Late January - Early February Pattern Discussion

[Amped]

SE ridge is a nightmare. Probably above average temps February 2nd-6th time frame.

[mitchnick]

Nice overrunning look. 

 

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for rain, yes

[yoda]

Nice overrunning look.

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Yes it is if you like rain

[psuhoffman]

Agree. If by some chance the NAM is on to something for Wed and this thing moves NW it will prove it...if I were in S PA or N MD I would be more optimistic though...Westminister MD is the where I need to move

Yea I am frustrated up in central pa this year. My old location in md is over 30" now and I'm stuck at 15" and all from small fringe snows. I've managed to miss out in every direction and today's snow seems to be falling apart here also. Just not my year. I'm still paying for my 100" in 2010.

[BristowWx]

Yea I am frustrated up in central pa this year. My old location in md is over 30" now and I'm stuck at 15" and all from small fringe snows. I've managed to miss out in every direction and today's snow seems to be falling apart here also. Just not my year. I'm still paying for my 100" in 2010.

Not mine either...best snows have been just north of me in MD....this upcoming pattern looks to be a battle between the strong low in Canada and the SE ridge...you do get overrunning it's just what side you are on...shame with so much cold air around although I don't think the final chapter has been written on this

[vinylfreak89]

two things stick out to me about the NAM...

 

1) shortwave #2 is much faster dropping thru Canada in each successive run and also much stronger.

 

2) The SS energy fully phases as opposed to the GFS which leaves a piece behind.

 

The GFS also has that second shortwave, but evolves it in to the next vortex as opposed to trying to phase it with the develop storm over NE (extrapolating from 84 hour NAM).

 

Three key things to watch in the models:

 

1) Does the PV scoot northeast faster than currently indicated?

 

2) Does the SS energy phase in fully or does a piece get left behind?

 

3) How much separation is there (if any between the first and second polar shortwave)... the best case scenario for us is none... they phase early... if that happens... we have a KU on our hands... if it doesn't phase it acts like a kicker, and we have varying degrees of success depending on the first two factors.

 

This is not anywhere close to done evolving. Today's 12Z Euro will be very interesting to me, even though the Euro hasn't been stellar late

 

ETA: Just looked at the 00Z Euro. Its up to its old tricks of leaving energy behind in the SW so the trough ends up very progressive. Take away that bias and the 00z euro looks alot like the 12Z NAM

[Wonderdog]

The active "winter" pattern in Feb still shows up on the GFS just delayed by a couple of days. Cold air retreats then comes back. Had to happen some time. I like our chances of something significant occuring during pattern changes.

[dallen7908]

It'll be interesting to see if todays CPC 6/10 8/14 day outlook changes dramatically today (yes I know it is computer generated over the weekend). As of yesterday It called for below normal temperatures and above normal precipitation during the first week of February.  They used 15% 6z GFS, 30% 6Z ensembles, 15% Canadian 0z, and 40% 12z European ensembles. 

 

 

The NAEFS had colder than normal temperatures over the Great Lakes area and warmer than normal temperatures over the ATlantic.  We were in between. Perhaps a cutter look.  The NAEFS did have a strong signal for precipitation in the Feb 4-6 time frame. Temperatures during the Feb 4-6 time period were seasonal or slightly below. 

 

... and yes, last night's ECMWF run was a disaster, especially for the vast majority of our SE friends 

[Scraff]

Hearing EURO is whiff for VA north. Meh. Gimme the GFS happy hour run.

[clueless]

Who has Euro pls?

[lsukev]

The Euro is very little QPF anywhere it does precipitate, which is nowhere north of a southern South Carolina to New Orleans line.

 

ETA: Jacksonville jackpot

[Heisy]

No mention of west based block day 10 on EURO? 

[midatlanticweather]

The Euro is very little QPF anywhere it does precipitate, which is nowhere north of a southern South Carolina to New Orleans line.

 

ETA: Jacksonville jackpot

ARE YOU saying snow in Jacksonville FL? Whaaat

[ACFD FIREMAN]

Who has Euro pls?

Snowshowers tmrw late day.

 

Wed-Thur is OTS and not even close.

