Friday, January 16, 2015

New GFS Products and Comments from Jeff Spicoli

As discussed in an earlier post (see, the GFS underwent a substantial upgrade on Wednesday of this week, including an increase in resolution to an effective grid spacing of about 13 km, very similar to the NAM.

In addition, for the first time, NCEP is kindly providing high-resolution vertical profiles and time series from the GFS for Alta (in what is known as BUFR format).

With help from Trevor Alcott, we've upgraded several of our products to take advantage of these improvements.  For example, the Little Cottonwood guidance tables, GFS time-height sections for Alta, and GFS meteograms for Alta at are now based on the high-resolution BUFR output.

If you have been adjusting the old GFS precipitation forecasts to estimate precipitation at Alta (or other locations), you are probably going to need to tweak your approach some.  At least at Alta and other mountain locations, you're probably going to see more precipitation generated by the GFS than you used to.   

Just for kicks, here's what the GFS is generating for Alta over the next week for snow-water equivalent.  A few dribs and drabs today and tonight, and then two small events on Sunday Night/Monday morning  and then Thursday night/Friday morning.  I suspect the old GFS would have produced less total precipitation due to its inferior resolution.  

I'm hoping to eventually upgrade the GFS horizontal maps on to something based on higher resolution output grids.  Unfortunately, NCEP is not providing output grids with anything near the full resolution of the new GFS, so while I can do better than we have now, we're still going to be looking at the model output at roughly half the full resolution of the GFS.  What a bummer!  To paraphrase Jeff Spicoli, "we upgraded the GFS 'cause it was bogus; so if we don't get some high-res output grids - pronto - we'll just be bogus too!"

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