December 2012 Pattern Analysis

[MJO812]

Fwiw, 0z Nam came in much further south than the GFS. Looks like the Euro.

http://mag.ncep.noaa.gov/NCOMAGWEB/appcontroller?prevPage=Model&MainPage=indexℑ=&page=Param&cycle=12%2F13%2F2012+00UTC&rname=SFC-LAYER+PARMS&pname=850_temp_mslp_precip&pdesc=&model=NAM&area=NAMER&cat=MODEL+GUIDANCE&fcast=084&areaDesc=North+America+-+US+Canada+and+northern+Mexico&prevArea=NAMER&currKey=model&returnToModel=&imageSize=M

[tombo82685]

Fwiw, 0z Nam came in much further south than the GFS. Looks like the Euro.

http://mag.ncep.noaa...el=&imageSize=M

The lows are in the same spot in michigan. The nam just has more front running moisture. Also, has more of a cold air drainage, but its still to warm for both nyc and phl on that first storm.

[RowanBrandon]

That first low needs to get further east under the block than that for it to be useful.

[tmagan]

NAM BUFKIT KLGA forecast sounding for 12Z Sunday.

[earthlight]

The ensemble mean still has a poor looking Pacific pattern for us.

The Pacific is not ideal but you can still get snow here in that pattern especially with the ridge spike in the Western US. Any shortwave that comes over the top of that ridge can amplify over the MS Valley and will not cut north with the block in place.

[bluewave]

The Pacific is not ideal but you can still get snow here in that pattern especially with the ridge spike in the Western US. Any shortwave that comes over the top of that ridge can amplify over the MS Valley and will not cut north with the block in place.

We could see a minor snow, but a major December event usually isn't followed by temperatures running

above normal like we have seen this month with the Pacific pattern. All our major December snow events

happened with mostly below normal December monthly temperatures. Since 1995 all the decent snowy

Decembers featured the monthly average temperature from 32.4 to 37.6. Even if we cool down after the

20th, I don't think that we will be able to finish below 39 for the month since we are running over 5+ now.

But we could always pull a rabbit out of the hat ,so I would never say never.

[earthlight]

We could see a minor snow, but a major December event usually isn't followed by temperatures running

above normal like we have seen this month with the Pacific pattern. All our major December snow events

happened with mostly below normal December monthly temperatures. Since 1995 all the decent snowy

Decembers featured the monthly average temperature from 32.4 to 37.6. Even if we cool down after the

20th, I don't think that we will be able to finish below 39 for the month since we are running over 5+ now.

But we could always pull a rabbit out of the hat ,so I would never say never.

I think the pattern could offer the potential for normal or below normal temperatures by the end of December (the last week of the month). But we'll see. The GFS has temperatures running 6 to 9 degrees above normal on the 2m temp anomaly on Tuesday 00z. That's a terrible set up for snow in December so I think we can toss that one out as far as potential snow goes.

The interesting thing is how perfectly the QBO analogs are playing out right now. The QBO analog years for December match up perfectly with the December temperature map across the CONUS so far this month. And, they all show a major pattern flip by January with below normal temperatures across most of the CONUS.

[bluewave]

I think the pattern could offer the potential for normal or below normal temperatures by the end of December (the last week of the month). But we'll see. The GFS has temperatures running 6 to 9 degrees above normal on the 2m temp anomaly on Tuesday 00z. That's a terrible set up for snow in December so I think we can toss that one out.

The interesting thing is how perfectly the QBO analogs are playing out right now. The QBO analog years for December match up perfectly with the December temperature map across the CONUS so far this month. And, they all show a major pattern flip by January with below normal temperatures across most of the CONUS.

This is a very unusual December pattern that we are seeing so far this month. It's very rare to get

such a mild pattern with such persistent blocking. It almost seems like with the ENSO dropping

back to neutral let a -PDO looking pattern emerge over the Pacific. The big -EPO during October

was a textbook El Nino look for that month. But as always, the weather will and can defy what

the analogs suggest will happen so maybe we can get lucky before this month is over.

[earthlight]

This is a very unusual December pattern that we are seeing so far this month. It's very rare to get

such a mild pattern with such persistent blocking. It almost seems like with the ENSO dropping

back to neutral let a -PDO looking pattern emerge over the Pacific. The big -EPO during October

was a textbook El Nino look for that month. But as always, the weather will and can defy what

the analogs suggest will happen so maybe we can get lucky before this month is over.

