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Good Blocking for Jan 2014
Meanwhile.....
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that chart is 2009 the one I was showing was 2010
here is the SST anomalies for the closest to todays date as I can find for the past few years 2008 onwards to this year for comparison on how we stand just now
anomnight_10_30_2008.gifanomnight_11_2_2009.gifanomnight_11_1_2010.gifanomnight_10_31_2011.gifanomnight_11_1_2012.gifanomnight_10_31_2013.gifGood point, sorry, brain meltdown. I could get away with it though.....mid-December 2009 was "before the cold set in" in 2010
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EC32 tries to suggest a somewhat more NW flow for the last week of November, but not a strong signal. Prior to that, +ve heights nearby or to our south.
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for those who maybe don't know what a classic TRIPOLE is heres a chart and note the atlantic
W = warm
C = cold
TRIPOLE = warm then cold then warm ( warm south of Greenland, cold mid atlantic and warm tropical atlantic)
here is a link to the SST anomalies
http://www.ospo.noaa.gov/Products/ocean/sst/anomaly/index.html
Here is the pattern just before the cold set in that month:
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I did a fairly detailed post on this last year, which you might find of use http://forum.netweather.tv/topic/74491-winter-2012-2013-part-2/?p=2373163
Seemed the strength, rather than phase, is what matters most.
That was very interesting, thanks.
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What is that mean?
That type of pattern was identified as a key driver in the 2010 winter. There are some similarities with the current pattern, but also some differences. Nothing ever quite fits the conceptual model perfectly.
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I don't think the temperature values are of much use, I only really posted them for interest's sake. Temperature forecasts are much tougher in general than getting the broad pattern I find.
Does that paper mention why they only tried correlation from 1997? Seems there's plenty more data than that.
Just a very quick example....correlating MEI against 1000mb temperature does not detect any strong relationships in our part of the world.
Similar story for 500hPa heights:
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No regrettably not,he has gone to a large professional Weather company. I feel any criticism of him to be totally unfounded as he did meet with great success and developed a huge following,we are less knowledgeable due to his departure. Chio is doing his best to fill the void and doing a good job but as I said he is certainly a big miss.
Do we have any idea who he works for? I know he said "multinational". Why is it a secret? Is this the same Stewart Rampling? (http://www.countrysideconsultants.co.uk/profile.htm)
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I'm determined to try and get a better handle on pacific teleconnections this year... so I have to ask this dumb question. Alaskan high and Aleutian low. OK - but to my very untrained eye the aleutians sit directly south of Alaska. How can the aleutian trough be downstream of an alaskan high? Does an aleutian low not actually pump up an alaskan high as per next week?
I think "Aleutian High" typically refers to a pressure pattern in the stratosphere.
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to add to what CREWECOLD was saying about CFS heres the 12z winter charts
sea level pressure anomalies
cfsnh-4-12-2013.pngcfsnh-4-1-2014.pngcfsnh-4-2-2014.pngcfsnh-4-3-2014.pngtemp anomalies
cfsnh-8-12-2013.pngcfsnh-8-1-2014.pngcfsnh-8-2-2014.pngcfsnh-8-3-2014.pngtemp anomalies don't look as cold as the charts do I would think the temps would be a little lower
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It seems plausible. But "locals" all over the world will always claim that their spot is somehow significantly warmer or significantly colder, or significantly different in any other way, to the "official" records. These claims are often exaggerated but sometimes contain grains of truth.
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This is an astonishing image to see on the CFS because it's off the 10 day averaged run. Would not be surprised to see this on an individual run, but these massive anomalies on the 10 day are amazing.
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I am usually defensive of the EC32, but the run from 3rd October valid for next week did predict higher than normal pressure just south of Greenland (extending N), with a weak signal for lower than normal pressure to our NE. I don't think that will verify too well.
As it currently predicts a continually unsettled spell though, you would expect periods like that are closer to climate norm and easier to predict.
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I'm not sure if they would be. The azores high would still affect us and the Atlantic weather would still affect us.
I suspect that is the case. Subtropical highs like living off the west edge of continents (i.e. Europe for the Azores High). If the Gulf Stream "shut down", perhaps we would end up with a weaker but similar current, forced by persistent winds around the Azores High. SST's would be lower, so perhaps we would have similar weather patterns but cooler resulting temperatures.
Lots of "perhaps" there!
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Looks, to me, as though we were all taken-in??
Interestingly, it was close to the time of Tropical Cyclone EVAN in the SW Pacific. The models for some time had difficulty getting a grip on that feature - it seems plausible that this could have been a distant source of error for the flow in the NH.
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Decided to have a look at this famous failed easterly from last year. This and the pages following:
http://forum.netweather.tv/topic/75166-model-output-discussion-12z-04122012/page-26
Not an experience many people want to revisit I imagine!
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What was the GLOSEA model showing this time last year?
See attached. This winter uses a newer version of the model though.
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The met office ensemble mean has finally updated and we have a signal for lowish pressure to dominate Greenland this winter and high pressure dominating to our west / south west as well as drifting over to the UK it would keep the Atlantic very quiet during winter, the high to our NE is further east compared to the September update
Rainfall looks slightly below average
We are only awaiting on jamstec to update now for October
Just out of interest, I have attached the Met Office forecast for winter 2010/2011 and for winter 2011/2012 issued in the corresponding Octobers. The model has apparently improved since then. I think it's version 5 now.
