2013 Fall Medium Range Discussion

[am19psu]

There is strong model consensus for a major Plains/Midwest winter storm next week. The progs for the shortwave around D6 in the SW are pretty amazing. There will be a ton of baroclinic energy available for this thing to explosively deepen once it connects with the inflow off the Gulf of Mexico. B_I will be going nuts over the DMC.

[donsutherland1]

I think Dec. 1950 turned out very cold around DC. Wonder how that month went from very mild start.

The cold pattern set in on the 10th. After December 9, 17/22 days had below normal anomalies and 15/22 days had highs below 40°.

[donsutherland1]

There is strong model consensus for a major Plains/Midwest winter storm next week. The progs for the shortwave around D6 in the SW are pretty amazing. There will be a ton of baroclinic energy available for this thing to explosively deepen once it connects with the inflow off the Gulf of Mexico. B_I will be going nuts over the DMC.

This seems to be an exciting event. It's quite amazing how strong the model agreement is right now.

[Srain]

This seems to be an exciting event. It's quite amazing how strong the model agreement is right now.

It does appear that way Don. While folks along the I-95 Corridor experience above normal temps and little in the way of weather as heights build across the EC, we here in the Central US certainly are hoping for this pattern change. Records highs across Texas and the Plains have been common and the threat of some badly needed moisture across the drought parched Rockies/Plains are very encouraging.

[am19psu]

It does appear that way Don. While folks along the I-95 Corridor experience above normal temps and little in the way of weather as heights build across the EC, we here in the Central US certainly are hoping for this pattern change. Records highs across Texas and the Plains have been common and the threat of some badly needed moisture across the drought parched Rockies/Plains are very encouraging.

We very well could put down a foot plus over the worst of the drought areas

[tacoman25]

Although some of the guidance has backed off on the pattern change toward a generally colder than normal period for the last 10-14 days of December (12/18-31) with a transition beginning at some point during the second week of the month, the ensembles were in good agreement that the Arctic Oscillation is forecast to drop to severely negative levels (-3.000 or below).

Below are three scenarios for the December 10-31, 1950-2011 timeframe when the AO was -3.000 or below and the ENSO Region 3.4 anomaly was 0.00°C to +0.70°C for different PNA figures.

Given the ensemble guidance and the current PDO-, I believe the PNA will predominantly be < 0. Hence, either the second or third scenarios is probably likely to play out for the closing 10-14 days of December if the AO goes severely negative. Severe cold, though, appears to be unlikely given the pronounced warmth in the Arctic and possible EPO+ through at least December 17.

Good analysis, Don, and I think your thoughts regarding the PNA/AO are spot on. I'm not sure the "warmth" in the Arctic would be much of a factor, though, as there has still been a lot of very cold air in Alaska and northern Canada recently. Fairbanks, for example, just saw their 4th coldest November on record, and have been well below normal since mid October. In fact, through the first few days of December they are running about 30 degrees below normal and that looks to continue for the foreseeable future. So there is definitely some very cold air up north, and if we get a -EPO especially, the CONUS could see a significant Arctic outbreak later this month.

[A-L-E-K]

Good analysis, Don, and I think your thoughts regarding the PNA/AO are spot on. I'm not sure the "warmth" in the Arctic would be much of a factor, though, as there has still been a lot of very cold air in Alaska and northern Canada recently. Fairbanks, for example, just saw their 4th coldest November on record, and have been well below normal since mid October. In fact, through the first few days of December they are running about 30 degrees below normal and that looks to continue for the foreseeable future. So there is definitely some very cold air up north, and if we get a -EPO especially, the CONUS could see a significant Arctic outbreak later this month.

Fairbanks isn't in the artic.

[donsutherland1]

Good analysis, Don, and I think your thoughts regarding the PNA/AO are spot on. I'm not sure the "warmth" in the Arctic would be much of a factor, though, as there has still been a lot of very cold air in Alaska and northern Canada recently. Fairbanks, for example, just saw their 4th coldest November on record, and have been well below normal since mid October. In fact, through the first few days of December they are running about 30 degrees below normal and that looks to continue for the foreseeable future. So there is definitely some very cold air up north, and if we get a -EPO especially, the CONUS could see a significant Arctic outbreak later this month.

My point is that because Arctic cold is not expansive and the EPO remains persistently positive (both factors), it does not appear that the CONUS will see a severe Arctic outbreak this month. That is unlike parts of Western Europe and Alaska, which remain locked in the proverbial freezer. Of course, that thought only concerns December, not the winter as a whole. It's far too soon for me to suggest that the CONUS won't experience severe cold at some point this winter given my thoughts of a predominatly negative Arctic Oscillation.

