[1] Note that the CONVECT program scales the hodograph plots so that the result is more or less the same size, regardless of the magnitude of the shears. This can be deceiving, as a hodograph with little or no shear may be scaled to look like a hodograph with large shear. Thus, users of this program are cautioned to examine the plots carefully. It would be better to have the coordinates remain the same for all plots, making the difference between a low-shear case and a high-shear case more apparent visually.

[2] On Figure 2, the CONVECT program has drawn a line from the origin to the surface (labelled "0") which, strictly speaking, is not part of the plot.

[3] This is true for the northern hemisphere, of course. In the southern hemisphere, one should substitute ``right'' for ``left'' and everything else remains the same.

[4] Strictly speaking, of course, such an atmosphere is baroclinic (nonbarotropic), but it is a special case, clearly.

[5] If the cyclone is advancing at the same rate at every level in the troposphere, is it likely to be developing? I leave that for the reader to answer. If it does advance at the same rate throughout the troposphere, it will not increase the low-level flow in such a way as to create a low-level jet -- rather, such a system would show increasing flow at all levels.

[6] Note that in the case of unidirectional flow with shear, the flow is equivalent barotropic (recall the discussion in Sec. 3a).

[7] These unit vectors can also be thought of as those associated with the so-called natural coordinate system (see e.g., Hess 1959, pp. 177 ff.)

[8] Sometimes this local value is referred to as the helicity density . [footnote not in original text]

[9] Note that by using Eqn. 4 and a form of Eqn. 1 appropriate to a p -coordinate system, it can be shown that H (ground-relative) is proportional to the average thermal advection in the layer. [footnote not in original text]