Where we're at, where we're going

[usedtobe]

Last night's gfs and euro ensembles showed a similar pattern over the U.S. in the day 10 time range. Both showed a negative PNA and a negative NAO. Both show the ridge in the pacific with plenty of amplitude with a strongly negative PNA look while also showing high heights over Greenland and an area of lower heights to its south close to the 50n 50W position that weenies love. However to me, that low, area of low heights is a little too far east for most of us and it's still November (more on that later). The GFS ensembles:

The euro ensembles.

The plot below clearly shows that when the PNA goes massively negative the NAo also goes negative,

For the mid atlantic, getting cold air into the region gets tougher with a negative PNA and during November, the sign of the PNA index is usually more important than the sign of the NAO index. Let's look at the raw temperature correlations for the two indices first starting with the PNA index. Note the fairly strong negative correlations with temps across the south and positive correlation across the Northwest into western Canada. That means that when the PNA index is negative, warmer than normal temps are likely across the south and colder across the Pac NW.

Now compare those NOvember correlations with those of the NAO index. While there are positive correlations with Temps across the southeast the strongest correlations are over the Atlantic and that the correlations are weaker than those related to the PNA. This time of year, the PNA seems to usually rule the roost.

The slightly above normal heights across the southeast on both the Euro and GFS ensembles are reflecting that fact and the warmer than normal 850 temps being forecast by the euro at 240 hours across much of the southeast is fairly well explained. Even with decent agreement between the models, The day 10 forecast could end up being a lot different but with the both ensembles forecasting a strongly negative PNA, the odds are that days centered around D+10 will not be an extremely cold period across the southeast and Mid Atlantic regions. What happens after the D+10 remains a question mark. If we truly get the negative NAO with a REX or Omega block, the blocking ridge often comes west. That could lead to colder weather in the east.

[Dr No]

Wes, at least there is going to be a fair share of interesting weather coming up in the weeks ahead as things get real blocky. Sunny and seasonable is getting old for a weenie like me

I'm optimistic that things will line up for us to pull at least one out of the hat in the MA in the next 6 weeks.

[usedtobe]

During winter (D-F), the NAO correlation with temps gets much stronger so having a negative nao would probably have a much bigger impact even with a less than great pacific. Here's the winter correlation with temperature. If you compare it to Nove, the difference is impressive.

Now compare that with the November correlation.

[Amped]

GFS and euro in excelent agreement, The -NAO does nothing to stop tbhe warmth. Todays graphic shows the same thing so might as well post yesterdays which will autoupdate. Hopefully a better correlation will start in winter.

[tombo82685]

During winter (D-F), the NAO correlation with temps gets much stronger so having a negative nao would probably have a much bigger impact even with a less than great pacific. Here's the winter correlation with temperature. If you compare it to Nove, the difference is impressive.

Now compare that with the November correlation.

wes whats being shown by the euro and prob the gfs, looks like a true east based -nao which does nothing for us, where the hgts are centered over greenland. For our area we need the center to push more towards baffin island, for the west based -nao

[CAD_Wedge_NC]

GFS and euro in excelent agreement, The -NAO does nothing to stop tbhe warmth. Todays graphic shows the same thing so might as well post yesterdays which will autoupdate. Hopefully a better correlation will start in winter.

Interesting....... You would think that the cross polar flow that is being shown by the models would have the same effect now as later into winter. Of course a milder version due to the time of year. So what's the reasoning.....sun angle????

[usedtobe]

Interesting....... You would think that the cross polar flow that is being shown by the models would have the same effect now as later into winter. Of course a milder version due to the time of year. So what's the reasoning.....sun angle????

part of it is the location of the block associated with the negative NAO which in this case is farther east than you want. The other thing is the heights aren't as low because of the time of year, the atmosphere just plain isn't as cold. The high heights due to the negative PNA make it really hard to get even shallow cold air into the mid atlantic and southeast this time of year.

