January 2013 Pattern Discussion

[SACRUS]

I think that we have to go back to 92-93 to get above 20 inches on the season after a December below 2 inches.

Dec 2004 was pretty close. There was also a failry impressive turn around Jan '05, from frist half major warmth to secod half major cold and snow.

[bluewave]

Dec 2004 was pretty close. There was also a failry impressive turn around Jan '05, from frist half major warmth to secod half major cold and snow.

 

Yeah, 2004 I believe was just over the Trace to 2 inches list with 3, but the average monthly temperature

finished below 40 degrees.

[Isotherm]

I was looking at the correlations last night, and the AO only has a minor correlation to temperatures as far north as New York City...much less of a correlation than in the Southeast, and MUCH MUCH less than in Russia and Europe, where a -AO has turned this winter into a brutal one. What's really important here is the EPO, and the AO's impact on 500mb heights is much less in Alaska than Greenland. 

 

 

 

Disagree for the NYC area. AO has similar importance to the EPO, and the NAO is slightly less important but still a decent correlation for NYC. Just north of NYC, for most of New England, the EPO is clearly the most important temp indicator, followed by the AO, and NAO.

 

PNA has a weak correlation to temps for 40N northward, and increasing significance in PHL-DCA, and very crucial in the SE US. Thus from DC southward, they usually need a +PNA/-AO/-NAO to get big snows.

 

EP/NP index correlation: highest importance in the Mid west and Northeast

 

 

 

AO correlation - not too correlated from BOS northward, but NYC area southward is quite strong:

 

 

 

NAO correlation, > 0.4 from CT southward:

 

 

 

We can see why NNE is the place to be given they need to worry less about the state of these indices.

 

 

And the PNA... mostly important for 40N southward:

 

[doncat]

Dec 2004 was pretty close. There was also a failry impressive turn around Jan '05, from frist half major warmth to secod half major cold and snow.

Yeah Jan 2005 saw a hugh turnaround... My station averaged 41.0 degrees for the first 14 days then 19.7 for the next 17 days.

[nzucker]

Disagree for the NYC area. AO has similar importance to the EPO, and the NAO is slightly less important but still a decent correlation for NYC. Just north of NYC, for most of New England, the EPO is clearly the most important temp indicator, followed by the AO, and NAO.

 

PNA has a weak correlation to temps for 40N northward, and increasing significance in PHL-DCA, and very crucial in the SE US. Thus from DC southward, they usually need a +PNA/-AO/-NAO to get big snows.

 

EP/NP index correlation: highest importance in the Mid west and Northeast

 

 

 

 

AO correlation - not too correlated from BOS northward, but NYC area southward is quite strong:

 

The AO is correlated as high as .7 over a decent amount of Russia, and almost all Eurasia has a .6 correlation or better. That's clearly not true in the CONUS, where places like the northern Mid-Atlantic and New England have much less dependency on the AO for wintertime temperatures. NYC is sort of on the threshold between needing a -AO/+PNA and relying less on these indices. 

 

What I was also trying to point out is that the AO has the highest correlation with 500mb heights near the Kara Sea and over Greenland. Therefore, the -AO is most likely to make Asia cold (Kara block), second most likely to make Europe cold (Greenland block), but only somewhat likely to make North America cold because heights over Alaska and the GoA are much less dependent on the AO. So it's somewhat common to have a -AO/+EPO pattern. 

[Isotherm]

The AO is correlated as high as .7 over a decent amount of Russia, and almost all Eurasia has a .6 correlation or better. That's clearly not true in the CONUS, where places like the northern Mid-Atlantic and New England have much less dependency on the AO for wintertime temperatures. NYC is sort of on the threshold between needing a -AO/+PNA and relying less on these indices. 

 

What I was also trying to point out is that the AO has the highest correlation with 500mb heights near the Kara Sea and over Greenland. Therefore, the -AO is most likely to make Asia cold (Kara block), second most likely to make Europe cold (Greenland block), but only somewhat likely to make North America cold because heights over Alaska and the GoA are much less dependent on the AO. So it's somewhat common to have a -AO/+EPO pattern. 

 

 

 

Well if you're talking about the areas of the nern hem mid latitudes that are most likely to benefit from a -AO, I agree that Europe is better positioned than the CONUS.

 

They're positively correlated up to 0.8 or 0.9 in the red shaded areas. Japan/Far East looks similar to the Eastern US in terms of correlation to -AO at the 500mb level.

 

[Isotherm]

Surface temp correlations - Europe again strongest, and portions of Asia are more correlated than the US as you said. EPO is definitely most important temp wise for the northern United States, we agree on that.

 

[bluewave]

The usual combination necessary for NYC to drop below 10 degrees is

-EPO/+PNA/-AO/-NAO. The following composite is made up of 20 dates

from 2000-2011 that NYC made below 10 degrees.

 

 

 

[Isotherm]

Yeah we've got to align the stars for all 4 of those indices for our coldest temps. The pattern for the second half of Jan could be -PNA/-EPO/-AO/-NAO which would center the most negative temp anomalies in the Central Plains.

[tombo82685]

Yeah we've got to align the stars for all 4 of those indices for our coldest temps. The pattern for the second half of Jan could be -PNA/-EPO/-AO/-NAO which would center the most negative temp anomalies in the Central Plains.

In terms of snow, center of the trof over miss river would be a good snow pattern. You would have the cold, though not bitter and just enough se ridge to bring storms up

[uncle W]

I've showed when the ao is at it's lowest point NYC usually gets snow or cold or both...I think we haven't seen the ao at it's lowest point...I believe it gets below -4.000 and that's when we will see something that resembles real winter weather...If it doesn't then it could be a disaster...

[mulen]

All we need is the right timing the cold is so close it'll snow cyrstal balls tend to blowup in my face.Happy new year unc peace.

[JBG]

Warmth always seems to overpreform. We are probably looking a 10 to 14 day stretch that will finish above normal. If i had to bet it would b to the higher end of the range. But my hope is the last 10 days of jan r as harsh as the middle 10 will b nice

 

I wish that were true during the summer. 

 

All kidding aside, it's the first day of the warm spell that usually overperforms.  After that the sea breezes and hovering back-door fronts put a damper on the temperature. January 6 and 7, 2007 are perfect examples.

[MJO812]

Don Sutherland
 

1. A renewed period of blocking (AO-) appears increasingly likely. Blocking analogs cited in #6 and the larger pool in #25 indicated a high probability that the January AO would average < 0. The main winter blocking analogs I cited were 1966-67, 1981-82, 2002-03, 2009-10. There has been a stratospheric warming event. Sometimes those events reflect a bottom-up response to a blocking regime (one just ended) and sometimes they reflect a top-down situation that would lead to renewed blocking. The stratospheric warming has gone down to about 10 mb. Personally, I'd like to see it propagate further down beyond 30 mb as happened during the 2009-10 winter. The GFS ensembles are in good agreement about the AO's going negative, possibly even tanking down the road.


2. There is good consensus on the ensembles that the EPO will go negative.


3. We are now in the transition to a period of moderation. Temperatures will likely peak in the East on Sunday-Tuesday (1/13-15). As noted previously, this is a temporary period of warmth. It is not the end of winter so to speak. Around 1/20 +/- a few days, the changes in the AO and EPO should produce a colder pattern and that pattern is likely to be of longer duration and greater magnitude than the one that is ending. The Plains States will likely see the cold occur first and they could also experience the largest cold anomalies.

 

[HailMan06]

Wow great discussion yesterday from you guys, one of the best I have seen here. I am learning so much from this thanks again.