AO Forecast to Plunge

[Whacker77]

The area along the Ohio River (EVV/SDF/CVG) is generally not in a great spot for storms. Often, WAA advection places the river communities on the rain/snow line or ice/snow line. In December 1989 and 2000 (la nina years I believe), we saw very cold months, but no big storms. Cold air supression can play havoc in the area as well. Considering the blocking has been so strong, I was just curious if the region might find itself in the bulls eye. Thanks for responding.

[Snow Wizard]

I thought the west was getting plenty of winter weather-- I heard there were reports of widespread 10-15 FEET of snow in the Sierra.

In parts of the NW this is on target to be one of the 5 warmest Decembers in the last century. I have kept records since 1980 and this is number one for me up to this point.

[A-L-E-X]

In parts of the NW this is on target to be one of the 5 warmest Decembers in the last century. I have kept records since 1980 and this is number one for me up to this point.

Wow, that is absolutely astonishing in a moderate la nina! I hope you start to cash in on it sooner rather than later.

Meanwhile I would love to be in the part of Cali that received 17 feet of snow in the last few days. But I bet they get snow no matter the pattern lol.

[donsutherland1]

Quick morning thoughts:

1) The longer-range in the modeling has been trending more noticeably toward the kind of moderation one should probably expect beginning in the first week in January +/- a few days. The key issue will be whether strong blocking redevelops. The signal toward that end is a little weaker on the overnight run of the GFS ensembles. But if such blocking develops, that would enhance prospects for a colder than normal January. Right now, that still remains less likely than moderation and a milder than normal January in the East. January should bring more snowfall to Ottawa than December has.

2) As the transition toward a milder regime takes hold, there could be an opportunity for a Midwest/Great Lakes region snowstorm due to the storm track's shifting north and westward.

3) No severe cold is likely in the eastern third of the U.S. or big cities of Ontario and Quebec anytime over the next 10-14 days.

4) More immediately, the models have begun moving closer into alignment. IMO, the 12/23 0z ECMWF ensemble mean (reasonably close to the recent ensemble means) offers a good idea as to the storm's track and development. I do believe some adjustments, possibly somewhat to the west are possible. In terms of qpf, I believe the 12/23 0z GFS ensembles provide a reasonable early guess as to qpf, perhaps with some adjustment to the west.

5) Historic La Niña climatology cannot be overstated in noting that the timing and location of phasing has to be all but perfect for a historic East Coast snowstorm of the kind earlier runs of the operational ECMWF had been showing. Just a small difference in timing when a phase takes place or if it does would have a substantial impact on the outcome. It is no coincidence that since 1871, there have been only two KU-type storms (December 1909 and January 2000) when the ENSO Region 3.4 anomaly was -1 or below. None of those storms brought 10" or more snow in all of the big cities running from Richmond to Boston (RIC, DCA, PHL, NYC, BOS).

6) During the course of the day's model runs, it wouldn't surprise me to see the GFS push the 0.50" qpf line (dark blue) 25-50 miles westward, possibly by the 12/23 18z and 12/24 0z runs. It remains possible that the Euro might well come up with a more robust solution again at 12z. If so, that could further highlight the possible westward adjustment that might yet occur.

[Porsche]

Quick morning thoughts:

1) The longer-range in the modeling has been trending more noticeably toward the kind of moderation one should probably expect beginning in the first week in January +/- a few days. The key issue will be whether strong blocking redevelops. The signal toward that end is a little weaker on the overnight run of the GFS ensembles. But if such blocking develops, that would enhance prospects for a colder than normal January. Right now, that still remains less likely than moderation and a milder than normal January in the East. January should bring more snowfall to Ottawa than December has.

2) As the transition toward a milder regime takes hold, there could be an opportunity for a Midwest/Great Lakes region snowstorm due to the storm track's shifting north and westward.

3) No severe cold is likely in the eastern third of the U.S. or big cities of Ontario and Quebec anytime over the next 10-14 days.