P.S. I had mentioned the EPO in #108. I just realize that I didn't include it in the message to which you replied.

[usedtobe]

Don, nice post. I monthly analog that has a negative NAO and rPNA that was warm over the east pretty much like we've been experiencing the last several days. I posted it in the Mid Atlantic forum medium range discussion. The latter half of Dec is a tricky period. Personally I think your third scenario is the most likely of the three as I think we are more likely to see average temps than colder than normal ones. If the NAO does shift west like what is being shown on the last panel of the latest operational GFS, then a colder scenario would be possible. The models have been more aggressive with such a shift than so far has occurred which I don't think is that unusual. Most high latitude blocks do shift west so eventually I do think the pattern gets better. I have little confidence that I have the ability to time such a change more than a couple of weeks in advance.

[tacoman25]

Fairbanks isn't in the artic.

It's pretty darn close. Point being, it's not like there isn't cold air up north to draw from. There is and has been a lot of very cold air around Alaska and in northern Canada. So if we get the right blocking pattern (-AO/-EPO or -AO/-NAO), I don't see that being a mitigating issue for severe cold in the CONUS later this month.

[am19psu]

It's pretty darn close. Point being, it's not like there isn't cold air up north to draw from. There is and has been a lot of very cold air around Alaska and in northern Canada. So if we get the right blocking pattern (-AO/-EPO or -AO/-NAO), I don't see that being a mitigating issue for severe cold in the CONUS.

That bottled up cold air is a big part of the winter storm forecast for next week in the Plains and Midwest. Without the supply of cold air, there isn't enough baroclinicity to spin up the shortwave over the SW.

[tacoman25]

My point is that because Arctic cold is not expansive and the EPO remains persistently positive (both factors), it does not appear that the CONUS will see a severe Arctic outbreak this month. That is unlike parts of Western Europe and Alaska, which remain locked in the proverbial freezer. Of course, that thought only concerns December, not the winter as a whole. It's far too soon for me to suggest that the CONUS won't experience severe cold at some point this winter given my thoughts of a predominatly negative Arctic Oscillation.

P.S. I had mentioned the EPO in #108. I just realize that I didn't include it in the message to which you replied.

Well, I certainly agree with the EPO part. It's always a significant player for lower 48 cold, especially if you don't have a west-based -NAO.

I just don't see the temperatures up north being nearly as much of a factor. The Arctic circle itself may be warmer than normal with higher heights (-AO), but there is plenty of very cold air in the NH right now. Not just Alaska/northern Canada....look at northern Asia right now too. Absolutely frigid. I think the early/extensive NH snowcover we saw this fall may have played a role.

[Isotherm]

To illustrate your point Taco -- most of the northern hemisphere throughout the mid latitudes is very cold right now. As seems to be usual these days, the good old US of A is really the only region torching big time:

Well, I certainly agree with the EPO part. It's always a significant player for lower 48 cold, especially if you don't have a west-based -NAO.

I just don't see the temperatures up north being nearly as much of a factor. The Arctic circle itself may be warmer than normal with higher heights (-AO), but there is plenty of very cold air in the NH right now. Not just Alaska/northern Canada....look at northern Asia right now too. Absolutely frigid. I think the early/extensive NH snowcover we saw this fall may have played a role.

[Isotherm]

A closer view of month to date anomalies indicates severe cold waiting in the wings, just N of the US/Canadian border. I think the Plains/U-Mid-west are likely to see some pretty substantial cold by mid/late month. Northeast US is a tougher forecast depending upon NAO magnitude and orientation.

[Isotherm]

Take a look at that differential b/t global temp anomaly and CONUS temp anomaly on the first map I posted for Dec 1-4.

Global: +0.1c

CONUS: +6.8C

Yeah - we're torching. US is significantly warmer than most of the globe right now.

[donsutherland1]

Ottawa sets December Record High...

At 1 pm, Ottawa had a temperature of 17.6°C (63.7°F). That broke the daily record of 13.9°C (57.0°F) set in 1982 and the monthly record of 16.3°C (61.3°F) set on December 3, 1982.

[tacoman25]

A closer view of month to date anomalies indicates severe cold waiting in the wings, just N of the US/Canadian border. I think the Plains/U-Mid-west are likely to see some pretty substantial cold by mid/late month. Northeast US is a tougher forecast depending upon NAO magnitude and orientation.

Agreed. Even in the near term, much colder air will begin moving into the northern tier days 3-6. The overall pattern is already changing. It may take a while before notably colder air reaches much of the east coast, though.

