January Storm Potentials

[HM]

Well, the data has come around to a less than ideal solution for snow lovers this weekend. However, I don't think we can quietly exit this cold pattern without something. Throwing out the model runs for a second, which do in fact show a storm around Christmas, I wanted to talk about why this period is trouble. Looking at things objectively, the one thing missing from this weekend's potential was the MJO factor. But what do I mean by that? Well, it doesn't have to mean a healthy octant 7-8-1 progression with an amplitude greater than 2. It can also mean how the global Walker Circulations are pulsing, which I'll discuss in a second.

We are about to see a few things time out in an interesting way:

1. A slow moving, retrograding block across Canada.

2. A parade of Pacific storms continuing with ample moisture

3. A development of a 50-50 low feature from Sunday's nor'easter

4. A MJO pulse across South America--perhaps low-frequency--but none-the-less, a pulse...

The first 3 points you can make out simply by looking at computer models and I'll save us all the global wind talk... but they do in fact look perfect for what's going on. The last time we had this GWO/MJO progression was back in late October/early November (positive tendency in a low AAM state). During that time, something similar happened where a West and East Coast trough went up but a ridge was squeezed out in between. This lead to a cold start to November in the East and even a nor'easter with early season cold/snow. While things are different, now that it's December, there are subtle clues that may suggest why the pattern may end up being similar anyway.

What we are going to focus on during this period, roughly anytime between Christmas and New Years, is the wavelengths. They are going to get much shorter than normal due to points 1, 3 and 4. This will allow the waves to act more autumn-like but with winter-like temperatures in place. This right here is a major signal for something to go down along the East Coast. It may or may not be the Christmas event but it could very well be one of the waves after that. It all depends on when the 50-50 lifts out and the rex block finally gets absorbed into the jet from Canada. If the clipper early next week aids in 50-50 growth but it is too slow to progress out, the Christmas wave will get redirected or squashed. If the 50-50 can get out of the way, I think that despite the poor placement of the CONUS ridge again, the MJO pulse would help out with the SE ridge from the added uplift from South America aiding in subsidence across the Horse Latitudes across Central America/Atlantic. This has been happening now and should stay heightened through New Years, before subsiding.

[HM]

By pulse, I just mean that the ENSO-aided forcing weakens a bit and the Atlantic side is a bit stronger. Yes, it doesn't show up well on orbit graphs but it's the best we can do in a strong La Niña. The reason I'm not getting cute with dates this year is because I honestly don't know. I just didn't get anything long range-wise worthy of mentioning and even today I still don't feel confident about anything for the rest of the month. The point of this post was to bring up that we may have trouble as this block gets absorbed.

But trouble may just be a regular winter storm and not a KU.

The MJO wave / forcing in the IO/Indonesia has weakened and this will allow other uplift centers across the Tropics to have some control on the state of the global winds/circulation.

[am19psu]

Thanks for the heads up, HM. The subtly of your analysis is the most amazing thing, to me.

[HM]

Now when this same thing happened in November, a s/w came east, much like the models have as we near Christmas, behind the big low near the East.

But because it was early November and the cutoff decides not to move, the s/w meant nothing. In late December, the 50-50 low will move and the flow will be a lot like this was. The idea of something cutting east under the block is definitely supported by the tropical parameters.

[HM]

Thanks for the heads up, HM. The subtly of your analysis is the most amazing thing, to me.

Thanks man...it is quite possible that this is a wasted pulse/weakened ENSO-forcing state and we just calmly go into a more zonal state in January. But according to the tropical side of things, we have through the end of the year before La Niña gets another shot at fighting back.

And without a summertime ridge over Greenland to fight back, it may mean your typical January response.

[am19psu]

Thanks man...it is quite possible that this is a wasted pulse/weakened ENSO-forcing state and we just calmly go into a more zonal state in January. But according to the tropical side of things, we have through the end of the year before La Niña gets another shot at fighting back.

