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January Long Range Disco Thread


yoda
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6 minutes ago, CAPE said:

Thanks, but what makes this fun is everyone contributing and sharing info and getting different perspectives. It's a group effort.

GEFS 850 MB temp anomalies still look to improve considerably after Jan 16, both for us and for our source region.  2m anomalies are disappointing though.

image.thumb.png.3db1133a99a9f4b53b6e3e6242b2f52b.png

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8 minutes ago, psuhoffman said:

It just depends. Not all blocking patterns are the same. But a -NAO split flow isn’t uncommon and usually a good thing. It’s not a cold pattern.  Feb 2010 was one. The Polar jet was directed across Canada by the trough in the pac but the southern streak was splitting into the SW and coming across the gulf coast.  But the pac jet wasn’t as intense and the profile in Canada wasn’t as awful to start. But it wasn’t warm. Actually north of us was very mild. And even here it would have been 45 that week had there not been snow.  It’s a puck your poison thing. A split flow cuts off the polar air but normally in winter we can develop a just cold enough airmass under the flow to get snow with a good track. This year that didn’t work out. A -EPO -NAO non split flow is much colder but it can be a dryer pattern if storms dive in too far north to amplify under us and the STJ is cut off in just case. So there are pros and cons to both. FWIW the split flow option accounts for a lot of our HECS storms. 

Could be just bad luck/bad timing then, or an indication of some longer term changes. Given the HL look we have had, it seemed different to me. Maybe that is partly due to the ground truth here being exactly the same as last winter, despite the HL blocking lol. It will be interesting to see how things play out over the next 10 days or so, when it appears we will have some colder/drier air to work with, and blocking in place. Better luck if nothing else, hopefully.

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12 minutes ago, cbmclean said:

GEFS 850 MB temp anomalies still look to improve considerably after Jan 16, both for us and for our source region.  2m anomalies are disappointing though.

 

Yeah I wouldn't worry too much about the 2m temps as advertised. Just having somewhat colder, lower dp air available will make a big difference. With a -AO/NAO,  we tend to have the highs and lows in the right places, and evaporational cooling can work its magic.

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11 minutes ago, cbmclean said:

GEFS 850 MB temp anomalies still look to improve considerably after Jan 16, both for us and for our source region.  2m anomalies are disappointing though.

image.thumb.png.3db1133a99a9f4b53b6e3e6242b2f52b.png

While they could be right for the wrong reasons I would tend to just look at the 850 mb anomalies. The long range 2m temp anomalies are atrocious to say the least.

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As snowdreamer noted, the best chance of snow in MBY according to the EPS is on the 20th - could be fun to watch the ... REMINDER: NO ...

While there is nothing through the medium-range, the 15 day mean of 2  - 2 1/2 inches is higher than its been in quite a while.  The 20th is roughly when the PNA is forecast to go negative for a while. 

 

 

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8 minutes ago, CAPE said:

Could be just bad luck/bad timing then, or an indication of some longer term changes. Given the HL look we have had, it seemed different to me. Maybe that is partly due to the ground truth here being exactly the same as last winter, despite the HL blocking lol. It will be interesting to see how things play out over the next 10 days or so, when it appears we will have some colder/drier air to work with, and blocking in place. Better luck if nothing else, hopefully.

I think, as wxusaf, that it’s a bit of both bad luck and the background stage becoming incrementally more hostile. In December we had a nice AO ridge but it was a bit north of perfect.  That can work though if you get other things to line up and we almost did but that SW that dive in out west really screwed us by amplifying the trough more. But it’s hard to get a big snow in mid December.  The first iteration of the -NAO this month ended up too extreme imo. That was part of the problem.  I posted this from a couple days ago. 
DAF7CF87-40F5-4860-87D4-2AABBD50DF37.thumb.jpeg.e1e8e16c6ce0576f44a08d5d35fae244.jpeg
That ridge is centered way too far south and extends too far SW.  Not only did that suppress 3 waves but it prevents colder air from draining into the pattern to the west of the block.  Center that further north without that extension into Quebec and we get a slightly colder profile and less suppressed systems and I bet one of them “works out”.  This next flex of the blocking looks more ideal but now there are questions about what kind of PAC we get. Ideally I would have liked one more bite of the apple with the current pac and a better NAO. But I don’t have the magic crayon. And the look we see now is pretty darn good. And I’m biased by my location. If I were you I would definitely go with the colder but possibly dryer option. We have way different climo. 

