Model Output Discussion 31/03/14 onwards.

[knocker]

Unless my eyes are deceiving me PM the GFS ens mean for the 7th is a tad different. Not quite so downbeat. Mind we are in Alice land!

Edited April 26, 2014 by knocker

[damianslaw]

A very changeable outlook with major changes taking shape over the northern hemisphere thanks to the weakening of the PV and its shift away from NE Canada allowing robust heights to form over the Greenland region - something we have not seen at any stage so far this year.

 

Where does this leave us? - exposed to a cold northerly attack as we enter May. Both GFS 12z and ECM are showing a notably chilly start to May as we see trough action move across the country into the N Sea and heights residing in situ away to our west and northwest pulling down cold uppers on a cold N/NE wind. UKMO less keen to see a marked sustained colder attack - it is showing heights building over the country after the colder interlude on Thursday/Friday coming preventing renewed trough action from the NW getting a foothold across the country, but the projected heights do look a weak affair and if the GFS and ECM is right the potency of the trough development to our NW in time for bank holiday would have no trouble pushing any height developments aside.

 

I've said many a time that early May sees northerlies reach their yearly maxim i.e. we are more likely to see northerly airstreams now than at any other time of year.

 

In the meantime we have a few more days of rather showery weather but under any sunny breaks it will feel quite warm.

 

The outlook from a synoptic perspective is what many of us cold snow lovers were craving for all winter - alas too late, but quite normal for the time of year - such synoptics are much harder to come by in the Oct-Feb period.

 

 

[bluearmy]

the ops continue to play with the bank holiday depression dropping in whilst the ens mean will obviously fail to pick this up at such a range. ecm remains keenest of all with this feature. the ens spread on ecm 00z seemed to show the favoured path for this system to be passing to our on a track which keeps it to our ne, should it actually verify.

[Summer Sun]

ECM continuing to show a settled spell developing later next week, but once more it shows a breakdown to more unsettled weather for BH Monday

 

 

Friday to Sunday will probably see the coldest conditions overnight how cold it gets in the towns and cities remains to be seen but out in the countryside frosts look inevitable wouldn't be surprised to see some of the the towns and cities getting close to 0c especially in the north

 

The run ends with a return to more unsettled weather on BH Monday and the Tuesday

 

 

GFS ensemble seems to be moving to something more unsettled for BH Monday as well, the ECM ensemble will be interesting later the 00z showed the high lasting through BH Monday we could see the 12z backing off like the GFS has

 

Edited April 26, 2014 by Summer Sun

[Winter Cold]

Yes ECM not following the GFS idea. However it still looks cool and unsettled with a trough coming down to the north and leaving us in a NW flow. This is bank holiday Monday:

 

[IDO]

ECM is a mirror of GEM at T144:

 

ECM:   GEM: 

 

So the negative uppers with the ECM for 3-4 days. 

 

At T192 GEM and ECM still carbon copies:

 

ECM:   GEM: 

 

So the Bank Holiday Saturday heralds 2-3 days of higher pressure from the ECM as well, followed by the trough re-establishing itself by D9 and by D10 and a return to a cooler slack flow, whereas the GFS op is a more active cold spell:

 

ECM at T240:

 

Ties in with my general thoughts that the next few weeks are more likely to be cooler and more unsettled due to the PV's dissolution. Any HP more likely to be transitional.

Edited April 26, 2014 by i'm dreaming of...

[Frosty.]

Tonight's Ecm 12z op run shows colder but drier and brighter weather spreading south later next week with a few showers for more eastern counties blown in on a stiff NE'ly breeze and also a risk of a few heavy showers building inland but next weekend looks fine with pleasant spells of sunshine and lighter winds under anticyclonic conditions but with damaging overnight frosts, it soon turns unsettled again into the following week as the high pulls away to the southwest and a low swings southeast from iceland setting up a cool and cyclonic end to the run with spells of rain interspersed with sunshine and showers. In the meantime, it looks like remaining unsettled until midweek with further rain and showers but with sunny spells too and reasonable temperatures and then improving from the north but with colder uppers (T850 hPa) extending to all areas by next thurs / fri.

Edited April 26, 2014 by Frosty.