4) More immediately, the models have begun moving closer into alignment. IMO, the 12/23 0z ECMWF ensemble mean (reasonably close to the recent ensemble means) offers a good idea as to the storm's track and development. I do believe some adjustments, possibly somewhat to the west are possible. In terms of qpf, I believe the 12/23 0z GFS ensembles provide a reasonable early guess as to qpf, perhaps with some adjustment to the west.

5) Historic La Niña climatology cannot be overstated in noting that the timing and location of phasing has to be all but perfect for a historic East Coast snowstorm of the kind earlier runs of the operational ECMWF had been showing. Just a small difference in timing when a phase takes place or if it does would have a substantial impact on the outcome. It is no coincidence that since 1871, there have been only two KU-type storms (December 1909 and January 2000) when the ENSO Region 3.4 anomaly was -1 or below. None of those storms brought 10" or more snow in all of the big cities running from Richmond to Boston (RIC, DCA, PHL, NYC, BOS).

6) During the course of the day's model runs, it wouldn't surprise me to see the GFS push the 0.50" qpf line (dark blue) 25-50 miles westward, possibly by the 12/23 18z and 12/24 0z runs. It remains possible that the Euro might well come up with a more robust solution again at 12z. If so, that could further highlight the possible westward adjustment that might yet occur.

Thanks Don, you seem to be spot on with your analysis, hopefully it can get shoved a little bit back west for my area, I'm guess maybe a dusting to an inch or so right now for my area.

[easternsnowman]

If you look at the past 20 years in the big east coast cities most January temps have averaged 1 or 2 degrees above the so-called norms.

[wxmx]

Quick morning thoughts:

1) The longer-range in the modeling has been trending more noticeably toward the kind of moderation one should probably expect beginning in the first week in January +/- a few days. The key issue will be whether strong blocking redevelops. The signal toward that end is a little weaker on the overnight run of the GFS ensembles. But if such blocking develops, that would enhance prospects for a colder than normal January. Right now, that still remains less likely than moderation and a milder than normal January in the East. January should bring more snowfall to Ottawa than December has.

2) As the transition toward a milder regime takes hold, there could be an opportunity for a Midwest/Great Lakes region snowstorm due to the storm track's shifting north and westward.

3) No severe cold is likely in the eastern third of the U.S. or big cities of Ontario and Quebec anytime over the next 10-14 days.

4) More immediately, the models have begun moving closer into alignment. IMO, the 12/23 0z ECMWF ensemble mean (reasonably close to the recent ensemble means) offers a good idea as to the storm's track and development. I do believe some adjustments, possibly somewhat to the west are possible. In terms of qpf, I believe the 12/23 0z GFS ensembles provide a reasonable early guess as to qpf, perhaps with some adjustment to the west.

5) Historic La Niña climatology cannot be overstated in noting that the timing and location of phasing has to be all but perfect for a historic East Coast snowstorm of the kind earlier runs of the operational ECMWF had been showing. Just a small difference in timing when a phase takes place or if it does would have a substantial impact on the outcome. It is no coincidence that since 1871, there have been only two KU-type storms (December 1909 and January 2000) when the ENSO Region 3.4 anomaly was -1 or below. None of those storms brought 10" or more snow in all of the big cities running from Richmond to Boston (RIC, DCA, PHL, NYC, BOS).

6) During the course of the day's model runs, it wouldn't surprise me to see the GFS push the 0.50" qpf line (dark blue) 25-50 miles westward, possibly by the 12/23 18z and 12/24 0z runs. It remains possible that the Euro might well come up with a more robust solution again at 12z. If so, that could further highlight the possible westward adjustment that might yet occur.

Great analysis as usual Don. Looking at the long range, yes it looks like there will be some moderation for the first week of January in the east coast, but I think the key won't be high latitude blocking/NAO (as it has been for December, though I think there will still be some kind of high latitude ridging) for the rest of the month, but the Pacific. Interestingly, the Pacific looks to be getting a lot more Niño like for January, with the replacement of the Aleutian high with a low, West coast ridging, remnants of Davis straits ridging and a more active STJ. Looks like all of this is MJO driven, with a more coherent wave trying to make it to phase 7 (and beyond)...not forecasted to be strong by any means, but stronger than it has been for months in those phases.

