oasis
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Posts posted by oasis
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Question: Does anyone know if the average u wind speed of the stratospheric vortex in winter has been increasing over the past 30 years? I know the stratosphere has been getting colder, so I wonder if this is encouraging a trend towards a stronger stratospheric vortex, and our winters experiencing less northern blocking/cold weather.
Or is it that the stratospheric/troposphere vortex is just becoming stronger specifically in the Greenland area? As a result of some other forcing such as the omnipresent NE Pacific ridge? It seems, at least anecdotally, that North America has continued to see similar amounts of arctic outbreaks from the vortex breaking down in the past 30 years.
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1 hour ago, JBMWeatherForever said:
The Artic Sea Ice extent seems to be back within the standard 1981- 2010 average deviation in the graph I am looking at https://nsidc.org/data/seaice_indexThe question I was raising was therefore whether the sea ice melt would indeed have as much of an effect this winter on the northern hemisphere cold air distribution. Some effect, Yes certainly, but more effect this year than previous ?
Hello. Yes, it does seem a bit higher, though not by a massive amount. Also, from what I've read recently, the amount of ice is still very low on our side of the Arctic. So, around Svalbard etc. So I'm not sure that this increased amount will have much effect on autumnal/winter weather patterns.
Ie, to keep on topic, charts for the next week have the jet stream passing just to the north of Scotland and leaving the south of England untouched. Which could be linked to lack of sea ice.
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7 minutes ago, Quicksilver1989 said:
Yes ideally because this would allow northerlies to stunt the progression of mild air across the UK.
The other alternatives are a weak low that fizzles out in the channel or a low that tracks through central Europe instead (looking unlikely now for the low to take that path).Curious, ICON looked a lot better for coldies with the low pressure earlier in run, and then later on marginally so.
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ICON at +60 has the low pressure in the Atlantic further south. Not sure if that's a good sign. Though high pressure migrating quicker west towards Greenland. For coldies do we want the high pressure to migrate slower towards Greenland?
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2 minutes ago, Quicksilver1989 said:
I think its just noise, I can only count 3 runs that pursue a scenario where pressure is higher to a significant extent in the north, the cold pool over Scandi still hits the UK albeit more the south.
There is always going to be a bit of noise, in fact 19 ensemble members show the Scandi cold pool having a clean hit on the UK so an unusually low level of noise.
Some GFS runs develop a small low and send it to Greenland but that will get gobbled up by the high pressure anyway
Thanks. Yeah, I guess with ECM and UKMO on board as well you'd expect the overwhelming majority to be correct. In a more zonal situation 19/22 would normally prevail.. And as you point out, even on those runs where a northerly sets up you still get some of an easterly in the south.
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Just now, Quicksilver1989 said:
Looking at the 18z OP, I calculated the CET estimate for the first 10 days of March and it came to an amazing -1.3C
and thats with the milder weather at the end! Some crazy minimums over the snow fields.
Anyhow just had a look at the ensembles and most of them show a battle with milder air from the Azores low trying to make its way through. However the majority support the OP in keeping us in the cold air under a slack regime.... so maybe that CET estimate for the first 10 days of March may not be too unrealistic....What do you think of the couple of ensembles which drag high pressure quickly to Greenland? Noise? Or still potentially a signal to be aware of?
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To my eye there are still a couple of GFS 18z ensembles which quickly take the high pressure to greenland and rapidly cut off the easterly flow from the deep cold pool. I think related to @bluearmy's shortwave point earlier. So, hopefully from a coldie perspective that cluster goes from 10% to 0% tomorrow. They are still cold though.
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The more of a straight southerly flow into the arctic, the higher latitude the high pressure will establish itself. If there is a bit of jet energy pushing east like on the ECM, then the high pressure will establish further south. Though if it too much energy goes east then obviously the high will completely collapse. Hopefully the latter won't happen, and at least some part of the UK gets pasted.
And at +168 on ECM we see a sub -20 cold pool setting up in Poland waiting to be advected westwards.
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I think UKMO would potentially be better for those living further north, due to its higher position, while ECM would potentially be better for southeners. A la GEM, sub -15 uppers and all that. Of course the run is still to complete, but seems it could set up that way.
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ECM 96 seems better than GFS 96. Though not knowledgeable enough to know how it will turn out. Less intense vortex south of Greenland, stronger high pressure over Scandinavia. Seems kinda similar to ICON.
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4 minutes ago, s4lancia said:
Agree 100% with your thinking. I suspect the ops problem is the hi res is over reacting and running with wrong? signals
It would be nice from a coldie's perspective if that was the case. I think someone said it's the biggest stratospheric reversal in many, many years. With all that cold pooling on the models to the north east seems -10 850 temperatures with day time maxes no higher than 3 or 4 degrees are almost guaranteed if the jet energy can dive south. And as mentioned that's the very peak if the sun comes out, from 12pm till 4pm.
