AAM and GWO Discussion

[HM]

Pretty impressive display of a Rossby Wave Train (RWT) during the 11/15-20 period across the western Pacific and Asia. The classic thing about it was how nicely it fit into the whole "tropical forcing shifting back into the Indian Ocean" thing. If you've noticed even worse model consistency than normal over the last 7 days, this is likely one of the reasons why, but certainly not the only reason.

Here is a 150mb vector map on 11/17 with a classic Ed Berry circulation (rip off) drawing (minus the black dashes) showing the RWT:

Also a 11/17 200mb height anomaly map:

Here are the AAM transports during this time with a lame black line from me showing you the poleward propagation over the course of the last 20 days of +AAM flux:

Next step is usually circumglobal ridges with enhanced 30S-30N easterlies. This takes the GLAAM down overall.

Here are the 250mb zonal wind anomalies graphed out along latitude for 11/17 and 11/21. Notice on 11/17 (the heart of the RWT) the anomalies at 30S-30N are not quite as impressive as on 11/21. On 11/21, you get a clear appreciation for the enhanced westerlies in the Mid Latitudes of the SH and NH along with the enhanced easterlies at 30N and 30S.

Long, nerdy, story short....the MJO, and all associated attributes, is still heavily influencing the pattern.

Nerd interlude over...carry on.

[ORH_wxman]

I will condense this for the layman....this pattern sucks azz for the east coast through early Dec when you extrapolate it out.

[HM]

I will condense this for the layman....this pattern sucks azz for the east coast through early Dec when you extrapolate it out.

LOL

Yes it sucks for Arctic cold and North Atlantic blocking when you continue to move forward.

The one saving grace is the shorter wavelengths of late autumn. If you go back up to the first image with the Ed Berry rip off KWT H's and L's, imagine those swirls moving northeastward quickly. You can see how that would perfectly place the low anomaly across the eastern US. That faster, more chaotic, motion was clearly seen on global water vapor loops, too. You could see the enhancement of momentum coming.

That transfer of momentum from the Tropics will certainly add speed to the westerlies and definitely explains the warmth coming up. However, the state of the N PAC circulation will slowly retrograde, allowing additional low anomalies to drop into the eastern US. If this were mid-winter, this would be a disaster coming up for snow/cold lovers.

[HM]

I just wanted to add the 11/21 Relative AAM chart:

The positive anomalies now in the westerlies (denoted by the plus symbol) and the negative anomalies in the Subtropics (denoted by the minus symbol) fit nicely with the u-anomaly charts above.

Notice that during the time of the -NAO period from late October into mid-November, there was a weak -AAM anomaly propagating poleward. This poleward negative anomaly with a positive anomaly building in the equatorial regions is the exact opposite scenario currently. Circumpolar troughs develop near 30N with a weakened Mid Latitude gradient and zonal wind. This is a better environment for polar blocking.

[CoastalWx]

Good stuff HM. We aren't going to be seeing any blocking for a while, but hopefully things change a bit later in Dec or Jan.

[HM]

Good stuff HM. We aren't going to be seeing any blocking for a while, but hopefully things change a bit later in Dec or Jan.

This pattern coming up is certainly not notorious for big storms, but it can produce East Coast snowfall. In fact, as the Alaskan Vortex continues to retrograde in early December and the ridge gets pumped up in the West a bit, lows will be able to break across the East. Sure, there will not be Arctic Air but there will be sufficiently cool air for snow.

The 12/6-12 period (I'm obviously skipping the late November/first few days of December potentials) has interest for a possible low-end snow event for the Mid-Atlantic and New England. I am not quite sure yet if it can be more than that for any place, given the pattern in place. I could even see snow into Maryland/DC at some point in this period.

As the forcing returns to phase 7-8, I expect cold air to plunge into the Plains / Midwest perhaps toward the 20th. I think this may cause a decent New England snowstorm 12/20-23 and probably mean a cold Christmas for most locations.

