Monday, September 28, 2015

ECMWF vs GFS For Next Weekend

While the coming week will be dry and hot, the weekend is interesting in that there is a very large difference between the operational, 168-h forecasts from the ECMWF vs the GFS models. All forecasts here are for 500 mb at 168-h (valid at 5:00 pm MST on October 4th) from the 00 UTC forecasts last evening.

The ECMWF forecast (above) indicates a strong, closed low over California, while the GFS forecasts a significant, bent-back ridge extending from Baja north and northwestward across Alaska. The ECMWF also forecasts a low-latitude, short-wave trough to our south, while GFS anticyclone has any such features blocked and kept at low latitudes. The weather associated with the forecasts would be quite different, of course.

The GFS spaghetti plot of its ensemble forecasts (bottom) indicates low predictability out at 7 days, shown by the mess of "spaghetti" that extends from the northeast Pacific eastward all the way across Europe. I don't have access to similar charts from the ECMWF, although they are available to some. Will keep an eye on how these forecasts evolve during the week.

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