Tuesday, December 16, 2014

Very-Long Range Model Forecasts For Christmas

The short-term forecasts have considerable fluidity as the model forecasts are a bit volatile. So, I thought I'd look all the way out to Christmas Day, just out of curiosity. By 240 hours out, the GFS ensemble spaghetti plots do indeed look like a bowl of the same.



So here goes. Above are the ECMWF 500 mb and surface forecasts valid at 5 pm MST on Christmas Day. Below are the same two forecasts from the GFS. Both are from the operational versions of the models. The ECMWF is shown "on the top" for obvious reasons.

The ECMWF forecasts the most significant weather action to be over the West with a strong cold front crossing the Southwest, a strong low pressure system over Colorado, and nasty upslope snow from eastern Colorado north to Montana.

The GFS patterns are generally similar but considerably damped. The model forecasts an east-west cold front across the U.S., no significant low pressure systems in the interior, and scattered areas of light snow across the northern half of country. The small area of heavier snow forecast southwest of Chicago seems to be right where the ECMWF forecasts the greatest 500 mb height rises that would likely be accompanied by considerable downward motion. 

In eight to ten days, or so, we'll know how these forecasts actually played out. Cheers.



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