 

Next weekend a storm slides north thru N. PA...we warm and rain.

 

Bounday slips south after the storm passes north and there is precip along it scatttered about the south.

[Amped]

No mention of west based block day 10 on EURO? 

 

Yeah cause we have the 588dm contour in Jacksonville.   Probably a nice pattern for Detroit.

[Heisy]

Yeah cause we have the 588dm contour in Jacksonville.   Probably a nice pattern for Detroit.

 

You realize that with the block you'd likely see a nice reinforcing shot of cold air. 

[Heisy]

It looks like a better pattern for 40N, but still a long way out. 

[Bob Chill]

Yeah cause we have the 588dm contour in Jacksonville. Probably a nice pattern for Detroit.

Nothing is cutting into the compressed flow. Verbatim its a pretty big overrunning along the boundary signal. Expansive cold hp pushing down from canada. It's an interesting look nonetheless.

[Bob Chill]

Day 10 Pattern on the Euro...not a great pattern ICEZ

It's not great but it's a massive expanse of 1030-1040 cold hp stretched from western MT to upstate NY and it's pinned under the block. GEFS is pretty similar in its members d10-15. We could be rain, ice, or snow or all of the above. Who knows.

GEFS 5h means look pretty good d10-15. Any ridging off the coast or down around fl will be shortlived.

[clueless]

18z will be interesting. Maybe not so happy, though, for happy hour.

I am totally ok with the warm up. And it doesnt seem like it has legs if I am interpreting Euro comments correctly.

[ACFD FIREMAN]

It's not great but it's a massive expanse of 1030-1040 cold hp stretched from western MT to upstate NY and it's pinned under the block. GEFS is pretty similar in its members d10-15. We could be rain, ice, or snow or all of the above. Who knows.

GEFS 5h means look pretty good d10-15. Any ridging off the coast or down around fl will be shortlived.

Yeah I deleted my last post b/c I wasn't sure if I could post wxbell Euro images.

 

Anyway, there is cold air availble in those areas, but that SE ridge is pushing. You are right that it's interesting...maybe the ridge acts like a pump and opens up the Gulf and we are lucky to be on the right side ala 2003.

[Bob Chill]

Yeah I deleted my last post b/c I wasn't sure if I could post wxbell Euro images.

Anyway, there is cold air availble in those areas, but that SE ridge is pushing. You are right that it's interesting...maybe the ridge acts like a pump and opens up the Gulf and we are lucky to be on the right side ala 2003.

The idea is there on both models. Once the next cold push slides off the coast we're going to suck for a few days. I thought it would happen later (still might) but we need to get that out of the way either way. Personally, I think sooner is better for the sake of climo window. EPS and GEFS really bring back the cold sometime in d10-15. Builds in western canada and basically covers the whole country by the time it's done invading. It's not crazy cold like we've seen. Maybe in the upper midwest but not for the rest of us. One of the reasons I like the Euro is because it implies that a cold conus could potentially be pinned underneath the best blocking of the year. And with a less amplified flow, pac moisture and/or gulf moisture could be plentiful over time.

I have some good ideas about the AO for Feb that I'm going to post soon. I'm working on my thoughts and putting together some data. I think many will like the direction I'm going in.

[Amped]

Nothing is cutting into the compressed flow. Verbatim its a pretty big overrunning along the boundary signal. Expansive cold hp pushing down from canada. It's an interesting look nonetheless.

Thee 50/50 vortex  would have to retreat north before an all out cutter would occur  that pattern. Weed probably get an ice to rain storm out of it.   P09 and P10 match the EURO 240 if you want to extrapolate a forecast that's probably wrong to begin with.

http://www.meteo.psu.edu/~fxg1/ENSHGTWIDE_12z/ensloopwide.html

[Bob Chill]

I've been paying close attention to the AO index this year because as Wes has clearly explained and plotted in the past, it's the most important teleconnection for snow at our latitude. It's no coincidence that both of our January snows occurred during periods when the AO was negative. December still had snow but we were greatly helped by a combination of factors (most importantly a well placed -EPO ridge and PV to our North and on our side of the globe). December was a low probability snow period but we scored and it was awesome. January was a much higher probability (even with its flaws) and we scored again.

