From summer to winter: El Niño’s staying power in the Brazos River Basin

It's official: El Niño conditions are here and likely to intensify through the winter. But how will this affect the Brazos River Basin, our reservoir levels and water supply?

Aaron Abel, Brazos River Authority's water services manager, recently explained that, moving into the hottest part of the summer, water stored in BRA reservoirs is ample for the upcoming year, with storage at 97% full as of July 1st.

"We're in good shape going into the summer, except for Possum Kingdom Lake and Lake Proctor, which are below full due to a lack of rain in those areas," Abel said.

Now, El Niño is increasing storm chances across the basin.

Though some forecasters are referring to the current El Niño event as a possible "super El Niño," as of now, that's not a thing. The National Oceanic and Atmospheric Administration (NOAA) categorizes La Niña/La Niña conditions as weak, moderate, strong, and very strong.

According to John Nielsen-Gammon, Texas State Climatologist and director of the Southern Regional Climate Center at Texas A&M University, "The official forecast has a 63% chance of the El Niño becoming very strong. The last El Niño we had was in 2015-2016. Before that, we had El Niño weather conditions in 1997-1998, 1991-1992, 1982-1983, 1972-1973, and 1957-1958."

He explains, "Average conditions during those events for the Brazos River were drier than normal July to August, wetter than normal October to February, and cooler than normal October to May."

"We're in a somewhat wetter pattern right now," Nielsen-Gammon said. "But that is expected to go away by the middle of July. Typically, western and central Texas reservoirs decline during the summer, and I expect the same this year. As of June 29, the NINO 3.4 (°C) index was already at 1.2 (°C), which would correspond to a moderate El Niño."

The NINO index he references is the Oceanic Niño Index (ONI), NOAA's primary indicator for monitoring the ocean component of the seasonal climate pattern called the El Niño-Southern Oscillation (ENSO).

The ONI tracks the three-month running average sea surface temperatures near the International Dateline within the equatorial Pacific Ocean to determine whether they are warmer or cooler than average.

NOAA recognizes El Niño conditions when ONI reaches +0.5 degrees Celsius or higher, indicating that surface waters in the east-central tropical Pacific are at least 0.5 degrees Celsius above the long-term average.

On the other hand, oceanic La Niña conditions occur when the ONI is -0.5 degrees Celsius or lower, meaning the area is at least 0.5 degrees Celsius cooler than the average.

El Niño conditions create above-normal sea surface temperatures, which typically lead to above-normal rainfall for Texas in late fall and winter.

What does El Niño mean for hurricane season?

NOAA suggests that historically, the summer before an El Niño winter has seen less tropical storm activity over the Gulf.

Abel explains, "El Niño suppresses thunderstorm development and leads to below-normal hurricane activity. NOAA predicts 8-14 named storms, 3-6 hurricanes, and 1-3 major hurricanes."

To see the water levels for all reservoirs in the Brazos River Basin, the BRA's BrazosBasinNOW website compiles data from various gauges, presenting information in real time, providing streamflow, reservoir levels, and rainfall amounts throughout the basin. Click here to see current conditions within the Brazos River Basin.

In a nutshell, El Niño patterns often bring cooler, wetter fall and winter weather to Texas as warmer ocean waters influence atmospheric conditions. Though Texas appears to currently be experiencing moderate El Niño conditions, meteorologists and climatologists are closely tracking signs of conditions changing to a potentially strong El Niño that could persist through the end of the year.