Rob K
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Posts posted by Rob K
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We won't see any atlantic influence in this run, the energy is being directed to the west
Ha, until GFS goes bonkers http://www.wetterzentrale.de/pics/Rtavn2281.png
I somehow don't think this run will verify!
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Its almost identical to previous outputs so far, nothing wrong within 60h.
Not true, the 0C isotherm is at least 30 miles further west on this run!
Seriously, all looks on track still. It's coming, 6 hours at a time.
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I do wish people would stop mentioning 1991. We're not looking at that sort of easterly. At all.
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GFS 06z Ensembles;
http://www.meteociel...1&ville=Londres
Some very cold members in there along with some less cold members.
Control & Operational close to the mean throughout the most part however.
Certainly more signs of milder stuff after midmonth than on the last run, but I suspect it would only be fairly temporary, The Aberdeen ensemble shows the cold air is not far to the north: http://www.wetterzentrale.de/pics/MT8_Aberdeen_ens.png
My feeling is still erring to an attack (possibly snowy) from the SW, a brief warm up and then retrogession to Greenland and the possibility of some properly cold air coming down from the NE rather than the modest cold from the east that we are likely to see next week.
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One thing that's a bit worrying perhaps is an increasing trend for low pressure to the SW/S. NAEFS pressure anomalies 00z at +240
That low pressure anomaly to the South/South West looks a little too close for comfort for me, on some of the OP runs and ensembles too. Hopefully if there's low pressure to the south/SW it will slide underneath perhaps giving us big snow events and keep the cold easterlies going, we don't want too much influence of low pressure to the S/SW though or it could bring in rain and milder air from the Atlantic. Need that block nice and strong too.
It's a balancing act though. If the block is too strong then you end up with most of the UK under 1030mb+ and very little precipitation around. With the LP to the south and a feed from the SE then as long as you can keep the uppers below about -2C then you can get some monster snowfall.
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Yes Steve. I am not bothered about the fine detail for next week of the exact shape of the Scandi high and "Will it snow in Snivelling-on-Sea?" etc, but looking at the longer trend of the last three GFS runs in FI they have followed a very similar theme to our NE. I smell a trend and that trend says "Greenland High for Christmas". It's looking a bit 2010-ish.
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Based on GFS FI trends over the past couple of runs I could actually see a Dec 2010 style event later in the month with a big Greenland High and the PV dropping down over us. Given that hadn't happened in 55 years before 2010, to have it occur again after two years would be pretty rare, but the general pattern certainly makes it possible.
In he meantime, ECM on the face of it may look like a downgrade but those charts would bury much of the country in snow.
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i am not sure saying this chart is not cold
It is very much the coldest of any output though (e.g. GFS here http://www.wetterzentrale.de/pics/Rtavn2162.png ) and even then it's not a patch on the sheer size and depth of the 1987, or the intensity of the 1991 cold pool: http://www.wetterzentrale.de/pics/archive/ra/1991/Rrea00219910207.gif
But 2009 would be plenty good enough for me - we got a good 15cm of snow round here with twice that on the Downs.
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The longer the easterly digs in for the colder it will get. The ECM post 192 hrs, you're looking at sub zero maxes......except for right on the east coast.
Even with -8 uppers you'd be looking at barely getting above freezing inland after a few days. A combination of little solar input (near shortest day), CAA from continent and general cooling of the landmass would see us struggle above freezing after a few days. All conjecture though at this range.
Yes it would get colder. But to see people asking whether it could be as cold as 1987 or 1991 is just asking for disappointment. No there is nothing on any model that suggests anything remotely as severe as those legendary spells. Something more akin to early Feb 2009 is a better match: http://www.wetterzentrale.de/pics/archive/ra/2009/Rrea00120090202.gif
which led to http://en.wikipedia.org/wiki/February_2009_Great_Britain_and_Ireland_snowfall
And even there the 850s were generally colder than I expect next week.
I think a few people are getting unrealistic - yes we've got an easterly on the horizon but not a mega cold one.
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Yes some of next weeks projected charts bear a canny resemblance to that amazing 6 day event.