[Frank Trough]

Yes the models have been spot on with regard to the coming week, for a slack flow, maybe not as meridional as expected due to the AH keeping the pattern flatter. Cold air, as predicted for a while on the march south, through delayed, but Thursday has been the call for a few runs now, The models then disagree from then.

 

GFS op and control have the ridging equating to an Icelandic high by T144:

 

 http:////d321955.r.worldssl.net/forum/public/style_images/tctc91_simplify/attachicon.gifgfs-0-144.png http:////d321955.r.worldssl.net/forum/public/style_images/tctc91_simplify/attachicon.gifgens-0-1-144.png  http:////d321955.r.worldssl.net/forum/public/style_images/tctc91_simplify/attachicon.gifgfs-1-144.png

 

Perfect winter synoptics with the UK on the cold side of the trough, so by T264 we are still in a cold flow:

 

http:////d321955.r.worldssl.net/forum/public/style_images/tctc91_simplify/attachicon.gifgfs-1-264.png  http:////d321955.r.worldssl.net/forum/public/style_images/tctc91_simplify/attachicon.gifgfs-0-264.png

 

Staying relatively cold till the end of the run, T324: http:////d321955.r.worldssl.net/forum/public/style_images/tctc91_simplify/attachicon.gifgfs-1-324.png

 

However UKMO has the high at T144 over the UK: http:////d321955.r.worldssl.net/forum/public/style_images/tctc91_simplify/attachicon.gifUW144-21.gif

 

And GEM close to the NW coast of Scotland: http:////d321955.r.worldssl.net/forum/public/style_images/tctc91_simplify/attachicon.gifgem-0-144.png

 

They will lead to the trough and associated cold air escaping south further east, into continental Europe.

 

GEM at T240:  http:////d321955.r.worldssl.net/forum/public/style_images/tctc91_simplify/attachicon.gifgem-1-240.png http:////d321955.r.worldssl.net/forum/public/style_images/tctc91_simplify/attachicon.gifgem-0-240.png

 

Looking at the GEFs, by T192 they are all over the place and I also suspect the 12z op is in the coldest 10% of its ensembles.

 

We have had inter model and cross model chopping and changing on this for some time so very uncertain as to what happens after the May Bank Holiday weekend.

 

since when? they've been spot on in downgrading any potent northerly but that has happened gradually. Last week a bitter northerly was supposed to be setting in by monday.

 

I hope the GFS (Guessing Forecast System) has guessed incorrectly in the latter period - although May is now traditionally cold and wet so it'sprobably right. Pointless northerlies.

[Polar Maritime]

since when? they've been spot on in downgrading any potent northerly but that has happened gradually. Last week a bitter northerly was supposed to be setting in by monday.

 

I hope the GFS (Guessing Forecast System) has guessed incorrectly in the latter period - although May is now traditionally cold and wet so it'sprobably right. Pointless northerlies.

 

Well since the models picked up the signal a good 10 days ago, it's safe to say they have done pretty well, As i have said before it's always the timing of which they struggle with especially with Cold Shots once a pattern is picked up where they can toggle between a few days here and there, So nothing unusual. 

 

The GFS is far from a Guessing tool, And no weather is pointless as far as the Models are concerned.

Edited April 26, 2014 by Polar Maritime

[Frosty.]

I agree with polar maritime, the gfs is a good forecasting system :-)

Turning colder later next week.

[knocker]

Well I can't say I agree with everything that has been discussed but that's life. The ECM hasn't much changed it;s tune regarding the weekend but as I've said before the orientation of the high is vital regarding the weather. The basic synoptics are high pressure over the UK (the GFS has a cell to the NE on Monday) and a large area of low pressure in eastern Europe. This will probably lead to a NE/N flow but I wouldn't bet the bank on it at the moment. No sign of any trough.from the north as yet.

Edited April 26, 2014 by knocker

[summer blizzard]

GFS18z is interesting past day 5 keeping high pressure for most of the run.

 

[William of Walworth]

It's all about the exact positioning of the HP for next weekend (Bank Holiday w/e) isn't it? Devil's in the detail.

 

No warmth to be expected most likely ... lack of rain to be welcomed though I suppose!