[Amped]

Here's an explaination graphic from http://www.esrl.noaa.gov/psd/map/clim/gsdm.composites.shtml

[Rainman]

The planviews were great for illustrative purposes, HM. It makes it easier for us normal folk (I thought I was a nerd, but maybe I'm not after all ) to visualize things. It also makes the more dynamic-based stuff (e.g. AAM) easier to understand conceptually. Thanks for the educational post.

[HM]

Here's an explaination graphic from http://www.esrl.noaa...omposites.shtml

Thanks for posting that information in this thread. It's a good idea for sure.

The planviews were great for illustrative purposes, HM. It makes it easier for us normal folk (I thought I was a nerd, but maybe I'm not after all ) to visualize things. It also makes the more dynamic-based stuff (e.g. AAM) easier to understand conceptually. Thanks for the educational post.

No problem man; I can understand completely how this stuff can seem pretty confusing at first. I thought the last few weeks were a perfect way to understand these concepts and just wanted to bring it to the board's attention.

The EPO response we are about to get is related to this stuff as well:

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

However, we aren't done with "torches" by any means. Another widespread shot is coming mid-December.

[am19psu]

[pcbjr]

Thanks, HM. Very interesting, but not too hopeful for the deep SE folks. We need a season-long gift from Santa, I fear ....

[HM]

This pattern coming up is certainly not notorious for big storms, but it can produce East Coast snowfall. In fact, as the Alaskan Vortex continues to retrograde in early December and the ridge gets pumped up in the West a bit, lows will be able to break across the East. Sure, there will not be Arctic Air but there will be sufficiently cool air for snow.

The 12/6-12 period (I'm obviously skipping the late November/first few days of December potentials) has interest for a possible low-end snow event for the Mid-Atlantic and New England. I am not quite sure yet if it can be more than that for any place, given the pattern in place. I could even see snow into Maryland/DC at some point in this period.

As the forcing returns to phase 7-8, I expect cold air to plunge into the Plains / Midwest perhaps toward the 20th. I think this may cause a decent New England snowstorm 12/20-23 and probably mean a cold Christmas for most locations.

Well it appears that the 12/6-12 period did bring a coastal low and cold shot (ongoing). Looks like if you didn't have elevation on your side, the snow amounts on the 7th-8th are going in the book as traces. However, I am glad that this did get down into the Mid-Atlantic, even if it wasn't anything memorable.

The models are now keying in on the 12/18-20 period for a Midwest cyclone and Arctic plunge. It is very phase 7 looking, per the MJO composites. The semi-permanent E PAC ridge feature will likely expand as wavelengths elongate toward winter. The PNA will likely be a viable contender through the holidays and the start of January with perhaps another cold shot / snow potential near New Years.

The original forecast for a "decent New England snowstorm 12/20-23" still holds; although, I'd like to make a few adjustments. Baroclinic zone likely arrives 12/20-22, so the threat is more like 12/22-24. Also, it could manifest as another fast-moving coastal storm, possibly favoring the interior Mid-Atlantic and New England.

[QVectorman]

Notice that during the time of the -NAO period from late October into mid-November, there was a weak -AAM anomaly propagating poleward. This poleward negative anomaly with a positive anomaly building in the equatorial regions is the exact opposite scenario currently. Circumpolar troughs develop near 30N with a weakened Mid Latitude gradient and zonal wind. This is a better environment for polar blocking.

HM, I'm trying to learn how to use the AAM chart as you do, so looking at the most recent AAM chart can one say that a -AAM anomaly is propagating poleward and it could help produce a -NAO period in the coming weeks? Based on your statement above or am I misunderstanding you. Thanks!

I think this is a great educational thread, it would be great if we could keep it going as the winter goes on and you could give us your insight into to the different maps/graphs you have presented as they change over the winter.

[HM]

HM, I'm trying to learn how to use the AAM chart as you do, so looking at the most recent AAM chart can one say that a -AAM anomaly is propagating poleward and it could help produce a -NAO period in the coming weeks? Based on your statement above or am I misunderstanding you. Thanks!