As you can see, for both these winters it picked the general pattern nicely.
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Very many thanks for the wonderful explanation both! It seems to be not as easy as I thought it was, but this greatly improves my understanding of these phenomena! I'm really in your debt now.
Are there also charts available of the compositions of the individual waves?
What I really like about this forum, and especially your replies to my question, is that you have the quality and patience to make meteorology highly understandable for the lesser of us, even during difficult subjects. Once again, many thanks.
Thanks, I just hope I haven't made any mistakes!
I am yet to find anywhere freely available online which breaks down the compositions of the waves. An exception is the FU Berlin stratospheric page which shows you the Wave 1 and 2 amplitudes. I think the NCEP stratosphere site gives you Wave 3 also. Beyond that, I'm yet to find anything.
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1) So if I am correct, the ridge/trough system on the midlatitudes is essentially a superposition (mixture) of different numbers of waves. Likewise, on this GFS chart:
2) for example, looking at about 60S, you see a number of (more or less pronounced) ridges and throughs (2 waves near southern Brazil). Are those the result superposition of several waves?
1) Pretty much. And fourier analysis allows you to get an idea of what the composition is.
2) I always find it really difficult trying to manually visualise for a given chart what the component waves might be. It might not be possible at all....however, you can think of it in a simple way just using two different waves:Imagine in your latitude belt you have just two waves. One of them is Wave 2 and the other is Wave 7. So very distinct waves. Wave 2 is perhaps stationary, very persistent whereas Wave 7 moves in the westerly flow, and by itself would just look like a standard mid-latitude zonal pattern with lows and highs.
Where the Wave 2 ridge and Wave 7 ridge are in phase, there would be "constructive interference" (from standard wave theory). The resulting ridge would therefore be more intense than under other circumstances. Likewise, where the troughs are in phase, you would probably see a deep low. In areas where the phases don't match up, you would see destructive interference. So for example, a Wave 7 ridge beneath a Wave 2 trough would perhaps result in a fairly weak area of high pressure. And a Wave 7 trough + Wave 2 ridge would probably see the resulting low pressure system not being deep or not forming a closed low at all.
Apparently, in the past it used to be possible for forecasters to improve on NWP by being aware of the long wave patterns in the short term. If you know that you're under a Long Wave ridge, then you would naturally expect resulting medium wave (troughs) and shortwave (troughs) moving into your area to weaken somewhat. I suspect these days this isn't really possible in the short term (due to sophistication of modern NWP), though would be an interesting experiment. In the long term it may be a different matter, and is somewhat akin to how John Holmes approaches long range forecasts using the 500hPa anomaly charts.
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Height fields at a given surface are superpositions of many different waves on top of each other. You can pick out the individual waves by doing something called fourier analysis, which has applications in many different fields.
Once you do that you will end up with an idea of the different contributions from waves 1, 2, 3 etc. all the way up to about 9. What does this mean?
The numbers are the "wavenumber". This means that in a given belt of latitude, a wave with wavenumber 1 will have one peak and one trough around the entire world. This is called wave 1. Likewise, a wave with wavenumber 2 ("Wave 2") has two peaks and two troughs as you go around the globe within this latitude belt. And so on. As you can probably see, as you increase the wavenumber, you are cramming more waves in as you go around the world. So the distance between each peak and each trough gets less. This is another way of expressing the relationship between wavenumber and wavelength. Wavenumber is essentially the inverse of wavelength.
Long waves are usually referred to as those with wave 4 or below (aka Rossby waves or planetary waves). It is possible for these to be stationary, even in a mean westerly flow. With wavenumber 5 and above, you get into "synoptic waves" and these usually move with the mean flow (i.e. for us usually towards the east).
The paper you referenced has the same idea (in terms of wave theory, wavenumber is a consistent concept), but is talking about Kelvin Waves. These occur in the atmosphere and the ocean - probably best known in the tropical atmosphere as an eastwards moving wave of about 40 knots. Usually when meteorologists talk about wavenumber they are talking about Rossby waves.
Your question is definitely worth asking because I suspect that around the internet some people throw these terms around without getting a real physical understanding of the terms they're hurling around.
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November 2004 to January 2005 was terrible for the south. Winter 2004/05 was saved from being a stinker by February. Just a great shame that Europe had been so mild meaning that the prolonged cold spell failed to deliver as much as it could have done. Winter 2005/06 may have been the coldest since 1996/97 but for the south it was dry with little in the way of snow.
It snowed on Boxing Day 2004 in South Wales
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White means climatology, i.e. no signal at all. What use is that? Any forecast of any worth must be at least as good as the climatology skillwise when verified to what actually happens.
I don't think a "no signal" forecast is as useless as you're claiming, and it happens frequently enough in all the models. e.g. the CFS shown below. Even the best models have huge areas of the globe covered with "no signal". It might mean that there truly is no signal (intrinsic), or it could mean the model is not good (practical). Hard to know in individual cases. I think what we hope, is that when a model does go for a signal, that it comes off well. The majority of seasons come in close to seasonal average, so for a model to predict "no signal" more often than not might be a sign that it is well calibrated.
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Model Output Discussion 1st Nov.2013
in Forecast Model Discussion
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I don't agree. Comparing the deterministic with the ensemble mean should be part of the approach.
See the (not-unquestionable) Bible here: http://www.ecmwf.int/products/forecasts/guide/user_guide.pdf