2013 Fall Medium Range Discussion

[easternsnowman]

Long range euro has not been very good as of late. The way the models are going I would'nt count on it if it's more than a few days out>

[usedtobe]

Raging +EPO, -PNA on today's long range 12Z ECMWF. You can pop an east coast trough with that pattern, but it will be transient. The zonal jet will just be too strong in the western half of the country, pushing things along.

That's pretty much my thinking plus I don't think the atlantic looks good on the GEFS ens mean.

[GaWx]

The lack of a weak El Nino and its partial correlation with a +PNA is definitely not helping right now. Also, its existence might have helped to fight the

-PDO and at least raise it to some extent.

However, this is just the beginning of met. winter. If it is going to be mild, I'd rather it be in early Dec. than later in the winter.

[easternsnowman]

philly,baltimore and dc all average around or close to 50 the next 10 days or so, it would have to be much below that to get snow anyway this time for them especially in the daytime. It's a good time to be mild now, if we're not going to snow I would rather have it in the 70's!

[Isotherm]

philly,baltimore and dc all average around or close to 50 the next 10 days or so, it would have to be much below that to get snow anyway this time for them especially in the daytime. It's a good time to be mild now, if we're not going to snow I would rather have it in the 70's!

Nope. I prefer my bugs dead at this time of year, keep the 70s way down yonder. If it's not snowing it should be cold from Nov to April.

[icebreaker5221]

Slightly OT, but does anyone know why ESRL shows the EPO as being very negative right now?

http://www.esrl.noaa.gov/psd/forecasts/teleconn/images/epo.png

Their index must just be the reverse of how I learned it (Z500'_south - Z500'_north).

[Isotherm]

The lack of a weak El Nino and its partial correlation with a +PNA is definitely not helping right now. Also, its existence might have helped to fight the

-PDO and at least raise it to some extent.

However, this is just the beginning of met. winter. If it is going to be mild, I'd rather it be in early Dec. than later in the winter.

Agree; the moderately negative -PDO/neutral ENSO combo almost guarantees we average on the negative side with the PNA this winter. However, the EPO is more important in my opinion; if we can get the high height anomalies to persist from the Aleutians northeastward through AK into Siberia, we should sustain the cross polar flow into the CONUS. Of course if we don't have that, we're completely reliant on Atlantic cooperation. 1952-53 is a good example of a winter where the -NAO/AO didn't matter because the EPO was raging positive (PNA actually near neutral). So that EPO region is crucial. I saw a couple very long range GFS runs totally breaking down the AK pos height anomaly, and if that occurs, we're done. But thankfully modelling has been variating wildy from run to run, so I wouldn't take anything beyond D 5 w/ certainty at this juncture.

[icebreaker5221]

Slightly OT, but does anyone know why ESRL shows the EPO as being very negative right now?

http://www.esrl.noaa.../images/epo.png

Their index must just be the reverse of how I learned it (Z500'_south - Z500'_north).

Come to think of it, maybe the trough is far enough south that we are in a -EPO right now. But it should almost certainly become + in a couple of days, which is why their forecasts to remain - are confusing me right now...

[Isotherm]

Slightly OT, but does anyone know why ESRL shows the EPO as being very negative right now?

http://www.esrl.noaa.../images/epo.png

Their index must just be the reverse of how I learned it (Z500'_south - Z500'_north).

I know for the EPO data set the modality is reversed (negative numbers actually indicate a positive EPO regime). But this is the fcst I look at:

http://www.esrl.noaa.gov/psd/forecasts/teleconn/images/compare.we.png

We're around neutral now, +EPO for the next week, some disagreement down the road b/t NCEP and ESRL.

[icebreaker5221]

I know for the EPO data set the modality is reversed (negative numbers actually indicate a positive EPO regime). But this is the fcst I look at:

http://www.esrl.noaa.../compare.we.png

We're around neutral now, +EPO for the next week, some disagreement down the road b/t NCEP and ESRL.

