Chesil View
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Posts posted by Chesil View
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The crazy Highs and lows people put themselves through in advance of a projected cold/snowy spell is farcical. There will be plenty more movement in tracks etc bearing in mind this is still essentially a week away. Don't wear yourselves out before it all gets here guys and gals.
Today has seen major upgrades across most models and the ecm as it so often does beyond day 7 has plumped for an outlier as its deterministic run. We saw this going on through last winter as well it has a well known habit for doing this. Be it cold or mild.
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My take this morning based purely on det runs. Gfs has moved somewhat towards ecm /ukmo in medium term. Gem best of the bunch so far for preserving longevity of cold spell.
We await ecm but again with the caveat that none of the models will have exact positions of possible snow events nailed at this range.
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11 minutes ago, bluearmy said:
Fwiw, the control diverges from the op post day 9
the runner is fifty miles further south and day 10 system is 36 hours later and runs through n France
Which just goes to show the huge range of options that are on the table regarding the movement of the lows later next week. Nobody should take getting snow or not getting snow for granted.
Exact tracks if either of them actually approach our shore wont be sorted until 24 hour beforehand and certainly not at 240 hours beforehand.
Not trying to pee on anybody's fireworks but just stating facts gleaned from more than 40 years of model watching.
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Nice to look at but far too far out to put any accuracy on where the snow line will be at this stage.
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2 minutes ago, Catacol said:
A fair point - but I'm not sure the prognosis at the moment has really deviated from the overall shape of things that was probably best expressed by Tamara a couple of her posts ago. We have the wave break now that is being pushed up to high latitude at the end of the week, we then have the cold trough dropping in. We will likely have a slower breakdown from this than the models predict (because observationally models speed up breakdowns than is usually the case once it happens) and then we have - with the less favourable MJO phases and a drop in AAM - an anomaly chart like this to wrestle with:
First of all it is a very long way off - but if we take it at face value it reflects the progression of the drivers stated above but does not really give us a scooby as to what the synoptics will be. There is certainly a pressure contrast that is still suggestive of weak -NAO but quite where the cold/warm boundary will sit is very uncertain.
Then - looking at the latest GEPS that, to my eye, has been a bit more accurate than GEFS from the 00z run we get this out in the very far reaches of ensemble modelling:
High pressure starting to build back into Greenland in line with the Nino background and drivers pointing to renewed momentum and amplification which then ties in with the EC weekly move back towards this:
So - some degree of relaxation of the cold was inevitable at the end of next week, but it does look temporary and - in any case - quite where the boundary between the warm and cold air will be is utterly impossible to nail down now. I think the overall pattern as described in that post of Tamara's remains solid.
Good post Catacol. It's easy for people to say thus has not worked or so .ych for that driver. Because they purely look at it from a snow I my backyard point of view but the overall global picture is very much as the drivers predicted. Local backyard stuff within that global pattern is down to nuance and if its snow you want a bit of luck. But the overall pattern is very much as was suggested.
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Snowing very lightly in Wyke regis as I type.
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Ecm shows a channel slider which could be very Interesting depending on the exact track.
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More choices from the envelope of ensemble solutions this morning.
Always worth remembering the models are on a global scale and as part of that the UK is on a micro scale.
A couple of hundred miles error is on a global scale is nothing and within a reasonable margin of error but on a local scale is the difference between bitter cold and mild.
The differences between the gfs 18z and 00z det runs in the medium term mean trusting those det runs past the initial retrogression is a pointless exercise.
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Let it snow and frosty ground make very good points,when looking at some of our biggest snow events. You often actually need those milder( but still cold uppers) to bring the snow fall.
I hark back to it often but the great South west blizzard of Feb 1978 came with uppers around minus 2 and produced drifts over 20 feet deep.
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Bearing in mind the difference in the position of the low pressure to the southwest between 06z and 12z at the critical time I'm more inclined to think that's it just a ensemble choice rather than a trend to bring the mild air as far north into southern England. It is a high risk high reward game but the final dice are far from having been thrown on this one.
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Light flurry of snow grains here at Wyke regis. Weymouth.
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16 minutes ago, Dorsetbred said:
Morning All, a dry yet overcast morning, after an overnight low of -1.5°C at: 01:43, currently 2.4°C, RH74% with a light breeze in from the NE - E. The soil temperature is now 4.4°C, so it's cooled nicely.
From Above a wider view this morning to see what's happening
Radar mapping
AND of course , On Golden sands
Now the cooler weather has arrived, time for winter supply check. De-icer, sand/grit snow shovel, snow tracks for car, blankets, thermos flasks, torch, and that's just to get to the car from the house. Important winter supplies ready:
Indeed Dorsetbred. Those are the supplies that count.
