Model Output Discussion 12z 03/04/13

[Paul]

Just a reminder - if your post contains a few random charts which you're posting because they back up your preference for a certain weather type with no other reasoning or thought process then that doesn't really constitute model discussion and needs to go in to the model banter thread:

A few of the overnight posts have been moved in there..

[Frosty.]

According to the Gfs 00z operational run, winter goes on and on and on, temps remain below average for most of the run across the southern half of the uk, and very much on the cold side for the north, especially scotland with no sign of a warm up until beyond T+300 hours, the gfs run ends with a few lovely charts but there is lots of cold, below average temps up to then and sometimes windy which will just increase the chill factor, at least there is a lot of anticyclonic weather in FI but the high is mostly in the wrong place, the scandi high would feed a lot of low cloud across a very cold north sea with only the far west and northwest being sheltered enough to have some sunshine. So, for northern britain, it would remain cold with frosts and occasional wintry showers with snow on hills, for the south, becoming more unsettled with spells of rain but temps struggling to get much higher than 11c and sometimes not even reaching double figures with frosts returning once the trough clears away to the southeast by next weekend.

At least this weekend will be fine with light winds and feeling pleasant in the sun but with frosts overnight and in the far north there will be outbreaks of rain, sleet and snow.

Edited April 6, 2013 by Frosty039

[IDO]

ECM this morning still keen to bring the anomalous warmth to the south of the UK at D8-D10:

GFS at the moment keeping across the Channel:

Although the control run is keener:

The GEFS suggest a battle between the Atlantic and the Euro high with no clear signal for a prolonged wet or warmth from any members:

But cold members, as expected, on the wain. So mid-next week proper Spring weather (more so for the south) and the possibility of a teaser for summer.

[mushymanrob]

enjoy the sun today and for some, tomorrow. the easterly has dropped and its looking pretty good for the afternoons.

but the working week ahead is looking a right mess, with the wind and cloud returning, however the wind will be southeasterly as opposed to northeasterly. milder weather should win by thursday, but earlier in the southwest. the price to pay is rain and cloud. all this is brought about by a trough digging in from the atlantic. it is currently expected to drift across us, but by friday the models and runs dont appear to have much clue as to what might lie ahead. theres no agreement from the anomaly charts so theres nothing to be gained from those.

so what we might get beyond t144 is anyones guess. the ecm still suggests an easterly, the gfs does eventually but with a totally different evolution and position.

the only thing that there is in agreement is that we lose, at last, the very cold uppers and whilst the ecm suggests pretty warm uppers, thatll be no good really IF theres persistent cloud. winters gone, replaced by 'below average'. so past t144 is pure speculation atm.

Edited April 6, 2013 by mushymanrob

[Gibby]

Good morning. From a very sunny West Country here is the report on the 00z output from GFS, UKMO, GEM,ECM and for the first time NAVGEM for today Saturday April 6th 2013.

All models show a small area of High pressure drifting slowly East over the UK finally cutting off the cold feed from the SE and maintaining largely fine and dry conditions with sunny spells and frosty nights and sunny days through the weekend. A weak trough near northern Scotland will give rise to rain and hill snow here while the South and West become windy and cloudier later tomorrow as milder Atlantic air tries to move up against the cold block over the UK. Through the first half of the next working week the majority of output holds the progress of this milder and wetter weather to the South and West with a more substantial push NE after midweek.

GFS then takes Low pressure across the centre of England soon after midweek and on into the North Sea with rain and hill snow in the North clearing to rather cold and somewhat showery weather with the return of night frosts under clear skies at the end of the week. Then the trend from the operational is for more settled conditions to develop as High pressure to develop close to northern Britain. As shown the result at the surface would be for the best weather to be in the North while the South would develop a nagging East wind while not as cold as recently would feel chilly. Low pressure to the South could encourage occasional rain to extend North into the South at times too before High pressure wins out for all by the end of the run with warmer and sunnier conditions for all in light winds.

The GFS Ensembles show a period of more normal April conditions on the way as uppers recover to normal and Low pressure rolls in from the west next week. Temperatures at the surface will be more subdued, especially in the north next week before all areas look like becoming rather milder in the second phase of the run.

The Jet Stream shows the slow progresssion North of the flow continues though it is very slow for the next 4-5 days before accelerating to a more acceptable position in relation to the UK late next week and beyond as it looks like ridging north to Greenland then and breaking up over Europe.

UKMO for the end of next week looks quite unsettled with Low pressure having crossed the centre of the UK with rain or showers for all. the end of the week then shows a weak NW flow over the UK with sunshine and April showers, heaviest and still possibly wintry on northern hills and frost at night should skies clear.