Yeah that one looks more realistic. Thanks

[donsutherland1]

Don, 1980 was the year I was born, so I have no memory of that December, but from stats I can see that it was a pretty impressive month. In fact, it was the coldest Christmas morning over recorded at both Toronto Pearson and Ottawa airport.

Brett Anderson of accuweather posted hisi nterpretation of the latest european weeklies and (according to him) they seem to show very little cold making their way into this region in December and in fact show a very mild Christmas week. Do you have access to the weeklies? What is your interpretation.

Judging from Joe Bastardi's tweets, he would seem to be in your camp, calling for sustained cold to move in weeks 3 and 4.

Ottawa Blizzard,

1980 is not as important with respect to the magnitude of cold that occurred. It's more important relative to the pattern, the period of impressive warmth that occurred in early December (12/7-9), and assessing whether or not it is likely to flip to colder. My analog pool on a week-to-week basis is dynamic. The 12/7-9/1980 timeframe was in my mix for the first 7-10 days of December; whether it will be in my next mix of analogs for the following 7-10 days remains to be seen.

Despite the Euro weeklies (which I don't receive), I believe the pattern is more likely to flip to colder than it is to remain warm. The one caveat for parts of Canada, especially in the East, would be if the current severe blocking regime turns into a December 2009 or December 2010-style superblock. I don't believe it's going to reach such a magnitude right now.

3 of the last 4 runs of the CFSv2 showed Week 4 being cold. The most recent run (11/29 weekly) showed Week 3 turning cold. The 11/30 weekly data will be available either later today or tomorrow.

[donsutherland1]

Given the current state of the PDO phase and fall patterns we have seen, I have to lean more towards Isotherm's 1968-69 analog than 1980-81 or 2002-03.

2002-03 is an analog for blocking. My thoughts from earlier in this thread were:

More recently, the AO averaged -1.514 during October. Since 1950, there were 8 prior cases during which the AO averaged -1.000 or below during October. 6/8 (75%) saw the winter AO average < 0.

From that pool of 8 cases, 4 saw the AO fall to -2.000 or below during the December 1-10 period, as is forecast to occur by a majority of ensemble members.

All four (1966, 1981, 2002, and 2009) saw the AO average < 0 during the winter. 3/4 (75%) of those winters experienced a KU snowstorm. The exception (winter 1981-82) saw a springtime KU snowstorm (the April 1982 blizzard).

My winter thoughts are based on the assumption that the winter will generally be blocky and it's one analog to support that idea.

I believe we have moved into an extended period of blocking in what will likely be a blocky winter. That the West Coast storm is analogged to 2002 (a prominent period of blocking in a blocky winter) gives me added confidence that my assumption concerning blocking could be reasonable.

I don't believe one should go beyond that relatively narrow insight. One reason to avoid going too far with 2002-03 is that during that winter the El Niño was much more impressive than this winter's ENSO (probably borderline to, at most, weak El Niño).

[donsutherland1]

Don, I think we get through the 1st two weeks of Dec and that they will be in the warm camp. Week 3 we may start seeing a change but I'm not even sold on that yet.

I think the first half of December will certainly be generally warm, with perhaps some transient cold. Sometime during the 2nd week is when I think a transition could get underway, probably later than earlier. That transitional period might last a week or so, before the cold locks in with perhaps the last 10 days of the month being cold. I'm assuming the blocking will persist for the most part. I'm not sure about any severe cold, though.

[donsutherland1]

Stronger Hints of a Blocking-Driven Pattern Change?

With strong blocking continuing and with blocking likely to continue through much or all of the medium-term (excepting for a few ensemble members), one typically would expect to see the beginning of a pattern change to colder in parts of eastern North America. I've speculated that the transition could begin sometime during the second week of December (#19 and #25) but the risk of error of being too fast probably outweighs the risk of my being too slow. The month last 10-14 days of the month probably will wind up colder than normal in a large part of the East if my thinking is right.