 

January is going to end up negative on the means for the AO. This goes against quite a bit of what was spoken about back in October with the SCI/OPI stuff. I'm not questioning the science of that research and analysis because there is a correlation. But it doesn't appear to be working out as absolute as many of us believed leading into December.

 

In my opinion, odds appear to favor a continued outright flip of the index for February. This is not a high confidence forecast by me at all. Just some thoughts I've been gathering since it started becoming clear that Jan would end up with a -AO as a whole.

 

November and December were very positive on the averages (2.029 and 1.475 respectively). The behavior of the AO went through a marked change right after its final peak around Christmas.

 

I have a financial risk background and we use trend channels all the time to mark performance and identify when resistance is broken (for better or worse) and then digging deep into why resistance was broken so changes can be made to underwriting. This has zero to do with weather teleconnections but I've always loved trend channels because they are handy for showing ideas.

 

Here's the upward AO trend channel for the period leading up to Christmas week. Pretty clear period of higher lows that never breached.

 

 

 

 

Here's the downward trend channel up through current. Pretty clear period of lower highs that never breached.

 

 

 

 

 

There are other years with anomalous +AO periods in November and December where there was an outright flip to an extended period of being negative.

 

Nov-March 1979-80

 

 

 

Nov-March 1982-83

 

 

 

 

Nov-March 1990-91

 

 

 

 

Nov-March 2004-05

 

 

 

 

What can we glean from this?

 

No two years are alike and even the years above have many differences as a whole to how this winter has played so far. I'm solely focusing on the AO index behavior. One thing that stands out (and we've spoke about this in years past) is that once the AO goes into a persistently negative state, the period typically lasts for 45 days or more. There are exceptions of course and I cherry picked the above data for support for this post. There are contrary cases and that's why this isn't a high confidence forecast. I'm just sharing my thoughts. 

 

Another thing is that February is a favored month for a -AO in the above cases. I didn't select these years for the month of Feb. I picked them for the fact that the AO flipped. Being negative in Feb was either a nice coincidence or there is some meaning to it. I personally have no idea the whys even if there is one. 

 

I can find contrary cases but the fact that the AO changed behavior back in December from near record high anomalous positive readings is noteworthy. And it has since taken on an overall negative state for January with only a very brief positive spell is more telling.  Now ensemble guidance is slowly becoming more bullish on a continued -AO for Feb.

 

If the 45+ period theory is correct in this case, it looks like the best starting period would be January 15th or so. That would take us through the end of February with a predominantly -AO. Again, this is not a high confidence forecast. Everything could go to hell in a handbasket. But for snow weenies, there is more than just blind hope that Feb produces. Only time will tell.

 

[mitchnick]

I've been paying close attention to the AO index this year because as Wes has clearly explained and plotted in the past, it's the most important teleconnection for snow at our latitude. It's no coincidence that both of our January snows occurred during periods when the AO was negative. December still had snow but we were greatly helped by a combination of factors (most importantly a well placed -EPO ridge and PV to our North and on our side of the globe). December was a low probability snow period but we scored and it was awesome. January was a much higher probability (even with its flaws) and we scored again.

 

January is going to end up negative on the means for the AO. This goes against quite a bit of what was spoken about back in October with the SCI/OPI stuff. I'm not questioning the science of that research and analysis because there is a correlation. But it doesn't appear to be working out as absolute as many of us believed leading into December.

 

In my opinion, odds appear to favor a continued outright flip of the index for February. This is not a high confidence forecast by me at all. Just some thoughts I've been gathering since it started becoming clear that Jan would end up with a -AO as a whole.

 

November and December were very positive on the averages (2.029 and 1.475 respectively). The behavior of the AO went through a marked change right after its final peak around Christmas.

 

I have a financial risk background and we use trend channels all the time to mark performance and identify when resistance is broken (for better or worse) and then digging deep into why resistance was broken so changes can be made to underwriting. This has zero to do with weather teleconnections but I've always loved trend channels because they are handy for showing ideas.