GEM shows a showery NW flow too to end the week before after a few days a mobile westerly pattern develops as a deep low crosses to the north sending wind and rain East across the UK in average temperatures.

NAVGEM too develops a cool NW flow later next week behind the exiting UK depression with a cold and showery feed for a time before pressure builds from the South to show the end of the run with the UK under more settled conditions with frost at night still a risk but some decently bright pleasant days.

ECM today quickly replaces the unsettled conditions at the end of the week into something much more like Spring as high pressure builds quickly over the South with pleasant and potentially rather warm conditions developing towards the end of the weekend and into the following week, especially in the South and East.

In Summary a more unsettled period is on the way with rain or showers extending slowly North and East to eventually all areas and still cold enough for some hill snow in the North. The unsettled spell should not last long though with most models showing High pressure developing later in the output. The problem this morning is where will that high settle as at this time of year it's position is paramount to what weather is experienced at ground level. ECM produces an ideal scenario for a taste of Spring in the South whereas if it settles too far North, despite warmer uppers it is not necessarily good news if an Easterly feed is allowed to develop as GFS shows to some degree for a time. At least the Scandinavian beast shown by last night's ECM operational has been dropped for now.

[Summer Sun]

ECM is an absolute cracker this morning its following its ensemble run to a degree from last night (see page 12) in developing a warm south westerly feed

The pattern changes at t240 but still warm in the south

[Frosty.]

The Ecm 00z brings a real taste of spring warmth compared to the dismal, cool/cold Gfs 00z, just a flick through the T850 hPA charts shows how we emerge from winter into glorious spring but the transition is messy and low pressure dominated, the track of the low holds the key, the gfs keeps the north cold throughout but the ecm eventually bathes the whole of the uk in very mild air and in the south and east, warm or very warm air for a time.

[SP1986]

Another set of runs where the warmth stays out in the unreliable timeframe, of course it (or something similar) has to arise sometime in the future. This morning all model up to 144 hours are showing the extension of cool, possibly wet, and in the case of the UKMO, GEM and NAVGEM, wintry weather potential also in the form of sleet/hail/snow showers from N/NW.

As yet Spring is looming large, but it's looming too far away.

The 6z GFS basically keeps northern areas (north of roughly Birmingham) in a similar state to now, except with more cloud and rain/sleet.. generally cold by day and night with temperatures failing to reach double figures, the south however fairs a little better with temperature reaching double figures, maybe the seasonal average for a very short time.

I'd consider the outlook to be fairly similar to what I'd expect on an average February day, so by that token, we're still really looking at a wintry outlook.

Edited April 6, 2013 by SP1986

[Duane S.]

I haven't really been looking at the weather charts for a good few days but looking through them this morning, the general evolution that was showing up a week ago of (an already occurring) 1)Ebbing away from the severe cold to cool to a 2)Unsettled period through to 3)A more settled and warm set up is still very much still on. Winter is finally leaving us and whilst it may not go down a classic as a whole, the anomalously cold March/early April spell will be remembered for a long time to come. I'm doubt I will ever see snow falling on the water in Portland harbour in April again!

[Frosty.]

Wintry weather digs it's heels in yet again next week in the north on the Gfs 06z operational, nothing remotely springlike for the north of the uk next week with frosts, wintry showers and a risk of snow, mainly on hills but becoming a little milder in the south but nothing to shout about although it does then become very briefly much milder and very windy with gale force ssely winds across all areas but then we are back to lighter winds and below average or average temps at best, the Ecm 00z is far superior in terms of a much warmer and settled trend in FI, the gfs runs so far today are mixed and generally much cooler than the ecm. Next week will become very unsettled and cyclonic, cold to the north of the low but trending milder further south but still disappointingly below where it should be as we approach mid april.

[Summer Sun]

GFS 06z brings winds up from the south for next weekend

And then it decides to end with a northerly

Of course this is the 06z run so tonight it will have something completely different no doubt

Edited April 6, 2013 by Gavin.

[Captain Shortwave]

There seems to be quite a lot of support in the longer range models for a build in pressure just to our east during the middle part of the month. CFS/JMA longer range models building pressure similar to the ECM ens over the last few runs. There seems to be some signs of the weather turning drier and warmer in the latter half of April after a rather brief return to unsettled conditions.

GFS is calling a flatter zonal type pattern but still milder than of late.

