In Depth Model Discussion and Summaries

[David Morse]

 

Nov500anom.png

 

 

NovSoFar.gif

 

Well all the key features are there

 

Hi SK,

 

I'm sure you've read much deeper into this than I have; but I do have a few questions about your analysis of the two 500mb charts.

 

On the face of it it looks convincing; but perhaps you could support your position more by showing composite anomalies from Novembers preceding a mild winter and an average winter so we can see the differences?

 

Secondly you say that the "key features are in place"; but even a casual glance shows remarkable differences between the long term composite and this November's composite? For instance the Atlantic low anomaly is aligned along a North West - South East axis. In the long term chart the low anomaly is aligned on an East-West axis. A substantial difference would you agree?

 

Thirdly the high anomalies are in quite different positions: the Siberian high anomaly is much further west and there is an intense high anomaly in the high Arctic centred on the Canadian / Alaska border; this has no equal in the long term chart.

[snowking]

Hi SK,

 

I'm sure you've read much deeper into this than I have; but I do have a few questions about your analysis of the two 500mb charts.

 

On the face of it it looks convincing; but perhaps you could support your position more by showing composite anomalies from Novembers preceding a mild winter and an average winter so we can see the differences?

 

Secondly you say that the "key features are in place"; but even a casual glance shows remarkable differences between the long term composite and this November's composite? For instance the Atlantic low anomaly is aligned along a North West - South East axis. In the long term chart the low anomaly is aligned on an East-West axis. A substantial difference would you agree?

 

Thirdly the high anomalies are in quite different positions: the Siberian high anomaly is much further west and there is an intense high anomaly in the high Arctic centred on the Canadian / Alaska border; this has no equal in the long term chart.

 

Hi David, and sorry for taking so long to get back to you on this.

 

Let me start by addressing your second and third points. When matching composites across the space of 30 days such as this (and especially when you then factor in adding multiple years together with the historical composites) you are very very unlikely to ever get an exact match. I think it is also worth bearing in mind that these are 500mb composites. We are not looking for an exact match pixel for pixel, what we are interested in is the overall longwave pattern insinuated. In this instance I have picked out those key longwave features, the Aleutian low, the Scrussian high, the amplified pattern up across the US, and indeed the troughing to the West of the UK. These may not match pixel for pixel across the two composites but you can certainly see the longwave pattern matches very well.

 

As mentioned in my previous post these features all align well to Cohen's expected climatology following a high SAI, and to address a further point, the fact that the positive anomaly around Scandinavia is further west than the baseline composite is not a bad thing, it's actually a very positive thing stratospherically.

 

As for previous November composites from milder years lets take a look at two of the more nightmare years as far as collides are concerned - 2013 and 1988, with this years November to date composite alongside:

 

 

I'm sure I don't need to point out the differences here, but notice the much flatter pattern overall, with the loss (and indeed reversal) of our positive Scrussian anomaly, and vice versa around the Aleutians too.

 

I hope this helps and if there are any further queries do not hesitate to ask

 

SK

[David Morse]

Hi SK,

 

Thanks for the reply; I suppose what I'm looking at is something which I'd think should be more indicative across the years. I was talking about the axis along which the low anomalies lie. In my mind these indicate the nature of the development of depressions in the lower atmosphere over time; in other words they are a pattern of behaviour. We know that just small changes in the direction of any factor can impact the localised weather massively.

 

It would be interesting to see a correlation between the exact axis along which anomalies lie and their location and the consequential seasonal averages following.

 

What we've seen recently is a disrupted PV and weak blocking from the east; but the track of Atlantic depressions has continually brought warm air across these Islands and frustrated the easterly blocking. I see this as a battle between the easterly blocking which has simply not been strong enough to over come Atlantic depressions that have been persistent, slow moving and often deep and large which are forming anomalously across a north west / south east axis and acting like a wall preventing encroachment of the cold east. In detail its because the depressions are moving air up from the far south east and keeping temps high here; and the East has to over come that amount of energy to bust through.

