After three long years of being in the La Niña weather cycle, the National Weather Service officially announced our entrance into the El Niño weather pattern in June of 2023.
So you might have heard that we have entered into the El Niño phase of the El Niño-Southern Oscillation (ENSO) climate pattern and are curious what that means for us. The ENSO is a climate pattern relating to changes in the temperature of water in the central and eastern tropical Pacific Ocean. These changes have big impacts on our weather here in Central Texas; get ready for some wet weather!
“El Niño conditions have developed, as the atmospheric response to the warmer-than-average tropical Pacific sea surface kicked in over the past month. We expect El Niño to continue into the winter, and the odds of it becoming a strong event at its peak are pretty good, at 56%. Chances of at least a moderate event are about 84%.”
Understanding El Niño and La Niña
What exactly are El Niño and La Niña? The ENSO is composed of three phases; El Niño, La Niña, and Neutral. The extreme phases of the ENSO are El Niño and La Niña. These phases bring with them distinct impacts to our weather patterns and help to predict what weather conditions we might expect in each phase.
El Niño
El Niño is characterized by warmer than normal sea surface temperatures (SSTs) in the central and eastern equatorial Pacific. This warming of the ocean surface disrupts the normal atmospheric circulation patterns and has far-reaching impacts on weather and climate around the globe.
During El Niño, the trade winds that usually blow from east to west across the equatorial Pacific weaken or even reverse. This weakening allows warm water from the western Pacific to move eastward towards the South American coast. As a result, the warm surface waters in the eastern Pacific expand, and the thermocline (the boundary between warm surface waters and cooler deep waters) becomes shallower.
The changes in the oceanic and atmospheric conditions associated with El Niño brings a range of effects, including:
1. Changes in precipitation patterns: El Niño can cause shifts in global rainfall patterns, leading to increased rainfall over parts of the central and eastern Pacific, including the southwestern United States, (that’s us!) and reduced rainfall in other regions, such as the northern U.S., Canada, and Australia. The last El Nino cycle was 2015 when we experienced much higher than normal rainfall and the flood events that characterized that year.
2. Temperature anomalies: El Niño events can lead to below average temperatures in regions such as the southwestern United States and South America and above average temperatures in other regions.
3. Impact on tropical cyclones: El Niño can suppress tropical cyclone activity in the Atlantic basin but enhance it in the eastern Pacific.
La Niña
La Niña is a climate pattern that is the counterpart of El Niño. It is characterized by cooler-than-normal sea surface temperatures (SSTs) in the central and eastern equatorial Pacific, particularly along the coast of South America. Like El Niño, La Niña also has significant impacts on weather and climate patterns globally.
During La Niña, the trade winds blowing from east to west across the equatorial Pacific intensify, pushing warm surface waters toward the western Pacific. This intensification enhances the upwelling of cold waters along the South American coast, leading to even colder SSTs in the central and eastern Pacific.
The changes in oceanic and atmospheric conditions associated with La Niña result in several effects, including:
1. Changes in precipitation patterns: La Niña tends to cause shifts in global rainfall patterns. Often leading to decreased rainfall in the central and eastern Pacific, such as over the southwestern United States and South America, and increased precipitation in the western Pacific, including parts of Southeast Asia and Australia. The drought of the last several years here in central Texas and the increased rainfall in California is a direct result of the extreme La Nina we recently exited.
2. Temperature anomalies: La Niña events can lead to above average temperatures in regions such as Central and South America and below average temperatures to other regions.
3. Influence on tropical cyclones: La Niña typically enhances tropical cyclone activity in the Atlantic basin, increasing the likelihood of hurricanes and storms, while reducing it in the eastern Pacific.
La Niña and El Niño events can last for several months to even years, as their intensity and duration vary. For the past several years we have been in the La Niña phase of this cycle. During this time we have experienced extreme drought conditions here in central Texas. With the news of this switch, many of us are celebrating as the El Niño typically brings precipitation for us in the Hill Country.
“After a particularly extended stay, the La Niña weather phenomenon that’s persisted for the past three years, contributing to extreme weather worldwide, has finally come to an end.”
El Niño and La Niña Effects on Central Texas
But if this weather pattern is based on the temperature of the Pacific Ocean, why should we in Central Texas care? Here is what hydrologist Dr. Mark Wentzel has to say,
"El Niño and La Niña, that whole cycle, that is really just looking at sea surface temperatures in a large area of the eastern Pacific. And that's quite a distance away from us. So, it wouldn't seem like it would have any relevance to us. But what it does is the temperature conditions in that part of the ocean sets up circulation patterns in the atmosphere, and those patterns are what bring us extra moisture from the Pacific. They’re patterns that may suppress hurricanes from coming to us from the Gulf. They may influence the jet stream that is bringing cool air down to us from the north. So, in combination, El Niño/La Niña influence weather patterns all over the globe, they mean different things to different people, different areas. But for us, La Niña conditions, the warmer temperatures in the eastern Pacific, those really correlate to warmer and drier winters than we would typically experience."