The upcoming bout of exceptional warmth does not change things. Such warmth has occurred in the past in patterns that later flippled (eg. December 7-9, 1980 was referenced).

The latest guidance lends some confidence that a pattern shift is becoming more likely. Timing questions abound and the timing shown on the guidance is not a high confidence proposition.

First, if one takes a look at the NAEFS (12/9-15/2012 forecast), one finds more moderate probabilities of warmth in the East. A look at the 12/1/2012 0z GFS ensemble forecast finds similar anomalies early in the NAEFS's forecast period.

However, the GFS ensembles are transitioning toward a trough in the East/cold in the East. By 360 hours, the trough and cold anomalies are a prominent feature on the GFS ensembles.

The subsequent 6z run had a similar outcome. So if the GFS ensembles are right, the NAEFS forecast does not necessarily indicate no change in the pattern. Rather, the probability of warm anomalies overall for the period in question might well reflect early warmth that outduels the arrival of colder air.

Finally, the last two runs of the CFSv2 anomalies have shown cold anomalies in a significant part of eastern North America.

Overall, my confidence in the idea of a pattern change has increased. Timing questions remain, as does uncertainty. At least we're not looking at a winter 2011-12 scenario where week after week passed with little prospect of anything more than transient cold.

[usedtobe]

Don,

We're now pretty much in accord. I don't like our snow chances through Dec 15th as even if the euro is sort of right with it's 240 hr forecast, it looks to me like the low would track to the north of DC. Beyond that time, I like seeing the low heights over AK being replaced though I'd like to see the ridge axis farther east while I'd like to see the atlantic blocking farther west. Still, I like the idea of the AO being negative during most of the month and think it likely that Jan will also probably be more in the negative range than positive.

[donsutherland1]

Don,

We're now pretty much in accord. I don't like our snow chances through Dec 15th as even if the euro is sort of right with it's 240 hr forecast, it looks to me like the low would track to the north of DC. Beyond that time, I like seeing the low heights over AK being replaced though I'd like to see the ridge axis farther east while I'd like to see the atlantic blocking farther west. Still, I like the idea of the AO being negative during most of the month and think it likely that Jan will also probably be more in the negative range than positive.

I agree, Wes. Hopefully, things will continue to progress to the point where there are much more favorable prospects for snowfall during the second half of the month. Anything before then would be a bonus.

[GaWx]

There's no Q in my mind that model consensus has cooled quite a bit over the last 24 hours in much of the E US for the 7-15 day period. This is quite encouraging as far as temp.'s are concerned starting mid-month.

[donsutherland1]

Some morning thoughts...

1. The AO had risen to -0.627 today, but is forecast to dive to strongly negative levels in coming days. Within a week, there is strong ensemble support for a figure at or below -3.000. Some ensemble members take the AO below -4.000.

2. While there have been some exceptions where strong or persistent blocking failed to translate into colder weather in parts of eastern North America, those cases have typically been the exception. December 2001 is one such case. However, coming into December there was more cold air available then there was in 2001 across Canada out to Asia.

3. The current pattern is quite similar to the December 7-9, 1980 case. Similar to that timeframe, temperatures are forecast to soar. Much of the Ohio Valley, Mid-Atlantic, and New England regions will likely see high temperatures top out 1.5-2.5 standard deviations above normal (the largest anomalies being in the norther parts of those areas). Southern Ontario, including Toronto, and southern Quebec could see a high temperature more than 2 standard deviations above normal over the next day or two.

For purposes of comparison, the following are the 1.5-2.0 standard deviation anomalies for the December 1-10 timeframe (1981-2010 base period) for select cities:

Boston: 59°-64°

New York City: 61°-66°

Philadelphia: 63°-68°

Washington, DC: 65°-70°

The 12/3/2012 0z MOS (MAV and MET) forecasts show the following ranges:

Boston: 55°-57°

New York City: 62°-66°

Philadelphia: 64°-66°

Washington, DC: 67°-68°

My guess is that Boston could reach or exceed 60° (probably Wednesday) and Washington, DC has a chance to reach 70° (probably tomorrow).