Well, the blocking is still over Scandanavia for the most part so far. We'll have to see how things really behave, when push comes to shove, as the blocking builds into Greenland in 3-4 days and then retrogrades to Central Canada. This usually helps with cold air transport a little bit and you can see the models trying to swing some cold air in from the PV to the West Coast and then eastward along a gradient through the Northern 1/3 of the US

[bluewave]

Well, the blocking is still over Scandanavia for the most part so far. We'll have to see how things really behave, when push comes to shove, as the blocking builds into Greenland in 3-4 days and then retrogrades to Central Canada. This usually helps with cold air transport a little bit and you can see the models trying to swing some cold air in from the PV to the West Coast and then eastward along a gradient through the Northern 1/3 of the US

Yeah, trying to go beyond the 6-10 day means is always a roll of the dice so anything can happen. I guess that's what keeps these threads so busy this time of year.

[WeatherX]

Yeah, trying to go beyond the 6-10 day means is always a roll of the dice so anything can happen. I guess that's what keeps these threads so busy this time of year.

Yup. This thread is rocking.....You're keeping it on fire there Bluetorch.

[WeatherX]

It gon' snow........that's all you need to know.

[snywx]

Another cold one tonight. 23.9/19

[earthlight]

Some pretty exciting stuff here through the medium and long range. The stratospheric forecasts today are very exciting...plus we're starting to see some better looking potential inside 200 hours now with the Euro trying to get a ridge going on an axis near Boise and maybe amplify something if we get lucky and time a shortwave. Plus the blocking looks nice over Central Canada still. We could use some improvements in the Pac but that will be a step down process which will be aided by the shifting PV thanks to the stratospheric help. Throw in the QBO analogs which strongly support a big flip in the Pacific and overall pattern by Jan..and I think we can start to get a little excited about the prospects of the two to four week period from late Dec into mid to late Jan.

[Isotherm]

To add onto what John noted regarding the stratosphere, the 10 hpa stratospheric vortex will be repositioning itself over the next 10 days and slowly propagating away from our side of the hemisphere, at all levels actually. Thus, by 240hrs we're looking at a stratospheric situation which involves a warming signal across Siberia/Pole and the vortex moving away from Greeland (where it's at right now). This should increase / maintain the tendency for Arctic blocking as we progress into January. The December AO state is also a foreteller of the Jan modality in 75% of cases, so statistical data are on our side as well.

Note the movement of the 10 hpa vortex.

Now -

240hrs -

Additionally, I was pleasantly surprised that the November PDO came in at -0.59, warmer than I thought we'd ever get this winter actually. What this translates to is there's now a higher probability for at least a 2-3 week period of PNA pattern for the CONUS. Given current progression in tropical forcing, stratosphere, and analogs, I expect this favorable north Pacific period to probably fall in the late dec-mid Jan time frame, similar to John's thoughts.

The MJO pulse into phase 1 is real, and the EPO will be neutralizing rapidly over the coming week:

What this all boils down to - regardless of what happens w/ the event 19th, which shouldnt be written off by the way, I'm confident that the pattern will be conducive for the coming month. The descending QBO is a classic early winter strat warming producer and blocking inducer, as we saw in the winter of 2003-04.

[earthlight]

To add onto what John noted regarding the stratosphere, the 10 hpa stratospheric vortex will be repositioning itself over the next 10 days and slowly propagating away from our side of the hemisphere, at all levels actually. Thus, by 240hrs we're looking at a stratospheric situation which involves a warming signal across Siberia/Pole and the vortex moving away from Greeland (where it's at right now). This should increase / maintain the tendency for Arctic blocking as we progress into January. The December AO state is also a foreteller of the Jan modality in 75% of cases, so statistical data are on our side as well.

Note the movement of the 10 hpa vortex.

Now -

240hrs -

Additionally, I was pleasantly surprised that the November PDO came in at -0.59, warmer than I thought we'd ever get this winter actually. What this translates to is there's now a higher probability for at least a 2-3 week period of PNA pattern for the CONUS. Given current progression in tropical forcing, stratosphere, and analogs, I expect this favorable north Pacific period to probably fall in the late dec-mid Jan time frame, similar to John's thoughts.

