Medium Range-Long Range thread

[NJwinter23]

But the problem I have is that all guidance shows this. It would have to be a total fail of guidance to lose this strong signal within 7-8 days. SOmething is clearly allowing for this to happen..maybe leftover junk in the west pac or something..I really don't know. I guess what I could see is a quicker demise to the +PNA...I mentioned it being possibly transient yesterday. It is perplexing, but tough to ignore right now.

 

^ This. Couldnt agree more, though I certainly understand where Adam is coming from.

[am19psu]

Why though? What is the forcing for this PNA signal? It's not the tropics, right?

 

P4: http://raleighwx.americanwx.com/MJO/MarchPhase4.gif

P5: http://raleighwx.americanwx.com/MJO/MarchPhase5500mbAnomalies.gif

 

AAM is pretty blah right now, so it's not that. In fact, we've even had -MT off the Himalayas, which should lead to more zonal flow across the Pacific.

 

The polar vortex is displaced over Siberia, so I get why that leads to -NAO when you couple it with the heat and momentum transport from the near coastal bombs, but that doesn't explain a +PNA.

 

I just don't get why the modeling is doing what it's doing. And if I don't get why the modeling is doing, or it's not doing what I think it should be doing, it gives me a lot pause in accepting its solutions, regardless if all of the guidance is in agreement.

[Rainshadow]

Why though? What is the forcing for this PNA signal? It's not the tropics, right?

 

P4: http://raleighwx.americanwx.com/MJO/MarchPhase4.gif

P5: http://raleighwx.americanwx.com/MJO/MarchPhase5500mbAnomalies.gif

 

AAM is pretty blah right now, so it's not that. In fact, we've even had -MT off the Himalayas, which should lead to more zonal flow across the Pacific.

 

The polar vortex is displaced over Siberia, so I get why that leads to -NAO when you couple it with the heat and momentum transport from the near coastal bombs, but that doesn't explain a +PNA.

 

I just don't get why the modeling is doing what it's doing. And if I don't get why the modeling is doing, or it's not doing what I think it should be doing, it gives me a lot pause in accepting its solutions, regardless if all of the guidance is in agreement.

It would be a pretty big modeling bust given how well the PNA is normally handled at this forecast juncture.  Maybe like Scott posted,  just transitory vs prolonged.

[NJwinter23]

Chris,

 

In actuality, the GEFS PNA skill scores have been higher than the NAO for the same time periods, so in theory the +PNA solution "should" have a greater chance of verifying than the -NAO.  The EPO is also outlooked to be positive (dont know its skill score), so there is a mixed message out there. But, just looking at the blocky 500mb flow, its going to be tough for lows to "cut" the next couple of weeks.

 

Hey Tony,

 

That is an interesting way to look at it, from a skill scores perspective. 

 

My curiosity was purely from a forcing perspective: Yes, the -NAO has been deceptive all season and most times has not occurred as modeled, but you can kind of make sense of it as we've gotten closer and have seen wave breaker after wave breaker off the Northeast coast among other factors. As far as the PNA though, many would agree the base state has been a -PNA due to the regime in place, and the various +PNA spikes of late can be traced back pretty well to the tropical forcing/AAM spikes. This spike as modeled doesnt readily appear to have a tracer, and in fact, the tracers argue for the opposite sign...hmmm

[NJwinter23]

Maybe it is a response to the whole train getting clogged up due to the atlantic blocking downstream, which seems to want to retrograde across Canada as the 1-2 week time frame goes on. Maybe this is overpowering the tropical pacific signal,  maybe the PNA is transient/ a couple of days like Scott has suggested (a lot of maybes there).. I would even go as far to interpret the gfs operational runs as suggesting that last part in the 11-15 day.

 

Looking at the height forecasts in the stratosphere, it actually looks well in support for the its PNA forecast. There is a negative height anomaly centered in the aleutians at 50mb by ~day 8.

[Rainshadow]

Hey Tony,

 

That is an interesting way to look at it, from a skill scores perspective. 