Edited April 6, 2013 by Captain shortwave

[reef]

GFS 06z brings winds up from the south for next weekend

And then it decides to end with a northerly

Of course this is the 06z run so tonight it will have something completely different no doubt

The milder weather seems to have been stuck in the 8-10 day range for weeks now. Just a look at the temperatures in my backyard on the GFS 06z shows we wouldnt hit double figures until next Saturday now - 7 days away.

The difference between the models in the T+96 - T+120 range at the moment is the strength of the Greenland high. The ECM has this as more of a weaker surface high which allows the mid-Atlantic trough to move north-eastwards into the GIN corridor and as a result the Azores high to strengthen and send moist south-westerlies in our direction. The GFS is completely different in the same timeframe, as that stronger Greenland high deflects the jet and low pressure systems along a more southerly W-E track, giving cooler, wetter weather to the UK with temperatures generally remaining average or below.

Until the models resolve the strength of the Greenland high (they arent too great at this), then we'll continue to see the carrot on a stick scenario we've been in for weeks now.

[Frosty.]

The latest met office update going for a cold and unsettled week in the north of the uk, much as the gfs 6z shows and for the south it also looks unsettled but with temps trending towards average, once the trough fills and pushes away southeast it looks like pressure will rise strongly across the uk with a fine spell but for the n and w, the fine spell looks brief before atlantic lows begin to target northern britain during FI, the warmest, driest and brightest conditions tending to be across the southern half of the uk and more so towards the southeast. So, yet another wintry week for scotland with wintry showers and also a risk of more persistent sleet and snow, mainly for higher ground but rain at low levels, further south it looks like starting chilly but a milder second half of the week, colder air may briefly push south again if the filling trough slides southeast in around a weeks time before high pressure takes control.

[Guest pjl20101]

The GFS seems like a classic pub run to my books, you have to ask yourself has it verified? Not very often and the ECM have been closer to the mark. I would be very surprised if the weather took the GFS route to be honest, however it does seem though that the MJO isn't playing ball as well for warmth as we would like it to be currently. However it will give something better than what we have had and we cannot ignore that. Oh and the CFS on the CPC NOAA site have removed the trough scenario situation to the south and pushed it back towards the Atlantic.

[Frosty.]

The GEFS 06z mean shows a trough well in charge at T+120 hours, the far north in the cold and showery ENEly flow with overnight frosts and also rather cold for the rest of northern britain with rain at times for lowland areas but a wintry mix on higher hills with night frosts where skies clear, central and southern britain less cold and trending towards average with more of an atlantic flow and spells of rain. The Ecm 00z ensemble mean shows the main body of the trough further west at T+120 compared to the gefs but by 24 hours later it's adjusted further east, the ecm ens mean then goes on to show a rise in pressure to the southeast with low pressure anchored out to the west/nw with an increasingly warm SSW'ly airflow developing further into FI, it becomes warm and settled for the southeastern quarter of the uk but rather more unsettled for the north and west, especially the northwest, the gefs is not really onboard with the warmer settled spell although it does show a trend towards a NW-SE split beyond next week so I think the chances of a warmer and more settled spell (duration unknown) will eventually occur in at least southern britain and especially for east anglia, lincs and the southeast by week 2, the north and west of the uk will probably be generally unsettled during that period but with temps closer to average which means it should turn significantly milder across northern britain after next week.

Edited April 6, 2013 by Frosty039

[Zenarcher]

For the rest of the weekend it will stay mostly cloudy with showers likely across Southern Ireland and South Western England also wintry showers are likely over the Scottish Highlands. The wind will be calm although the South West of Ireland will be breezy that will change to gale force later on Sunday afternoon. Temperatures still staying on the cold side.

Monday and Tuesday next week continue the cloudy theme with anywhere at the risk of some showers around. Wintry showers may continue over Northern parts of the UK. A strong Easterly light gale will cover most of the UK and Western parts may touch gale force. Temperatures continuing to still look cold.

As we look further out to Wednesday it does look rather unsettled with heavy rain over Ireland and England and gale force winds over Scotland as a low pressure system makes its way through. Temperatures still staying cold but some places will notice a temperature increase as the low makes its way through. The GFS, ECM and UKMO don't fully agree on how much rain or wind it may bring at the moment but it is something to keep a watch on as confidence begins to grow on the likely hood.

Edited April 6, 2013 by weathermaster

[Summer Sun]

Wet and windier weather remains likely by Wednesday

Rain for most with some snow on the high ground of Scotland

Looking like GFS is going to stick to the 06z run and develop a southerly wind later next weekend

GFS and UKMO at t144 are taking different routes

And here comes the short lived southerly

Edited April 6, 2013 by Gavin.

