Model Output Discussion 12z 20/04/13

[Milhouse]

 

The colder uppers start creeping into the UK on the 23rd.

 

http://www.meteociel...1&ech=30&size=2

 

Then its just downhill from there!

 

http://www.meteociel...1&ech=54&size=2

 

http://www.meteociel...1&ech=78&size=2

 

http://www.meteociel...&ech=102&size=2

 

http://www.meteociel...&ech=126&size=2

 

Into FI the NAVGEM and the BOM showing colder than the rest but overall not great.

 

http://www.meteociel...&ech=126&size=2

 

http://www.meteociel...&ech=174&size=2

 

Combined with a cool northerly we'll all be needing our hats and coats on.

 

http://www.meteociel...&ech=102&size=2

 

 

Really really hoping for a definate warm up soon as i'm getting a bit fed up with the cooler weather now!

 

The black line denotes the 0c 850 hpa line. Round about this time of year the average position for it is somewhere between London and the Midlands. On the above charts it never really sinks south of the UK apart from Friday/Saturday. Next week most models show the main bulk of the cold going into the mid Atlantic with warmer air over Europe affacting the south and east of the UK.

[Milhouse]

With uppers almost 10c in the south this week theres only one way and thats down. Doesnt necessarily mean the coats and hats will be coming out again. Fiday and Saturday look chilly admittedly but after that plenty of options remain on the table.

[Carlrg]

With uppers almost 10c in the south this week theres only one way and thats down. Doesnt necessarily mean the coats and hats will be coming out again. Fiday and Saturday look chilly admittedly but after that plenty of options remain on the table.

 

I really hope you're right but i have just been outside and cut the grass and it felt decidedly chilly out there and thats before the cooler uppers and northerly/noreasterly sets in.

Edited April 22, 2013 by Carlrg

[SomeLikeItHot]

The black line denotes the 0c 850 hpa line. Round about this time of year the average position for it is somewhere between London and the Midlands. On the above charts it never really sinks south of the UK apart from Friday/Saturday. Next week most models show the main bulk of the cold going into the mid Atlantic with warmer air over Europe affacting the south and east of the UK.

 

The ECM differs of course. After the warm blip this week, we have cool northerly weather into May. This is expressed by the ECM mean with the 0 deg 850 line moving south of the channel from somewhere between 96-120 hrs and staying there for the remainder of the run.

 

Further more the met office doesn't really believe its getting warm after saturday and sunday with the statement, that

"Most areas will be dry and bright at first this weekend but a band of cloud and rain is expected to move southeastwards across the UK during Saturday and Sunday. Colder, more unsettled weather will follow in behind this band of rain, and it is likely to remain unsettled for much of the rest of April. As a result most areas will see sunny spells and showers, and some of the showers could be heavy with a risk of hail and thunder. It will also be breezy at times. Temperatures are likely to be colder than normal for the time of year with a chance of overnight frosts, especially in rural areas."

 

 

The ecm means from Saturday.

 

 

Nothing as cold as we saw in March but certainly colder than average and much colder than this week.

Edited April 22, 2013 by SomeLikeItHot

[Milhouse]

Lets see what the ECM says tonight. Yesterdays ECM 0z was promising in keeping the main cold away from the UK in the long term and this mornings 0z was an outlier against the ensemble mean for the final frames.

Edited April 22, 2013 by Milhouse

[Andy Bown]

Further more the met office doesn't really believe its getting warm after saturday and sunday with the statement, that

"Most areas will be dry and bright at first this weekend but a band of cloud and rain is expected to move southeastwards across the UK during Saturday and Sunday. Colder, more unsettled weather will follow in behind this band of rain, and it is likely to remain unsettled for much of the rest of April. As a result most areas will see sunny spells and showers, and some of the showers could be heavy with a risk of hail and thunder. It will also be breezy at times. Temperatures are likely to be colder than normal for the time of year with a chance of overnight frosts, especially in rural areas."

Quite a crucial sentence there though as it states

'and it is likely to remain unsettled for much of the rest of April.'

Now, April ends next Tuesday so "much of the rest of April" is only a few days really!

[Summer Sun]

Once again tonight we have consistent hints of a settled period during early May

 

 

Normally I wouldn't have much confidence in this but it is something the met office are going for the low affecting the south isn't mentioned from them so I wouldn't worry about that too much

Edited April 22, 2013 by Gavin.

[Cheshire Freeze]

Once again tonight we have consistent hints of a settled period during early May

 

 

Normally I wouldn't have much confidence in this but it is something the met office are going for the low affecting the south isn't mentioned from them so I wouldn't worry about that too much

Yep and something I think will bare fruit. Back at the end of March and earlier on in April I wrote in the summer thread that May would feature such an occurrence. Personally I crave to see some 'interesting' weather but hey ho!

[Frosty.]

