December 2012 Pattern Analysis

[SnowGoose69]

Tell me about it...my worst winter forecast ever as well by far....looking back I think the signals were fairly clear by early/mid Dec that the winter was going to suck, or in the best case scenario, pull a 2006-07 type deal with the feb reversal.

Agree about the SSW, plenty of misinformation still going around regarding last winter's bust. Many think the SSW was fake and just "made up", but it certainly was real for 70% of the rest of the northern hemisphere - Europe, Asia, etc. England's on one helluva run - this is their 4th winter in a row that's probably colder/snowier than normal.

Usually your make or break date for winter as far as seeing where it may go is late December. People don't realize that while occasionally there are winters that are very cold and snowy or very warm and snowless through late January and then change it does not happen often. Think about how often a summer thats miserable through mid to late July reverses in August...I can only recall one (2001) that did that. As a result, if you're not seeing anything in the MJO/Stratosphere/Weeklies by late December that show a change occurring in the first half of January its pretty likely the rest of the winter will resemble largely what you've already gotten. Exactly why so often winters that have had a bad first half/good 2nd half or vice versa change course sometime close to Christmas or the first week of January. It seems to me that once you're 3 weeks past the solstice both in summer and winter large changes are rare.

[earthlight]

Usually your make or break date for winter as far as seeing where it may go is late December. People don't realize that while occasionally there are winters that are very cold and snowy or very warm and snowless through late January and then change it does not happen often. Think about how often a summer thats miserable through mid to late July reverses in August...I can only recall one (2001) that did that. As a result, if you're not seeing anything in the MJO/Stratosphere/Weeklies by late December that show a change occurring in the first half of January its pretty likely the rest of the winter will resemble largely what you've already gotten. Exactly why so often winters that have had a bad first half/good 2nd half or vice versa change course sometime close to Christmas or the first week of January. It seems to me that once you're 3 weeks past the solstice both in summer and winter large changes are rare.

I think that it has a lot to do with the fact that it takes a much bigger hemispheric event to change the pattern once its settled in around the date you mentioned. I can remember winters that have featured big changes...but it's a big deal..it doesn't just happen all the time. You often have to flip the entire pattern in many parts of the globe.

Luckily for us we're looking pretty good right now.

[Dsnowx53]

There definitely has been subtle hints of a brief +PNA spike on the ensemble data. The MJO would greatly help us with that.

[Chris L]

Yeah I think there are definitely similarities to 2010 - pretty analogous PDO/PNA/blocking wise. ENSO was weak and this year ENSO is not much of a factor for us.

The thing I'm conflicted about is will we see an impressive PNA surge like 2010-11 had. MJO suggests maybe, if we can get phase 1-2 to do its magic later this month. I doubt it'll be able to sustain itself though into January, which is why I think if/when the blocking breaks down, we could be mild for awhile post mid jan. This will be an interesting winter to follow with the first yr in awhile of neutral ENSO...

Tom,

We can get a large storm with a negative to neutral PNA, but the pattern will probably breakdown right after. February 1969 which the PNA was negative, we still got quite a big snowstorm (The Lindsay storm) that month.

[nzucker]

I think that it has a lot to do with the fact that it takes a much bigger hemispheric event to change the pattern once its settled in around the date you mentioned. I can remember winters that have featured big changes...but it's a big deal..it doesn't just happen all the time. You often have to flip the entire pattern in many parts of the globe.

Luckily for us we're looking pretty good right now.

I still don't love this pattern...we have a very strong East Pacific ridge progged offshore which keeps the PNA quite negative. We have the retrograding NAO block timed nicely around mid-month when climo becomes more favorable for snow here, but I'm still concerned about the PNA and potential retreat of the PV into Siberia with cold air getting cut off to Canada. You can see on the 12z ECM that even though we get the big -NAO, the cold air source is a bit depleted by the end of the run.

[weathafella]

I still don't love this pattern...we have a very strong East Pacific ridge progged offshore which keeps the PNA quite negative. We have the retrograding NAO block timed nicely around mid-month when climo becomes more favorable for snow here, but I'm still concerned about the PNA and potential retreat of the PV into Siberia with cold air getting cut off to Canada. You can see on the 12z ECM that even though we get the big -NAO, the cold air source is a bit depleted by the end of the run.

Depleted?

[earthlight]

I still don't love this pattern...we have a very strong East Pacific ridge progged offshore which keeps the PNA quite negative. We have the retrograding NAO block timed nicely around mid-month when climo becomes more favorable for snow here, but I'm still concerned about the PNA and potential retreat of the PV into Siberia with cold air getting cut off to Canada. You can see on the 12z ECM that even though we get the big -NAO, the cold air source is a bit depleted by the end of the run.

