Medium Range Discussion Winter 2011-12

[donsutherland1]

With today's 12z guidance in (except for the 12z Euro ensembles), I don't have much to change from my thinking that the temperature anomaly for the 12/1-10 period as a whole should fall on the warm side of normal. In fact, there's a growing possibility of an outbreak of 60° or higher temperatures into the northern Mid-Atlantic and perhaps southern New England next week that should give a boost to the warm anomalies in the East.

Highest 12/1/2011 12z MOS figures (12/5-6):

Boston: 59°

New York City: 61°

Newark: 62°

Philadelphia: 62°

Providence: 61°

Richmond: 68°

Washington, DC

...DCA: 63°

...IAD: 62°

Afterward, there could be brief window of opportunity (December 10-15 +/- a few days timeframe?) for cold and, if timing is good, some snow in parts of the East. There is some support for such an idea, especially on the 12z Euro. However, the coldest anomalies will likely be directed at the Plains States and then retreat across the Great Lakes region into Canada.

[wxmx]

CONUS-centric wise, it looks like it will be below average for the majority of the country next 2 weeks, though the warmest anomalies will probably be in the eastern third. I don't see a relaxation of the pattern, other than maybe some worsening in the Pac side and a slight improvement in the Atlantic.

[Jaguars]

Anyone with thoughts on how the pattern evolves after the middle of the month?

[pcbjr]

Anyone with thoughts on how the pattern evolves after the middle of the month?

I do, but the mods would probably ban me

Hey - Jax/N Fla - old adage - warm before X-Mas then cold after and vice versa; let's just hope ....

[donsutherland1]

Anyone with thoughts on how the pattern evolves after the middle of the month?

A lot depends on whether blocking develops. The EPO is currently forecast to go positive toward mid-month. Assuming little or no blocking, it is plausible that a mild zonal flow could evolve. Of course, much can change, so this is not cast in stone.

[Ginx snewx]

A lot depends on whether blocking develops. The EPO is currently forecast to go positive toward mid-month. Assuming little or no blocking, it is plausible that a mild zonal flow could evolve. Of course, much can change, so this is not cast in stone.

Don mid range looks pretty decent for a -EPO low level cold period. An ice storm is very possible.

[donsutherland1]

Don mid range looks pretty decent for a -EPO low level cold period. An ice storm is very possible.

I agree. There might be an opportunity for some frozen precipitation in the Dec. 10-15 +/- a few days timeframe. Hopefully, that opportunity will be realized.

[Jaguars]

Thanks Don and others for the info

[Srain]

Heh...interesting pattern this year...

[Ji]

A lot depends on whether blocking develops. The EPO is currently forecast to go positive toward mid-month. Assuming little or no blocking, it is plausible that a mild zonal flow could evolve. Of course, much can change, so this is not cast in stone.

translation from the little devil above Don's shoulder....

December is going to completely suck and the question is will it be a warm 2nd half of december or just downright hot.

[wxmx]

Heh...interesting pattern this year...

Not very Niñaish, with the the lower height anomalies and temps in our backyards. I have noted that the very +AO is producing ridging a little farther north than what we would expect (closer to 40-50N instead of 25-40N)...hence the lower heights in the 25-35N latitudes.

[Srain]

Heck of Plains/GL storm on the Euro...

[usedtobe]

Steve the 12Z euro 240 hour prog is still a lame one for the east especially the mid atlantic.

[BethesdaWX]

Steve the 12Z euro 240 hour prog is still a lame one for the east especially the mid atlantic.

Some ensembles and models now hinting that the polar vortex could begin to weaken a bit soon, can't hurt.

[wxmx]

Silver lining of this ridiculously high +AO is that the PV is on our side of the world and the Pacific ridge refuses to retrograde...this is a setup for a very cold CONUS mid section usually, and the models are now showing another artic shot for this part of the nation.

