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Offline BJBlake  
#241 Posted : 13 January 2019 00:11:34(UTC)
BJBlake

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Location: South west Norfolk 28m ASL

The Town won today against all odds: I'm humming the Great Escape, so if the Town can win, the weather can verify cold - eventually! 

 

Can an anyone remember the roller coaster leading to the Beast? There was plenty of promise, followed by wrist slitting disappointment, followed by renewed optimism. This one is more uncertain true but it's the same roller coaster. 

I don't usually like the mean outputs. But right now they are a sanity check to the inconsistency. I think the UKMO is the one to watch with greater hope.

Brecklands, South Norfolk 28m ASL
Offline tallyho_83  
#242 Posted : 13 January 2019 00:21:13(UTC)
tallyho_83

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Location: Devon

18z ensembles chart  for London: -the OP run was a mild outlier:

 

------------------------------------------------------------

Home Location - Exeter Haven Banks (5m asl)

Winter 2017/18 stats for Exeter from 1st December 2017 - 1st March 2018:

Coldest temp recorded -5.5c (27/28th Feb 2018 - making it the coldest temp recorded since 2012)

Number of mornings with frost 12

Ice day's: 1 (28th Feb 2018)

No of days with snow falling: 6

No of days with snow lying 0

No of days with snow settling 1 (A tiny trace of frozen snowflakes on morning of 12th Feb 2018)

No of days sleet/soft hail fell: 8

No of days with freezing fog: 0.

No of days with frost lasting all day: 0

Warmest daytime max 14.4c 11:30am (25th December 2017)

Lowest pressure recorded (979mb)

Offline Gandalf The White  
#243 Posted : 13 January 2019 00:35:32(UTC)
Gandalf The White

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Originally Posted by: tallyho_83 Go to Quoted Post

18z ensembles chart  for London: -the OP run was a mild outlier:

 

Tally, an outlier is a run without any support amongst the ensemble perturbations. The 18z was not in any way an outlier even towards the end.

Location: South Cambridgeshire

130 metres ASL

52.2N 0.5E

Brexit: proof that you can fool people into making a stupid choice

Offline Arbroath 1320  
#244 Posted : 13 January 2019 00:37:06(UTC)
Arbroath 1320

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Originally Posted by: Gandalf The White Go to Quoted Post

 

Whereas the GFS(P) maintains the theme of a chunk of the polar vortex dropping SSE with a mid-Atlantic ridge building

Roughly how the ECM 12z might have evolved.

 

 

 

Yes and the 18z ens show the op to be in the milder cluster. Still strong signals for cold, but with the Azores High continuing to pose a threat it seems.

GGTTH
Offline Arbroath 1320  
#245 Posted : 13 January 2019 00:39:50(UTC)
Arbroath 1320

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What will tomorrow's runs bring I wonder?

Edited by user 13 January 2019 00:46:55(UTC)  | Reason: Not specified

GGTTH
Offline fairweather  
#246 Posted : 13 January 2019 00:41:57(UTC)
fairweather

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Originally Posted by: jhall Go to Quoted Post

 

We would hardly be looking at late February by next weekend, which will be the 19th of January. Even if the GFS was to show a clear signal at 16 days out - which is unlikely - that would still only just take us into February. And in any case the GFS and ECM ensembles are already showing a pretty clear signal of -5C 850 mb temperatures from about 8 days out, which is not that far from the -7 that you say you want - especially when you bear in mind the point that Retron has made that the low pressure forecast to be over the UK in that timeframe means than that 850 mb level will be substantially closer to the surface than it would usually be. That would pretty much make -5 equivalent to the -7 that you'd like to see.

Maybe not put quite as I meant and late Feb is probably pushing it a bit John. I am saying that the uncertainty that is there now for 8-10 days should be resolved by next weekend if not before. If it isn't showing a consistent cold outlook and the cold isn't with us we will be starting to look at the first week of February onwards. That will be the last month of winter and the later it is the more special it will have to be to justify it as a cold second half to winter that has been widely predicted and more especially so since Christmas with the SSW event.

Whilst I personally think  there is enough evidence that it will be cold I think -5C 850's still might not make for severe cold and settling snow in  the South. I also do think that the mean is likely to fall to -7C though. 

This was and is not meant to be a "winters over" type post in any shape or form, just being a bit more measured. 

Edited by user 13 January 2019 00:45:49(UTC)  | Reason: Not specified

Offline David M Porter  
#247 Posted : 13 January 2019 00:42:16(UTC)
David M Porter

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Originally Posted by: Arbroath 1320 Go to Quoted Post

 

Yes and the 18z ens show the op to be in the milder cluster. Still strong signals for cold, but with the Azores High continuing to pose a threat it seems.

The current situation with the model output reminds me of last February in a lot of ways as there was a lot of variation back then among the various operational runs before the models all came into line wrt the arrival of the Beast. My own feeling is that at the moment, the models are quite possibly still getting fully to grips with the effects in the troposphere of the SSW which took place over the festive season and they may not have this fully worked out yet.

Tomorrow's model runs will make for interesting viewing I suspect.

"Sometimes what we accept as the truth may not be the full story".

Hercule Poirot (David Suchet)

Offline Arbroath 1320  
#248 Posted : 13 January 2019 00:47:58(UTC)
Arbroath 1320

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Originally Posted by: David M Porter Go to Quoted Post

 

The current situation with the model output reminds me of last February in a lot of ways as there was a lot of variation back then among the various operational runs before the models all came into line wrt the arrival of the Beast. My own feeling is that at the moment, the models are quite possibly still getting fully to grips with the effects in the troposphere of the SSW which took place over the festive season and they may not have this fully worked out yet.

