Patterns Have Become Most Extreme Before Changing

[bluewave]

Since we saw the big pattern change in the arctic last winter, the patterns have really maxed out before changing.

12-15-10 to 1-15-11 was followed by a dramatic change from 1-15-11 to 2-15-11.

The strongly negative AO was followed by a positive AO with peaked back in April.

The pattern shifted to more blocking as we headed into May and June.

More recently the EPO made a big rise during August and ran all the way through the fall with record low 500 mb heights reported over Alaska this week.

Now a more negative to neutral looking EPO pattern is showing up in the forecasts.

This fall has featured a +AO pattern which has been very consistent. The big question is if the long range GFS is onto something showing the AO

reaching a point where it looks to be reaching a maximum for this cycle going back to the summer. If the pattern holds, then AO with become even

more positive as we head into December. This might be setting the stage for an eventual change to more neutral to negative later on. It's all a

bit speculative at this point so it will just be something interesting to watch for as we go into the winter.

Will the +AO peak before a pattern change?

[winterymix]

Good read, meshes well with Wes's analysis.

Maybe we can bet a good second half of February into Early March in the East.

[bluewave]

Good read, meshes well with Wes's analysis.

Maybe we can bet a good second half of February into Early March in the East.

Yeah,the last time we saw +3 AO readings was last April when the positive AO peaked before changing.

ftp://ftp.cpc.ncep.n...1.current.ascii

I guess the question is how long will a a pattern change take now for a +AO to a neutral or even negative state

as the pattern has been going since the beginning of September.

Long range GFS resembles the last April peak.

[HM]

The last +AO period in the spring occurred during the last active phase of the sun:

While the EPO / PNA will continue to respond to intranseasonal activity, I wouldn't expect the AO to drop considerably until the sun calms down. Notice in the last few days, we've had elevated proton levels (time sensitive; period of interest 11/26-28 2011):

http://www.solarham.com/proton.htm

This is an agent of ozone destruction and PV intensification for sure.

[am19psu]

This is an agent of ozone destruction and PV intensification for sure.

Ok, now I'm a bit confused. I thought ozone destruction released energy due to the breaking of bonds between oxygen atoms? Why would that intensify the polar vortex?

[HM]

Ok, now I'm a bit confused. I thought ozone destruction released energy due to the breaking of bonds between oxygen atoms? Why would that intensify the polar vortex?

By combining with either nitrogen or hydrogen. You're right that it should help make more ozone, so the only way to actually destroy ozone is to have the free radicals combine with something else. In this case, water vapor and nitrogen are the main sources. N₂ and H₂ also will split in these proton events and help combine with oxygen.

[Snowstorms]

By combining with either nitrogen or hydrogen. You're right that it should help make more ozone, so the only way to actually destroy ozone is to have the free radicals combine with something else. In this case, water vapor and nitrogen are the main sources. N₂ and H₂ also will split in these proton events and help combine with oxygen.

Does sudden changes in stratospheric temperatures esp. across the Arctic due to shifting anomalies also destroy the Ozone? Like sudden shifts in the AO/AAO (negative to positive or vice versa). I think I read a paper that had something like that, cant remember which one.

S02 particles destroy the Ozone becoming sulfur particles in the atmosphere.

[bluewave]

The last +AO period in the spring occurred during the last active phase of the sun:

While the EPO / PNA will continue to respond to intranseasonal activity, I wouldn't expect the AO to drop considerably until the sun calms down. Notice in the last few days, we've had elevated proton levels (time sensitive; period of interest 11/26-28 2011):

http://www.solarham.com/proton.htm

This is an agent of ozone destruction and PV intensification for sure.

Kind of reminds me of some of the big month to month changes in the AO that we saw back in the the late 70's when the sun was becoming more active.

The sun has not reached that level of activity yet and the pattern is much warmer than those days. Quick changes that we saw in late 78 are like the

big flip from last winter going into the spring.

http://solarscience....ch/spot_num.txt

[HM]

Does sudden changes in stratospheric temperatures esp. across the Arctic due to shifting anomalies also destroy the Ozone? Like sudden shifts in the AO/AAO (negative to positive or vice versa). I think I read a paper that had something like that, cant remember which one.

S02 particles destroy the Ozone becoming sulfur particles in the atmosphere.

Stratospheric temperatures are ozone. So when a change in temperatures occur, it has to do with the amount of ozone.

[HM]

Chris, yeah that's interesting. Of course, there is more to it, but it is still pretty cool.

In 1999-2000 there was a relative maximum in the autumn and then a relative minimum December-January.

1999 6 137.7 33.3

1999 7 113.5 26.0

1999 8 93.7 42.7

1999 9 71.5 24.0

1999 10 116.7 27.9

1999 11 133.2 36.2

1999 12 84.6 18.2

2000 1 90.1 34.7

2000 2 112.9 24.3

2000 3 138.5 25.8

2000 4 125.5 29.4

[pcbjr]

This is all very interesting. I'm lost, though - it's so far above my comprehension level (sort of like cost accounting was when economics was my major). Anyway, can someone explain the ramifications short-term, mid-term and long range? Thanks (very humbly).