 

Here's the upward AO trend channel for the period leading up to Christmas week. Pretty clear period of higher lows that never breached.

 

13-14ao upward trend channel.JPG

 

 

 

Here's the downward trend channel up through current. Pretty clear period of lower highs that never breached.

 

13-14ao downward trend channel.jpg

 

 

 

 

There are other years with anomalous +AO periods in November and December where there was an outright flip to an extended period of being negative.

 

Nov-March 1979-80

 

Nov-March 79-80.JPG

 

 

Nov-March 1982-83

 

Nov-March 82-83.JPG

 

 

 

Nov-March 1990-91

 

Nov-March 90-91.JPG

 

 

 

Nov-March 2004-05

 

Nov-March 04-05.JPG

 

 

 

What can we glean from this?

 

No two years are alike and even the years above have many differences as a whole to how this winter has played so far. I'm solely focusing on the AO index behavior. One thing that stands out (and we've spoke about this in years past) is that once the AO goes into a persistently negative state, the period typically lasts for 45 days or more. There are exceptions of course and I cherry picked the above data for support for this post. There are contrary cases and that's why this isn't a high confidence forecast. I'm just sharing my thoughts. 

 

Another thing is that February is a favored month for a -AO in the above cases. I didn't select these years for the month of Feb. I picked them for the fact that the AO flipped. Being negative in Feb was either a nice coincidence or there is some meaning to it. I personally have no idea the whys even if there is one. 

 

I can find contrary cases but the fact that the AO changed behavior back in December from near record high anomalous positive readings is noteworthy. And it has since taken on an overall negative state for January with only a very brief positive spell is more telling.  Now ensemble guidance is slowly becoming more bullish on a continued -AO for Feb.

 

If the 45+ period theory is correct in this case, it looks like the best starting period would be January 15th or so. That would take us through the end of February with a predominantly -AO. Again, this is not a high confidence forecast. Everything could go to hell in a handbasket. But for snow weenies, there is more than just blind hope that Feb produces. Only time will tell.

well done Bob....82/83 had the mega NINO and 04/05 had a weak one

79/80 and 90/01 were technically neutral enso, but both were warm neutral

we remain a cool neutral...what does it all mean? idk, I just look at the CFS2 FEB forecasts twice a day and dream!

all kidding aside, nice job

[Scarlet Pimpernel]

I've been paying close attention to the AO index this year because as Wes has clearly explained and plotted in the past, it's the most important teleconnection for snow at our latitude. It's no coincidence that both of our January snows occurred during periods when the AO was negative. December still had snow but we were greatly helped by a combination of factors (most importantly a well placed -EPO ridge and PV to our North and on our side of the globe). December was a low probability snow period but we scored and it was awesome. January was a much higher probability (even with its flaws) and we scored again.

 

January is going to end up negative on the means for the AO. This goes against quite a bit of what was spoken about back in October with the SCI/OPI stuff. I'm not questioning the science of that research and analysis because there is a correlation. But it doesn't appear to be working out as absolute as many of us believed leading into December.

 

In my opinion, odds appear to favor a continued outright flip of the index for February. This is not a high confidence forecast by me at all. Just some thoughts I've been gathering since it started becoming clear that Jan would end up with a -AO as a whole.

------------------------------------------------

 

Bob...nice thoughts and analysis here on the AO.  I think you present some good stuff with the necessary caveats.  Long and the short of it, if I may condense things in this manner, we have good reason to be optimistic about February in terms of winter weather and snow opportunities.  That, despite what appears to be a few days of the pattern relaxing and warmer temperatures (along with rain) in the first few days of February.  I'll admit that the weenie in me rolled my eyes upon looking at the GFS out in that range, and got that sinking feeling!  But looking beyond that, and checking the ensemble mean (GEFS, at least), you can see we go back into a colder pattern.  It may not be the extreme cold that we just had, but we don't need single digits to score really well here.  And, if my eyes do not deceive me, it seems as if the GEFS (and GFS deterministic?) attempt to show signs of -NAO blocking.  It's done that before and it never materialized, so that remains to be seen, but I've heard you (and others) say the Euro ensembles have been kind of big on that too.  We'll see.

