Building on Jack's great analysis - as obs. heights in the NW US were substantially higher than modeled, one might ask how did the 12z GFS initialization account for that forecast error?

The new GFS analysis did nudge heights in the right direction, but still not enough. https://twitter.com/JackSillin/status/1357324668693344257
Thinking of data assimilation from a quick conceptual perspective - DA is a combination of a first guess (prior model forecast) & observations, which aren't necessarily truth & may contain biases/errors as well. Radiosondes are one of many types of data assimilated into a model.
Assimilating radiosondes & other obs (e.g., satellite) in the 12z GFS analysis did nudge the model analysis towards the radiosonde values, but not all the way, which may suggest a continuation of the NW trend in future runs.
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