Model output discussion - 20th Feb onwards

[knocker]

The ECM ops this evening continues the theme of a pattern change by the of next week.

Friday has the HP edging in from the SW but this is quickly supplanted as the depression to the west rushes east and the associated fronts bring wet and windy conditions on Sunday. Liable to some reevaluation of course.

[knocker]

The week according to the GFS

It looks like Tues/Weds may be the worst of the week with the depression tracking south in the eastern North Sea to northern Germany producing quite strong wins in the eastern half of Britain with wintry showers of rain/hail/snow and feeling cold in the wind with temps well below average.

Friday a shortwave develops Scotland and wanders south before HP pushes in from the SW overnight into Saturday. This is a false dawn as a shortwave forms in the western Atlantic and races east, phasing in with a low pressure area to the north and arrives, with associated fronts, on Sunday giving a very inclement day. This is not a million miles away from the scenario from last nights ecm. (slightly different track await today's).

[Polar Maritime]

The GFS this morning tends to keep the cool/cold air over the UK as we head into May, From a slack N/E flow.

ECMWF showed a very similar theme on yesterdays 12z (But not on this mornings run as Knocker points out below!

 

 

Edited April 24, 2016 by Polar Maritime

[knocker]

The ecm somewhat confuses the issue for the weekend and the evolution is considerable different.

Thursday 12z it has HP pushing into the SW with a developing shortwave south of Iceland.

It runs this shortwave SE, via Cornwall, into Biscay by 00z Saturday.

By 06z Sunday HP again into southern England but things are afoot The low pressure to the north of Scotland moves SE and the shortwave developing in the western Atlantic nips in and is a small feature over Cornwall 00z Monday. This quickly moves out of the way and HP is the order of the day Monday. This scenario is much better for the holiday weekend than the GFS.

The 00z chart Monday

[knocker]

Polar you had me going there for a minute. That ecm chart you have posted is yesterdays 12z. I thought I was having another senior moment.

Edited April 24, 2016 by knocker

[Polar Maritime]

22 minutes ago, knocker said:

I thought I was having another senior moment.

Yes Knocker my turn today, Even i thought it was this mornings run, I should remember to finish my coffee before attempting anything in a morning especially after a long day yeasterday.. 

Edited April 24, 2016 by Polar Maritime

[knocker]

The GFS upper air charts 00z 27th with the upper trough neatly aligned down the North Sea. Could be some wintry stuff down the eastern half of Britain.

Edited April 24, 2016 by knocker

[johnholmes]

Little sign on the anomaly charts of any warmth in the next 6-10 days.

[mb018538]

Big differences between gfs and ecm today....ecm collapses heights over the pole and things turn more westerly, gfs maintains more of a block. Very much hoping ecm is on the right track!

[knocker]

1 hour ago, johnholmes said:

Little sign on the anomaly charts of any warmth in the next 6-10 days.

And looking further even, although the upper trough weakens and moves east  backing the winds WNW we are still looking at temps a little below average in general according to the GEFS and EPS.

Edited April 24, 2016 by knocker

[Milhouse]

Once again on the GFS high pressure building from the SW. Usually on these occasions you would get cool winds coming over the top of the high but not so much on this occasion.

 

[knocker]

After a brief flirtation with HP on Friday the GFS is still rushing the fronts trough Sat/Sun

 

[The PIT]

8 hours ago, johnholmes said:

Little sign on the anomaly charts of any warmth in the next 6-10 days.

Interesting perhaps ECM going off on one. As others have said gfs showing plenty of blocking and keeping the general cool theme going.

[Summer Sun]

ECM slowly losing the blocking high again this evening

Temps slowly but surely climbing back closer to average

Edited April 24, 2016 by Summer Sun

[knocker]

The GEFs continuing the transition to an unsettled westerly regime albeit the with the temps very slow to rise to average.

[Milhouse]

Indeed SS. Its a relief to see the cold air gradually dispersing and temperatures returning to more seasonal values to start May.

[ANYWEATHER]

Evening All! Some very Tasty synpotics and some record cold across the nation . Farmers and growers wont be happy with the outlook.....

[knocker]

NOAA and the ecm are on the same page, if not precisely the same, this evening with the transition to a more zonal regime starting in the 5-10 period. A negatively tilted trough and some ridging mid Atlantic Basically a NW upper flow so still unsettled and cool.

In the later period the trough fills somewhat and the flow backs to more WNW with the temps, although gradually rising still remaining a little below average.

[knocker]

The GFS this morning plus the latest take from UKMet fax

Not to dwell too long on this week as as I imagine everyone is aware that we will be in the grip of a cold northerly with temps well below average and the prospect of some very wintry stuff, hail/snow, down to some low levels particularly in the north and east. But what about the weekend.

Early Saturday a small perturbation tracks SE. courtesy of the negatively tilted upper trough to the NE but this is just the hors d''oeuvre as fronts zoom in later that day on quite a strong bringing some wet and quite windy with them.

I'll leave everyone to pick the bones out of the latest fax charts.

 

[knocker]

Well after a quick look at the ecm for the weekend if you can sort out the likely outcome you are better man than I am Gunga Din.

