Critical Flaws Bared in Aviation Tornado Warning System

One year ago, a violent tornado struck Lambert-St.Louis International Airport, exposing hundreds of passengers to danger from flying debris in the concourses as well as onboard aircraft sitting on the tarmac. Despite a half-hour heads up from the National Weather Service, the airport authority never warned passengers of the approaching twister, and the tornado warning was not relayed to pilots either. Damage to one of the concourses was so severe — the EF-4 tornado peeled away a section of the roof from the one of the concourses and blew out the large windows in the main terminal — that repairs were only completed earlier this month.

The St. Louis tornado was supposed to be a wakeup call for the aviation and weather communities. Yet three weeks ago, the same perilous scenario was repeated at a different airport, this time at Dallas-Ft. Worth International, the eighth-busiest airport in the world. There, a severe thunderstorm on April 3 that was showing signs of producing a tornado tracked directly over DFW, and while airport officials succeeded in warning passengers in the concourses and ushering them to safety, there are indications that there was a failure to inform pilots of the severity of the approaching storm.

Radar images and explanation for the tornadic thunderstorm that struck DFW Airport on April 3, 2012. Credit: NWS Dallas. Click on image for a larger version.

Those two events illustrate that crucial gaps in the nation’s severe weather warning and response system remain, and with tornado season in full swing, those gaps can carry deadly consequences.

Weather forecasters, emergency managers, and state and city officials are working hard to ensure that the high death toll from the 2011 tornado season — when 550 people lost their lives — is not repeated. Yet in the case of the airline industry and airports, the DFW incident demonstrates that little, if any, progress has been made to communicate tornado warnings to pilots.

Despite clear indications on weather radar of a powerful thunderstorm with a possible tornado heading toward the DFW airport, the issuance of a tornado warning, and a “tornado emergency” airport weather warning, airline pilots were still caught off guard on taxiways with full loads of passengers — exposed and vulnerable to a powerful tornado. The tornado emergency warning for DFW was issued 17 minutes in advance of the storm, according to the National Weather Service.

Luckily, the tornadic circulation passed over the airport without touching down (neighboring towns weren’t as fortunate), but golfball-sized hail damaged more than 100 planes, denting their aluminum skin, scaring passengers, and causing significant delays and cancellations.

According to news reports, pilots seemed unaware of the dangerous nature of the approaching storm. “In a matter of minutes, it went from being a thunderstorm to probably the worst weather event I’ve ever lived through,” American Airlines captain David Rintel told weather.com. He said he thought a “typical spring storm” was approaching when his aircraft pushed back from the gate, but knew the situation was very different when the storm hit. “It sounded like a whole little league team was going to work on the plane with bats.”

Fortunately, passengers inside the DFW terminals were warned in time to get to safety in designated tornado shelters and other interior portions of the buildings.

The DFW tornado was eerily reminiscent of the St. Louis event on April 22, 2011.

Despite a tornado warning being issued 34 minutes in advance, St. Louis airport authorities never notified passengers within the terminals of the approaching threat, a failure that the National Oceanic and Atmospheric Administration (NOAA) called attention to in a post-storm assessment. “Preparedness activities and action-plan procedures for the Lambert-St. Louis International Airport were minimal and ineffective for this event,” the report said. The airport authority has since taken steps to establish a plan and designate storm shelters throughout the terminals.

Path of two tornadoes (numbered) that touched down near DFW Airport (center) on April 3, 2012. Credit: NWS Dallas. Click on image for a larger version.

According to the NOAA assessment, even the controllers in the tower did not receive the tornado warning until two minutes before it struck, when their manager called to relay the warning after seeing it on television.

Pilots were not told of the approaching tornado either, as reported in a series for the Washington Post Capital Weather Gang blog last year, causing them to keep passengers on their aircraft, waiting for what they thought would be a garden-variety thunderstorm to pass.

Luckily, no one was killed during either event, but they call attention to the lack of procedures and jurisdictional confusion surrounding who is responsible for conveying tornado warnings to pilots while they are on the ground.

The main channel for passing tornado warnings to planes before they are handed off to air traffic control is via their individual airlines. Airline dispatchers can send the equivalent of text and email messages directly to the flight deck via a data link, and ramp controllers can reach them on the radio while they are on the tarmac, but it’s not clear whether any airline requires tornado warnings to be passed along that way. Furthermore, dispatchers typically handle multiple flights simultaneously and are not trained as meteorologists to look for tornado signatures on Doppler radar, such as the telltale “hook echo”, so they may not routinely look for such warnings.

Aircraft don’t come under the authority of the FAA until they emerge onto a taxiway or runway, and controllers do have access to weather warnings and local radar at most major airports. Here, too, there have been lapses, though.

Clearly, in both St. Louis and Dallas, word did not reach pilots at the gate or on airport taxiways. The weather.com story indicates that, as Rintel's plane waited with its engines turned off for the storm to pass, passengers received word of the tornado warning on their cell phones before the pilots had heard of it.

Other recent instances of planes being caught in severe storms, such as a massive hailstorm at Omaha, Nebraska's Eppley Airfield last year, offer more evidence that there are deficiencies in handling severe weather threats when planes are not airborne.

According to Mike Smith, a  Senior Vice President at AccuWeather Enterprise Solutions, a private weather forecasting firm in Wichita, Kan., the Dallas storm illustrates that progress has not been made to ensure that pilots receive timely tornado warnings in order to evacuate their passengers into the terminals.

“There are no procedures in place for what the pilot should do if in fact a tornado is approaching the taxiways,” he said. “The industry seems to want to do things after someone gets killed.”