Sunday, December 6, 2020

Meteorological Winter is Here!

During a cold walk last week I saw this leafless sycamore tree among colorful bushes. I think it looks like a winter tree wearing an autumn skirt. And that might be a nice metaphor for the season. Depending on which system you use, it's either winter now or the end of autumn. Click to enlarge.

As meteorologists reckon, winter begins on December 1st and extends through January and February, the three coldest months of the year in the northern hemisphere. The system is based on the calendar and the temperature and begins on the same day every year. That's important for comparing weather data.

Astronomical winter, on the other hand, is based on the Earth's rotation and the tilt of its axis. Astronomical winter arrives with the shortest day of the year around December 22, but possibly a day or so sooner or later. This year, it will be on the 21st.

December 1st or three weeks later? We're between these winters right now. Regardless of which you prefer the sun is low in the sky these days, it's dark out early, and it's cold out there.

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