[WEATHER53]

The cold pattern set in on the 10th. After December 9, 17/22 days had below normal anomalies and 15/22 days had highs below 40°.

So do you think this TX storm next week might move east, off midatlantic coast and bring down a similar onset of cold?

[donsutherland1]

So do you think this TX storm next week might move east, off midatlantic coast and bring down a similar onset of cold?

I think that storm will mark the beginning of the pattern change to colder weather, first out in the Plains then eastward. The transition probably won't be completed until sometime during the third week in December.

I previously referenced the current period of excessive warmth to the December 7-9, 1980 timeframe. Using December 8th as the mid-point, Washington, DC didn't enter into a persistent period of below normal temperatures until December 20th. That pattern change was driven by a persistently positive PNA. The one I'm thinking will occur will be driven by the AO, at a time when the PNA is predominantly negative, so it might take a little longer to progress. My best guess is that the cold will become more sustained in about 14 +/- a few days from today. Some additional exceptional warmth might occur before that transition is completed. There might also be some transient cold shots prior to then, but nothing too significant or long-lasting.

[Ottawa Blizzard]

This may seem off-topic, but it does in fact have something to do with the medium range discussion. DT (ruggieweather on the old forums) posted an interesting article yesterday in which he takes a swipe at Joe Bastardi's hyping of upcoming severe cold, without actually naming him. It's actually quite funny. I really appreciate the outlooks posted by Don on this forum as he analyzes the pattern in a clear manner without any hype.

Here is a link to the article.

http://www.wxrisk.com/2012/12/major-winter-storm-for-plains-upper-miss-valley-dec-9-10/

[donsutherland1]

This may seem off-topic, but it does in fact have something to do with the medium range discussion. DT (ruggieweather on the old forums) posted an interesting article yesterday in which he takes a swipe at Joe Bastardi's hyping of upcoming severe cold, without actually naming him. It's actually quite funny. I really appreciate the outlooks posted by Don on this forum as he analyzes the pattern in a clear manner without any hype.

Here is a link to the article.

http://www.wxrisk.co...alley-dec-9-10/

Thanks for the kind words.

FYI, DT (Dave Tolleris) is not Ruggieweather. They are two different people.

[Ottawa Blizzard]

Thanks for the kind words.

FYI, DT (Dave Tolleris) is not Ruggieweather. They are two different people.

, my mistake!

[donsutherland1]

Yesterday's record highs in Toronto and Ottawa:

Ottawa: 17.9°C (64.2°F) broke the monthly record of 16.3°C (61.3°F) set on December 3, 1982

Toronto: 16.7°C (62.1°F) broke the daily record of 15.9°C (60.6°F) set in 1998

[am19psu]

The Euro op has trended much weaker with the early week system for the Plains/Midwest. The GFS op has a strong system, but it's delayed and does not really start churning until it reached Indianapolis on Monday morning. The Euro ensemble actually looks closer to the GFS op than the Euro op. I still feel confident that there will a formidable storm next week, but there is high uncertainty as to where it ends up.

[The_Global_Warmer]

It's pretty darn close. Point being, it's not like there isn't cold air up north to draw from. There is and has been a lot of very cold air around Alaska and in northern Canada. So if we get the right blocking pattern (-AO/-EPO or -AO/-NAO), I don't see that being a mitigating issue for severe cold in the CONUS later this month.

Good analysis, Don, and I think your thoughts regarding the PNA/AO are spot on. I'm not sure the "warmth" in the Arctic would be much of a factor, though, as there has still been a lot of very cold air in Alaska and northern Canada recently. Fairbanks, for example, just saw their 4th coldest November on record, and have been well below normal since mid October. In fact, through the first few days of December they are running about 30 degrees below normal and that looks to continue for the foreseeable future. So there is definitely some very cold air up north, and if we get a -EPO especially, the CONUS could see a significant Arctic outbreak later this month.

I don't think it is either. We haven't seen it stop winter from happening or more snow in some spot's than year's when it has been colder in the past. But we have seen a downturn in record cold/long severe cold snaps.

The below animation is rudimentary, doesn't cover pre-1950 when we did have warmer periods before then. It's not to make claims outside of the chance a warming North can have an effect on our chances for or duration of and bottom out of "severe cold".

For December only. We see the 1950-1980 period was colder over a huge region of the Northern Hemisphere, as we go poleward the changes are the largest.