 

My curiosity was purely from a forcing perspective: Yes, the -NAO has been deceptive all season and most times has not occurred as modeled, but you can kind of make sense of it as we've gotten closer and have seen wave breaker after wave breaker off the Northeast coast among other factors. As far as the PNA though, many would agree the base state has been a -PNA due to the regime in place, and the various +PNA spikes of late can be traced back pretty well to the tropical forcing/AAM spikes. This spike as modeled doesnt readily appear to have a tracer, and in fact, the tracers argue for the opposite sign...hmmm

 

Maybe we are looking at this backwards. Could it be the forecast retrograding -nao ridge causes the flow to buckle which would then increase doubts?

[NJwinter23]

Maybe we are looking at this backwards. Could it be the forecast retrograding -nao ridge causes the flow to buckle which would then increase doubts?

 

Yeah that's what I was wondering too

[NaoPos]

I'm not buying the PNA scenario at all. I think it has to do with models doing a crummy job forecasting tropical convection. Look at this forecast from the Euro ensemble and tell me if it jives with the concepts laid out in this thread.

COuld this be a factor why? its @ the lower levels of the strat, so maybe it wouldn't take long for it to transfer? Or could it just be simple physics? With the PV strengthening on the other side of the globe, it allows for PNA to go positive to balance out ? (sinking air over there, equal and opposite reaction over here?) Just taking a stab here, so take it easy on me! lol :-)

[CoastalWx]

I agree Adam et al. I'm just as curious as you are. 

 

Sometimes this field is humbling..nice to see that happen once in a while when we all think we have it figured out.

[NaoPos]

This is a pretty intense pattern going forward:

[HM]

 

Oh yeah. I see how it played it now. But I definitely didn't back two weeks ago (or even a week ago), and HM was chirping as early as January about it not being a typical transition into a P3-P4-P5 +NAO regime.

 

 

I missed those posts....I'll have to go back and look. HM, what was your rationale if you don't mind. 

The -NAO prediction was based on a lag effect/feedback of what was happening in the previous weeks (cyclonic wave breaking e.g.) mixed with the time of year, AAM state and stratospheric setup. We were speculating as early as the start of the New Year about what would happen in mid-late Jan into Feb with the SSW/MJO. The biggest question then would be if it happened too soon or not; but, it seemed like it was going to lead to C.W.B. during a favorable time of year to have this -NAO form.

My wave timings are always cross-checked with analogs (e.g. certain circulations mid-winter favor certain circulations in March), AAM/forcing and the stratosphere. The wave/feedback/lag timings passed the test on all 3. For example, in early Jan we had a subtropical -AAM anomaly with a developing +AAM anomaly at the equator (MJO). Based on the expected MJO/SSW, I anticipated and predicted a poleward flux, leading to a 60N or so -AAM anomaly by mid Feb (favoring a -AO/NAO).

The NAO is never a linear process. It is always a feedback / lag thing mixed with the current conditions/time of year. If just 1 of these things is out of tune, the NAO process gets ruined.

[HM]

 

Why though? What is the forcing for this PNA signal? It's not the tropics, right?

 

P4: http://raleighwx.americanwx.com/MJO/MarchPhase4.gif

P5: http://raleighwx.americanwx.com/MJO/MarchPhase5500mbAnomalies.gif

 

AAM is pretty blah right now, so it's not that. In fact, we've even had -MT off the Himalayas, which should lead to more zonal flow across the Pacific.

 

The polar vortex is displaced over Siberia, so I get why that leads to -NAO when you couple it with the heat and momentum transport from the near coastal bombs, but that doesn't explain a +PNA.

 

I just don't get why the modeling is doing what it's doing. And if I don't get why the modeling is doing, or it's not doing what I think it should be doing, it gives me a lot pause in accepting its solutions, regardless if all of the guidance is in agreement.