If the pattern were to shake down as advertised on both the Euro and GFS ensembles...I couldn't agree with what you're saying.. at all. The only thing I can think of is that maybe you're looking for bone chilling polar cold ... which this type of pattern won't deliver to this part of the country. But if you're looking for snow, the pattern being advertised is fantastic. I'll leave it at that.

[Dsnowx53]

The east Pacific ridge is amplified enough to allow for cross polar flow. While we have a -PNA, the Pacific is not awful in that it'll be doing enough to provide enough of a cold air source, provided the blocking does take shape.

[Dsnowx53]

I'm actually starting to think that there will be an even bigger threat a few days after the Dec 19-20 period. The Pacific will be better, and the block may retrograde a bit more and become stronger. Something that I have seen on the ensembles (Euro ensembles included) for after the Dec 19-20 period and especially after is that the Pacific really starts to get reshuffled, and the block anomaly on the ensembles actually gets stronger. Like, literally, the anomaly on the GEFS in the Davis Straights increases from the 288 hour period to the 312 hour period, which is a really strong signal considering the time frame. And look at the +PNA spike on the image below. Isotherm's thoughts about the block being sustained are certainly supported by the GEFS. As long as the MJO doesn't crap the bed this time, the idea for a threat Dec 19-20 and a bigger one a few days after it could certainly be valid.

[bluewave]

The 0Z model runs are even more impressive with the strength of the polar vortex through

day 10 near Alaska. This helps to pump the SE Ridge and maintain above normal temps

here. Beyond the 10 day time frame, our only shot at a return to more normal or even

cooler temps would be heights coming up near Alaska and the PNA region. This is one of

the Pacific dominated patterns where you would want to see a change in the Euro ensembles

day 6-10 first to believe that there would be a change day 11-15.

[MJO812]

Don S seems confident about a change.

Some morning thoughts...

1. The AO has now fallen below -3. It currently stands at -3.055.

2. The PNA has now had its 33rd consecutive negative reading. The guidance shows the PNA remaining negative through the 16-day forecast period. For those who are interested, the PNA once had 81 consecutive negative readings (February 28, 1967 through May 19, 1967).

3. The NAO remains negative and there is strong agreement among the ensemble members that it will fall below -1.000 around December 20.

It's probably around that time that a colder--not exceptionally cold--pattern could lock into a portion of eastern North America. The evolution toward a cooler pattern should start farther west.

Below are composite temperature anomalies for all December cases where the AO was -3.000 or below categorized by cases where the NAO was above -1.000 and those where it was -1.000 or below. In total, there were 136 days in December when the AO was -3.000 or below. Just 4 (2.9%) of those days saw the NAO above 0.000, therefore I didn't create a map for the tiny subset of days with a positive NAO. Nevertheless, that tiny handful of days saw warmth on both the West and East Coasts with cold in the Plains States and across much of Canada.

Finally, below are again the maps for PNA <0 and PNA of -1.000 or below for AO cases where the AO was -3.000 or below:

[Weathergun]

The 0Z model runs are even more impressive with the strength of the polar vortex through

day 10 near Alaska. This helps to pump the SE Ridge and maintain above normal temps

here. Beyond the 10 day time frame, our only shot at a return to more normal or even

cooler temps would be heights coming up near Alaska and the PNA region. This is one of

the Pacific dominated patterns where you would want to see a change in the Euro ensembles

day 6-10 first to believe that there would be a change day 11-15.

The PV though is far enough north, to allow some ridging over Western Canada/Alaska and allows us to tap into some colder, from time to time. It's not the deep AK vortex from last year. We are getting the strong SE ridge, next week, mostly due the 15-16 system dig over the West coast and the -NAO not being strong enough.

[earthlight]

But the similarities to last year are chilling to say the least

No they are not.... not at all.

[earthlight]

The strong AK polar vortex looks to establish itself for the long term, similar to last year.

Can you provide some reasoning behind this thought?

[Jefflaw77]

John,

I know my statement isn't quite correct.. But my concern is that the result, the weather we all enjoy will not be any different, despite the fact that the pattern isn't the same.. Look, i hope I am wrong, and I put a hell of a lot of faith in your forecasting b/c honestly, your posts are second to none...

So yes, i'll shut up w/ my incorrect statements, but again like I said, I fear that the end result (our actual weather) may not turn out very different to last year..

[MJO812]

Storm is still there on the GFS for the 19th. Big signal. Better run than the 0z run for sure.

[earthlight]

John,

I know my statement isn't quite correct.. But my concern is that the result, the weather we all enjoy will not be any different, despite the fact that the pattern isn't the same.. Look, i hope I am wrong, and I put a hell of a lot of faith in your forecasting b/c honestly, your posts are second to none...

