Friday, July 6, 2012

OT detection utility: turbulence

On the morning of 120705 a small area of convection was slowly moving SE through lower MI and northern OH, and consistently was showing a number of overshooting top detections, particularly in the vicinity of Detroit Center. Overshooting tops (OTs) are turbulent in nature, both from the vertical and horizontal shear associated with the rapid growth of the updraft and from wave clouds which form when the updraft penetrates the Equilibrium Level (EL). While much of this activity is limited to the area in the direct vicinity of the convective core, the wave clouds can cause turbulence 25 miles or further from the OT.

In this case severe turbulence was reported just SW of Detroit Center  between 1030 and 1100 UTC by a number of large aircraft, including a 757, 753, and an A320, and while none of these jets flew within 30 miles of the OTs themselves, note the wave-like pattern of the clouds surrounding these tops. This is most likely the main cause of the turbulence reports in SE MI.

At the current moment the OT detection algorithm is only a 'yes/no' classification and to a forecaster the use of this type of detection is somewhat limited as the top is already notable on visible imagery. However, some work has been done on developing a turbulence probability for the area surrounding the OT. The potential for this probability tool is especially notable in this example, as knowing where the highest risk for turbulence around the OT would aid traffic flow managers in routing aircraft safely through convective areas.

120705 1045 UTC Overshooting Top (OT) detections and visible imagery

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2 comments:

  1. Kris BedkaJuly 6, 2012 at 1:32 PM

    great example of the turbulence associated with flight near overshooting top regions. From what I see in this image though, aren't these aircraft flying relatively low, i.e FL170 and 140, such that they wouldn't be flying within the gravity wave features depicted in the visible image? I'd imagine that the cloud tops would probably be above FL300. It's possible that the wave signature would penetrate below the anvil, but 15 kft of downward penetration would be extreme? Anyone have a cloud resolving model handy to simulate this storm? :->

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  2. AMTJuly 9, 2012 at 11:14 AM

    Yes, there were two reports of lower level turbulence in OH, but you'll notice that the severe marker just SW of Detroit Center didn't have a reference level. Severe turbulence was noted here by a number of different aircraft at a number of different levels and I believe the highest level reported was up near anvil level (~FL390 if I recall correctly). It would definitely be interesting though, to see how far a wave signature penetrates.

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