Worthy copying and pasting this from the MO thread just for the record;
Morning all, just a quick one...
The latest update of the EC 32 day is essentially a continuation of the last few updates and without question it continues to highlight a significant pattern change into early February and beyond. In all its glory high pressure becomes dominant to the N or NW of the UK as a -ve pressure anom becomes established across Central and Southern areas of Europe and this then allows the overal mean flow to become E or NE'ly across the UK and other Northern areas of Europe into the opening week or more of February. Clearly the temperatures drop below average by at least 2C or 3C at times and precipitation generally becomes lower than average.
So as I said last week, either the EC 32 is going to fail miserably, change at what is now becoming an increasingly last minute situation or we are going to see a very interesting final month to winter. We haven't got long until February so we must be approaching the time now that the Deterministic and Ensemble models from the various sources begin to signal this pattern change. This is what clearly needs to be looked for now without question and that is height rises to the N or NW of the UK and either marked trough to the E or SE of the UK and perhaps even a cut-off low type scenario over France or Iberia.
It's all to play and time will tell as ever...
TY for that good news Matt
Tha possible situatio for a cut-off over Iberia it would be the cherry on the top of the cake
From some way out the cusp period of end of January and the start of February has seemed the most likely time for this noticeable pattern change to show its hand. We still don't know exactly how things are going to change for the BI, or to what extent, but what it has already shown is that the stratosphere/troposphere interaction is a very prominent one in determining cold or mild weather potential.
Without the recent and ongoing large scale changes in the stratosphere we may as well have been praying for longer days and Spring as the only way to get out of interminable atlantic westerlies and frequent dark, wet and windy days
What we can be fairly confident about is that the stratosphere is very unlikely now to return to the state it has been, this side of the summer, and a final warming will surely be much earlier than last year
I assume at the other times they are 5 or 6c below average? Otherwise, not much more than may be expected from a chilly northwesterly or anticyclone over the UK and not a proper cold spell
Edited by user 20 January 2012 13:25:07(UTC) | Reason: Not specified
The rise and fall of the warming at 30hpa level in response to the higher level, as it come via pulses of wave breaking, is what is assisting the warm anomalies downwelling to the surface and translating to the break up of the polar vortex at the surface. Although we may at this stage have fallen an nnth short of a technical SSW what we are seeing nevertheless is sustained moderate to significant warming with the likelihod of a further warming peak to come in the near future as well. A case of watching the forecasts for that though
Arguably, for longer term cold outbreaks rather than some one off like Feb 2009, this type of warming evolution holds better potential - with chances for a cold spell increased in the UK because if one attempt falls just short, there is a better chance that another attempt will come around afterwards. Plus that in turn stands an even higher chance of succeeding because of the sustained attack on the vortex and not allowing it chance to regroup
Edited by user 20 January 2012 16:46:13(UTC) | Reason: Not specified
Irrespective of short term question marks and differences being resolved by the models, the outlook from the stratosphere continues to show sustained warming and wave breaking with latest Mountain Torque event probably due to produce yet another warming spike to maintain a disturbed vortex and repel any attempts by it to reform through February and beyond.
I think the UK will be very unlucky indeed not to see an end product in terms of cold at some time
I noted in another thread that some were a bit bamboozled by the terminology used in here - that goes for me too. I think I may have understood and use the chart below as an illustration. If I'm standing on the ground at 1000hPa, I'm looking up through the atmosphere to the top of the stratosphere at 0hPa. The chart shows the fluctuations of temperature at different heights above me. Somebody plese correct if I've got it wrong.
Edited by user 21 January 2012 10:42:13(UTC) | Reason: Not specified
Spot on!
That's certainly my understanding of that chart. One clarification - it shows temperature anomalies not 'fluctuations', i.e. it shows warmer and colder points in the atmospheric 'column' between 60 and 90 degrees north.
Sometimes there is a simple explanation for this. And in this case that is so. The warm stratospheric air is deflected away from the North Pole - south of 60N - by the shape of the vortex, before re-entering a day or so later to latitudes further north (E-P flux important here)
http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ec.php?alert=1&level=30&forecast=all&lng=eng
Rest assured the stratosphere is driving NH events here.
Interesting tweet fro Matt Hugo a short time ago
Compare & contrast - Very important signs from the ECM in particular regarding the Polar Vortex into early Feb..
https://p.twimg.com/AjxOHM3CIAEirDy.jpg
https://twitter.com/#!/MattHugo81/status/161089572292403201/photo/1
Ignore the 18z GFS at least everything in the stratosphere is looking good
Ironically the GFS stratospheric outlook is looking especially good, unlike its mood swinging tropospheric sibling
That's a pretty good description of it, I must say.
The sustained process of destroying the polar votex continues to grow with every passing day. Looking to the ECM forcast now for yet another spike in temperatures. GFS stratosphere forecasts already indicating this, courtesy of the latest MT I have been speaking about
Meanwhile the next pulse of warming anomalies are making their way to the troposphere - and they underpin further the prospects for February with a new entrenched -AO/NAO pattern and strongly question any suggestion of attempts to return to zonality. Of all the options available as far as the UK is concerned, this is the least likely to occur. So easterly, then north/north easterly as blocking retrogresses to the NW?
The refreshed and newly updated ECM 32 dayer which has stayed consistent for several roll-outs now, looks very good value for money
Edited by user 24 January 2012 12:26:45(UTC) | Reason: Not specified
Indeed
I think the problem is that we know that the NAO can be a law unto itself, behaving in a set patterned away and not responding to other drivers in the way that it might.
We have seen this before, notably in winters earlier this century and that is again looking where we are headed for February in spite of everything else.
Edited by user 26 January 2012 09:33:34(UTC) | Reason: Not specified
The NAO can operate in disconnect to the AO, at least for a time, but as far as winter is concerned seasonal wavelengths dictate that this usually happens early in the season - late November and December. However during the second half of the winter there is an increased coupling of the two during January and most especially February.
However the key part of this is that the relationship cannot operate indefinitely de-coupled. Despite the gyrations and contrary signals coming from the models atm, that are leading people to believe what they are saying at face value, nothing has changed in terms of the outlook in terms of February for an entrenched -AO pattern in direct contrast to first half of the winter.
On that basis any suggestions by the models to over strengthen the northern arm of the jet should be taken (imo) with a pinch of salt. Especially kee jerk reactions to the ebbs and flows of daily model forecasts. It seems wiser to take an overview imo over a couple of days or so to get a wider picture.
The present complication in terms of jet energy to the north is a residual parcel of vortex close to the North Pole and the modelling of this has been chopping and changing for some time. But when seen in the context of the overall pattern and expectations of stratospheric forecasts this is not a long term situation with further downwelling of warmer layers expected through the first week of Feb that should further change, and improve the polar profile. I'm not sure that the models have read this signal yet properly.
Irrespective of what happens next week, easterly or not - that is why I am taking model projections into the new month with a pinch of salt.
Edit: chionomaniac on NW has given a much more technical answer to the overall situation than I ever could in my own simple lay language - but the gist is more or less the same in terms of the prognosis for February. As he states in terms of the vortex - longer term changes should be expected in the context of the present messy and uncertain situation
Edited by user 26 January 2012 12:00:34(UTC) | Reason: Not specified
Tamara, I would certainly agree with what is being said in principle, but what should happen and what actually happend may be two different things for whatever reason.
Not seen GP posting over on NW, I take that to mean he has no confidence in the cold evolution.