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Typhoon Tip

December pattern discussion, part II

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i like how the ec ens look in the long range.  heart of the cold is centered just north of new england and up to James Bay. and it's not mediocre cold either.

 

We had a lovely debate at work about January. Long range guys want to warm the CONUS and think ridging near AK will break down, but myself and a few other medium range guys did not agree. If nothing else, the EC has been to bullish breaking it down only to show it coming back with vengeance inside day 10. Plus, you have that Scandinavian block forming which is sort of new and that also helps to lock in the PV. The EC was a bit higher with heights near AK on this run as well.

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I think it is too soon to conclude this to be a "+AO winter" - we are just over midway through the first Met winter month; there is plenty of time for different modes to evolve.  In fact the longer term trend slipped negative recently, so using that linear extrapolation ... positive isn't really support.  Which, admittedly, is neolithically stupid to say because we all know that the longer term curve is a serrated ride.  Still, there is a reason that background trend is taking place.  What that is, who knows -- maybe it's keyed into the solar and all that jazz. Maybe is some giant Pac sloshing of the PDO and ...yadda yadda yadda   QBO notwithstanding...

 

Granted, some leading outside factors don't correlate too well with SSWs, but SSWs can also disrupt the positive phase (should one occur).   Heh, no sign of one anytime soon.

 

Anyway, the -EPO is no mystery in why we have been cold.  In fact, inside the domain of the AO, it doesn't matter if it is positive or negative; it is cold inside that domain space. The index can be positive or negative, doesn't matter if the EPO domain is forcing a NW/NNW flow into the NW territories.  It's going to grab that air and bring it into the Canadian shield.

 

you know when you think about it... You can have a +PNA/+EPO/-AO and that another cold conveyor, too.   'Course, can't forget a solid -AO/-NAO, either.   

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maybe the follow up wave has legs? euro ens mean has anafrontal precip on xmas eve

Euro op has been awful at this range with these borderline, non phased systems. Always surpressed always wrong. Think this one is coming.

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i like how the ec ens look in the long range.  heart of the cold is centered just north of new england and up to James Bay. and it's not mediocre cold either.

Seriously that is January 1994 to a t.

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With respect to the AO, the AO has averaged +1.767 this month (12/1-19). Assuming it averages +1 to +2 for the remainder of December, it would finish with a monthly average of +1.470 to +1.857. Even if it averages 0.0 for the rest of December, it would finish the month with a +1.083 average.

 

Since 1950, there have been 13 winters that featured a December AO average of +1 or above. 12/13 (92%) of those cases also had a positive average for the December-February period. The lone winter with a negative average was 1979-80 (December figure: +1.295). That's the bad news so to speak.

 

The better news is that 10/13 (77%) cases saw the January-February AO average come out lower than the December figure and 7/13 (53%) cases saw the January-February figure average 1 or more points below the December average.

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With respect to the AO, the AO has averaged +1.767 this month (12/1-19). Assuming it averages +1 to +2 for the remainder of December, it would finish with a monthly average of +1.470 to +1.857. Even if it averages 0.0 for the rest of December, it would finish the month with a +1.083 average.

Since 1950, there have been 13 winters that featured a December AO average of +1 or above. 12/13 (92%) of those cases also had a positive average for the December-February period. The lone winter with a negative average was 1979-80 (December figure: +1.295). That's the bad news so to speak.

The better news is that 10/13 (77%) cases saw the January-February AO average come out lower than the December figure and 7/13 (53%) cases saw the January-February figure average 1 or more points below the December average.

I kind of like this style AO with the massive cold nearby, certainly has fooled a lot of prognostic outlooks since Nov.

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Weeklies look atrocious Weeks 3/4, from what I've read. It's their unreliable range, so take it FWIW.

 

yea weeklies haven't really had the hot hand lately...move on :thumbsdown:

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Weeklies are derived from mjo forecasts I believe.

