"C Kingsbury" wrote in message
hlink.net...
Roger,

I find the conditions you describe (high wind velocity with low
turbulence)
more commonly in the Winter months up here in New England, which would
seem
to comport with your suspicions about atmospheric stability. Do you still
have the winds and temperatures from that day? You could look at the lapse
rate to see how it compared to the standard rate.

-cwk.



Stability is a great part of the equation, and there is one other.

The High in the northeast is well established, to high levels. With
Anticyclonic flow all the way up through 500 mb (18,000 ft) that airmass is
generally sinking. Hence the clear skies, not even any CU, even though the
air is relatively cold. Warm ground would help destabilize it, but the low
sun-angle isn't doing very much.

The horizontal gradient of the upper-air temperatures is fairly flat at all
levels... At 5000 feet, it is only 6 degrees Celsius difference between
Quebec and Northern Florida. A flat horizontal temperature gradient, actual
leads to little vertical wind shear, and to some degree, to little
*horizontal* wind shear.... So the only shear you tend to get is just the
boundary-layer shear.

So we have no vertical currents (stable), and little horizontal and vertical
shear, (except for some vertical shear in the boundary layer).

Now I am no aerodynamic expert, but it would seem that vertical wind shear
(alone) is the least problematic for aircraft. With the horizontal wind
changes quickly, the only things that happen could be yaw, and a possible
change in overall lift, but there is little or no roll...the relative wind
changes more or less uniformly for the whole wing.

When we have those unstable summer CU days, and a similar sort of boundary
layer vertical shear, the increased winds reach portions of the wings at
different times due to the vertical currents helping to bring them down or
retard them, (as well as adding their own differential vertical
components...).... so the potential for roll is greatly increased. If you
add horizontal shear, you get yaw problems as well.

To summarize:
A stable airmass with no horizontal shear, in spite of the boundary-layer
vertical shear, is probably the cause of your non-problems. :-)
Horizontal wind shear (such as vicinity of a front), and/or stronger sun
producing convective currents, would have probably upset that significantly.