Medium Range Discussion Winter 2011-12

[Isotherm]

I made a thread in NYC subforum regarding the pattern over the next few weeks or so, but rather than repost I'll just sum up my thoughts here.

Until we can get the MJO into a more conducive octant, we're going to be struggling with -NAO development over the next 10-15 days. PNA values will be reaching a minimum by D 5-7 which should culminate in a strong trough amplifying in the Western US. At week 1 we've got the unholy trifecta in place: -PNA, +AO and +NAO. However, there are clues that the pattern will be changing down the road, probably by the end of the 15 day period noted in this thread. My target time frame for a full scale pattern reversal in the East is week 3-4, essentially around mid December. MJO will be propagating through p 3-6 in the late Nov-early Dec period, which is unfavorable for any polar air penetration into the US. In fact I wouldn't be surprised to see a torch for much of the CONUS the first week of December. With that said, by D15 we see GFS ensembles beginning to retrograde the PAC NW trough into the Gulf of Alaska, and heights rising in the north atlantic as well. MJO should be approaching more conducive phases by Dec 10th-15th, and given the continued low geomagnetic indicators, I expect the -NAO block to initiate fairly easily by week 3-4. This is kind of getting past the time frame for this thread, but the main points I think for the next 15 days -- 1) Strong RNA pattern w/ troughing in the west, burgeoning SE ridge, negative heights flooding the arctic, 2) Western US trough retrograde toward the GOA by day 15; NAO region heights starting to rise 3) MJO in phases promoting warmth/pac orgin air for the remainder of November and early December.

[WidreMann]

I made a thread in NYC subforum regarding the pattern over the next few weeks or so, but rather than repost I'll just sum up my thoughts here.

Until we can get the MJO into a more conducive octant, we're going to be struggling with -NAO development over the next 10-15 days. PNA values will be reaching a minimum by D 5-7 which should culminate in a strong trough amplifying in the Western US. At week 1 we've got the unholy trifecta in place: -PNA, +AO and +NAO. However, there are clues that the pattern will be changing down the road, probably by the end of the 15 day period noted in this thread. My target time frame for a full scale pattern reversal in the East is week 3-4, essentially around mid December. MJO will be propagating through p 3-6 in the late Nov-early Dec period, which is unfavorable for any polar air penetration into the US. In fact I wouldn't be surprised to see a torch for much of the CONUS the first week of December. With that said, by D15 we see GFS ensembles beginning to retrograde the PAC NW trough into the Gulf of Alaska, and heights rising in the north atlantic as well. MJO should be approaching more conducive phases by Dec 10th-15th, and given the continued low geomagnetic indicators, I expect the -NAO block to initiate fairly easily by week 3-4. This is kind of getting past the time frame for this thread, but the main points I think for the next 15 days -- 1) Strong RNA pattern w/ troughing in the west, burgeoning SE ridge, positive heights flooding the arctic, 2) Western US trough retrograde toward the GOA by day 15; NAO region heights starting to rise 3) MJO in phases promoting warmth/pac orgin air for the remainder of November and early December.

I think you mean subarctic or something like that. The Arctic will have plenty of low heights with that +AO. The 10 day Euro has a beautiful vortex NE of Alaska.

[Isotherm]

I think you mean subarctic or something like that. The Arctic will have plenty of low heights with that +AO. The 10 day Euro has a beautiful vortex NE of Alaska.

Thanks for that catch, I meant to say negative heights there. Going to be a long time until we see positive heights flooding the arctic..

[WidreMann]

Thanks for that catch, I meant to say negative heights there. Going to be a long time until we see positive heights flooding the arctic..

The world will probably end before that happens.

[am19psu]

If you buy the tropical forecasts (and I do), I'd suspect we'll see at least a multi-day shot of cold coming into the East after Thanksgiving. As convection moves into the IO, we should see the pattern retrograde with troughing along both coasts and a ridge in the center part of the country. I don't think we'll see the Arctic air mass tapped into, but a few days of -6 to -10 anomalies seem possible for the weekend after Thanksgiving.