[skierinvermont]

part of it is the location of the block associated with the negative NAO which in this case is farther east than you want. The other thing is the heights aren't as low because of the time of year, the atmosphere just plain isn't as cold. The high heights due to the negative PNA make it really hard to get even shallow cold air into the mid atlantic and southeast this time of year.

I was thinking it might have to do with wavelengths being a little shorter in November.. you would need a more west-based block to get a good effect on eastern US temperatures.

[usedtobe]

Nothing has changed since yesterdays runs when looking at the ensemble mean products. The neg nao continues to be advertised with a trough in the west with heights still above normal over the southeast. 1st a 156 hr forecast from the 06Z gfs.

Now the 240 hr forecast from the euro ensembles.

Both have a warm look. Based on a question asked by Ellinwood on the CapitalWeatherGang blog asking whether Dec would be the blocky, colder than normal month, I looked at the NCEP D+11 superensemble dates and composited them for Dec. I only used the top 5 years which is way below the number of cases to establish any statistical significance to any results but the composite did support the CWG call for a colder than normal Dec for the east.

[mitchnick]

Nothing has changed since yesterdays runs when looking at the ensemble mean products. The neg nao continues to be advertised with a trough in the west with heights still above normal over the southeast. 1st a 156 hr forecast from the 06Z gfs.

Now the 240 hr forecast from the euro ensembles.

Both have a warm look. Based on a question asked by Ellinwood on the CapitalWeatherGang blog asking whether Dec would be the blocky, colder than normal month, I looked at the NCEP D+11 superensemble dates and composited them for Dec. I only used the top 5 years which is way below the number of cases to establish any statistical significance to any results but the composite did support the CWG call for a colder than normal Dec for the east.

so you're saying there's a chance?

great, because another well known poster is taking a somewhat different angle, and its not like him at all

[usedtobe]

so you're saying there's a chance?

great, because another well known poster is taking a somewhat different angle, and its not like him at all

http://www.americanw...-winter-cancel/

lol, Tell him to wait as the NAO has more impact in winter than in November. I still like snowfall for dca to be in the 8-12 inch range. Add extra for Ji-land.

[CT Rain]

Nice post, Wes. Had almost the exact same one in the New England thread.

I do think that even with a torch possible in the Monday-Wednesday timeframe next week we could see some snow potential once the PNA signal begins to wane and the strong -NAO block remains in place after Thanksgiving.

[Baroclinic Zone]

Nice post, Wes. Had almost the exact same one in the New England thread.

I do think that even with a torch possible in the Monday-Wednesday timeframe next week we could see some snow potential once the PNA signal begins to wane and the strong -NAO block remains in place after Thanksgiving.

Signals are there on the models. Patience this time of year.

[usedtobe]

It is looking like the pattern change that many have been expecting will occur around or just after Thanksgiving. I prefer the slightly slower transition but admit that my thought may be biased somewhat by the look of last night's 240 hr operational euro. I haven't yet seen the euro ensembles. The gfs ensemble mean looks to bring in the cooler air jsut about at thanksgiving especially across new england and the northern mid atlantic states. However, the individual members have lots of variation in the trough locations and flow across the u.s. with some members still holding the trough in the middle of the country while others have more troughing farther east and have a solidly westerly based nao. The one common factor for almost all the ensembles is that they are showing lots of high latitude blocking which makes the december cold idea look pretty good.

[WxUSAF]

Yikes with the 3 of those GFS ensembles that drop the PV down near the Great Lakes! If that was in Dec-Feb, that would be numbing cold! Still would be pretty chilly at the end of Nov as well, I'd think. But also dry, unfortunately.

[Porsche]

Yikes with the 3 of those GFS ensembles that drop the PV down near the Great Lakes! If that was in Dec-Feb, that would be numbing cold! Still would be pretty chilly at the end of Nov as well, I'd think. But also dry, unfortunately.

