Model Output Discussion 12z 20/04/13

[Polar Maritime]

You investing in a time machine, Frosty? I thought it could only be resolved as-and-when it either happens or doesn't happen, as Pete said.

 

Recent model output hasn't budged wrt thundery breakdown (or absence of); there is no change there. Sensing some subtle maneuvering away from original assessment. Hmmmm.

But as it's the mod discussion, frosty said in his earlyer post that (with a little human input) he "feels" there could be convective activity... the models are there to predict the weather and they chop and change untill they resolve.

[Frosty.]

But as it's the mod discussion, frosty said in his earlyer post that (with a little human input) he "feels" there could be convective activity... the models are there to predict the weather and they chop and change untill they resolve.

cheers mate, 

 

there has been some chop and change with the models, especially with the 12z and now we have a yawning gap opening up between the gfs and the ecm in particular, there are likely to be a few more twists and turns before we get solid cross model agreement during the first half of next week, hoping the ecm is on the money and the fine warm spell can be prolonged as long as possible.

Edited April 20, 2013 by Frosty039

[Purga]

Interesting opportunities for some frosty nights and maybe snow for northern areas at the weekend

 

 

 

 

 

A cold pattern setting up for May?

 

 

could there be some snow for parts in May? That would be quite something as favoured areas would have had snow every month since October if it materialises!

Edited April 20, 2013 by Purga

[Frosty.]

The 00z models are all in agreement that most of the uk will have a three day pleasantly warm and fine spell with lots of strong late april sunshine and light winds, only the far northwest of the uk missing out and remaining breezier, cooler and more changeable. It will be warming up through the week and the midweek period will be the warmest with temps nudging into the 70's towards the southeast, london will probably have some of the warmest temps in the week ahead but most areas will reach the low to mid 60's for a time. Friday looks like being the day of change with pressure falling across all parts of the uk and cool, unsettled weather pushing down from the north with a rather cold and showery weekend to follow. Friday will probably bring a band of rain southeastwards but perhaps some heavy showers will develop before the front arrives in the south, the ukmo 00z shows a trough forming next friday across england with cold and showery weather with ne'ly winds for next weekend with a trough to the east in control. So, monday will be a getting better kind of day, tues/wed/thurs look fine, warm and sunny or at least bright, then unsettled and much cooler to end the week. The Gfs 00z later in FI shows a nice anticyclonic spell and then goes for high pressure retrogression with a cold plunge heading for norway through early may.

Edited April 21, 2013 by Frosty039

[IDO]

Although the GFS 0z op run (from D7) is more settled than of late, it looks like it is an outlier. It has High pressure close to the UK from late next weekend till the end of FI:

Still a cool MLB, but relatively settled. However the GEFS pressure charts suggest only low support, compared to the mean:

The GEFS mean remains supportive of a mid-Atlantic ridge and a UK trough, although the pattern is more flat than recent output, suggesting changes may be afoot:

ECM at T216 remains under the influence of a UK trough:

Last night's ECM ensembles start to split at the end of next weekend (a la GFS op run synoptic) :

So lower confidence on whether the trough remains in situ for long, probably due to the Atlantic high unable to move north, blocked by the Greenland PV piece,and therefore trying to push east. It fails on the first attempt with ECM (possible second shot around D10), but succeeds with the GFS op, though not with the GFS mean.

The south-east looking good for 2-3 days of mild weather this week (Tuesday-Thursday):

Further north, feeling a lot cooler.

Edited April 21, 2013 by i'm dreaming of...

[AWD]

Looking at the latest NAE for Monday, it looks a rather cloudy affair nationwide, although favoured areas will no doubt get something a little sunnier;

With temps into the low teens;

The GFS then goes on to show a sunnier day on Tuesday with the cloudcover breaking up;

Before returning more somewhat, especially over the South of the UK into Wednesday and Thursday;

Most areas should see some sunny periods over the 3 day period at some point, but equally a period of more cloudy conditions looks likely for most at some point too.

This also represented well by the week ahead forecast from the Met Office for my location;

[Purga]

A simple question. What is the likelihood of a repeat of last year's May? Will it be warm enough for the fruit blossom, bees etd. to come out only to be cut down by frost?

