Kentish Kiwi
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Posts posted by Kentish Kiwi
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How close does it get?
I think even without a SSW, we are likely to see a significant warming and reduction in mean zonal winds which should open the door to blocking in favourable places. November 2010 is a recent example.
Karyo
Though I would have thought a significant difference between now and November 2010 is that the warming in 2010 occurred at a time before an organised vortex could even develop properly, while now there is a huge and intense vortex that is well established across a large amount of the northern hemisphere. It would seem to me that we need a pretty powerful warming to knock such a big PV out of the poles, especially given how early in the season it is...
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Ooh is this what I think it is??? Only worrying thing with the heights trying to go to the north is that huge LP to the west of it, surely that will blast the **** out of the high?
You'd think that might be the case but...
http://www.wetterzentrale.de/archive/ra/1991/Rrea00119910202.gif
http://www.wetterzentrale.de/archive/ra/1991/Rrea00119910205.gif
Granted 1991 was a special occasion and I'm not suggesting anything similar is going to be repeated as things are currently significantly different synoptically, but just an example of how big low pressures off the west coast of Greenland can quite readily stall and are usually a positive sign as a pre-cursor to an easterly.
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Actually, up to the +192h stage, things look notably different to the ECM's evolution, with the GFS drawing up very long fetch SW/Serlies as opposed to a flatter pattern from the ECM.
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Will certainly be interesting to see if the GFS 18z gives any support to the ECM 12z, or indeed its own 06z run, in raising heights in the mid-Atlantic towards Greenland around the +240h period.
If such a trend is to develop, as hinted at by OMM, it seems to have some support from stratospheric developments and forecasts.
Edit: Is it just me or at +129h are there already significant differences over and to the west of Greenland on this run compared to the 12z...
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Is there any chance the increased amplification and hints of retrogression towards Greenland shown on the GFS 06z and now the ECM 12z could be the models picking up on the effects of the current warming taking place? Or, more excitingly, could it be the models picking up a signal for a SSW pre-cursor blocking event, given the chart Chio posted above?
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Just got a report of '4 inches' in Sevenoaks but somehow doubt it's credibility. I know it's relatively high up but don't think it'd make that much difference.
Just light sleety snizzle here now.
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Snow here in Hildenborough!
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I for one didn't, how can a weather pattern become extinct in a chaotic system?
I quite honestly can't get my head around. Seems to indicate a huge deal of ignorance and stubbornness, bordering on stupidity, which is all the more confusing as IB is obviously an intelligent enough character.
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What we can say is that Ian Brown's continued projection of a mild spell around Christmas with HP to the south is looking like a significant possibility, having gained the support of this evening's GFS and ECMWF operational runs. But it's still too far early to be celebrating a victory on the forecasting front.
Especially when he specified that the mildest Christmas period on record was a distinct possibility. It may well be odds on for a mild Christmas at this stage, but the warmth and general pattern requires a significant 'upgrade' to get near what Ian Brown has been forecasting.
It's hardly a rarity to see low pressure to the NW, high pressure to the south and SWerly winds prevailing over the UK at this time of year. Just three years ago it was expected of the period. Would be useful if somebody such as Mr Data could provide the statistics or charts illustrating record warmth over Christmas, so comparison can be made to what the models are actually presenting.
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Looks like the minor warming has already finished and the temperature has proceeded to drop like a stone once again...
http://ds.data.jma.go.jp/tcc/tcc/products/clisys/STRAT/html_e/pole30_n.html
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http://www.wetterzen..._London_ens.png
distinct change in the IOW ensembles-
As said it hinges on the atlantic ridge gaining enough elevation North & the cold air coming along the southern flank-
S
Hardly any support whatsoever for 'the mildest Christmas period on record'. Looks distinctly below-average, with the mean not rising above average at all through the whole run...
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And often when it didn't exceed 5.0C, January or Feburay or indeed both was mild.
Such as Decembers 1989, 1991 (February 92 was mild), 1992, 1996 (February 1997 was mild), 2001, 2003, 2007. So what does that tell us?
January or February was very often mild in that period, whilst December was much less so. That is all that tells us.
Bingo. A quite concise illustration of how data/statistics can be moulded and influenced to support a contrasting statement or point of view.
I must say I'm rather disheartened by the increased frequency with which the 'christmas pudding' has been referred to... I'd hoped we'd have moved on from that exasperating business by now.
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The odds of the positioning of the low and intensity are very low for storms 6 days away <30% chance
BBC are only airing warning because the UK experienced a notable storm a few days ago
This is typical British weather for Autumn and Winter
So I will say this again...it's SIX days away. If by Wednesday the track and intensity is the same than we can be 70% sure what we are dealing with.
These storms are extremely difficult to predict. Even 3 days away, let alone 6.
True, such storms are enormously difficult to model accurately and it is 5/6 days away so may well be downgraded significantly. However, I would strongly dispute your claim that this is 'typical British weather for Autumn and Winter'.
The storm that hit Scotland, Ireland and Northern England two/three days ago wasn't 'typical' and nor are the two lows forecast by the GFS for the coming week. These are significant extra-tropical storm systems of notable intensity. It is not at all typical to see three depressions, all with sea-level pressures below 960 (because that is possibility given the modeling) sweep through the UK in the space of a week.
