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January Medium/Long Range Disco Thread

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3 minutes ago, WinterWxLuvr said:

That relationship is only a general guideline and if I’m not mistaken acts slightly differently in winter and summer. 

That's actually the part of meteorology that really interests me.  I find cyclogensis, precipitation, winds speeds, only mildly interesting, but I am fascinated by temperature.  Unfortunately there just isn't a whole lot of easily available information out there beyond the simplistic guidelines we have just been discussing.  I need to find a text book on "Atmospheric temperature patterns and 500 MB analysis".

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47 minutes ago, cbmclean said:

That's actually the part of meteorology that really interests me.  I find cyclogensis, precipitation, winds speeds, only mildly interesting, but I am fascinated by temperature.  Unfortunately there just isn't a whole lot of easily available information out there beyond the simplistic guidelines we have just been discussing.  I need to find a text book on "Atmospheric temperature patterns and 500 MB analysis".

Since I don't think it has been answered yet, the 500mb height is a function of the surface pressure and thickness (which is proportional to temperature averaged over the layer). So, BN heights can be the result of BN temperatures from the sfc to 500mb, BN surface pressure, or some combination. When the 500mb height is BN but sfc is AN, that tells me the sfc pressures are low and/or the sfc temp is higher than would be expected for a given thickness. This makes sense since Pacific maritime air masses have steeper lapse rates (warm sfc, cold aloft) than continental/arctic origin air (cold sfc, cold aloft). Think about it - air coming from the Pacific more or less assumes the SST after many days. There isn't enough time when these travel over North America to cool radiatively at the sfc. Also, the latent heat added from orographic precip over the Rockies actually results in a warming of these air masses (chinook effect). Contrast that with Arctic air masses - the cooling is strongest at the surface (surface radiates heat much more effectively than atmosphere), so these tend to have a strong inversion. Further, when you get an EPO ridge the cold air doesn't have to cross the Rockies, it comes down the eastern slope from the north so no latent heat gets added (not that there would be much considering how dry these air masses are).

Models are really good at moving air around - I'm not sure how well they represent the radiative heating/cooling though. It's pretty complex and depends on the surface properties, water vapor, etc. I remember reading a paper about the formation of deep cold air masses, and the authors found that you get "diamond dust" ice crystals - basically very light snow w/o clouds - forming below -40C (or something really cold), and these radiate heat more effectively than the air itself. At really long lead times if these processes are not represented properly it could result in a odd looking temperature for a given flow pattern. There are modeling experts on this forum who know way more than me (I'm from more of a radar/remote sensing background) , so I'm happy to be corrected.

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32 minutes ago, GEOS5ftw said:

Since I don't think it has been answered yet, the 500mb height is a function of the surface pressure and thickness (which is proportional to temperature averaged over the layer). So, BN heights can be the result of BN temperatures from the sfc to 500mb, BN surface pressure, or some combination. When the 500mb height is BN but sfc is AN, that tells me the sfc pressures are low and/or the sfc temp is higher than would be expected for a given thickness. This makes sense since Pacific maritime air masses have steeper lapse rates (warm sfc, cold aloft) than continental/arctic origin air (cold sfc, cold aloft). Think about it - air coming from the Pacific more or less assumes the SST after many days. There isn't enough time when these travel over North America to cool radiatively at the sfc. Also, the latent heat added from orographic precip over the Rockies actually results in a warming of these air masses (chinook effect). Contrast that with Arctic air masses - the cooling is strongest at the surface (surface radiates heat much more effectively than atmosphere), so these tend to have a strong inversion. Further, when you get an EPO ridge the cold air doesn't have to cross the Rockies, it comes down the eastern slope from the north so no latent heat gets added (not that there would be much considering how dry these air masses are).

Models are really good at moving air around - I'm not sure how well they represent the radiative heating/cooling though. It's pretty complex and depends on the surface properties, water vapor, etc. I remember reading a paper about the formation of deep cold air masses, and the authors found that you get "diamond dust" ice crystals - basically very light snow w/o clouds - forming below -40C (or something really cold), and these radiate heat more effectively than the air itself. At really long lead times if these processes are not represented properly it could result in a odd looking temperature for a given flow pattern. There are modeling experts on this forum who know way more than me (I'm from more of a radar/remote sensing background) , so I'm happy to be corrected.