 

My freezer's nearly empty of everything I managed to grow last year and the year before as there was no fruit harvest at all in 2012.

It looks from the models and the way that the METO updates are worded that there is a chance of a cooler / colder pattern developing after the relatively warm period we are in now. So quite a strong possibility of frosts occurring which, I guess, won't be helpful to growers. It could have been better if the cold had persisted throughout April and then gone away until the end of summer rather than blowing hot & cold. The weather will do what it will despite what any of us wish for.

Edited April 21, 2013 by Purga

[Gibby]

Hi there. Here is the morning outlook from the midnight outputs from GFS, UKMO, GEM, NAVGEM and ECM for today Sunday April 21st 2013.

All models currently show a cold front moving steadily SE over the UK through today followed by a somewhat showery Westerly flow in the north tonight. Tomorrow a warm front crosses East over the UK introducing rain and drizzle along with hill fog and more humid conditions to all areas by the end of the day. Through Tuesday and Wednesday a moist and warm SW flow lies over many areas with some warm sunny intervals developing to the lee of high ground across Southern England where it will become rather warm. More Northern and Western areas North of the Midlands will be more sustained overcast with occasional rain at times through the midweek period. Then later in the week and before the weekend a change to rather colder weather develops from the North as Low pressure drifts down to the NE setting up a Northerly flow with a mix of sunshine and heavy showers to end the week.

GFS then shows the weekend a showery and rather chilly one before a ridge topples down from the NW cutting off the cold and showery theme by Sunday. The new week then looks like steadily becoming more settled again as High pressure builds it's way NE over the UK with pleasantly warm and dry weather with sunny spells and light winds for nearly all regions. As the High intensifies further later in FI the pressure gradient steepens over the UK with an Easterly feed bringing cool weather to the South, especially near Eastern coasts. the NW however, lying closest to the High just off NW Scotland would see the best of the dry and sunny weather where it could become quite warm in the afternoons for a time.

The GFS Ensembles are in comfortable agreement of a warm snap this week in the South followed by a colder snap next weekend before a steady build of temperatures to near the late April-early May average sets up. After some showery precipitation from the cooler phase a lot of fine weather looks like being shared by all.

The Jet Stream shows the flow streaming over the Atlantic and the UK for some considerable time now weakening as we start the week after next.

UKMO today shows slack Low pressure over the UK on Friday drifting off to the East on Saturday with a chilly and showery weather pattern the most likely scenario for the UK over the weekend.

GEM has a more direct Northerly feed over the UK at the weekend enhanced by further disturbances running down from the NW keeping the rather cold and showery theme going with some longer spells of rain at times too.

NAVGEM today too has a showery North flow for a time next weekend before a ridge slips South over the UK followed by a new area of Low pressure close to the North of Scotland by Day 7 with rain and showers moving SE to all areas through Day 7.

ECM shows a complex structure of innitially Northerly winds early next weekend with showers. A ridge moving SE later dampens the showers down before a new area of low pressure becomes complex over and then to the north of the UK with cool and unstable air over the UK from the NW bringing further spells of rain and showers to all.right out to Day 10.

In Summary this week looks Ok for the South with a spell of pleasantly warm and humid weather towards midweek while the North keeps cloud and more unsettled conditions going. Later in the week pressure falls over the UK and low pressure slides SE either over or to the East of Britain bringing a change to rather colder conditions with heavy showers and sunny spells. GEM and ECM show some more coherent bands of rain later in the weekend and start to the following week in association with renewed low pressure from the NW whereas GFS wants to bring the UK under High pressure again later in it's output which could be shared by ECM beyond it's output as pressure is shown to be recovering from the SW at Day 10. In essence although the deep cold of recent output has mellowed somewhat there would still be a risk of frost for a time next weekend should skies be clear overnight but it does now look that this will be a shorter risk than was originally shown.

