Model Output Discussion 31/03/14 onwards.

[Frosty.]

There could be some snow and frosts later in the month if we do pull down a prolonged strong Northerly from the Arctic with 528 dam, it would be a real shame if the pattern was too far west, I think it will be gradually adjusted eastwards..this would be the longest wait for a wintry spell in living memory. :-)

[Captain Shortwave]

There could be some snow and frosts later in the month if we do pull down a prolonged strong Northerly from the Arctic with 528 dam, it would be a real shame if the pattern was too far west, I think it will be gradually adjusted eastwards..this would be the longest wait for a wintry spell in living memory. :-)

Taking a look at the 850s, I suspect to get snow in the upcoming weeks would involve the earth being hit by a meteor. Struggling to get 850s below -12C over the north pole, let alone anywhere near us. 

Edited May 10, 2014 by Captain shortwave

[knocker]

Yes they would only appear to be a couple of degrees below average with the ECM ens.

 

[William of Walworth]

Too much writing off of the whole of May going on here on the most recent models IMO. I'm watching this space VERY cautiously. Chances remain for more changes in details and positioning. 

[Captain Shortwave]

The GEM is first to place the trough far enough west to bring much warmer weather for the UK.

850s of up to 14C in this plume, temperatures would reach the mid/high 20s if this was pulled off. Still the unlikely solution but shows what a relatively small correction does.

 

GFS still going for retrogression

 

GFS still the most progressive with this and has the trough the furthest east.

Edit - ECM also further west

Certainly drier and warmer than previous runs.

Edited May 11, 2014 by Captain shortwave

[IDO]

^^^ Yes GEM going with a different synoptic. The AH arriving mid week doesn't retrogress, it continues towards Scandi/NE:

 

T156:   T240 (Scandi High):

 

GFS op retrogresses quickly to the Atlantic/Greenland:

 

T156:    T240: 

 

Around D10 the op gets messy with HP and LP interacting close to the UK. The Control keeps it similar to yesterday's runs (also like ECM):

 

 

The London ENS suggests the op may be too progressive with the return to higher pressure, however this is a very fluid period so I would not rule out anything:

 

 

ECM now reverts closer to GEM with the AH ridging to Scandi and the trough slides in behind:

 

T144:   T168:  

 

The flatter solutions from yesterday are now vacated and we have a more amplified pattern in our locale, however variance remains as to how we get there. The GFS being the colder medium term scenario. Their D10 mean is supportive of a retrogressing high leading to a UK trough:

 

 

ECM has flipped from yesterday. T192 today:   T216 yesterday: 

 

Trough further west, a weak affair that is easily cut off by the Atlantic ridge and by T216:

 

   T240: 

 

We have a mishmash of pressure close to the UK. Lots of uncertainty but it does look like no long term settled spell on the horizon and any unsettled spell also looks relatively transient. A typical seasonal mixed bag maybe the call.

Edited May 11, 2014 by i'm dreaming of...

[bluearmy]

The 00z runs stretching the westward envelope on the trough as i mused yesterday. At least we now have some doubt on the feature though, given the consistency of ops and ens mean up until these runs came out, i wouldnt be planning any barbecues for next mon/tues just yet! Infact, the end result could just be a less cold unsettled spell than looked likely up until this morning. More swings likely on this yet.

[knocker]

A brief summary of the GFS for the weekend.

 

On Saturday high mid Atlantic bringing NW/N winds to UK and a generally dry day. And this is the last day under the influence of the HP.

 

By Sunday the low over Scandinavia has the UK under it’s influence again with NW winds and generally dry. Monday and Tuesday very much the same story but troughs moving north/south across the UK making both days pretty miserable.

 

It may be worth noting Thursday and Friday as these will be the hottest days of the week by a country mile with temps in much of England in the upper 60s and low 70s. Perhaps even mid 70s in places.

 

Worth a closer look at the 500mb anomaly from yesterdays 18z and todays 00z.

 The 18z had a strong pool of warmer air over NE Europe and the eastern seaboard of the States with a strong pool of colder air plonked over the UK. By the 25^th the warmer, although weaker is dominating from Russia to America with a weak ridge in mid Atlantic.

