Skew-T adiabats and mixing lines do not plot correctly if drawn before range is set

[jrleeman]

If user sets the axis limits before drawing the special lines, the lines are drawn far below the normal plotting range and would not appear on the plot. Example:

This works:

# Create a new figure. The dimensions here give a good aspect ratio
fig = plt.figure(figsize=(9, 9))
skew = SkewT(fig)

# Plot the data using normal plotting functions, in this case using
# log scaling in Y, as dictated by the typical meteorological plot
skew.plot(p, T, 'r', linewidth=2)
skew.plot(p, Td, 'g', linewidth=2)
skew.plot_barbs(p, u, v)

# Set axis limits
skew.ax.set_ylim(1000, 100)
skew.ax.set_xlim(-40, 60)

# Calculate full parcel profile and add to plot as black line
prof = parcel_profile(p, T[0], Td[0]).to('degC')
skew.plot(p, prof, 'k', linewidth=1)

# Add the relevant special lines
skew.plot_dry_adiabats()
skew.plot_moist_adiabats()
skew.plot_mixing_lines()

This does not:

# Create a new figure. The dimensions here give a good aspect ratio
fig = plt.figure(figsize=(9, 9))
skew = SkewT(fig)

# Plot the data using normal plotting functions, in this case using
# log scaling in Y, as dictated by the typical meteorological plot
skew.plot(p, T, 'r', linewidth=2)
skew.plot(p, Td, 'g', linewidth=2)
skew.plot_barbs(p, u, v)

# Calculate full parcel profile and add to plot as black line
prof = parcel_profile(p, T[0], Td[0]).to('degC')
skew.plot(p, prof, 'k', linewidth=1)

# Add the relevant special lines
skew.plot_dry_adiabats()
skew.plot_moist_adiabats()
skew.plot_mixing_lines()

# Set axis limits
skew.ax.set_ylim(1000, 100)
skew.ax.set_xlim(-40, 60)