[donsutherland1]

The 12/4 12z run of the GFS notwithstanding, I have few changes from my thoughts of 11/29 (Message #116).

- We are currently in the midst of a period that, when all is said and done, should generally wind up warmer than normal as a whole in much of the East (12/1-10).

- The GFS, though it is overdone in my opinion, reflects what I believed would be a brief window of opportunity (December 10-15 +/- a few days timeframe) for cold and, if timing is good, some snow in parts of the East. It should be noted that I've seen some charts showing that the GFS ensembles forecast a brief period of a negative AO in the near-term. I disagree.

First, the GFS ensemble charts showing such a depiction are badly initialized. In fact, I cannot recall a worse initialization of the AO.

Second, historic climatology associated with strong AO+ readings in December (especially during La Niña events) and extreme AO+ readings both argue for a much longer-duration AO+ regime than what the GFS ensembles are depicting.

An event that broads rain, possibly some snow to coastal sections and perhaps a moderate interior snowfall during the timeframe in question remains plausible. The kind of storm shown on the 12z GFS appears to be out of line with some of the other modeling e.g., ECMWF, so I don't believe we'll see something quite as significant. Even that storm provides only a small amount of snow to the big cities of the East and their nearby suburbs.

On the GFS, a strong cold shot follows with lows in the teens in the big cities. Again, that is probably overdone, but the areas that have yet to see a freeze will likely see their first freeze in the 12/9-11 period, possibly with lows in the middle and upper 20s.

Finally, if the EPO goes positive and the AO remains positive--the AO's remaining positive is a good probability--ridging could still return to the East in time to provide mild conditions for Hanukkah and Christmas. Hence, I'm not sold on the cold depicted on the 12z GFS from late next week and beyond. I suspect that the 12z Euro will offer a less extreme outlook.

[ptb127]

http://grib2.com/gfs/CONUS_GFS0P5_SFC_ACCUM-SNOW_10-1_120HR.gif

[uncle W]

The 12/4 12z run of the GFS notwithstanding, I have few changes from my thoughts of 11/29 (Message #116).

- We are currently in the midst of a period that, when all is said and done, should generally wind up warmer than normal as a whole in much of the East (12/1-10).

- The GFS, though it is overdone in my opinion, reflects what I believed would be a brief window of opportunity (December 10-15 +/- a few days timeframe) for cold and, if timing is good, some snow in parts of the East. It should be noted that I've seen some charts showing that the GFS ensembles forecast a brief period of a negative AO in the near-term. I disagree.

First, the GFS ensemble charts showing such a depiction are badly initialized. In fact, I cannot recall a worse initialization of the AO.

Second, historic climatology associated with strong AO+ readings in December (especially during La Niña events) and extreme AO+ readings both argue for a much longer-duration AO+ regime than what the GFS ensembles are depicting.

An event that broads rain, possibly some snow to coastal sections and perhaps a moderate interior snowfall during the timeframe in question remains plausible. The kind of storm shown on the 12z GFS appears to be out of line with some of the other modeling e.g., ECMWF, so I don't believe we'll see something quite as significant. Even that storm provides only a small amount of snow to the big cities of the East and their nearby suburbs.

On the GFS, a strong cold shot follows with lows in the teens in the big cities. Again, that is probably overdone, but the areas that have yet to see a freeze will likely see their first freeze in the 12/9-11 period, possibly with lows in the middle and upper 20s.

Finally, if the EPO goes positive and the AO remains positive--the AO's remaining positive is a good probability--ridging could still return to the East in time to provide mild conditions for Hanukkah and Christmas. Hence, I'm not sold on the cold depicted on the 12z GFS from late next week and beyond. I suspect that the 12z Euro will offer a less extreme outlook.

I liked your posts about the AO last year when you knew it would lead to cold and or snowstorms.....This year is a nightmare unless you like near 70 degree temperatures in January...I wouldn't mind if I was living in Florida but as long as I'm living in this area I want the winters to be exciting...I'm still holding out hope for a change in the AO late January or February...

