Thursday, December 29, 2016

Weather Potpourri For New Year's Weekend

More interesting weather going on than I can show with my late start this morning.

High pressure of about 1038 mb over eastern New Mexico today will bring east winds to our part of Arizona later today. The WRF-GFS at 06 UTC forecasts a period of gusty winds of 25 to 35 mph at the airport this afternoon. The issue of how the winds will play out depends upon both the easterly pressure gradient and the heavy cloud cover - the two are essentially fighting each other. Forecast soundings indicate a fairly shallow layer of strong winds that would affect parts of the metro area. Up at the Mt. Hopkins RAWS site, the the easterly push may be just deep enough to bring a marginal wind event of say around 45 mph later today.

On to the precipitation events. The 06 UTC GEFS plumes have become much more consistent since yesterday morning (QPF plumes for TUS at the top). The models in the ensemble are consistent now in time - light sprinkle showers today; then tomorrow night the models forecast 100 % chance for measurable rain at the airport; followed by a more significant 100 % event from late night on New Year's Eve through midday on the 1st of January. The operational GFS is now very close to the ensemble mean, and thus Atmo's WRF-GFS forecasts from 06 UTC are of much interest.

Currently the NWS seems to have covered all this with a broad brush, as per the current grid forecast for the airport below, with max POPs of only 50% for three different periods. However, if the forecasts from Atmo come close to verifying, then we are in store for a fairly significant precipitation event over the long Holiday weekend.

Here are two composite radar forecasts from the 06 UTC WRF-GFS - above is valid at 01:00 am MST on the 31st and below is valid at 06:00 am on January 1st.

While here are two forecasts for total precipitation from the model run last night. Above is valid through 05:00 am on December 31st, while below is valid through 11:00 am on New Year's Day. This would certainly be an interesting end of the year, if the model forecasts are close to reality. Bottom panel is forecast surface plot for 07:00 am on News Year's Day - a wet and very chilly start for next year.

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