It is interesting about phase 4 because if you go to April, you get this picture:

http://raleighwx.americanwx.com/MJO/AprilPhase4.gif

FMA temps:

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/Composites/Temperature/FMA/combined_image.png

I bring this up because our wavelengths are getting pretty spring-like, despite the calendar and this has to do with the AAM state / retreating AJ. This leaves us with -NAO anomalies and stale cold air of course but also shorter waves. Does this mean we can force a PNA response this way? Sort of like an early spring jet setup instead? Either way it's brief because once the "burp" is removed (hopefully with a huge storm in early March) I expect the wavelengths to elongate again +WPO/EPO style and broaden the warmth.

[HM]

 

Could this be a factor why? its @ the lower levels of the strat, so maybe it wouldn't take long for it to transfer? Or could it just be simple physics? With the PV strengthening on the other side of the globe, it allows for PNA to go positive to balance out ? (sinking air over there, equal and opposite reaction over here?) Just taking a stab here, so take it easy on me! lol :-)

 

It is part of the equation in a sense but we can't prove that it is directly related to the PNA. It could simply be the tropospheric N PAC low causing the ozone surplus in the lowest half of the strat and it alone is causing the downstream PNA ridging. This makes the strat sort of a red herring. I'm not saying that's the case, by the way, just saying that we can't say for sure one way or another at such short time scales.

I will say this though: we have had immediate bottom-up responses this year on the AO so it is quite possible this warming is helping with the PNA. Notice on the euro's potential vorticity maps that anticyclonic anomalies are being fluxed down the Rockies. Sure, it could be related to the models predicting a PNA ridge but it could also be the other way around too (the reason the PNA ridge sustains).

So, in short, I have no idea.

Let's put it this way: it's definitely not making things worse! There is no major stratospheric cooling reaching these levels to kick off March, which was something I was expecting to happen this year/why this wouldn't be 2012 all over again.

[am19psu]

 

It is interesting about phase 4 because if you go to April, you get this picture:

http://raleighwx.americanwx.com/MJO/AprilPhase4.gif

FMA temps:

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/Composites/Temperature/FMA/combined_image.png

I bring this up because our wavelengths are getting pretty spring-like, despite the calendar and this has to do with the AAM state / retreating AJ. This leaves us with -NAO anomalies and stale cold air of course but also shorter waves. Does this mean we can force a PNA response this way? Sort of like an early spring jet setup instead? Either way it's brief because once the "burp" is removed (hopefully with a huge storm in early March) I expect the wavelengths to elongate again +WPO/EPO style and broaden the warmth.

Is there a site with "wavelength anomalies?" I've noticed the wavelengths have been getting much shorter on the guidance, but I was strugging to understand why. It's not like we're in a true La Nina where the pole to equator temperature gradient is really weak.

[HM]

 

Is there a site with "wavelength anomalies?" I've noticed the wavelengths have been getting much shorter on the guidance, but I was strugging to understand why. It's not like we're in a true La Nina where the pole to equator temperature gradient is really weak.

 

Well, in the sense of what we are talking about, I don't think there is a website that exists. Of course, I'm at work now so I can't skim through my bookmarks. There are probably a lot of sites where you can infer or maybe use something else as a proxy. When I look over the maps, I see where the main NH Rossby Waves are setting up and what areas they have abandoned. That void area is usually cluttered with shorter waves. Between doing a hemispheric comparison and knowing generally what climo should be with our wave lengths, that's when I usually make a statement about them. I know, it's not quite scientific; but, it usually suffices for my needs. Although in this case, I'm not sure if that method would have had enough lead-time to be useful.

I've seen through the Albany sites/Mike's links etc. someone who develop "A.P.E" graphics which could help with equator-->pole gradients. But we are dealing with something subseasonal in a certain section of the hemisphere, so I have no idea if that will work. Also, I haven't used or work with these APE graphics so maybe Mike or someone can chime in about them.

[NJwinter23]

Is there a site with "wavelength anomalies?" I've noticed the wavelengths have been getting much shorter on the guidance, but I was strugging to understand why. It's not like we're in a true La Nina where the pole to equator temperature gradient is really weak.