 

I've been checking out Don Sutherland's discussions now and then over in the general weather/forecasting forum, and he seems to have similar ideas concerning February...i.e., perhaps some kind of relaxation/warmup for a short time early in the month, but after that it looks like a good period to be optimistic.  He seemed on board for a colder than normal February.  At least, I hope I'm not mis-representing what he said!  That's the general gist that I got.

 

One thing that you don't mention...and I in no way am trying to denigrate the work you've shown, but just stating this to continue discussion...is that sometimes, a -AO does not translate to good -NAO blocking for us.  In fact, despite -AO periods this winter, we've utterly failed in that regard to get decent west-based blocking through Greenland.  If I recall correctly, the same kind of thing happened last year.  Now, maybe this will change heading into February, I am not sure (but I sure hope so!).  I know the AO/NAO are correlated, but not always one in the same and I'm not that knowledgeable enough to elaborate on the whys and wherefores.  But in reference to your comment that blocking tends to "like" February (with several periods of -AO occurring that month), I have read and heard that there could be some correlation to SSWs, though not certain of the extent.  I do know that SSWs tend to occur more in the mid-late winter and the stratospheric Arctic vortex tends to be more disturbed then with more wave activity, especially during the easterly phase of the QBO.

[Bob Chill]

AiZ,

I only have a couple thoughts on the nao. One is persistance. Haven't had it all year so I don't expect much. Another is that since the ao shares some domain space with the nao, having a decent -ao increases odds but no guarantees. Lastly, the nao is so much more volatile than the ao that lr forecasting or educated guessing is full of trouble.

On the flip side, EPS is showing some tendency for a -nao on the means. We can only hope.

Big storms require a -nao more often than than not but we've had plenty of snow with a -ao and neutral or positive nao.

[usedtobe]

AiZ,

I only have a couple thoughts on the nao. One is persistance. Haven't had it all year so I don't expect much. Another is that since the ao shares some domain space with the nao, having a decent -ao increases odds but no guarantees. Lastly, the nao is so much more volatile than the ao that lr forecasting or educated guessing is full of trouble.

On the flip side, EPS is showing some tendency for a -nao on the means. We can only hope.

Big storms require a -nao more often than than not but we've had plenty of snow with a -ao and neutral or positive nao.

Plus for our moderate 4" inch or more snow chances the AO is a little more important than the NAO.

[psuhoffman]

It's not great but it's a massive expanse of 1030-1040 cold hp stretched from western MT to upstate NY and it's pinned under the block. GEFS is pretty similar in its members d10-15. We could be rain, ice, or snow or all of the above. Who knows.

GEFS 5h means look pretty good d10-15. Any ridging off the coast or down around fl will be shortlived.

If and that's a big if, the idea is right the lower levels will trend colder as we approach. South of 40 not all the waves will be snow but some should or parts of some. It's not a bad pattern but true it's better the further north you go.

[Scarlet Pimpernel]

AiZ,

I only have a couple thoughts on the nao. One is persistance. Haven't had it all year so I don't expect much. Another is that since the ao shares some domain space with the nao, having a decent -ao increases odds but no guarantees. Lastly, the nao is so much more volatile than the ao that lr forecasting or educated guessing is full of trouble.

On the flip side, EPS is showing some tendency for a -nao on the means. We can only hope.

Big storms require a -nao more often than than not but we've had plenty of snow with a -ao and neutral or positive nao.

 

 

Plus for our moderate 4" inch or more snow chances the AO is a little more important than the NAO.

 

Bob...Thanks for the feedback and continuation of that discussion...good points.  It is very true the NAO is far more variable than the AO, and forecasting that for any length is difficult.  Likewise, the point that having a -AO surely increases the chance of a -NAO, but no guarantee there.  As you said, we certainly can score with at least a neutral NAO if we keep the AO negative (even if not a "big" event).  It would be nice if the (model) hints of a possible -NAO in the offing are on the correct track.

 

Wes...Interesting, I did not realize that for "moderate" level events, the AO phase is more important, but upon considering it for awhile, kind of makes sense.