And without a summertime ridge over Greenland to fight back, it may mean your typical January response.

I'm sure I'm reading too much into your post, but with the 3-4-5-6 progression, are you surprised about the state of blocking from Dec 5ish through now? I busted hard on my Dec forecast, and I still don't entirely understand why.

[snowfallower]

Thanks man...it is quite possible that this is a wasted pulse/weakened ENSO-forcing state and we just calmly go into a more zonal state in January. But according to the tropical side of things, we have through the end of the year before La Niña gets another shot at fighting back.

And without a summertime ridge over Greenland to fight back, it may mean your typical January response.

Thanks HM for giving us some hope for snow. So far in NEPA this has been a waste of cold air.I think you said a while back that week 3 in January could be wintry and I was just wondering if that is still valid. I always enjoy reading your posts.

[wxmx]

By pulse, I just mean that the ENSO-aided forcing weakens a bit and the Atlantic side is a bit stronger. Yes, it doesn't show up well on orbit graphs but it's the best we can do in a strong La Niña. The reason I'm not getting cute with dates this year is because I honestly don't know. I just didn't get anything long range-wise worthy of mentioning and even today I still don't feel confident about anything for the rest of the month. The point of this post was to bring up that we may have trouble as this block gets absorbed.

But trouble may just be a regular winter storm and not a KU.

The MJO wave / forcing in the IO/Indonesia has weakened and this will allow other uplift centers across the Tropics to have some control on the state of the global winds/circulation.

It looks like we are looking at the same things HM. I made a case for some wintry period possible in the S Plains in the TX thread in the Central/W States regional forums, and gave about the same date periodsand the same reasons (or I think I did) that you did. It's relieving to have some HM support here

[NinjaWarrior2]

I think that from now until Early to Mid January is our time before a more Zonal/Ridge pattern takes control. Although we have been in a decently low -NAO/-AO pattern lately, although I dont think it will help that much.

[Srain]

Great information HM, and you are correct Jorge. You spelled out a lot of the same data in the TX/MX thread yesterday. Great minds think alike.

[usedtobe]

I hadn't looked at the mjo and your analysis of it is beyond what I can do anyway. Like the coming set up the most of any so far. The dec 19 threat was always a low end threat as the pattern was less than optimal with some many moving parts and the ridging to the west of the shortwave being so weak. xmas threat is a more interesting one. This is the 1st time this year that the CPC supersensemble analogs have shown the potential for a KU storm. The D+8 spit out Dec 1966 and dec 1969. As you know but others might not, the analogs are determined by taking the a 5 day mean of the 500h pattern centered on the middle day of the pattern. The D+11 also shows new years eve 1970 another 4 inch storm for dca.

[mahk_webstah]

Thanks man...it is quite possible that this is a wasted pulse/weakened ENSO-forcing state and we just calmly go into a more zonal state in January. But according to the tropical side of things, we have through the end of the year before La Niña gets another shot at fighting back.

And without a summertime ridge over Greenland to fight back, it may mean your typical January response.

Thanks HM...I agree with AM about the subtlety thing. It is nice to hear good news from the Pacific side of things, and I think up here in New England we need something to shift to get us snow. The pattern has produced either cuts (pun intended) or suppressed OTS solutions. If we get our usual snow cover laid down then perhaps we do quite well in January if the typical La Nina gradient sets up. I am north of Concord NH and we do pretty well in that set up while my friends in the MA and SNE suffer.

As wonderful as the blocking looks I wouldn't mind seeing it disappear or weaken for a bit. If the Pacific shifts and we get weakened or further east NAOs we do well here at least I think so.

[HM]

I'm sure I'm reading too much into your post, but with the 3-4-5-6 progression, are you surprised about the state of blocking from Dec 5ish through now? I busted hard on my Dec forecast, and I still don't entirely understand why.

