Moving on to mid/late November

[ORH_wxman]

6 weeks starting Oct 30. Build. Ignite. Boom

I'd like to get a white Thanksgiving in the hills at least...we avg one about 25% of the time....been since 2005, so we are due. Not sure this year will happen though because the pattern looks pretty crappy though maybe by the 24th (T-day) it will be good enough for a snow threat.

[CoastalWx]

All snow, all the time. I think it's funny how people can get so down over the LR. Beautiful surprises like this last storm will happen regardless of what the warministas say. Never fear, Winter is here.

Well I hope nobody gets down from the next two weeks. That doesn't necessarily mean anything for this winter, so I hope people aren't down...other than the fact it could be boring.

[Ji]

Terrible terrible pattern coming but I'm not ready to cancel winter yet

[Typhoon Tip]

Man it looks warm the next 2+ weeks aside from a transient cooldown. The NAO does try to go west based, but big time -PNA causes a se ridge big time.

I see this completely different - oy vay. ( lol )

Folks - I wouldn't count on that sort large scale circulation orientation working out too well (as described above), even though some operational runs are trying to pull that off... This is not to refute a warm notion for a few days, but one or the other drillers will dominate most likely. If the -NAO arrives on time, those wave lengths as depicted where you see a ridge node up the East Coast, and negative node over NE Ontario, and another positive node over Baffen Island will almost never work out save for very transient (day and a half) lengths of time. Planetary physics et al, that is just too unstable of a large scale regime to persist. This whole west-based, east- based NAO is extremely important, because rather than settling into an absurd configuration like that, the -NAO will most likely be east based, allowing the wave-lengths to stretch, or west based ... crushing the SE heights into a compressed flow of high balanced geopotential winds - either way, wave-lengths are conserved.

Personally, I think things try to remain more sneakily seasonable nearing 40 N and possibly below normal for November as a whole, N of that parallel - more below.

Negative NAO appears to want to emerge according to CPC/CDC qualitative agreement; both signaling ~ -1SD. Most (at least) GFS ensemble members on board for the index collapse, with the usual mop ending as to how much. This ending notion lends confidence to the -NAO righting the cold ship beginning D7 and onward in time.

Caveat Emptor: I am aware that others are Euro cluster reliant and that source may differ for appeal currently, but I have found competitive error values beyond D7...certainly D10 regardless of camp. Point being '6 of 1/2 a dozen of the other'. I also will tip a secret that I have no problem with anyone wanting to assume at least some canvas tinting prior to painting the synoptic picture being biased toward cool because of the multi-decadal AO/NOA/EPO variant having gone negative recently - it's a not an out right corrective measure, but an on-going bias however subtle.

The last 3 nights of AO computation at CPC is showing a new 2 week descent to -1SD as an ensemble mean of the GFS cluster ; this is a pattern of behavior also modeled around October 10 One thing that has piqued my interest about it this time is that unlike October, this time the ensembles are moving the AO/NAO in tandem; that is the longer term preferred state due to their shared domain space.

The wild card in this is the EPO. At least 2 runs in the last 3 days worth of GFS have shown somewhat more robust height anomalies over Alaska, with undercutting Pac flow consistent with a stubborn -PNA. Others have noted this but I caution that the -PNA/-EPO opposes the correlation coefficient for those two teleconnectors. Be that the case, the CDC monitoring for this index changed rather abruptly nearing November 1; previous days if not weeks of dominating positive values were snap-shocked negative. That has eased some, but neutralization of the field in general still argues for the possibility of as yet modeled ridging to pop in the Alaskan region. That advent of that has a correlation off the WPO (West Pac Oscillation), which makes sense considering R-wave counts and dispersion down stream. And interesting, the WPO neutralized and/or went negative in the outlook at about the same time. Bottom line, the negative PNA may not be as important over all to establishing the direction of our temperature anomalies if when in quadrature it's individual components show that the index's whole value has cold contaminating appeals. The EPO is a tiney domain compared to the whole of the PNA; the two can exist for awhile in anti-correlated phase state and what do you have? You end up with huge cold loading potential into southern or event SE Canada, with warmth raging in the MV to lower MA. That is a volatile large scale intense baroclinic nightmare for any extended range forecaster!

Not a certainty on the -EPO, but again ... as I've discussed in the past, the actual scalar value at a point in time is less important than the differential leading. Seeing days/weeks of +EPO suddenly go neutral and/or negative is pretty telling that the mass fields want to change this month for that circulation region.

We have a tentative teleconnector converging going on here. It flags a 2 week cold episode despite the current warm operational appeals; one that begins around D7 but perhaps waits a click or two to gain momentum.

