[Qgis-user] Issue with "Mesh Calculator" with a GRIB file

[Eric Compas]

All,

I'm experimenting with the mesh viewing and analysis tools in QGIS (3.12.3)
using both the Crayfish and QGribDownloader plugins. All's going very well,
and for the most part, the tools are relatively easy to use.

While I've gotten several "Mesh calculator" expressions to work correctly
with a GRIB file (downloaded using the QGribDownloader plugin), I'm running
into an error with any expression using precipitation group, e.g.:

("Temperature [C]" > 10) and ("03 hr Total precipitation [kg/(m^2)]" < 2)


This expression yields an error "Mesh calculator: Invalid or incompatible
datasets used." I've tried several permutations and start/end ranges. All
without luck.

Investigating further, it seems like the number of time "slices" in the
precipitation group isn't the same as in the temperature group and may not
be handled correctly in QGIS (??). In the temperature group layer
properties, the time slider and metadata times are always the same
(synchronized).  For the precipitation group, the time slider and metadata
in the layer properties aren't in sync:

[image: 2021-02-06_10-34-02b.gif]
I suspect that the precipitation group has fewer time "slices" that may not
be handled correctly and hence the error in the "Mesh Calculator" tool.

Is this a user error or some issue with how the mesh tools handle groups
with differing number of time "slices?"

I'd appreciate any help.

Thanks,

Eric
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