Lately we've noticed some higher temperature forecasts from the NBM
along the benches (transitions between the mountains and valleys),
than in the valley floors. I was able to trace this back to the RTMA
and URMA analysis which is impacting the bias correction in the NBM.
This also seems to happen at some pixels along the boundary of the
Great Salt Lake lake shore as well. The issue is fairly ubiquitous at
these transition zones in elevation, and does not appear to be limited
to any specific observation site issues. The other odd thing is that I
actually can't explain how the RMTA and URMA are arriving at the final
analysis values. Using the KML files available to see how the obs are
impacting the RTMA analysis, the final analysis values for the
offending pixels in the KML file are actually reasonable values, but
they don't actually match what I'm seeing the gridded RTMA and URMA.
Furthermore, it appears the RTMA is too warm at these locations, but
the URMA is even warmer at these locations, like the error magnifies
between the RTMA and URMA. I've attached some examples are specific
points, but the issue is far more widespread than just these pixels.
The issue also shows up any day, and seem independent of how warm/cool
the day is, we just happened to notice this on the warmer days as this
has downstream impacts to the NBM and thus HeatRisk forecasts as well.