Edited April 21, 2013 by Gibby

[Summer Sun]

The ENS shows a rise in pressure for early May nicely this morning

 

[DR(S)NO]

The 00z models are all in agreement that most of the uk will have a three day pleasantly warm and fine spell with lots of strong late april sunshine and light winds, only the far northwest of the uk missing out and remaining breezier, cooler and more changeable. It will be warming up through the week and the midweek period will be the warmest with temps nudging into the 70's towards the southeast, london will probably have some of the warmest temps in the week ahead but most areas will reach the low to mid 60's for a time. Friday looks like being the day of change with pressure falling across all parts of the uk and cool, unsettled weather pushing down from the north with a rather cold and showery weekend to follow. Friday will probably bring a band of rain southeastwards but perhaps some heavy showers will develop before the front arrives in the south, the ukmo 00z shows a trough forming next friday across england with cold and showery weather with ne'ly winds for next weekend with a trough to the east in control. So, monday will be a getting better kind of day, tues/wed/thurs look fine, warm and sunny or at least bright, then unsettled and much cooler to end the week. The Gfs 00z later in FI shows a nice anticyclonic spell and then goes for high pressure retrogression with a cold plunge heading for norway through early may.

Hi Frosty,I'm probably reading these charts wrong,but I really can't see most areas here in the low to mid 60s?

In fact many areas look as though they will struggle to get into the low double figs. And with the continuing nagging wind I would say its going to be a cool feel to the week.

[Frosty.]

The latest Ecm 00z ensemble mean is painting a very unsettled and cool picture once we get through to next weekend and the following week out to T+240 hours and beyond with a persistent slow moving trough dominating our weather for several days beyond the warmish settled weather in the coming days, the upcoming fine spell has been extended by an extra day or so. The Gefs 00z mean also look cool and unsettled at T+168 hours.

 

As for today, sunny towards the southeast but slowly clouding over as time goes on, this recent satellite image shows the lovely clear skies with just thin high cloud at the moment but further north and west it is turning more cloudy and a band of rain will slowly move east but by the time it reaches the southeast later, only a little rain will be left, tomorrow it's an improving story but temps only around average but pleasantly warmer and sunnier by tuesday onwards and wed/thurs also look fine and pleasantly warm but cooler and more unsettled to the northwest, the south could become rather humid later in the week with perhaps some thundery showers on friday as pressure falls.

Edited April 21, 2013 by Frosty039

[Frosty.]

Hi Frosty,I'm probably reading these charts wrong,but I really can't see most areas here in the low to mid 60s?

In fact many areas look as though they will struggle to get into the low double figs. And with the continuing nagging wind I would say its going to be a cool feel to the week.

image.jpgimage.jpgimage.jpgimage.jpg

a lot will depend on sunshine amounts, synoptically the charts look good until the end of the working week but cloud amounts will determine which areas reach the low to mid 60's and low 70's, the further southeast across the uk looks warmest and sunniest and to the lee of high ground further north and east, the west and northwest probably cloudier and therefore cooler.

[mushymanrob]

not looked at the models much, but this mornings expected cool spell (end of the week) isnt as as severe as previously expected, at this rate itll amount to nothing much at all..  to me the outlook is pretty normal for the time of the year, some nice warmth, some cooler interludes... no sign of anything extreme, be it heat, cold, wind, rain...

[nitro_deluxe]

Aye, usual Spring like weather with few if any surprises.Hard to believe we're almost into May!

[IDO]

The 06z GFS op has trended more towards the 0z mean (and ECM op) with a failed attempt next weekend for a high to push east. The 06z shows the UK under trough conditions till past D10 before a transient Atlantic ridge, breaks the trough:

Messy from there. This run is more in keeping with yesterdays runs.

That said, I am not confident of this morning's ECM op. The run seems to be an a worse case scenario after D5/6:

Rainfall totals for the op at the top end (London ensembles):

The 2m temp ensembles: A slow recovery of temps from D10-15, around +5c on the mean.

Still no high confidence from D7, either inter model or inter run and still no sign of a sustained warm up, UK or Euro wise, even by the end FI:

....7th May

Edited April 21, 2013 by i'm dreaming of...

[Frosty.]

The Gfs 06z just doesn't want to let go of winter, arctic air covering the uk at times with night frosts and some potent showers, next weekend looks very showery across the uk mainland as sunny starts give way to afternoon and evening heavy slow moving showers with hail and thunder and wintry for northern hills and cold enough for snow showers across the scottish mountains. As for the reliable timeframe, the warmth is confined to southern england and the southeast with temps reaching 17-19c, much cooler to the north and west with more cloud but cloud breaks to the east of high ground further north would boost the temps into the low 60's but the weather goes downhill everywhere from thursday onwards. The recent frosts have done a lot of damage to spring growth and there could be more frosts to come through late april into early may.