 

In the historical averages you put up, the low anomalies in the Atlantic are most definitely concentrated in a different and cooler direction; lows tracking in a direct west to east axis would be more readily deflected to the north by easterly blocking allowing ingress of those easterlies.

 

One indicator that I saw consistently in 2009 and 2010 was the strong development of a the "Polar Express" caused by the Greenland High and an intense Scandinavian Low. Both cold winters were preceded by this and I remember seeing it appear consistently in the charts in FI and far in advance of the cold arriving; and in both the years the cold arrived from the north first and then the intense cold followed from the east. 

 

These lows were from the Atlantic and were getting deflected north to settle over Scandinavia and then sending cold air south.

 

So I really don't see this same set up or even close to it and I feel that is a paramount detail that needs to be in place before true cold arrives.

 

Yes the disrupted PV is a good indicator; but I'm sure people are choosing to overlook the details which I feel are a better signal for timing. I can't see any chance of cold for the foreseeable future because in my view; the details aren't in place.

[snowking]

Hi David,

 

I certainly take your point, but I think it is important to remember what we are looking here are not strictly tropospheric precursors, but stratospheric precursors (which later lead to tropospheric effects), and it is these which many are becoming more excited about. I don't have the links to Cohen's work to hand but I am sure if you wanted to read more in to these then somebody will be kind enough to provide a link

 

I think the most important point to take is that nobody interested in the stratospheric season this year is expecting much to happen of wintry note tropospherically until later in December or even in to January, but what we are specifically looking for here are tropospheric patterns which lead to stratospheric wavebreaking. These happen to be the Scandinavian(ish) high and Aleutian low in tandem. I see you mention 2009, if we take a look at the November composite for 2009:

 

 

Notice once again we do not necessarily end up with the features in the exact same area but they are there nonetheless - the Scandi high/Aleutian low combination.

 

So, if all we are interested in is those two features, why would I draw attention to some of the other features of my original composite, such as the troughing to the West of the UK and the amplified pattern in the USA. Well the very purpose of creating a composite in forecasting is that you believe that the background features used to derive the composite years should ensure a close match as you progress through the current season to the historic composite. The standout feature was the tropospheric Scandi High/Aleutian Low combination, which we know from Cohen's work is a derivative of a high Snow Advance Index, and this pointed towards the likelihood of some serious stratospheric vortex disruption through the season. But the years were not chosen because of this tropospheric signature, they were chosen because they matched this years setup in terms of ENSO, QBO and OPI. As stated in my previous post, you are unlikely to get a pixel for pixel match between composites, but the overall longwave pattern is what we are interested in and so to see that, as we have progressed through November, that we see the same basic longwave setup as the composite years predicted heightens my confidence in the likelihood of a colder than average winter overall, whilst we of course maintain the Scandi high/Aleutian low signature.

 

Of course as ever this is simply a forecast and nothing in meteorology is guaranteed, but to come back to the point that every year which has finished with a sub -1 OPI has also featured a below average CET (and the consistent theme through that is a below average January in every year), and then adding this factoring in to the fairly accurate composite forecast for November, confidence is raised. In unison with this the disturbed nature of the vortex continues to encourage too.

 

It may also be worth re-iterating that we should have the expectation of the vortex strengthening a little through December tropospherically, and this is in line with expectations.

 

SK

[Vorticity0123]

Now that the models are showing some interesting synoptics in the long term (i.e. a Greenland block), it seems that a pattern change is possible in the near future (about 10 days away). I will try to give an in-depth look on what indicators point toward a pattern change. Given that I am covering some unexplored terrain for myself in this post, any corrections/comments would be very welcome.

 

GWO

 

The first thing that will be discussed is the GWO (Global wind oscillation). A very good description in what it exactly is, can be found in the Netweather guides, with the link given below:

 

https://forum.netweather.tv/topic/52083-gwo-and-global-angular-momentum/

 

In short, a GWO in phase 6 to 7 indicates a westerly wind tendency at the midlatitudes (in other words: the winds are flowing more from the west than usual, giving rise to a more zonal pattern). On the other hand, phases 2 and 3 indicate an easterly wind tendency at the midlatitudes (the winds do have a tendency to be less westerly than usual, which often goes along with blocked, highly amplified jetstream patterns.

