Model Output Discussion 12z 20/04/13

[Frosty.]

So, we have the gfs, navgem and gem showing a cool and showery outlook for early next week (potentially persisting all next week with a nw/se aligned jet) which rather goes against the warmer and more settled met office update covering the start of may, the ecm 12z is more promising for the southern half of the uk next week with high pressure ridging northeast but scotland and n.ireland again having a raw deal with a windier, cooler oceanic air mass with rain and showers, in other words, the ecm 12z would be very similar to this week but rather cooler across the south of the uk with an ongoing risk of ground frosts or slight air frosts under the settled conditions further south but pleasant sunshine, the sun is now almost as strong as it is in mid august.

Edited April 22, 2013 by Frosty039

[SP1986]

It certainly does look after a pleasant few days some cool-very cool weather coming in from north.. certainly the 18z does not entertain any suggestion of a warm up at all, keeping the temperatures significantly below average (nationwide maximum temperature average for the 7 days following Friday around 9-12C, which would be approx 4-6C below average depending on where you are in the country). It does seem that northern blocking is likely to play a huge part in our weather this year, it's so prevalent more-so than I've seen in my lifetime thus far, and so you have to ask what are the chances of a pattern change?

Edited April 22, 2013 by SP1986

[Frosty.]

The south and southeast warming up to 19-20c for the next 3 days and feeling humid but it also looks rather cloudy at times but with the strong late april sunshine punching some holes in the cloud sheet , some parts of the southeast will have prolonged sunshine from time to time and the temps could rise to 21c 70f but if it remains rather cloudy, 19c would be the max. Much cooler by friday after a band of rain has cleared southeast but then showers developing and also spreading down from the northwest, saturday starting showery but then improving as an atlantic ridge topples southeast. For the rest of england and wales it's similar to the above but temperatures trending lower the further north and west you are.

 

Scotland and N.ireland are in a different weather type completely with much more unsettled and windier conditions with blustery showers and more persistent rain spreading northeast at times with occasional swly to wly gales, also a much cooler oceanic air mass compared to the tropical maritime flow for the south of the uk, however, the north of the uk will have some sunny weather too during the coming days so not a complete washout, a cool and showery day on friday is followed by a cool and showery weekend with a polar maritime flow.

 

The Gfs 00z shows a cool and cyclonic pattern next week with complex troughs over the uk bringing sunshine and showers type weather and temps well below average with frost overnight where skies clear, later in FI warms up a little but then it becomes cool and anticyclonic with overnight frosts.

 

The Ukmo 00z is more promising at T+144 hours with milder/warmer air and drier weather with higher pressure encroaching into the southeast but cool and showery to the northwest with a trough in control.

Edited April 23, 2013 by Frosty039

[Gibby]

Good morning. Here is the report on the midnight runs of GFS, UKMO, GEM, NAVGEM and ECM for today Tuesday April 23rd 2013.

All models show a Westerly flow over the UK. This will feel warm and humid in the South but much cooler over Northern Scotland with the boundary marked by a front which will wave over northern England in the coming 48-72 hours. Southern parts will therefore be bright with some warm sunny spells, especially in the SE while Central regions close to the front see rain at times and Northernmost areas stay colder and more showery. This weather type is then shown to accelerate South on Thursday night leaving all areas in a cold and showery couple of days with frost developing at night, especially Saturday night as all models show a ridge of High pressure slipping South across the North, settling over Southern Britain on Sunday.

GFS then starts the new week with Low pressure slipping South down over the UK with showers or spells of rain in moderate to fresh cyclonic winds, making it feel rather cold. Through FI this Low pressure fills in situ only slowly continuing to affect the UK weather for some considerable time with heavy showers in places. Eventually High pressure wins the day forming to the NW of Scotland with a NE flow over the UK. This would lead to a very cold and misty East Coast with low cloud streaming a long way West across Southern Britain bringing cold and grey conditions. There will be a trend for it to burn back towards the east each day but given North sea temperatures are so cold it could prove reluctant to clear at times. The NW would see the brightest and warmest weather in light winds.

The GFS Ensembles show a chilly phase following the next few warm days in the South before things slowly recover to near or slightly above average. The operational was a warm outlier in the South towards the end which would not be reflected at the surface in a NE feed. the North conversely is colder in it's later stages which also would not be a reflection at the surface by day as clear skies and strong sunshine would make for pleasant conditions here. Rainfall amounts in general are generally quite small.

The Jet Stream shows the flow slowly weakening as it crosses the Atlantic and the UK in the coming days eventually sinking SE to the West of the UK and returning NE over NW Europe later next week.

UKMO for the start of next week has the UK in a 'Col' area between Low pressure North and South of the UK with High pressure to the West and East. In these situations any type of weather is possible though with a stronger high pressure influence on this occasion many areas could start next week dry away from the North where some rain is likely from the deep Low to the North.

GEM today brings steadily more unsettled conditions into the South of the UK as we move through next week as Low pressure moves slowly North from the South with rain at times and average temperatures while the NW become dry and bright closest to a ridge to the NW.

