Stu_London
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Posts posted by Stu_London
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Just now, 1947s coming said:
Hi I have never posted in here ,have once in my local thread . Have followed this site many years tho and always liked winter weather . I have tried to learn a little from here. So we have a possible block setting up close to Greenland and a flow from the north possible for the uk. If that high could then move a little east we could then move into a north , north east flow and with a possible cold east to feed from could the beast be lurking . Snow and ice maps looking very similar to 2010 . Can we count the cold spell down with bumps along the way
️. Go easy my first post in here thanks
Welcome - 2010 is probably the best analog at the moment (certainly for the 21st Century), but there are lots of differences and this set up doesn't quite look good enough (yet) to deliver anything on a par with that both in terms of severity and longevity.
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Great models today but lets look at some of the downside risks.
1) Its way too far out to have too much confidence yet - similar charts by the weekend and then we can be reasonably confident of a cold snap/spell.
2) GFS tends to move things east when it gets more into the reliable timeframe. That might push most of the colder uppers and PPN away from us - particularly western areas. Particular attention needs to be paid to the UKMO and ECM as they are better at modelling this sort of correction. If one of them jumps ship, I would be worried.
3) Watering down of the 850s - marginality is more of an issue earlier in the season (remember last December?) due to generally higher dew points - anywhere above -9C 850s might get a wintry mix rather than settling snow. The south and coasts most susceptible to this.
4) Not many hard frosts ahead of the cold - soil/ground temps might be an issue.
5) PPN amounts and distribution can and will change - there could be quite a lot less around. The nearer the purples get to us the better, but we don't want any features blowing up too much as warmer uppers will get mixed in.
Not to be a party-pooper - just thought it was worth highlighting the risks, and, on the upside, I agree with Mike Poole that upgrades are certainly possible.
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Another good operational from the GFS - lets see if the ensembles can tighten a little and we lose some of those +5 to + 10 850s.
I assume these runs are similar to last nights 18z which introduced southerlies after a brief flirt with the cold.
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7 minutes ago, Mapantz said:
Cross model agreement at 240 doesn't mean a great deal from what I have seen over the year. I don't quite understand how anyone could say odds on at 8, 9 or 10 days?!
Better chance than without that agreement, but nothing odds on at that range and still a lot of variance with the ensembles at that sort of range, as would be expected.
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11 minutes ago, Battleground Snow said:
How many days out in 2010 was there broad model consensus? My memory isn't great...
With 11 years advancement in models you would hope they have got more accurate in the mid term.
I think the drivers were similar back then, apart from QBO was westerly.
I remember the build up quite well.
A few GFS op runs started to build heights into Greenland with a potent northerly blast at +330 - not much ensemble support.
Dropped the idea for quite a few runs with some bizarre flip flopping output until about the range of day 11-12.
Ensemble and cross model support was excellent by 120-144.
Difference with 2010 was we had a complete PV split with a lobe eventually falling right over the UK (responsible for those bone chilling mins going down to near -20C) and - not so many runs showing that sort of scenario - if fact this currently looks like a 7 day cold spell at best with heights eventually recovering over Iberia as the high sinks. Also as others have mentioned, it wouldn't take a lot for the whole lot to get shunted east and we and up coldish and dry - not a lot of wiggle room with that one.
So, as ever, more runs needed
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16 minutes ago, Allseasons-si said:
Here is the full animation in all it's glory from 192 to 384 hrs
500's/850's and Geopotential height anomaly.
Very nice - if I was being hyper-critical I'd like the more to be made of the cut off lows to the west of Portugal. Otherwise, later, the heights spill into Iberia and the longevity of the cold is then in jeopardy. But miles away yet and a lot can and will change.
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1 minute ago, Ed Stone said:
Today's GFS 12Z operational: a run that screams POTENTIAL! It's not nailed on, but even 2010 had to start somewhere! And, with all those anomalously warm SSTs around these islands, thundersnow might be experienced?
Yep I would imagine a lot on instability and potential disturbances as tends to be the case early in the season and was, if I recall correctly, a feature of the early part of the Nov/Dec 2009 event
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Just now, Eagle Eye said:
248 hours and we've got snow in Kent, crikey...
Haha - thats a very, very narrow band - might a case of snow in the back garden and cold rain at the front of the house (depends how big your house is I suppose).
Another decent cold spell GFS op - looks like there is a trend towards cross model and ensemble agreement, but probably a way to go there.
This has been a classic GFS modelling episode. About a week ago, a couple of eye watering operation and control runs, with very little support elsewhere in the ensembles. Then all cold dropped for a couple of days - then its all back on again.
My prediction is as we countdown - from now to +96 slight upgrades then either a very subtle watering down of the spell between 0-96, or a spoiler (like what happened with Storm Darcy in February) makes a late appearance.
