Monday, February 21, 2011

ECMWF vs GFS Forecasts For Saturday February 27th

The operational member forecasts for 500 mb (valid at 144 hours from last evening or 5 pm Saturday February 27th) are shown above for ECMWF (top) and GFS (middle). There is quite a bit of difference between the two forecasts. Both forecasts have cold heights (lower than 534 dm) over the western US but the ECMWF system is impacting the Southwest, while the GFS system is impacting the Northwest. Note that ECMWF forecast 500 mb heights are MORE than 300 m lower than those forecast by GFS near San Diego. The ECMWF has been doing much better than the GFS last several winters (my subjective feel is that at longer ranges for the western US it is more accurate for significant events than the GFS 8 or 9 times out of 10). So, something to watch as the week progresses.
The bottom figure is the GFS spaghetti plots and ensenble average for 500 mb forecasts valid at the same time. In this situation the GFS operational member seems to be a significant outlier over western North America and the eastern Pacific, with many of the ensemble members having a forecast considerably more similar to that of the ECMWF (see the right panel).

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