NAVGEM shows the Low pressure shown to the North on other output sliding down the North Sea early next week which would help maintain cold and showery weather with wintry showers on Northern hills and clear skies inland at night leading to further frosts.

ECM Not available at time of printing.

In Summary today the weather still looks like turning rather cold, at least for a time as we move into the weekend and start to next week. With a set of charts containing complex and rather slack synoptic patterns over and around the UK next week the longer term prospects remain somewhat unclear but it does look as though somewhat warmer conditions could develop with the risk of showers remaining, maybe more so in the South while the risk of frosts gradually subside as we move deeper into next week.

[Frosty.]

Well it's looking like turning into a rather cold and showery spell next week according to the Ecm 00z with a N'ly to NW'ly airflow with a mixture of sunshine and heavy showers with hail and thunder, merging at times to give longer spells of rain, temps look below average and cold nights with slight frosts, however, it's a gradually improving picture for the second half of next week with high pressure building and becoming fine with longer sunny periods with daytime temps starting to recover but cold and frosty nights which would do yet more damage for gardeners and growers, we have general model agreement that next week will be rather cold and showery, the gfs 00z is actually considerably worse than the ecm shows for next week. As for this weekend, starting showery but becoming drier and brighter as an atlantic ridge topples southeast over the uk, but followed by more low pressure into nw scotland, pressure starting to rise to the southeast by early next week but then a cold, showery spell for all, at least for a time.

Edited April 23, 2013 by Frosty039

[SomeLikeItHot]

ECM cool from 72hrs on - with two northern bursts of cold. at +72-96 and 168-192. only a brief incursion of +ve uppers at +144 into the east and if its coming across the north sea it will be cool at the surface.

 

Some slightly warmer air seeping in at the very end of the run.

 

Cold compared with the next few days, but very mild compared to a month ago!

 

 

 

 

Edited April 23, 2013 by SomeLikeItHot

[Carlrg]

Looks like the cold northerly only lasts a day.

 

http://www.meteociel.fr/cartes_obs/comp_panel.php?mode=0&ech=78&size=2

 

 

 

It has waned and turned into a slightly warmer norwesterly.

 

http://www.meteociel.fr/cartes_obs/comp_panel.php?mode=0&ech=102&size=2

Edited April 23, 2013 by Carlrg

[Frosty.]

I really like the look of the GFS 06z further into FI with the weather becoming very blocked and anticyclonic across all areas, temps slowly recovering after the cold showery first half of next week with high pressure building from midweek onwards, actually, the gfs 06z looks very similar to the ecm 00z next week with the cold showery weather eventually giving way to a nice rise in pressure, if the ecm had gone beyond T+240 hours I can imagine it following the same type of pattern to the 6z towards a prolonged settled outlook. The nights would be cold enough for frosts initially but as we go further into may, the risk of damaging frosts subsides and minima remains in low single digits celsius. So in summary, the models are showing a warming trend for southern and eastern england, the 6z shows 21-22c is possible but progressively cooler further to the north and west of the warm zone, scotland and n.ireland in a more disturbed and cooler oceanic airflow this week, the temperature contrasts are huge between scotland and southern england, especially tomorrow and thursday but by friday there is negligable difference from north to south as we will all be in a much cooler airflow by then. The weekend starts cool and showery but then becomes fine as the atlantic ridge topples southeastwards but with overnight frosts, then from early next week, a deep trough to the northwest of scotland will call the shots for a few days as it drifts east to the north of the uk dragging cold arctic air down it's western flank with sunshine and heavy showers with hail and thunder, then slowly becoming sunnier and drier but cool for a while before daytime temps return to average.

[Summer Sun]

The met office continue to go for warmer conditions arriving as we move to the first full week of May but the ECM monthly ensemble still says no to this with temperatures staying below normal for most of the month

 

 

Rainfall also stays at or below average for most of the run which is stark contrast to 12 months ago

 

 

GFS once again shows high pressure starting to become established as we move through the opening days of May

 

http://www.null/ds/gfs.htm

[Frosty.]

Firstly, just look at this recent satellite image showing the lovely clear skies and unbroken sunshine across the south & east

 

The latest ecm 00z ensemble mean and gefs 06z mean are showing a rather cold and unsettled start to next week and this persists through to midweek but notice how the trough then retreats further and further northeast towards northeast europe with pressure rising across the uk, so this is a lot like the latest met office update with a relatively cold and unsettled spell for most of next week with sunshine and showers, some heavy and thundery with wintry ppn on northern hills and overnight frosts but then a gradual change to more anticyclonic weather and slowly becoming warmer with temps recovering close to average and feeling pleasantly warm in the strong early may sunshine but chilly nights.

 

Tomorrow looks generally cloudier than today but warm in the southeast with sunny intervals. wet, windy and much cooler across n.ireland and scotland but brighter later.

