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SE Mid-Long Range Discussion II


strongwxnc

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already as early as 120 hours there are big differences btwn the models. The ecmwf has the cold air coming down strongly and arrives at the Apps by Thursday morning, with -10 to -12 back in Ark. and Missouri. The southwest cutoff is well off the Calif. coast. though.

Crazy dfferent!

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Back in november I was very pessimistic about this winter and I was accused of jumping to conclusions and being a weenie and it seems so far this winter is playing out just liker I feared. This was the first winter i can remember in quite sometime where I was truly down on the chances of a decent winter or any winter weather events. I thought it would be bad and so far it's been about as bad as it can get for much of he country. I'm don't normally come to such negative conclusions before it even starts. For example, Last year for example, despite all the forecasts for really warm weather, I was really optimistic and thought it would be a good winter and I was right.

I pray that feb is different but I'm still not optimistic. Hopefully I'm wrong.

Well, after the last few winters you've had, I'd expect you'd enjoy a nice balmy winter for a change, lol. I would hate for you to suffer from snow glut :) And with a few moderations in the high department, next weekends affair could supply us with some nice icy over running for a change :)

I'm more encouraged than ever that I'll see a nice suppressed sleet storm to make me very happy this winter. I'm seeing shots of cold, I'm seeing gulf systems and I'm seeing suppression. Some of my favorite ingredients for a nice surprise pudding, lol. T

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The PNA is our friend on this run?

at this point I wouldn't trust them with anything, but the trend is just for an amplified pattern everywhere. The troughs and ridges have a huge north-south gradient. I'm sure next run will look much different anyway. Nothing really consistent.

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a little snow in Al, Fl coast around 204 hour, which goes across northern Fl by 210. This run has a sharp s/w dropping into the lower Miss. valley. Kind of pointless to be looking at the models lately beyond 72 hours though.

Wouldn't that be something. This would certainly be a winter to remember that the first snow of the SE for 2012 would be SAV to UST

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at this point I wouldn't trust them with anything, but the trend is just for an amplified pattern everywhere. The troughs and ridges have a huge north-south gradient. I'm sure next run will look much different anyway. Nothing really consistent.

That was interesting run, kind of in shock, probably just a fluke but nice to see...shows why we need that ridge in the west.

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well this run didnt' end up as far off from its previous run as I thought it would. And by day 10 for NC and the east coast it's not that bad of a setup. But its day 10. Atleast there's good blocking still showing up in western Alaska, and strong HP most of Canada, even the Great Lakes region. I'm sure things will change again. I read a paper about blocking that stated thats the hardest part for numerical modeling because of the equations or something, but once the blocking is formed, they handle the flow much better. Its going to be a long week.

00z:

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12z:

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The GFS ensemble members are generally colder than the Op and the CMC continues its colder trend as well, I think it will be colder than the latest Op GFS shows. After that, the GFS ensemble mean shows the AK block a bit too far west for my taste and no signs of a negative NAO- the Canada PV as a result is pretty far north well north of Hudson's Bay. The ridge is still present along the West Coast so it looks chilly but signs of a massive cold air dump all the way to us are faint.

Good post here Cheez. Yeah, without north atlantic blocking, we really would like to see the AK ridge shoot up in eastern AK as opposed to west of there.

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should have added that same paper showed that Alaskan blocks have high precip. pattern in southern California and the Southeast and Ohio Valley during the eleven day period of the block. Showed the temps cold in nw to southern plains.This one so far doesn't look like a typical Alaskan block yet, the wavelengths are so amplified which gives room to more longwaves.

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Posted: 9:44 a.m. Saturday, Jan. 7, 2012

Kirk Mellish's Weather Commentary

More big ticket weather on the way

On the weather menu: another taste of spring, another risk of strong thunderstorms and/or heavy rain, and another cold wave or more.

Now is the winter of our content. Does not quite have the same ring as the famous line from Shakespeare in Richard the III. But the difference between last winter and this winter is truly “A Tale of Two Cities”, or a tale of two quite different winters in the same city here in Atlanta. This winter has so far had little of the snow and cold made famous by the writings of Charles Dickens and made the first half of last winter tough in the south. Last year a White Christmas in Atlanta, this year Christmas was preceded by 6 tornadoes in the metro region.