MJO

GFS ensembles:

PNA

Tropical forcing (day 11+)

[Srain]

Glad you brought this discussion over to the main forum, Jorge. Don, we've been watching this in the TX/MX sub forum for a while now and the signals are stunning to say the least. Look forward to your thoughts regarding these significant changes.

[donsutherland1]

Great analysis as usual Don. Looking at the long range, yes it looks like there will be some moderation for the first week of January in the east coast, but I think the key won't be high latitude blocking/NAO (as it has been for December, though I think there will still be some kind of high latitude ridging) for the rest of the month, but the Pacific. Interestingly, the Pacific looks to be getting a lot more Niño like for January, with the replacement of the Aleutian high with a low, West coast ridging, remnants of Davis straits ridging and a more active STJ. Looks like all of this is MJO driven, with a more coherent wave trying to make it to phase 7 (and beyond)...not forecasted to be strong by any means, but stronger than it has been for months in those phases.

Thanks Jorge. I do agree that once the severe block erodes/ends (now a good signal on the GFS ensembles), the Pacific will play the leading role until/unless a fresh severe block develops. Some of the longer-range modeling and also the reforecast ensembles are headed in the direction of moderation in the East consistent with the demise of the severe block. Weaker blocking won't really have a large impact.

In general, when it comes to January, during cases in which the ENSO Region 3.4 anomaly was -1.00 or below, the La Niña pattern typically predominates unless the AO is severely negative. The noted January 1985 Arctic outbreak occurred when the AO was below -3.000. The mean high and low temperatures (°F) for select cities follows:

AO: -3.000 or below:

Boston: 30.8°-18.5°

New York: 34.8°-23.6°

Philadelphia: 36.4°-22.4°

Washington, DC: 41.2°-25.5°

AO: -2.999 to -1.000:

Boston: 36.0°-23.1°

New York: 38.7°-25.9°

Philadelphia: 39.8°-25.5°

Washington, DC: 43.5°-28.9°

AO: -0.999 to 0.000:

Boston: 37.9°-22.2°

New York: 39.3°-27.1°

Philadelphia: 41.6°-26.2°

Washington, DC: 45.2°-30.0°

[easternsnowman]

Thanks Jorge. I do agree that once the severe block erodes/ends (now a good signal on the GFS ensembles), the Pacific will play the leading role until/unless a fresh severe block develops. Some of the longer-range modeling and also the reforecast ensembles are headed in the direction of moderation in the East consistent with the demise of the severe block. Weaker blocking won't really have a large impact.

In general, when it comes to January, during cases in which the ENSO Region 3.4 anomaly was -1.00 or below, the La Niña pattern typically predominates unless the AO is severely negative. The noted January 1985 Arctic outbreak occurred when the AO was below -3.000. The mean high and low temperatures (°F) for select cities follows:

AO: -3.000 or below:

Boston: 30.8°-18.5°

New York: 34.8°-23.6°

Philadelphia: 36.4°-22.4°

Washington, DC: 41.2°-25.5°

AO: -2.999 to -1.000:

Boston: 36.0°-23.1°

New York: 38.7°-25.9°

Philadelphia: 39.8°-25.5°

Washington, DC: 43.5°-28.9°

AO: -0.999 to 0.000:

Boston: 37.9°-22.2°

New York: 39.3°-27.1°

Philadelphia: 41.6°-26.2°

Washington, DC: 45.2°-30.0°

It looks like when the AO get around neutral so are the temps, maybe a degree above.

[donsutherland1]

It looks like when the AO get around neutral so are the temps, maybe a degree above.