That will be fine, it can wait to snow till after I come back from the Caribbean(12 night cruise)

[NaoPos]

During winter (D-F), the NAO correlation with temps gets much stronger so having a negative nao would probably have a much bigger impact even with a less than great pacific. Here's the winter correlation with temperature. If you compare it to Nove, the difference is impressive.

Now compare that with the November correlation.

Wes,

With those graphics, is that as close as you can get to the temp anomolies? It's showing lower heights over NE canada/maritimes...In retrospect, wouldn't the NAO cause heigher heights in those aforementioed areas? And with the way the blocking is seting up, cross connecting at the pole, would that force the AO to dip negative and help stunt the Se ridge's influence through the east coast? I'm sure not completely, but to what extent does the Ridge flex it's muscle?

[CAD_Wedge_NC]

Wes,

With those graphics, is that as close as you can get to the temp anomolies? It's showing lower heights over NE canada/maritimes...In retrospect, wouldn't the NAO cause heigher heights in those aforementioed areas? And with the way the blocking is seting up, cross connecting at the pole, would that force the AO to dip negative and help stunt the Se ridge's influence through the east coast? I'm sure not completely, but to what extent does the Ridge flex it's muscle?

Agree....... I believe the models are having a hard time with the strength of the SE ridge. With a block that pronounced and a true cross polar flow, you should see the cold push much deeper than what is being shown.

[usedtobe]

after a couple of cool days coming up. the pattern looks warm until around turkey

day when the pattern looks to get colder. We're still looking at the 240 hr ensemble mean forecast which still has lots of uncertainty in it but it and the gfs shows a strong negative nao and the u.s. trough shifted a little east towards the middle of the country. It looks like a set up that gets the cold into the mid atlantic states.

First the 6-10 day forecast which shows a warmer than normal look to the mid atlantic in the 168 to 240 hr range. Note the ridge in the southwest but that both operational models show a negative ao and nao.

at 240 hrs, the end of the period, the ensemble mean forecast looks much colder as it deepens the trough in the pacific, allows a weak ridge to develop near but just off the west coast that pushed the trough that had been in the west eastward. the heights across the northeast and mid atlantic states by then are forecast to be below normal. Below is the 240 hr euro ensemble mean 500h and 850 temp anomaly forecasts.

Is the pattern change guaranteed. of course not. The models often shift the pattern too quickly which they still could be doing. However, having all the high latutude blocking and a period with a negative epo prior to thanksgiving which should pull some cold air into southern canada and the u.s., it is likely that some of that cold will get into the east especially the northeast. Our southern peeps down in the carolinas may be on the transition zone but so even could my back yard. Still, the solidly negative nao may be a good think for later in dec as it foten goes negative again even if it relaxes and goes positive for a short period.

[HM]

Assuming that the long range guidance is correct, the pattern would become favorable for wintry precipitation. The anafront on Thanksgiving is a nice way to kick off winter, potentially bringing the season's first flakes to the Mid Atlantic. Although, I have seen these turn into junk as we get closer and hone in on the details. A clipper-styled s/w around the 30th is of interest and then potentially Dec 3-5 as the -NAO breaks. Overall, a very active pattern if all goes correctly.

Can DC see a 10" snowstorm like Dec 1973?

[VAwxman]

Assuming that the long range guidance is correct, the pattern would become favorable for wintry precipitation. The anafront on Thanksgiving is a nice way to kick off winter, potentially bringing the season's first flakes to the Mid Atlantic. Although, I have seen these turn into junk as we get closer and hone in on the details. A clipper-styled s/w around the 30th is of interest and then potentially Dec 3-5 as the -NAO breaks. Overall, a very active pattern if all goes correctly.

Can DC see a 10" snowstorm like Dec 1973?

I'm not too excited about the Thanksgiving front yet, though can see how a wave on the front MIGHT do something interesting if things time out just right. I do like the look of the pattern though for some possible wintry stuff at end of nov and sometime a few days into early Dec, as you stated here, with systems forced to dive underneath the block. The East I don't think sees the negative departures that the Plains will see next week, but not like you need it that extreme anyway.

