Thursday, December 14, 2017

Model Uncertainty For Sunday

Global models have considerable differences for the Southwest by Sunday afternoon - above is GFS operational 500 mb forecast valid at 5:00 pm MST Sunday, while below is same forecast from operational ECMWF. The GFS digs the 500 mb shortwave as a single feature that closes off nearly overhead with much lower heights and temperatures. However, the ECMWF splits the short wave into two pieces, with one closing off over Baja and the other crossing Colorado. Both models bring a front through Arizona, but the GFS would support at least a chance for rain/snow showers in our part of state.

The GEFS spaghetti plot for 500 mb valid at same time as other forecasts indicates maximum uncertainty in the ensemble members nearly overhead - thus, something to watch and also another head-to-head between operational versions of the two global models.

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