Tuesday, September 29, 2015

Update Re: ECMWF vs GFS

Comment from Mike Leuthold this morning - The 0z WRF GFS has some interesting weather for Arizona by Sunday with as much as 6 inches of rain along the border by Tuesday afternoon.

Forecast above shows the model's forecast of accumulated rainfall through 5:00 pm MST on Tuesday afternoon, October 6th.

Since yesterday the ECMWF forecast for the 500 mb pattern over western U.S. has remained fairly stable, while the GFS 500 mb forecasts have undergone very large dForecast/dTime - above and below are the 144-h operational-member forecasts from 00 UTC last evening valid at 5:00 pm MST Sunday afternoon. Compare the GFS forecast (below) with the earlier one shown in previous post. There are still substantial differences in the forecast strength of the 500 mb systems - both over the East and the West. The closed low forecast over California is 150 to 200 m deeper in the ECMWF forecast, while the GFS is stronger wrt the East Coast short-wave.

Both features are interacting with tropical disturbances, and the attention in the East revolves around how the short-waves in the westerlies will interact with TS Joaquin. The model differences are very large, with the GFS bringing remnants of Joaquin ashore over the Northeast, while the ECMWF scoots Joaquin rapidly off into the open Atlantic. 

These systems will possibly be heavy rain producers both in the Southwest and the Northeast - the GFS forecast shown below is for 60-h precipitation ending at 5:00 pm MST on Monday afternoon. Lots to watch through the coming weekend, and 144-h is still a long way away.

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