 

On the 00z run the analysis is identical for 00z Tuesday at least showing some consistency which gives greater confidence to the surface analysis.

 

 

[knocker]

The ECM is going with a slightly different scenario with the upper Scandinavian ridge developing more into the UK. This pushes the low pressure further west.

 

[William of Walworth]

 More swings likely on this yet.

That's what I'm thinking too. Smallish shifts in position and detail van alter UK surface conditions significantly. There've already been a fair few modelling shifts over the last few days and there'll be more. Later in May = all still to play for IMO.

[Gibby]

HERE IS THE LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM TODAY SUNDAY 11TH MAY 2014.

 

THE CURRENT GENERAL SITUATION. Low pressure over the North Sea will fill slowly as well as move slowly away NE. A broad showery trough will continue to lie across Northern Britain with a weakening but currently strong Westerly flow over the South.

 

GFS The GFS Ensemble pack today show that after the improvements of later this week the weather slides downhill again, most likely from the North with a showery and cool flow giving way to Low pressure across the UK with rain at times with subdued temperatures, a trend that lasts some while before the clarity of what happens after that become diffuse and less clear cut.

 

UKMO UKMO shows High pressure declining across Southern Britain next Saturday with fine and dry weather here while Northern parts are cloudier and more unsettled with some rain. This rain looks like it would edge down across the UK later next weekend as High pressure continues it's decline.

 

GEM The GEM operational also shows pressure falling slowly next weekend following the improvements of the week. However, it shows the resulting Low pressure much more to the west today which 'could' result in better weather hanging on more in Northern and Eastern areas while any rain becomes most likely towards the South and West instead of a general UK wide event.

 

NAVGEM NAVGEM shows the pattern as before with Low pressure removing the High pressure over the South next weekend bringing a return to rain and showers to most parts from the NW by Sunday.

 

ECM this morning is somewhat different with the Low pressure moving down from the NW as before but on a more Westerly trajectory bringing unsettled and wet conditions to the South and West for a time while Northern and Eastern parts largely escape from the most unsettled period though it could become chilly and cool as winds switch to the East. There are then signs of pressure recovering again towards the end of this morning's operational run with a showery slack flow in humid weather likely should this morning's run verify.

 

MY THOUGHTS  There are small but subtle differences in the evolution of the outputs as we enter the weekend and following week. Though most output continue to show Low pressure of some sort returning down from the NW over next weekend the track of the Low is far from settled with some output including ECM holding a cell further West which could keep Northern and Eastern parts rather drier than originally thought while the South and West become most at risk of rain and all areas becoming under a more Easterly flow for a time. Longer term no strong trends are shown today with most long term output suggesting slack pressure around the UK indicative of no strong signals to one weather type or another.

[IDO]

ECM mean this morning in line with yesterdays 12z.

 

At T192: 

 

Support for the GEFS solution of a retrogressing high and a trough more east based than the ECM op.

[Summer Sun]

A closer look at the UK from the ECM Op shows pressure remaining quite high for the east throughout this morning, no ensemble support yet but the settled spell didn't get support for a few days if its still on tonight's 12z its got a chance if its gone then it was probably a rouge run

 

 

day 10 sees a rise in pressure for most of England and Wales

 

[Captain Shortwave]

I do get the feeling that the GFS evolution is too clean and simple, this also reflected in the ensembles that again might be making this too clean. I have a suspicion that we will end up in a southerly flow in week 2, how warm it might be depends on how far west the trough is. Close to the low it will be pretty average temperature wise, if it continues to move west then it could become very warm.

Worth noting the UKMO would possibly show the same thing going beyond day 6. Out of the operationals, the GFS is very much on its own.

Edited May 11, 2014 by Captain shortwave

[shaky]

I do get the feeling that the GFS evolution is too clean and simple, this also reflected in the ensembles that again might be making this too clean. I have a suspicion that we will end up in a southerly flow in week 2, how warm it might be depends on how far west the trough is. Close to the low it will be pretty average temperature wise, if it continues to move west then it could become very warm.Worth noting the UKMO would possibly show the same thing going beyond day 6. Out of the operationals, the GFS is very much on its own.

yup ukmo and ecm much closer together!!and its been like that for the past 48 hours!!not to say gfs is wrong though!!