I think this is a great educational thread, it would be great if we could keep it going as the winter goes on and you could give us your insight into to the different maps/graphs you have presented as they change over the winter.

I am sorry I missed this post. Yes, I'll try and post some periodic updates when there is something interesting going on. For the time being, outside of a shift equatorward of the mean AAM anomalies, there is nothing to note. Forcing has been stagnant and actually coming from multiple areas.

To get an idea of how AAM anomalies can reflect global circulation, below is the year AAM chart. Notice early winter last year had the exact opposite anomaly pattern as late winter last year (when things changed to warmer in Feb) and the start of this winter:

We'll see how things progress this week.

[HM]

Latest GWO Numbers are quite interesting. This is truly a major AAM spike in progress from the IO convection. The graphics

haven't updated yet to reflect these numbers (only updated through 12/24).

362 2011 12 23 -0.14 0.32 15 3.5 0.3

363 2011 12 24 0.01 2.05 20 4.5 2.1

364 2011 12 25 0.37 3.48 20 4.5 3.5

365 2011 12 26 0.85 3.77 20 4.5 3.9

366 2011 12 27 1.27 2.43 25 5.5 2.7

[QVectorman]

You are using the GWO FNL numbers correct? So what is the difference between the GWO and GWO FNL? I noticed they are different for the phase and amplitude each day.

[kylemacr]

You are using the GWO FNL numbers correct? So what is the difference between the GWO and GWO FNL? I noticed they are different for the phase and amplitude each day.

My guess is that regular GWO uses a model analysis field and FNL is the final NCEP reanalysis, once it has been attacked by the reanalysis machine... I base this on the fact that the FNL data lag the non-FNL data.

EDIT: ... and I immediately take this back since the lag seems to be the other way around! oops!

[HM]

You are using the GWO FNL numbers correct? So what is the difference between the GWO and GWO FNL? I noticed they are different for the phase and amplitude each day.

I did use the GWO FNL file to get some of the early data. I believe the raw data will then get converted using a 5-day mean:

http://www.esrl.noaa.gov/psd/map/clim/test_maproom.html

Which will explain why, for example, the 12/24 numbers came down a bit from the original numbers. So yes, there will likely be an adjustment downward, but this is still the biggest raw tendency/spike in AAM.

[tombo82685]

I did use the GWO FNL file to get some of the early data. I believe the raw data will then get converted using a 5-day mean:

http://www.esrl.noaa...st_maproom.html

Which will explain why, for example, the 12/24 numbers came down a bit from the original numbers. So yes, there will likely be an adjustment downward, but this is still the biggest raw tendency/spike in AAM.

not really familiar with the gwo, but what does this mean in terms of conus weather?

[okie333]

not really familiar with the gwo, but what does this mean in terms of conus weather?

It means the atmosphere's hungry, and the Polar Vortex looks mighty tasty.

[Amped]

Nice, this has much more potential to change the pattern than the SSW IMO. More momentum means somethings got to give.

[am19psu]

Latest GWO Numbers are quite interesting. This is truly a major AAM spike in progress from the IO convection. The graphics

haven't updated yet to reflect these numbers (only updated through 12/24).

362 2011 12 23 -0.14 0.32 15 3.5 0.3

363 2011 12 24 0.01 2.05 20 4.5 2.1

364 2011 12 25 0.37 3.48 20 4.5 3.5

365 2011 12 26 0.85 3.77 20 4.5 3.9

366 2011 12 27 1.27 2.43 25 5.5 2.7

So, it looks to me at least, the IO AAM response we'd been talking about for weeks is occurring is a little earlier than expected. Instead of Jan 10-15, we'll see it Jan 3-7. Once convection moves back over the Maritime Continent around Jan 2-5, we'll see the warmth return to the East around Jan 10 or so. I don't see any reason to talk about a wholesale "pattern change" based on the forecasted MJO evolution.