 

As mentioned by Tamara in the MOD thread, the GWO is currently trending toward phase 2 and 3, which indicate that zonal westerly winds are less likely in that period. Therefore, a trend to more blocking is plausible, given this forecast. The GFS agrees with this forecast, as can be seen in the phase diagram below:

 

GWO trend over the past few days and GFS forecast (green colour), as of 16-12-2014.

 

What can be seen is that, after about 20 December, the GWO starts to become active, cycling toward phase 2 and 3.

 

A more in-depth explanation of the GWO can be found in the link below:

 

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

 

MJO

 

The MJO (Madden-Julian oscillation) is, in short, a measure for the amount and distribution of convection anomalies near the equator. The placement of these anomalies over the equator tells us something about the weather which occurs, or is likely to occur in the future, in the midlatitudes as a result. A more extensive explanation can be found in the link below:

 

http://www-das.uwyo.edu/~geerts/cwx/notes/chap12/mjo.html

 

Currently, the MJO is not active at all, giving little aid to the predictability of the weather over the midlatitudes. However, in a week or so, the MJO is forecast to enter phase 3, as suggested by the GFS ensembles:

 

MJO trend over the past few days and MJO forecast (green lines) as given by various GFS ensemble members, as of 16-12-2014.

 

The MJO 'travels', like the GWO, counterclockwise around the diagram given above. Currently, there seems reasonable certainty that the MJO will enter phase 3, but there remains a lot amount of uncertainty as whether and how fast the MJO will continue toward phase 4, or whether it will weaken back to a state in which the convective anomaly patterns over the equator caused by the MJO are negligible. The Climate Prediction Center states this, in their discussion, as follows:

 

 

Looking ahead, the majority of the dynamical model RMM forecasts of the MJO indicate a weak signal during the upcoming week before some potential strengthening of the signal in generally Phase 3 during the Week-2 period. Agreement is good for this evolution, although some models propagate this signal toward the MC more quickly than others thereafter. Longer term forecast models of the RMM index, show a continuation of eastward propagation once again to the western Pacific by early-to-mid January.

 

If the MJO would trend into phase 3, the following 500 hPa anomalies would be observed:

 

500 hPa anomalies caused by a MJO signal of greater than 1 (out of the inner circle as given in the phase space diagram). This is phase 3.

 

Note that these anomalies are no guarantee that the pattern will look exactly like that; they are only a general guide. Furthermore, these charts indicate anomalies, no real 500 hPa heights. This means that positive anomalies may still be associated with a 500 hPa trough, with it being only weaker than it usually is.

 

What can be seen is that there is indeed some kind of a positive 500 hPa anomaly noted to the south of Greenland, which kind of coincides with the Greenland block which has been advertised by some models. However, there are also positive anomalies forecasted over Scandinavia, which do not seem to be very likely at the moment. This can be seen in the GFS ensemble 500 hPa anomalies anomalies forecasted for 26 December, which can be found in the link below.

 

http://www.wetterzentrale.de/pics/Rnaa2401.gif

 

All in all, it seems that a pattern change is plausible given the various model output, the negative GWO and the MJO becoming more dominant again. To what this will lead is still up to debate, though. It will be a good watch, that is for sure .

 

EDIT:

 

Hopefully this thread can spring back to life over winter as the main model output will no doubt begin gathering pace and pages day on day. Looking around this morning found a couple of interesting things.

 

First is the GWO data, although ESRL are not maintaining chart output, email sent and hope others do to, the raw data is still being delivered in the form of a text file, we can see from this the GWO phase space and also the general tendency.

 

For the GWO forecasts, there is a great link available which does show the trend and forecast of the GWO by the GFS. It can be found in the link below:

 

http://mikeventrice.weebly.com/misc-oscillations.html

 

There is much more to find on this link in terms of MJO, GWO, waves etc., hope it helps!