I was planing on evaluating the state of the blocking after it was over and writing up a post about it when the pattern settles down. A few things that come to mind are (but nothing certain yet):

1. The state of the October cryosphere / -AO development

2. The state of the low solar impact. As the solar parameters subsided from October's burst, the AO/NAO got increasingly negative

3. The state of the ozone, which became quite above normal

4. The favorable MJO/forcing/AAM that jump started the buckling. (notice the beautiful poleward propagation of the -dAAM/dT anomalies from Late Nov-early Dec which jump-started the -EPO which feeds the -NAO)

5. Oceanic feedbacks with the SST / tropics.

Right now, I feel that the combination of everything is what made this special but it was point 4 that got things going. Point 4 doesn't explain why it was so massive but it explains why it got going in the first place. I'll look into it more in January and write something up.

[WhiteoutWX]

I was planing on evaluating the state of the blocking after it was over and writing up a post about it when the pattern settles down. A few things that come to mind are (but nothing certain yet):

1. The state of the October cryosphere / -AO development

2. The state of the low solar impact. As the solar parameters subsided from October's burst, the AO/NAO got increasingly negative

3. The state of the ozone, which became quite above normal

4. The favorable MJO/forcing/AAM that jump started the buckling. (notice the beautiful poleward propagation of the -dAAM/dT anomalies from Late Nov-early Dec which jump-started the -EPO which feeds the -NAO)

5. Oceanic feedbacks with the SST / tropics.

Right now, I feel that the combination of everything is what made this special but it was point 4 that got things going. Point 4 doesn't explain why it was so massive but it explains why it got going in the first place. I'll look into it more in January and write something up.

Could the North Atlantic SST's have anything to do with it. Ive heard multiple times that we have a favorable "tripole" anomaly helping to sustain the current period of blocking. I have no idea about this type of stuff, but what are your thoughts?

[HM]

Could the North Atlantic SST's have anything to do with it. Ive heard multiple times that we have a favorable "tripole" anomaly helping to sustain the current period of blocking. I have no idea about this type of stuff, but what are your thoughts?

Well, I'll definitely look into this more once the blocking is over but I would have to say that we shouldn't confuse long term/climatic factors with our day-to-day NAO. For example, you can't blame why this particular block was so strong because of the tripole. All the tripole suggests is that you are in a certain phase of the AMO/NAO and that's it. It could be a footprint more than an initiator. Having that said, a more conducive environment definitely helps and can aid in making something stronger as long as all the other factors say it is a go.

The cyclonic wave breakers that had an equatorial propagation in late Nov-early Dec were conveniently placed with the SST tripole. But they also weren't there during more positive NAO times but the tripole was still there. Therefore, we cannot equate the two on this timescale.

[HM]

Thanks HM for giving us some hope for snow. So far in NEPA this has been a waste of cold air.I think you said a while back that week 3 in January could be wintry and I was just wondering if that is still valid. I always enjoy reading your posts.

Yes the end of December and sometime in January in the second half will be snowier times for you. In January, a classic gradient in snowfall departures may setup across New England/N. Mid Atlantic, and you would likely be on the positive side. The cold shot looks like it would start out west though and ultimately build east, akin to late Nov/early December. I don't think the NAO will cooperate as well as it did with the December shift; however, I don't think it will be positive either at the end of January. It may be more negative on the CPC calculation given the expected h5 heights at that time. February still looks warm overall; but as many here pointed out, changes late in the month into March seem probable.

[HM]

I think that from now until Early to Mid January is our time before a more Zonal/Ridge pattern takes control. Although we have been in a decently low -NAO/-AO pattern lately, although I dont think it will help that much.

Don't get too hung up on the past...although I'm about to contradict that statement. So, aah, I mean...don't get too hung up on how anomalous this -NAO has been. Go with climo of -NAO blocks and the modeling, which supports the climo. All of which suggest this pattern breaks down as we enter January. Once the block is no longer in place, it is going to be hard to keep this pattern going with the way the Pacific flow looks.

