492
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Posts posted by 492
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The broad scale features may well support progression in the longer term but we still have to negotiate the trough which is expected to disrupt in the short and medium term close to or over the UK. Pressure falls are expected over the western Med which would help to support the high which is currently taking shape over and to the NW Scandiavia. Following the disruption and looking at some of the recent output I would have thought that a period of quieter, colder weather perhaps with a gentle NE'y flow at least in the SE in still on the cards and which may just hang on a little longer than is currently expected.
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The block that is expected to develop over N Scandinavia is not predicted to be in place until 2 days from now at the earliest. It is not until it is in place that we may start to know what its effects will be on the behaviour of the UK trough and the possible disruption that may occur. Current analysis shows a high of 1042 MB centred over Greenland with weak high cells futher east. The modelling has proven to be unreliable over the last week with some centres forecasting (the currently non existant) block to the NE to slip away SE. I think we need to closely watch developments over the next 48-72 hours to see what happens regarding the block. Also the presence of very cold surface air already in place over Scandinavia must have some impact on any blocking in the region.
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ECM and GFS both show a developing block to the NE from around T+96 . GFS still goes for trough disruption over the UK and continues this right up to 192. If the block develops as predicted by these models the trough disruption could easily be further east or further west. Lets first see if the block does indeed develop and take it from there.
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510 thicknesses reach mid atlantic (50N 31W) on UKMO 120 FAX with sub 528 air approacing uk.
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But it might be cold at the surface?
At the moment 850 temperatures are around +8C over Europe yet surface temps are widely sub zero with dewpoints as low as -10 C in places. So if this senario is repeated next week and with a SE feed it could indeed be cold perhaps very cold in the SE.
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1974, 1975, 1976 and 1977 were all mild winters at least in the south. It wasn't until the winter of 1978 that things turned dramatically colder.was it not the case that the Atlantic was in its cold phase? I do remember that in the 70's we did have a string of cold and snowy winters. I also remember certain science journals and media predicting a slow haul back to an ice age lol
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It was of course early February 2012 not 2011 when the Siberian anticyclone moved west to Scandinavia.http://www.uni-koeln...rcisoTTPPWW.gif
Analysis 20th March 2013 showing classic pattern with reversal of flow around the Pole with an easterly component from eastern Siberia to central Canada. Although this has been modelled for some time it is noteworthy that this is now a reality. It is almost as remarkable as early February 2011 when the Northern Siberian anticylone moved westwards to Scandiavia maintaining a central pressure of 1060 hpa and put Europe into a deep freeze.
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It was of course early February 2012 not 2011 when the Siberian anticyclone moved west.T0, that's impressive I have to admit. Stunning high pressure cell over the Pole
With that as a starting point and the weather pattern shaping up in our area of the world, it's actually not surprising that we have a good chance of tapping uppers of potentially up to -12 even at this time of year.
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http://www.uni-koeln.de/math-nat-fak/geomet/meteo/winfos/arcisoTTPPWW.gif
Analysis 20th March 2013 showing classic pattern with reversal of flow around the Pole with an easterly component from eastern Siberia to central Canada. Although this has been modelled for some time it is noteworthy that this is now a reality. It is almost as remarkable as early February 2011 when the Northern Siberian anticylone moved westwards to Scandiavia maintaining a central pressure of 1060 hpa and put Europe into a deep freeze.
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I cannot recall many March months with similar synoptics but March 1962 does comes to mind.Significant changes this evening from the UKMO and GFS towards the ECM evolution.
Its a very wintry outlook - a locked in cold pattern with heights to the north digging its heels in - this is turning into a notable lengthy cold period for the time of year especially in the north- the cold pool over Scandi remains very intense for the time of year. I don't believe many at the start of the month would have expected just how things are turning out this March. In terms of anomalous synoptics it is very reminscent of December 2010.
The Scottish ski resorts look like having a bumper easter.
Snow amounts on the Pennines, S uplands, Highlands, Cairngorms and Lake District are stacking up - will take a long time for these amounts to shift this year.
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If the trend continues the precipitation from the SW may indeed not reach very far into the country. The unusually powerfull block to the north will be squeezing the Atlantic low forcing part of it westwards and the remnants southeastwards into the continent. The 12Z UKMO T120 shows a very significant shift south in the pattern compared to yesterdays 12Z.Brilliant upgrade for the midlands snowfall wise!!what if the precipitation doesnt even make it into englandí ½í¸³!!
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Well, the met office are not expecting the cold snap in early march shown on most of the models so far today, a change to more unsettled and less cold weather from the northwest is what they anticipate, actually they have been saying this for days, even when the models were showing continued high pressure so it's probably best to NOT get suckered into thinking that an arctic outbreak is likely after next week because according to the experts, it won't happen, it's not even hinted at.
But with ''A large degree of uncertainty''.
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Totally disagree - with respect to Stewart and the METO - both were wrong in December and the METO did a quick volte face.
I'm surprised the METO are talking about snow early next week, I thought the 6-15 dayer would stress the uncertainty. The GFS must be a huge elephant in the room at Exeter right now.
Statistically third week in January is slightly more likely to be dominated by high pressure to our east or even north east. The Altantic will often quieten down during the second half of January. The effects of the turmoil in the stratosphere may act in our favour. Over the last few years mainly short severe spells have been occurring so it is reasonable to expect unusual events to continue to occur. If the next fortnight results in normal zonality we have to reconsider the teleconnections that we currently believe to be a useful tool in forecasting in our latitude.
