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Southeast Mid/Long Range Discussion III


Rankin5150

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At hour 120 on the new Euro, the favored upslope spots in Western NC could pick up a decent snow from a diving clipper on the back side of that upper low that is lifting out of the NE. I believe the GFS also entertained this possibility as well.

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How would we have sustained cold? What mechanism in the atmosphere would prevent a high from sliding offshore that isn't associated with a negative NAO. Not trying to be combatitive, but if there is one I am unaware. And to reiterate, I'm talking about sustained cold like we've seen the previous two winters, not one or two day cold shots.

Two of the all-time great southern snowstorms (Feb 1973 and Jan 1988) did not have a -NAO leading up to, or during the storm....but they did both have a tall ridge in western Canada / eastern Alaska that displaced a polar vortex down into SE Canada that provided a sustained period of cold air.

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If the artic oscillation tanks as projected and the NAO doesn't dive with it before/around the latter part of January, we could be in trouble. This block should set things off and shake everything up. Could the NAO stay positive? I guess, just much more likely it goes negative.

Based on the correlation, if the AO tanks, there's roughly an 80% chance the NAO will go with it.

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Based on the correlation, if the AO tanks, there's roughly an 80% chance the NAO will go with it.

Bingo, which is why it's not prudent to go cliff diving at this point in the game. The block won't be fully mature for several days still, and we have had an amped flow all year!

Let's say the block forms and the models suddenly begin to see blocking on the Atlantic side too.......several days from now. With so much in the flow, and so much cold air filling Canada and pressing into the US, it doesn't take much imagining to see a very snowy scenerio being possible.

Devils advocate - Yes I see some (some very respected people too) saying the last 10 days of January we see major warming. I guess that's a very real option. BUT, with things changing, let's just see how everything pans out.

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Maybe if there is thunder to be heard in tomorrow's storms and maybe if the folk tales about thunder in winter are true...then maybe we might see a couple of flakes in ten days...maybe!

That wives' tale has come tru before. It makes sense, too, because a severe thunderstorm system in winter would usually bring a change to the pattern and be a good set up for snow later on down the road. At one time there was something on the models around the 20th, but I don't believe it's there anymore.

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That wasn't sustained cold in the Feb. case - KILM had a high in the 30s for one day after the storm, and then warmed up to the mid 40s and then the mid 50s the next day in 1973. Also, the NAO was near neutral to slightly negative during the time frame of the storm. Jan 1988 did have sustained cold, but during that period the NAO was near neutral to slightly negative. I have the daily NAO values to support this.

Don't care what the temps were after the Feb 1973 storm. You can't have 2 feet of snow between Columbia and Charleston, South Carolina without a sustained period of locked in cold prior to the storm's arrival.

The NAO was positive every single day in both Feb 1973 and Jan 1988 - ftp://ftp.cpc.ncep.noaa.gov/cwlinks/norm.daily.nao.index.b500101.current.ascii

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This is why I'm looking at the NAO! Is that not meteorology? Wow.

That is the truth, it's not making things too simple. There is plenty of research to back this up. Maybe you don't understand what a negative NAO actually is?

You can't index your way to a snowstorm and sustained cold.

A -NAO is ONE way for sustained cold, depending on how you define the term sustained (one day, three days, a week, a month?) but not the only way.

But I agree, it would be helpful to have.

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Folks,

I see many folks here are in need of therapy. I have some good news, the doctor is in the house to try to help and I definitely don't mean the Doc (Euro).

1) I looked back at major KATL S/IP (3.5"+) weak La Nina storms back to the late 1880's. They took place on these dates:

1/28, 2/11-12, 2/11-12, and 2/15-16 from three different winters (1904, 1899, and 1895). Also, 2.3" fell on 2/29/1968.

2) Also, of the 18 weak La Nina's, a respectable four had both extreme cold (single digit or lower lows/multiple very cold days with highs of 24F or lower!) and the coldest of the season in early Feb. at KATL (1996, 1951, 1899, and 1895): Furthermore, regarding the other 14, two others (1968 and 1963) had very cold Feb.'s overall. In addition, 2/23/1939 was the coldest morning of that winter at KATL.

