Another potential source of large error comes with extremely high amplitude ridges in the Gulf of Alaska and the forecast supergradient flow crossing to the right of the height contours on the east side of the upper ridge. Not digging upper energy far enough S, they are prone to miss closing off systems. The MRF ensemble members can often be helpful in determining when any model, particularly the operational MRF, is an outlier and straying too far from reasonable solutions offered by consensus of all the available models. A West Pacific typhoon, in the process of becoming extratropical as it enters the westerlies, can significantly alter run-to run continuity in all the models. Tends to progress shorter wavelength features too quickly.
Westerlies are often too far south.
The model tends to lower surface pressures too much and too far south and often implies synoptic-scale fronts too far south. This results from the forecasted baroclinic zone being too broad and low-level temperature gradients being too weak. Of the medium range models, it has the poorest performance forecasting polar vortices. Often is too flat with the upper and surface patterns over the western Pacific. This is a tropical interaction problem or applies directly to tropical cyclones.