[easternsnowman]

Many forecasters use models to justify their forecasts it seems.

[brad1551]

The 12/4 12z run of the GFS notwithstanding, I have few changes from my thoughts of 11/29 (Message #116).

- We are currently in the midst of a period that, when all is said and done, should generally wind up warmer than normal as a whole in much of the East (12/1-10).

- The GFS, though it is overdone in my opinion, reflects what I believed would be a brief window of opportunity (December 10-15 +/- a few days timeframe) for cold and, if timing is good, some snow in parts of the East. It should be noted that I've seen some charts showing that the GFS ensembles forecast a brief period of a negative AO in the near-term. I disagree.

First, the GFS ensemble charts showing such a depiction are badly initialized. In fact, I cannot recall a worse initialization of the AO.

Second, historic climatology associated with strong AO+ readings in December (especially during La Niña events) and extreme AO+ readings both argue for a much longer-duration AO+ regime than what the GFS ensembles are depicting.

An event that broads rain, possibly some snow to coastal sections and perhaps a moderate interior snowfall during the timeframe in question remains plausible. The kind of storm shown on the 12z GFS appears to be out of line with some of the other modeling e.g., ECMWF, so I don't believe we'll see something quite as significant. Even that storm provides only a small amount of snow to the big cities of the East and their nearby suburbs.

On the GFS, a strong cold shot follows with lows in the teens in the big cities. Again, that is probably overdone, but the areas that have yet to see a freeze will likely see their first freeze in the 12/9-11 period, possibly with lows in the middle and upper 20s.

Finally, if the EPO goes positive and the AO remains positive--the AO's remaining positive is a good probability--ridging could still return to the East in time to provide mild conditions for Hanukkah and Christmas. Hence, I'm not sold on the cold depicted on the 12z GFS from late next week and beyond. I suspect that the 12z Euro will offer a less extreme outlook.

[brad1551]

Remember, what goes up must come down! The real question is when on the +AO. Does not look like anytime soon.

[k***]

Many forecasters use models to justify their forecasts it seems.

this is deserving of its own thread

[winterymix]

Finally, if the EPO goes positive and the AO remains positive--the AO's remaining positive is a good probability--ridging could still return to the East in time to provide mild conditions for Hanukkah and Christmas. Hence, I'm not sold on the cold depicted on the 12z GFS from late next week and beyond. I suspect that the 12z Euro will offer a less extreme outlook.

Hi Don;

To my marginally-educated eye, this pattern seems locked-in. In the "old days" I think they used to refer to long waves,

i.e. hemispheric long waves that would set into an equilibrium and become self-perpetuating for perhaps 35 to 49 days

and even a bit longer; perhaps reflective of MJO patterns.

Thinking of the old analogy that when the rubber band gets stretched too far in a certain direction, it will build potential

energy and oscillate back to the opposite extreme; pehaps mid- and late winter will have more appeal in the East.

Ensemble GFS pattern at 16 days: (more of the same);

Agree or disagree, Don?

[donsutherland1]

Winterymix,

It doesn't look great. I worry that the AO+ regime will prove remarkably durable and the proverbial rubber band might not snap until sometime in January. But even then, there's the prospect that the AO might return to a positive state fairly quickly afterward. Both La Niña cases that saw the AO reach +3.5 or above in December (1975-76 and 1999-00) had very warm anomalies in February. I very much hope that won't be the case this winter, but that is a real concern.

[Mitchel Volk]

Agree, I reduce my official snowfall amounts for NYC down to 20 inches and predicted above normal temperatures. I would not be surprise if NYC gets even lass snow than that this winter. The past few runs of the ECMWF monthly forecast are bearish on coastal snow and arctic air. I think that both the AO and NAO will both be a mainly positive state this winter.

[WidreMann]

this is deserving of its own thread

Seriously wtf.

