Friday, December 15, 2017

Finally - A Weather Event

An interesting weather event shaping up for the weekend: wind, then some precipitation, then cooler into week heading up to Christmas. The GEFS QPF plumes, above from 00 UTC last evening, have almost all members forecasting some rainfall at TUS on Saturday night and Sunday. The big spread is in the amounts forecast, which range from a Trace to almost 8/10 of an inch. Ensemble average keeps amounts fairly light, yet again.

Once again the operational GFS appears to have had the trends forecast better than the ECMWF, which continues to show considerable variability between 12 and 00 UTC intialized forecasts.

The operational GFS forecast for 500 mb is shown above - from 00 UTC last evening and valid at 00 UTC on 18 Dec (Sunday afternoon at 5:00 pm MST). The model's precipitation forecast for period ending at same time is below.

Shown here are two ECMWF 500 mb forecasts. Above is forecast from yesterday morning at 12 UTC (valid at 12 UTC Sunday) - note that it trended into sync with the GFS. The 00 UTC ECMWF
(below and valid at same time as GFS forecast above) now shows that model to be slower and deeper than the GFS. Strange behaviors in the global models at very short forecast periods,

The big uncertainty remains as to how much moisture the digging, mostly overland, short wave can tap. The  MIMIC TPW analysis below is valid at 14 UTC this morning with higher PW amounts pushed way to our south - so moisture availability is likely to be limited, and this now looks to be the key factor to watch as the weekend event unfolds.

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