Edited April 21, 2013 by Frosty039

[Frosty.]

The latest met office update shows colder and more showery weather spreading south into next weekend once the milder air and a band of rain has cleared away southeast, a cold and showery weekend with sunshine but with a lot of showers developing and some will be heavy and thundery with hail and with snow on hills and possibly a few flakes of wet snow in the heaviest showers as temperatures drop like a stone as the showers push through, pleasant sunshine at times though with temperatures up and down, cold enough at night for slight air frosts and icy patches where late showers have occured, thereafter it remains cool with scattered showers and night frosts, most of the showers becoming more confined to northwest britain towards the end of the month and as we go into may, becoming more settled and milder with the risk of frost then diminishing, this would tie in with the gfs 06z in FI with drier air spreading from the east.

[Frosty.]

The Gfs 12z looks a little bit warmer in the week ahead for the southeast of the uk, midweek shows 21c across southeast england and 17-19c for a large area to the north and west of london, say a line from north wales across to humberside, southwards where temps could be on the warm side and feeling rather warm in any prolonged sunny spells, the best of the sunshine towards the southeast. It's a different story for the north and west though with a more cloud and some patchy rain with temps struggling in the low teens celsius, much cooler than that over most of scotland with temps really struggling to get even close to 10c in some areas only 6-8c, windier and more unsettled across nw scotland and occasionally further south and east. On thursday, a band of persistent rain spreads southeast across england and wales and the warmer temps become restricted to the far south and southeast, following the rainband the skies become a lot brighter but then showers start to increase across the northwest of the uk, the rainband dragging it's heels across the southeast on friday and showers then spreading down across most areas, on this run, the weekend looks less showery due to more influence from an atlantic ridge toppling southeast but showers then becoming more frequent across the northwest. Early the following week shows a cool cyclonic pattern with showers and longer spells of rain, the driest and brightest weather across the south and temps around average following a cool weekend with slight frosts, the trough then fills and pressure rises slightly with a drier and milder spell before a deepening trough over southern ireland becomes the dominant feature in FI with wet spells spreading across the uk. There are hints of a more settled easterly type pattern later in FI but the trough to the west proves to be a nuicance for most areas on this run.

Edited April 21, 2013 by Frosty039

[Frosty.]

The Ukmo 12z shows next weekend will be a very showery and rather cold few days, much more showery than the gfs 12z shows, the main reason being that the atlantic ridge is further west on the ukmo and the uk would be in a colder arctic sourced airmass with widespread overnight frosts and icy patches, and with the strong late april sunshine acting as the trigger for heavy showers with hail and thunder to develop within the cold unstable airflow and cold enough for snow on northern hills, less of a ne'ly influence on this run though compared to the ukmo 00z.

Edited April 21, 2013 by Frosty039

[Frosty.]

Well, the Ecm 12z builds the atlantic ridge southeast across the uk next saturday, much as the gfs 12z so it's the ukmo which is the most showery outcome. Looking at thursday, the ecm shows a trough forming as pressure falls and with the air ahead of the front still being rather warm and humid, that could spark some heavy showers which would then merge with the more persistent rain spreading down from the northwest, so it could become very wet across the south later on thursday and well into friday before the colder air chases the mild air away, but then a half decent weekend with a lot of fine weather but much cooler than earlier in the week with overnight frosts.

[Summer Sun]

So after a warm week in the south we see a change on Friday as high pressure looses its grip on the UK it will feel pleasant in the sunshine but under any showers it will feel cooler than of late

 

 

Saturday see's a weak ridge of high pressure building so dry and settled for most

 

 

Into Sunday the high gets pushed away with a north westerly flow setting up with temperatures lower than of late

 

 

T192 sees the floodgates open from the north

 

Edited April 21, 2013 by Gavin.

[phil nw.]

In spite of the Euro heights getting quite close to S.England during the coming week it looks like the UK will be divided in two with somewhat colder air further north and fronts straddling the country.

