and June was dry in most areas,” said State Climatologist John Nielsen-Gammon. “The wet winter and spring should help keep temperatures from getting excessively hot for a while, but the long-term warming trend is still likely to leave us with above-normal temperatures.”

The combination of above-normal temps and mostly dry conditions have led to an increase in wildfire activity. Wildfire analysts with the Texas A&M Forest Service report that these conditions could cause an early and severe summer wildfire season.

“Vegetation is rapidly losing moisture due to consecutive days of extremely high temperatures,” said Brad Smith, Texas A&M Forest Service predictive services department head, in a recent online article. “Grass that was green five days ago has wilted and turned brown under the accelerated drying produced from the extreme heat. It will be quite difficult to replenish this lost moisture during the normally dry months of July and August.”

Of course, a good amount of rainfall could help relieve the state’s dry conditions and reduce the number of wildfires. However, there are no clear answers as to how much rain there will be across the state. Why? The Atlantic hurricane season can overhaul any precipitation outlook for the basin.

The 2020 Atlantic hurricane season was expected to be a busy one, and it still looks that way, says Nielsen-Gammon.

“For hurricane season, the original outlook still looks on track,” he said. “However, there's only about a 50% chance of a named system affecting Texas in any given year, and the odds don't change very much with the hurricane outlook.”

An above-normal hurricane season can be caused by a variety of factors, such as sea surface temperatures and vertical wind shear. And these factors are a result of the El Niño-Southern Oscillation, a climate pattern of changing sea surface temperatures in the central and eastern tropical Pacific Ocean. During the El Niño phase of ENSO, those temperatures are warmer, which suppresses Atlantic hurricane activity. During the La Niña phase, the temperatures are cooler, strengthening hurricane activity.

Currently, ENSO conditions are neutral, with a weak La Niña phase likely to set up by fall. Because of this, the seasonal outlook for fall and early winter calls for the continuation of increased chances of drier than normal conditions and above-normal temperatures.

With the hurricane season, the Brazos River basin’s precipitation levels during the summer months will vary. According to the National Weather Service West Gulf River Forecast Center, there is a higher than normal chance for above-normal precipitation for East Texas. But the rest of the state has equal chances for above normal, below normal, or near-normal precipitation levels. If a tropical storm were to occur in an area, it would push the rainfall average to above normal.

With the busy Atlantic hurricane season and wildfire season, along with COVID-19, the Texas Department of Emergency Management is implementing additional precautions for hurricane season this year. However, the basic principles of hurricane and wildfire preparation still apply, and you can implement them today.

For wildfires:

• Create an evacuation plan for family members, including pets and livestock
• Look for and clear up dead/dry vegetative materials around your property

For hurricanes:

• Know your hurricane risk
• Make an emergency plan with your family—what’s your evacuation route, where are you going to shelter, etc.
• Build a disaster kit
• Get connected with emergency notification systems

As for river flooding and soil moisture levels, Nielsen-Gammon says that there’s currently no place in the Brazos River basin that is remarkably dry or wet. Compared to the spring, where there was no room in the soil to retain water, an average amount of rainfall is not likely to produce runoff with the soil’s current condition.

Despite the warming temperatures and dry conditions, the BRA’s water supply has remained high at 99% full since the spring months, with the majority of reservoir levels in Texas being about 85% full as of July 6. In contrast, reservoir levels around Texas were 81% full in 2018 and 90% full in 2019. The U.S. Seasonal Drought Outlook, curated by the Climate Prediction Center, also shows that the drought conditions in the upper region of the basin will likely improve and possibly be removed by fall.