In summary, a very respectable 8 of the 18 weak La Ninas resulted in some interesting to very exciting wx in Atlanta either during very late Jan. or Feb. So, there remains reason for hope, especially if the NAO and/or AO would go negative.There wil be no charge for this session. Have a nice day!

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Don't care what the temps were after the Feb 1973 storm. You can't have 2 feet of snow between Columbia and Charleston, South Carolina without a sustained period of locked in cold prior to the storm's arrival.

The NAO was positive every single day in both Feb 1973 and Jan 1988 - ftp://ftp.cpc.ncep.n...1.current.ascii

Well I disagree with this. It was very warm prior to the Blizzard of 1993 and we still got plastered. You don't need a period of cold prior to a storm for snow to accumulate if it's heavy.

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Maybe we'll get a big surprise like the Carolina Crusher in Jan 2000. Nobody saw that coming, either.

It's funny you bring up that storm.We actually missed out on that storm in my area .But on Martin Luther King monday we we supposed to get a couplein of snow .There wasn't supposed to be very much moisature wiith the storm.We Woke up on tuesday morning to a whopping 8 in.Now 8 in of snow isn't a ton,lot more that we have now, but when it was wasn't forcasted it was a pleasant suprise.THen on wed night ,same week a clipper brought another 6 in.They said it would have been more but the system was moving fast.Fast foward to next weekend sat,before the epic snow on monday, we got another 5 in .and snow shoers on sunday.That was it for winter but it was an awesome 2 weeks.

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Don't care what the temps were after the Feb 1973 storm. You can't have 2 feet of snow between Columbia and Charleston, South Carolina without a sustained period of locked in cold prior to the storm's arrival.

The NAO was positive every single day in both Feb 1973 and Jan 1988 - ftp://ftp.cpc.ncep.n...1.current.ascii

Actually, to the contrary, it was quite mild the week prior to the great 2/1973 snowstorm. So, I disagree since there wasn't any cold prior to the 2/1973 storm.

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Exactly, which makes your post from one page back irrelevant...you could have a +PNA and a +NAO and still have cold and snowstorms in the SE...its happened MANY times...all you need is a subtropical jet and a little cold air spilling in from the north via a trough in the east and you can get a snowstorm.

So in order to have a conversation about the NAO, you must also talk about the EPO, WPO, PNA, MJO, AO, SOI, ENSO, etc.? Heck, the NAO doesn't even mean that much honestly - it's all about the positional placement of the anomalies be that a "west or east" based NAO.

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We weren't talking about snow! I said sustained cold, it was in the 60s the day before the February storm!!! You obviously don't know how to stay on topic, and you are 100% incorrect about the daily nao values. But carry on.

Feb. 1973 (days leading up to the storm): 2/1/1973 -3.2 2/2/1973 -19 2/3/1973 -1.7 2/4/1973 6.6

Where did you get those NAO values? The link he provided from NOAA shows:

1973 2 1 0.250

1973 2 2 0.252

1973 2 3 0.237

1973 2 4 0.525

1973 2 5 0.834

1973 2 6 0.944

1973 2 7 0.807

1973 2 8 0.672

1973 2 9 0.656

1973 2 10 0.718

1973 2 11 0.924

1973 2 12 0.928

1973 2 13 0.708

1973 2 14 0.575

1973 2 15 0.585

1973 2 16 0.641

1973 2 17 0.540

1973 2 18 0.354

1973 2 19 0.423

1973 2 20 0.568

1973 2 21 0.796

1973 2 22 0.737

1973 2 23 0.521

1973 2 24 0.751

1973 2 25 0.877

1973 2 26 1.005

1973 2 27 1.025

1973 2 28 1.073

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This is why I'm looking at the NAO! Is that not meteorology? Wow.

That is the truth, it's not making things too simple. There is plenty of research to back this up. Maybe you don't understand what a negative NAO actually is?