[HM]

So, it looks to me at least, the IO AAM response we'd been talking about for weeks is occurring is a little earlier than expected. Instead of Jan 10-15, we'll see it Jan 3-7. Once convection moves back over the Maritime Continent around Jan 2-5, we'll see the warmth return to the East around Jan 10 or so. I don't see any reason to talk about a wholesale "pattern change" based on the forecasted MJO evolution.

My best guess is that this IO response is Kelvin Wave induced and that the actual "MJO" in phase 5 is more or less the Walker Cell / ENSO-forcing. The stagnant / looping nature in ph4-5 is one clue for this along with the existence of h85 convergence / -h2 winds there allowing for coherence. So really, the MJO is not in the IO or Indonesia. It will be interesting to see how this KW interacts with the Walker Cell and if we can send a CHI wave across phase 7-8-1 down the road (most models do propagate the MJO away from phase 5, which is just as important as having it being coherent in phase 7-8-1).

So, I am not so sold on a blowtorch returning. However, I do agree that behind the cold blast, we'll warm up before the next cold blast. But I think the western ridge will remain semi-permanent and cold blasts will be more frequent than December (which isn't that much of a stretch).

The other implication will be the next stratospheric disturbance potential.

[nzucker]

My best guess is that this IO response is Kelvin Wave induced and that the actual "MJO" in phase 5 is more or less the Walker Cell / ENSO-forcing. The stagnant / looping nature in ph4-5 is one clue for this along with the existence of h85 convergence / -h2 winds there allowing for coherence. So really, the MJO is not in the IO or Indonesia. It will be interesting to see how this KW interacts with the Walker Cell and if we can send a CHI wave across phase 7-8-1 down the road (most models do propagate the MJO away from phase 5, which is just as important as having it being coherent in phase 7-8-1).

So, I am not so sold on a blowtorch returning. However, I do agree that behind the cold blast, we'll warm up before the next cold blast. But I think the western ridge will remain semi-permanent and cold blasts will be more frequent than December (which isn't that much of a stretch).

The other implication will be the next stratospheric disturbance potential.

What do you think is causing the +PNA to appear so suddenly on models, given that the MJO remains in the unfavorable phases? Could the MT wave/increased heights in the upper levels over Asia have turned the tables on the Pacific pattern, even if the PV remains over Alaska?

[HM]

What do you think is causing the +PNA to appear so suddenly on models, given that the MJO remains in the unfavorable phases? Could the MT wave/increased heights in the upper levels over Asia have turned the tables on the Pacific pattern, even if the PV remains over Alaska?

I think more simply, it is the GWO response into phase 4-6.

Link to GWO data and composites:

http://www.esrl.noaa.gov/psd/map/clim/gsdm.composites.shtml

Here is a 500mb anomaly chart for phase 5 in the last 10 days of December.

[QVectorman]

I'm not by any means even a novice at this but I know everyone talks about MT events and it appears the largest one so far this season is in progress. Asian and South American MT event. Are certain geographic MT events more favorable for the Con. US? If someone would like to elaborate that would be great!

[okie333]

I'm not by any means even a novice at this but I know everyone talks about MT events and it appears the largest one so far this season is in progress. Asian and South American MT event. Are certain geographic MT events more favorable for the Con. US? If someone would like to elaborate that would be great!

<image removed>

Asian is the best.

[HM]

I'm not by any means even a novice at this but I know everyone talks about MT events and it appears the largest one so far this season is in progress. Asian and South American MT event. Are certain geographic MT events more favorable for the Con. US? If someone would like to elaborate that would be great!

The East Asian Mountain Torque promotes an extension of the Pacific Jet and a PNA ridge down the road. That's always why seasonal / long range forecasters are looking out for these. They also promote stratospheric disturbances through upwelling / remote wave breaking.