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Just a thought, but could the higher resolution of the good models ops actually be lowering their accuracy at this moment in time? Maybe the operationals are picking up in more detail other parts of the climate system like GWO and MJO, parts which are against mega extensive blocking, thus diluting higher blocking in them, while the lower resolution runs are not able to pick up so much detail on the MJO/GWO and are instead more purely reacting to the overwhelming stratospheric signal? Hence more extensive northerly blocking in the lower resolution runs and the lower resolution models?
Would anyone know if the higher resolution runs are more higher resolution relative to lower resolutions runs in the strat or with regards to tropical feedbacks? @chionomaniac @Steve Murr @bluearmy @Catacol Plus anyone else interested who could answer my question.
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4 minutes ago, bluearmy said:
The eps and GEFS mean height anomoly at day 15 almost identical on a hemispheric level - can't say I recall that happening too often.
The two vortex centres just ne of Alaska and far ne of Siberia. - very strange charts, if only in their agreement! ..
I saw mentioned about lack of stratopsheric tropospheric coupling in near future, suppose if these charts can happen, that would mean upper vortex not filtering down?
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Is this the right place to put this? Jason Furtado suggesting lack of stratospheric troposphere coupling in foreseeable future, which I think means tropospheric weather patterns can run their course without intereference from the stratosphere. Good news for cold weather fans if current long range forecasts continue as they are. Ie, strengthening vortex won't cause problems from above.
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3 minutes ago, bluearmy said:
Maybe time to say that arctic ridges are funny old things and the cold evolution currently on the table is very reliant on the behaviour of one of these - hard to watch without getting too excited but for a few days probably the best policy .......
Question I would ask, if this hypothetically happened something like shown on 12z run, is it 2 weeks too early? Maxes showing at 5-7 in south on 12z.
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To my eyes, gfs ensemble mean at 10 days better on 12z than on 6z. Stronger looking high pressure over arctic.
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ECM showing siberian high extending further into the Arctic than GFS at +240. Expands from 216 to 240.
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8 minutes ago, bluearmy said:
Good ol Friday pub run ............
btw, I say it every November but you really should look at fi on the NH profile at this time of year to get the most fun!
Some of those ensembles heights over Arctic are very high. The op run a cross polar flow - crazy. Pushing those blue 850 hpa temperatures into Svalbard and around.
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Steve Murr if reading, we're seeing a lot of stressed vortexes in the ensembles at t 240+, I remember reading something last year about the Arctic oscillation in November quite often being connected to winter CET. Somethng about at least 1 month being colder. Was that you? If so, that theory may be tested this year, if the AO can be negative for the month.
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Looking through ensembles at T240 IMHO I'd classify about five (25%) of them - tops - as having a healthy,strong vortex. Does anyone remember if that's normal for november? For so many ensembles with stressed vortexes to appear?
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Ensemble mean on 18z at 120 high pressure to NE marginally stronger, troughing orientated slightly more N-S than on 12z. Little things built up like that over a couple of days could help keep high pressure more in place to the NE for longer. I think assisting in wave breaking and stress in vortex? With possible consequences down the line.
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17 minutes ago, Northern Sky said:
Yes it always seems to be the case year after year. It does make me wonder why this happens and if it would be possible for the models to be tweaked to correct this?
Height rises around or towards Greenland should always be viewed with a very sceptical eye until they get within at least 120hrs - probably less. That way you save yourself a lot of disappointment.
6z not quite so bad. Weakish UK heights sort of holding on. Yes is odd, though what is weird is that we have seen the height rises in Spring and Summer.
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Ah, ok, perhaps I misinterpreted what the person on TWO said about cold decembers being statistically colder. Maybe slightly different parameter. I always prefer snow in December - just 'cause it lasts longer.
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39 minutes ago, Daniel Smith said:
There's no straight forward answer.
Greenland blocking could produce widespread snow in late November but also nothing in the middle of winter. It depends entirely on where the "cold" is. If the cold air has been shunted to the opposite side of the pole then there'd be no significant cold air for the block to "tap into" to to speak.
But generally speaking, mid-late November through until about mid-late March. Any earlier and the cold hasn't really become established, any later and the cold has thinned significantly as summer edges closer.
Hmm, yes, I think I'd agree on mid late November. Late Nov 2010 was pretty awesome.
and thats with the milder weather at the end! Some crazy minimums over the snow fields.
Stratosphere and Polar Vortex Watch
in Spring Weather Discussion
Posted
Thank you Interitus, Knocker and Singularity for taking the time to respond to me. I greatly appreciate it. I dont have the links to the data and analogs at hand/the necessary knowledge so cheers.
Looks very interesting Singularity, curious how each decade has had slightly different patterns regionally. Certainly to my untrained eye does look like in general the temperature gradient between polar and mid latitudes has become stronger in our region of the world than in North America. Hence greater mobility in the Atlantic sector.
Amy Butler's tweet offers some reassurance though.