The latest fax for Weds shows this

the warmer air to the south will give some pleasant weather here with some sunshine and temps into the high teens for a couple of days around midweek.

Further north and west there will be probably a lot of cloud about perhaps with some light showers on west facing coasts and hills and feeling somewhat cooler.

Towards next weekend that upper trough digs south across the UK with a mid-Atlantic high developing turning winds towards the north west.

Cooler and showery conditions then spreading south and this setup looks like taking us into the start of May according the mean outputs.

Checking the Ens graph rainfall amounts are still forecasted to be quite low over the next few weeks.

Longer term there are signs of temps.on the rise again as the trough starts to fill.

[Summer Sun]

FI in ECM has -8 uppers pushing down as the floodgates from the north open up

 

 

May opens up with high pressure pushing up from the south

 

 

Thankfully this is FI so the chances of it happening are low

Edited April 21, 2013 by Gavin.

[Gibby]

Hi folks. Here is tonight's report on the 12 noon output of GFS, UKMO, GEM, NAVGEM and ECM for today Sunday April 21st 2013.

All models show a Westerly flow over the UK for the coming two or three days. Tonight's very weak cold front will clear the SE followed by a warm front tomorrow which will affect mostly northern regions with a spell of rain while the South sees low cloud and drizzle along with some hill fog by later tomorrow. Over the following few days the more humid weather behind the front across the South will become quite warm as the sun burns through the cloud in more SE areas midweek with some very pleasant weather here for a time. In the North there will be a huge contrast developing as cold and unsettled conditions here intensify later in the week and spread South to all areas by Friday with cold Northerly winds and heavy, thundery showers, wintry on northern hills becoming widespread and lasting into the weekend.

GFS then shows a new Low moving SE over Scotland at the end of the weekend and start to the new week with further rather cool conditions and showery weather prevailing for the UK. Through the week the cold modifies and temperatures recover to nearer to average as Low pressure becomes more prominent to the west of the UK with a Southerly flow developing. Through to the end of the run the Low remains close enough to the UK to influence the weather, especially in the South and West where further showers or rain at times continues with the driest weather developing more towards the North of the UK.

The GFS Ensembles show the warmer patch of weather through the middle of the coming week is replaced by uppers closer to normal, just below at first and just above late in the run. Rain is most prevalent soon after the cool down at the end of the coming week with the second week looking quite dry for some.

The Jet Stream shows a continuation of the undulating flow over or in the vicinity of the British Isles for the time being before it becomes much calmer late in the forecast period.

UKMO shows a cold but slack Northerly flow over the UK with the mix of sunshine and showers, some heavy with thunderstorms in places. Hail and snow are also a possibility (the snow mostly on the hills of the North) along with frost at night next weekend.

GEM shows a cold Northerly flow too next weekend with showers. A ridge slips SE late in the weekend as a forerunner to new Low pressure early next week with more unsettled and rather chilly weather to come.

NAVGEM shows a rather chillier and unsettled spell next weekend with showers or rain at times before a NW flow develops at the end of the run with rain at times.

ECM shows a very dispiriting set of charts for farmers and growers and will hope there are some changes through the week as it looks like there will be two phases of cold and strong North winds and wintry showers with hail and thunder and night time frosts, firstly early next weekend and once more after a brief respite by Tuesday of the second week.

In Summary the weather looks like encountering two phases over the coming two weeks. There will be a spell of milder weather and indeed possibly quite warm conditions in the South midweek while the North turns colder from Wednesday extending to all areas by Friday. Thereafter, it's a case of waiting and seeing how long the cold spell lasts before any change to milder weather takes hold, something that with all the High Latitude Blocking there is by next weekend may take some time to develop as it looks like most of the early warmth is for Eastern Europe at that moment.

[Frosty.]

Running this sequence of charts from the Ecm 12z operational, quite a colourful run and it would be unusual to see the 510 dam line so close to the north of the uk at the end of april, just shows how unusually cold the arctic has been over the winter and continues to be very cold well into spring but this run is not the favoured outcome looking further ahead, more likely for milder and drier weather to spread in from the east as we go into may with quite a big warm up further east over europe taking place.

Edited April 21, 2013 by Frosty039