It is a great lesson in the vagaries of Mother Nature. This winter, like last winter the South Pacific Ocean is in a condition known as La Nina with colder than normal surface water. But the previous La Nina was strong this one weak. Its mirror opposite El Nino is when South Pacific waters are warmer than normal.

These patterns come and go at 3 to 7 year intervals and impact the global jet stream and thus average weather for months at a time. However, it is just one factor controlling the weather and climate. Therefore, no two El Nino or La Nina seasons are ever exactly the same. In making long-range forecasts for a season ahead, they tell us how the odds are tilted but do not guarantee the usual weather will occur.

 

Last winter a negative AO or Arctic Oscillation and Greenland Blocking (GB) accompanied La Nina for an 8-12 week period with a -AO/NAO. No repeat thus far this winter. The AO measures the magnitude of cold air in the Arctic. When this value is positive the coldest air is locked up near the Arctic Circle leaving the US with normal to above normal temperatures. But when it goes negative the polar air is released and drives south into parts of America.

The Greenland Block (negative NAO or North Atlantic Oscillation) is a bulge in the jet stream near Greenland and it forces the jet stream to dip south driving cold air into the eastern US and often providing energy for winter storms. This combination is what caused the cold and snow of last winter for an unprecedented La Nina pattern. It’s absence thus far this year made November and December mostly mild. “Blocking” in the jet stream allows cold air to “lock-in” or block-in for long periods. In the absence of a -AO and blocking -NAO GB cold snaps come and go. Thus far this winter La Nina impacts have been muted by the MJO recycling into warm phases accompanied by a +WPO/+EPO in the West and North Pacific Ocean which are also warmer influences with a "firehose" Pacific Sub-Polar Jet Stream.

The La Nina favors a mild winter on average going forward. But there are numerous signals pointing to a significant pattern change that will open the window of opportunity for more sustained cold if not cold and snow as we move deeper into January. At least the pattern will be MORE FAVORABLE for this to occur with one shot as early as next weekend, and more to follow for the second half of January and early February.

This is because a sudden stratospheric warming SSW event has been observed over the Arctic and West Canada and forecast by the models, along with a change in the forecast AO and NAO/Greenland Blocking. The QBO is now more easterly and the MJO is forecast to move toward more winter like phases in the weeks ahead. At the same time low pressure over AK is transitioning to High Pressure with a resultant jet stream connection to Siberia underneath the SSW with a block around 70 degrees North 70 degrees East helping to change the PNA to a ridge west trough east configuration. When such pattern changes occur as a result of all these signals they typically last from 4 to 6 weeks before breaking down. But what is interesting is how these jet stream induced weather regimes can flip on a dime. The rubber band theory of weather holds… the longer you stretch an extreme the more likely it will snap to the other extreme.

When, how strong, and for how long this occurs will determine if Old Man Winter awakes from his slumber for more than a few days at a time as we’ve seen so far. It probably will since we usually see at least one abrupt pattern change each winter. That does not mean we repeat last winter, it just means we don’t coast through the whole season on easy street. Obviously snow and ice are not a certainty even when it turns bitter cold as we’ve already witnessed.

This article is from Kirt Mellish. I thought it was very informative.

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Euro ensembles are just what I expected- colder than the GFS but not nearly as cold as the Op run- the biggest difference is the amplitude of the western ridge- the Op is a big outlier with almost all members quite a bit flatter.

Yes, the Euro operational is a good bit taller with the western NA ridge in the 144-216 range. In fact, it is taller than just about every ensemble member.

However, the ensemble mean is in good agreement with the operational in building the big Alaskan ridge 204-240.

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How close are the Euro and GFS ensembles? They have to agree at some point. I'm tired of this roller coaster! If I was certain the pattern was going to stink like earlier in the season, I wouldn't be spending so much time getting my hopes up and then being disappointed the next day.

Model flip flopping is a good sign the pattern is going to change from what we've seen over the last 2 months. Sit back and enjoy the show.

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Model flip flopping is a good sign the pattern is going to change from what we've seen over the last 2 months. Sit back and enjoy the show.

Agree. Whatever follows is bound to be substantially better than what we've had since early November. Hopefully our -NAO will return though it's been like pulling teeth to have the models hold on to one. The rising confidence of Arctic blocking gives me hope.

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