Wednesday, December 28, 2016
New Year's Weekend - Considerable Uncertainty
The meandering, 500 mb closed-low west of Baja is providing low-latitude interest, as a broad plume of tropical moisture spreads northward, centered about 115 degrees W. The IR image above is from 1130 UTC this morning, and the MIMIC blended PW analysis below is from 1100 UTC. Values of PW of an inch or more have reached northward up the GoC to about 30 degrees N. A key forecast issue for the next few days will be how far into the Southwest this moisture plume might intrude. Currently, model forecasts are very mixed.
The GEFS plumes illustrate the high uncertainty at this time. The 06 UTC plumes for QPF at TUS (above) have a variety of forecasts (amounts and timing) depending upon the member model run. The operational version of the GFS is a serious DRY outlier wrt the ensembles, and I have not paid much attention to the WRF forecasts, which are driven by this very dry model forecast. The operational ECMWF appears considerably more wet.
The plumes for PW (below) spread all over the place beginning on the 1st of the New Year, and this is part of the reason that the various ensemble members go different directions - some versions bring the higher moisture into our area and others don't. Another wait and see what the weekend actually brings situation.
The models do indicate that the first week of 2017 will be quite cold for a large part of the continental U.S.
Posted by Bob Maddox at 6:15 AM