Re: Long Range Thread 12.0

[sroc4]

I can't answer for Tom, Scott, but if you look at 2M or 850mb temps there actually is decent cold penetrating across the country the first half of December. It's a fast flow, but I'm thinking the high heights associated with the -EPO entering the Arctic help bring some of that cold air down. So while it may he cold, it looks pretty dry and if there is a storm I fear it will take an unfavorable track due to the ugly looking aforementioned signals.

Ahh I am finally back from vacation.  Ive been in Chicago and Indiana for the past 8 days with the family.  It was nice to actually wake up in my own bed this morning.  

Anyway I totally see what your saying Frank.  There is no doubt that the most likely scenario between now and the first week of Dec has any energy coming out of the N most likely phasing with S energy early forcing a storm track well west with warm temps out ahead.  The system, for instance, coming through this upcoming week is a great example.


 




But just as this system lifts out at the same time a piece breaks off and backs into the SW once again to reinforce the -PNA.  I guess my question was/is why the reinforced persistant -PNA?  The trough in the SW CONUS has been one that has remained a constant since early November.  This was a quote from my write up on Oct 29th:

"That trough sitting off the NW Coast MUST leave for the fundamental pattern change to occur because it leads to a warm source region that floods the nation with Pac air."
https://www.njstrongweatherforum.com/t745-fundamental-pattern-change-on-the-wind

Now as we head deeper into the winter season climo changes so the intensity of the ridge ahead of it has become somewhat muted relative to a month ago, but the point being that it persists none the less.  And I believe it is a direct result of the Nina forcing's that have been present is some fashion since the beginning of Sept as seen by the OLR anomaly maps.

Mod MJO pulses running through phases 8, 1, and 2 throughout the later 2/3rds of Nov, combined with the -NAO and -AO, are responsible for our normal to below normal temp anomalies to this point, and likely was the reason our brothers and sisters to the NW were able to squeak out their first measurable snowfall of the season.  Without these factors the -PNA would have likely allowed the SE ridging to dominate and we could have had a miserably warm Nov temp wise.  

So now we see in the Md/LR the -EPO to start showing up, but at the same time the -NAO/-AO begin to get muted.  The -PNA looks to remain unchanged however, and the MJO is looking a little incoherent at the moment but I'm concerned it comes out in 3-6 yet again as we head into Dec.  Well see about that.  



My concern is that the forecasted -EPO will not evolve as it may appear on LR modeling, because that always seems to be the case when looking at LR modeling.  However, there is hope regarding that.  When looking at the SSTA maps there has been significant warming going on in the region where the cold pool is over the last 7-14days as well as warming in the GOA  



Recall this:  The SSTA as of Nov 12th

 

Now look at the curent SSTA:



The reason this may be significant is the strongest SST gradient may shift now from the N Central Pac like it has been, to the NE Pac now enhancing the -EPO ridge formation(A more classic +PDO setup) making the -EPO an actual real LR projection, rather than a fantasy LR projection.  We shall see though.  I am still skeptical, but if true the invasion of the Siberian/arctic air masses into NA, beginning with Canada and the Western CONUS will commence as we head into the first week of Dec.  

Wild Cards: We will have to see how the MJO behaves and how the Nina forcings behave as they could be factors that mute the potential pole ward -EPO blocking influences esp if they work together.   In addition a "west based" -EPO may play a role in keeping the coldest air in the west.  The stratosphere may play a role beyond day 10, however, its influences will likely not be known for some time.  There will likely not be any major changes to the strat and its influences on us for at least the next 10days.

[Frank_Wx]

The cold air will bleed east, but it's going to modify as it does so. The pattern continues to look fairly so so as of this morning. We'll get colder but nothing excites me in terms of seeing snow.

[algae888]

frank and scott help me understand this if you can. everywhere I read people are saying we have a -pna however nws shows pna has been + to neutral since late September? so which is right?

[algae888]

also can there be a persistent trough out west with a neutral to + pna?