The 1980 pattern later flipped to a colder one. Having said that, there are enough differences e.g., the pronounced warmth in the Arctic region and the forecast for a positive EPO that suggest that the colder pattern probably won't produce severe to extreme cold. Hence, despite mixed guidance, I still expect a transition to colder weather to begin sometime during the second week of this month. The last 10-14 days of December would probably wind up generally colder than normal, but severe cold probably won't occur during that timeframe. Snowfall opportunities could increase for the Great Lakes/Ohio Valley/Mid-Atlantic/Northeast during that colder period.

In the meantime, while the U.S./southern Canada await the turn to colder weather, the siege of cold is likely to hold for much or all of the next 10-14 days in Western Europe. The same holds true for parts of East Asia, though some moderation could occur later in the timeframe depending on the evolution of the Pacific pattern.

[uncle W]

Some morning thoughts...

1. The AO had risen to -0.627 today, but is forecast to dive to strongly negative levels in coming days. Within a week, there is strong ensemble support for a figure at or below -3.000. Some ensemble members take the AO below -4.000.

2. While there have been some exceptions where strong or persistent blocking failed to translate into colder weather in parts of eastern North America, those cases have typically been the exception. December 2001 is one such case. However, coming into December there was more cold air available then there was in 2001 across Canada out to Asia.

3. The current pattern is quite similar to the December 7-9, 1980 case. Similar to that timeframe, temperatures are forecast to soar. Much of the Ohio Valley, Mid-Atlantic, and New England regions will likely see high temperatures top out 1.5-2.5 standard deviations above normal (the largest anomalies being in the norther parts of those areas). Southern Ontario, including Toronto, and southern Quebec could see a high temperature more than 2 standard deviations above normal over the next day or two.

For purposes of comparison, the following are the 1.5-2.0 standard deviation anomalies for the December 1-10 timeframe (1981-2010 base period) for select cities:

Boston: 59°-64°

New York City: 61°-66°

Philadelphia: 63°-68°

Washington, DC: 65°-70°

The 12/3/2012 0z MOS (MAV and MET) forecasts show the following ranges:

Boston: 55°-57°

New York City: 62°-66°

Philadelphia: 64°-66°

Washington, DC: 67°-68°

My guess is that Boston could reache or exceed 60° (probably Wednesday) and Washington, DC has a change to reach 70° (probably tomorrow).

The 1980 pattern later flipped to a colder one. Having said that, there are enough differences e.g., the pronounced warmth in the Arctic region and the forecast for a positive EPO that suggest that the colder pattern probably won't produce severe to extreme cold. Hence, despite mixed guidance, I still expect a transition to colder weather to begin sometime during the second week of this month. The last 10-14 days of December would probably wind up generally colder than normal, but severe cold probably won't occur during that timeframe. Snowfall opportunities could increase for the Great Lakes/Ohio Valley/Mid-Atlantic/Northeast during that colder period.

In the meantime, while the U.S./southern Canada await the turn to colder weather, the siege of cold is likely to hold for much or all of the next 10-14 days in Western Europe. The same holds true for parts of East Asia, though some moderation could occur later in the timeframe depending on the evolution of the Pacific pattern.

nice post Don...It was 66 degrees on this date in 2009 in NYC...Two weeks later we were shoveling 11" of snow...Going back to 1960 when I was 11 NYC reached the 60's for a few days the first week of December and then we got a blizzard a week later...natually if this torch we are having now continues the winter will end up like last year...I don't think that will happen this year...1980 became much colder with the coldest Christmas on record...NYC has not had a single digit day in December since 1989...Could it happenn this year?...TWT...

[Ottawa Blizzard]

Some morning thoughts...

1. The AO had risen to -0.627 today, but is forecast to dive to strongly negative levels in coming days. Within a week, there is strong ensemble support for a figure at or below -3.000. Some ensemble members take the AO below -4.000.