Going back to a previous point - never discount a potential trend in deep FI if the operational and control are onto it, even if no other support. That's how Nov 2009 was modelled in deep FI on the GFS initially
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18 minutes ago, Paul said:
Latest blog from @Nick F - a preview of the upcoming winter forecast, and a very interesting read.
Not The Winter Forecast: A preview of the potential influencers of Winter 2021/2022
WWW.NETWEATHER.TVA look at the global drivers that may determine whether winter 2021-22 will be mild, average or cold. The Netweather Winter forecast will be issued later this month.An excellent read.
Two things I take out of it.
1) Unlikely to be an all out TM atlantic driven zonal winter - this is largely backed up by the current model output as it is usually around now to mid December that a pattern of that nature would lock in.
2) So many variables to consider. Very difficult to put all the jigsaw pieces together and so many potential derailments along the way. All power to Nick's elbow for taking it on.
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33 minutes ago, Allseasons-si said:
The tpv is in all kinds of trouble on this run,...it's almost spaced out and cannot be bothered this year and on the ropes in the naughty corner,in fact it has been on the ropes all year,...stay there
Yes some very interesting NH charts tonight - no real cold for the UK to tap into yet, but good signs that we will not be seeing a flat PV as we head to the end of the month.
I always feel the last half of November is critical for early winter prospects. If zonal conditions set up during this period, it can often mean curtains for meaningful wintry weather through December and most of January. Thankfully, prospects of that look a little way off, but things can change.
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8 minutes ago, jon snow said:
This is nae bad, I cannae wait!
Superb cold rain charts
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Models seem to be trending a bit more zonal in the medium term. TS Wanda looks like giving the +NAO a bit of shot in the arm next week.
Not full on blow-torch and not a particular worry at this time of year unless the pattern becomes really embedded.
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In some ways with everything that is going on, it might be better not to have a prolonged severe spell akin to December 2010 as the country might be pushed to the brink.
Perhaps a very severe event, like January 1987, that only lasts a few days in amongst an otherwise largely benign winter would be enough excitement for cold and snow lovers, without putting the country under too much pressure.
Sadly, weather is not available to order, so what will be, will be. But it would be rather ironic if we did get prolonged or multiple severe weather when as a nation we are at our most vulnerable to it in quite some time.
Of course, severe winter weather isn't all about cold. Being battered by gales and rain for months on end could be just as destructive and is probably a lot more likely than cold snowy weather.
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From a coldie perspective, I think 2020-1 was a bit under-rated. Granted the south did not always benefit in the way the forecast models were predicting in terms of snowfall, which for some would be disappointing, however we did manage a full week of snow cover here in February and midlands northwards had multiple events.
In addition, there were a fair few occasions where the marginality chips just fell the wrong way, so it could be argued that it was a little unlucky that there were not a few more events, that might have just tipped the balance and made it more of a 'classic' winter.
Given the background signals and the knack of colder, snowier winters tending to come in small groups of 2 or 3 in 21st Century, the prospects for this winter delivering could be considered better than average, although there are so many variables, it is impossible to have any confidence.
For any front loaded winter to occur, I'd be looking to avoid above average SSTs in the immediately vicinity as they tend to have a detrimental effect on dewpoints. Later in the season, we will probably be looking to the east as has become the norm as the battleground events that were a feature of my younger years, have become generally rarer in recent times.
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surprised we are still getting little phases of spotless days at this stage.
either we are not as far into the cycle as perhaps some think or we are in for a patchy cycle with periods of high activity interspersed with quieter than normal periods. Probably makes for a weakish cycle overall. Whether it is stronger than SC24 still looks a little in the balance. Whether some sort of grand minimum is underway wont become clearer until SC26.
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If I was sitting on a 15.5C guess I would be quite happy.
However, I didn't enter the competition, so ambivalence for me
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Reasonable chance the last 14 days of August will be in the range of 15.9C-16.4C (a continuation of mild night/average or below day theme)
It it is at the lower end of the prediction, then a sum 16C month could be possible after recalibration of the data
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The usually north west / south east split was perhaps more west / east at the start of the month. Perhaps Sheffield found itself favourably positioned compared to some of the more western CET stations - only explanation I can think of.
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Perhaps a small fall over the next couple of days, with a small rise in the last couple of days of the month.
With adjustments probably mid 15s - so above average but not particularly noteworthy.
Borderline exceptional warmth for the first half of the month, particularly in the south east, which wont be fully recognised in the CET figures.
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died down here - impressive cell however - more for the intensity of the rain than anything else. A few good flashes and bangs thrown in.
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Torrential rain and a few rumbles of thunder in Tunbridge Wells.
One big flash of lightning a few mins back
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Quite a warm looking 18z, although most of it is more to the southeast, so how much impact to the CET the warmth will have is debatable, even if it were to verify.
Quite striking how this year we have had a couple of flip-flop changes very close to the change of calender months.
