Homeward Bound: Planes, Weather and a Flight to Catch

Severe weather patterns have serious implications for air travel, but improvements in Earth observation and weather forecasting help airlines plan ahead.

Aviation weather tracking in action at an airline operations center. Image Credit: Federal Aviation Administration

Aviation weather tracking in action at an airline operations center. Image Credit: Federal Aviation Administration

Airlines and passengers want to avoid flight delays and cancellations. Harsh weather poses a threat to this goal and it becomes impossible for some flights to take off or land on time. How do airlines use Earth observation systems to make these tough calls?

When airlines survey the skies and ground for approaching weather events using Earth observation systems, they can plan ahead to see which delays are necessary. Weather tracking is a way to plan for delays or change flight paths to ensure that planes won’t encounter harsh weather like rapidly changing wind currents or atmospheric turbulence. Currents and turbulence accompany strong storms, and without tracking it’s almost impossible to determine future weather patterns.

AIRS image of strong storms forming over the Midwestern United States in May 2015, indicating severe wind currents that caused some airports in the region to cancel flights. Image Credit: NASA Goddard Space Flight Center

AIRS image of strong storms forming over the Midwestern United States in May 2015, indicating severe wind currents that caused some airports in the region to cancel flights. Image Credit: NASA Goddard Space Flight Center

According to Warren Qualley, senior weather expert for Harris Corp. and former manager of weather services at American Airlines, larger airports tend to have more delays than smaller ones. Three New York City area airports (LaGuardia, John F. Kennedy and Newark) together experienced more than 57,000 total delays for calendar year 2013.

Excluding extreme weather events, about 20 percent of all commercial flights are delayed in an average year, all of which impart economic consequences.

“The cost of a delay for a flight is generally up to $80 per minute,” Qualley said.

The Federal Aviation Administration (FAA) reported that weather caused 10 million minutes of delays in calendar year 2013. Since the FAA only counts delays of greater than 15 minutes, this is likely an underestimate of the total impact. This means that weather-related delays cost U.S.-based airlines $800 million per year, according to Qualley.

Those weather delays aren’t necessarily from severe weather. Only 4 percent of all delays are due to extreme weather. Most of the delays  are from what people may consider “normal” weather.

“Normal is a cycle on a washing machine,” said Dr. Bill Patzert, a climatologist and oceanographer at NASA’s Jet Propulsion Lab. “Normal weather is a statistical myth created by averaging by scientists.”

The inherent unpredictability of “normal” weather means that Earth observation systems that track storms and weather are crucial to ensuring safe, timely flights. Currently, agencies like the FAA and the National Oceanic and Atmospheric Administration’s (NOAA) National Weather Service (NWS) provide monitoring programs such as the Weather and Radar Processor (WARP). This program sends information to NWS meteorologists stationed in national Air Route Traffic Control Centers (ARTCCs). Those meteorologists then pass the weather information along to airlines.

Airline meteorologists use forecast information to generate weather maps that can be overlaid with aircraft positions. All airlines have access to weather services including the ones NWS provides, as well as public foreign aviation forecasts for airports and SIGnificant METeorological Information messages (or SIGMETs).

To make sure that information gets where it needs to go, the FAA is continually updating its Next Generation Air Transportation System (NextGen), aimed at making communication of weather and aviation planning easier in ways that include switching from a radio- to satellite-based systems.

The NextGen Weather Processor (NWP) produces images of current weather conditions along with zero-to-eight and zero-to-two hour forecasts. The longer forecasts are used to track precipitation patterns, and the shorter ones to make more specific predictions about how clear flight paths will be.

Before anyone at the FAA or the NWS can make a weather forecast, they have to use Earth observation systems to capture key metrics about current conditions. Richard Heuwinkel, manager of NextGen’s Aviation Weather Division, says that the FAA acquires this kind of information and assesses how usable it is for pilots and operators.

“The FAA and National Weather Service take observations at surface level at airports in about 2,000 locations in the country,” Heuwinkel said. “We look at basic things like temperatures, wind and direction, wind speed, pressure, humidity and so on.”

