1. Aviation and Downbursts Douglas Cain Jamie Gudmestad Aviation Program NWS Midland

5. Things you should know about Downbursts Are caused by shower or thunderstorm outflow Strong out-rush of damaging winds Can be very hazardous to aircraft

6. Weather related Aviation Crashes & Deaths in 2004 by Type of Operation Crashes Deaths Crashes Deaths Scheduled Airlines 1 13 Scheduled Airlines 1 13 Air Taxi, Commuter 12 29 Air Taxi, Commuter 12 29 General Aviation 98 198 General Aviation 98 198 Totals 111 240 Totals 111 240

7. Downburst!

8. Downbursts most dangerous to aviation On take off On take off On landing On landing

9. During take-offs the pilot experiences a headwind and increased aircraft performance followed by a short period of decreased headwind a downdraft and finally a strong tailwind

10. During landings the airplane begins the descent flying into a strong headwind a downdraft and finally a strong tailwind represents the extreme situation just prior to impact

11. Research by NCAR and collaborators in the 1980s uncovered the deadly one-two punch of microbursts: aircraft level off when they encounter headwinds, then find themselves pushed to the ground by intense downdrafts and tailwinds.

14. Downbursts can be Divided into Two Main Types MACROBURST: A large downburst with its outburst winds extending greater than 2.5 miles horizontal dimension. Damaging winds, lasting 5 to 30 minutes, could be as high as 134 mph. MICROBURST: A small downburst with its outburst, damaging winds extending 2.5 miles or less. In spite of its small horizontal scale, an intense microburst could induce damaging winds as high as 168 mph.

15. Wisconsin on the 4th of July, 1977, with winds that were estimated to exceed 115 mph, and completely flattening thousands of acres of forest Macroburst Microburst

16. DownburstsMicroburst Dry Microburst Damaging winds less than 2.5 miles in diameter Accompanied by little or no rainfall Wet Microburst Damaging winds less than 2.5 miles in diameter Accompanied by very heavy rainfall and perhaps hail

17. August 1, 1983 the strongest microburst recorded at an airport was observed at Andrews Air Force Base in Washington DC. The wind speeds may have exceeded 150 mph in this microburst. The peak gust was recorded at 211 PM – 7 minutes after Air Force One, with the President on board, landed on the same runway.

18. Dry Microburst Sounding

23. Wet Microburst

25. Signs a Downburst may be Occurring Thunderstorm Thunderstorm Rainshower Rainshower Blowing dust Blowing dust Virga Virga Rainfoot Rainfoot

26. Dry vs. Wet Microburst Characteristics CharacteristicDry MicroburstWet Mircoburst Location of Highest Probability Precipitation Cloud Bases Features below Cloud Base Primary Catalyst Environment below Cloud Base Surface Outflow Pattern West Little or none As high as 500 mb Virga Evaporative cooling Deep dry layer/low relative humidity/dry adiabatic lapse rate Omni-directional Southeast Moderate or heavy Usually below 850 mb Shafts of strong precipitation reaching the ground Downward transport of higher momentum/precipitation loading Shallow dry layer/high relative humidity/moist adiabatic lapse rate Gusts of the direction of the mid- level wind

27. The following are some fatal crashes that have been attributed to windshear/ microbursts in the vicinity of airports: The following are some fatal crashes that have been attributed to windshear/ microbursts in the vicinity of airports: Eastern Airlines Flight 66 Eastern Airlines Flight 66 Eastern Airlines Flight 66 Eastern Airlines Flight 66 Pan Am Flight 759 Pan Am Flight 759 Pan Am Flight 759 Pan Am Flight 759 Delta Airlines Flight 191 Delta Airlines Flight 191 Delta Airlines Flight 191 Delta Airlines Flight 191 USAir Flight 1016 USAir Flight 1016 USAir Flight 1016 USAir Flight 1016

28. Eastern Air Lines 66 June 24, 1975 New York – Kennedy Airport 112 killed 12 injured Crashed while landing Boeing 727

29. Pan Am 759 July 9, 1982 New Orleans Airport 145 passenger/crew killed 8 on ground killed Crashed after takeoff Boeing 727

30. Flight trajectory (red line), winds (green arrows), and indicated airspeed of PAA 759

31. Delta 191 August 2, 1985 Dallas-Fort Worth Airport Crashed on landing 8 of 11 crew members and 128 of the 152 passengers killed, 1 person on ground killed Lockheed L-1011

33. USAir 1016 July 2, 1994 Charlotte/Douglas Airport Crashed on landing 37 killed 25 injured McDonnell Douglas DC-9

34. Is the Situation Getting Better or Worse?

35. Fatalities Associated with U.S. Aviation Wind Shear Accidents

36. The Terminal Doppler Weather Radar (TDWR) is now deployed at 44 major airports. The TDWR mission is to provide wind shear detection services to air traffic controllers and supervisors

37. In the 1980s, research conducted at the National Center for Atmospheric Research (NCAR), indicated that microburst windshear was very dangerous to aircraft below 1000 ft. Several major accidents during the 1980s also implicated windshear as a factor. Low Level Windshear Alert System (LLWAS)

38. Microburst “Season & Time” Microburst “Season & Time” The four best known downburst aviation disasters in the U.S. happened in the summer. The four best known downburst aviation disasters in the U.S. happened in the summer. (1 in June, 2 in July, 1 in August) (1 in June, 2 in July, 1 in August) All four happened in the late afternoon or early evening (from 4:05 to 7:43 local time) All four happened in the late afternoon or early evening (from 4:05 to 7:43 local time)

39. Still not There The threat of wind shear has been reduced but not eliminated. It was mentioned in an average of 25 National Transportation Safety Board accident and incident reports a year from 1983 through 2001. But the vast majority of cases were nonfatal and mostly involved general aviation. The threat of wind shear has been reduced but not eliminated. It was mentioned in an average of 25 National Transportation Safety Board accident and incident reports a year from 1983 through 2001. But the vast majority of cases were nonfatal and mostly involved general aviation.

40. So What Days have High So What Days have High Likelihood of Downbursts? Likelihood of Downbursts?

46. This is a morning sounding, what kind of microburst would you expect in the afternoon?

47. The End!

48. Aviation and Downbursts Douglas Cain Jamie Gudmestad Aviation Program NWS Midland