 

Sources:

http://www.americanwx.com/raleighwx/MJO/MJO.html (MJO anomaly composites)

http://www.esrl.noaa.gov/psd/map/clim/test_maproom.html (GWO circle explanation, also showing more in-depth mountain torque events associated with the GWO)

http://www.esrl.noaa.gov/psd/psd1/review/Chap04/sec3.html (Explanation of GWO)

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml (GFS MJO forecast)

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ghazards/ (Tropical convection and MJO uncertainty analysis)

http://www.wetterzentrale.de/topkarten/fsenseur.html (GFS ensemble forecast of Europe)

http://mikeventrice.weebly.com/misc-oscillations.html (Various oscillations and their current strengts)

Edited December 16, 2014 by Vorticity0123

[johnholmes]

my comments on the current probability of any marked change in the pattern in the upper air pre, over and post Christmas

 

To answer the post mushy made this morning.

This is the link to the chart he quoted

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

this what I suggested the 6-10 showed last evening post 605 p31, quoting the bit needed

… Noaa

6-10 and the anticipated pattern change in the main  wavelength looks to be getting under way; trough nw pacific/w of Alaska and ridge Alaska along with reasonable sized +ve anomaly, the Canadian trough is now way west of the predicted position 3 days or so ago (then s Greenland, now suggested to be towards gr lakes, ridge now shown as off ssw Greenland and largish +ve anomaly with it thus the flow into the uk is still w’ly over the uk but as trough-ridge and associated +ve with ridge edge east so the flow will turn n of west into the uk, also the flat trough e of the uk is likely to react to thses changes by extending south/sharpening into Europe. Not even looked at the 8-14 but that is what is needed to be seen there if the colder shot is to be more than a short spell?

 

Going back to the EC-GFS and only the gfs actually shows this idea in its time frame (6-10). Again if my previous comment is to occur then by 2 days from tomorrow they should both be showing this prediction.

So a colder shot for sure 6 days or so from now, after the colder shot in the run ip to Christmas perhaps or will it merge into one-we have to wait and see?

This is what I felt after spending time this afternoon looking at the morning output from EC-GFS link below

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

 

Fri 19dec

Ec-gfs

Well no definite charts shown for any deep cold really; detail below

Ec suggests far west over pacific and trough/centre is deepened, flow east over states lok about the same and over atlantic; close in the uk and the trough is now suggested west (part of it) the uk giving a s of west flow then over uk and east the same flat trough type flow of a w’ly=no deep cold showing

Gfs has a link between the two ridges over n America (ec does not) otherwise fairly similar and again differs from ec re trough uk area, this time w of the uk into the lower trough thus flow into uk is s of west=again no deep cold being suggested 6-10 day time frame.

So which is closer to 6-10 noaa?

Ec shows marked ridge sw greenalnd into e n America  more similar to noaa, but not sure of either east of this

Overall this morning the threat of deep cold is no nearer, that is a cold north of west flow into the uk on the forward side of the upper ridge.

Will it show again, perhaps more so, this evening on the noaa 8-14 version?

 

I hope this makes sense to anyone who has read this post. If not please pm me to prevent the thread getting clogged up with the new 12z in mid run already?

Thanks

Edited December 19, 2014 by johnholmes

[lorenzo]

Sorry Vorticity, been busy with current charts to come back on this.

 

Stewart ( previous contributor to this site) is probably the best in class for GWO parameters and the influence of the mode on modelling, following from Weickmann and Berry, Ed Berry released a blog through 2006-2012 which explored the GDSM or GWO or GLAAM or what is commonly referred to as the GWO Global Wind Oscillation.

 

It is one of those modes where, you had to be there, to learn it and see it evolve, not so much the weather, in this case the understanding, right now the GWo remains a 'jedi' understanding. I do not mean that negatively.

 

For modelling, the imprints are imprecise it really is a 'feel' thing, and as such is not a black and white tool for predictability, the MJO follows the GWO in phase space, so we have some lead for the classic phase space MJO  with GWO. 