Edited April 27, 2014 by William of Walworth

[knocker]

Morning snapshot. Forecast max temps for the western US Monday 6th. OOh la la.

 

The discussion on the merits of relative models made me smile a tad. I remember at Dunstable in the late 50s people such as Fred Bushby and Dr. Sawyer et al had a Ferranti Mercury computer run with paper tape whilst developing the METO numerical model. And from that little acorn sprouted veritable oak trees and now the five day forecast is as good as the two day not that many years ago. Comparisons are futile unless supported by an in depth analysis which few are qualified to carry out.

 

Anyway back to sun block in the US.

Edited April 27, 2014 by knocker

[phil nw.]

The colder shot looks quite brief this morning on the 00z runs as pressure rises quite quickly from the sw by the weekend.

The upper trough a little further east as it digs south so only a brief glancing blow for the Uk before it settles down for the BH period.

 

 

Still time for some minor adjustments but the overall trend for a nice BH weekend and into week 2 is very much showing in the Ens means and now in the Op runs. as the Azores High is modeled close to the UK.

 

[knocker]

The woeful ECM is still telling the same story for the weekend with the trough just briefly nudging Scotland en passant. The coldest day may well turn out to be Friday.

 

EDIT

 

Sorry didn't see your post phil. A touch of repetition.

Edited April 27, 2014 by knocker

[IDO]

Well I can't say I agree with everything that has been discussed but that's life. The ECM hasn't much changed it;s tune regarding the weekend but as I've said before the orientation of the high is vital regarding the weather. The basic synoptics are high pressure over the UK (the GFS has a cell to the NE on Monday) and a large area of low pressure in eastern Europe. This will probably lead to a NE/N flow but I wouldn't bet the bank on it at the moment. No sign of any trough.from the north as yet.

 

 

Hi. I notice you say there is no sign of a trough coming from the north yet. I always thought the best way to ID them was at 200 or 300hPa level. For instance this morning's 300hPa chart for the next 10 days:

 

 

I have marked out what I believe to be an upper trough incoming from the north. You seem to know your stuff so I wonder if that is indeed the best chart for such comparison? Thanks in advance.

 

This morning it is less apparent than yesterday's 12z (that at the time I identified as a probable outlier) due to the HP cell coming late this week now being closer to the ECM; upper ridge nearer Iceland on the GFS 12z, now more UK centric:

 

Todays 0z :   Yesterdays 12z: 

 

The colder air flow on the 0z now marries with the other models and the flow is further east meaning we get a shorter burst of cold uppers:

 

The mean 850s at T96 is incoming:   Feeds south and by T132 it nearly covers the UK: 

 

Before slipping east by T180: .

 

Drier run for the three days of the May Bank Holiday as the front sinking south should clear the south by early Friday, followed by a more showery run before higher pressure brings more settled conditions. The control run has also flipped to a more settled medium term. However the GEFS remain split and that period IMO still remains uncertain. The GEFS at T228 highlight this:  http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=228

 

The mean also shows the variation of the GEFS at T228:   op: 

Edited April 27, 2014 by i'm dreaming of...

[Captain Shortwave]

The ECM op is more in line with its ensembles this morning with the Azores high building in on Friday and slowly slipping away south west, but maintaining its influence over most of the UK into the following week. The OP of previous days looks to have been too progressive and extreme with the evolution.

 

GEM looks even more settled

As does the GFS

Its ensembles look not too shabby either.

 

So fingers crossed on a good bank holiday weekend.

[knocker]

Hi. I notice you say there is no sign of a trough coming from the north yet. I always thought the best way to ID them was at 200 or 300hPa level. For instance this morning's 300hPa chart for the next 10 days:

 

I have marked out what I believe to be an upper trough incoming from the north. You seem to know your stuff so I wonder if that is indeed the best chart for such comparison? Thanks in advance.

 

 

Whoa ido I'm a long way from being an expert on this As far as I know you can use other contour heights but usually the 500-mb map is employed by meteorologists because of its importance in revealing the direction of the steering winds, that is, the winds that steer weather systems across the Earth's surface.

 

Regarding the trough I was meaning just for this weekend.

