Saturday, December 30, 2017

Extreme Gradients In Morning Obs

Temperatures yesterday were quite something - low here at house was again 32 F but high at airport reached 82 F, so a diurnal swing of around 50 F for parts of the metro area.

Very large gradients over U.S. and Canada this morning, on next to last day of the year, as illustrated by the 12 UTC observations this morning. Above is the 850 mb plot. Tucson comes in as warmest site in country at 850 mb with +18 C. Due north of us, Great Falls and Glasgow, Montana, reported 
- 26 C (44 C colder than here).

Below shows the plot of 12 UTC 500 mb observations, indicating an anticyclone nearly overhead, with heights of 5850 m here and at San Diego. But south of Hudson's Bay, the cold vortex has heights below 5100 m - again an extreme difference. Good to be in Tucson this morning and not the Northeast.

The WRF forecasts from ATMO at 06 UTC last night indicate the arctic air battles with our mild desert air masses will remain over in eastern new Mexico (above WRF-GFS temperature forecast valid at 12 UTC on January 1st, 2018).

The NWS has put a nice (slightly preliminary) summary of the past year up on their website (only partly shown below) - definitely another year with record-breaking warmth. Entire summary is at:

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