 

My guess would be that it has something to do with the stratosphere vortex on the otherside of the NH and the cold air source/arctic jet retreating northward as a result.... Didn't think of the shorter spring-like wavelengths, that also makes a lot of sense.

[am19psu]

My guess would be that it has something to do with the stratosphere vortex on the otherside of the NH and the cold air source/arctic jet retreating northward as a result.... Didn't think of the shorter spring-like wavelengths, that also makes a lot of sense.

What is the physics between the polar vortex over Siberia and shorter wavelengths over here? I kinda feel stupid asking this.

[NJwinter23]

What is the physics between the polar vortex over Siberia and shorter wavelengths over here? I kinda feel stupid asking this.

 

Oh please, I don't even know if it is correct so no need to feel stupid... I'm interpreting it like it is Fall/spring month when you have less cold air in Canada/less of a temp gradient and you can get more closely spaced kinks/cutoffs in the jetsream, versus the broader scale ridges/troughs you get in the winter when there is a huge temp gradient.

 

And the connection I was making to the stratopshere is that when it shifts to the other side of the pole/siberia, so does the greatest cold air source, and were left with this kind of look

[CoastalWx]

Oh please, I don't even know if it is correct so no need to feel stupid... I'm interpreting it like it is Fall/spring month when you have less cold air in Canada/less of a temp gradient and you can get more closely spaced kinks/cutoffs in the jetsream, versus the broader scale ridges/troughs you get in the winter when there is a huge temp gradient.

 

And the connection I was making to the stratopshere is that when it shifts to the other side of the pole/siberia, so does the greatest cold air source

 

The wavelength deal and HMs bottom up energy transfer seem to be part of the reason why mother nature is saying eff you to the MJO composites. The signal also appears to get muddled as the dynamic models have been trending near the COD so where is the coherent wave to break up this pattern? Also, the Atlantic is killing it right now. Not often we can say this, but it's owning everything as far as our weather east of the Rockies.

 

I still think we may perhaps see the PNA break down a little quicker than modeled (I may be wrong), but perhaps not before the first 10 days at least are pretty cool across a good part of CONUS real estate.

[Mike.Ventrice]

  

Well, in the sense of what we are talking about, I don't think there is a website that exists. Of course, I'm at work now so I can't skim through my bookmarks. There are probably a lot of sites where you can infer or maybe use something else as a proxy. When I look over the maps, I see where the main NH Rossby Waves are setting up and what areas they have abandoned. That void area is usually cluttered with shorter waves. Between doing a hemispheric comparison and knowing generally what climo should be with our wave lengths, that's when I usually make a statement about them. I know, it's not quite scientific; but, it usually suffices for my needs. Although in this case, I'm not sure if that method would have had enough lead-time to be useful.

I've seen through the Albany sites/Mike's links etc. someone who develop "A.P.E" graphics which could help with equator-->pole gradients. But we are dealing with something subseasonal in a certain section of the hemisphere, so I have no idea if that will work. Also, I haven't used or work with these APE graphics so maybe Mike or someone can chime in about them.

 

Great stuff in here- thanks all! As for the ZAPE diagnostics (convective available potential energy), Jason Corderia is the expert with regards to this stuff. I haven't spun my head around it but it is basically a measure of the jets globally around the Northern Hemisphere. Pretty much the only thing Jay briefed me on is when there is a significant swing in ZAPE anomalies (from 1-2 sigma positive anomalies to 1-2 sigma negative anomalies), there is usaully a cold air out break over the Continental U.S.

 

I'm not sure about the other way around- negative to positive ZAPE means warmth? Something to ask Jay. His real-time diagnostics can be found at the following link:

http://jasoncordeira.weebly.com/atmospheric-energy.html

 

Currently, we are transitioning into a period consisting of positive ZAPE anomalies:

 

 

I presume this is a time where the mid-latitude N. Hem jets should be increasing in magintude, especially the North Pacific Jet. Most of March appears to be in the positive 2 sigma thereshold. Hopefully when his user guide becomes available, we can be sure what that exactly means. 

