December 2017 Discussions & Observations Thread

[SnoSki14]

Wow look at that massive SE ridge on the gfs, it keeps getting stronger every run. Huge torch for Christmas 60F+ possible, like clockwork. 

[Eduardo]

1 hour ago, bluewave said:

The Pacific based blocking since mid-2013 has been as impressive in its own right as the Atlantic was from 2009-2013. The WPAC forcing and -EPO block continues to be the main event.

 

 

 

What do you think accounts for its resiliency in spite of varying ENSO states though (aside from maybe the 2016 super Niño)?  One thing I've noticed is oceanic warmth somewhere east of Hawaii.  This year, we have a warm "blob" centered just off of the Baja coast:

 

In previous years, we saw it displaced further north:

Possible that those high SST anomalies in that region have yielded such an awesome multi-year PAC blocking regime?  Or am I totally off-base?  Just a hypothesizing hobbyist over here.....

ETA: Having trouble posting images in order.  Sorry if readers have to piece my post together a bit.  Buggy upgrade....growing pains :-P

[Paragon]

6 hours ago, snowman19 said:

There in lies a problem, once we loose the Pacific, and there are signs that MAY (may) happen come January, we are dead in the water. The NAO hasn’t cooperated in years, it just wants to default positive in winter and the AO hasn’t really either, it’s been more neutral so far recently however. If the -EPO/-WPO go bye bye, it’s going to get ugly real fast. With a background La Niña in place, the PNA isn’t going to cooperate (+) for long periods of time

This is one reason why I suspect the -NAO calls for upcoming winters after this one may not pan out.  There seems to be a definite climate shift towards more +NAO.

Then again it may not matter much if we also continue to see the shift towards -EPO.

 

[Paragon]

6 hours ago, bluewave said:

There could very well be a period of Pacific blocking relaxation or reversal after January 7th. But that doesn't mean that we won't  see any more -EPO intervals during the remainder of the winter. The La Nina last winter still produced snowy periods despite the warmth in each of the winter months when the EPO went negative. The slightly -EPO last DJF was all that was needed to get us to normal to above normal snowfall. We have already exceeded the normal December snowfall and the month is only half way through. It just wants to snow in the new climate regime here.

Funny thing is, I don't recall anyone talking about the EPO before the last few winters.  Is this a new index that we've hashed out in the last five years?  I remember we used to talk much more about the PNA and PDO before this, but starting in 2013, the EPO began to be mentioned much more frequently.

 

[Paragon]

1 hour ago, Eduardo said:

What do you think accounts for its resiliency in spite of varying ENSO states though (aside from maybe the 2016 super Niño)?  One thing I've noticed is oceanic warmth somewhere east of Hawaii.  This year, we have a warm "blob" centered just off of the Baja coast:

 

In previous years, we saw it displaced further north:

Possible that those high SST anomalies in that region have yielded such an awesome multi-year PAC blocking regime?  Or am I totally off-base?  Just a hypothesizing hobbyist over here.....

ETA: Having trouble posting images in order.  Sorry if readers have to piece my post together a bit.  Buggy upgrade....growing pains :-P

It's the same reason why the avg precip in NYC is up to 50 inches from 42 inches lol.  The warmth actually extends far below the surface.  Get used to it- it's our new climate.

 

[donsutherland1]

8 minutes ago, Paragon said:

Funny thing is, I don't recall anyone talking about the EPO before the last few winters.  Is this a new index that we've hashed out in the last five years?  I remember we used to talk much more about the PNA and PDO before this, but starting in 2013, the EPO began to be mentioned much more frequently.

 

It's not new, but it likely wasn't mentioned during winters 2009-10 and 2010-11, because a super negative AO was, by far, the dominant feature that shaped those winters. The extreme AO- essentially overwhelming every aspect of the pattern.

[Isotherm]

The mean positive NAO modality is congruous with my winter outlook, namely the indicator-specific conditions I analyzed pre-season, which were highly suggestive of a positive mean (with some spasmodic negative dips). This predilection isn't a function of a climate regime shift, but rather, of certain, recurring forcing mechanisms both internal/endogenous and exogenous. 