One of the primary effects of La Niña to us in Central Texas is the increased risk of drought. During La Niña phase we typically experience below-average precipitation, in addition La Niña can bring about warmer temperatures and increased heat extremes. The combination of reduced rainfall and increased evaporation due to the warmer temperatures can exacerbate the potential for droughts in our area, which we have seen first hand over the past couple years.
Conversely, El Niño, the counterpart to La Niña, has its own distinct impacts on our weather patterns in central Texas, mainly, increased precipitation and the risk of flooding. During El Niño, the trade winds weaken, causing warm surface waters to shift eastward across the Pacific Ocean. This shift typically brings an influx of moisture and above-average rainfall to us over in central Texas. Whereas with La Niña we expect warmer temperatures, during El Niño we can expect cooler fall and winter temperatures in the Texas Hill Country.
“It would bring cooler and wetter conditions in fall and early winter. During most El Niño years, threats of hurricanes are possible in Texas, but pose a very low threat of making landfall, according to White" (Keith White with the Austin/San Antonio National Weather Service)
*It is important to note that while these are the typical effects of La Niña and El Nino weather patterns on Central Texas, the actual weather conditions may vary from one event to another. The intensity and duration can influence the magnitude of its impacts.*
Learning from the Past
The 2015 Memorial weekend flood was a historic and catastrophic event in central Texas. One of the largest recorded floods in the state. Our region was oversaturated with record breaking rainfall and floods broke loose across the area.
The Weather Event Summary by the Austin/San Antonio Weather Forecast Office states, “A persistent weather pattern from the beginning of May began to set the stage for a more concentrated and more impactful flash and river flooding event. May 2015 will go down in history as one of the wettest months across the state of Texas. For the first two to three weeks of the month, most locations across south-central received well-above normal rainfall that saturated the soils. By the time Memorial weekend arrived, much of the region was at least 2-4 inches (100-300%) above normal. These wet antecedent conditions meant that any new rain and especially heavy rain would become run-off directly into rivers, streams, and flash flood prone areas.”
According to the National Weather Services rainfall records for the Austin area, in 2015 we received 59.96 inches of rain (quite the jump from our yearly average of around 36 inches).
As it turns out, all of this wasn’t just happenstance, we were being affected by the El Ninõ that was declared earlier that year. Record floods, hurricanes, droughts and other extreme weather events erupted across the globe in addition to what we experienced here in central Texas.
“While the events were scattered across the globe, they all had one thing in common: they were all connected to one of the three strongest El Ninõs in the historical record.”
Let’s take a look at some of our other record breaking numbers; in 2011 the Austin area received only 19.68 inches of rainwater and in 2008 we received 16.07 inches, La Niña’s were present in both of these years. As we look at the history, it’s no question that these weather patterns have a big impact on our weather, even here in the Texas Hill Country.
Many experts attribute the drought conditions we have experienced in recent years to the La Niña that we recently exited. With the announcement of El Niño in June of 2023, it seems that things are looking up in terms of rainfall for central Texas. We have already seen a shift in our weather with our monthly rainfall totals having doubled for April and May of 2023 from last year.
For the past several years we have seen extreme drought conditions throughout the area, showcasing just how precious of a resource water can be for a community. Whether it’s too much or not enough, understanding our weather patterns can help us to plan and prepare for a more secure water future. To learn about how harvesting rainwater can benefit central Texans, check out our previous blog The Importance of Rainwater Harvesting in Central Texas
Working with Our Weather
Something that has really become clear over the past several years is the importance of learning how to work with our weather patterns and natural resources. We know that central Texas is subject to extreme conditions when it comes to our rainfall patterns. So the question becomes; how can we build our resilience, work with our weather patterns, and conserve the natural resource of water?
Rainwater harvesting allows us to do just that. It allows us to capture during times of abundance and store for times of scarcity. Not only does it help reduce our reliance on municipal water supplies and our strain on aquifers, but it can even aid in managing stormwater during the seasons of excess.
While many Texans experienced dry wells from the drought, those with rainwater harvesting systems have still had access to water. Utilizing a rainwater harvesting or catchment system is a great way to increase your resilience while working with these extreme weather conditions.
Our Recent Transition from La Niña to El Niño
After struggling with extreme drought conditions, the announcement of a shift into El Niño is good news for central Texas.
“After three years of severe weather brought on by the effects of La Niña, the Climate Prediction Center has officially declared the end of La Niña's warm and dry weather wrath”
Time will tell what this particular El Niño will bring for us, but based on history we should expect increased rainfall coming into the fall and winter, with Keith White (a lead forecaster at the National Weather Service's New Braunfels office serving San Antonio) saying “Later this year, we'll likely see cooler and wetter conditions, which is good for those areas around us in need of more rain. Despite the rains this spring, we're still in an exceptional drought."
Could this El Niño be exactly what central Texas needs to recover from the drought? We sure hope so!
At the time of this writing, June 22, 2023, we can already tell there is a shift in our atmosphere, with late season heavy rainfalls the past two days. Overall, we welcome the change with open arms and are hopeful that this shift can give our land and rivers some time to heal after an intense La Niña phase.
Resources:
Climate Prediction Center | National Weather Service
National Weather Service | National Oceanic and Atmospheric Association
Texas Water Newsroom
CW 39 Houston
Climate.gov | Science and Information for a Climate-Smart Nation