So yes, i'll shut up w/ my incorrect statements, but again like I said, I fear that the end result (our actual weather) may not turn out very different to last year..

Regardless of whether or not we had a thunderstorm on the same day, there was a similar cloud in the sky on Aug 10 of last year, we had a hurricane two years in a row...the pattern is completely opposite of what it was last year.

Last year we were staring at wall to wall negative height anomalies over the NAO and PNA regions for the most part (+NAO) with a huge vortex that clearly wasn't budging until January. When I say this year is literally opposite over much of the Atlantic blocking regions, it is literally opposite.

Sure, it may take until mid/late December to come together and things don't always go as planned with mega blizzards starting Dec 1. But the high latitude blocking is something that everybody should get excited about on the medium range guidance. Even with a - PNA pattern, if the blocking retrogrades for a period into the West Based region of Western Greenland and the Davis Straight -- we can benefit.

The only thing I would be concerned about, at this point, is that the MJO forecasts are too bullish and we struggle with tropical forcing...and that the blocking stays more east based. If that is the case, the gradient pattern will be shifted farther north as the southeast ridge will have a chance to build and push the baroclinic zone farther north without the aid of the block keeping it south. But even then, I'd still be confident that the blocking would show up eventually.

You can loop through this for a good look at how, even though there might not be a huge block over Greenland right now...it's getting there..and there are + anomaly ridges all over the high latitudes which is something we haven't seen since 2010.

http://www.meteo.psu.edu/~fxg1/ENSHGTAVGNH_6z/ensloopmref.html

[bluewave]

The PV though is far enough north, to allow some ridging over Western Canada/Alaska and allows us to tap into some colder, from time to time. It's not the deep AK vortex from last year. We are getting the strong SE ridge, next week, mostly due the 15-16 system dig over the West coast and the -NAO not being strong enough.

This is a different pattern than last December since the AO is below -3 instead of above +3.

The temps are also much colder this December in Alaska than during last year.

We would need to see the EPO go more negative along with an improvement in the PNA and

the NAO remaining negative for a colder end to the month.

[PB GFI]

No they are not.... not at all.

Im sure he means in the result thus far , not in the set up atmospherically .

Think once the pac ridges retrogrades back towards the alaskan shore , it will release the trough downstream ,

and hopefully we get a nice block over the Davis straits after the 20th like the Ensembles say .and the trough can settle in and get trapped for a bit in the east .

Think the frustration is the " constant pattern change coming " , last year SSW event never materialized for us

so it wasnt long ago and its in the forefront , think this changes after the 20 th in my opinion .

Just would like see some of the operational runs start to match up with the ensembles.

[uncle W]

the arctic oscillation is the complete opposite of last year...so far it hasn't helped but sometimes it takes a few weeks to get something out of it...

2011 11 19 1.433

2011 11 20 1.871

2011 11 21 1.523

2011 11 22 1.729

2011 11 23 2.329

2011 11 24 2.849

2011 11 25 3.519

2011 11 26 3.342

2011 11 27 3.030

2011 11 28 2.893

2011 11 29 2.615

2011 11 30 2.446

2011 12 01 3.001

2011 12 02 4.350

2011 12 03 3.948

2011 12 04 3.298

2011 12 05 3.571

2011 12 06 3.729

2011 12 07 2.419

2011 12 08 1.270

2011 12 09 0.991

2011 12 10 1.408

2011 12 11 1.553

2011 12 12 1.973

2011 12 13 1.752

2011 12 14 1.083

2011 12 15 0.596

2011 12 16 0.449

2011 12 17 -0.018

2011 12 18 0.335

2011 12 19 0.836

2011 12 20 0.853

2011 12 21 0.888

2011 12 22 1.378

2011 12 23 2.556

2011 12 24 3.570

2011 12 25 3.824

2011 12 26 3.473

2011 12 27 2.614

2011 12 28 2.607

2011 12 29 2.563

2011 12 30 2.661

2011 12 31 2.865

2012 01 01 1.831

this year...

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao_index.html

if it keeps going down sooner or later it's going to snow or get very cold...

[Jefflaw77]

Regardless of whether or not we had a thunderstorm on the same day, there was a similar cloud in the sky on Aug 10 of last year, we had a hurricane two years in a row...the pattern is completely opposite of what it was last year.

Last year we were staring at wall to wall negative height anomalies over the NAO and PNA regions for the most part (+NAO) with a huge vortex that clearly wasn't budging until January. When I say this year is literally opposite over much of the Atlantic blocking regions, it is literally opposite.

Sure, it may take until mid/late December to come together and things don't always go as planned with mega blizzards starting Dec 1. But the high latitude blocking is something that everybody should get excited about on the medium range guidance. Even with a - PNA pattern, if the blocking retrogrades for a period into the West Based region of Western Greenland and the Davis Straight -- we can benefit.