[vortmax112]

Great thread. I think we started to see some of this in the 90s..I mean look at what happened going from record little snow in the NE during 94-95 to a record max in 95-96. Variability has always been part of weather but NE snowfall seems to have become far more variable from year to year since the late 80s for reasons discussed in this thread. One year we're blow torched with a super positive AO / NAO and then the next year places like Baltimore and Boston are getting 80-100 inches with an extreme negative NAO

[bluewave]

Chris, yeah that's interesting. Of course, there is more to it, but it is still pretty cool.

In 1999-2000 there was a relative maximum in the autumn and then a relative minimum December-January.

1999 6 137.7 33.3

1999 7 113.5 26.0

1999 8 93.7 42.7

1999 9 71.5 24.0

1999 10 116.7 27.9

1999 11 133.2 36.2

1999 12 84.6 18.2

2000 1 90.1 34.7

2000 2 112.9 24.3

2000 3 138.5 25.8

2000 4 125.5 29.4

HM, that 1999-2000 analog was interesting with the dramatic change to colder and snowier that occurred later in January 2000 after a mild start.

We are also seeing a +EPO Scandinavian Ridge pattern this November like back in 1999, though this year is more amplified with less US warmth recently.

[Bob Chill]

I posted this in my regional thread but thought I should add it here because there seems to be some sort of connection. Why and how I really have no idea. I just like digging through numbers.

I usually try to find something to watch in the models and indicies but man, this is one boring period we're in. NAO and AO forecasts are absolutely atrocious. +PNA not gonna be around long either (not that the current +pna is doing anything).

If Dec ends up having a +NAO and AO monthly reading then it will be the first time since pre 1950 that both indices average in positive territory for the Sept - December timeframe. Individually the indices have stayed positive during the Sept - Dec timeframe a few times:

NAO: 56, 59, 99, 07

AO: 71, 75

99 is probably the closest statistical match I can find for matching both indicies together. The AO was just slightly negative in Oct.

1956 is the closest with the NAO. Quite similar in fact.

I did find an interesting connection between all these years. They are all Nina winters with the exception of 59. However, 59 did feature negative enso temps just not strong enough to classify it as a Nina.

Even deeper into the connection showed that 56, 71, 75, & 99 were all second or third year Ninas (75 was a 3rd year).

I would post the analog composite maps but I'm not going to. Trust me. You don't want to see them.

With the exception of 1975, December was warm to very warm in every other year.

I'm not sounding any alarms. Just posting what I found. But if December does come in warm I think the odds might be stacked against us a bit this year.

[bluewave]

I posted this in my regional thread but thought I should add it here because there seems to be some sort of connection. Why and how I really have no idea. I just like digging through numbers.

Yeah, there are some parallels to 1999. You can also include the record heat this July followed by tropical systems that will be remembered for their record rainfall like Floyd.

The last few winters have been very different with the record degrees of blocking than the late 90's though. Even during January 2000 we were able to manage late month

blocking with cold and snow in the East.

After December 1975, we experienced a very cold January though nothing like what was to follow in 1977.

[Bob Chill]

Yeah, there are some parallels to 1999.

Yes, and I've bumped into 1999 several other times looking at various analogs. Most discounted it early on for the upcoming winter because of what appears to be a longer term -NAO cycle that we're in. However, there is some concern building in the back of my brain thinking that the cycle may not continue this winter. No signs of it anywhere in the near future at least.

I'm interested to see what happens if and when the MJO cylces though phases 8-2 in later December. If there are still no signs of sustained blocking or arctic air intrusions in the EC during the next 3-4 weeks then you gotta wonder if we're in for a disappointment.

Looks like alot of the cold Dec forecasts are in jeopardy right now.

[bluewave]

Yes, and I've bumped into 1999 several other times looking at various analogs. Most discounted it early on for the upcoming winter because of what appears to be a longer term -NAO cycle that we're in. However, there is some concern building in the back of my brain thinking that the cycle may not continue this winter. No signs of it anywhere in the near future at least.

I'm interested to see what happens if and when the MJO cylces though phases 8-2 in later December. If there are still no signs of sustained blocking or arctic air intrusions in the EC during the next 3-4 weeks then you gotta wonder if we're in for a disappointment.

Looks like alot of the cold Dec forecasts are in jeopardy right now.

Yeah, but some other differences this year are the stormier pattern and less expansive warmth this November compared to 1999.

[usedtobe]

I think the differences are pattern related. 1999 was a pure positive epo pattern that floods the u.s. with warmth. This the pattern has been a negative pdo pattern which dumps some cooler air into the west.

[bluewave]

I think the differences are pattern related. 1999 was a pure positive epo pattern that floods the u.s. with warmth. This the pattern has been a negative pdo pattern which dumps some cooler air into the west.

True, you can see the colder forecast for the start of December compared to all the warmth back in 1999.

[tacoman25]

I think the differences are pattern related. 1999 was a pure positive epo pattern that floods the u.s. with warmth. This the pattern has been a negative pdo pattern which dumps some cooler air into the west.

Exactly. 1999 was in a low NPI phase, without the NE Pacific blocking more common in a +NPI/-PDO phase like we are in now.