In the dailies I still think we have a good shot at a White Thanks Giggedy this go... but obviously at this range that is a fun conjecture for the challenge of seeing that emerge, and not much more. However, the D7 trough translation should end a 2 to 3 day stint of positive departures. Then we have falling AO/NAO, with neutralized EPO, and believe it or not, both the CDC/CPC have the PNA rising between the 12th and the 20th of this month - how much remains to be seen but who cares as long as it is rising.

[ORH_wxman]

John I think the Pacific is going to overwhelm the NAO signal at least the first 2-3 weeks...it may break down to the Atlantic by the end of the month though. A good example of a heavily -PNA and -NAO pattern is December 1996 and we torched in that pattern while the N plains and N rockies froze. I think this pattern isn't too dissimilar and might be quite similar on many levels. We may sneak some colder air in than what is advertised currently, I certainly won't disagree on that point, but I think the mean will be comfortably above average through about the 20th.

Beyond this is far enough out to see a big breakdown in the pattern and we could certainly freeze our butts off late in the month if the EPO goes nuts on us with a well placed NAO. So I wouldn't be confident in saying the month as a whole will be a torch, but the first 3 week look overall on the mild side to me.

[snowNH]

GFS keeps hinting at a monster phased storm for the midwest around day 10-12... possible change to pattern after that?

[weathafella]

All going fine. 11/5 average max runs 50+ for most of us. Not too many Novembers ran 15 subnormal If any. And if this one did....most assuredly it would be tough to hold until mid march.

[Typhoon Tip]

John I think the Pacific is going to overwhelm the NAO signal at least the first 2-3 weeks...it may break down to the Atlantic by the end of the month though. A good example of a heavily -PNA and -NAO pattern is December 1996 and we torched in that pattern while the N plains and N rockies froze. I think this pattern isn't too dissimilar and might be quite similar on many levels. We may sneak some colder air in than what is advertised currently, I certainly won't disagree on that point, but I think the mean will be comfortably above average through about the 20th.

Beyond this is far enough out to see a big breakdown in the pattern and we could certainly freeze our butts off late in the month if the EPO goes nuts on us with a well placed NAO. So I wouldn't be confident in saying the month as a whole will be a torch, but the first 3 week look overall on the mild side to me.

Certainly be interesting to see how it all plays out. Keep in mind though that the PNA is rising beginning in 7 days, and it is an emerging signal that may gather momentum going forward.

Also, one thing I am noticing is that the majority of the MJO strength bias is on the left side of the Wheeler diagram. Interestingly this took place much of last winter, such that when the MJO was ever more than weak in strength it it was always 1, 7, 8, and 2. Who knows if that will be the case this year too, but the last month is showing the same behavior thus far... If it does this again over the next 30 days, we'll see the PNA likely do just that and gather momentum.

Cool.

[snowNH]

Certainly be interesting to see how it all plays out. Keep in mind though that the PNA is rising beginning in 7 days, and it is an emerging signal that may gather momentum going forward.

Also, one thing I am noticing is that the majority of the MJO strength bias is on the left side of the Wheeler diagram. Interestingly this took place much of last winter, such that when the MJO was ever more than weak in strength it it was always 1, 7, 8, and 2. Who knows if that will be the case this year too, but the last month is showing the same behavior thus far... If it does this again over the next 30 days, we'll see the PNA likely do just that and gather momentum.

Cool.

What did we have last year? -NAO and +PNA?

Is there a site that explains everything?

[weathafella]

Well the GFS beyond this week is not warm....in fact there are some very nice changes. Similar to the Euro there's a stab of cold for a couple days around d7 and that appears to set the table for greater cold in length and strength as we move forward. Iow....cold comes and goes but each time it comes it stays a bit linger and of course is stronger. Nice GFS run today.

[Typhoon Tip]

What did we have last year? -NAO and +PNA?

Is there a site that explains everything?

There are sites that contain these indices (archived); I would start with the Climate Diagnostic Center (CDC). Will would be better to ask then me, but I believe the predominate signal was indeed the +PNA/-NAO, but it really didn't kick in meaningfully for us in terms of creating cold and snow locally until after X-Mass.

As far as "explaining" - not sure what you mean. If you are seeking a basic primer on NAO and PNA, just go to Google and type that in, and you'll be greeted by lots of reference material. Actually, Wikipedia undoubtedly has reams of info on atmosheric indices, but be careful with Wiki - it's refereeing on material isn't officiated.

[ORH_wxman]

There are sites that contain these indices (archived); I would start with the Climate Diagnostic Center (CDC). Will would be better to ask then me, but I believe the predominate signal was indeed the +PNA/-NAO, but it really didn't kick in meaningfully for us in terms of creating cold and snow locally until after X-Mass.

As far as "explaining" - not sure what you mean. If you are seeking a basic primer on NAO and PNA, just go to Google and type that in, and you'll be greeted by lots of reference material. Actually, Wikipedia undoubtedly has reams of info on atmosheric indices, but be careful with Wiki - it's refereeing on material isn't officiated.