Firstly, I like the new design, it's really nice

The Gfs 12z shows an increasingly warm spell this week over southern and eastern england with temps rising into the low 70's, maybe 23c will be reached in the southeast on thursday but if not, 20-22c will be. There should also be plenty of sunshine in the above locations but rather cloudy at times and more humid, further north and west across england & wales tending to be rather cloudier but with some pleasant sunny spells too, especially to the lee of high ground with temps nearer 14-18c. Scotland and N.ireland look more unsettled througout with showers and more persistent rain and remain within an oceanic airmass, also much windier with swly to wly gales in the far north and northwest but still with sunny spells between the fast moving blustery showers but temps struggling between 8-12c. During thursday a spell of wet weather will spread southeast from scotland across england and wales, reaching the southeast of england overnight into friday and heralding a cooler spell, once the rain clears southeast it will be showery and much cooler, the weekend may not be so bad, a weak ridge should weaken the shower activity on saturday and sunday may also be fine in the south with relatively higher pressure but cool and showery for the n and w, cold enough for a touch of overnight frost. The gfs shows most of next week being rather cold and showery with a light to moderate nwly flow but with sunny spells and the risk of frost continues but eventually the weather trends more settled and gradually warmer with high pressure tending to take control.

Edited April 22, 2013 by Frosty039

[Purga]

A few frost warnings coming up methinks Again throughout FI GFS 12z Even London has some 2m sub 0C nights

Edited April 22, 2013 by Purga

[Cheshire Freeze]

A few frost warnings coming up methinks Again throughout FI GFS 12z Even London has some 2m sub 0C nights

Frost warnings? I've heard it all now!

[Purga]

Frost warnings? I've heard it all now!

Why not? A sudden air or ground frost can be very tricky for growers especially after a warm spell.

[Milhouse]

Chances of high pressure dominating to start May are quite high. However what is unclear is where it will originate from. So at this stage its unclear whether it will be a warm source or a cold source but we are getting to the stage when an easterly is as warm as a westerly (away from the east coast though )

[NeilN]

Chances of high pressure dominating to start May are quite high. However what is unclear is where it will originate from. So at this stage its unclear whether it will be a warm source or a cold source but we are getting to the stage when an easterly is as warm as a westerly (away from the east coast though )

 

Hopefully May will be a winning month! I think we're in for a good run now.

[Summer Sun]

ECM is now going for a weak ridge of high pressure building on Saturday

 

 

Not spectacularly warm but in the sun it should feel pleasant

[Iceni]

Why not? A sudden air or ground frost can be very tricky for growers especially after a warm spell.

 

Right that sounds like another year of no orchard fruit lined up. Last May was appalling and we had no apples, pears, plums or quinces. I'm really getting sick of these so-called springs. A couple of days warm weather brings everything into bloom and then the frosts and cold zaps it all.

[Summer Sun]

ECM is now showing the rise in pressure as we enter May

 

[Milhouse]

Right that sounds like another year of no orchard fruit lined up. Last May was appalling and we had no apples, pears, plums or quinces. I'm really getting sick of these so-called springs. A couple of days warm weather brings everything into bloom and then the frosts and cold zaps it all.

Its not happened yet so do not fear. You can not be sure of these things until nearer the time but it does look like some cold nights nearer the weekend.

 

ECM is out and after 2 cool and possibly showery days on Friday and Saturday we have 2 better days of higher temperatures on Sunday and Monday. Winds veer northerly on Tuesday before an area of high pressure builds from the southwest to raise temperatures and settle things down.

[Frosty.]

The Ecm 12z shows the warmth quicky increasing across the south in the days ahead but a much cooler oceanic air mass across northern britain all week with showers and persistent rain with strong to gale force swly to wly winds in northern and northwestern scotland, trending polar maritime by the end of the week, even in the south it looks much cooler by friday after a spell of rain has cleared southeast followed by showers. A very cool feeling weekend relative to the midweek warmth but with weak ridging, southern britain should have less showers and more sunshine but cold overnight with slight frosts, more in the way of showers for n and w areas, especially for nw britain, turning milder in the southeast early next week on this run.

[NeilN]

Its not happened yet so do not fear. You can not be sure of these things until nearer the time but it does look like some cold nights nearer the weekend.

 

ECM is out and after 2 cool and possibly showery days on Friday and Saturday we have 2 better days of higher temperatures on Sunday and Monday. Winds veer northerly on Tuesday before an area of high pressure builds from the southwest to raise temperatures and settle things down.

 

That's more like it...glad the South West gets some good weather,

[Frosty.]

A more settled look to early next week with pressure rising, just like the met office update promising increasingly fine and warmer weather in early may, this ecm run looks much better than the gfs 12z shows for next week.

[Gibby]

Hi everyone. Here is the report on the midday output from GFS, UKMO, GEM, NAVGEM and ECM for tonight Monday April 22nd 2013.