The MJO pulse into phase 1 is real, and the EPO will be neutralizing rapidly over the coming week:

What this all boils down to - regardless of what happens w/ the event 19th, which shouldnt be written off by the way, I'm confident that the pattern will be conducive for the coming month. The descending QBO is a classic early winter strat warming producer and blocking inducer, as we saw in the winter of 2003-04.

The MJO wave is definitely real this time...the OLR anomalies had me convinced a few days ago. So we're going into phase one with a decent sized pulse..that's pretty much a fact that this point. How it behaves thereafter is still up in the air. Nice stratosphere discussion..agree on all counts. This should keep the PV moving and that's very important as we continue to reshuffle the pattern moving forward. The support for high latitude blocking should continue through January.

The QBO remains a major factor in my reasoning for expecting a flip to a colder and potentially snowier pattern in January. The December QBO analogs (which were the years that featured -25.00 readings for 3 or more months in the fall, then rising towards neutral in Oct and Nov with a neutral Enso state) were almost spot on through the first half of the month with the hemispheric pattern and 2m temperature anomalies. This adds a great amount of confidence to the forecast moving forward. The QBO analogs all show a major pattern flip especially in the Pacific which unloads the cold air into the Northern 1/3 of the CONUS and continues the potential for storminess...and this continues modestly into February.

Rolling these analogs forward into January we get this...

[Isotherm]

Yeah nice post, and I hate to bring up last winter but I feel the contrast must be made apparent given the disaster that unfolded w/ long term forecasting. The QBO regime is polar opposite 2011-12 right now. Last winter we had a positive/westerly phase gradually becoming more negative/easterly as the winter progressed. Whereas at this point in time we're strongly negative but rapidly neutralizing as we approach January. The latter scenario is almost ideal for the development of high latitude blocking, especially when coupled with a low solar background. Last winter featured almost the worst case QBO, Solar, and Stratosphere wise. Another major and obvious difference is the persistence and maintenance of NAO blocking since late October, and the Arctic blocking during November, both strong indicators/correlations for a repeat performance to some degree during the winter.

While the EPO is positive now and some will argue the low height field near AK will doom us, the EPO was negative in November; this is an 80% indicator for a neg EPO winter, and the tropical Pacific is world's apart from last year which featured a MJO pulse cycling thru p3-6, aka a horrendous pattern. I don't know where the MJO will go from phase 1, but it's a lock we're now getting some forcing from the MJO and coupled w/ the recent, sudden SOI plumment, this will send off "shockwaves" to the long wave Pacific pattern and begin to reorient those low heights away from the AK/Bering region.

[Isotherm]

BTW, significant changes on the 00z GFS speaking of mid next week's event.

[Dsnowx53]

Why are we even bothering to discuss the medium and long range when the world is going to end in about a week?

All awful jokes aside, great discussion. It's uncanny how well the QBO analogs have worked out thus far. Individual indices do not usually have that much of an effect in themselves, but when the signal is so obvious regarding a strongly negative QBO rising towards zero, then you can certainly make use of that.

It's great to know that the medium and long range positivity has support from the stratosphere and the analogs. Considering the blocking seems pretty sustained, all we need is a PNA spike - we do not need the Pacific to have a sustained, gorgeous look - it just needs to look good in spurts, considering how active the pattern already is.

Another thing to emphasize is that the good patterns often reward a little later than what you would initially think. The Dec 19-20 threat is still during the transitional period when the Pacific pattern is really poor. After that, the Pacific improves. Remember how long we had to wait in December, 2010?

What's also great is that PV is able to move around and split, yet the blocking remains in tact.

[Dsnowx53]

The QBO analogs also point to signs of major arctic cold as well down the road.

[Dsnowx53]

BTW, significant changes on the 00z GFS speaking of mid next week's event.

First thing that stood out was the fact that there was no Central US ridge after the storm. Instead there is a mean Central US trough. Lol.

Edit: The ridge does develop a few days later, though. But that initial trough could be a weak Miller B signal or something.

[Dsnowx53]

I love seeing those big 1040mb + highs coming down from Central Canada.

[earthlight]

Why are we even bothering to discuss the medium and long range when the world is going to end in about a week?