First Friday it makes much more of the small perturbation and has a low Scotland at 12z

It develops a shortwave in it's circulation which it runs into France whilst building a ridge to the west.

This ridge then develops and pushes into the UK Sat/Sun, whilst at the same time zapping the shortwave attempting to zoom in from the west. Thus certainly a drier if cool weekend. I have a feeling this might be more in line with the METO thinking. But who knows, it's all a bit of a dog's breakfast.

Edited April 25, 2016 by knocker

[mb018538]

ECM certainly holds some promise in the 8-10 day range, GFS still a little bit at odds with this and the UKMO thinking. Before that, the bank holiday weekend isn't looking too great....especially so on the GFS run.

[Gibby]

HERE IS MY LATEST ANALYSIS USING DATA SUPPLIED BY THE NWP OUTPUT COVERING 5 OF THE WORLDS MOST POWERFUL WEATHER COMPUTERS ISSUED AT 09:00 ON MONDAY APR 25TH 2016

THE CURRENT GENERAL SITUATION An increasingly cold Northerly airflow is moving down across the UK behind a cold front moving South down across Northern and Eastern regions through today with the cold Northerly lasting for much of this week thereafter before backing Westerly later.

http://www.wetterzentrale.de/pics/Rtavn001.gif

CURRENT SNOW FORECAST AND FREEZING LEVEL OVER THE UK The UK sees very low uppers across the UK throughout this week with the range of the freezing level lying between 1500ft in the North and less than 3000ft in the South. This allows a risk of snowfall in showers at any elevation over 1000ft UK wide through the week.

http://www.snow-forecast.com/maps/dynamic/uk

http://www.natice.noaa.gov/pub/ims/ims_gif/DATA/cursnow.gif

MODELS-2 WEEK HEADLINE Remaining rather cold and showery this week but possibly becoming less cold next week.

THE GFS JET STREAM FORECAST The Jet Stream is streaming South down across the UK today and for much of this week before it backs to more of a West to East flow close to Southern Britain next weekend. In the second week the flow still looks like remaining close to Southern Britain still largely blowing West to East while all the time maintaining an unsettled and cyclonic weather pattern across the UK.

http://www.netweather.tv/index.cgi?action=jetstream

GFS OPERATIONAL The GFS Operational Run today shows a cold and showery Northerly flow blowing down across the UK between High pressure to the West and Low to the East. By the end of the week the Low pressure to the East eases West towards the North of the UK backing the winds more Westerly and removing the very coldest uppers with it but maintaining a very unsettled pattern. Through the second week things have only warmed up marginally on this run with continuing cool and unsettled weather next week with rain at times although any wintriness should become confined to the far North.

GFS CONTROL RUN The theme of the Control Run is very similar to the Operational during the first half of the period with a cold Northerly flow the main feature promoting wintry showers this week with a slow transition towards somewhat less cold weather and at the very end of the period drier conditions too especially across the North and East as on this run as pressure builds over and then to the North and East of the UK. 

http://www.wetterzentrale.de/pics/Rtavn1441.gif

http://www.wetterzentrale.de/pics/Rtavn3841.gif

http://www.meteociel.fr/modeles/gefs_cartes.php?code=0&ech=144&mode=0&carte=0

http://www.meteociel.fr/modeles/gefs_cartes.php?code=0&ech=384&mode=0&carte=0

GFS ENSEMBLE DAY 14 DATA  Still very mixed messages from the Clusters yet again with a mix of Low pressure lying close to the West and SW of the UK just about holding sway as the most likely theme at 14 days although there are plenty of alternative outcomes involving closer proximity to higher pressure scenarios albeit no real signal on location of this or longevity of any one pattern.

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cpre&HH=372&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

UKMO The UKMO model this morning is showing a cold and showery week as Low pressure dominates just to the East of the UK with a Northerly feed down across the UK. By the weekend the pressure gradients slacken across the UK as well as backing more Westerly giving fair and less chilly conditions at the weekend with rain and showers more likely towards the North and West by then than elsewhere. 

http://www.wetterzentrale.de/pics/Rukm1441.gif

THE FAX CHARTS The Fax Charts today show a very complex week of synoptic pressure patterns across the UK as unseasonably cold air floods South across the UK frequently complicated by frequent injections of troughs from the North and later West ensuring unsettled conditions remain for all of the UK up until and probably including the start of the Bank Holiday weekend..

http://www.weathercharts.org/ukmomslp.htm#t120

GEM GEM this morning shows a sustained fairly unsettled period this morning and with cold Northerlies blowing down across the UK this week it will stay cold with rain or wintry showers at times. With time the coldest conditions weaken as winds back Westerly at the weekend but it never looks like becoming anything like warm with next week too looking relatively cool and unsettled under Low pressure over or close by to the UK. 

http://www.wetterzentrale.de/pics/Rgem2401.gif

NAVGEM NAVGEM N/A at time of issue. 

http://www.wetterzentrale.de/pics/Rnvg1681.gif

ECM ECM is the most optimistic model this morning in that while it also shows a cold and showery week to come conditions slowly improve at the Bank Holiday Weekend as the cool and showery theme becomes replaced by less cold and benign conditions especially in the South with improvements continuing next week to include much of the UK as High pressure over Biscay and France builds North across the UK.