One should also keep an eye on the GWO. GWO Phases 2 and 3 have typically been the coldest, on average, during moderate or strong La Niña events (ENSO Region 3.4 anomalies of -1.00 or lower), both when the AO was positive and negative. The great January 1985 Arctic outbreak occurred during GWO Phase 2. Phase 5 has sometimes witnessed strong shots of cold when the AO has been negative. Phase 4 was the warmest, in general. Phase 1 came out even warmer, especially when the AO was positive, but data is insufficient and could be skewed due to an anomalous event in the very limited data set.

We've just switched to Phase 4. With the AO likely to be approaching zero toward the end of the month/early January and were the GWO to remain in a "warm" La Niña phase, a spike in temperatures would be plausible in parts of eastern North America. Such a spike could be produced as the storm track shifts to the north and west, even before the tendency for SE ridging increases.

[uncle W]

so far temperatures this month are a little like Dec. 62...Not exactly in the upper mid west especially Montana but close enough along the east coast...

12/31/62 had the Maine Blizzard and the mother load of cold air before a milding trend early January...January 1963 was cold also as the blocking continued...

[Whacker77]

So it looks as though la nina is ready to assert itself across America. I don't get the sense from reading all of the comments in this thread a blowtorch is in the offing, but is a replay of 2000-2001 possible? I know there are significant differences, but after a cold December, January was closer to average.

[wxmx]

So it looks as though la nina is ready to assert itself across America. I don't get the sense from reading all of the comments in this thread a blowtorch is in the offing, but is a replay of 2000-2001 possible? I know there are significant differences, but after a cold December, January was closer to average.

More likely a non-Niña pattern is ready to assert itself...at least through the first half of January, IMO. More like moderate high latitude blocking versus severe -AO & -NAO, but it looks like a Aleutian low vs the constant ridge he have had and neutral to positive PNA are possible plus some active STJ. All of these more non-Niña like.

[donsutherland1]

So it looks as though la nina is ready to assert itself across America. I don't get the sense from reading all of the comments in this thread a blowtorch is in the offing, but is a replay of 2000-2001 possible? I know there are significant differences, but after a cold December, January was closer to average.

IMO, the best chance for at least a period of blowtorch readings next month would probably be during the second half of the month. In the larger scheme of things, the current La Niña is not likely to come close to those along the lines of 1949-50 or 1998-99.

[pcbjr]

Someone (don) - please educate me.

It does look like the blocking mechanism will be going toward neutral, but then it looks like it starts going negative again shortly after the 1st (seemingly in keeping with the recent pattern as illustrated by the charts below).

So, if the AO and NAO go down in keeping with what appears to be a cycle, why a Jan warm-up/torch?

[donsutherland1]

Someone (don) - please educate me.

It does look like the blocking mechanism will be going toward neutral, but then it looks like it starts going lower again shortly after the 1st (seemingly in keeping with the recent pattern as illustrated by the charts below). I suspect that it will be the second rise that sees it break positive (first week in January).

So, if the AO and NAO go down in keeping with what appears to be a cycle, why a Jan warm-up/torch?

During moderate/strong La Niñas, severe blocking can contribute to sustained cold in the East in January (see Msg #250 in this thread for some temperatures). The AO is forecast to rise close to January 1, fall afterward, and then rise anew. Severe blocking appears to be less likely. Hence, I expect moderation during the first week in January. That means, on average, warmer than it has been.

A torch is not guaranteed for January. But if there is a period where temperatures run much above normal, I suspect that it would occur in the second half of the month.

Finally, it is not yet assured that the month as a whole will wind up warmer than normal. Odds somewhat lean in that direction unless the month is blocky. If not, were the GWO to primarily stay in, let's say Phase 2, and the EPO were to go negative, then the month could also be cold on account of some strong cold shots. Right now, the EPO is progged to be positive at least through the first week in January.

[pcbjr]

During moderate/strong La Niñas, severe blocking can contribute to sustained cold in the East in January (see Msg #250 in this thread for some temperatures). The AO is forecast to rise close to January 1, fall afterward, and then rise anew. Severe blocking appears to be less likely. Hence, I expect moderation during the first week in January. That means, on average, warmer than it has been.

