[gradsusr] Question about why the wind vectors barbs not showing up for the 0-6 KM Shear difference

[Jeff Duda]

I suggest you have a look through this page (
http://mathworld.wolfram.com/VectorAddition.html) and the related page
linked under "see also" called "vector difference".  You can add/subtract
two vectors by adding/subtracting the corresponding *components* (i.e., the
u and v components), and making a vector of the resulting sum/difference.
 What you seem to be stuck on is taking the difference of the *magnitude* of
the vectors rather than the difference of the components.

I'll use this example to help illustrate this.  Suppose you had a westerly
wind at 500 mb of 50 kts, and an easterly wind of 50 kts at the surface
(unlikely except for possibly within a severe thunderstorm, but just bear
with me).  There is no difference in the wind speed between 500 mb and the
sfc, but there is a difference in the direction.  Clearly there is shear,
but only if you look at the component form of the wind.  The u- and
v-components of the 500 mb wind in this example are u = 50, v = 0 (kts),
whereas at the surface, the components are u = -50, v = 0 (kts).
 Therefore, the shear is given by (u500-usfc)*i* + (v500-vsfc)*j* = (50 -
-50)*i* + (0-0)*j* = 100*i* + 0*j*.  The shear vector is straight out of
the west here.  The magnitude is given by sqrt(ushear^2 + vshear^2), which
is sqrt(100^2 + 0^2) = 100 kts of shear.

Jeff
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://gradsusr.org/pipermail/gradsusr/attachments/20130901/03a9ad31/attachment-0003.html