Well I've certainly learned something this evening...especially the part about the Chinook effect...and why an EPO ridge is helpful (though I still need clarity on exactly what it is). Thanks for breaking that down! 

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36 minutes ago, GEOS5ftw said:

Since I don't think it has been answered yet, the 500mb height is a function of the surface pressure and thickness (which is proportional to temperature averaged over the layer). So, BN heights can be the result of BN temperatures from the sfc to 500mb, BN surface pressure, or some combination. When the 500mb height is BN but sfc is AN, that tells me the sfc pressures are low and/or the sfc temp is higher than would be expected for a given thickness. This makes sense since Pacific maritime air masses have steeper lapse rates (warm sfc, cold aloft) than continental/arctic origin air (cold sfc, cold aloft). Think about it - air coming from the Pacific more or less assumes the SST after many days. There isn't enough time when these travel over North America to cool radiatively at the sfc. Also, the latent heat added from orographic precip over the Rockies actually results in a warming of these air masses (chinook effect). Contrast that with Arctic air masses - the cooling is strongest at the surface (surface radiates heat much more effectively than atmosphere), so these tend to have a strong inversion. Further, when you get an EPO ridge the cold air doesn't have to cross the Rockies, it comes down the eastern slope from the north so no latent heat gets added (not that there would be much considering how dry these air masses are).

Models are really good at moving air around - I'm not sure how well they represent the radiative heating/cooling though. It's pretty complex and depends on the surface properties, water vapor, etc. I remember reading a paper about the formation of deep cold air masses, and the authors found that you get "diamond dust" ice crystals - basically very light snow w/o clouds - forming below -40C (or something really cold), and these radiate heat more effectively than the air itself. At really long lead times if these processes are not represented properly it could result in a odd looking temperature for a given flow pattern. There are modeling experts on this forum who know way more than me (I'm from more of a radar/remote sensing background) , so I'm happy to be corrected.

Thank you very much, GEOS5ftw, this is exactly the additional details that I have been looking for.  I am intensely interested in learning more about this.  If I was looking to invest some hobby money into technician literature about this topic, is there a term for this sub-specialty of meteorology?  I don't mean modeling.  I mean understanding why air masses obtain the temperature characteristics that they do, and how the get moved to different locations.  For example, what made the Feb 1899 airmass so cold in its source region, and how did it get unleashed into the lower 48 with so little attenuation?

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5 minutes ago, Maestrobjwa said:

and why an EPO ridge is helpful (though I still need clarity on exactly what it is)

I stole this graphic from the post that PSU made to start off the snow climo thread last year.  He has marked the EPO domain.  An EPO ridge is just AN 500 MB heights in the EPO region.

 

image.png.2804bd6061f4e6bb1f28a1d7eb93a0c0.png

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1 minute ago, cbmclean said:

I stole this graphic from the post that PSU made to start off the snow climo thread last year.  He has marked the EPO domain.  An EPO ridge is just AN 500 MB heights in the EPO region.

 

image.png.2804bd6061f4e6bb1f28a1d7eb93a0c0.png

Now on those maps you guys post...above normal heights are shown in red?

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Just now, Maestrobjwa said:

Now on those maps you guys post...above normal heights are shown in red?

I don't post many maps.  I am actually a novice myself, but I love to learn.  Yes on those 500 MB maps the AN anomalies are various shades of red.

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4 minutes ago, Maestrobjwa said:

Now on those maps you guys post...above normal heights are shown in red?

Yes...and this is what he was talking about. Get a ridge into the EPO (AK region) and it sends cold continental air down east of the Rockies into the central and eastern US. 
70028499-F2E0-4BAF-87C8-6848495D0C6E.jpeg.ac9fc0b03640d1a391f9ae4254f6ba1f.jpeg

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@WxUSAF tonight’s op gfs I think is more indicative of what the ensembles are “seeing” then the bootleg heights issue.  From 300-340 there is a full Rex block centered near the southern tip of Baffin with a 50/50 trapped doing loops under it. If anything that should be too much blocking. And yet it rains to Montreal during that period. There is no cold. The flow is blocked. The systems shear out. 
 