Going forward, my thoughts remain consistent with the initial forecast for a SECS or greater event in the 15th-30th period (now narrowed to 22nd-30th). Background factors become less propitious for the maintenance of high latitude blocking as we head deeper into the winter, and there will be a tendency to retrograde the poleward Pacific ridging, introducing a higher likelihood of SE-ridge contamination. But there's plenty of time to discuss that later; my confidence is still very high that the models are incorrectly detecting the onset of higher geopotential heights in the NAO/AO domains D 7-15. I would continue to monitor the period beginning around the 23rd and beyond for a winter event near the east coast. 

[Stormlover74]

Hovering at 35 for the past few hours. Still supposed to drop another 11 degrees

[psv88]

9.8” of snow already. Pretty incredible start out here.

[SnoSki14]

Holy crap at that Arctic surge around and after Christmas especially for Central & Southern/Southeast US on the gfs. 

I think I saw teens in New Orleans and 30s down to Miami. 

[Paragon]

2 hours ago, Isotherm said:

The mean positive NAO modality is congruous with my winter outlook, namely the indicator-specific conditions I analyzed pre-season, which were highly suggestive of a positive mean (with some spasmodic negative dips). This predilection isn't a function of a climate regime shift, but rather, of certain, recurring forcing mechanisms both internal/endogenous and exogenous. 

Going forward, my thoughts remain consistent with the initial forecast for a SECS or greater event in the 15th-30th period (now narrowed to 22nd-30th). Background factors become less propitious for the maintenance of high latitude blocking as we head deeper into the winter, and there will be a tendency to retrograde the poleward Pacific ridging, introducing a higher likelihood of SE-ridge contamination. But there's plenty of time to discuss that later; my confidence is still very high that the models are incorrectly detecting the onset of higher geopotential heights in the NAO/AO domains D 7-15. I would continue to monitor the period beginning around the 23rd and beyond for a winter event near the east coast. 

But what we've been talking about is that pos NAO seems to have become the climatic norm, not just for this winter but in general.  It's one of the reasons I doubt going back to sustained neg NAO winters in the future, outside of a renegade season or two.  So let's say that around 70% of all winters are pos NAO winters.  Outside of a few outlier winters, it seems that far more winters are pos NAO than neg.  Also, since east-based neg nao are also unfavorable for us, it seems that three out of the four NAO groupings have an unfavorable outcome.

Also going forward, it seems as though the first half of Jan might be a lot better for wintry weather than the second half.

Of course it might not matter at all with a favorable Pacific.

 

[CIK62]

Next 8 days jump to 42deg. average, or 5degs. AN.  I think I made a mistake with yesterday's arithmetic.

[CIK62]

GFS still has Christmas Morn @+8degs. and ditto for New Years Hangover Morn, with a deep freeze in between them.

 GFS also wants to waste 2" of liquid w/o a snowflake for us, over just the next 10 days.

[WEATHERBUFF]

6 minutes ago, CIK62 said:

GFS still has Christmas Morn @+8degs. and ditto for New Years Hangover Morn, with a deep freeze in between them.

 GFS also wants to waste 2" of liquid w/o a snowflake for us, over just the next 10 days.

gfs is not reliable beyond a few days.

[LurkerBoy]

5 minutes ago, bluewave said:

This will be our December thaw week before the -EPO and cold reloads for later in the month.

 

 

 

Any chance of that cutter shearing out more the 23rd? 

[SACRUS]

With plenty of cold air source near by and what appears to be an active period 12/24 - beyond, i like our chances of some additional and potentially significant accumulations by new years.  I am sure there will be close calls, mixing/changeovers but i could see us doubling our monthly accums between Christmas and new years

[MJO812]

5 minutes ago, LurkerBoy said:

Any chance of that cutter shearing out more the 23rd? 

I think that one is a cutter.

It helps reload the cold pattern

[snowman19]

8 hours ago, SnoSki14 said:

Holy crap at that Arctic surge around and after Christmas especially for Central & Southern/Southeast US on the gfs. 

I think I saw teens in New Orleans and 30s down to Miami. 