A torch is not guaranteed for January. But if there is a period where temperatures run much above normal, I suspect that it would occur in the second half of the month.

Finally, it is not yet assured that the month as a whole will wind up warmer than normal. Odds somewhat lean in that direction unless the month is blocky. If not, were the GWO to primarily stay in, let's say Phase 2, and the EPO were to go negative, then the month could also be cold on account of some strong cold shots. Right now, the EPO is progged to be positive at least through the first week in January.

As always, thanks for the education, and for the patience in dealing with questions that can be simple (except to me!).

[tacoman25]

so far temperatures this month are a little like Dec. 62...Not exactly in the upper mid west especially Montana but close enough along the east coast...

12/31/62 had the Maine Blizzard and the mother load of cold air before a milding trend early January...January 1963 was cold also as the blocking continued...

1950 is a very good match overall

[uncle W]

1950 is a very good match overall

that is a better match as of now...Big difference Jan and Feb in those winters...One got milder and the other stayed cold but snow was light both years in NYC...

[A-L-E-X]

that is a better match as of now...Big difference Jan and Feb in those winters...One got milder and the other stayed cold but snow was light both years in NYC...

Looks like that below normal snowfall in Dec scenario leading to below normal seasonal snowfalls (excluding el ninos) most of the time might work out-- that's what they were talking about in the NE thread, and the numbers were pretty significant.

[uncle W]

Looks like that below normal snowfall in Dec scenario leading to below normal seasonal snowfalls (excluding el ninos) most of the time might work out-- that's what they were talking about in the NE thread, and the numbers were pretty significant.

My post from last year showing the percentages are much higher for an above snow season if NYC got 3" or more in Dec. was lost on easternwx...very few exceptions...

[donsutherland1]

Looks like that below normal snowfall in Dec scenario leading to below normal seasonal snowfalls (excluding el ninos) most of the time might work out-- that's what they were talking about in the NE thread, and the numbers were pretty significant.

I agree. In 9/10 moderate-strong La Niña cases since 1871, NYC saw less than 20" seasonal snowfall when it received less than 2.5" in December. FWIW, at the Newx-forecasts seasonal snowfall contest, my seasonal snowfall estimate for NYC was 13.9". My guess for Boston was 33.5".

[donsutherland1]

Some early evening thoughts:

I still like the ECMWF ensemble mean track (very good continuity) and also the 12z GFS ensemble mean qpf idea. While I believe a blockbuster HECS is very unlikely, I do believe a moderate snowstorm of the 3"-6"/4"-8" variety (perhaps localized significant snowfall e.g., in parts of New England) remains on the table. I was happy to see the 18z GFS shift in that direction. I also believe that the idea of the 0.50" qpf line shifting further west, perhaps to a position near NYC and along the Jersey Shore has some possibility. Beyond this event, the next possible significant event will likely be a cutter in the 1/1-3 timeframe. Even as Ottawa and Toronto probably start as rain, both will probably end as snow. Ottawa has a chance to pick up a moderate snowfall.

[ThatWxGuy16]

1950 is a very good match overall

I actually put this in one of our reports today illustrating the neat similarities of this Dec MTD to the 1950 Dec. The spatial temperature pattern correlation over the CONUS was r=0.88 according to our calculations.

1950

2010

One of the other nice similarities (and not totally unrelated obviously) was the ridge/trough pattern across the NH during Dec 1950 and this Dec (same days as maps above)...

Dec 2010

1950

Does this make 1950 all of a sudden a front-runner for the upcoming January? No, not necessarily, but Dec 1950 did feature a cold ENSO (-0.93) with a -AO (-1.93) and -NAO (-1.02).

The following January had a clear breakdown in the blocking as measured by the monthly AO and NAO values (-0.085 and 0.08, respectively).

While the debate is certainly open on whether this January will see a similar breakdown in the blocking the ensemble guidance is hinting at it...at least on average.

Note the 12z GFS and ECMWF ensembles means show positive values for the AO as we get into Jan (might be hard to see but they are the thicker lines the plots below). I mention the debate in the sentence above because look how many d@mn members are still dropping the hammer and return to low index values!