The predominate signal was actually -PNA/-NAO last year but we did get a solid burst of a +PNA during about the Jan 14-Feb 5 period which sustained out cold/snowy regime when the NAO block broke down during the Archambault type Jan 12th event....we got lucky with a nice MJO wave robust in the 7,8,1 region and another temporary -NAO right before the Jan 27 event. Then we lost both the PNA and NAO into mid February which ended the snowy period and turned it into a gradient pattern with NNE snowy and lots of mixed crap SWFEs in our area including that one torch.

Anyway, here was the pattern overall for the entire met winter

Here was the pattern for the snowy part of January into early Feb

[snowNH]

There are sites that contain these indices (archived); I would start with the Climate Diagnostic Center (CDC). Will would be better to ask then me, but I believe the predominate signal was indeed the +PNA/-NAO, but it really didn't kick in meaningfully for us in terms of creating cold and snow locally until after X-Mass.

As far as "explaining" - not sure what you mean. If you are seeking a basic primer on NAO and PNA, just go to Google and type that in, and you'll be greeted by lots of reference material. Actually, Wikipedia undoubtedly has reams of info on atmosheric indices, but be careful with Wiki - it's refereeing on material isn't officiated.

Thanks Tip. It seems like you, will and the GFS are pegging the 3 week in November as our next possible snow threat, which isn't that far away.

[Typhoon Tip]

Thanks Tip. It seems like you, will and the GFS are pegging the 3 week in November as our next possible snow threat, which isn't that far away.

Yeah, Will's estimate and mine are probably off by all of 4 day for all intents and purposes, which falls squarely into the aspect of "noise" give or take.

I think the pattern turns cooler immediately post the D7 trough and then gains momentum nearing the 20th and beyond. Just not sure if it will be sustained and characterize the first half of winter type of thing, or will it be a 10 D stint with a couple of winter threats - then balms out just in time to ruin x-mass. lol.

[snowNH]

Yeah, Will's estimate and mine are probably off by all of 4 day for all intents and purposes, which falls squarely into the aspect of "noise" give or take.

I think the pattern turns cooler immediately post the D7 trough and then gains momentum nearing the 20th and beyond. Just not sure if it will be sustained and characterize the first half of winter type of thing, or will it be a 10 D stint with a couple of winter threats - then balms out just in time to ruin x-mass. lol.

I'm in San Diego from Dec 18 to 25, so it looks like I may have picked a good week to miss weather around here.

[weathafella]

Well the GFS beyond this week is not warm....in fact there are some very nice changes. Similar to the Euro there's a stab of cold for a couple days around d7 and that appears to set the table for greater cold in length and strength as we move forward. Iow....cold comes and goes but each time it comes it stays a bit linger and of course is stronger. Nice GFS run today.

Ensembles say not so fast op...we wait.

[Typhoon Tip]

The predominate signal was actually -PNA/-NAO last year but we did get a solid burst of a +PNA during about the Jan 14-Feb 5 period which sustained out cold/snowy regime when the NAO block broke down during the Archambault type Jan 12th event....we got lucky with a nice MJO wave robust in the 7,8,1 region and another temporary -NAO right before the Jan 27 event. Then we lost both the PNA and NAO into mid February which ended the snowy period and turned it into a gradient pattern with NNE snowy and lots of mixed crap SWFEs in our area including that one torch.

Anyway, here was the pattern overall for the entire met winter

...

Here was the pattern for the snowy part of January into early Feb

...

More than less what I was remembering... The +PNA last year being so well timed pretty much set up the dominant character of the winter with that 45 day siege of snow and cold. The -PNA seemed to be less effective at created positive departures, though did contain some.

[Typhoon Tip]

I'm in San Diego from Dec 18 to 25, so it looks like I may have picked a good week to miss weather around here.

Eh, that was joke -

[40/70 Benchmark]

Me thinks the table is set for a 2001 lite.

Interior rejoice.

[40/70 Benchmark]

John I think the Pacific is going to overwhelm the NAO signal at least the first 2-3 weeks...it may break down to the Atlantic by the end of the month though. A good example of a heavily -PNA and -NAO pattern is December 1996 and we torched in that pattern while the N plains and N rockies froze. I think this pattern isn't too dissimilar and might be quite similar on many levels. We may sneak some colder air in than what is advertised currently, I certainly won't disagree on that point, but I think the mean will be comfortably above average through about the 20th.

Beyond this is far enough out to see a big breakdown in the pattern and we could certainly freeze our butts off late in the month if the EPO goes nuts on us with a well placed NAO. So I wouldn't be confident in saying the month as a whole will be a torch, but the first 3 week look overall on the mild side to me.

Told ya that October event reminded me of something:

[40/70 Benchmark]

Get this pattern out of the way in Novie because the cp is screwed, regardless.

