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Pattern Discussion 12/15 and beyond


ORH_wxman

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How do the AO/NAO look Scott?

It weakens considerably, but still a little ridging into Greenland after d10. The big thing I see is models trying to build a ridge near and north of AK. I think that is important to follow because that will help ensure cross polar flow. We still may have a -PNA, but better to fight that will cold Canadian air.

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It weakens considerably, but still a little ridging into Greenland after d10. The big thing I see is models trying to build a ridge near and north of AK. I think that is important to follow because that will help ensure cross polar flow. We still may have a -PNA, but better to fight that will cold Canadian air.

I agree. With this still being a week out I think the ridging development in AK is important. If these models do verify though with a cutoff event it's definitely going to be interesting.

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Rain all the way to Nome, Alaska at the end of the 00z GFS tonight.

Good signs for LR potential there. Things will eventually break our way.

Shows about 1" total snow accumulation for SNE through 384. Ugly but its probably only worth looking at the first 144.

Lets hope we can pull of an inch the days in and around Christmas. Even mood flakes would be nice.

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Pattern Change Now Evolving as Panic of December '12 Rises...

The storm that brought record daily snowfall to Minneapolis-St. Paul commenced a sequence of events that is leading to a pattern change. That sequence of events will likely include several systems (one underway and one or two others in coming days) that will be noted more for wet than white in the East. Afterward, the last 10-14 days (14 days for the Plains States and 10 days for the East Coast) could see generally cooler than normal weather.

The rising panic that Winter 2012-13 is becoming a repeat of the non-Winter of 2011-12 has resulted for a large gap between the actual pattern change that is now imminent and expectations. The pattern change was likely to be slow with a fairly lengthy transition before sustained colder weather set in. Given the combination of an EPO+, PNA-, and persistent Arctic warmth, severe cold was not very likely for much or all of December. Expectations were for prolonged and deep cold to set in with the potential for excessive snows. That gap was unsustainable, hence the rising panic.

If one steps back to take a look at the non-Winter of 2011-12, one finds:

1. A powerful AO+ regime predominated in December.

2. The long-range guidance and analog cases were unrelenting with their warm idea.

3. The subtropical jet was quiet.

To date, one finds:

1. A persistent AO- regime.

The AO has now been negative for 22 consecutive days. It is likely to remain predominantly negative for the remainder of the month as per the ensemble guidance and also historic cases. Notable long-lived blocks that developed in the 11/20-12/10 timeframe have typically been long-lived. Put another way, the blockiness that was present in mid-Autumn reasserted itself during the winter.

Recent examples include the blocking regimes of 2009-10 and 2010-11. The following severe blocking episodes (minimum AO value of -3.000 or below) began in late November/early December (11/20-12/10) following a blocky October (monthly AO of -025 or below):

December 7, 1966-January 11, 1967: 36 days

December 7, 1981-January 12, 1982: 37 days

November 29, 2009-January 15, 2010: 48 days

December 3, 2010-January 15, 2011: 44 days

All four of those cases saw the January AO average < 0. KU snowstorms occurred during the winter in 1966-67, 2009-10, and 2010-11. A KU snowstorm occurred during the spring in 1981-82,

2. The long-range guidance has been anything like last winter. In fact, the latest CFSv2 guidance has trended toward widespread cold to begin January and a generally cold month across much of North America. With the PNA having been negative for 41 consecutive days, both historic cases and some ensemble members suggest that it could go positive near or during January. Once that happens, the dam that has kept some of the coldest air bottled up in Alaska and westward could break and a genuine prospect of at least an outbreak of severe cold could develop.

Below are the latest CFSv2 weekly (weeks 3 and 4) and monthly (January 2013) forecasts:

CFSv212152012weekly.jpg

CFSv212162012Monthly.jpg

3. The SOI has recently gone negative. December 10-12 had values below -40. The 30-day moving average has gone negative and the 90-day moving average is near 0. Often such developments suggest a stronger subtropical jet. Hence, there is a possibility that the closing 10 days of December and perhaps the opening 10 days of January could be stormy.