[knocker]

On the evidence of the ECM EPS can'r see it getting that warm with the upper ridge not progressing that far west. The jet is also looping south

Edited May 11, 2014 by knocker

[IDO]

Its easy to see how much the ECM op was an outlier for placement of the Euro ridge.

 

The op has it more west based, D10: 

 

Mean is further east with the ridge at D10: 

 

The De Bilt D9 & D10 show how the op is a total outlier compared to the mean:  

 

D9 & D10 temps about 10c above the mean 2m temp. We can discount the ECM op run on that basis, and go with its mean for the time being.

[bluearmy]

Fair point ID although note the control also looks warm. As i posted earlier, we are stretching the envelope to encompass possible solutions - as of 1 hour ago, the op was certainly outlier potential re southwestward placement of the trough. would you stake much on the same being the case this time tomorrow? Until the direction of travel changes,(or at least halts for a couple of runs) i would remain cautious on this trough placement.

[Cloud 10]

Looking at the ensemble mean's for day 8 from gfs,ecm and the gem,the gfs has the trough

furthest east while the gem has it furthest west with the ecm in the middle.

 

gfs. ecm. 

 

gem.

Edited May 11, 2014 by Cloud 10

[Thundery wintry showers]

There is a lot of uncertainty over how far west the low will track, but in my experience the low often does get revised a bit further west nearer the time so I don't expect us to be hit full-on by the northerly plunge.  I envisage us ending up with a cyclonic south to south-westerly flow on the eastern flank of the low (though not particularly warm, as it will be like an arctic maritime version of returning polar maritime air) and then maybe a brief easterly as the low slips SE, although more lows are likely to follow behind from the west as we head into the last week of May.

Edited May 11, 2014 by Thundery wintry showers

[Summer Sun]

GFS brings the breakdown in quicker than UKMO this afternoon away from NW Scotland where cloud and possibly some rain will be more of a feature UKMO gives another warm day for many

 

 

 

UKMO the better chart if you want the warmth to continue for the start of the weekend, looking like the first spell of BBQ weather for many is just days away now

Edited May 11, 2014 by Summer Sun

[Captain Shortwave]

UKMO looks OK to me, looks like the trough will drop west of the UK, though it does look a little flatter than the ECM/GEM this morning so maybe some rain for the north west and a more south westerly flow, but I suspect next weekend would be pretty decent for England and Wales based off that. GFS in my view looks rather lost.

GEM still calling Scandi high in a weeks time

Rain trying to get into the west of the UK.

 

Interesting to see the GEM pull another end of run plume event

Only another 9 days until it verifies 

Edited May 11, 2014 by Captain shortwave

[Milhouse]

Heading down to Wembley for the FA Cup final on Saturday i know which one i would want to verify. The UKMO would bring a very pleasant start to the weekend with low 20s achievable in the SE. We'll have to see if the ECM also agrees with this.

[IDO]

Heading down to Wembley for the FA Cup final on Saturday i know which one i would want to verify. The UKMO would bring a very pleasant start to the weekend with low 20s achievable in the SE. We'll have to see if the ECM also agrees with this.

 

 

The GFS mean at T144 is less progressive than the op and control:

 

 

 

So looks good for the south all Saturday.

[IDO]

GFS have the UK under an upper mean trough from about T156 to T288:

 

 

 

Good consistency for the timing and duration of this upcoming unsettled spell from around D7. This supersedes the 3-4 days of higher pressure from mid week. Friday should be the warmest (>20c) day.

 

The LP stalls in the trough over the UK and fills from week 2; so pretty miserable. The London ens rainfall highlights this:

 

 

From D13 the trend is to build pressure from the S/SW/SE dependent on the cluster so by T300 the GFS mean: 

 

The GEM solution of the AH continuing to build a Scandi High rather than full retrogression has about three member (being generous) support in the GEFS. So not convinced with that solution (yet).

 

The GFS mean is pretty compelling with regard to the timing & location of the UK trough, so will see if ECM sticks to its guns tonight...

Edited May 11, 2014 by i'm dreaming of...