chionomaniac

That is a projection on this winters proposed H5 anomalies based on the current SST pattern and is very similar to last month's projection. Interestingly the increased heights in the Bering sea region and weak Greenland to Scandi increases fit in very nicely with similar analog years. Has anyone got the link to the web page that this projection comes from ( not Joe B's) Thanks in advance.

Looking at the charts between T+120 and T+144 which was yesterdays T+144 - T+168 that Steve was highlighting we see neither a true retrogressing high - but neither do we see a sinker as you suggest. Rather we see the halfway house solution where heights start to build north of the Atlantic low before fading - but so does the Atlantic trough fade at that time frame. The anomaly charts that John posted show that the heights are likely to be strong in the Greenland region keeping the Atlantic trough detached from the main core of vorticity from T=144 onwards - so as SK says it is probably best to watch what happens from here on in.

The correlation is still probably there, SI - it just may have not been significant until the ice levels were at record low levels. Just because other factors have overridden the low sea ice values before it became significant, and these factors could still give the UK cold winters back then, doesn't nullify the correlation that is shown now, except perhaps in your eyes?

The thing is, is that we well never get to see the 00Z T+168 UKMO so we will never know. However the signs are there for SM's theoretical exercise. If you look on meteociel and run down the times you will see the Scandi block form at T+120. By T+144 the Euro trough has elongated and is slighly more NE positioned, the lobe of vorticity and lower heights that is the Atlantic trough become detached from the main PV segment - allowing heights to rise in between and the trough becomes negatively tilted - in itself this is a big clue as the energy crossing the Atlantic will rather split and go under the block rather than recurve and go over. The UKMO could well be wrong - but it has been leading the way and has done all last winter in these type of set ups. The ECM shows retrogression of the Ridge as well whilst it diminishes in strength.

The retrogression of the high has already begun between T+120 and T+144. But the negative tilt on the Atlantic trough alongside the reduction in vorticty further north tend to be a dead giveaway. It's a pity that we will never see the T+168 chart, as by this evening there are likely to be further changes to the modeling as no two runs at this timeframe are the same.

The NOAA show the 60ºN latitude (when they are working) Here is a chart borrowed from American Wx for the 1st OCT (and also 2002)

I see that you are starting your nonsense a bit earlier this year, Ian. As feb 1991 correctly points out the whole winter pattern was completely disrupted by the SSW in early Jan and the effect of this was enhanced by further wave 1 breaking events in March just when it looked like the vortex was recovering. The only thing that the strat experts can be guilty of is taking their eyes off the ball as the season drew to a close. If you look at the following anomaly chart it is quite easy to see how the underlying stratospheric conditions encouraged the trosposheric blocking that ensued - yes we still have a lot to learn - yet you say that the persistent low heights over Europe were the cause as if the earlier stratospheric polar blitzing that had occured had no influence at all. Yes we needed tropospheric conditions to be right but without stratospheric support March's cold outbreak would have been a complete non-starter. I too expect the vortex to power up later this Autumn possibly giving a very positive AO in November but this may be counteracted by a strong Atlantic ridge at that time.

Here is the cpc one, Steve, http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_UGRD_ANOM_ALL_NH_2013.gif and the ECM zonal wind forecasts http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/eczm.php?alert=1&forecast=all&var=u&lng=eng