In sum, the gradual pattern change is unfolding. At first, the cold will be a little more impressive than seasonal cold. Storminess could increase as well. The possibility of an outbreak of severe cold could increase after the start of January, as the PNA heads to more neutral values,and especially if it goes positive. All said, even as the first two weeks of December have been sufficiently warm to rekindle nightmares of the non-Winter of 2011-12, there are big differences that argue against a repeat.

Delayed,but not denied
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My best advice is to stop looking for 2009-10, 2010-11 type of results in the long range. Anyone trying to sell you "blockbuster" snow and cold is simply BSing you. I am now completely confident that we don't end December with an all out torch but with a classic Gradient Pattern. Glad to see the Midwest looking to be the prime area since that's what the data actually suggested 10-15 days ago.

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My best advice is to stop looking for 2009-10, 2010-11 type of results in the long range. Anyone trying to sell you "blockbuster" snow and cold is simply BSing you. I am now completely confident that we don't end December with an all out torch but with a classic Gradient Pattern. Glad to see the Midwest looking to be the prime area since that's what the data actually suggested 10-15 days ago.

Hopefully January comes through.

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Euro's got a nice widespread light snow event for all of Sne this weekend..with the ULL and inverted trof. Doubt it verifies..but our last hope for a white Xmas

I wish that little western extension/redevelopment would form closer to the Cape than the Gulf of Maine. Otherwise it may just be ski country/CNE/NNE that cash in. But I like the potential and there's a good shot we'll at least have some mood flakes around here xmas weekend.

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Hopefully January comes through.

Gradient patterns can come through for your area. Currently it is not and I agree that it is a bummer we don't have cold air around. Really this blocking is a joke. A legit blocking pattern in the polar fields producing those kind of h5 anomalies that are matching to "2010" on the CPC site is NOT what we are dealing with.

Cold comes in just in time for the holidays with an active southern stream. Things will continue to get colder and snowier in the Plains for sure and ultimately that gradient will come way south in New England.

I'm even starting to think I'll see snow down this way between Christmas and New Years.

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Gradient patterns can come through for your area. Currently it is not and I agree that it is a bummer we don't have cold air around. Really this blocking is a joke. A legit blocking pattern in the polar fields producing those kind of h5 anomalies that are matching to "2010" on the CPC site is NOT what we are dealing with.

Cold comes in just in time for the holidays with an active southern stream. Things will continue to get colder and snowier in the Plains for sure and ultimately that gradient will come way south in New England.

I'm even starting to think I'll see snow down this way between Christmas and New Years.

HM roughly speaking where are you? I see you reference your area but I don't think a lot of us know generally what region you're speaking about. Thanks for all the great posts.

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HM roughly speaking where are you? I see you reference your area but I don't think a lot of us know generally what region you're speaking about. Thanks for all the great posts.

He's in NJ...Princeton I believe.

Thanks Saki. Jerry I moved to Mount Laurel which is further south into Burlington County. But yes, I'm down into NJ for everyone that doesn't know but I like hanging out with y'all.

I'm not thinking big snow or anything (yet) for my area but perhaps something widespread before a possible changeover??!!?

My worry is the Midwest storm coming up at the end of the week ends up moving quicker / further ENE, allowing the next wave to amplify freely. We'll see..

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January, January January....

Well, this is going to be an interesting ride because we'll have the cold dumping into the western half of the USA while the old blocking regime changes and possibly manifests as a -EPO and a new -NAO east. The tropical forcing will possibly ignite a PNA response mid-month but I also don't want to rush this end of things. For now, it still looks solidly RNA into early January. Some long range data, including GCMs and tropical forcing-based modeling, suggests this PNA switchover second week. We'll see...new data arrives today of course.

Finally, the stratosphere will take another jab at the polar vortex at the beginning of the New Year. Another strong wave 1 punch in the jaw coming with a significant anticyclone moving over Canada. Around that time, models have been insisting on an even stronger mid-upper level warming developing over Siberia which could be the beginnings of a possible breakdown 10-20 days after that point.

Sometime in mid to late January, the vortex will self-destruct and then we have to start talking big snow and cold.

