Contouring bug on lcc projection

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This same issue is occurring for all data types. Quite often, though not always, one of any of the contoured data will spike sharply downward away from the rest of the contour (seen below in the yellow data). This happens quite often in the middle of the domain.
I doubt this is a problem with the data themselves or my analysis since this error makes the contour line cross other contour lines of the same data. If there were just an anomaly at the bottom of the domain, I would expect there to just be a gradient with the contouring toward it. This makes me think that the problem is all in the plotting.


Here's the plotting portion of my code.
`
#Plotting
fig = figure()
map = Basemap(llcrnrlon=-120.,llcrnrlat=20.,urcrnrlon=-50.,urcrnrlat=50.,\
rsphere=(6378137.00,6356752.3142),\
resolution='l',projection='lcc',\
lat_0=40.,lon_0=-98.,\
lat_1=30.,lat_2=60.)

#Draw geographical boundaries
map.drawcoastlines(color='red',linewidth=0.75)
map.drawstates(color='red',linewidth=0.75)
map.drawcountries(color='red',linewidth=0.75)
map.fillcontinents(color='black',lake_color='black')
map.drawmapboundary(fill_color='black')

#Create X-Y plane for contouring and filling on map
X,Y = map(asarray(longitude_grid), asarray(latitude_grid))

#1st Variable#
#------------#

levels = linspace(700., 1200., 126) #4 mb levels for SLP
cs = map.contour(X,Y,var,2,colors='c',linewidths=1.,levels=levels)
clabel(cs, fmt="%1.0f", fontsize=8, inline=1)

#2nd Variable#
#------------#

levels = linspace(0.,12000.,241) #50 m levels for thickness/height
cs = map.contour(X,Y,contr,2,colors='y',linewidths=0.75,levels=levels)
clabel(cs, fmt="%1.0f", fontsize=8, inline=1)

#Snow Contour#
#------------#

cs = map.contour(X,Y,snow,2,colors='w',linewidths=2.,levels=[0.,1.])


title('%s SLP [Blu] and 800-500 mb Height [Ylo] over Snow Line [Wht]' % times[i])

savefig('temp_plot%03d.jpg' % i)
`

Non è indicato alcun file o test del repository. Inizia riproducendo la Basemap lcc projection e le chiamate a contour mostrate nel report con gli stessi input longitude_grid, latitude_grid, var, contr e snow; il lavoro è completato quando avrai determinato perché le linee di contorno presentano picchi o si incrociano in modo imprevisto e confermato che il comportamento di plotting corretto non mostra più questi artefatti.

Scritto dal modello di indicizzazione a partire dal testo della issue.