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Pattern December to Remember

Myfrotho704_ said:
I respectfully disagree. It’s not a great pattern at all and I’m not saying it is, but it’s not that terrible, you literally have one of the key pieces to a Carolina winter storm on the 18z GFS run, a strong 50/50 low. It’s a big change vs last years WAR, as I’ve said many times, all you need is a handoff of energy time right with the confluence and you have something interesting. A terrible pattern is a pattern with no options to score. This pattern has a option that might be a stretch, but it’s still a small possibility. Again this is just the OP GFS, and the GEFs wasn’t as good as the 12zView attachment 98211View attachment 98212
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This pattern is not a pattern we are going to get snow in. The ridge creates a flow that really is not conducive for snow to develop. The 50/50 low means nothing with the ridge as any s/w will likely remain north of us. With that being said, the pattern is not bad for cold weather which is something to be excited about. I'm however encouraged about chances in the long term to move to a +PNA which will end up boosting our chances of snow.
 
Ollie Williams said:
This pattern is not a pattern we are going to get snow in. The ridge creates a flow that really is not conducive for snow to develop. The 50/50 low means nothing with the ridge as any s/w will likely remain north of us. With that being said, the pattern is not bad for cold weather which is something to be excited about. I'm however encouraged about chances in the long term to move to a +PNA which will end up boosting our chances of snow.
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That been the big debate in the past for the importance of a +PNA to score winter storms. I know with a perfect setup (-AO, -NAO, etc.) we can pull something out of the hat, but from all the years of tracking storms the PNA has been the biggest player for us SE folks. Bigger the ridge out west the more the storms dig in the SE.

And, the PNA looks to stay negative in the LR: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/teleconnections.shtml
 
FallsLake said:
That been the big debate in the past for the importance of a +PNA to score winter storms. I know with a perfect setup (-AO, -NAO, etc.) we can pull something out of the hat, but from all the years of tracking storms the PNA has been the biggest player for us SE folks. Bigger the ridge out west the more the storms dig in the SE.

And, the PNA looks to stay negative in the LR: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/teleconnections.shtml
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Well, it's not necessarily that we need a +PNA, but we need to have room for a s/w to dig or slide east. Here is a run composite of the most favorable 500mbar looks across NC.
Charlotte.pngRaleigh.pngGreenvilleH5.png
 
Webberweather53 said:
Ok, here's the updated version of the daily teleconnection spreadsheet. It now includes the my ENS ONI (I have a paper that's been accepted and should be published soon), daily standardized indices of the NAO, PNA, EPO, WPO, TNH, SCAND, AO, AAM, & RMM MJO coupled w/ dates for winter storms in NC since 1948.

Have at it @Ollie Williams

Nov-Apr Daily Teleconnections and NC Winter Storms List (1948-2021)
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Thank you! I've been working on creating a snowfall anomaly algorithm this evening. It will be nice to have some more data to work with.
 
Ollie Williams said:
Well, it's not necessarily that we need a +PNA, but we need to have room for a s/w to dig or slide east. Here is a run composite of the most favorable 500mbar looks across NC.
View attachment 98217View attachment 98218View attachment 98219
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The main thing all of those images have in common is the ridging in NW Canada. The response is lower heights in the SE. It also creates the proper trajectory in the Northern stream for both cold air transport and for the opportunity of a SW in the northern stream to dig a bit and phase with a southern stream wave...or at the very least, move through in advance of a southern stream system, laying the cold foundation and keeping the southern system suppressed.

And you see heights along the west coast aren't all that amped. Get any blocking up north and you have a chance for a big dog.

Our current pattern (and the predicted pattern for at least a while) features the NW Canadian ridge way out west toward the Aleutians. Not ideal.
 
Rain Cold said:
The main thing all of those images have in common is the ridging in NW Canada. The response is lower heights in the SE. It also creates the proper trajectory in the Northern stream for both cold air transport and for the opportunity of a SW in the northern stream to dig a bit and phase with a southern stream wave...or at the very least, move through in advance of a southern stream system, laying the cold foundation and keeping the southern system suppressed.