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14 minutes ago, psuhoffman said:

I think, as wxusaf, that it’s a bit of both bad luck and the background stage becoming incrementally more hostile

Just curious how much impact you think the hostile November had.  You have mentioned it a few times as a negative factor, but was it a MAJOR factor?

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56 minutes ago, psuhoffman said:

Just a little blocking when storms transfer from Indianapolis to Hatteras 

It's been so long since  we've had an actual block I think we forget what crazy storm tracks that can cause lol.

That storm on the GFS at 300+ hours out looks like it's going to be Rainer but the block says nope your going south. 

If we can't score the last 10 days of January If this pattern comes to pass, I dont know what to say lol.

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1 hour ago, cbmclean said:

If you are feeling didactic tonight, what exactly is a "transfer"?  I only have the vaguest idea of storm dynamics.

I’ll let others explain better, but basically when a low pressure hits a high pressure and a new low forms. Here is a random map I pulled off google showing the two lows. The secondary is the one forming near the coast. 

A5B39438-195A-4EC2-B746-6F54F1046A3F.jpeg

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3 hours ago, cbmclean said:

If you are feeling didactic tonight, what exactly is a "transfer"?  I only have the vaguest idea of storm dynamics.

A low transfers when it meets resistance and can no longer progress and reforms somewhere else along the thermal boundary. This can happen because of the upper level support jumping or a surface feature blocking progress. Often the jump we want is a system moving northeast up the west of the Apps to jump to the coast. What typically causes this is when a cold high is blocked in to the north impeding the low, and CAD banked in against the mountains so the path of least resistance is to jump east to the baroclinic zone along the coast.  The example from the 18z gfs is below. 
3718FBCA-BEE8-4214-B8C2-52AB4C0D0998.thumb.jpeg.1a3255e69fd132da5918c6fe0f9e75c0.jpeg

the primary in the Midwest has hit a brick wall of confluence. Note that system to its north hit the same wall and has actually done a loop and is retrograding west because it’s an arctic wave removed from any thermal gradient so it had nowhere to jump too. It simply put er in reverse lol. That primary in IN can’t go anywhere. So it’s going to transfer to the triple point along the front in the Carolinas. That’s common because there is often a lot of lift there that can promote pressure falls and an enhanced baroclinic boundary. It’s also along the warm front providing a path east under the block for the storm to progress so it transfers the energy there. 

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10 minutes ago, Ralph Wiggum said:

and energy ejecting out of the Rockies

On this plot what indicates "energy"?  I am used to seeing people refer to "energy" when they are talking about areas of enhanced vorticity on vorticity maps, but I don't see what you are referring to on this map.

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6 minutes ago, cbmclean said:

On this plot what indicates "energy"?  I am used to seeing people refer to "energy" when they are talking about areas of enhanced vorticity on vorticity maps, but I don't see what you are referring to on this map.

You can’t see it directly there but you can see the evidence because there is a 1004 surface low with h5 low ejecting so obviously it has an associated SW and vort. It’s just assumed from secondary evidence. 

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3 minutes ago, psuhoffman said:

You can’t see it directly there but you can see the evidence because there is a 1004 surface low with h5 low ejecting so obviously it has an associated SW and vort. It’s just assumed from secondary evidence. 

GFS isn't far off from that look either. Liking this setup more than 18z. Little more separation between jets, less phasing in plains

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