Lol and they are not bad for us, week 3 is great actually, week four the EPO is rebuilding, Euro has beat it down consistently. Gradient remains, think Leon 70_71 combo

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Lol and they are not bad for us, week 3 is great actually, week four the EPO is rebuilding, Euro has beat it down consistently. Gradient remains, think Leon 70_71 combo

 

That's odd. I read something completely different about what the weeklies showed. 

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That's odd. I read something completely different about what the weeklies showed.

for South of NE its not as good although it's still pretty much status quo and rebuilding. I would lean cold

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Weeklies had an Aleutian low, ridging Over the west and slight ridging over the northeast at week 4. It wasn't bad at all. Week 4 has been awful though as far as forecast accuracy.

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Weeklies had an Aleutian low, ridging Over the west and slight ridging over the northeast at week 4. It wasn't bad at all. Week 4 has been awful though as far as forecast accuracy.

that's what I took out of it

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With respect to the AO, the AO has averaged +1.767 this month (12/1-19). Assuming it averages +1 to +2 for the remainder of December, it would finish with a monthly average of +1.470 to +1.857. Even if it averages 0.0 for the rest of December, it would finish the month with a +1.083 average.

 

Since 1950, there have been 13 winters that featured a December AO average of +1 or above. 12/13 (92%) of those cases also had a positive average for the December-February period. The lone winter with a negative average was 1979-80 (December figure: +1.295). That's the bad news so to speak.

 

The better news is that 10/13 (77%) cases saw the January-February AO average come out lower than the December figure and 7/13 (53%) cases saw the January-February figure average 1 or more points below the December average.

 

 

Hi Don ... I like the your statistical approach.  

 

I have bolded the region that is most important to me.  The reason why is, "since 1950," a significant number of decades were spent in a rising longer term oscillation, such that lowering January and February's landed within a positive region -- granted mainly the 1980s, '90s, and through 2005 (or so).  However, now that we are on the descending aspect of the curve, I am wondering how a downward modality might look this year, should the same downward Jan/Feb trend take place.

 

One thing that is unrelated but fascinating is that the extreme -AO years, have a greater SD than the positive years.  There is more clustering of more modestly positive AO winters, and only one positive AO year that rivals the extremeness of multiple negative years going back across the last 100 years or so.  Here is one of many graphs:

 

800px-Arctic_Oscillation.svg.png

 

What should leap out is that there is 1 ... arguably 2 seasons that exceeded +2SD, but there are 4 that neared or exceed -2SD. It seems from this 100 year data sample that the positive state is the preferred state, but it is offset by extreme negatives.  That's ...amazing for me.  I don't think that is random.  One supposition is that there is a 20 to 30 year periodicity there. But that doesn't really lend much to where we are headed into early 2014.  

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Hi Don ... I like the your statistical approach.  

 

I have bolded the region that is most important to me.  The reason why is, "since 1950," a significant number of decades were spent in a rising longer term oscillation, such that lowering January and February's landed within a positive region -- granted mainly the 1980s, '90s, and through 2005 (or so).  However, now that we are on the descending aspect of the curve, I am wondering how a downward modality might look this year, should the same downward Jan/Feb trend take place.

 

One thing that is unrelated but fascinating is that the extreme -AO years, have a greater SD than the positive years.  There is more clustering of more modestly positive AO winters, and only one positive AO year that rivals the extremeness of multiple negative years going back across the last 100 years or so.  Here is one of many graphs:

 

800px-Arctic_Oscillation.svg.png

 

What should leap out is that there is 1 ... arguably 2 seasons that exceeded +2SD, but there are 4 that neared or exceed -2SD. It seems from this 100 year data sample that the positive state is the preferred state, but it is offset by extreme negatives.  That's ...amazing for me.  I don't think that is random.  One supposition is that there is a 20 to 30 year periodicity there. But that doesn't really lend much to where we are headed into early 2014.  

Thanks Tip.

 

By any chance do you have monthly values prior to 1950. Any enlargement of the sample would be helpful.

 

Finally, I agree with you about the extremes (more frequent extremes on the negative side) not being random. I don't believe the AO is a normal distribution.

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Thanks Tip.

 

By any chance do you have monthly values prior to 1950. Any enlargement of the sample would be helpful.