[usedtobe]

I'm not too excited about the Thanksgiving front yet, though can see how a wave on the front MIGHT do something interesting if things time out just right. I do like the look of the pattern though for some possible wintry stuff at end of nov and sometime a few days into early Dec, as you stated here, with systems forced to dive underneath the block. The East I don't think sees the negative departures that the Plains will see next week, but not like you need it that extreme anyway.

I'm with you but also am waiting for the retrogression in the pacific to really start the ball rolling. Without that, all the other changes become tougher.

[HM]

I'm not too excited about the Thanksgiving front yet, though can see how a wave on the front MIGHT do something interesting if things time out just right. I do like the look of the pattern though for some possible wintry stuff at end of nov and sometime a few days into early Dec, as you stated here, with systems forced to dive underneath the block. The East I don't think sees the negative departures that the Plains will see next week, but not like you need it that extreme anyway.

Yeah, like I said, I have seen these anafront situations flop in the short range. It is just always interesting when these -EPO induced cold low level attacks happen when the mid/upper heights haven't responded. I agree about the temperature departures. I think another MJO event will get triggered late Nov/early Dec that propagates eastward through Indonesia. This could swiftly end the cold pattern after December 10th.

[Gibbsfreeenergy]

Yeah, like I said, I have seen these anafront situations flop in the short range. It is just always interesting when these -EPO induced cold low level attacks happen when the mid/upper heights haven't responded. I agree about the temperature departures. I think another MJO event will get triggered late Nov/early Dec that propagates eastward through Indonesia. This could swiftly end the cold pattern after December 10th.

just read this, sounds like my reply to your pm

[HM]

just read this, sounds like my reply to your pm

Yeah this is going to potentially set up a reverse warm anomaly for many in the northern 2/3s of the CONUS, outside of maybe the NW, for a 6-10 day period. As the MJO composites suggest, a phase 3-4-5 transition from where we are now would bring quite an impressive warm shot, outside of the southern states. Once the -NAO block is finished and the EPO goes significantly positive (as wavelengths become longer from both being a winter seasonal progression and the -NAO block going away), it is going to get ugly. At some point in late December, I expect a classic cold Northwest/North regime to return and the ridge to properly place over the Southeast. This classic regime looks to get heightened in early January, possibly setting off some serious storm systems across the Central States!

[nynjpaweather]

Yeah this is going to potentially set up a reverse warm anomaly for many in the northern 2/3s of the CONUS, outside of maybe the NW, for a 6-10 day period. As the MJO composites suggest, a phase 3-4-5 transition from where we are now would bring quite an impressive warm shot, outside of the southern states. Once the -NAO block is finished and the EPO goes significantly positive (as wavelengths become longer from both being a winter seasonal progression and the -NAO block going away), it is going to get ugly. At some point in late December, I expect a classic cold Northwest/North regime to return and the ridge to properly place over the Southeast. This classic regime looks to get heightened in early January, possibly setting off some serious storm systems across the Central States!

Question, if I may:

When you say the -NAO done, are you saying neutral or a full positive NAO feature? Also, what makes you think the MJO will go in a phase 3-4-5 transition? Are we talking the same phases as what is shown at the CPC?

[usedtobe]

Question, if I may:

When you say the -NAO done, are you saying neutral or a full positive NAO feature? Also, what makes you think the MJO will go in a phase 3-4-5 transition? Are we talking the same phases as what is shown at the CPC?

Why wouldn't it? Usually a negative nao lasts 10 days to two weeks, weakens and sometimes disappears before rising back out of the ashed. Even during last year with the massive block and ssw event/s, the nao relaxed briefly in Jan. This year, the qbo is different and is not quite as favorable for a negative nao so it's likely that it will weaken again for awhile. Also, the ssta in regions where the convection would be located during phases 3-5 are warmer than normal so why wouldn't 3-5 again play a role in the pattern evolution? YOu also can see on the aussi site that we have just gone thru one mjo cycle so if and when another develops it should again work into phase 3-5 . Anyway, my opinions which could be wrong as I'm no expert.