And you see heights along the west coast aren't all that amped. Get any blocking up north and you have a chance for a big dog.

Our current pattern (and the predicted pattern for at least a while) features the NW Canadian ridge way out west toward the Aleutians. Not ideal.
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Rain, do you think we will get to the more favorable pattern in January, providing the mjo moves along? No fun chasing unicorns lol
 
Mr. Golf said:
Rain, do you think we will get to the more favorable pattern in January, providing the mjo moves along? No fun chasing unicorns lol
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It'll be fun if you catch one though!

I think we'll move into a better pattern in January, at least for a while. Whether or not we do something with it is a different story. It's likely that when it's all said and done, it will have been a relatively mild winter with below normal precipitation in the SE. If that is the case, then the odds favor below normal snowfall. But if everything comes together just once, you can go above average in the snowfall department, just like that.
 
GaWx said:
Quiz: what do these 5 periods have in common weatherwise?

- 12/29/1967-1/13/1968
- 12/1/1968-1/16/1969
- 12/27/1978-1/9/1979
- 1/24/1979- 2/21/1979
- 11/27/2010-12/25/2010

I’ll have more to say about this when I get some time, hopefully by this evening. Hint: it may be relevant to upcoming SE weather forecasting discussions for very late this month into January.
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Here’s the answer: These 5 periods are the only two week plus long cold periods at ATL since 1950 that were during a -PNA:

- 12/29/1967-1/13/1968: 0.2” + 2 Ts of SN
- 12/1/1968-1/16/1969: 3 Ts of SN
- 12/27/1978-1/9/1979: 2 Ts of SN
- 1/24/1979- 2/21/1979: major ZR & 4.4” of sleet from different storms
- 11/27/2010-12/25/2010: 1.3” Christmas snow (only measurable one on record?) plus 3 other trace to 0.1” wintry events.

So, what did these rare five periods have in common to be able to get that longlasting cold during a -PNA? A -AO and a -NAO were both present every time with them being quite strong during most of these 5 periods. A -EPO was present only during 3 of the 5 periods….so, not crucial. ENSO wasn’t crucial. The key is the strong -AO and -NAO. Furthermore, note the multiple wintry precip events during all 5 periods.

This is relevant in case we never get out of the -PNA to see if there’d still be much hope for sustained cold in the SE. Whereas a +PNA would certainly be most preferred, these five periods show that given both a strong enough -AO and -NAO it is still a reasonable possibility.
 
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The 0Z GEFS sucks around days 9-10 as it is the warmest run of at least the last 4 then. It may be because of a weaker -NAO as Europe is also not as cold. Let’s see how much it cools later.

Edit: the warmest coldest of any December on record at KATL is the 31 of 1931. Tied for second warmest at 30 are five years including 2014, 2012, and 1994. So far, the coldest this month is 36.
 
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The 0Z GEFS, like most runs, slowly improves late.with strong cold n Plain to Washington state.
 
Rain Cold said:
It's just not going to be cold enough. I would consider a non-terrible pattern to be one that isn't 85%+ chance against us. The upper level confluence is not bad, I don't disagree. But you literally have no genuine cold air nearby and no snow pack to our northwest. With the little bubble ridge in the middle of the country, you have an unfavorable storm track, with the exception of potentially a quasi-cool Miller B that might produce some front end mix for some lucky areas. We just need more than a -NAO and 50/50, particularly in today's climate, particularly when the bulk of the cold is well to our northwest, and particularly in early winter. This is just going off the 18z GFS, though.
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Goofy keeps throwing up gom lows, and if they actually start occurring in Jan, we might find some cold air to go with it. I never expect much until near New Years. Except for that weird Xmas annomoly a few years back...and that might have been mass hypnotism, lol.
 
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