At any rate...the month as whole in Jan 1951 was relatively warm in the East...

BUT the last week was GD cold. (note these maps are relative to normal and this period is approx the coldest time of year per the 30yr normals...) So, if anything, January could be pretty d@mn interesting once all is said and done!

[Whacker77]

Looking at those maps, I'm reminded of Janaury 1996. As best I can remember, that month featured a lot of variability in the temperatures. Where I live, SDF, we began the month cold with a foot of snow and then 10 days later it was warm and flooding was a problem. Not too long after that, we dropped 60 degrees in 24 hours going from 70 to 10. Janaury was back and forth, but lead to a coldish February. I remember it being stormier though. Just throwing this out there.

[VAwxman]

I actually put this in one of our reports today illustrating the neat similarities of this Dec MTD to the 1950 Dec. The spatial temperature pattern correlation over the CONUS was r=0.88 according to our calculations.

1950

2010

That's a stunning pattern match, both with U.S. temps and the global pattern. I don't think you'll ever see any that are closer. Obviously, like you, I'd exercise a lot of caution in riding one single analog too strongly, but it is clearly the leader of the analog pack.

My hunch is that January will indeed be interesting... Less cold than December easily with respect to normal, but not a total rout to the warm side either.

[A-L-E-X]

Looking at those maps, I'm reminded of Janaury 1996. As best I can remember, that month featured a lot of variability in the temperatures. Where I live, SDF, we began the month cold with a foot of snow and then 10 days later it was warm and flooding was a problem. Not too long after that, we dropped 60 degrees in 24 hours going from 70 to 10. Janaury was back and forth, but lead to a coldish February. I remember it being stormier though. Just throwing this out there.

Im wondering if that extremely cold last week of Jan in 1951 also led to a very cold beginning to February.

[A-L-E-X]

I agree. In 9/10 moderate-strong La Niña cases since 1871, NYC saw less than 20" seasonal snowfall when it received less than 2.5" in December. FWIW, at the Newx-forecasts seasonal snowfall contest, my seasonal snowfall estimate for NYC was 13.9". My guess for Boston was 33.5".

Thanks, Don. Its absolutely AMAZING how much of a pattern difference there can be between a weak la nina and a moderate one. I maintain that this could have been an epic snow season for us with a weak la nina (especially after an el nino.) Going for 40"+ for NYC would have been a good bet with a weak la nina after el nino scenario.

[donsutherland1]

Morning thoughts:

1) After taking some time to examine the synoptic pattern and having a look at some of the KU snowstorms for more ideal patterns, I suspect that a good idea for the range of solutions is between the 12/24 0z and 12/24 6z runs of the GFS. There is still a possibility of a solution outside those two, but the opportunity for that outcome is waning.

2) Translated into real weather, parts of New England have the best chance at seeing a 4"-8" snowfall with locally higher amounts. The Jersey Shore, New York City, and southwestern Connecticut have a decent chance of picking up 1"-3" maybe 2"-4" locally (farther east) but there is still an uncomfortably high risk of even lighter amounts.

3) The severe shot of cold shown at the end of the 12/24 0z run of the GFS does not fit the emerging synoptic situation from the Ohio Valley eastward. A more modest shot of cold is still possible there. Stronger cold is possible north of the Canada-U.S. border.

Disclaimer: Those who are faint of heart should stop reading here.

Ugly snowfall Statistics: ENSO Region 3.4 Anomaly -1 or below in both December and January

Boston:

December snowfall < 10": 6/7 (86%) cases had < 40" seasonal snowfall; < 10" December snowfall and no measurable November snowfall: 5/5 (100%) cases had < 40" seasonal snowfall

New York City:

December snowfall < 2.5": 9/10 (90%) cases had < 20" seasonal snowfall

Washington, DC (DCA):

12/12 (100%) of those La Niña cases had < 20" seasonal snowfall; 5/12 (42%) of those La Niña cases had < 10" seasonal snowfall