[Frank_Wx]

frank and scott help me understand this if you can. everywhere I read people are saying we have a -pna however nws shows pna has been + to neutral since late September? so which is right?

also can there be a persistent trough out west with a neutral to + pna?

These can kinda be answered together. Those oscillation graphics produced by the NWS do not do a great job in sensing or measuring wavelengths over a given area. They are also based off the GFS, a statistically poor model when it comes to oscillation forecasting. Here is the PNA forecast from the EURO. It went negative around Nov 22nd and will stay that way for the foreseeable future.

My rule of thumb is to look at the 500mb height anomalies to get a sense of what the real phase of any one signal is in. A persistent trough in the west almost always is a neutral to negative PNA.

https://2img.net/h/s3.postimg.cc/rfrfiv1nn/ecmwf_pna_bias.png

[algae888]

thanks and wow frank that is significantly different from nws chart.

[sroc4]

frank and scott help me understand this if you can. everywhere I read people are saying we have a -pna however nws shows pna has been + to neutral since late September? so which is right?

also can there be a persistent trough out west with a neutral to + pna?

These can kinda be answered together. Those oscillation graphics produced by the NWS do not do a great job in sensing or measuring wavelengths over a given area. They are also based off the GFS, a statistically poor model when it comes to oscillation forecasting. Here is the PNA forecast from the EURO. It went negative around Nov 22nd and will stay that way for the foreseeable future.

My rule of thumb is to look at the 500mb height anomalies to get a sense of what the real phase of any one signal is in. A persistent trough in the west almost always is a neutral to negative PNA.

https://2img.net/h/s3.postimg.cc/rfrfiv1nn/ecmwf_pna_bias.png

Exactly.  And to show wjy I don't use that NWS graph for teles here is the Euro, EPS, GFS, and GEFS for the PNA through weather bell.  Like Frank said looking at the 500mb pattern in the west for the PNA the WB graphs seem much more realistic.  I mean look at the difference in the forecasted GFS ensembles on that NWS graph vs weatherbell, then look at the 500mb forecasts.  

[Frank_Wx]

That was an interesting 12z GFS run. Look at what it did with the -EPO ridge. Instead of confining it to the Aleutians it cut it off over Alaska

[Frank_Wx]

For the record, if the GFS came to fruition then YES we will see an artic outbreak AND snow in our area. But that is the first run of any model I saw the ridge track into Alaska.

[sroc4]

Looking at the 500mb map above the northern portion of the PNA region technically has ridging so this is likely why the absolute value looks like it might be positive. But clearly the trough in the SW would lead to -PNA type response to our sensible weather. At least that's how I see it devoid of any other broad scale factors.

[algae888]

12z euro 995mb low apps runner to 957mb low east of maine 5th and 6th. Interesting followed by bitter cold all across canada entering ne and nw us.

[algae888]

That was an interesting 12z GFS run. Look at what it did with the -EPO ridge. Instead of confining it to the Aleutians it cut it off over Alaska

12z euro has the same intensity with high pressure except its West. Get ready the cold is coming

[algae888]

wonder if dec ends up like this? from another poster weak nina/+qbo

looks like todays gfs

[algae888]

this is the best early dec pattern we have had in 6 years. ill take this pattern any year for early December and looks more interesting as we move deeper into month. does that Aleutian ridge move right over Alaska post 10 day on op euro to match gfs? hmm

[amugs]

This would be sick if it verifies - skeptic yes BUT IF those extreme heights build over the NW Alaska and we have which we will a good base of snow in the NW CONUS and Central Conus the air will have trouble modifying and this could very well happen - slosh tube effect JB has been harping on and something I discussed with a pro met who worked for NOAA in Alaska for 12 years and now works for meteo? in NY State and New England. Lyndon State grad in 2000.