[Frank Trough]

The met office continue to go for warmer conditions arriving as we move to the first full week of May but the ECM monthly ensemble still says no to this with temperatures staying below normal for most of the month

 

 

Rainfall also stays at or below average for most of the run which is stark contrast to 12 months ago

 

 

GFS once again shows high pressure starting to become established as we move through the opening days of May

 

http://www.null/ds/gfs.htm

 

The ECM monthly outlook seems to be defaulting to below average temperatures. It's outlook for April was solidly below average and yet we are seeing three days of temps over 20c in the southeast. It now has that virtually retrospective peak at the start before heading back to default.

 

After a few days of cooler, more unsettled weather things look set to settle down again towards May. Remains to be seen what conditions are actually like on the ground if high pressure takes charge (as seems to be the theme at present) depending on where it sets up and what sort of feed we get. Worth noting that the met office have been going for a warmer, drier more settled period in May for a while now.

 

Big difference from last year, especially rainfall wise.

Edited April 23, 2013 by Pharaoh Clutchstraw

[johnholmes]

copied from the in depth thread-my view of what the weather may be as we get into the first week of May

http://forum.netweather.tv/topic/76236-in-depth-model-discussion-and-summaries/page-2#entry2684831

[Frosty.]

The fax charts are interesting, it looks like it could become fairly wintry towards the weekend in the northern most parts of the uk with troughs swinging southeast in a flow of arctic origins with showers becoming wintry with snow on hills, this cold air gradually being drawn south to all areas by friday although not as cold in the south as in scotland but the cold front bringing the change in airmass from tropical maritime to polar maritime/arctic reaches the south coast of england around 00z friday, into the weekend and the weather improves as a ridge slides southeast with more in the way of dry sunny weather and showers becoming isolated but a trough across the south on saturday would produce a line of prolonged showers before the ridge arrives from the north, also watch out for widespread night frosts once the ridge arrives, there are then signs of trouble ahead with a deepening low to the northwest of scotland which looks like bossing our weather during the first half of next week as it slowly pushes east towards scandinavia with a cold and showery spell lasting until later next week.

Edited April 23, 2013 by Frosty039

[summer blizzard]

Pretty nice FI..

 

[Summer Sun]

Once more we have 2 models going completely different ways

 

GFS and UKMO both at t144

 

 

Whilst the shorter term is uncertain we continue to see consistent hints of pressure building during early May

 

Edited April 23, 2013 by Gavin.

[Purga]

Wow! Temps set to get to -6C in sheltered parts of the N Midlands and -7C in N Wales

That's a drop of about 22C from todays daytime temps.  

[johnholmes]

I think at T+144 and beyond it is often better to look at the upper air situation rather than specifics at sea level Gavin.

In this case both show similar patterns in terms of upper air temperatures. One chooses to put a surface feature in the upper trough one does not.

[Frosty.]

Ukmo 12z looking good for sunday, could be a nice but rather cool sunny day for many areas after an early frost, monday shows milder/warmer air pushing northwest across southeast britain so the trough to the northwest is not in control at T+144 although it does look to be turning unsettled as pressure falls with heavy showers or even a longer spell of heavy rain, at least the majority of the weekend looks fine and dry after the very showery and rather cold day on friday.

[rory o gorman]

I think we cant write off the next week after tomorrow for warmth , but F.I plus ens are still hinting at a solid warm up

[Summer Sun]

Wow! Temps set to get to -6C in sheltered parts of the N Midlands and -7C in N Wales

That's a drop of about 22C from todays daytime temps.  

 

Remember thats only the minimum the maximum it could be at the same time is around 0c

 

 

Granted 0c is chilly but frosts in April is not unusual just a pain in the backside for growers

Edited April 23, 2013 by Gavin.

[NeilN]

0 is pretty chilly. Nothing unusual with frosts in late April but not good considering everything is late in bloom.

Does look encouraging that this cool spell is very brief. Why always a weekend though lol

[peterf]

0 is pretty chilly. Nothing unusual with frosts in late April but not good considering everything is late in bloom.

Does look encouraging that this cool spell is very brief. Why always a weekend though lol

It's good that the bloom is late and responding to current conditions.

no good having full blossom and a cold spell with no insect activity.

[Frosty.]

The Gfs 12z shows an unsettled and rather cold showery polar maritime flow during the first half of next week but then the weather becomes anticyclonic although just for a time, nw britain becomes unsettled again, the good news for the northwest is that further into FI the trough to the northwest then drifts away towards iceland/greenland and high pressure becomes dominant with a very blocked looking pattern for the uk, slowly becoming warmer so the risk of night frosts should lower as we go further into may. So it's very good news for everyone looking for a prolonged fine spell.

[Summer Sun]

the 12z ensembles continue with the steady rise as we move through the next 2 weeks precipitation continues to stay very low which is a complete difference to 12 months ago

 

 

If tonight's ECM is to be believed many should see a fine if not cool weekend though in the sunshine it will feel pleasant

 

Edited April 23, 2013 by Gavin.

[Methuselah]

the 12z ensembles continue with the steady rise as we move through the next 2 weeks precipitation continues to stay very low which is a complete difference to 12 months ago

 

 

If tonight's ECM is to be believed many should see a fine if not cool weekend though in the sunshine it will feel pleasant

 

Very much like last weekend, is my guess...