10.6
A case study of a high altitude turbulence outbreak
Paul C. Fike, NOAA/NWS/NCEP/Aviation Weather Center, Kansas City, MO; and S. R. Silberberg
Encounters with high altitude turbulence pose a significant problem for aviation. Passengers can be injured or killed and aircraft can be damaged or pilots can lose control of aircraft due to encounters with moderate to severe or greater high altitude turbulence.
During 1-3 March 2001, nearly 100 reports of moderate to severe or greater high altitude turbulence occurred across the continental United States; with most of the reports between 1700 UTC March 1 2001 and 0300 UTC March 3 2001. A noteworthy feature associated with this turbulence outbreak was the large area affected. At one time, there were SIGMETS for severe turbulence in effect from the southern Rockies across the central Plains and Ohio Valley to the mid Atlantic coastal waters.
This paper will explore the causes of the severe high altitude turbulence outbreak and evaluates the performance of tools used by Aviation Weather Center meteorologists to forecast severe turbulence for this case. Observed and model soundings have identified multiple thin layers of strong vertical and horizontal wind shear. Infrared and water vapor satellite imagery signatures for severe turbulence such as transverse bands were examined. Preliminary results indicate transverse bands were present in the outbreak area and in other areas not affected by the outbreak. This illustrates the importance of examining the vertical and horizontal wind profiles and not relying on satellite signatures alone when forecasting moderate to severe or greater turbulence.
Zero and six hour fields of Ellrod Index, Turbulent Kinetic Energy, and Richardson number from the Eta, AVN and RUC2 strongly suggest a major high altitude turbulence outbreak. These forecast fields were compared with the severe turbulence reports for a qualitative evaluation of performance in this case. Preliminary results indicate that while these forecast fields captured the moderate to severe or greater turbulence reports, they overforecast the area affected by the turbulence outbreak.
Session 10, Turbulence and Wind Sheer
Thursday, 16 May 2002, 8:00 AM-11:45 AM
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