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Pattern December, Make analogs relevant again

I’m not a fan of the 18z gfs..warmest cycle compared to the last six for Atlanta. How do ensembles look?
 
EastAtlwx said:
I’m not a fan of the 18z gfs..warmest cycle compared to the last six for Atlanta. How do ensembles look?
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This is tricky for the SE. Indeed, the 18Z GFS 6-15 is the warmest GFS of the last 6. However, the 18Z GEFS is just about as cold as any run in the 6-10 and is either the coldest or about tied for the coldest in the 11-15. Moreover, the 12Z EPS and CMC ensembles in the 6-15 are about the coldest yet.
 
GaWx said:
This is tricky for the SE. Indeed, the 18Z GFS 6-15 is the warmest GFS of the last 6. However, the 18Z GEFS is just about as cold as any run in the 6-10 and is either the coldest or about tied for the coldest in the 11-15. Moreover, the 12Z EPS and CMC ensembles in the 6-15 are about the coldest yet.
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Thanks Larry for pointing this out! Just another great example of why we use ensembles not deterministic forecasts esp beyond the medium range and/or when the operational looks nothing like its ensemble mean at the synoptic-planetary scale
 
GaWx said:
No, the models for the most part aren't plunging the cold deep down into the SE (at least not yet). Rather, the SE is near the bottom of intense cold to the north, which could pay off at some point with a winter storm traveling along the boundary if it can tap into the lower level cold air via CAD assuming WSW upper flow/upper trough axis near the MS River or a little further west..
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Lol, that's where it gets so twisted down here. We need the cold, good strong cold that won't erode, but it can't be too cold, or get in here too quick :) It's got to get into just the right position, with just the right winds at different levels, to allow the over running, while being reinforced. Meanwhile, we want a gulf low that's weakish, but not too weak, lol. And most of all, for me, the whole set up has to remain ignorant of the I 20 mystery line, lol. We just need a good little ice age to come along for a few years so we don't have to work for it so hard :) T
 
SD said:
That's cold

Sent from my SM-G955U using Tapatalk
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Yep, below-well below average by day 4 and thru at least mid month, not bad.
Of course right as I post this, Maue just finished the EPS city charts page on his free wx.graphics site
http://wx.graphics/models/city/eps_charts.php

Really like how he gives us spread & uncertainty in the members in addition to the mean. Once he gets these done and snowfall accumulation maps for the EPS suite, I'd consider weatherbell completely obsolete and not worth paying for anymore.

KRAH_2017120312_forecast_EPS_360.png
 
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pcbjr said:
No, but 43 and 45 have possibilities for a like - in January ... :p
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Yeah, 43 would "nail" us both with 0.5". "Nail", of course is a relative term as that would be huge for either of us, especially you.

I do find the 50 members overall to be rather interesting for my area as I count 7 of the 50 (14%) with measurable SN/IP and 5 of the 50 with 0.5-2", any of which would be a pretty rare hit. Now that SN is supposedly really SN (that glitch has been fixed, correct?) I would only rarely expect to see any run as good as that of this 12Z EPS absent the rare impending storm. In the city, itself, since 12/1989, the few measurable hits (3) were under 0.5". So, this is saying there is a 10% chance for the heaviest SN/IP here in 28 years! That's more than enough for me to be hopeful, especially considering the EPS' warm bias and the expected averaged out solidly -AO for the rest of Dec.
 
To show how potentially long this upcoming cold period is to our north, the 12Z EPS mean has Chicago (O'Hare) staying at 28 or colder for at least 12 straight days to the end of the run. I believe I have to go all of the way back to Jan-Feb 2007 for the last time that was exceeded. There may not be any extreme lows showing up (at least not yet... maybe that would require much more snowcover there and to their north), but the longevity is quite impressive. Very long cold like this (and it could go even longer though short breaks would be normal) will hopefully pay off with a SE winter storm underneath at some point this month or in the first half of Jan, the most likely period per my analogs.
 
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