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Quite agree. The cooling down later this coming week in unlikely to be connected to the stratospheric warming which is not forecast to split the vortex for another 3 days. The coming week is likely to be just a normal part of winter. It is the following weeks that all hell may break loose as the unusual events in the stratosphere start to have an influence. It is not known if we will get a few days of colder conditions, a Bartlett or a 1947 style block setting up.Really not sure where this thread is going. ! Looks to me we will see a dramatic cool down by the weekend...Let nature do the rest!!!
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Apologies if these questions have already been answered but can anyone enlighten me on the following::
1. Does Stratospheric warming occur every winter but in varying degrees of intensity.
2. Is the warming greater when the wind flow is at its stongest and at right angles to the mountain ranges.
3. Is the current warming and predicted evolution of the warming significantly different from other years.
4. Does the shape of the stratospheric temperature signal e.g. the vortex and the shape of the warm area represent low and high pressure in the stratosphere
5. Can the shape of this temperature/pressure signal in the stratosphere result in a eventual similar distribution of pressure at the surface.
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I wish
This is what the UKMO were predicting on 6th December for the period we are just entering, just about the opposite of what we are getting and about to get I would say. So hopefully their current predictions will be wrong too! I know it doesn't always work like that but you can but hope....
UK Outlook for Friday 21 Dec 2012 to Friday 4 Jan 2013:
Temperatures by both day and night are most likely to be below average during this period, with a greater incidence of overnight frost and, at times, fog or freezing fog. The signal for rain and snowfall amounts during this period shows a high degree of uncertainty, however, on balance, slightly drier conditions compared to average are favoured for most of the UK. Even though there is a drier-than-average signal for much of the UK, where precipitation does occur, there is a greater chance that it will fall as snow compared to normal.
Updated: 1136 on Thu 6 Dec 2012
Yes it is a bit wetter than their forecast suggested and a bit warmer. But it could be argued that on a global scale the forecast was reasonably accurate give or take 200 - 300 miles as condition over parts of Germany, Holland and Denmark are decidely cold today. Lets say it was close but not close enough to be of any benefit to the UK.
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Yes, that a minority thought, but I am tending to think along those lines this morning.
C
The models maintains the block to the east for the next two days and temperatures in the low countries are already down to around 3C. The very cold Russian air has been advancing across Poland overnight and it looks like continuing to advance westwards over the next couple of days. Confidence in the models seems quite high in an Atlantic dominated pattern but it is still facsinating to watch the mild advancing from the southwest at the same time as the cold is advancing from the east. In some of the earlier decades I would have backed the cold to win not but I'm not so sure these days.
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There is no reason to throw in the towel for this possible northerly, just as there was no reason to get excited about an easterly earlier in the month
There was never a potent easterly shown within the reliable timeframe (96 hours)
Nothing shown in the reliable timeframe now disregards the prospect of a Northerly. IMO the reliable timeframe for northerlies is longer than that of easterlies. (for a number of reasons which I shall not go into)
Nevertheless, there is still ample time for change. It will not take much change to make things much more favourable for a cold spell.
We have this at 144 hours.
As opposed to this.
While the current forecast looks like a west based -NAO, the potential is there for a potent cold spell with a small change. We dont have a raging polar vortex or jet stream as we did last year.
Although models now mostly agree on the evolution until T+72 it is still a knife edge situation close to the UK as very cold air currently feeding into Poland from Russia continues its journey westward over the next three day.
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But then, by the time we're past Christmas the models' outputs will, no doubt, bear little resemblance to those of today?
Sooner than that.
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12Z GFS run ismore progressive than the 06Z run especially in later frames. Slightly more consistency in nearer time frames but very cold air has become entrenched over western Russia and is starting to extend into Poland and is likely to extend further west before stalling. Consequently the high to the east may be more difficult to shift than models are currently predicting.
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OOZ UKMO and ECM still show the Russian ridge holding ground between T+72 and T+96 against what looks likely to be an eventual push from the Atlantic.
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Nearly every operational GFS run over the past two days has made westwards movement of the Russian HP in its early timescale and every time its been dismissed by the Professionals and amateurs alike. Seems to me this large HP cell is retrogressing slowly towards Iceland and maybe beyond. The computer models logic does not see this and corrects to norm as soon as possible on each operational run giving the impression that the HP is slowly decaying or being moved back East. Maybe just maybe everyone has underplayed the synopsis unfolding before us ?
While this trend in the GFS continues in its early stages there must remain the possibility, however small, of an easterly incursion before xmas.
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The one constant theme I see at present in FI is the continued tendency to see a trough move over Scandi post Xmas towards the New Year. That sort of development is something I've had my eye on for some considerable time. How much that would affect UK re cold is unknown as so many variables, but I'm comfortable that we are heading in that direction.
BFTP
ECM has a huge part of the Polar vortex situated over Siberia moving towards us between 192 and 240 with hints of a cross polar flow.
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Well this is rather different, the shortwave is ejected more SE, and HP is trying desperately to extend Westward from Scandinavia. But we still have that Iberian High preventing a better outcome.
Yes, a much better shape at T+120 than the 06Z
Model Output Discussion - 10th Jan Onwards
in Forecast Model Discussion
Posted
http://meteocentre.com/analyses/map.php?lang=en&map=eur_full&area=eur&size=large
The upper high over northern Scandinavia has intensified slightly over night and the surface high is elongating NNE - SSW. Dewpoints are falling over parts of Northern Europe and Poland has now got a renewed snow cover. The Low to the west is elongating, gradually filling and slipping SSE. All in all a good start to the day along with the westerly correction on UKMO output at around T+84.