 

Finally, I agree with you about the extremes (more frequent extremes on the negative side) not being random. I don't believe the AO is a normal distribution.

 

 

I found this. It looks like it matches the CPC values fairly well where they overlap, though it is not exact. (obviously these values are multiplied times 100)

 

 

http://jisao.washington.edu/ao/ao18992002

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Thanks Tip.

 

By any chance do you have monthly values prior to 1950. Any enlargement of the sample would be helpful.

 

Finally, I agree with you about the extremes (more frequent extremes on the negative side) not being random. I don't believe the AO is a normal distribution.

 

Something is driving that (bold).  

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Thanks Tip.

 

By any chance do you have monthly values prior to 1950. Any enlargement of the sample would be helpful.

 

Finally, I agree with you about the extremes (more frequent extremes on the negative side) not being random. I don't believe the AO is a normal distribution.

 

 

This could be explained by the fact that a positive AO (or high index annular mode) is basically amplified climatology, whereas a negative AO can be more significantly anomalous from the background state.

 

Can this be replicated in ENSO data? Tend to get slightly more extreme El Ninos than we do La Ninas.

 

Of course all this is based upon the methodology of how we measure these oscillations.

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Looks like we lost our snow event Christmas Eve and Day on the 00z runs

 

NAM, GFS, EURO, GGEM to some extent all have more so rain impacting us from the frontal wave as well as the UKMET model.  They just don't show the temps dropping enough for an all snow event, instead its a rain event.  But they still have the low.

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NAM, GFS, EURO, GGEM to some extent all have more so rain impacting us from the frontal wave as well as the UKMET model.  They just don't show the temps dropping enough for an all snow event, instead its a rain event.  But they still have the low.

That's on Monday. The one Tuesday night is gone. Maybe the ensembles show different..but it's pretty depressing

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Looks like we lost our snow event Christmas Eve and Day on the 00z runs

No surprise there. I think the next 3 weeks could well tell the tale for this winter. The positive AO/NAO has always concerned me even with the cold and snowy start to winter. 

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No surprise there. I think the next 3 weeks could well tell the tale for this winter. The positive AO/NAO has always concerned me even with the cold and snowy start to winter. 

As long as we keep the +WPO and -EPO we should be good. Ensembles have been showing the PV splitting and the core of the cold shifting east from the Lakes to Northeast rather than centered over the N Plains. It looks stormy and cold after this disasterous weekend

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As long as we keep the +WPO and -EPO we should be good. Ensembles have been showing the PV splitting and the core of the cold shifting east from the Lakes to Northeast rather than centered over the N Plains. It looks stormy and cold after this disasterous weekend

It looks cold to me but I don't know about stormy...maybe into January but looking at a lot of the models we may have a shot up north of light clipper snow showers later next week, other than that it's just cold and dry through New Years.

It's like the 6z GFS said "Merry Xmas" and gives like ten days of cold/dry, then throws in an inland runner/cutter to break up the cold/dry. The lack of blocking should lead to more mixed events and track will probably be an issue for a while.

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It looks cold to me but I don't know about stormy...maybe into January but looking at a lot of the models we may have a shot up north of light clipper snow showers later next week, other than that it's just cold and dry through New Years.

It's like the 6z GFS said "Merry Xmas" and gives like ten days of cold/dry, then throws in an inland runner/cutter to break up the cold/dry. The lack of blocking should lead to more mixed events and track will probably be an issue for a while.

We haven't had blocking all winter. Sne is above for snow and below for temps. What's the status in NNE? We didn't have blocking in 1993-94 or 1992-93. Both blockbusters for snow and 93-94 was brutal non stop cold. There is a lot to the equation. EPO to get the cold in Canada but I'm not sure it's as dominant force as we think. Solar? Activity but a weak sun now but now do we explain a hot July? Apt of intrigue here.

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Let's the wrist cutting end. The overall pattern continues with -EPO and +NAO. The potential is there. Yes there may be a lakes cutter at some

Point but as long as this pattern is there with arctic air available...the chances look goo to get snow.

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