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Thanks Saki. Jerry I moved to Mount Laurel which is further south into Burlington County. But yes, I'm down into NJ for everyone that doesn't know but I like hanging out with y'all.

I'm not thinking big snow or anything (yet) for my area but perhaps something widespread before a possible changeover??!!?

My worry is the Midwest storm coming up at the end of the week ends up moving quicker / further ENE, allowing the next wave to amplify freely. We'll see..

WooHoo!!

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WooHoo!!

LOL

I wonder if we were just beginning or in the process of peaking our -QBO wave if things would have been different in the Pacific. The advection would have been cold and the 50-10mb layer would have been a lot cooler than it is now over the equatorial regions, possibly helping the MJO activity.

Then again, the weak El Niño crapping out was the biggest disappointment. So far, the statistic of "neutral ENSO having the most MJO activity" is taking a shot. Also, Cohen's connection to our DJF temperatures currently is taking a shot but the raw AO index is not.

Edit: BTW I'm only taking a shot at Cohen because he completely dismissed the Pacific in his interview and research saying that these things do not correlate as strongly as the AO. Well, okay Cohen, but they do correlate and they do have a causal relationship. I think this December shows that perfectly. He still has the rest of the winter to get the correlation he needs.

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Well as we mentioned for several days now, the key feature IMO, is how this weenie block near and north of AK manifests itself. The euro ensembles break this off and drift it right over Santa's fanny, while trying to rebuild a positively tilted ridge into AK. This is going to be huge in fighting the -PNA. There is a weak ridge over ern Greenland, but I'm not even sure if that does much as currently modeled. The ridge in AK is huge in trying to set up cross polar fllow. There is also continued 50mb warming progged right over Canada and centered on the Davis Straits too. I don't know how much this will have an effect on the troposphere below via conduction or top down, but as modeled..very impressive warming.

What could go wrong? Well the AK ridge may go poof or weaken as we head forward. That reduces cross polar flow and the potential for more cutters. However, for here specifically, I don't see a reason to favor that right now. I think this pattern for SNE plus deeper into winter climo will help us out.

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Well as we mentioned for several days now, the key feature IMO, is how this weenie block near and north of AK manifests itself. The euro ensembles break this off and drift it right over Santa's fanny, while trying to rebuild a positively tilted ridge into AK. This is going to be huge in fighting the -PNA. There is a weak ridge over ern Greenland, but I'm not even sure if that does much as currently modeled. The ridge in AK is huge in trying to set up cross polar fllow. There is also continued 50mb warming progged right over Canada and centered on the Davis Straits too. I don't know how much this will have an effect on the troposphere below via conduction or top down, but as modeled..very impressive warming.

What could go wrong? Well the AK ridge may go poof or weaken as we head forward. That reduces cross polar flow and the potential for more cutters. However, for here specifically, I don't see a reason to favor that right now. I think this pattern for SNE plus deeper into winter climo will help us out.

What are your thoughts on light snow this weekend?
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Well as we mentioned for several days now, the key feature IMO, is how this weenie block near and north of AK manifests itself. The euro ensembles break this off and drift it right over Santa's fanny, while trying to rebuild a positively tilted ridge into AK. This is going to be huge in fighting the -PNA. There is a weak ridge over ern Greenland, but I'm not even sure if that does much as currently modeled. The ridge in AK is huge in trying to set up cross polar fllow. There is also continued 50mb warming progged right over Canada and centered on the Davis Straits too. I don't know how much this will have an effect on the troposphere below via conduction or top down, but as modeled..very impressive warming.

What could go wrong? Well the AK ridge may go poof or weaken as we head forward. That reduces cross polar flow and the potential for more cutters. However, for here specifically, I don't see a reason to favor that right now. I think this pattern for SNE plus deeper into winter climo will help us out.

Interestingly, there has been an overall sharp cooling recently (still ongoing) with the strongest anomalies in the 10-5mb layer. This is in response to the oncoming +QBO in this layer but also the recent proton / geomag activity.

http://www.cpc.ncep....ALL_EQ_2012.gif

http://www.solarham.net/proton.htm (time sensitive)

Good news is that these warmings are "bottom-up" and it looks like a good one is coming just after xmas.

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