[CoastalWx]

If you buy the tropical forecasts (and I do), I'd suspect we'll see at least a multi-day shot of cold coming into the East after Thanksgiving. As convection moves into the IO, we should see the pattern retrograde with troughing along both coasts and a ridge in the center part of the country. I don't think we'll see the Arctic air mass tapped into, but a few days of -6 to -10 anomalies seem possible for the weekend after Thanksgiving.

It's in the works on the ensembles. You can see heights try to rise a bit out west after T-Day. I wonder though, if the changes take a while to occur...like perhaps after Thanksgiving weekend? Still have that monster trough near AK.

[am19psu]

It's in the works on the ensembles. You can see heights try to rise a bit out west after T-Day. I wonder though, if the changes take a while to occur...like perhaps after Thanksgiving weekend? Still have that monster trough near AK.

Agree. I mean, the timing the tropical convection isn't exactly a given for the 11-15 day period.

OTOH, I don't see any major storm systems upcoming for anyone outside the Pac NW/N Rockies/N Plains through the period. I don't see how the pattern allows for snow anywhere east of the Mississippi (except lake effect).

[Srain]

I wouldn't be surprised to see a nice dump in the Cascade/Sierra Nevada Range in the upcoming weekend. If I recall correctly it was about this time last year a potent storm walloped the Cascades and Sierra Nevada Range with some impressive totals. Tis the season…

[CoastalWx]

Agree. I mean, the timing the tropical convection isn't exactly a given for the 11-15 day period.

OTOH, I don't see any major storm systems upcoming for anyone outside the Pac NW/N Rockies/N Plains through the period. I don't see how the pattern allows for snow anywhere east of the Mississippi (except lake effect).

I suppose there might be a small chance up in northern New England early next week as even the euro ensembles kind of hint at a wave of low pressure moving across SNE, but overall I agree. I don't really see much in the way of snow at this time, except possibly in NNE...and that is low confidence right now.

[SnowGoose69]

There continue to be 3 problems showing up on the long range models. The Scandanavian ridge which though it weakens in the next 5-7 days returns, the Phillipines ridge which is notoriously a strong correlator to a SE ridge in the U.S., and the strong GOA vortex. The only good news is the GFS and Euro sort of flatten the SE ridge in the longer range but this may be more a product of a strong Pac Jet blasting west-east across the CONUS than anything else. I'm pushing back any chance of cold/snow now til 12/10(of course those who saw my winter forecast know I never had any cold/snow anyway, however, I'm concerned about this lousy start meaning we may see a reversal, still think that reversal has to occur by 12/10-12/15, if it does not I think this winter is likely toast for anyone east of the Mississippi)

[Srain]

Perhaps a swim in the pool for Thanksgiving...

[usedtobe]

Perhaps a swim in the pool for Thanksgiving...

Doesn't look promising to the mid atlantic for the next two weeks. The GEFS ensembles show some signs of the NAO goign negative but he correlations are so low its hard to give them much credence. The ao forecasts are a little more skillful and they show at negative ao through week two. Probably because of the monster vortex over AK. The pna index does rise out of abyss to neutral but then falls again. The old EPO index which I like pretty much for indicating whether cold air is on the way is massively positive on the progs.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao_index_ensm.shtml

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/new.pna_index_ensm.html

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

I still don't see much through hope through the end of the month.

[SnowGoose69]

Perhaps a swim in the pool for Thanksgiving...

The best news there is the GFS trying to boot the Scandanavian ridge and West Asia trough out late, and the last few GFS runs do finally eject the West Asia trough Days 10-16 and build a ridge there, a semblance of the JB "Cahirs Connection" but that ridge won't do much if the massive trough wants to continue sitting in the GOA.

[uncle W]

this November reminds me of 1975 when we set the record for the warmest November at the time...It came after a brief cold shot minus the snow at the end of October...I had a handfull of analogs this year but only a few were mild into January with colder endings...1971 and 1974 were on the list and as of today they are my top two for now...1973 is not far behind...

[tamarack]

this November reminds me of 1975 when we set the record for the warmest November at the time...It came after a brief cold shot minus the snow at the end of October...I had a handfull of analogs this year but only a few were mild into January with colder endings...1971 and 1974 were on the list and as of today they are my top two for now...1973 is not far behind...

I'd be very happy with another 75-76. Real cold didn't arrive until mid-December, but then came continuing snow and cold (with just a few snap-thaws) almost thru the equinox. Winter in N.Maine ended on 3/20, as my 3/19 low in Ft.Kent of -25 was followed by 50 for the 3/20 high.