[donsutherland1]

Verification of 12/5-6/2011 Warmth:

From 12/1/2011; Message #151

...there's a growing possibility of an outbreak of 60° or higher temperatures into the northern Mid-Atlantic and perhaps southern New England next week that should give a boost to the warm anomalies in the East.

Highest 12/1/2011 12z MOS figures (12/5-6):

Boston: 59°

New York City: 61°

Newark: 62°

Philadelphia: 62°

Providence: 61°

Richmond: 68°

Washington, DC

...DCA: 63°

...IAD: 62°

12/5-6/2011 Highest Readings:

Boston: 63°, 12/5

New York City: 61°, 12/6

Newark: 61°, 12/6, 12/6

Philadelphia: 62°, 12/6

Providence: 61°, 12/6

Richmond: 71°, 12/6

Washington, DC:

...DCA: 60°, 12/5

...IAD: 62°, 12/6

In addition, the warmth accumulated through the first six days of December makes it highly likely that the big cities from Richmond to Boston will see above normal anomalies for the 12/1-10 period.

Finally, tomorrow's event will likely bring meaningful snows well inland across the Poconos and Catskills into interior New England. The big cities from Washington to Boston could end as some snow, but any accumulations there will likely be on the light side. This is consistent with data for AO+ regimes during La Niña events.

In the longer-range, there remains little prospect that the AO will go negative. As a result, after mid-month, temperatures could be on the rise in the East. The West could see some additional cold shots, but danger of a turn toward a mild zonal flow still lurks beyond 12/20.

[Feb]

Verification of 12/5-6/2011 Warmth:

From 12/1/2011; Message #151

...there's a growing possibility of an outbreak of 60° or higher temperatures into the northern Mid-Atlantic and perhaps southern New England next week that should give a boost to the warm anomalies in the East.

Highest 12/1/2011 12z MOS figures (12/5-6):

Boston: 59°

New York City: 61°

Newark: 62°

Philadelphia: 62°

Providence: 61°

Richmond: 68°

Washington, DC

...DCA: 63°

...IAD: 62°

12/5-6/2011 Highest Readings:

Boston: 63°, 12/5

New York City: 61°, 12/6

Newark: 61°, 12/6, 12/6

Philadelphia: 62°, 12/6

Providence: 61°, 12/6

Richmond: 71°, 12/6

Washington, DC:

...DCA: 60°, 12/5

...IAD: 62°, 12/6

In addition, the warmth accumulated through the first six days of December makes it highly likely that the big cities from Richmond to Boston will see above normal anomalies for the 12/1-10 period.

Finally, tomorrow's event will likely bring meaningful snows well inland across the Poconos and Catskills into interior New England. The big cities from Washington to Boston could end as some snow, but any accumulations there will likely be on the light side. This is consistent with data for AO+ regimes during La Niña events.

In the longer-range, there remains little prospect that the AO will go negative. As a result, after mid-month, temperatures could be on the rise in the East. The West could see some additional cold shots, but danger of a turn toward a mild zonal flow still lurks beyond 12/20.

So we hit 60 next week, which is mid month, and then temps rise. Good to hear.

[donsutherland1]

So we hit 60 next week, which is mid month, and then temps rise. Good to hear.

My thought has been that the 12/10-15 period +/- a few days could wind up on the cool side of normal. I'm not sure that any 60° readings will be realized during that timeframe. Beyond 12/15 +/- a few days, a milder pattern could begin to reassert itself. After 12/20 if the EPO goes positive (the guidance is divided) and if the AO+ regime persists (likely, but will it be as extreme as it is now?), that's where the risk of even warmer conditions could manifest itself. Right now, my guess is that the Hanukkah/Christmas period will be milder than average. Whether it becomes a full-fledged blowtorch remains to be seen. Unfortunately, that prospect cannot be dismissed quite yet.

[pcbjr]

I'm thinking about organizing a Board softball game for Christmas afternoon. Weather looks like it will be superb for such outside sports.