Changing weather patterns and shifting jet streams likely portend greater risk for turbulent skies for business aviation in the next few decades. With the potential for such conditions expected to worsen, operators should utilize the latest tools to predict areas of turbulence.
One resource is the Aviation Weather Center (AWC) operated by the National Oceanic and Atmospheric Administration (NOAA) and National Weather Service (NWS). AviationWeather.gov offers a wealth of weather information, including convective forecasts and an interactive Flight Path Tool that disseminates all weather products available for a given route.
“We’ve made tremendous advances over just the past few years, thanks to improved weather forecast models with more data going into [them] and better understanding of the science in these models,” said Jennifer Stroozas, warning coordination meteorologist for NOAA’s AWC. “That results in better forecast information across the board, including when evaluating the potential for turbulent conditions.”
One result of this effort is the Graphical Turbulence Guidance tool that lists SIGMETs (significant meteorological hazards) for turbulence and pilot reports in both graphic and text formats, ranging from 1000 feet above ground level up to 50,000 feet.
Graphical airman’s meteorological information, or G-AIRMETs, provide greater understanding not only of areas with predicted turbulence, but also the mechanical factors that drive such forecasts.
“We've definitely seen improved NOAA and NWS forecasts over the past decade through use of ensemble prediction tools and more data.”
Dean Snell Manager, NBAA Air Traffic Services
Dean Snell, manager of NBAA Air Traffic Services at the FAA’s Air Traffic Control System Command Center (ATCSCC) in Warrenton, VA, noted these tools benefit not only pilots, but also those tasked with routing traffic and assisting operators throughout the national airspace system.
“We’ve definitely seen improved NOAA and NWS forecasts over the past decade through use of ensemble prediction tools and more data,” Snell said. “They’re able to take that information and assemble it in new, more accurate products that provide better predictions.”
Turbulence occurs with rapid variations in wind speed and altitude, creating wind shear. “Those can be quite large,” said Dr. Paul Williams, professor of atmospheric science in the Department of Meteorology at University of Reading in the United Kingdom. “In scale, we’re looking for rapid variations in wind speed and altitude that create wind shear.”
“You must understand that air is a fluid, just not one as thick as water,” said Jeff Wofford, CAM, and former chair of the NBAA Safety Committee. “A river might be nice, smooth and calm, or you might encounter ‘rapids’ that make the current choppy and bumpy.
“The exact same thing happens with the air,” he continued. “As wind speed increases, and it goes over topographic obstacles like mountains, things get stirred up and that causes eddies and turbulence. Especially in the Rockies during wintertime, you get into mountain wave situations even up at 35,000 feet.”
New and Future Tools
Another, relatively new forecasting turbulence method involves tracking eddy dissipation rates that stimulate turbulence. “These are little swirling air currents or vortices that are about 200 meters in length,” Williams said.
While current atmospheric models offer a typical resolution of a few kilometers in a three-dimensional mesh, Williams noted these still capture the processes that generate turbulence. “Once we know where the wind shear is from the forecasting model,” he continued, “we have a set of equations we can use to figure out the turbulence.”
Clear air turbulence (CAT) poses further challenges. “Thermal[-driven] CAT is difficult to predict as it’s on the microclimate scale,” Stroozas said. “Other clear air turbulence is associated with a jet stream, which is more prominent in the wintertime. While we can’t see it, we know that changes in wind speed and direction cause it, and we have models to give us an idea where that may be.”
Near-future technologies also hold promise for better detection of CAT, although with some caveats. “LIDAR (Light Detection and Ranging) works similar to radar but uses ultraviolet light that can reveal CAT up to 20 miles ahead,” Williams said. “That’s not very much time, but it’s enough to put the seatbelt sign on.”
However, “LIDAR is also very expensive technology inside a big, heavy box,” he added. “That’s why it’s not being used to large scale currently, but it does work.”
Back to Basics
While technological improvements have driven advances in predicting turbulence, Stroozas noted that traditional tools like radar, satellite observations and PIREPs remain at the heart of all aviation weather forecasts.
“We’re able to better drill down on certain areas, and the different algorithms that are now available allow us to watch for different signals to what’s happening as the weather of the day unfolds,” she said. “There’s also a variety of different weather models that are available to aviation weather forecasters to try to detect some of these signals out in the future, including forecast models specifically for turbulence.”
Those improved forecasts are most welcome for pilots. “When I did my PhD on turbulence 20 years ago, pilots told me they simply ignored the turbulence forecasts because they were so often wrong,” Williams said. “They were about 60% accurate back then; now, we’re closer to 85%.”
Commercial resources are also available. As one example, SmartSky Networks recently introduced its SmoothSky tool that disseminates crowdsourced, off-aircraft data to provide real-time turbulence avoidance information, similar to apps like Waze that assist drivers on the ground.
“The most important tool we have is a Mark One-model eyeball. If you take a proactive stance versus reactive, you're going to be a lot better off.”
Jeff Wofford CAM, Former Chair of the NBAA Safety Committee
Wofford urged pilots to also remember the basics from their earliest days of flight training. “Get a good weather briefing,” he said. “If you’re doing a self-briefing, look at all the charts, and understand what you’re dealing with for that particular flight.
“The most important tool we have is a Mark One-model eyeball,” Wofford continued. “If you take a proactive stance versus reactive, you’re going to be a lot better off.”
That further reinforces the importance of having NWS personnel at the ATCSCC. “They’re on the floor to help air traffic managers determine the specific trouble areas,” Snell said. “If reported turbulence is moderate or above, we’re able to take that information and determine if reroutes are needed to get aircraft around those areas.”
“The weather never stops,” Stroozas concluded. “We have such a dedicated team of aviation weather meteorologists, and they have such expertise in this area. By keeping an eye on the sky, we can make sure we’re helping keep everybody as safe as possible.”
Study Points to Even More Turbulence Ahead
A June 2023 research project published by the University of Reading and the American Geophysical Union revealed significant increases in clear air turbulence (CAT) over the past 40 years, an ominous indication of what’s likely to come in the future.
Study co-author Dr. Paul Williams noted the largest increases came over the United States and the North Atlantic, with a 55% increase in severe-or-greater CAT in 2020 compared to 1979.
That not only poses added risk of physical injury to cabin crew and passengers, he said, but also increased operational costs and more emissions as the aviation industry works to reduce its carbon footprint.
“A 2007 study about the impacts of turbulence found up to two-thirds of commercial flights [within the survey window] had deviated from the most fuel-efficient altitude because of turbulence, with an average duration of 41 minutes,” he added. “So, there’s certainly a cost implication here.”
Turbulence may also cause greater airframe and component fatigue, which even in the best-case scenario requires more frequent inspection intervals. Passengers already uneasy about flying may become more unnerved by even mild encounters with turbulence, Williams added.
The Aviation Weather Center (AWC) recently launched an experimental trial version of its new and improved AWC resource that offers an even more informative and easy-to-use interface, available at beta.aviationweather.gov.
The new site is expected to formally go live in September.
International Business Aviation Council Ltd.