[nynjpaweather]

Why wouldn't it? Usually a negative nao lasts 10 days to two weeks, weakens and sometimes disappears before rising back out of the ashed. Even during last year with the massive block and ssw event/s, the nao relaxed briefly in Jan. This year, the qbo is different and is not quite as favorable for a negative nao so it's likely that it will weaken again for awhile. Also, the ssta in regions where the convection would be located during phases 3-5 are warmer than normal so why wouldn't 3-5 again play a role in the pattern evolution? YOu also can see on the aussi site that we have just gone thru one mjo cycle so if and when another develops it should again work into phase 3-5 . Anyway, my opinions which could be wrong as I'm no expert.

Well, see that's why I'm asking if he's referring to the CPC diagrams or not. My question is if the SSTA are supportive of phases 3-5 of the MJO, why has the MJO not even attempt to move into these regions (3 through 5) all Fall? Shouldn't there be some forcing mechanism? I think based on the way the atmosphere is reacting to the ENSO anomalies going on nearly 3 months of the coldest anomalies being towards niño 3 and 1+2, that this is having an effect on the MJO, just as I thought it would. Thus the non-torch winter forecast. I could be wrong, but the atmosphere tends to set up a seasonal pattern, a theme so to speak, and that theme is an MJO in PHASE 5 to 8, a negative NAO, and a hell of a battle with the Southeast ridge with an axis off the Southeast coast.

Now, you mention the QBO as being less favorable for a negative NAO and yet that QBO sure hasn't had much of an impact in the late summer and now through much of this Fall. Don't you think there is something else at play here than just the QBO? I'm looking at stratospheric anomalies, specifically where the warmest portions of the stratosphere is located, and I think that MIGHT be a clue. I used it for three years in forecasting when and if the NAO will go negative, and so far I'm batting around .800. I'm still testing the theory out for another two winters before I can say I'm confident on the idea, but it could explain why the NAO has been and continues to be neutral to negative.

[Isotherm]

Now, you mention the QBO as being less favorable for a negative NAO and yet that QBO sure hasn't had much of an impact in the late summer and now through much of this Fall. Don't you think there is something else at play here than just the QBO? I'm looking at stratospheric anomalies, specifically where the warmest portions of the stratosphere is located, and I think that MIGHT be a clue. I used it for three years in forecasting when and if the NAO will go negative, and so far I'm batting around .800. I'm still testing the theory out for another two winters before I can say I'm confident on the idea, but it could explain why the NAO has been and continues to be neutral to negative.

There's little doubt in my mind that the low geomagnetic activity / aa "hangover" so to speak, from the long duration minimum since 2008, has aided in the weakening of the north atlantic jet and thus makes it easier to block up the pattern in the nern latitudes. The big test this winter is how that particular forcing interacts / behaves wih th more unfavorable factors, like the powerful La Nina, +QBO, etc. Thus far, our pattern seems to be following the more blocky Nina years of the mid 50s than recent +NAO ninas like the late 90s. But we'll see how it progresses. I'm certain that the fast jet will probably create a hostile environment for -NAO blocks, at least in a west based orientation, to persist more than a week or two at a time. That's not to say that can't reoccur throughout the winter though. I expect we will see episodes of good blocking in mid to late winter as well, but likely shorter in duration than the upcoming earl/mid December event since the growing unfavorable Nina signals will be tougher to overcome.

[NinjaWarrior2]

Just messing around with some November telleconnectors in Ninas vs DJF Temps

West-Based -NAO Nov

East-Based -NAO Nov

West-Based +NAO Nov

East-Based +NAO Nov

-PNA Nov

+PNA Nov

-EPO Nov

+EPO Nov

**values and maps taken from Raliegh's East/West Based NAO page and NOAA ESRL**