 

I have been meaning to write a discussion pertaining to the RMM and CCKWs- maybe I'll get around to it later tonight but if I don't, I'll post it sometime next week.

[am19psu]

Positive zape should also be correlated to longer wavelengths than usual, too

[Rainshadow]

Great stuff in here- thanks all! As for the ZAPE diagnostics (convective available potential energy), Jason Corderia is the expert with regards to this stuff. I haven't spun my head around it but it is basically a measure of the jets globally around the Northern Hemisphere. Pretty much the only thing Jay briefed me on is when there is a significant swing in ZAPE anomalies (from 1-2 sigma positive anomalies to 1-2 sigma negative anomalies), there is usaully a cold air out break over the Continental U.S.

 

I'm not sure about the other way around- negative to positive ZAPE means warmth? Something to ask Jay. His real-time diagnostics can be found at the following link:

http://jasoncordeira.weebly.com/atmospheric-energy.html

 

Currently, we are transitioning into a period consisting of positive ZAPE anomalies:

 

 

I presume this is a time where the mid-latitude N. Hem jets should be increasing in magintude, especially the North Pacific Jet. Most of March appears to be in the positive 2 sigma thereshold. Hopefully when his user guide becomes available, we can be sure what that exactly means. 

 

I have been meaning to write a discussion pertaining to the RMM and CCKWs- maybe I'll get around to it later tonight but if I don't, I'll post it sometime next week.

 

Mike,

 

Is the atmospheric normal zape on this graph around 4.5?

 

Orrrrr I could have just gone to the link and found out the SD(s) are shaded in blue and red. 

[jrodd321]

This is a pretty intense pattern going forward:

Dayum look at that blocking. Sexy. 

[tombo82685]

Dayum look at that blocking. Sexy. 

Like HM stated, after a while the cold air is going to get pretty stale. Theoretically with a block you are cutting off the cold air from entering the US. Combine early march with a stale airmass and it still may have issues for the coastal plain area and a good bit of this forum. Especially if the gfs is right and parks that low over the great lakes. That would almost seal it for not much snow.

[Allsnow]

I'm a bit confused. Seems like the sne and NYC forums are really liking the upcoming pattern for snow chances. Was reading that the gefs and euro ensembles are a weenies dream. That being said, does not seem like we have the same kind of vibe in here. Is this not the type of pattern that will produce for us? Do we have morch coming?

[jrodd321]

Like HM stated, after a while the cold air is going to get pretty stale. Theoretically with a block you are cutting off the cold air from entering the US. Combine early march with a stale airmass and it still may have issues for the coastal plain area and a good bit of this forum. Especially if the gfs is right and parks that low over the great lakes. That would almost seal it for not much snow.

Yea I know you're right man. Seeing that in mid January would have be nice, though.

[famartin]

I'm a bit confused. Seems like the sne and NYC forums are really liking the upcoming pattern for snow chances. Was reading that the gefs and euro ensembles are a weenies dream. That being said, does not seem like we have the same kind of vibe in here. Is this not the type of pattern that will produce for us? Do we have morch coming?

Cold air is marginal.  Enough for areas north of this area, even the Pocs and LV perhaps, but quite possibly not enough for the I-95 corridor in this subforum.

[Allsnow]

Cold air is marginal. Enough for areas north of this area, even the Pocs and LV perhaps, but quite possibly not enough for the I-95 corridor in this subforum.

Oh okay. Thanks ray

[NaoPos]

Cold air is marginal.  Enough for areas north of this area, even the Pocs and LV perhaps, but quite possibly not enough for the I-95 corridor in this subforum.

No real difference from any other time this winter :-)

@ this point, we're going to start to battle #climo, sun angle and all that good stuff, especially along the coastal event. MArginal set ups/weak coastals wont cut it. And like you have been saying, with the PV retreated to mother russia, our cold pool will be modifying.

[CoastalWx]

Too bad we can't see euro ZAPE. GFS tries to beat down the PNA and if I am interpreting this right..is probably why ZAPE goes positive.