Bone dry April followed by May monsoon.
Cold May (albeit warmed up a bit the last couple of days) - to what looks like, at this early stage, being a fairly warm June.
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23 minutes ago, BornFromTheVoid said:
Assuming a post corrections May CET of ~9.8C, the next big target becomes an April to June average of under 10C. This was last achieved in 1923, and would require a June CET under 13.7C this year (June <13.7C was reached quite recently too, in both 2012 and 2013)
9.8 would also leave us needed June to be sub 14.9C for the period 01.01.21-30.06.21 to be below the 1961-90 average.
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2 hours ago, Roger J Smith said:
EWP closing in on 100 mm, was 84 mm to 19th, then yesterday's downpours especially heavy in north Wales and northwest England, look to add 10-12 mm as smaller amounts fell in the southeast. The 10-day GFS outlook now about 20-25 mm mostly from this weekend's rainfall plus the tail end of today's portion of the event. That all adds up to around 120 mm but could go a bit higher, guidance would have to be seriously off to get us to the record but for what it's worth this is the top twenty of May rainfalls (precip if it snowed) in the past 255 tries (with their CET values for May and June to September in brackets):
Rank _ Year _ May EWP _ (CET May to Sep)
01 _ 1773 __ 151.8 mm (10.3, 14.7, 15.9, 17.2, 12.4)
02 _ 1782 __ 142.4 mm ( 9.0, 14.9, 15.6, 14.2, 13.3)
03 _ 1967 __ 140.7 mm (10.4, 14.0, 16.7, 15.7, 13.5)
04 _ 1932 __ 129.6 mm (10.5, 14.1, 16.1, 17.1, 12.9)
05 _ 1843 __ 129.1 mm (10.4, 12.8, 14.8, 15.3, 14.4)
06 _ 1886 __ 123.1 mm (10.3, 13.6, 15.9, 15.8, 13.6)
07 _ 1924 __ 122.4 mm (11.6, 13.9, 15.3, 14.1, 13.3)
08 _ 1811 __ 121.9 mm (12.8, 14.1, 16.1, 14.4, 13.7)
09 _ 1869 __ 121.5 mm ( 9.6, 13.2, 17.3, 15.5, 14.4)
10 _ 1979 __ 119.1 mm (10.0, 13.9, 16.2, 14.9, 13.5)
11 _ 2007 __ 118.4 mm (11.9, 15.1, 15.2, 15.4, 13.8)
12 _ 1878 __ 117.6 mm (11.8, 15.1, 16.6, 16.2, 13.3)
13 _ 1969 __ 115.8 mm (11.2, 13.9, 16.8, 16.4, 13.9)
14 _ 1983 __ 115.2 mm (10.3, 14.4, 19.5, 17.3, 13.7)
15 _ 1807 __ 113.9 mm (11.8, 14.2, 17.1, 16.9, 10.5)
16 _ 2006 __ 111.8 mm (12.3, 15.9, 19.7, 16.1, 16.8)
17 _ 1796 __ 110.4 mm (10.3, 13.9, 14.7, 15.9, 14.6)
18 _ 1813 __ 110.1 mm (11.6, 13.6, 15.0, 14.5, 12.5)
19 _ 1797 __ 109.5 mm (11.3, 13.6, 17.3, 15.8, 12.5)
20 _ 1766 __ 108.1 mm ( 9.7, 13.7, 15.7, 16.6, 13.3)
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(averages for CET) __ (10.86, 14.15, 16.38, 15.77, 13.50)
... so as you might expect, rather cool May values, lingering cool into June, July quite a mix, Aug tending more seasonable and Sept rather cool also).
... as to rainfalls in the summer seasons that followed these wet Mays, the tendency seemed to be for at least one month to be quite dry but it ranged from June to August, and one or two (like 2007 and also 1782) had quite a prolonged wet spell.
... the only thing these wet Mays can say about summer forecast might be to expect one hot, dry month somewhere in the mix, it seemed to happen more often than not. also, some near misses (rank 21-30) included some other hot summers like 1955, so that perhaps 1983 and 2006 being in the set is not that big a fluke. 1925 fairly wet May (96.5 mm) was followed by driest June on record.
Could go one of a number of way I guess. There is often a significant period of rather unsettled weather in May or June (sometimes nicknamed the June monsoon) - from a personal point of view, hopefully we are getting this out of the way now as June does have the potential to deliver my favourite summertime weather of warm, dry, sunny days without significant humidity.
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Model output discussion - the final third of Autumn
in Forecast Model Discussion
Posted
dont think the 850s are necessarily the key - we had -7s and -8s in the south east last winter but the dewpoint was above 0C so it was rain.
later in the season similar 850s delivered snow as the relatively humidity and thus the dewpoint was lower.
All sorts of little nuances can influence the dew point, but warm ssts around the UK will definitely not help.