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December Medium/Long Range Discussion


yoda
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@frd good morning. Nice updates. Couple thoughts. 
1. I think for a while we’re going to have to roll the dice with domestic cold. The WPO trough is prevented cross polar flow but it’s also preventing the Nina from taking over also.  Overall it’s a trade off I’ll take. Domestic cold worked in January 2016 btw. But not before some frustrating rainy coastals earlier in the month.  So long as the source regions in Canada aren’t super warm even air that is a little above normal there will usually work mid winter is discharged south into our region.  If the NAO and AO really tank (and some guidance suggests it will) and exerts pressure to retrograde the WPO a little further west and allow an epo ridge (the famous ridge bridge) then we could see a colder regime. 
 

2. I am by no means a Strat expert. But in my experience whenever we have had a PV “event” that leads to extended blocking during the core of winter there were hints in the TPV before the stratospheric warning or wind reversal.  In 2009 the TPV was already a mess before the SPV collapsed.  I’ve never seen the TPV in a completely hostile state mid winter and a SSW suddenly saves us.  2018 was the closest to that but it happened very late in the season. There is some synergy there but that’s why I don’t spend a lot of time focusing on the strat to hope for a save. Typically you see it coming at the trop level also. This would be a perfect example.  

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28 minutes ago, psuhoffman said:

@frd good morning. Nice updates. Couple thoughts. 
1. I think for a while we’re going to have to roll the dice with domestic cold. The WPO trough is prevented cross polar flow but it’s also preventing the Nina from taking over also.  Overall it’s a trade off I’ll take. Domestic cold worked in January 2016 btw. But not before some frustrating rainy coastals earlier in the month.  So long as the source regions in Canada aren’t super warm even air that is a little above normal there will usually work mid winter is discharged south into our region.  If the NAO and AO really tank (and some guidance suggests it will) and exerts pressure to retrograde the WPO a little further west and allow an epo ridge (the famous ridge bridge) then we could see a colder regime. 
 

2. I am by no means a Strat expert. But in my experience whenever we have had a PV “event” that leads to extended blocking during the core of winter there were hints in the TPV before the stratospheric warning or wind reversal.  In 2009 the TPV was already a mess before the SPV collapsed.  I’ve never seen the TPV in a completely hostile state mid winter and a SSW suddenly saves us.  2018 was the closest to that but it happened very late in the season. There is some synergy there but that’s why I don’t spend a lot of time focusing on the strat to hope for a save. Typically you see it coming at the trop level also. This would be a perfect example.  

 

I am with you regarding your thoughts and progressions. 

Seems colder air gets involved later,  but we could score with typical cold as we near better climo.

Strat is preconditioned and the trop is receptive to the incoming and ongoing SSWE. Also, as HM alluded to,  the timing of this event is very good, nothing really on the table to interfere. In the past the high amp MJO and Pac features made the SSWE useless and entered chaos into seasonal forecasts. 

This time the brunt of the hoped for benefits seems to  NA and the Eastern US in time. 

As several strat experts have mentioned nothing is a slam dunk in long range forecasting, but so far it looks good and the event is becoming more likely as well. 

The  expansive event getting underway in Siberia will hopefully lead us to a more conducive period of +PNA. 

Meanwhile very cold air should begin to pool and grow in coverage in Central Canada. Get that Greenland blovk to retro as well and the bar is raised. 

Looking at the lastest GFS NH polar vortex ellipse time lapse forecast, it seems to place us in a interesting location as the SSWE progresses. 

Also of interest, is Anthony's post yesterday  regarding the pv, strat, and the warming, etc. He mentioned the event itself may, depending how it evolves, could create it's own regime. I thought that was a very interesting comment.       

 

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gfs_nh-gphellvert_20201221_f384.png

 

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@frd wrt HMs comments he may have been alluding to my observation that Mjo waves in conflict with a dominant base state do not have the same impact on the pattern as when the MJO is driving or in synergy with the dominant pattern. A brief warm phase mjo in a -NAM base state won’t hurt is as much as when the MJO goes ape in warm phases during a +NAM state. 

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54 minutes ago, psuhoffman said:

I am by no means a Strat expert. But in my experience whenever we have had a PV “event” that leads to extended blocking during the core of winter there were hints in the TPV before the stratospheric warning or wind reversal.  In 2009 the TPV was already a mess before the SPV collapsed.

Luckily this year the TPV is already in a discombobulated state (the AO has already been negative since the beginning of December and that's before the upcoming SSW). I'm not saying that there will be a 2009-10 repeat this year but it is an interesting little tidbit in regards to the TPV/SPV.

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Just now, nj2va said:

GFS with the classic Ontario to well off the Delmarva coast low transfer to recurve inland into Phin’s backyard.  I don’t think Ji will like it...

I’ll give it another couple days but I think the 28th storm is a rain event. NAO block at that time doesn’t look as west-based as it did several days ago, which allows the primary to cut far to our NE before transferring.

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13 minutes ago, WxUSAF said:

I’ll give it another couple days but I think the 28th storm is a rain event. NAO block at that time doesn’t look as west-based as it did several days ago, which allows the primary to cut far to our NE before transferring.

wait.  Just so I understand what you are saying clearly.  Are you saying that modeled blocking from a couple days ago might not pan out?  This seems unpossible

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7 minutes ago, leesburg 04 said:

Good thing those of us to the North and West have seen snow already. That could be our only shot in 2020

The only white Christmas I'll see is if they hold a Barry Manilow concert on my patio on Friday.    It is what it is.   I'll be away until the 7th anyway.  I hope y'all get zilch until then.   I still love you tho.

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1 minute ago, stormtracker said:

The only white Christmas I'll see is if they hold a Barry Manilow concert on my patio on Friday.    It is what it is.   I'll be away until the 7th anyway.  I hope y'all get zilch until then.   I still love you tho.

The 7th?  I guess I'll just have to celebrate NYE with a fine bottle of JWB

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Just now, stormtracker said:

The only white Christmas I'll see is if they hold a Barry Manilow concert on my patio on Friday.    It is what it is.   I'll be away until the 7th anyway.  I hope y'all get zilch until then.   I still love you tho.

Barry really is the whitest guy on the planet next to fitness guy Richard Simmons.  When Barry sings Copacabana all is right with the world.  

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Just now, poolz1 said:

A nice west based block...finally some consistent lower heights in the 50/50 region and the gfs just shreds every sw coming east.  Need just a mediocre PNA ridge to get something to amplify.

Should be seasonally cold.  That maybe all we can get.  Hoping one of those CAD over run events show up.  Anything really 

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1 minute ago, BristowWx said:

Should be seasonally cold.  That maybe all we can get.  Hoping one of those CAD over run events show up.  Anything really 

I'll certainly take anything to track...May have to let this pattern mature a little into Jan.  Hopefully, the calls for increased +PNA start to pan out by then.

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