[Amped]

Get this pattern out of the way in Novie because the cp is screwed, regardless.

Agreed atlantic won early last year. The Nina -PDO look dominate this month on the GFS and Euro Runs.

[N. OF PIKE]

i find it interesting that john mentions the pna starts rising from day 7 (and that it's directional movement) rising (i infer from what he says) is just as important if not more so then wether it is (+) or - overall. so going from a -2.5 PNA to a -.5 PNA (Pna rising 1.5) combined with a -NAO would be somewhat compatable for a colder than normal pattern from 42 N and above. I would LOVE to see more mets discuss this on the general weather forum

this link really shows the PNA rising rapidly from day 7 onward.....so again it would seem rather key to me when discussing the end of the mid/end of the month pattern wether a CLEAR rising trend on the PNA 2 full numbers is a pretty strong signal that supports cold or wether the overall - or + number is more is much more important.

Will since you have a wealth of knowledge i would like to know if you have much info. regarding patterns rising from a heavily - pna to a neutral slightly negative pna. i.e if you could just look at periods where the PNA rose 2 numbers wether that combined with a -NAO is enough for cold pattern to "sneak in"

[CoastalWx]

The EC ensembles are getting there in the final 2-3 days of the forecast. They have a decent NAO black and the ridging in the NPAC looks better to me.

[CT Rain]

Get this pattern out of the way in Novie because the cp is screwed, regardless.

Agreed. This pattern is great in November. Sucks post dec-15.

[CoastalWx]

In response to John, the PNA I think rules the roost for the next 10-14. It goes down to almost 3SD in the negative territory on the EC ensembles and a healthy -PNA on the GEFS too. But, I think things may start to change as the big west trough retrogrades a bit and allows for some relaxation and even slight ridging. All the while the NAO tries to go negative and some cold leaks into the US. I still think it's going to take a while for it to really move east given the still -PNA.

[H2Otown_WX]

In response to John, the PNA I think rules the roost for the next 10-14. It goes down to almost 3SD in the negative territory on the EC ensembles and a healthy -PNA on the GEFS too. But, I think things may start to change as the big west trough retrogrades a bit and allows for some relaxation and even slight ridging. All the while the NAO tries to go negative and some cold leaks into the US. I still think it's going to take a while for it to really move east given the still -PNA.

Seems like the GFS just keeps backing off with the colder regime. In fact, the 18z run has a vortex up in AK at the end. Don't you think that realistically we'll probably have to wait until after 12/1 to get into a consistent cold pattern with snow threats? Not that there is anything wrong with that, it reminds me a lot of last winter.

[snowNH]

Seems like the GFS just keeps backing off with the colder regime. In fact, the 18z run has a vortex up in AK at the end. Don't you think that realistically we'll probably have to wait until after 12/1 to get into a consistent cold pattern with snow threats? Not that there is anything wrong with that, it reminds me a lot of last winter.

18z GFS is a 'litchfield' special. Although, I'm still liking a snow threat around 11/19-11/22

[Typhoon Tip]

Get this pattern out of the way in Novie because the cp is screwed, regardless.

I've been away the last couple of days so am not sure what you folks have covered...

Ray - this is almost a very typical Indian Summer scenario, perhaps a rather extreme version. Let's take a quick peek at the AMS Glossary of Met's definition of Indian Summer:

Indian summer—A period, in mid- or late autumn, of abnormally warm weather, generally clear skies, sunny but hazy days, and cool nights. In New England, at least one killing frost and preferably a substantial period of normally cool weather must precede this warm spell in order for it to be considered a true “Indian summer.” It does not occur every year, and in some years there may be two or three Indian summers. The term is most often heard in the northeastern United States, but its usage extends throughout English- speaking countries. It dates back at least to 1778, but its origin is not certain; the most probable suggestions relate it to the way that the American Indians availed themselves of this extra opportunity to increase their winter stores. The comparable period in Europe is termed the Old Wives' summer, and, poetically, may be referred to as halcyon days. In England, dependent upon dates of occurrence, such a period may be called St. Martin's summer, St. Luke's summer, and formerly All-hallown summer.

We had a period of really bizarre warmth in mid October. Temperature soared to the mid and even upper 80s across 2 to 3 days for much the region. I heard it espoused then that Indian Summer was upon us, and given to the definition(s) above, that warmth post the frosts around ~ the 10th of the month certainly qualifeis. The warmth we are seeing now, this week, does as well - perhaps as it is stated above, this is a multi-Indian Summer year.

The main reason to bring this up is because I thought it interesting. But also, one shouldn't be too surprised or put out by the occurrence (not that you are...) in general. I don't believe there is much statistical berring on the ensuing cold season, as to whether these intervals transpire or not.

[snowNH]

Tip how is late November looking? If you've looked at models already