It is worth pointing out how important a meridional flow is for those hoping for cold when looking at the models for this coming winter. We are seeing a classic switch forecast from high 850's (+12ºC) over Scotland tomorrow being replaced by low 850's by Thurs (-3ºC?) - a 15ºC switch around. This is very difficult to achieve in a zonal flow. Yes, we may be on the wrong side of the ridge in the outer reaches of the modelling in FI, but always be aware that these switcharounds do occur in meridional flows and that by the time that the exact ridge positioning becomes modelled more accurately by days 4/5, the ridge may be better postioned/ orientated bringing colder 850's over an area that this previously looked unlikely. I have learnt to always look for the meridional pattern first and disregard the positioning of the troughs/ ridges until the meridional pattern is established. Normally, when it is established over a period of time, the cold that floods to more southern latitudes will often hit the UK and when it does it can hang around. So that begs the question - when we are in an established zonal flow, what is necessary to change this to a more meridional flow? And the answer to this is not a straightforward one. It just doesn't occur without some type of driving mechanism. Yes, we need to look at the stratosphere - but if the stratosphere is already cold and a strong polar vortex established then we need to look back into the troposphere. In some years the stratosphere will be more receptive to tropospheric interactions than others ( more discussion for the strat thread) but we will still need a kick start from the troposphere to feedback into the stratosphere. The kick start often will come from the tropics in the form of pulses of convection interacting with slight undulations in the polar vortex which influence the positions of the sub tropical jet stream and polar jet streams respectively. The exact positioning of the large scale undulations ( or Rossby waves) will be influenced by (amongst other things) the pulses of tropical convection ( aka the phase of the MJO) and that is why we monitor that so closely. These waves will interact with land masses and mountain ranges which can absorb or deflect the Rossby waves disrupting the wave pattern further - and this interaction and feedback between the tropical and polar systems is the basis of how the Global Wind Oscillation influences the global patterns. The ENSO state can affect this - giving us the underling atmospheric base state . If the deflection of the Rossby Wave is great enough then the wave can be deflected into the stratosphere. This occurs a number of times during a typical winter and is more pronounced in the NH due to the greater land mass area. Most wave deflections into the stratosphere do change the stratospheric vortex flow pattern - this will be greater if the stratosphere is more receptive to these wave breaks ( and if they are substantial enough, then a SSW can occur). The change in the stratospheric flow pattern can then start to feedback into the troposphere - changing the zonal flow pattern into something with more undulations and perhaps ultimately to a very meridional flow pattern. It is looking like the loss of summer sea ice in the Arctic ( and corresponding increased autumnal snowfall further south) in recent years may be contributing to the pattern of the jet stream being less zonal - with more undulations due to the baronclinicity zone possibly being displaced further south - but there are other factors such as the SST's influencing whether the flow is more zonal. And these are all the things that we need to monitor in the coming weeks and during winter - especially if a zonal flow becomes established.

Will start a new thread in the next week or so for this years monitoring. But that is interesting. I have to say that there is a certain pattern that I am hoping to see this autumn and from this we may be able to project a winter stratospheric pattern. Edit - and thanks for Tony and feb1991blizzards kind words. It is good to see that most now realise how important that the strat pattern is in dictating the tropospheric patterns.

Looks like the first cell of the day has developed and is about to hit Bognor. Not thundery (yet).

Those new cells have really developed in the last 20 mins - looking like a measle rash about to hit the SW.

Interesting - it is one of those days with an enriched low level moisture feed in as well. We have the sun breaking through the low fast moving cloud from the SE. Reminds me of the LLJ in TX. I have a funny feeling that today will end up a cracker for some. Already new cells forming ahead of the main band.

Radar look impressive to our S already. And a few strikes thrown in the mix. Lovely dew points, Cape and warm uppers all in the pot as well. Could get interesting later..

My understanding is that positive mountain torques follow positive frictional torques adding energy to the tropical momentum budget and negative mountain torques follow negative frictional torques deflecting momentum northwards away from the tropics. The former is better for reducing west to east flow across more northern latitudes and a more meridional flow is more likely, as well as the posibility that the MT can be deflected into the stratosphere if it is strong enough.

The corrected anomaly chart is pretty amazing- next I think that I will add one to show the difference between the two Here it is - it doesn't look as impressive but that is only because the scale has changed!

Cheers - Grrr - correction on the way sorry - trying to do to many things at once!

Wonderful Paper as posted by Snowy L (thanks) in the winter thread. And when I get time there are many links to other papers in there that need to be researched. http://www.tellusa.net/index.php/tellusa/article/view/19375/html

Which is probably significant as seen in the posted anomaly charts as suggested above

Here they are: Low sea ice years Jan-March High Sea ice years Jan-March It is not so much the low sea ice years anomaly that is impressive here - but the increase in the polar vortex strength over Greenland over the high sea ice years. Now this may be for some other reason - but it has been reversed over the last few years that does coincide with the low sea ice years. Note that the anomaly from the high sea ice years from the Dec- Feb transfers from the Barents Sea and Kara Sea north of Siberia towards Greenland. Both areas are situated where we would want to sea blocking occur to favour cold in the UK. Still Interesting.

I think that this was addressed at the time and was found to have no measureable impact when looking at the whole Arctic stratosphere as a whole. If it were to have an impact it would have been noted as an increase in the stratospheric temps at the time - and there was no such increase recorded. I guess it's a bit like expecting a match being lit to have a measurable impact in the millenium Dome!

It is Full paper here : http://www.tos.org/oceanography/archive/26-4_cohen.pdf I think that I mentioned it a week or so back after Sebastiaan linked to it, thanks for the reminder.

The recent figures though are interesting. If we look at recent below average Arctic ice years and above average Arctic years and compare the H500 anomalies then the winter differences are quite drastic. Years here: http://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/ Low sea Ice anomaly High Sea Ice anomaly No correlation? Not so sure.

I may not expect it to verify - but there is always a pleasure to see a great synoptic looking chart at any time!

Blimey! do I see an omega block at the end of the ECM run. What a waste in September!