[nrgjeff]

Many of the cold and stormy analog years mentioned in the 60s/70s were during -AMO years which are of course cold in the East. This year we hold onto a +AMO. With the NAO trends relaxing compared to the last two winters, look for a less cold outcome this year. East Coast can still gen up some good snows, but the coastal front may break some snow lover hearts on occasion. Believe last two years the -NAO overpowered the still +AMO. This year look for less snow and cold back East with a less negative NAO (just neutral some months). If you hate this forecast remember the last two years rocked so count your blessings.

It is almost Thanksgiving!

[easternsnowman]

Many of the cold and stormy analog years mentioned in the 60s/70s were during -AMO years which are of course cold in the East. This year we hold onto a +AMO. With the NAO trends relaxing compared to the last two winters, look for a less cold outcome this year. East Coast can still gen up some good snows, but the coastal front may break some snow lover hearts on occasion. Believe last two years the -NAO overpowered the still +AMO. This year look for less snow and cold back East with a less negative NAO (just neutral some months). If you hate this forecast remember the last two years rocked so count your blessings.

It is almost Thanksgiving!

We still don't know what the NAO will do.

[Bob Chill]

The east can still get decent events w/ a neutralish NAO and AO. The persistent -pna isn't that big of a deal considering it's November still. The se ridge isn't that big of a deal either. It's flexing and relaxing instead of building and torching.

We can do ok with just a +pna and neutralish ao/nao indexed just by having the trough positioned right. Don't need true polar air to get snows in Dec/Jan. Canadian air can do just fine.

Pretty much a stating the obvious post but it is important to not get all hung up on NAO/AO. The current setup is a perfect example of how a -nao doesn't really mean anything for the east when the rest pattern isn't cooperating.

I think I remember some posts back on eastern some years back talking about the pna and how a persistent anomaly generally flips in 6+/- week intervals or something like that. Pretty foggy memory of the reasoning but I don't think what we are seeing now is a reason to hit the panic button. Heck, I'm enjoying the extended outdoor weather were having. It's been a really nice fall so far.

[usedtobe]

Many of the cold and stormy analog years mentioned in the 60s/70s were during -AMO years which are of course cold in the East. This year we hold onto a +AMO. With the NAO trends relaxing compared to the last two winters, look for a less cold outcome this year. East Coast can still gen up some good snows, but the coastal front may break some snow lover hearts on occasion. Believe last two years the -NAO overpowered the still +AMO. This year look for less snow and cold back East with a less negative NAO (just neutral some months). If you hate this forecast remember the last two years rocked so count your blessings.

It is almost Thanksgiving!

For the dc and Baltimore area, last year was pretty bad. We didn't rock.

[nrgjeff]

Re the NAO: The trend is your friend, until it ends. The negative regime has ended and we are variable; it will continue through winter. This week the natty bulls just lost their shirts!

We still don't know what the NAO will do.

[BethesdaWX]

Many of the cold and stormy analog years mentioned in the 60s/70s were during -AMO years which are of course cold in the East. This year we hold onto a +AMO. With the NAO trends relaxing compared to the last two winters, look for a less cold outcome this year. East Coast can still gen up some good snows, but the coastal front may break some snow lover hearts on occasion. Believe last two years the -NAO overpowered the still +AMO. This year look for less snow and cold back East with a less negative NAO (just neutral some months). If you hate this forecast remember the last two years rocked so count your blessings.

It is almost Thanksgiving!

Isn't that only a summer season correlation though? How does the +AMO lead to warm eastern winters? SSTAs off the East coast are actually below average in many areas. http://www.osdpd.noaa.gov/data/sst/anomaly/2011/anomnight.11.14.2011.gif

How can you assert the -NAO phase has ended? We're just 2 weeks into november. I thought warm SSTAs in the North Atlantic were one of the culprits for a deep -NAO and that cooler North Atlantic SSTAs did not promote as healthy of a -NAO? The AMO is cooler this winter so I'm going by the assumption that you're in the solar activity camp?

The -NAO in the 1960s and early 1970s during the -AMO kind of mystifies the warm SSTAs being a dominant forcing on the NAO.