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7 minutes ago, prolongedSnowLover said:
The latest synoptics strongly favour Northern regions with the South at mercy of milder incursions.
Clearly nowhere near as good as the models were showing a few days ago with everything watered down.
That's always been the risk reward equation for the south from northerly sourced cold. The northerly source usually means dry for the south and therefore you need the risk of milder air nudging in to create snowfall chances.
Short of a polar low or very active cold front like the 2004 thundersnow event. Northerlies on their own are not great for southern snow chances
Edit. I see winter of 47 has said something similar above.
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Just now, Penrith Snow said:
If Netweather existed 20,000 years ago some members would be complaining about how thin the glaciers were south of the M4 corridor compared to up north!
Indeed. But very strange that 20,000 years later the M4 corridor is still so often a demarcation line for snow events.
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Models seem to be converging on a cold out come around day6/7 which is still too far out for comfort but definitely a step in the right direction.
Snow chances will be governed by day to day developments much closer to the time if the reality of the general forecast pattern materialises.
Still some scope for milder nudging air into the south on current output which could lead to high risk/high reward snow chances here but that would be highly dependent on nuances much closer to the time.
Ideally now we want to see the models firming up or even upgrading the pattern on which they appear to be converging, over the next few days. That would decrease Nick Sussex's very sensible margin for error factor.
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6 minutes ago, Bricriu said:
Well hopefully at that range it can be treated as cannon fodder.
Indeed all nwp is cannon fodder at that range. Even the sainted ECM
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Trying to look at the output at the moment can be a bit nerve shredding for southernsnow lovers at the best of times.
A couple of days back, we had cleaner retrogression and northerly plunge of some note covering the whole UK.
Now as Scott Ingham day nears the models seem a bit more reticent to go full on cold for the whole UK although the latest 06z does bring that back.
I can only assume that the various variables are making this something of a knife edge scenario which can of course bring big rewards but can equally give snow starved southerners sod all. Maybe this is one of those instances where we literally won't really have the best idea until 24/48 hours before things align.
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6 minutes ago, Weathizard said:
I do find it mildly disappointing really that we are now looking out for wedges and ridges, our proper GH has slowly wained away, at day 5 it looks absolutely primed but unfortunately we don’t ever get a clean cut off high and that LP system pumps up the Iberian heights, most cold spells in the UK start with a low undercutting a ridge or HP cell and engaging cold air to our north/east, at the moment we are lacking that proper trigger because of the issues I’ve been banging on about
Don’t get me wrong we could still strike lucky, but it just shows how one ingredient out of 20 being wrong and 19 being right can still spoil the party for us.
Indeed Weatherwizard just a couple of days ago we had cleaner retrogression and a cleaner southern jet taking lows into Europe.
Now its much more messy. oh for the seventies and eighties when northern blocking was clean cut and trigger lows actually triggered something.
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1 minute ago, northwestsnow said:
00z mean day 10 doesn't even get -5 uppers south of the Scottish border
Yesterday's day 9
Indeed NWS .Scott Ingham day steadily being pushed back on the ECM.
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Ecm.gfs ukmo and gem are roughly similar at 168 this morning. Beyond that as Carinthian said earlier various option are on the table.
For me this is a step backwards from the clean evolutions of a couple of days back. Ecm in particular pushing the arrival of any real cold from the north back to day ten yet again and that is only for the north.
It could have it right and the evolution to full on uk cold may just be a bit slower.
Overall though I'm less convinced of a UK wide cold evolution this morning from a southerners point of view and you don't get much more southern than where i am overlooking Chesil beach.
I'll reserve judgement for now as the ensembles are yet to be viewed and there are a lot of moving parts in the evolutions showing now compared to the cleaner evolutions across the models a couple of days ago.
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Just now, Mark wheeler said:
Warm outlier
Let's hope so.
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22 minutes ago, fromey said:
I ask Marco yesterday about this being a major warming and he replied
But at what strength.
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6 minutes ago, booferking said:
Take your pick you don't want the trend to weaking the heights in Greenland hopefully an outlier which we will see later but gfs op been showing this for a couple of days now.
Fair enough Booferking but in reality the hieghrs are more than enough to do what we want. The Atlantic is dead and the cold air is still coming south. Today's 12z actually holds out the hope of more snow for more people going forward than yesterday's
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Model Output Discussion - Colder but how cold and for how long?
in Forecast Model Discussion
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Thank you Tamara. I'd take Feb 1978 any day of the week.