Siberia hasn't warmed much in that period vs the other cold regions and the arctic. But we can see the Canadian side has warmed quite a bit more and the deep cold depository over the Canadian Archipelago from period 1 to the final period has warmed quite a bit. when cold out breaks come rolling South, I can't see how the initial air-mass being warmer at multiple points along the roadway down doesn't cause us to have less prolonged cold or less severe cold.

2010-2011(DEC) we can see the cold pool over North America into the arctic was warm vs climo and 1950-1980. This is in Celsius. But this really shows how much warmer below 800MB towards the Surface and as you get to us the effect dwindles quite a bit. But

It wasn't as pronounced from 2002-2011 for December.

Them we go back to 1981-1997. We can see the initial warming taking place up North. But not near as an effect as in the last decade.

I am not saying we can't have arctic out breaks and such. But there has been a major decline in the longevity and strength of the cold getting established, even during pretty ideal conditions.

I think we need to take that into consideration in forecasting cold and adjusting for the warming that has taken place during the 30 yr climo throwing it off balance quite a bit. Until it changes back to something we had before, but as it stands we have some pretty good reasons when using analogs to temper them if they are pre-2000 for sure.

[Clinch Leatherwood]

I don't think it is either. We haven't seen it stop winter from happening or more snow in some spot's than year's when it has been colder in the past. But we have seen a downturn in record cold/long severe cold snaps.

The below animation is rudimentary, doesn't cover pre-1950 when we did have warmer periods before then. It's not to make claims outside of the chance a warming North can have an effect on our chances for or duration of and bottom out of "severe cold".

For December only. We see the 1950-1980 period was colder over a huge region of the Northern Hemisphere, as we go poleward the changes are the largest.

Siberia hasn't warmed much in that period vs the other cold regions and the arctic. But we can see the Canadian side has warmed quite a bit more and the deep cold depository over the Canadian Archipelago from period 1 to the final period has warmed quite a bit. when cold out breaks come rolling South, I can't see how the initial air-mass being warmer at multiple points along the roadway down doesn't cause us to have less prolonged cold or less severe cold.

2010-2011(DEC) we can see the cold pool over North America into the arctic was warm vs climo and 1950-1980. This is in Celsius. But this really shows how much warmer below 800MB towards the Surface and as you get to us the effect dwindles quite a bit. But

It wasn't as pronounced from 2002-2011 for December.

Them we go back to 1981-1997. We can see the initial warming taking place up North. But not near as an effect as in the last decade.

I am not saying we can't have arctic out breaks and such. But there has been a major decline in the longevity and strength of the cold getting established, even during pretty ideal conditions.

I think we need to take that into consideration in forecasting cold and adjusting for the warming that has taken place during the 30 yr climo throwing it off balance quite a bit. Until it changes back to something we had before, but as it stands we have some pretty good reasons when using analogs to temper them if they are pre-2000 for sure.

Outstanding points all around. Analogs are still useful but we all have to realize times are a changing and particularly the underlying conditions. That first animation paints a clear picture.

[NEOH]

Outstanding points all around. Analogs are still useful but we all have to realize times are a changing and particularly the underlying conditions. That first animation paints a clear picture.

Tell the folks in Europe that arctic outbreaks are becoming more limited and not as strong. December is rockin in Europe... just not our side of the pond. A lot like last year when hundreds died from the cold.

[scottmartin49]

Tell the folks in Europe that arctic outbreaks are becoming more limited and not as strong. December is rockin in Europe... just not our side of the pond. A lot like last year when hundreds died from the cold.

As Arctic ice becomes more transient it loses the effect of sustaining continental cold. Eurasia being the greater land mass, it retains more, with periods of -AO releasing same.

More and colder outbreaks in Eurasia, fewer in North America. My own theory, feel free to disagree!

[wxmx]

There's a decent pool of very cold air over Alaska and NW Canada, so the potential is there and this has nothing to do with climo. -AO increases the probability of cross polar flow, which hasn't really happened, but there's still that pool of homegrown cold air. We are not that far from a severe cold outbreak, a period of good -EPO and amplification over the CONUS (even without strong amplification) and we'll be talking about a strong cold snap. It's nothing like last winter, and the cold dam is rather fragile at the moment.

[The_Global_Warmer]

Tell the folks in Europe that arctic outbreaks are becoming more limited and not as strong. December is rockin in Europe... just not our side of the pond. A lot like last year when hundreds died from the cold.

Your right, Europe has seen some big cold snaps the last few Winters. But this was more in reference to severe cold. I doubt they are reaching wide spread huge deep cold anomaly's.

Many cities in the USA can't reach within 10-20F of there coldest winter temps since the mid 90s. That is what is mean't by depth of cold. Nor those huge monthly anomaly's.