All models show a mild and muggy Westerly flow with a weak cold front across Southern areas. Through the next 24 hours it is shown to move North over Northern Britain with some patchy light rain in the North later. Brighter skies will develop across Southern Britain with some warm sunshine in places later in the day. The following few days then show a frontal system straddling the middle of the UK , lying West to East somewhere over Northern England. To the North will be cloudy and increasingly wet conditions with the far North staying drier but colder. Southern Britain will stay rather warm with some occasional sunshine and light SW winds. Through Friday the cold front across the North will move South over Southern Britain with rain crossing SE through the day and introducing rather cold and showery conditions to start the weekend for all.

GFS then shows a ridge of High pressure slipping South over the UK on Sunday with some fine and rather cold conditions replacing Saturdays showers though cloud would be moving into the North from the NW later as a new deepening Low pressure East of Iceland slips South down over the UK early in the week with further rather chilly and unsettled conditions over all parts through the week wit heavy showers and sunny intervals with hail and thunder a distinct possibility. Temperatures are shown to slowly recover through the week though as the winds slacken and back Westerly. The end of the run shows High pressure building over the UK with some fine, settled and dry conditions with good spells of sunshine with temperatures still subdued by Day 15.

The GFS Ensembles show that after a few colder days from the weekend the weather warms up steadily and as far as the South is concerned warms up enough to push temperatures above average later in the run. There is a fair amount of dry weather shown too though the cooler phase is accompanied by some unsettled and showery conditions.

The Jet Stream currently blowing over Scotland will meander around over the coming days before digging South to the West of the UK in about a week from now before returning NE over the Low Countries and Northern Europe. The Western end of the flow in the Western Atlantic largely disintegrates at the same time point.

UKMO has a cold North or NE flow on Saturday with scattered showers and sunny spells. A ridge then slips gently South across Southern areas too on Sunday bringing a dry and potentially sunny day in temperatures closer to average or a shade below. Frost at night would be a distinct possibility at the weekend though.

GEM shows a similar weather pattern at the weekend with a gradual deterioration to unsettled and showery conditions as we move into next week.

NAVGEM shows a fine end to the weekend under a ridge of High pressure before it too shows a Low pressure area sinking down over the UK next week with unsettled, showery and rather cool conditions developing early in the week and lasting through to the end of the run.

ECM shows a colder and showery start to the weekend before the same ridge is shown sinking South over the UK as a slender feature on Sunday with a reasonable day with sunny spells and light winds. However, the North won't be fairing as well as Westerly winds around a sinking depression to the North brings some rain across from the West later in the day. Through the early days of the week the weather turns somewhat showery and cool again though much less drastically then recent runs with a quicker end to the cold likely soon after midweek when Low pressure sinks South through the Atlantic cutting off the cold feed and bringing a ridge across the UK from the SW with dry and largely bright days across England and Wales while any rain becomes restricted to the NW. The final frame of the run shows High pressure ridges holding across Southern Britain from both the Baltic States and the SW approaches with any rainfall restricted to the far NW in association with slowly Eastward moving Low pressure areas to the North. Temperatures would recover to near average at this time point.

In Summary tonight I feel slightly encouraged that the cold weather may be just a brief encounter rather than anything more prolonged as the models seem to be softening the influence of the cold North flow quite quickly after it's arrival. The first attack of cold is quickly cut off on Sunday as a ridge slips South while the course of the second Low early next week is far from decided and agreed upon by the models yet meaning the second incursion of cold is equally undecided upon yet. Taking into account the GFS Ensembles look reasonably encouraging towards only the briefest of cold weather and the Met Office mid range outlook sounds favourable the models seem to be leaning towards a more acceptable period of weather than was earlier thought though the risk of frost at night for a time has not been eliminated tonight.

[Frosty.]

Yes this is much better, high pressure next week and more like the met office update compared to the showery and colder gfs run, cool to average temps but feeling pleasantly warm in the strong early may sunshine, a bit more changeable and windier across the north, much as this week.

Edited April 22, 2013 by Frosty039

[johnholmes]

There are signs, not definite at the moment but they are there from the 500mb charts that a change from the blocking type 'cold' northerly flow is going to change by early May. Probably to a fairly slack south of west flow at 500mb with any ridging being way west and not affecting the UK. Little sign either of any ridging either east or SE of the UK.

[johnholmes]

The Ecm 12z shows the warmth quicky increasing across the south in the days ahead but a much cooler oceanic air mass across northern britain all week with showers and persistent rain with strong to gale force swly to wly winds in northern and northwestern scotland, trending polar maritime by the end of the week, even in the south it looks much cooler by friday after a spell of rain has cleared southeast followed by showers. A very cool feeling weekend relative to the midweek warmth but with weak ridging, southern britain should have less showers and more sunshine but cold overnight with slight frosts, more in the way of showers for n and w areas, especially for nw britain, turning milder in the southeast early next week on this run.

The charts are a good way of showing how the model, at height is behaving, and can be used at both short and longer terms predictions.