Tomorrow's model runs will make for interesting viewing I suspect.

Very likely David.

GGTTH
Offline Retron  
#249 Posted : 13 January 2019 04:42:37(UTC)
Retron

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No great change to the overall outlook yesterday evening, I see! The GFS(P) 18z yet again plastered the UK in snow, it was very consistent yesterday.

The ECM strat charts:

https://www.geo.fu-berli...erdiagnostics/index.html

haven't changed much since Friday either. The SSW is still ongoing and is forecast to end on the 20th - the best part of three weeks after it started. It's shown to affect 30hPa, but 50hPa doesn't quite go negative on this run... the vortex is well and truly split, however.

The ECM ensemble means last night show a decent-sized cluster, perhaps even a majority cluster, for a low pressure, accompanied by a chunk of the polar vortex, to cross the UK. Now, where have we seen that before? Oh yes, the GFS(P)!

As has been mentioned in passing from the NW post, the ECM was a very cold suite last night with the majority cluster on the cold side. You can see this via the 10th/90th percentile charts quite nicely - there's more scatter on the warm side than the cold side:

https://weather.us/forec...emble/euro/temperatur850

With ECM mean maxima for London pretty much matching the GEFS in the 10 day+ time frame, i.e. 2 or 3C, the signals for a noteworthy cold spell are the strongest they've been this winter. Another exciting day of model-watching beckons!

Offline Retron  
#250 Posted : 13 January 2019 06:02:17(UTC)
Retron

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A different parallel this morning, with the "bit of the vortex" heading east instead. Much of Scotland and northern England still gets hammered with snow, but for the southern and SE folks it's a series of slushy coverings instead of one big dump.

It's interesting though that even outside the deep upper low, on the "warm" side of it, it's still cold enough for snow at times.

Offline Steve Murr  
#251 Posted : 13 January 2019 06:45:14(UTC)
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@Retron

ECM brings out the 1995 cold this morning

-20c a risk in Scotland @192- Upper air cold pool developing in situ over England-

Offline Retron  
#252 Posted : 13 January 2019 06:50:21(UTC)
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Originally Posted by: Steve Murr Go to Quoted Post
@Retron
ECM brings out the 1995 cold this morning

-20c a risk in Scotland @192- Upper air cold pool developing in situ over England-

Indeed, a weak ridge and clear skies would lead to some exceptionally cold temperatures. We last saw a -20 in 2010 and as you say there'd be a good chance of the same with that ECM run.

I suspect when we see the T2M ensembles later it'll be one of the coldest, if not the coldest member!

Offline Steve Murr  
#253 Posted : 13 January 2019 06:56:38(UTC)
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Originally Posted by: Retron Go to Quoted Post

 

Indeed, a weak ridge and clear skies would lead to some exceptionally cold temperatures. We last saw a -20 in 2010 and as you say there'd be a good chance of the same with that ECM run.

I suspect when we see the T2M ensembles later it'll be one of the coldest, if not the coldest member!

Also a substantial correction west@216 with the atlantic V the milder 12z 

216 brings more in the way of snow to the UK -

Offline Whether Idle  
#254 Posted : 13 January 2019 07:03:04(UTC)
Whether Idle

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I think the effects of the SSW may be starting to be calibrated a little more effectively by the ECM model as time progresses, with the ECM going for some cold scenarios this morning involving both frost for most and snow (for some). Its been fascinating viewing for days and I don't see that changing.  Nothing is particularly nailed on, but the potential for some stellar charts as the days progress, popping up in FI is there.

Today's offerings from the EC, however, may appear understated, but they are also fairly cold!

With model watching its as much about remembering to forget things as it is forgetting to remember.
Offline Steve Murr  
#255 Posted : 13 January 2019 07:09:10(UTC)
Steve Murr

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Originally Posted by: Whether Idle Go to Quoted Post

I think the effects of the SSW may be starting to be calibrated a little more effectively by the ECM model as time progresses, with the ECM going for some cold scenarios this morning involving both frost for most and snow (for some). Its been fascinating viewing for days and I don't see that changing.  Nothing is particularly nailed on, but the potential for some stellar charts as the days progress, popping up in FI is there.

Today's offerings from the EC, however, may appear understated, but they are also fairly cold!

EC 240 must raise your eyebrow lol 😁

Offline Retron  
#256 Posted : 13 January 2019 07:11:28(UTC)
Retron

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Originally Posted by: Steve Murr Go to Quoted Post

EC 240 must raise your eyebrow lol 😁

TBH I'm stunned by that ECM run - that'd give a cold spell for the record books.

Offline Steve Murr  
#257 Posted : 13 January 2019 07:18:19(UTC)
Steve Murr

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Originally Posted by: Retron Go to Quoted Post

 

TBH I'm stunned by that ECM run - that'd give a cold spell for the record books.

Waiting for EPS - Although looking at the high res Aperge thats to 96 - it builds a similar blocking ridge 

Should be lots of support today !

Offline Solar Cycles  
#258 Posted : 13 January 2019 07:20:27(UTC)
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The ECM the pick of the output thus far today although it’s a predominantly dry set up for many until the end, I have to say though it does look a strange evolution.
Offline Ally Pally Snowman  
#259 Posted : 13 January 2019 07:22:30(UTC)
Ally Pally Snowman

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ECM is on the verge of bonkersness in a good way I don't think I've seen a run quite like it before . The major models are still quite different to each other but most roads still lead to cold and snow.

 

Offline Ally Pally Snowman  
#260 Posted : 13 January 2019 07:27:53(UTC)
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A very decent set of GEFS this morning

 

 

 

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