Unfortunately, the good folks at the ESRL/CDC haven't updated the reanalysis AAM/GWO beyond Christmas but the FNL numbers continue to indicate a high AAM regime / GWO orbit through 6-7-8. Very El Niño-like atmosphere in progress and I believe this will verify my call of a relative AAM max in December. This was one of the reasons I thought the CONUS would look strange this December, temperature-anomaly-wise; but unfortunately, I was wrong about the cold mid nov-early dec period.

[HM]

Reanalysis:

19716 2011 12 24 -0.15 1.12 20 4.5 1.1

19717 2011 12 25 0.11 2.80 20 4.5 2.8

19718 2011 12 26 0.51 2.76 20 4.5 2.8

19719 2011 12 27 0.77 1.61 25 5.5 1.8

19720 2011 12 28 0.91 0.43 25 5.5 1.0

19721 2011 12 29 0.90 -0.20 30 6.5 0.9

19722 2011 12 30 0.88 -0.40 35 7.5 1.0

19723 2011 12 31 0.81 -0.39 35 7.5 0.9

19724 2012 1 1 0.85 1.41 25 5.5 1.6

FNL Data:

357 2011 12 24 0.01 2.05 20 4.5 2.1

358 2011 12 25 0.37 3.48 20 4.5 3.5

359 2011 12 26 0.85 3.70 20 4.5 3.8

360 2011 12 27 1.27 2.58 25 5.5 2.9

361 2011 12 28 1.49 0.88 25 5.5 1.7

362 2011 12 29 1.51 -0.40 30 6.5 1.6

363 2011 12 30 1.42 -0.78 35 7.5 1.6

364 2011 12 31 1.35 -0.34 30 6.5 1.4

365 2012 1 1 1.36 0.60 25 5.5 1.5

366 2012 1 2 1.51 1.78 25 5.5 2.3

Looks like another round of positive tendency started. This is quite an impressive +AAM peak.

Interestingly, and possibly related, the latest ECMWF and JMA MJO forecasts have a brief coherence into phase 8 now:

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/clivar_wh.shtml

[usedtobe]

Reanalysis:

19716 2011 12 24 -0.15 1.12 20 4.5 1.1

19717 2011 12 25 0.11 2.80 20 4.5 2.8

19718 2011 12 26 0.51 2.76 20 4.5 2.8

19719 2011 12 27 0.77 1.61 25 5.5 1.8

19720 2011 12 28 0.91 0.43 25 5.5 1.0

19721 2011 12 29 0.90 -0.20 30 6.5 0.9

19722 2011 12 30 0.88 -0.40 35 7.5 1.0

19723 2011 12 31 0.81 -0.39 35 7.5 0.9

19724 2012 1 1 0.85 1.41 25 5.5 1.6

FNL Data:

357 2011 12 24 0.01 2.05 20 4.5 2.1

358 2011 12 25 0.37 3.48 20 4.5 3.5

359 2011 12 26 0.85 3.70 20 4.5 3.8

360 2011 12 27 1.27 2.58 25 5.5 2.9

361 2011 12 28 1.49 0.88 25 5.5 1.7

362 2011 12 29 1.51 -0.40 30 6.5 1.6

363 2011 12 30 1.42 -0.78 35 7.5 1.6

364 2011 12 31 1.35 -0.34 30 6.5 1.4

365 2012 1 1 1.36 0.60 25 5.5 1.5

366 2012 1 2 1.51 1.78 25 5.5 2.3

Looks like another round of positive tendency started. This is quite an impressive +AAM peak.

Interestingly, and possibly related, the latest ECMWF and JMA MJO forecasts have a brief coherence into phase 8 now:

http://www.cpc.ncep....clivar_wh.shtml

The is the 1st time this season that I've started to get interested in the pattern if the models are right in the re-amplfication of the pattern on day 10. I don't see any snow chances south of 40 before then but think sometime around the 14-16 jan period could be interesting if we get a big storm that tries to put some higher heights over greenland for a few days. The forecast pattern certainly looks a little better than it has and the polar vortex does appear to be weakening.