Yes. Today is the first day of Winter...Meteorological Winter that is. Believe it or not there are different time frames for seasons.
WHAT YOU NEED TO KNOW:
Meteorological seasons are different from astronomical seasons
This is done for more even seasonal meteorological comparisons
Meteorological seasons are counted by full months
The "official" beginnings or ends of seasons of which you are accustomed to hearing are called "astronomical seasons". The astronomical calendar is centered around the earth's rotation around the sun.
The earth's orbit around the sun, combined with our home planet's tilt, gives us our seasons.
The astronomical beginning of spring occurs when the sun is directly over the equator and is called the Vernal Equinox, which occurs in late March.
Summer officially begins with the Summer Solstice, which is when the sun is directly over the Tropic of Cancer.
The Autumnal Equinox marks the beginning of autumn, and that is when the sun is directly over the equator once again.
Finally, the Winter Solstice, when the sun is directly over the Tropic of Capricorn, marks the beginning of winter.
WHAT ARE THESE SEASONS' TIME FRAMES?
Meteorological spring is March, April, and May.
Meteorological summer is June, July, and August.
Meteorological fall is September, October, and November.
Meteorological winter is December, January, and February.
WHY IS THIS DONE?
These meteorological seasons were created for the purposes of meteorological and climatological forecasting and research. The length of the meteorological seasons is more consistent than the astronomical seasons (the dates of the equinoxes and solstices can vary by a few days each year).
Meteorological seasons also more closely follow our regular calendar. For these two reasons, this makes the use of the meteorological seasons easier for study and research, including calculating seasonal averages for temperatures, precipitation, and more.
CHANGES AROUND THE CORNER!
I don't think it's any kind of secret - I outlined exactly a month ago that I believe this Winter will feature ABOVE normal temps and BELOW normal snowfall... but more snow than last year. We may just get a shot of Winter weather EARLY in the season... as in the first part of December. There are several things that will come together that could lead to such an outcome.
One of the factors we look at when trying to determine what's going to happen long-range is what's occurring with the Madden Julian Oscillation (MJO). This shows us what thunderstorm activity is doing. There are 8 phases. When those squiggly lines go into 8, 1, 2 & 3, we can expect colder weather in our part of the country. Or, at least conditions become more FAVORABLE. Last year we spent a good chunk of time in 5 and 6 which are WARM phases.
So where are we at this moment in time with it? The models have it either in the "circle of death" or "null phase" OR bordering those warmer phases. The farther the lines are INTO the phases and AWAY from the center, the more amplified and bigger impact it has on the overall global pattern. Doesn't really appear to me that the MJO is going to have a huge impact on where we go over the next couple weeks. That can be good and bad but for now I think it will benefit us since it looks to stay out of the harsh warm phases.
UPPER AIR PATTERNS
The big indices we look at are the Pacific North American pattern (PNA) and North Atlantic Oscillation (NAO). If these aren't favorable...forgettaboutit. Through the course of November, they've pretty much been the opposite of what we need for colder air. That looks to flip around.
Here's the NAO:
It's doing exactly what we NEED it to do, which is go negative. I'd like to see it go DEEP negative, but anything below that neutral line will do for now. Here's what that looks like on a map:
A negative NAO puts high pressure over greenland and not only forces colder air down into the eastern part of the country, but it can "block" storms from being progressive. The storm tracks can be altered to bring wintry weather.
Here's the PNA:
Going positive. For the most part it was NEGATIVE during November. Here's what that looks like on a map:
High pressure (ridging) sets up in the west bringing warmer than average weather to that part of the country while cooler than average weather moves into the east.
These two indices working in tandem could produce for us. There's a narrow window though because I believe things warm up as we head into the new year. So it's a "now or nothin" mentality we have. We've got a couple different storm chances in the next 10 days. We shall see if any wintry weather can materialize from them!
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