http://www.wetterzentrale.de/pics/Recm2401.gif

ECM 10 DAY MEAN (12z) The 240hr mean Chart from last night is continuing the theme of the UK gradually lifting out of the cold spell as slacker pressure gradients with a weak Westerly component looks likely in 10 days time with the best weather then developing over the South with temperatures having recovered somewhat for all.

http://www.wetterzentrale.de/pics/Reem2401.gif

NOTABLE TRENDS & CHANGES FROM PREVIOUS RUNS There is still plenty of evidence that the very coldest conditions shown this week will weaken over the Bank Holiday weekend with a more changeable but less cold mix of options shown between the models thereafter.

31 DAY HISTORICAL VERIFICATION STATS FOR GFS, UKMO & ECM The verification Statistics of GFS, UKMO and ECM show at 24 hours ECM ahead at 99.6 pts with UKMO at 99.5 pts and GFS at 99.3 pts.  At 3 days ECM is leading with 97.3 pts to UKMO's 96.6 pts while GFS lags behind at 95.5 pts. At 5 days ECM leads with 88.9 pts to UKMO at 86.8 pts and GFS at 83.2 pts. Then at 8 Days ECM has the leading spot from GFS with 62.3 pts to 54.5 pts. Finally at Day 10 ECM has the lead from GFS with a score of 44.6 pts to 38.3 pts.

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day1_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day3_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day5_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day8_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day10_PMSL_MSL_G2NHX.png

MY THOUGHTS The models remain constant in showing this week as being nothing less than a cold and in a few places wintry one with rain and showers falling as sleet and snow at times on higher ground and not always just in the North. The winds will be screaming down from the North over the coming days accentuating the cold and while frost at night may not be the biggest problem due to the strength of the wind it is a very real risk where sheltered from the wind. By the weekend changes do look like beginning as the Low pressure to the East transfers towards the North of the UK and as pressure rises to the South winds back to a less cold Westerly. The weather at the weekend is still very undecided with some output suggesting rain and showers continuing although the Euro's look much more sedate as High pressure ridges into the UK from the South restricting the showers to the far North and more importantly it could be that temperatures then approach normal values especially in the South. To my untrained eye there seems little prospect of any sustained warmer period anytime soon as the models which stretch out to longer term periods suggest that Northern High pressure blocking remains a strong possibility as we move into the first half of May and if that verifies it will remain rather on the cool side with rain or showers at times as Low pressure areas take a track that is further South than ideal for the UK. However, this is not a forecast but a generalisation of what the models appear to be showing two weeks from now and it maybe that the better orientated rise of pressure given from both UKMO and ECM from next weekend moves further forward in breaking the rather cool pattern to something much better and May like. Time will tell of course but I would like to see more cohesion between all the output on the conditions for next week and beyond before I feel more confident  in any one solution. More from me tomorrow. 

Next Update Tuesday April 26th 2016 from 09:00

[stodge]

Morning all

No point trying to emulate Martin's usual excellent daily analysis of the output so just a few observations from me.

GFS OP is a horror show for those wanting warmth - northerly blocking and a southerly jet means if it's not raining now it will be soon. Always the prospect though of one of the LPs slowing down and allowing a feed from the S or SE so a glimmer of hope.

ECM OP goes in a very different direction and brings the Azores HP much more into play. A much more settled and warmer output though may not come in time to save the Bank Holiday weekend and, worryingly, keeps getting pushed back.

GEM OP an interesting mix as can be the case - the northerly blocking is there but so is the Azores HP so it's a bit of everything really with some fine spells about also some cooler and wetter periods.

UKMO downgrades the northern blocking more quickly and while the weekend doesn't look settled the winds are coming from the west rather than the north.

One key might be the signal for lowering heights over Europe which allows the Azores HP to ridge north and slows down the movement of LP systems from west to east. ECM does this, GFS doesn't by keeping the stronger jet and the core of LP more over the UK and southern Scandinavia.

 

[Man With Beard]

Excellent posts above but to add a little focus on the "potential" change at around D9: several models now throwing a trough into the Atlantic at this time, cutting off the cold northerly feed. Whether that leads to warm/sunny or cool/showery/westerly is debated:

 

  

Caveats being the usual - big pattern changes in FI often get modified as they move through D7 / D6 / D5, and along those lines, the GFS Parallel demonstrates a quite likely variation with a portion of heights surviving in the mid-Atlantic leading to the following:

 

although interestingly we've reached the seasonal tipping point for easterlies, and the result is increasingly warmer weather:

 

the lesson being, the continuation of northern heights may no longer be such a bad thing for spring weather if the Scandi trough is removed (EAST COAST EXCEPTED!!)

Either way, I do not see the beginning of May being significantly below average, leaving aside the first couple of days.

Edited April 25, 2016 by Man With Beard

[Summer Sun]

We should start and see more of an Atlantic influence by the end of the week nothing special temp wise, but at least we'll cut off the northerly winds get any sunshine it will be pleasant enough

As UKMO shows this afternoon