 

To be honest having seen this for the first time on netweather, it has remained a puzzle since, I think it is science and weather as art. Pushing solidly on the dynamics that underpin our physical modelling. Nevertheless, I also think that from taking a small half a degree variance in SSts some 50 years ago MJO and evolving to GSDM is amazing work. The GWO is a vital tool, not immediate range, not a silver bullet , but still genius. 

 

I hope the ESRL PSD maintain the work, I have enjoyed working up the phase spaces into analogs and still the daily GWO data is available on ESRL.

 

Where we get our Nina GWO disconnect from this season, cannot answer that yet, where would weather be without puzzles...!

Here are the Jan analogs

 

 

[Vorticity0123]

It is one of those modes where, you had to be there, to learn it and see it evolve, not so much the weather, in this case the understanding, right now the GWo remains a 'jedi' understanding. I do not mean that negatively.

 

For modelling, the imprints are imprecise it really is a 'feel' thing, and as such is not a black and white tool for predictability, the MJO follows the GWO in phase space, so we have some lead for the classic phase space MJO  with GWO. 

 

To be honest having seen this for the first time on netweather, it has remained a puzzle since, I think it is science and weather as art. Pushing solidly on the dynamics that underpin our physical modelling. Nevertheless, I also think that from taking a small half a degree variance in SSts some 50 years ago MJO and evolving to GSDM is amazing work. The GWO is a vital tool, not immediate range, not a silver bullet , but still genius. 

 

Hi Lorenzo, thanks for the reply.

 

It seems I was thinking too narrow on the GWO, there is much more to the GWO than I realized at the time of creating the post above. My understanding of the physics on the GWO is only very small, imagining what transport of angular momentum 'looks like' is already a challenge. A challenge that is not easily solvable, it seems.

 

Going back to the basic principles of physics, the first thing that I have realized is that angular momentum is a measure of rotation in the atmosphere, analogous to vorticity (coincidently my profile name ). So, in simple terms, angular momentum (vorticity) indicates the 'tendency' of a particle to rotate. Physically, the definition is the gradient of the velocity of the air (wind speed). Yet, upon knowing this, it is hard to be able to 'visualize' this in terms of high- and low pressure areas, let alone what the effect is of increased/decreased angular velocity transport poleward or equatorward.

 

Another thing I probably overlook was the assumption that the GWO phase space diagram (given in my post above) indicates angular velocity values at the midlatitudes. What the definition is, is uncertain to me.

 

Concluding, I do agree that the GWO remains something of a puzzle (a very complicated one), which is very difficult to understand physically. Probably experience is a good tool to get an indication of what it all indicates, rather than try to get a full fundamental understanding.

 

Sources:

http://journals.ametsoc.org/doi/abs/10.1175/2008MWR2686.1

http://www.theweatherprediction.com/charts/500/basics/

http://www.wetter3.de/animation.html

http://en.wikipedia.org/wiki/Madden%E2%80%93Julian_oscillation

Edited December 24, 2014 by Vorticity0123

[lorenzo]

Will come back on this soon !

[Man With Beard]

A question - what is the difference in impact on the NAO between MJO phase 6 and phase 7?

[Vorticity0123]

A question - what is the difference in impact on the NAO between MJO phase 6 and phase 7?

 

Before we start: I am by no means an expert on this subject, but I'll try to do my best to provide a as clear as possible explanation .

 

The first thing that has to be stressed is that the NAO (North Atlantic Oscillation) is merely a result of pressure distributions. In other words, the NAO is no controlling factor when it comes to weather. This is important to keep in mind.

 

Link MJO and ENSO

 

Regarding your question: currently it is a tough one to answer. This has all to do with the fact that the effect the MJO has on the weather in the extratropics is influenced by the ENSO-state (in short, this is what contains El Nino and La Nina). We are currently experiencing El Niño conditions at sea (at least judging from the Nino 3.4 SST anomalies; elaboration can be found here). Although the SSTS (sea surface temperatures) in ENSO-region 3.4 are currently El Nino-like (positive anomaly of higher than 0.5*C), the positive anomaly has not been observed in enough months in a row to declare an El Nino event to be born (although this is more a matter of definition; it should happen for at least 7 to 9 months in a row according to Wikipedia).