2. While there have been some exceptions where strong or persistent blocking failed to translate into colder weather in parts of eastern North America, those cases have typically been the exception. December 2001 is one such case. However, coming into December there was more cold air available then there was in 2001 across Canada out to Asia.

3. The current pattern is quite similar to the December 7-9, 1980 case. Similar to that timeframe, temperatures are forecast to soar. Much of the Ohio Valley, Mid-Atlantic, and New England regions will likely see high temperatures top out 1.5-2.5 standard deviations above normal (the largest anomalies being in the norther parts of those areas). Southern Ontario, including Toronto, and southern Quebec could see a high temperature more than 2 standard deviations above normal over the next day or two.

For purposes of comparison, the following are the 1.5-2.0 standard deviation anomalies for the December 1-10 timeframe (1981-2010 base period) for select cities:

Boston: 59°-64°

New York City: 61°-66°

Philadelphia: 63°-68°

Washington, DC: 65°-70°

The 12/3/2012 0z MOS (MAV and MET) forecasts show the following ranges:

Boston: 55°-57°

New York City: 62°-66°

Philadelphia: 64°-66°

Washington, DC: 67°-68°

My guess is that Boston could reache or exceed 60° (probably Wednesday) and Washington, DC has a change to reach 70° (probably tomorrow).

The 1980 pattern later flipped to a colder one. Having said that, there are enough differences e.g., the pronounced warmth in the Arctic region and the forecast for a positive EPO that suggest that the colder pattern probably won't produce severe to extreme cold. Hence, despite mixed guidance, I still expect a transition to colder weather to begin sometime during the second week of this month. The last 10-14 days of December would probably wind up generally colder than normal, but severe cold probably won't occur during that timeframe. Snowfall opportunities could increase for the Great Lakes/Ohio Valley/Mid-Atlantic/Northeast during that colder period.

In the meantime, while the U.S./southern Canada await the turn to colder weather, the siege of cold is likely to hold for much or all of the next 10-14 days in Western Europe. The same holds true for parts of East Asia, though some moderation could occur later in the timeframe depending on the evolution of the Pacific pattern.

Great post Don and thanks for including southern Ontario and southern Quebec in your outlook. Always much appreciated!

I also like how your forecasts are devoid of hype, exemplified here in how you point out that there likely won't be any severe cold such as was seen in months like December 1980, December 1989 and January 1994. Joe Bastardi usually has a video for free on Saturdays and watching that, as well as reading his tweets, you'd swear the biggest arctic outbreak in years was coming. It would appear that this is very unlikely.

For your reference, here is a link to Bastardi's latest free video to show you what I'm referring to. The video is on the right of the screen.

http://www.weatherbell.com/

Keep up the good work!

[donsutherland1]

Great post Don and thanks for including southern Ontario and southern Quebec in your outlook. Always much appreciated!

I also like how your forecasts are devoid of hype, exemplified here in how you point out that there likely won't be any severe cold such as was seen in months like December 1980, December 1989 and January 1994. Joe Bastardi usually has a video for free on Saturdays and watching that, as well as reading his tweets, you'd swear the biggest arctic outbreak in years was coming. It would appear that this is very unlikely.

For your reference, here is a link to Bastardi's latest free video to show you what I'm referring to. The video is on the right of the screen.

http://www.weatherbell.com/

Keep up the good work!

Thanks Ottawa Blizzard.

I have not yet viewed the video, but will do so later. I did click on the hyperlink above it and saw the Weatherbell December map. If that map is to verify, one will probably need a sustained period of much colder than normal readings in the East (Toronto and Ottawa areas, included)--probably a bout of severe cold given the warm anomalies that will build up, in general, through the first two weeks of the month. I don't believe such cold is likely this month. Of course, I could be wrong.

Having said this, I am much more encouraged than I was last winter. Week after week, the outlook favored warmth with no meaningful pattern changes.

