The National Weather Service’s Aviation Weather Center (AWC) has issued a SIGMET alerting pilots and passengers of the threat of severe turbulence in the airspace over portions of Colorado and New Mexico, impacting high-traffic routes going to United Airlines’ hub in Denver, Colorado and Delta Airline’s hub in Salt Lake City, Utah. Other transcontinental aircraft may encounter rough air, although they could fly around or above it. Specifically, SIGMET PAPA 10 has been issued through at least 0255Z this evening.
According to the National Weather Service, there is occasional severe turbulence in the SIGMET area between the surface and 20,000 feet, altitudes typically used by commercial aircraft flying through this region especially as they descend into or ascend out of Denver International Airport. The National Weather Service says this severe turbulence is being created by strong low level winds, strong up and down drafts, and low level wind shear. Wind shear is a difference in wind speed and/or direction over a very short distance in the atmosphere. Airline pilots generally regard significant wind shear to be a horizontal change in airspeed of 30 knots (15 m/s or 34 mph) for light aircraft and 45 knots (23 m/s or 51 mph) for traditional airliners flying at flight altitude.
Flying through turbulence can be dangerous, with injuries encounter on two U.S. airline flights this week.
On Monday, a United Airlines 767 jet encountered severe turbulence on its flight to Houston, Texas. Due to that encounter with rough air, 3 crew members and 2 passengers had to be rushed to the hospital for care upon landing.
On Sunday, Hawaiian Airlines Flight 35 flew through severe turbulence before landing at Honolulu International Airport after originating in Phoenix, Arizona. A Mass Casualty Emergency Event was declared, with dozens of passengers needing care for injuries sustained in the violent ride. Officials with Honolulu Emergency Medical Services and American Medical Response say the flight encountered the extreme turbulence about 30 minutes prior to landing; they treated 36 patients at the airport. 20 patients, ranging from a 14-month old toddler to older adults, were transported to hospitals near the airport, some with serious injuries.
Known as a SIGMET, short for Significant Meteorological Information, the severe weather advisory issued by the AWC contains weather-related information concerning the safety of all aircraft passing through a specific zone. Sometimes AIRMETs are issued too; an AIRMET consists of turbulence, visibility, and icing-related warnings that are less severe than those in a SIGMET.