Front loaded winter. Typical for a La Niña. We saw something similar in 1989, which I think is a decent analog now 

[MJO812]

3 minutes ago, snowman19 said:

Front loaded winter. Typical for a La Niña. We saw something similar in 1989, which I think is a decent analog now 

2010-2011 was a front loaded winter

[MJO812]

8 hours ago, SnoSki14 said:

Holy crap at that Arctic surge around and after Christmas especially for Central & Southern/Southeast US on the gfs. 

I think I saw teens in New Orleans and 30s down to Miami. 

It's called winter

[snowman19]

2 minutes ago, Snow88 said:

2010-2011 was a front loaded winter

Sure was, by the last week of January 2011, it was all over 

[Ralph Wiggum]

GFS still has Christmas Morn @+8degs. and ditto for New Years Hangover Morn, with a deep freeze in between them.
 GFS also wants to waste 2" of liquid w/o a snowflake for us, over just the next 10 days.

Are you using a GFS op run to make a 15 day forecast?

[Ralph Wiggum]

Any chance of that cutter shearing out more the 23rd? 

We need that cutter. Sacrificial lamb so-to-speak.

[TriPol]

22 minutes ago, Ralph Wiggum said:

56 minutes ago, LurkerBoy said:

Any chance of that cutter shearing out more the 23rd? 

We need that cutter. Sacrificial lamb so-to-speak.

[mranger48]

1 hour ago, CIK62 said:

GFS still has Christmas Morn @+8degs. and ditto for New Years Hangover Morn, with a deep freeze in between them.

 GFS also wants to waste 2" of liquid w/o a snowflake for us, over just the next 10 days.

Not to be rude, but it would make more sense to compare and contrast the euro and gfs ENSEMBLES day by day against the norm. This would be far more valuable data to the board, as opposed to posting 1 operational run’s output daily. Idk maybe I’m crazy

[SnoSki14]

Today's AO forecast stays more positive, which means the SE ridge could have a lot more staying power than thought. 

Very skeptical about the pattern going forward. 

[MJO812]

1 minute ago, SnoSki14 said:

Today's AO forecast stays more positive, which means the SE ridge could have a lot more staying power than thought. 

Very skeptical about the pattern going forward. 

Have you looked at the epo ?

You have been on the warm train since the start of December.

[Isotherm]

9 hours ago, Paragon said:

But what we've been talking about is that pos NAO seems to have become the climatic norm, not just for this winter but in general.  It's one of the reasons I doubt going back to sustained neg NAO winters in the future, outside of a renegade season or two.  So let's say that around 70% of all winters are pos NAO winters.  Outside of a few outlier winters, it seems that far more winters are pos NAO than neg.  Also, since east-based neg nao are also unfavorable for us, it seems that three out of the four NAO groupings have an unfavorable outcome.

Also going forward, it seems as though the first half of Jan might be a lot better for wintry weather than the second half.

Of course it might not matter at all with a favorable Pacific.

 

 

But that isn't correct. The NAO variance on the positive side has not been statistically significant; the positive tendency over the past several years is well within averages. Keep in mind, NAO periodicity is such that there are usually protracted spells of negative or positive modality. For example, in the 1961-1971 period, only 2 winters featured a +NAO.

This recent period of +NAO, 2012-2018 is similar in length to the 1987-1994 +NAO period (every winter in this time frame was +NAO). We should be very thankful that the Pacific forcing has been sufficiently conducive to countervail the less auspicious Atlantic. 

I expect this NAO tendency to reverse soon, but not this current winter (although there will be more negative dips than the past couple of years).

[Isotherm]

People myopically focusing on index forecasts such as the large error bar, long term AO guidance, will be completely missing this upcoming period of potentially severe Arctic chill for the nation as a whole. The higher geopotential heights will invariably expand into the AO domain as well as western NAO domain, as concerted MJO/strat forcing continue to manifest. The anomalous negative standard deviations in the EPO will produce significant dense, low level arctic air which will suppress the thermal boundary further south than heights and even 850mb temperatures indicate. It's the type of pattern in which 2m freezing lines could be south of 0c 850mb lines, introducing freezing rain threats as well for parts of the Central/East. Again, operational guidance has proven futile in terms of prognostication ability here. 

[AfewUniversesBelowNormal]

10mb warming is now, began on Dec 8 with significant pattern shift... this is not something that just goes away on models.