 

However, in the atmosphere a La Nina atmospheric pattern is being observed. (La Nina is more or less the counteractor of El Nino). In other words, there seems to be a significant disconnection between the ENSO-state of the atmosphere and the ocean. This was alluded to by Tamara in the model output discussion thread. Quoting a small piece:

 

 

 

As suggested in previous posts, re-initiated Nina imprint to the atmosphere has beefed up sub tropical ridges - and a strong Azores High features in the near and mid term, forcing a dynamic pressure gradient differential between the High pressure to the south and the zonally active jet stream just to the north of Scotland.

This pattern now fully advertised in modelling with the deep lows which threaten Northern areas most especially later this week

 

The full post can be found here.

 

 

The reason for the explanation on El Nino is that the influence of the MJO on the weather at the midlatitudes (including the NAO) is dependent on whether we are in an El Niño event or a La Nina event. The link is very complex in nature, but the imprint on the weather at our latitude is readily visible in analogues (which will be shown later).

 

Further reading for the link between MJO and ENSO (which is basically the overarching signal for El Nino and La Nina events) can be found below:

 

http://www.google.nl/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&ved=0CGwQFjAI&url=http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F225607704_ENSO_regulation_of_MJO_teleconnection%2Flinks%2F02e7e528d98ed7b4ce000000.pdf&ei=V0SuVOXUHMvBPOqYgLgG&usg=AFQjCNFhdKNvtV3uAn8LDVwCfq4S0XZx7Q&bvm=bv.83134100,d.ZWU&cad=rja

 

http://journals.ametsoc.org/doi/abs/10.1175/JCLI4003.1

 

http://onlinelibrary.wiley.com/doi/10.1029/2007JD009230/abstract

 

MJO analogues

 

Going back to the MJO analogues, below are the MJO analogues (assuming amplitude of greater than 1, so that only the significant MJO events are being taken into account) for an El Nino event for phase 6 and 7 in January:

 

 

 

Phase 6

 

Phase 7

 

And now for the non-El Nino years:

 

Phase 6

 

Phase 7

 

All these plots show 500 hPa height anomalies for January (they therefore do not show actual heights, which has to be kept in mind when interpreting these charts).

 

Impact of different phases of MJO on NAO

 

From the MJO plots (El Nino as well as non-El Nino years) it can be seen that there is a significant negative anomaly in heights (generally meaning lower pressure) near Iceland, while higher than average pressure exists near the Azores. If one recalls the definition of the NAO, it is the difference in pressure between the Icelandic low and the Azores high (by approximation). A positive phase of the NAO indicates that the difference in pressure between the Icelandic low and the Azores high is larger (i.e. lower than average pressure near Iceland and higher pressure than average near the Azores). This is what is being experienced in phase 6, meaning that the MJO in phase 6 is more likely to coincide with a positive NAO.

 

On the other hand, the situation becomes much less clear when the MJO enters phase 7. The low pressure anomalies have shifted inland over Europe, while there also seems to be a tendency for above-average heights over the western Atlantic. The Icelandic low seems to be somewhat less strong than average, and the Azores high is less dominant. Therefore, an MJO-event of phase 7 will most likely coincide with a neutral or negative NAO.

 

Impact of ENSO on MJO effects on NAO

 

The first thing that comes to view when comparing the different phases of the MJO (phase 6 and 7 during January) during El Nino years and non-El Nino years is that the anomalies which are caused by phase 6 and 7 of the MJO are much more defined during an El Nino event.

 

More importantly, as noted before, the atmosphere does not seem to 'behave' like an El Nino event. Therefore, it seems that the El Nino analogue years do not seem to be very representative for the influence of the MJO on the weather near Europe at the moment. It is perhaps more safe to apply the non El-Nino containing MJO analogues for the time being.

 

Conclusion

 

In short, judging from MJO composites in January, phase 6 is usually accompanied by a positive NAO, while phase 7 often coincides with a neutral or negative NAO. It has to be emphasized, though, that there is monthly variability in the strength and position of the anomalies caused by the cycle of the MJO. In other words, the pressure anomalies caused by the MJO of phase 6 in March are likely somewhat different from these anomalies of phase 6 experienced in January.