[donsutherland1]

At 2 pm, the temperature was 70° at Washington, DC (DCA). That ties the daily record set in 1950. It is also the first December 70° temperature in Washington, DC since December 28, 2008. The last time it was warmer than 70° in December occurred on December 28, 2006 with a temperature of 74°. However, that was not the highest monthly reading. The mercury reached 75° on December 1, 2006.

[Isotherm]

NAEFS suggest a continued cold pattern for Asia, Europe, with blocking developing in the NAO regions. However, not much cooling into the Eastern US through the 18th per the NAEFS. Note the reservoir of cold building across Canada and likely seeping into the nern tier, particularly the northern Plains by mid December. It's likely that any change to sustained cold outside of the Upper-Mid-west/nern Plains will not occur before the 15th. Transient cold shots will occur as we see this Thursday w/ a brief surge of -10c 850's into the Northeast, but it's in and out in 24 hours. The NPAC pattern is unfavorable as is the north atlantic right now. Until we can significantly improve at least one of those oceans, sustained cold isn't likely to occur. Modelling seems to be more in agreement on general Atlantic improvement rather than NPAC at this time.

[Isotherm]

CONUS view. I would not be surprised if this is underestimating the amount of cold in the nern Plains.

[donsutherland1]

Some high temperatures from today:

Baltimore: 70°

Boston: 59°

Hartford: 57°

New York City: 60°

Newark: 64°

Philadelphia: 67°

Providence: 60°

Washington, DC:

...DCA: 71° (broke daily record of 70° set in 1950)

...IAD: 69°

[GaWx]

Folks,

The NOAA Nov. 2012 averaged PDO was just released and was -0.60 vs. -1.13 in Oct. My eyeballing tells me that the NOAA # is currently probably a bit lower than that....say, ~-.75 to perhaps as low as ~-1.00.

ftp://ftp.ncdc.noaa.gov/pub/data/cmb/ersst/v3b/pdo/pdo.dat

Based on the pattern when comparing these two tables, I expect the U of Washington # for Nov. to be higher than -0.60...maybe as high as ~-0.40.

I honestly expected a more negative # than -0.60. This may bode well for the winter if we could finally shake off the stubborn -PNA as -0.60 is a pretty modest -PDO, especially for the NOAA table.

[donsutherland1]

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.

[Isotherm]

The negative PNA signalling is of fairly high confidence for the medium range; I think it's a matter of the orientation and magnitude of the -NAO block in determining exactly where that thermal gradient sets-up in the US. As your maps indicate, it will be difficult to overwhelm the entire the nation w/ below normal temps unless the NAO is strongly negative and west based, like 2010. Otherwise we're probable to see that tight N-S differential. Unfortunately, in these type of patterns, bust potential is higher and many people may be disappointed depending upon where that gradient ultimately lays itself down.

[WEATHER53]

At 2 pm, the temperature was 70° at Washington, DC (DCA). That ties the daily record set in 1950. It is also the first December 70° temperature in Washington, DC since December 28, 2008. The last time it was warmer than 70° in December occurred on December 28, 2006 with a temperature of 74°. However, that was not the highest monthly reading. The mercury reached 75° on December 1, 2006.

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

[Srain]

The 00Z Euro has trended toward what the GFS had been suggesting for the past 4 days with a deepening Great Basin trough as well as a robust upper low closing off at the base of that trough. There are hints of both Winter and Severe elements that could be involved with this potential somewhat negative tilted trough axis. We need to see a bit more agreement in the guidance before biting too hard on any solution. The guidance has been all over the place regarding the piece of colder air dropping S from Western Canada and the 500mb pattern. That said it does raise an eyebrow because it has been a very long time since we've seen such a scenario develop this far S and we'll need to see a bit more continuity before honing in on a final solution 6-8 days out. It is encouraging though and does suggest the long awaited pattern change may well be in the cards for those of us across the Southern Rockies/Southern Plains into the Mid West.