Model Output Discussion 31/03/14 onwards.

[Gibby]

HERE IS THE LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM TODAY WEDNESDAY 14TH MAY 2014.

 

THE CURRENT GENERAL SITUATION. An anticyclone will build across Southern Britain through today and tomorrow while a warm front is expected to cross NE across NW Britain later today and tonight.

 

GFS The GFS Ensembles indicate an area of low pressure slips South across western Britain to lie to the SW of the UK for several days with outbreaks of rain for many but principally across more Southern and Western Britain. As days pass details become difficult to pin down but with the lack of any significant High pressure shown and quite slack conditions overall further showers or outbreaks of rain can be expected at times but with some dry and brighter weather too in places, especially towards the East.

 

UKMO UKMO shows the start of next week with Low pressure re-established across the UK with showers or longer spells of showery rain again with winds generally becoming a gentle Southerly or SE'ly and temperatures returning to nearer to average due to the increase of cloud cover.

 

GEM The GEM operational today shows Low pressure settling down towards the South of the UK through next week with unsettled weather for many delivering rain and showers for all, perhaps more especially towards Southern Britain. Temperatures would return close to average with a chilly wind off the North Sea for a time across more NE areas.

 

NAVGEM NAVGEM develops Low pressure further to the SW next week keeping the most unsettled and sometimes wet weather more towards the South and West while Northern and Eastern Britain stay drier and brighter in the NW but with a cool and cloudy North Sea breeze over Eastern Scotland and NE England.

 

ECM today shows Low pressure spiraling around to the SW of Britain through next week sending troughs North and East over Southern and Western Britain in particular with rain and showers in these areas as a result. Though also likely to see some rain at times Northern and Eastern parts may see the best chance of seeing longer drier periods but a chilly North Sea breeze will affect North Sea coasts at times.

 

MY THOUGHTS  Today's output continue to model Low pressure becoming influential over the UK for the period commencing from later this Sunday. With the majority of output suggesting Low pressure becoming slow moving close to SW Britain will probably mean the heaviest and most persistent spells of rain and showers will affect more Southern and Western Britain. Northern and Eastern parts look like they could miss at least some of the rainfall with the chance of something drier and warmer at times though with a flow from the East or SE here North Sea coasts could become plagued by dull and chilly North Sea haar conditions with the NW of Scotland being probably the warmest area at times. Longer term this morning Low pressure looks to hold control in one form or another near the UK with a continuation of outbreaks of rain and showers scattered about across the UK with little sign of anything reliably like high Summer shown as yet.

[Summer Sun]

The GFS 00z ground level values shows very little rain on the London ensemble between now and the 21st even though pressure falls

 

 

The Manchester ensemble however looks wetter

 

 

And finally over in Aberdeen bar the 18th / early part of the19th it too shows a fairly dry picture

 

 

So some rain yes next week but the east may not see much if the ground level values are correct

[MR EXTREMES]

i think it must be noted that convective and thundery humid to, so much better than cool and wet with some excitement in the form of thundery rain or convective in nature.

mid 70s is not out of the question in longer sunny spells south and southeast will fair the best for temps.

[Summer Sun]

Assuming UKMO is wrong with its 850's the start of next week is looking warm & humid with thunderstorms quite likely in places though as I said before the east looks driest for the opening half of the week

 

 

Looks nice and warm for the RHS Chelsea flower show next week as well though it could turn wetter from the Thursday

Edited May 14, 2014 by Summer Sun

[Frosty.]

Well we never saw a winter, just a loooong wet and windy autumn with mild/cool zonality but we are definately having a warm spring with power to add..hope we have a hot summer. :-)

[johnholmes]

Make the most of the latter part of this week and Saturday, probably Sunday for some parts over the south of the UK. Beyond that then to me all the indications are that for at least the next 7 perhaps 10 days, cool and unsettled will be the theme. The 500mb contour line over the south of the UK starts life over northern Canada with a height of 546dm, perhaps a bit below, that is fairly cold air for the UK for this time of the year.

[shaky]

Might be very warm next week but there could be some serious thunderstorms around!!have a feeling the output will change again though!

[Gibby]

Make the most of the latter part of this week and Saturday, probably Sunday for some parts over the south of the UK. Beyond that then to me all the indications are that for at least the next 7 perhaps 10 days, cool and unsettled will be the theme. The 500mb contour line over the south of the UK starts life over northern Canada with a height of 546dm, perhaps a bit below, that is fairly cold air for the UK for this time of the year.

Yes I agree John. High temperatures are not highly likely next week imo from todays output. Warm uppers at times yes but high humidities will mean a lot of cloud generally and rain to boot at times for many. I think the best temperatures could end up in the Westand NW of scotland if an ESE flow sets up. With humid air in tow these areas could see some fair weather while conversely near the North Sea could be dull and cold with sea fog and low cloud for much of the time. 

[Frank Trough]

Make the most of the latter part of this week and Saturday, probably Sunday for some parts over the south of the UK. Beyond that then to me all the indications are that for at least the next 7 perhaps 10 days, cool and unsettled will be the theme. The 500mb contour line over the south of the UK starts life over northern Canada with a height of 546dm, perhaps a bit below, that is fairly cold air for the UK for this time of the year.

 

So that indicates something other than low pressure to the west/southwest? Something more akin to previous GFS runs which had the low further north and east? It's been interesting watching the swings over the last few days - it often is when the models play around with low pressure moving up against a block.

 

Whatever happens with the positioning of the low i'm expecting central/southern England to be wet next week.

[knocker]

Make the most of the latter part of this week and Saturday, probably Sunday for some parts over the south of the UK. Beyond that then to me all the indications are that for at least the next 7 perhaps 10 days, cool and unsettled will be the theme. The 500mb contour line over the south of the UK starts life over northern Canada with a height of 546dm, perhaps a bit below, that is fairly cold air for the UK for this time of the year.