That's okay, we need a break!

[HM]

It looks like we are looking at the same things HM. I made a case for some wintry period possible in the S Plains in the TX thread in the Central/W States regional forums, and gave about the same date periodsand the same reasons (or I think I did) that you did. It's relieving to have some HM support here

Great information HM, and you are correct Jorge. You spelled out a lot of the same data in the TX/MX thread yesterday. Great minds think alike.

You see, this is one of the drawbacks to subforums. To be honest, I am not going to check a TX thread!

Anyone notice the 12/17 MJO sneak into phase 7?

[HM]

I hadn't looked at the mjo and your analysis of it is beyond what I can do anyway. Like the coming set up the most of any so far. The dec 19 threat was always a low end threat as the pattern was less than optimal with some many moving parts and the ridging to the west of the shortwave being so weak. xmas threat is a more interesting one. This is the 1st time this year that the CPC supersensemble analogs have shown the potential for a KU storm. The D+8 spit out Dec 1966 and dec 1969. As you know but others might not, the analogs are determined by taking the a 5 day mean of the 500h pattern centered on the middle day of the pattern. The D+11 also shows new years eve 1970 another 4 inch storm for dca.

Yes, it is encouraging to see more analogs show up for something appreciable. I could also see this wave turning into more of a quick-hitting suppressed wave or new england event, but something that goes on to strengthen the 50-50 low feature. I am kind of hoping that happens because I think the storm after that one would be the bigger event.

The 12z ECMWF ensemble mean post Christmas looks classic to me as well as the MJO parameters. I'll take classic and MJO over anything this weekend has going for it ANY DAY.

[HM]

Thanks HM...I agree with AM about the subtlety thing. It is nice to hear good news from the Pacific side of things, and I think up here in New England we need something to shift to get us snow. The pattern has produced either cuts (pun intended) or suppressed OTS solutions. If we get our usual snow cover laid down then perhaps we do quite well in January if the typical La Nina gradient sets up. I am north of Concord NH and we do pretty well in that set up while my friends in the MA and SNE suffer.

As wonderful as the blocking looks I wouldn't mind seeing it disappear or weaken for a bit. If the Pacific shifts and we get weakened or further east NAOs we do well here at least I think so.

Yes you will probably do better in January than most.

[usedtobe]

Yes, it is encouraging to see more analogs show up for something appreciable. I could also see this wave turning into more of a quick-hitting suppressed wave or new england event, but something that goes on to strengthen the 50-50 low feature. I am kind of hoping that happens because I think the storm after that one would be the bigger event.

The 12z ECMWF ensemble mean post Christmas looks classic to me as well as the MJO parameters. I'll take classic and MJO over anything this weekend has going for it ANY DAY.

I think the odds of snow are much better for xmas than they for tomorrow. I'm getting the feeling that any storm near the 1st will slam the door for awhile and that the pattern may try to break as suggested by Don, I think he's goign for slightly later but the model's are starting to show that look.

[HM]

I think the odds of snow are much better for xmas than they for tomorrow. I'm getting the feeling that any storm near the 1st will slam the door for awhile and that the pattern may try to break as suggested by Don, I think he's goign for slightly later but the model's are starting to show that look.

Well that goes without saying Wes, lol. (I'm just messing with you).

The question is: which one will be the Heather A. / end of pattern storm? Will it be Christmas or the next wave...or even the next wave?

[tacoman25]

I was planing on evaluating the state of the blocking after it was over and writing up a post about it when the pattern settles down. A few things that come to mind are (but nothing certain yet):

1. The state of the October cryosphere / -AO development

2. The state of the low solar impact. As the solar parameters subsided from October's burst, the AO/NAO got increasingly negative

3. The state of the ozone, which became quite above normal

4. The favorable MJO/forcing/AAM that jump started the buckling. (notice the beautiful poleward propagation of the -dAAM/dT anomalies from Late Nov-early Dec which jump-started the -EPO which feeds the -NAO)

5. Oceanic feedbacks with the SST / tropics.

Right now, I feel that the combination of everything is what made this special but it was point 4 that got things going. Point 4 doesn't explain why it was so massive but it explains why it got going in the first place. I'll look into it more in January and write something up.

