Frontogenesis Contour Issue

[jsillin]

Hi all,
After some much-appreciated help from folks on here, I have been computing and plotting frontogenesis using model data. My code runs great and produces nice-looking plots most of the time, but I get weird contouring problems every once in a while. See the example output map:

Note that some parts of the frontogenesis contours just don't plot. The data underneath is good, some of the contours show up as expected, but some of the contour loops don't close for some reason I can't seem to figure out.

I make thousands of plots each day with dozens of other variables and several models. Frontogenesis is the only parameter I've ever run into this problem with, so I'm not sure it's a matplotlib issue. This problem happens regardless of which model I'm plotting (HRRR, NAM, GFS) and hasn't been resolved by applying a smoother (at least the Gaussian Filter from ndimage that I'm using at sigma=2,order=0).

Any ideas what might be causing this and what a potential fix might look like?

Here is the plotting code:

    h7_fgen = mpcalc.frontogenesis(t7.data,u7.data,v7.data,dx,dy)
    h7_fgen = h7_fgen*1000*100*3600*3 ##convert to units of K/100km/3hrs
    h7_fgen = ndimage.gaussian_filter(h7_fgen,sigma=2,order=0)

    fc = ax3.contour(x,y,h7_fgen,alpha=0.7,colors='fuchsia',levels=range(6,60,2),linewidths=3)

[kgoebber]

Can you check for NaNs in the computed frontogenesis? I don't know why you would be getting a NaN, but that is the only thing that pops to the top of mind.

Are you using data from a THREDDS server or a local data source?

[ktyle]

Oh, this is suddenly sounding familiar. I recall getting NaNs when calculating frontogenesis on locally-stored CFSR grids. Let me see if I can resurrect that.