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December Discussion


NorEastermass128
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Beware those mjo diagrams. They can be contaminated and show the mjo going into phases not true. You’re better off looking at the VP (velocity potential) at 200mb. This is basically showing where we have divergence and where the mjo will typicaly show itself. The EC is usually best for that. However if you use those Wheeler diagrams, look at the EC. I believe the gfs still has a retrograde bias.

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5 minutes ago, TheCloser24 said:

12z FV3 GFS shows how next weeks storm COULD be wintry.

potent Arctic pop careening into the backside too - 

that system's been flagged for a while... The other models...heh, off and on more or less.  The FV3' isn't shy about cold boundary layer systems over this pattern (thus far that I've noticed). Not sure how it is scoring.

The model's 'experimental' technically, but is scheduled for parallel roll-out in mid December. That'll be interesting!  Get to start making 'official' 'er comparatives. 

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Just now, Great Snow 1717 said:

Certainly a different look than the GFS. Just from casual observation it seems as if the FV3 tends to be colder than the gfs.

Well the current GFS def has a warm bias in the boundary layer. Though that wouldn't explain why the FV3 is colder from a hemispheric pattern perspective. But I have noted that the FV3 is def doing a better job with the BL cold in storm systems. 

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In any case... the current perf monitoring on the FV3' discusses that it does have a progressive bias in the middle range ... to which next week is bit late on that but within reasonable scope. 

The 00z Euro was primaried up over the eastern Lakes with another one of these excruciatingly boring pallid commitments to secondary...  So, it might be interesting to 'contest' the two, and see if the FV3 goes back west or the Euro comes east...etc...etc

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3 minutes ago, Typhoon Tip said:

In any case... the current perf monitoring on the FV3' discusses that it does have a progressive bias in the middle range ... to which next week is bit late on that but within reasonable scope. 

The 00z Euro was primaried up over the eastern Lakes with another one of these excruciatingly boring pallid commitments to secondary...  So, it might be interesting to 'contest' the two, and see if the FV3 goes back west or the Euro comes east...etc...etc

Sort of like Rocky vs Creed.....lol I do think it will be interesting to see how the Euro and FV3 evolve over the next several days. 

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14 minutes ago, Great Snow 1717 said:

Sort of like Rocky vs Creed.....lol I do think it will be interesting to see how the Euro and FV3 evolve over the next several days. 

yeah... and "progressive" can come in a couple different meanings, too..  Like, 'too fast' or 'too far east' are both encapsulated in progressive bias; but they have different causes..  

They're likely subjective (physically influencing...) one another, but, looking at snap shots of D8's and 5's and 3's ... a system being corrected gradually west could be slowing down across successive model runs as much as the model being too stretched in the west-east coordinate.  blah blah .. 

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10 minutes ago, weathafella said:

So-in recent modeling the pig is further north in AK.  EPS at 0z had the worst of it a bit NW.  significance?

It depends how far north. You don't want it sitting over N AK and the Beaufort sea either. If it starts getting more toward Siberia like over the Chukchi and East Siberian sea then that can be fine...or far enough west where it crosses the dateline and allows for some ridging to pop in western Canada. 

We could also mute the impact if we either get a really good split flow coming onshore in the west (this will reduce the Canada torch if a chunk of the mild air is diverted to the southern stream by split flow) or we can somehow get a -NAO. The latter seems tougher to get and models aren't that excited about it...though a couple runs have hinted. 

 

Regardless, none of these are going to stop the milder pattern...it's probably coming unless really big changes happen fast...but it could be a less hostile mild pattern if that occurred. 

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1 hour ago, ORH_wxman said:

Well the current GFS def has a warm bias in the boundary layer. Though that wouldn't explain why the FV3 is colder from a hemispheric pattern perspective. But I have noted that the FV3 is def doing a better job with the BL cold in storm systems. 

Do you know when that model is taking over as the OP? And are they changing the name to FV3 or is that just a code name?

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13 minutes ago, The 4 Seasons said:

Do you know when that model is taking over as the OP? And are they changing the name to FV3 or is that just a code name?

I'm not 100% sure. Chris would probably know. I remember reading it was going to be operational in 2019 but no month was specifically listed. I'm not sure if they are still on target for next year or not. 

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23 minutes ago, The 4 Seasons said:

Do you know when that model is taking over as the OP? And are they changing the name to FV3 or is that just a code name?

 

7 minutes ago, ORH_wxman said:

I'm not 100% sure. Chris would probably know. I remember reading it was going to be operational in 2019 but no month was specifically listed. I'm not sure if they are still on target for next year or not. 

Pretty sure Jan 2019 is go time. It's checked out on all review, "does no harm" to skill scores, etc. So they are just waiting to push the button.

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4 minutes ago, OceanStWx said:

 

Pretty sure Jan 2019 is go time. It's checked out on all review, "does no harm" to skill scores, etc. So they are just waiting to push the button.

 This contains some useful info - ...also, discusses that it will be in parallel with the GFS in mid December ... which technically right now it is not.  The entire doc this comes from is posted by NOAA ... it's over the 9.7+ mb file size so I can't post it here.  

 

image.png

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Just now, mahk_webstah said:

Sometimes it seems that when -epo is showing up a lot on LR runs it tends to happen, yes?

If an actual EPO block can form as opposed to a ridge, then we will likely see the solutions become significantly colder. And yes, frequently a ridge of that magnitude does seem to pinch off a block. Obviously the strength of that block is important but even a weak one is still a lot more resistance than a transient ridge. 

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I like the 5-10th period for a storm on the East Coast, models seem to be in a -NAO pattern with 50/50 low blocking the pattern allowing it slow down some, this would be perfect as a decent cold air mass is modeled over the region before the 10th of DEC, this should allow a coastal storm to bring in snowfall to the coastline for a change, instead of this constant rain barrage.  Although short in time and duration, the cold will only last until the 10th and then a torch like pattern ensues as a major ridge settles over the Eastern US.

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Latest CPC ensemble guidance for the AO index shows a prolonged negative pattern, which means cold air masses will be around and energy to spark a coastal storm will be dependent upon the location of the Polar Vortex in Canada, if it is near Hudson Bay, Canada and especially James Bay, then the coast seems likely, if it is western Hudson Bay, then cutters will be the storm track.  12z EURO shifts the PV to the east, allowing for a trough over the eastern US and coastal low to develop in the pattern.

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