Above the surface, aircraft can make some observations while in flight and report those to the ground. According to Heuwinkel, this adds up to about 250,000 unique observations every day in the U.S.

The National Weather Service also uses weather balloons in 84 locations across the U.S., Heuwinkel added. “It’s a fairly ancient way of doing business … but they’re very reliable and provide a climate record.”

Balloons can provide important meteorological information for ground-level processes that aviation experts use to inform their forecasts for landing conditions.

Inflating a balloon for upper-air observation. Image Credit: NWS Weather Forecast Office, Green Bay, Wisconsin

Inflating a balloon for upper-air observation. Image Credit: NWS Weather Forecast Office, Green Bay, Wisconsin

The FAA contracts for other types of forecasts like the Integrated Terminal Weather System (ITWS) and the Corridor Integrated Weather System (CIWS), which address the terminal area and the en route area between airports, respectively. The FAA provides access to these systems to airline operations center personnel like flight dispatchers, operations center managers, and meteorologists.

Airlines use this information from the FAA and NWS, but many also have in-house meteorologists. The ones that don’t have private meteorologists can purchase highly accurate weather data from a variety of vendors, all of which Qualley said have significantly improved forecasting abilities over the past few years.

“The biggest changes over the past 10 years have been in the computer models that get converted into forecasts,” said Heuwinkel. The NWS continually upgrades its computer power and forecasting accuracy.

Improved forecasting systems mean that the airlines can work several days in advance of forecasted harsh weather to create a plan detailing whether or not to cancel flights. The latter isn’t totally based on the weather; other factors such as the percentage of passengers on each flight are taken into account.

“If the decision to cancel flights is made, the airline’s reservation group contacts all impacted passengers to help them make alternate flight arrangements which will avoid the airports where adverse weather is expected to occur,” Qualley said. Given that there are about 7,000 flights in the U.S. airspace at any given time, proactive planning through severe weather lets airlines help thousands of passengers and employees.

Sample map of all aircraft in US airspace at a given time. Image Credit: Federal Aviation Administration

Sample map of all aircraft in U.S. airspace at a given time. Image Credit: Federal Aviation Administration

If flights aren’t canceled due to a storm or if that storm comes too late for forecasts to pick it up, the airline can still be proactive. In this case, Qualley said, an airline’s air traffic manager is immediately tasked with creating a plan to help flights get back on track. The air traffic manager then uses weather forecasts to check how long the severe weather events will last and determines how long it will be until they can fly into and out of any given airport. With these forecasts, airlines are now able to make tough calls farther in advance and soften the blow for customers by planning alternate routes.

“Airline operation people realize that weather will always create chaos in their scheduled operations, but one way to mitigate some of the chaos is to plan ahead for it,” Qualley said.

In his experience, that planning has proven very effective in reducing the chaos of unplanned flight cancellations that once left passengers spending hours or days stranded at an airport. The U.S. Department of Transportation (DOT) tracks the reported cause of delays, but separates weather statistics into two categories: extreme weather and National Aviation System problems.

Extreme weather delays are those that prevent flying altogether, and are typically caused by events like hurricanes or tornadoes. National Aviation System (NAS) delays are a larger category; this designation includes all delays and cancellations that result from issues with operational procedures in air traffic control or from non-emergency weather conditions that are not properly dealt with.

Weather events make up 52.3 percent of these NAS delays, meaning that improvements in weather forecasting can reduce the number of total delays . Since 2003, delays from NAS events have gone down 13 percentage points. Even when all weather-related delays are factored in, including unavoidably severe weather, the amount of weather-related delays also declined.

In 2003, weather-related delays made up for nearly 50 percent of all delays, but by 2014 that number had decreased to 32.6 percent. (Check this and other annual aviation data by using the data finder on the U.S. Department of Transportation “TranStats” site.) The percentage of flights arriving on time also has risen since 2003, which means that weather-related delays are affecting not just a reduced percentage of planes but also fewer actual planes overall.

As the NWS increases its forecasting power, these numbers should continue to decrease even further. Fewer weather delays means fewer passengers inconvenienced and fewer profits lost, significantly increasing ease of travel for customers and airlines.

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