 

I hope this answers your question sufficiently . If you have any further questions, do not hesitate to ask!

 

Sources:

http://www.americanwx.com/raleighwx/MJO/MJO.html

http://www.ncdc.noaa.gov/teleconnections/enso/indicators/sst.php

http://en.wikipedia.org/wiki/North_Atlantic_oscillation

http://en.wikipedia.org/wiki/El_Ni%C3%B1o

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

http://onlinelibrary.wiley.com/doi/10.1029/2007JD009230/abstract

Edited January 8, 2015 by Vorticity0123

[Pennine Ten Foot Drifts]

Wasn't sure where to stick this, so mods feel free to move if there's a better place for it.

 

Not often I get something at work which is actually interesting, but I thought this one was worth a read:

 

http://www.cio.com/article/2878431/supercomputers/noaas-next-supercomputer-will-be-a-cray-ibm-hybrid-system.html#tk.rss_all

[Interitus]

Moved to more appropriate thread

Edited February 22, 2015 by Interitus

[BLAST FROM THE PAST]

Well an interesting blip coming up, I think the more potent idea for weekend like GFS shows could be on the money.  Also I've noticed, despite current warmth, that Spring in bloom is delayed.  Warmth to return next week but beware a cold return late April.  In some camps this year is the next down step in potential cooling period so I expect an interesting synoptic year ahead

 

BFTP

[cyclonic happiness]

Well an interesting blip coming up, I think the more potent idea for weekend like GFS shows could be on the money.  Also I've noticed, despite current warmth, that Spring in bloom is delayed.  Warmth to return next week but beware a cold return late April.  In some camps this year is the next down step in potential cooling period so I expect an interesting synoptic year ahead

 

BFTP

I never trust warm Aprils! they always seem to lead to crap summers 

[BLAST FROM THE PAST]

Looking good for the cold return I warned of...could be pretty darn chilly!!

 

 

BFTP

[David Morse]

East or West based NAO: what effect does El Nino have on its position.

 

With today's BBC report about temperature trends over the next two years (http://www.bbc.com/news/science-environment-34226178) I've been looking at seasonal prospects for Alpine Snow in the winter ahead (as I'll be returning to Avoriaz in March). According to several sources I've read; in recent history there has been a steady fall in winter snow depth over the western Alps: rising global temps have been pointed to as the main reason. The BBC news article mentions that the UK MO thinks the next two years will be the warmest on record, but with the cooling trend in the North Atlantic our summers may remain cool for some years. This though, as I've read, is against a background of a "low fequency multidecadal" cycle of snowfall which signal is sometimes "leveraged" or "dampened" by other oscillations like El Nino.

 

I know something like snow depths in any region is very difficult to forecast at any time; so I was more interested in what were the general potentials. I was interested to find out if under the current conditions of a developing and potentially (and forecast) strong El Nino what effect that would have on snowfall levels on the western Alps.

 

I've scanned through several academic papers looking at historic snow depths in the French Alps and also years with bad avalanches and compared those years with years of a strong El Nino; now there was not a great correlation anywhere. But as I read on and looked for more articles I did find several which showed a good correlation between years of strongly negative NOA and high snowfall depths in the French Alps.

 

There was a good correlation between these.

 

I did; however, see that although a winter with a strongly negative NAO gives cooler than usual temps in western Europe along with high snowfalls over the alps, the East/West placement of the NAO anomaly is crucial as there seems to be (particularly for the US east coast) considerable difference.

 

A good example was given: winters 1963 versus 1966

 

Both had strong -NAOs 1963 was a record breaking year for cold in the UK, but snowfall over the French Alps was higher in 1966 with a -NAO which was west based as opposed to the east based 1963 -NAO.

 

So the question I had was what effect do you think a strong El Nino would have on the location of the geopotential anomoly for a negative NAO this winter?

Edited September 14, 2015 by David Morse