The only thing I would be concerned about, at this point, is that the MJO forecasts are too bullish and we struggle with tropical forcing...and that the blocking stays more east based. If that is the case, the gradient pattern will be shifted farther north as the southeast ridge will have a chance to build and push the baroclinic zone farther north without the aid of the block keeping it south. But even then, I'd still be confident that the blocking would show up eventually.

You can loop through this for a good look at how, even though there might not be a huge block over Greenland right now...it's getting there..and there are + anomaly ridges all over the high latitudes which is something we haven't seen since 2010.

http://www.meteo.psu.edu/~fxg1/ENSHGTAVGNH_6z/ensloopmref.html

Thanks for your thoughts..

[MJO812]

There are a lot of differences this year compared to this year. Yes the PV is still there but there are signs of it breaking down. Also, there is a lot of cold air in Canada compared to this time last year. Another big one is the NAO and the AO. They were positive last year.

[green tube]

things don't always go as planned with mega blizzards starting Dec 1.

lolllll. that's quality signature material right there.

[weathafella]

Unc can validate or not but sensible wx this year in early December per my memory compares well to december 1960 (for me in Teaneck).

[Dsnowx53]

Regardless of whether or not we had a thunderstorm on the same day, there was a similar cloud in the sky on Aug 10 of last year, we had a hurricane two years in a row...the pattern is completely opposite of what it was last year.

Last year we were staring at wall to wall negative height anomalies over the NAO and PNA regions for the most part (+NAO) with a huge vortex that clearly wasn't budging until January. When I say this year is literally opposite over much of the Atlantic blocking regions, it is literally opposite.

Sure, it may take until mid/late December to come together and things don't always go as planned with mega blizzards starting Dec 1. But the high latitude blocking is something that everybody should get excited about on the medium range guidance. Even with a - PNA pattern, if the blocking retrogrades for a period into the West Based region of Western Greenland and the Davis Straight -- we can benefit.

The only thing I would be concerned about, at this point, is that the MJO forecasts are too bullish and we struggle with tropical forcing...and that the blocking stays more east based. If that is the case, the gradient pattern will be shifted farther north as the southeast ridge will have a chance to build and push the baroclinic zone farther north without the aid of the block keeping it south. But even then, I'd still be confident that the blocking would show up eventually.

You can loop through this for a good look at how, even though there might not be a huge block over Greenland right now...it's getting there..and there are + anomaly ridges all over the high latitudes which is something we haven't seen since 2010.

http://www.meteo.psu...nsloopmref.html

Definitely my concern as well. And that would also make the Pacific less favorable. I am confident that the blocking will show up eventually, but it would be nice to keep seeing it move up on the ensemble data. Often times, our rewards are a little later than what we initially think, kinda like December 2010.

[PB GFI]

Having a NEG NAO and NEG AO is a really nice signal , but that is not the only factor that is going to drive the outcome here Ive been saying it here for a week here if that ridge in the PAC continues its hold on the trough out west , then you pull the trough axis away from the coast and you get a corresponding SE ridge .

Now with a NEG PNA and cold air available in canada thats a great pattern for the upper great lakes and New England . .

a NEG PNA is a nice thing , if you happen to be north of the barroclinic zone . So i just want to wait and see if the PAC ridge stops with its hammer lock on the pattern .

So yes the signals ARE WAY DIFFERENT THAN LAST YEAR , does that guarentee a different outcome ? it should but ive seen some crazy stuff in my life .

[uncle W]

Unc can validate or not but sensible wx this year in early December per my memory compares well to december 1960 (for me in Teaneck).

I remember watching the news on tv and they were saying where is winter...It came with a bang a week later...Hopefully something happens before Christmas this year...

[Guest Pamela]

Unc can validate or not but sensible wx this year in early December per my memory compares well to december 1960 (for me in Teaneck).

KNYC hit 62 F, 64 F, and 55 F on the 5th, 6th, and 7th of December 1960 before the blizzard moved in on the 11th.

[uncle W]

KNYC hit 62 F, 64 F, and 55 F on the 5th, 6th, and 7th of December 1960 before the blizzard moved in on the 11th.

I remember the Friday before the storm...It was 16 degrees with a few flurries...Saturday the forecast was for snow Sunday...The temperature hit 40 on Saturday...It was 34 at midnight when an arctic front passed and stalled to our south...The rest is history...I play lottery numbers from December 11th 13th, 1960...8-9-19-20-21-34...The most numbers that ever came in is four...I've been playing them since the lotto started...

[NorEaster27]

Can you provide some reasoning behind this thought?

http://www.facebook.com/#!/photo.php?fbid=454549277925669&set=a.148807335166533.25889.129478830432717&type=1&theater