AO heading for sub -5 on Feb 11th!
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Started by WxFollower - Feb. 9, 2021, 9:37 p.m.

 The AO is headed for sub -5 on Feb 11 per the image below. How significant is this?

- The last met. winter day (DJF) with sub -5 was way back on 12/18/2010! 

- Since 1950, there have been only 35 met. winter days out of 6,318 with a sub -5 AO, which is only ~1/2 % of all winter days. Due to the rarity of this, maybe that is why the models have been so volatile.

- Only 8 winters out of the last 70 have had at least a single day of sub -5 AO:

 2010-1 (12/18)

 2009-10 (12/20-5, 1/2-6, 2/6-7, 2/14)

 1984-5 (1/18-20)

 1977-8 (2/5-6)

 1976-7 (12/28-9, 1/11-17)

 1968-9 (2/13-6)

 1965-6 (1/28)

 1962-3 (1/21)

- What did the 11 months that contained these 35 days have in common? They were all very cold in the US as a whole, especially E US. You can see that here:

  - Out of these 35 days, only 11 of them were -5.6 or lower and they were during only 3 periods: 12/21 & 12/23 of 2009, 1/18-20/1985, and 1/12-7/1977.


By metmike - Feb. 9, 2021, 11:11 p.m.
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Pretty amazing  larry

heres the 3 month averages going back to 1950.

Monthly Mean Arctic Oscillation index

By metmike - Feb. 9, 2021, 11:13 p.m.
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                Arctic and North Atlantic Oscillation             

                           Started by metmike - Oct. 23, 2018, 8:10 p.m.     

By MarkB - Feb. 10, 2021, 2:25 a.m.
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I remember the cold of 1987. I burned 11 cords of wood that winter, trying to stay warm. Sleopt on the living room floor, in front of the wood heater. Temps reached -17. In KY.

By bear - Feb. 10, 2021, 2:13 p.m.
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here in the ol pueblo (tucson) today... we should have a high of 74, and tonight a low of 47 ...

partly cloudy, mostly calm.  beautiful day for walking the dog, and doing a few chores outside.  

should be about the same all week.  

hope you all have a very nice valentines day this weekend.  

By metmike - Feb. 10, 2021, 2:26 p.m.
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thats the way it usually works.

the spacing in between large scale features is such that the midwest and east often have the opposite wx as the west and swest.

By WxFollower - Feb. 11, 2021, 12:51 p.m.
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- The AO dipped to -5.31 today, which is the lowest since 1/4/2010!
- Only 3 out of 70 winters since 1950-1 have had a day with lower AO: 2009-10 (a very cold E US winter, coldest since 1977-8 in some cases), 1984-5 (during the great E US cold dump), and 1976-7 (during another major cold dump which lead to snow falling in S FL/Bahamas).
- The only 17 days with lower AO than 2/11/2021: 1/2-4/2010, 12/20-3/2009, 1/18-20/1985, and 1/11-17/1977.
- The Midwest/Plains/TX/Midsouth have plenty to show for it with historic cold.

By metmike - Feb. 12, 2021, 12:42 a.m.
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pretty amazing to see something this rare!

one wonders if its related to the arctic amplification from global warming.

However, this is not unprecented. 

for sure, the extremely coldest air masses coming from the arctic are usually not AS cold as they once were during the coldest times of year from 30+ years ago.

The planetary warming has been amplified by around 3 times in the arctic vs the mid latitudes. so the air coming from that location will not be quite as cold as it used to be in many cases.

moderating the coldest places in the coldest times of year, is a good thing in many cases. 

Warm Arctic, Cold Continents? It Sounds Counterintuitive, but Research Suggests it’s a Thing


Scientists suspect that rapid warming in the Arctic is causing more climate extremes farther south, including bouts of severe cold and snow in the Northeast.