Now that was uncalled for, of course I understand what a - NAO is. I have been in the professional forecasting business for over 30 years. What is your background? I also understand perfectly that it is vastly preferable to have one in place in order to get say a week of cold weather here, and most snow storms have occurred in that pattern. However, there seems to be a lot of "no negative NAO, impossible to get snow and/or cold," type posts- that is simply not always true. Using only one index in a system as incredibly complex as the earth's atmosphere is way too simplistic. It is only one tool in the toolbox.

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I absolutely never said anything about snow - I said sustained cold. How everyone is getting that I said you can't get snow with a positive NAO is beyond me - please enlighten me if you so desire. I showed a web page that even illustrated you can get *some* snow days with a positve NAO and a La Nina. I'm talking about week long, reinforcing cold and parent highs that stay locked over New England for days on end like last year.

We don't want that unless the snow comes first. Too much cold and it's too dry generally.

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We weren't talking about snow! I said sustained cold, it was in the 60s the day before the February storm!!! You obviously don't know how to stay on topic, and you are 100% incorrect about the daily nao values. But carry on.

Feb. 1973 (days leading up to the storm): 2/1/1973 -3.2 2/2/1973 -19 2/3/1973 -1.7 2/4/1973 6.6

Your NAO numbers are all out of whack (-19, +6.6) - show us the link to those values.

OK, you are correct that it wasn't a sustained period of cold before or after the Feb 1973 storm...but it was an arctic boundary that moved south due to a cold vortex in SE Canada that provided the cold air without a -NAO

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NOT true...the rest of this post was fine. Is it better to have a West Based -NAO? ABSOLUTELY. But it is NOT the only way to get sustained cold in the SE.

Guys, it's called a positive NAO. I don't care what meteorologist on this board or anywhere else tries to talk about this block or that, if you don't have a negative NAO block you are not going to get sustained southeastern US cold, and any winter weather threats will require perfect timing. I've observed time and time again when the realist on these boards get shunted for saying such as this, but it's reality so fire away.

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Well I disagree with this. It was very warm prior to the Blizzard of 1993 and we still got plastered. You don't need a period of cold prior to a storm for snow to accumulate if it's heavy.

True Marietta. A strong, closed upper low, or rapidly deepening upper low can provide enough cold air.....but that was not the setup in Feb 1973 or Jan 1988

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Folks,

I see many folks here are in need of therapy. I have some good news, the doctor is in the house to try to help and I definitely don't mean the Doc (Euro).

1) I looked back at major KATL S/IP (3.5"+) weak La Nina storms back to the late 1880's. They took place on these dates:

1/28, 2/11-12, 2/11-12, and 2/15-16 from three different winters (1904, 1899, and 1895). Also, 2.3" fell on 2/29/1968.

2) Also, of the 18 weak La Nina's, a respectable four had both extreme cold (single digit or lower lows/multiple very cold days with highs of 24F or lower!) and the coldest of the season in early Feb. at KATL (1996, 1951, 1899, and 1895): Furthermore, regarding the other 14, two others (1968 and 1963) had very cold Feb.'s overall. In addition, 2/23/1939 was the coldest morning of that winter at KATL.

In summary, a very respectable 8 of the 18 weak La Ninas resulted in some interesting to very exciting wx in Atlanta either during very late Jan. or Feb. So, there remains reason for hope, especially if the NAO and/or AO would go negative.There wil be no charge for this session. Have a nice day!

Devils Advocate here....

We are perilously close to being in a moderate La Nina, what happens if you adjust these numbers based on a weak/moderate La Nina? Even the CPC says we are in a weak-moderate Nina, staying on the fence about what to actually call it. Say take La Nina's that were between -.5 and -1.5? Or some other range to show that we are borderline?

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OK folks, enough of the pie fight. Back to the current situation, the new 240 hr Euro does looks like we MAY be getting into a -NAO, plus all of Canada is below normal heights. In the SE on this run, we only really have a couple of days of milder weather and then another front comes through, so really out of the 10 days only two are not at least chilly. For the cold lovers at least this certainly is not a blowtorch pattern....

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