All awful jokes aside, great discussion. It's uncanny how well the QBO analogs have worked out thus far. Individual indices do not usually have that much of an effect in themselves, but when the signal is so obvious regarding a strongly negative QBO rising towards zero, then you can certainly make use of that.

It's great to know that the medium and long range positivity has support from the stratosphere and the analogs. Considering the blocking seems pretty sustained, all we need is a PNA spike - we do not need the Pacific to have a sustained, gorgeous look - it just needs to look good in spurts, considering how active the pattern already is.

Another thing to emphasize is that the good patterns often reward a little later than what you would initially think. The Dec 19-20 threat is still during the transitional period when the Pacific pattern is really poor. After that, the Pacific improves. Remember how long we had to wait in December, 2010?

What's also great is that PV is able to move around and split, yet the blocking remains in tact.

Yeah the signals are good at this point. I'm pretty confident now in the fact that we're going to get things going by the last week of Dec and continue into Jan. Although there could be some transition periods where things are a little warmer. Especially with the active Pac jet continuing to beat down on the SE Ridge...you're going to have some warmer days in there especially initially without the good low level cold air source.

The QBO analogs are exciting and we can hope that they will hold true. We'll probably know more by then...but the new QBO number for December will come in on 1/5 and we'll see how much it rises. Even now, the 4 analog years all produced a composite anomaly pattern over the NHEM that is very favorable for snow and cold air over the Northern 1/3 of the CONUS. The big thing will be getting the Pac to flip...the Jan QBO analogs have a ridge over AK, the Aleutians and even extending down to the NW US.

[earthlight]

Despite the fact that we're in a period with a million disturbances moving through the CONUS and coming out of the Pacific...there's a pretty clear signal that this 21-23rd storm has some teeth to it. It was lighting up the Euro ensembles this afternoon at 12z...and the GEFS have come on board tonight. Things will more than likely change a million times as we approach the event...but I think this is a period to watch for sure.

[Dsnowx53]

Yeah the signals are good at this point. I'm pretty confident now in the fact that we're going to get things going by the last week of Dec and continue into Jan. Although there could be some transition periods where things are a little warmer. Especially with the active Pac jet continuing to beat down on the SE Ridge...you're going to have some warmer days in there especially initially without the good low level cold air source.

The QBO analogs are exciting and we can hope that they will hold true. We'll probably know more by then...but the new QBO number for December will come in on 1/5 and we'll see how much it rises. Even now, the 4 analog years all produced a composite anomaly pattern over the NHEM that is very favorable for snow and cold air over the Northern 1/3 of the CONUS. The big thing will be getting the Pac to flip...the Jan QBO analogs have a ridge over AK, the Aleutians and even extending down to the NW US.

The pattern even becoming favorable for a Dec 21-23 event of a Miller B type variety would not surprise me. It's still kind of early in the transition period, but the signal was clearly there on the GFS and Euro ensembles. Also, the PNA spike does not happen in time to positively impact the Dec 19 storm, but it might happen in time for the Miller B.

And yes, there certainly will be transition periods, especially early on in the new regime when the Pacific is still reshuffling. But I feel that later on once the Pacific reshuffling finishes, we might be able to get an arctic outbreak of sorts in very late December or early January. The analogs, especially January 1985 and January 2004 support that.

Also, as the block retrogrades westward, it might be able to link with the PNA and Aleutian ridges. That would produce a very strong, sustained negative height anomaly for much of the country.

[West Milford Highlander]

Snowstorms are always 7-10 days out on models

[BxEngine]

Thanks guys for the great discussion overnight.

[Weathergun]

Starting to more linking up between the Aleutian and -NAO ridges over Canada and Alaska on the 6z GEFS, late next week. The more linking or merging we see, is farther west the East coast trough will likely setup for major winter storm threats in our area. After the December 20th

[Sampson]

Thanks guys for the great discussion overnight.

This thread is focused and insightful. Not sure why the NYC forum continues to take a beating this year in some of the other forums. There is far less clutter and weenie drivel in here compared to some. Thanks to all of the contributors.

[Momza]

This thread is focused and insightful. Not sure why the NYC forum continues to take a beating this year in some of the other forums. There is far less clutter and weenie drivel in here compared to some. Thanks to all of the contributors.

think we have quality, not quantity here.