However...that is the first major longwave trough after the block retrogrades.  Imo, like you said, if the blocking persists I think each subsequent wave will likely have a bit more cold to work with. The euro weekly ensembles, however, never quite get to that critical tipping point where there is enough depth of cold to keep storms from either waiting and cutting or shearing out.  I agree that’s unlikely. But the gfs shows that it’s a “real” block...and still warm. 

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20 minutes ago, psuhoffman said:

@WxUSAF tonight’s op gfs I think is more indicative of what the ensembles are “seeing” then the bootleg heights issue.  From 300-340 there is a full Rex block centered near the southern tip of Baffin with a 50/50 trapped doing loops under it. If anything that should be too much blocking. And yet it rains to Montreal during that period. There is no cold. The flow is blocked. The systems shear out. 
 

However...that is the first major longwave trough after the block retrogrades.  Imo, like you said, if the blocking persists I think each subsequent wave will likely have a bit more cold to work with. The euro weekly ensembles, however, never quite get to that critical tipping point where there is enough depth of cold to keep storms from either waiting and cutting or shearing out.  I agree that’s unlikely. But the gfs shows that it’s a “real” block...and still warm. 

You have mentioned that you don't feel as if super cold cross-polar flow is in the cards this year.  What is your feeling about the feasibility of simply getting the Pacific to be mediocre enough to not overpower perfect NAO blocking?

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41 minutes ago, cbmclean said:

You have mentioned that you don't feel as if super cold cross-polar flow is in the cards this year.  What is your feeling about the feasibility of simply getting the Pacific to be mediocre enough to not overpower perfect NAO blocking?

I’m optimistic. We will see. 

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4 hours ago, cbmclean said:

You have mentioned that you don't feel as if super cold cross-polar flow is in the cards this year.  What is your feeling about the feasibility of simply getting the Pacific to be mediocre enough to not overpower perfect NAO blocking?

The LR ensembles are suggesting some improvement in the EPAC, with the trough weakening some/retrograding, and a developing EPO ridge. That would provide a mechanism to redirect the flow, and inject some colder air. This seems to be the way things are evolving, but it will likely take some time. I can see some folks getting impatient because there will likely be a favorable west-based block for a time, without necessarily seeing more favorable outcomes. The evolution of the SWE probably increases the uncertainty on ultimate longwave pattern evolution, and how much colder we get going forward. It appears that the -AO/NAO will have persistence, so that's one big box checked on the list for winter weather in this region.

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6 minutes ago, leesburg 04 said:

Anything before January 20th in our region will be gravy....after that I remain hopeful

January of which year? 2022?

I've never seen guidance track so many ull and surface lows to our South and yield rain to SE Canada during prime climo with such a distinct west-based NAO in my 30 years of tracking. New Englanders must be jumping from bridges. At least we are used to regularly failing down this way.

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3 minutes ago, Ralph Wiggum said:

January of which year? 2022?

I've never seen guidance track so many ull and surface lows to our South and yield rain to SE Canada during prime climo with such a distinct west-based NAO in my 30 years of tracking. New Englanders must be jumping from bridges. At least we are used to regularly failing down this way.

They're complaining pretty hard up there, lots of words like bootleg etc. Who knows....I guess we will see...it's almost Spring anyway

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7 hours ago, Amped said:

Maybe it'll trend east:weenie:

 

 

yeah it is disgusting over their.. I have been begging my wife to hop on a plane to portland and go to mount bachelor for the weekend.. but you know.. Corona.. 

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Extended GEFS has the look we need to flush the Pac puke and inject legit cold into our source region. Hopefully we get there, but it will take some time.

eta- h5 is actually much improved out west by mid Jan, but still relatively mild in the lower levels at that time.

1611360000-XjxCztUteI8.png

1611360000-WsGusV7lZL8.png

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We'll get something wintry with that GEFS look.  Won't likely be cold smoke but we don't see that much anyway.  couple of 1-3 or 2-4 inch slop fest events would do nicely.  

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Just now, BristowWx said:

We'll get something wintry with that GEFS look.  Won't likely be cold smoke but we don't see that much anyway.  couple of 1-3 or 2-4 inch slop fest events would do nicely.  

I would trade that look with a much more favorable Pac and less blocking for what the models are advertising over the next 10 days or so.

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