A valiant effort to explain what's going on, HM...but I would have to think that most of those reasons given are probably not the main factor. Why? Because we saw the same extreme blocking occur last winter as well - with an opposite ENSO signal, no less. Unless there is something larger at work here, what are the odds that back to back winters would have record-setting blocking like this?

[HM]

A valiant effort to explain what's going on, HM...but I would have to think that most of those reasons given are probably not the main factor. Why? Because we saw the same extreme blocking occur last winter as well - with an opposite ENSO signal, no less. Unless there is something larger at work here, what are the odds that back to back winters would have record-setting blocking like this?

Well, I can't get too analytical right now because I'm really under the gun here. But for all I know all these signals mean squat. However, how different are they from last year?

The prevailing circumstances this year and last year are:

1. The weak solar factor

2. The presence of ozone

3. The presence of upwelling waves from Asia, aided by snow cover but also by general circulation.

4. The tripole/-PDO/+AMO oceanic circulations etc.

Despite different ENSO regimes and forcing, you can get buckling of the flow different ways. Forcing in one location can mean something quite different in the autumn vs. the winter. So even though the forcing was entirely different last year, it was once again favorable for the Atlantic response in November because of the Pacific response. I think once you get the ball rolling with the NAO, it's easy to keep it going. It is the "getting it started" part that is the most trouble...well at least it used to be!

Thanks for the post tacoman. At some point, I'll write something when it's over. Maybe during the thaw!

[Srain]

You see, this is one of the drawbacks to subforums. To be honest, I am not going to check a TX thread!

Anyone notice the 12/17 MJO sneak into phase 7?

And we wouldn't blame you for not visiting. Caught that phase 7 this morning.

[Typhoon Tip]

HM,

I agree - great minds think alike. I wrote a similar discussion in the New England thread specifically designed for them, but I see no reason to limit the potential at large to that region of the country.

John

[donsutherland1]

A valiant effort to explain what's going on, HM...but I would have to think that most of those reasons given are probably not the main factor. Why? Because we saw the same extreme blocking occur last winter as well - with an opposite ENSO signal, no less. Unless there is something larger at work here, what are the odds that back to back winters would have record-setting blocking like this?

FWIW, there are one or two cases where extreme blocks occurred in consecutive winters.

1968-69

1969-70 (March '70 was when the extreme block occurred)

Both occurred during meteorological winter:

1976-77

1977-78

Also, I suspect that there is a longer-term AO cycle and that the cycle had peaked in the recently and is now trending lower.

[NJwinter23]

Interesting post as always HM. Definitely going to have much more of a ridge out west to work with for the Christmas threat. However, the pesky trough crashing onto the west coast, and the ridge axis shifting east over Montana instead of Boise Idaho around storm day is concerning that this will all come together too far east once again. Or is this where the shorter wavelengths that HM mentioned can come into play and still work out for an east coast storm?

[tacoman25]

FWIW, there are one or two cases where extreme blocks occurred in consecutive winters.

1968-69

1969-70 (March '70 was when the extreme block occurred)

Both occurred during meteorological winter:

1976-77

1977-78

Also, I suspect that there is a longer-term AO cycle and that the cycle had peaked in the recently and is now trending lower.

Yes, that is true, it has happened before (though I would say the blocking this past winter and this winter so far is more impressive overall). But all of those winters were weak/moderate El Ninos.

[HM]

HM,

I agree - great minds think alike. I wrote a similar discussion in the New England thread specifically designed for them, but I see no reason to limit the potential at large to that region of the country.

John

My mind isn't that great