Which just got worse and worse - Nice 7 days of School though
Jan 87 was very extreme though because not only did the synoptics fall into place but they also did so at exactly the right time when there was a deep cold pool over the continent: http://www.wetterzen...00219870112.gif
Even if next week's easterly is the most perfectly aligned, the cold pool is likely to be a good 10C warmer than that, even if you go by the more "extreme" ECM charts: http://www.wetterzentrale.de/pics/Recm2162.gif , so I hope nobody is expecting anything to compare with that one. No subzero maxes likely on this one, more like +2C with a nagging breeze.
GFS shows the 850s even less cold, more like -8C.
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Is this what we are about to be having or will it be worse than this .
If that is a 1991 forecast (I'm on my mobile so can't watch it now) then no chance. That was a once in a lifetime easterly. Next week I'd expect highs of +2c by the end of the week and a few snow showers with modest accumulations in favoured spots. I certainly wouldn't expect snowy Armageddon!
Put it this way - I can't see anything as severe and snowy as Dec 2010 (or Jan 2010 when I got 25cm+ of snow here in Hampshire).
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Decent clustering up until the 14th, there after more scatter as you would expect, with the Op on the mild side of its suite;
http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=507&y=16
Very solid agreement of a 3-day easterly from the 11th to 14th at least. Although what are the chances that one solitary outlier has nailed it?
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Going to score this run at 9.5 out of a possible 12, mainly because it falls away at the end, The crucial thing now is not the many permutations of the easterly that the models may evolve over the coming days, but getting the building blocks right pre the 120hrs mark.
I actually think the final stages of the run in FI are quite encouraging, despite the fine detail. The PV relocating to Siberia is what needs to happen to keep the cold going. Otherwise the cold pool just runs out from the east and we get a gradual grey mushy warm-up.
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Purple blob by any chance?
That'll be Mr P. Vortex who has decided to visit Russia for Christmas, paving the way for a Greenland high to build and a shedload of cold air to come down to Britain from the north... http://www.wetterzentrale.de/pics/Rtavn3842.png
(ignore the Dec 21 Mayan Apocalypse LP there and look at the general theme...)
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not on that chart bd. not sure what you're seeing other than an atlantic depression
the siberian chunk isnt really moving
Indeed not on that chart but I seem to recall back in December 2010 we were effectively under a chunk of the PV which dropped down through the North Sea...
http://www.wetterzen...00120101216.gif
http://www.wetterzen...00120101217.gif
http://www.wetterzen...00120101218.gif
The 06Z GFS control run actually did something rather similar in deep FI.
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Could it be argued, we could be looking at a win-win situation, or is there the usual spoilers that could bring an end to the party before it even starts?
With the UK being where it is, there are always potential spoilers! However I would risk saying that the pattern looks pretty well locked in to bring an easterly for at least a few days, but that could be a weak and modified northeaster, a southeasterly, a slack easterly flow or a full-blooded beast from the east, depending on the exact position and shape of the block.
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A question about the PV: I thought the signals were meant to be that it was going to head to the Siberian side of the pole, so why have the models over the past 24 hours seemingly ramped it up over NW Canada?
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The ECM is consistent and that for me is the main thing to come out of this mornings runs.
Yes, consistent in that the easterly is still at 240 hours, just as it was 240 hours ago ;-)
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GFS 00z ensembles certainly suggest a big shift away from a cold solution for the UK with the block too far east. Still at least the block looks like forming which is a good first step.
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http://www.wetterzentrale.de/pics/MT8_London_ens.png
So the "dreadful" 18z was actually one of the coldest options?
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Or perhaps not. GFS officially loses it there.
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And here come the Atlantic south westerlies after blowing away a block the size of Europe and half of Asia, like a dandelion in the breeze lol.
South westerlies? Where? Slider all the way there.
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Greenland High about to come into play I think. Nowhere for the Atlantic to go.
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Did I mention southerlies? http://www.wetterzentrale.de/pics/Rtavn2161.png
I'd still back the cold air as there is nowhere for that low to go but underneath...
Model Output Discussion 5/12/2012 18Z onwards - the one after THAT ECM
in Forecast Model Discussion
Posted
Nice chart comparison there. Sadly for some people here it seems if it's not Jan 1987 from now until next March it's a disappointment.