[nrgjeff]

The AMO correlation is weaker in winter but valid. Re cooler at the immediate coast: Local SSTs do not drive hemispheric or continental patterns. Only local patterns, like a colder breeze when onshore, can be deduced.

The smoothed line graph for NAO is near neutral the last several months. SSTs can prolong or enhance the NAO, but are not considered initial drivers. The NAO trend is clearly neutral and it tends to continue several months at a time.

Though the AMO is cooler v LY, the record -NAO is now neutral. Net result is warmer. I'm not cancelling winter in Nov. Just not bulled up.

The 1970s marked the brief overlap when BOTH the multi-decadal Pacific and Atlantic oscillations were in cool phases. Winter wx lovers just wait about a decade or so and we'll be there again.

Isn't that only a summer season correlation though? How does the +AMO lead to warm eastern winters? SSTAs off the East coast are actually below average in many areas. http://www.osdpd.noa....11.14.2011.gif

How can you assert the -NAO phase has ended? We're just 2 weeks into november. I thought warm SSTAs in the North Atlantic were one of the culprits for a deep -NAO and that cooler North Atlantic SSTAs did not promote as healthy of a -NAO? The AMO is cooler this winter so I'm going by the assumption that you're in the solar activity camp?

The -NAO in the 1960s and early 1970s during the -AMO kind of mystifies the warm SSTAs being a dominant forcing on the NAO.

[Ginx snewx]

Re the NAO: The trend is your friend, until it ends. The negative regime has ended and we are variable; it will continue through winter. This week the natty bulls just lost their shirts!

Pretty broad assumption, do you have statistical correlation to your theory?

[BxEngine]

Re the NAO: The trend is your friend, until it ends. The negative regime has ended and we are variable; it will continue through winter. This week the natty bulls just lost their shirts!

I thought there was a decent correlation with a summertime -nao and a return to an -nao in the winter after a move to neutral or positive? Or am I thinking of something else?

[Ginx snewx]

I thought there was a decent correlation with a summertime -nao and a return to an -nao in the winter after a move to neutral or positive? Or am I thinking of something else?

Very correct sir.

[okie333]

Very correct sir.

But much more true about the AO... and both indices were very low this summer.

[FEFD17]

Last year north east NY could not buy a snowstorm of more than 7 inches at a time( or so it seemed). We were getting, what I call a half steady nickel and dime events. It was a real good year for anything south of about Albany maybe a little further south ,but not much getting the jackpot storms. The blocking pattern was awful to getting the monster storms. I rely on snow and storms for my work. I hope the models are wrong right now and it turns around a week or two before Christmas and have at least a couple good hits.

[ORH_wxman]

It doesn't look like (to me anyway) that we will have a chance at a huge pattern shift to colder in the east (sustained) until at least a week deep into December, perhaps two weeks in. The extreme vortex in Alaska doesn't really have a good reason to be dislodge before then as a robust MJO wave enters phases 3/4 which actually supports keeping it there. Once it moves out of those phases, then other factors can help in dislodging and perhaps the MJO itself if it can remain strong into phase 6.

Until then, the cool downs should be transient in nature.

[usedtobe]

It doesn't look like (to me anyway) that we will have a chance at a huge pattern shift to colder in the east (sustained) until at least a week deep into December, perhaps two weeks in. The extreme vortex in Alaska doesn't really have a good reason to be dislodge before then as a robust MJO wave enters phases 3/4 which actually supports keeping it there. Once it moves out of those phases, then other factors can help in dislodging and perhaps the MJO itself if it can remain strong into phase 6.

Until then, the cool downs should be transient in nature.

That's pretty much what I posted in the Mid Atlantic forum.

[ORH_wxman]

That's pretty much what I posted in the Mid Atlantic forum.

Yes I think I saw that in one of the threads. Zwyts bumped the winter thread and we talked it about it more. Perhaps you have some more add in...as you know the snow patterns there better than I would, but it definitely seems to be nothing like a snow pattern (even for up here in New England) over the next few weeks...some of our elevated spots and areas with more latitude can probably get a snow event during a transient cold snap but sustained cold and sustained winter threats do not look to be in the cards as we enter December...hopefully by mid-month we see the pattern more able to support them.