He said that at this time of year if yuo build heights over the top it forms an alley so to speak for cold air to drain into the CONUS - not saying a snowy pattern but IF we get a gradient set up with a SE ridge as this map shows then ala 93-94 and you can take your -PNA.



Also, the wetness this week will help not only the drought conditions but the cold and precip for storms as we move forward - soil less ground raises temps and wet ground keeps things cooler, hydro cycle.

[Dunnzoo]

this is the best early dec pattern we have had in 6 years. ill take this pattern any year for early December and looks more interesting as we move deeper into month. does that Aleutian ridge move right over Alaska post 10 day on op euro to match gfs? hmm

I'm with you! Anything would be better than last year. December usually isn't too exciting in these parts anyway, so seeing the cold coming is a plus. We are in a pretty decent wet pattern, so sooner or later we'll see snow. I'm trying not to model hug, just trying to work on rain timing for this week since I am on vacation!

[Frank_Wx]

wonder if dec ends up like this? from another poster weak nina/+qbo

looks like todays gfs

Look at the blocking from northern Europe (Scandinavia) to Greenland. I do not see that anywhere on any models.

this is the best early dec pattern we have had in 6 years. ill take this pattern any year for early December and looks more interesting as we move deeper into month. does that Aleutian ridge move right over Alaska post 10 day on op euro to match gfs? hmm

This is THE most important question we have to answer this week. It will determine our December.

[Frank_Wx]

Man the late October to early November pattern was ripe for strengthening WAF into the Strat. Nice Aleutian trough and Siberian High. If we can get back to this - given the already weak nature of the PV - it could lead to a SSWE.

[algae888]

the 5th to -8th time frame getting more interesting. gfs and cmc both have a n/s system and hold back the energy in the sw and gulf.


gfs and cmc then eject the energy east by the 7th.


cmc is well south and gets sheared and gfs forms a weak coastal.
the euro on the other hand amps up the energy in the gulf and it cuts.


here is the gfs and euro at 500mb on sunday night the 4th.


big difference.

here is what I like about set up esp on euro.
we have a block over Hudson bay a 50/50 low and hp over southern Canada. if system doesn't get as amp as euro depicts, which it sometimes does, then this system has a chance to stay south of  us and maybe redevelop off coast allowing for a colder solution. either way we have a good shot at seeing snow either on the front end (cuts) with hp and cold air damming as 00z euro depicts or if low takes a track further south with colder solution. stay tuned

[algae888]

after that here comes the cold and the fun may really begin...

[algae888]

can we say sswe...

12z

00z
look at that hp over Siberia and arctic.

[algae888]

eps matches the op.

obviously not as amped. that's a descent look. 7 days out so a lot can change

[Guest]

Cutters in early December don't excite me.  Sorry!

[rb924119]

Yeah Al, I've become much more interested in this same period over the last few days of model runs as well. I may do a video today or tomorrow as to why, and my thoughts behind it.

[amugs]

Cutters in early December don't excite me.  Sorry!

I hear ya BUT what we need understand is that cutter can be and a prelude at times (many actually) to a changing pattern and help start to set things up as we move forward - ala 50/50 block, blanket a cold pool of air source in Canada, help break the dam of cut off Arctic air etc. So I will take a cutter or two to help do this which I think starts to occur.

Jim, I want a snowstorm as bad as the next weenie on this board but understand which I know yuo do that we things to take shape and cutters help this occur.

[sroc4]

Cutters in early December don't excite me.  Sorry!

I hear ya BUT what we need understand is that cutter can be and a re prelude at times (many actually) to a changing pattern and help start to set thing sup as we move forward - ala 50/50 block, blanket a cold pol of air source in Canada, help break teh dam of cut off Arctic air etc. So I will take a cutter or two to help do this which I think start to occur.

Jim, I want a snowstorm as bad as the next weenie on this board but understand which I know yuo do that we things to take shape and cutters help this occur.

Agree!!!

[Snow88]

Euro is coming in colder/ less amped for the 5th storm. Great hit for interior areas.

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