 

Sorry I couldn't have been of more help but JH or TWS will give you a far more professional answer to your question hopefully.

Edited April 27, 2014 by knocker

[IDO]

since when? they've been spot on in downgrading any potent northerly but that has happened gradually. Last week a bitter northerly was supposed to be setting in by monday.

 

I hope the GFS (Guessing Forecast System) has guessed incorrectly in the latter period - although May is now traditionally cold and wet so it'sprobably right. Pointless northerlies.

 

Hi

 

I think you are being a bit hard on GFS. The pattern change can be very difficult to predict but GFS saw it coming around 10 days ago and has run with it since. It has never had great certainty as to timing or where the cold uppers would reach, but it picked out the change and that was what I was complementing it on. I have no access to ECM 15 day charts so cannot qualify whether it was also on the ball.

 

As for GFS seeming flip flopping, yes this is apparent in its op output. But if you look at it's ensemble suite there has never been great confidence past about D6 (acceptable in such a pending setup), so with  its members often split 50-50 then I would be more surprised if the op wasn't flip flopping on a regular basis.

 

As for May the CFS highlights how this pattern change may affect May: 

 

We appear to be on the border of HP to our west and a trough to our east. That of course, being a mean chart may just reflect, like GFS, two camps, one with HP over the UK or one with a trough. Or a battle between the two (more likely). It does look cool though: 

 

[Summer Sun]

ECM appears to have delayed the cold air till Friday now for England and Wales

 

 

The colder air then makes inroads on Friday and Saturday though western Ireland and the far south west may not turn too cold if ECM is right

 

 

By the Sunday milder air spreads over the UK once more and this continues through to the end of its run

 

 

So the cold air is still shown to arrive but its looks like a short snap of 2 days max for England and Wales with some in the far west possibly avoiding the coldest air

 

UKMO continues to show pressure rising so a decent BH weekend could be on the cards feeling pleasant in any sunshine but chilly overnight to start the BH weekend

 

 

As for GFS? well thats looking pretty settled through-out from later next week

 

And finally GEM that also follows the rest but it brings in some warm air later +10 850's for some

 

Edited April 27, 2014 by Summer Sun

[knocker]

The ECM ens. self-explanatory. Of course on May 19th.......................................Must go the Archers has started

Edited April 27, 2014 by knocker

[Captain Shortwave]

Well with the 06z coming out, it is becoming increasingly likely that the bank holiday weekend might be pretty decent, though temperatures looking rather depressed by having a cool airmass overhead. Low teens looks the likely outcome with frosts on Friday and Saturday night.

Saturday might present a rather chilly day for the south east with quite a nagging north easterly and probably some patchy cloud too. Rest of the UK should be fine and Sunday looks fine with sunny spells countrywide. The only other questions will be on Monday and how close fronts get to the north of the UK.

 

As for the week ahead, looks showery for the first half before rain pushes south in the later half of the week. Temperatures close or a little above average but becoming cooler from the north and possibly cold enough in the North on Thursday for wintry showers even to low levels, though the 850s mix out by Friday. So for those in the north who like the wintry stuff, Thursday looks your best bet.

[IDO]

Comparing the 0z ECM temp mean with this morning's GFS 0z suggests the latter is an outlier compared to ECM ens: 

 

D13 GFS op run is about 12c higher than the ECM mean!

 

It was at the top end in its own ensemble as well (NW): 

 

So probably an unlikely scenario and best ignored till sustained support.

 

The 06z Control looks to tie in closer with the ECM and the flip of the 06z op.

 

At T240 the Control:    Mean: 

 

At T288 on the Control another northerly blast: 

 

At T288 only four other members support the GFS 06z op for a MLB over the UK. From the London ens 850s the op is clearly at the top end of its members (in FI) and the control, the bottom end:

 

 

The majority of the suite are more similar to the control run (though not as cold). However it is the 06z run so I am not going to call a trend yet.

 

 

 

 

[The PIT]

GFS hinting at a colder spell but as it heads towards the reliable time frame the downgrades are already in full swing. I wouldn't be surprised by the time we get to Wednesday the cold spell will have become plain average which seems to be the constant theme this year. UKMO also indicates at cool down from the north at the present time.