Given the state of the stratosphere and polar vortex, and particularly after the generally successful modeling of the storm on Thursday, additional attention and caution should be paid to these potential events in my opinion. In fact, from what I witnessed, Thursday's storm was gradually upgraded as it neared (apart from I believe a very slight last minute weakening) rather than the usual downgrades we are so well accustomed to, although I doubt there is much potential whatsoever for the the storm on the 18z GFS to be upgraded.
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Squall line has just hit here. Pretty violent weather for this area. Probably the stormiest looking scene outside that I've seen for a few years to be honest.
Calmer all ready.
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125 years since this event
Interesting how similar the storm shown on the ECM 00z looked to this event.
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The uppers aren't too far off, and with some evaporative cooling should be enough, some of the best snowfalls here have been with the dodgiest uppers.
Personally I think we are crucially lacking low temperatures and dewpoints over the near continent for that chart to deliver anything significantly wintry to southern Britain.
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ECM showing an interesting little storm at 192, that if it were to come off, would cause blizzards possible with severe gales and heavy snow over much of southern Britain.
Good old FI!
Somehow I don't think the upper will be quite low enough for blizzards...
Certainly very interesting though, with very strong winds for this part of the country. Would be quite the little storm.
A very clear signal from the ECM for the jet to track south, would have been immersurably more exciting if we had a cold/snow covered continent and northerly blocking of some kind. Nevertheless certainly something of more interest for southern members from this evening runs.
Looking at the charts again, it really is such shame there's no cold pool to tap into to the east, otherwise the ECM from +192h through to +240h could have been something quite special... -_-
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As I've stated before, it might not look exactly like this due to La Nina, but could there be very tentative signs of the tropospheric polar vortex at least becoming stretched into an odd shape, which might open the door for wave breaking into the stratospheric vortex at the end of the month ?
By this do you at all mean you expect there to be a more NE/Eerly component to the wind direction, with stronger blocking over Scandinavia, rather than the general northerly that seems to be illustrated GP?
That particular composite for January looks rather similar to the kind of set-up experienced midway through December 2010 to my decidedly amateur eye...
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Are you saying this for the whole winter or for just the coming days? I hope it's the latter.
Just the coming days. No one has can accurately predict the end of this week let alone the rest of the winter. Personally I doubt there'll be much for the Midlands, south (in terms of snowfall) until at least after Christmas or New Years but things could change drastically should the stratosphere warm suddenly.
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Ok, but hasn't GFS been poorest performer of late and so I assume that support would be needed from euros too? Wouldn't the strong PV have had us in that situation now if it was the controlling factor and the default set up? Or is the PV set to intensify further? For me we will need euros on board and a few more days of consistent runs.
Whilst the coldest of any weather is for the north I think over a period of ten days if this set continues I think for the south average is better description.
BFTP
Like it or not the stratospheric signal would provide reasonably strong support for an evolution akin to the GFS 06z. I get the feeling we've been pretty 'lucky' with the current cold snap and indeed we are fortunate to have the one forecast for later this week.
The stratosphere has been at record or near record levels of cold for a while now and it seems inevitable that we revert to such a pattern as illustrated on this mornings run eventually. This is particularly significant taking into account the usual lag time for the effects of the stratosphere to be felt in the lower levels of the troposphere.
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Hopefully,the only way is up!
Doesn't look like it!
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For London & the SE, perhaps Whipsnade or High Wycombe.
Pretty certain, as Aaron says, the North Downs are snowier than those two locations, primarily due to a favourable combination of their altitude and proximity to the sea. Also their exposure to the 'famous' Thames Streamer is a significant factor - they can actually be one of the hardest hit areas in England under a potent easterly and a a supportive wind direction (specifically more ENEerly).
I would suggest that places such as Blotley Hill (267m & highest point on the North Downs) or the area around Biggin Hill, which is directly in the firing line of the Thames Streamer, would be in contention for snowiest area in the SE. Locally, but slightly further south, the town of Crowborough (242m asl) is also often mentioned and regarded as being particularly hard hit by snow.
Leith Hill (294m asl and part of the Greensand Ridge) in Surrey is also surely a strong contender, being the highest point in the SE (south of London), second highest in the whole of the region by only 3m, and also in an overall favourable location for a variety of snow set-ups. It is also slightly further from the UHI of London than the above areas of the North Downs which may be a contributing factor, at least in retaining snowcover, although I am uncertain what impact London's UHI has on areas of the North Downs that have relatively significant altitude.
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Is there any evidence to say that the colder the stratosphere prior to an SSW event, the greater its impact is? (if such a thing can be judge upon its 'impact'...) ie. whether this extremely cold stratosphere we are currently experiencing could ironically aid our prospects for cold should an SSW occur?
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Has anyone else noticed that in early Spring, it can get rather balmy on sunny days but when this happens, the temperature often drops heavily over night (and sometimes we get a frost). Meanwhile, in late Autumn, the temperature sometimes doesn't drop much overnight and the sun has little impact during the day.
Once again a result of the latent heat held by the land and sea and the residule cold after the winter.
Stratosphere Temperature Watch 2011/2012
in Spring Weather Discussion
Posted
Indeed, it seems to me as though the forecasts for a significant warming of the stratosphere have been gaining a little bit of momentum with every new day over the last couple of weeks, although this obviously will come to a halt at some point.
I am quite weary of Chiono's point about the possibility of the polar vortex reestablishing itself quickly if the warming is not significant enough to "burst" it.