Thursday, February 09, 2017

Brief Update For Weekend

The latest model forecasts are bouncing around wrt the weekend system and chances for rainfall here in eastern Pima County. The current synoptic pattern is very complex - the IR image above from 13 UTC this morning indicates two substantial vorticity centers within the broader trough off the West coast. One of these is a bit west of Portland, while the second is further west, along east side of mostly yellow cloud mass. The models forecast a very complicated evolution of these features that eventually results in a closed low digging southward into our region by Saturday night. However, current forecasts bring this low south over land, resulting in a more moisture-starved system for our region. It is not at all clear how the details will play out.

But, the GEFS members were considerably drier in their forecasts for QPF at TUS in last evening's 00 UTC forecast runs - below. There are no plume products available at this time from 06 UTC - probably due to the nasty storm impacting the Northeast this morning. However, the operational GFS (blue) was very dry at 00 UTC, and the ensemble members are drier and all over the place wrt to both timing and amounts.

For comparison, here are two WRF-GFS forecasts of precipitation through 11:00 am MST on Sunday morning. The above is from the 00 UTC runs at Atmo, while below is from the 06 UTC runs. very dry results from 00 UTC - driven by blue GFS forecast shown up in the plumes. The 06 UTC version is considerably wetter for Pima County (obviously reflecting that trend in the 06 UTC operational GFS).  Main point here is that models are jumping around, both up and down, and that it's much to soon to get a real handle on what Saturday night and Sunday may bring here in metro area.

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