[Summer Sun]

ECM and UKMO are pretty much in agreement now at t120 GFS looks like its pushing the low through slightly too quick

[Summer Sun]

ECM is keeping up its warm south westerly tonight

Getting better a t216 I couldn't have put in high in a better place my self just about inch perfect

At least we've lost the easterly Idea it had last night lots of sunshine and warmth on offer for around mid month

Edited April 6, 2013 by Gavin.

[Guest pjl20101]

ECM is keeping up its warm south westerly tonight

Getting better a t216 I couldn't have put in high in a better place my self just about inch perfect

At least we've lost the easterly Idea it had last night lots of sunshine and warmth on offer for around mid month

It would be nice if it came off Gavin, my small concern would be the AO which seems to have downgraded its prediction and could hinder more warmth being reached.

[Captain Shortwave]

Very typical of spring high pressure cells, we get an initial peak of temperatures before they fall away to more average values as we pull in a cooler easterly source as heights fully establish to the north east

But another run with an amplified set-up resulting in a large build of high pressure just to the east of us. It's exact positioning is too far away to worry about and we might see very warm runs and cooler runs. But there is a definite trend for a block to form over Central/Northern Europe which is good for giving more springlike and more importantly dry conditions.

[Frosty.]

Blink or miss it mild settled blip on Ecm 12z tonight followed by colder air from eastern europe fed in by a scandi high but for next week it will be turning unsettled and temps recovering close to average in the south but persistent cold for northern britain, the northern half of scotland looks cold all next week with wintry showers and even some persistent sleet and wet snow is possible at times with widespread frosts, so winter continuing in the far north for another week or so and then briefly milder. The main story next week though is the rain and quite a lot of it as low pressure dominates all week, then becoming more settled.

[Gibby]

Hi folks. Here is the report from the 12z outputs from GFS, UKMO, GEM, NAVGEM and ECM for tonight Saturday April 6th 2013.

All models show a ridge of High pressure settled over the UK currently with a weak trough over Scotland bringing some rain and snow to the far North. Light winds for all will be replaced tomorrow by a freshening SE breeze as Low pressure and an attendant area of milder air behind a trough moves slowly NE into the SW late tomorrow and more especially on Monday. Through the early week cold SE winds will bring rain at times but it will not reach more Northern areas until Tuesday when the models show a more defined Low pressure area moving into Southern Britain with attendant wind, rain and slightly higher temperatures. The North could see some of the rain fall as snow on the hills in the North. Later in the week all models show the Low exiting the UK to the East with a slack and rather cool and showery NW flow over the UK for a time.

GFS then shows a ridge of High pressure building NE across Southern areas on Friday and out into the North Sea on Saturday with a light to moderate SE flow developing over the UK in temperatures fairly close to average. The wind then freshens to strong with rain sweeping in from the South and SW giving several days of wet and windy weather. Then it becomes slowly more settled and calmer as a slack area of high pressure moves across the South developing stronger later as temperatures slowly rise.

The GFS Ensembles show a stuttering warm up over the coming 4 to 5 days with some appreciable rainfall for a time as the depression crosses. Thereafter things settle into a milder setup all round with some dry spells and just occasional rainfall.

The Jet Stream tonight shows the slow Northward movement of the flow though it still remains further South than it should be for this time of year through the period.

UKMO has Low pressure slowly moving away over the North Sea leaving a rather cool and showery west or NW flow over the nation with the risk of frost returning overnight at the end of the week.

GEM has a stronger NW flow with showers following the depression after midweek with a ridge slowly building from the SW at the end.

NAVGEM shows a similar evolution moving forward to bring a ridge up from the SW in a week's time with milder weather for all but some cloud, wind and rain reaching the NW over the weekend.

ECM tonight shows the Low moving away late in the week with a rapid rise of pressure from the South turning into a Denmark anticyclone tonight with an East to SE flow over the UK, quite brisk in the South probably making it feel rather chilly. It should be bright with some sunshine but the risk of low cloud and low temperatures would exist for Eastern Coasts south of the Humber.

In Summary after an unsettled and rather chilly week to come it looks like High pressure will be back on the scene by next weekend. The position of the High varies from model to model and run to run but there are some options which could bring us into favourably warm Spring conditions but if the High ends too far North then the North Sea haar will win the day for many.

[Guest pjl20101]

The current CPC 8-14 day output is still very persistent to have a +ve signal to the se of Britain. Notice the LP has started to come back to Ireland and I am not too worried now, but not looking as good as yesterday:

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

However if we look at this broadly its still a massive improvement on what we have had.

Oh and cheers martin for that as well.

Edited April 6, 2013 by pjl20101