 

I take it that's from NOAA John? The ECM ens is much the same, just a tad higher.

Edited May 14, 2014 by knocker

[Frosty.]

The 500mb anomaly charts are sometimes wrong, hopefully the very warm output this morning will herald a new trend with low pressure to the southwest and high pressure to the east with a feed from southern europe/north africa instead of the dismal atlantic.

[knocker]

Yes I agree John. High temperatures are not highly likely next week imo from todays output. Warm uppers at times yes but high humidities will mean a lot of cloud generally and rain to boot at times for many. I think the best temperatures could end up in the Westand NW of scotland if an ESE flow sets up. With humid air in tow these areas could see some fair weather while conversely near the North Sea could be dull and cold with sea fog and low cloud for much of the time. 

 

You may well be right but the GFS output certainly has high STs until Tuesday at least. Not that I'm saing they are correct.

[Frosty.]

The only fly in the ointment during the coming days is the cloud amounts, there will probably be large amounts of cloud but the sun will punch some holes in it, especially the further southeast you are, it will probably become generally sunnier by saturday but with a risk of isolated heavy showers but for the northwest of the uk a wriggling front will produce some rain at times and less warm than elsewhere.

[IDO]

The ECM op run is back to its old trick of being an outlier (outside the SD) compared to its mean.

 

T168 op: 

 

De Bilt 2m temps: 

 

About 6c above the mean on D7. In fact very close to the GFS op, that also was an outlier within its members.

 

Could be as Frosty has noted, a new trend has been spotted by the higher-res runs. However the means have been so consistent it is probably prudent to stick with them.

 

ECM Mean D5:   D10: 

 

It goes with the cooler flow.

 

Also GEM op at D6:  Whereas the mean is in line with ECM and GFS: 

 

So no real change from the mean. Will have to see if the outlier ops from GEM, ECM and GFS are replicated.

[Frank Trough]

06z maintains the theme of the warmer feed - nothing cool showing on this run in terms of uppers.

 

 

GFS now pretty close to the ECM at the same timeframe:

 

 

so either the ops are wrong and we'll see low placed differently to allow cooler uppers or perhaps the higher res ops have handled the crucial nearer timeframe better than the ensembles?

 

either way, bucket loads of rain for places in the south I would think. Possibly more with a warmer, unstable southeast feed.

[shaky]

Yup 06z maintains the very warm thundery theme for next week!!temperatures widely into the low 20s across england and wales well into next week!!if everything moves slightly further west next week then we could be looking at temps into the high 20s and maybe even touching 30 degrees considering how hot it is just across the continent!!

[Summer Sun]

GFS continues with its warm, humid and thundery outlook for next week

 

 

Met office also suggesting it could remain very warm in the east at times next week with longer spells of rain in the west and south west though no where is immune from some rain at times

 

Temperatures next week probably closer to average for most areas, but perhaps very warm at times in the east and feeling close here too.

Edited May 14, 2014 by Summer Sun

[Chris K]

Yup 06z maintains the very warm thundery theme for next week!!temperatures widely into the low 20s across england and wales well into next week!!if everything moves slightly further west next week then we could be looking at temps into the high 20s and maybe even touching 30 degrees considering how hot it is just across the continent!!

It's interesting to see the consistency in each GFS run, but until there is similarity between ops and mean outputs, I will stay a bit cautious as to how this is going to pan out. It only takes small adjustments in the Atlantic & European pressure patterns for us to either end up being influenced more by the cooler air, or the warmer, humid air from the South. Lots of time for change, although unsettled seems to be the key theme at this time (be it mild or more warm).

 

It is not uncommon for the models to produce outputs showing low pressure disturbances moving up from the South late Spring & Summer, only for them to either hardly form at all, or get pushed NE'wards across France/Belgium rather than more North towards the UK. The weather next week will also depend how far East the LP makes it as it also drops down towards the Bay of Biscay (If it does). Cloud amounts will also be a factor as well when it comes to thundery weather.

 

Oddly enough people mention that GFS often models LP systems too far East but actually I find the opposite happens more often during the Late Spring & Summer period. So many times it would edge just that bit more East day by day for patterns like what GFS has shown this morning.

 

I could be wrong, but that's my interpretation of this type of pattern from folllowing the models in recent years.

Edited May 14, 2014 by Chris K

[johnholmes]

The 500mb anomaly charts are sometimes wrong, hopefully the very warm output this morning will herald a new trend with low pressure to the southwest and high pressure to the east with a feed from southern europe/north africa instead of the dismal atlantic.

 

you can hope Frosty but it is that I am afraid-hope. Yes of course the anomaly charts are sometimes wrong but on a much much lower scale than the synoptic models. With the contour heights they are solidly predicting for the 6-15 day period then it is never going to be warm by Met O definition for late May. How much lower than 'warm' is not too clear, around normal to a bit below I would suggest and with bands of rain or showers rather than the dry spell developing today and into Saturday/Sunday for most.

 

re the temperatures, I should have added that regardless of the 500mb contour heights IF the surface system (low pressure) sets up in a position to give a low level flow from between south and SE then warm and muggy is a distinct possibility for some parts of E and SE England although that type of wind flow may mean some coastal districts are somewhat on the cool side.

Edited May 14, 2014 by johnholmes

[IDO]

^^^

 

The latest Met Update ties in nicely with Mr Holmes' analysis:

 

"

UK Outlook for Monday 19 May 2014 to Wednesday 28 May 2014:

Monday and Tuesday will see a change towards more unsettled conditions for the UK than experienced over previous days. Showers or longer spells of rain are likely to spread from the west, these will possibly be heavy with thunder and hail at times. The remainder of the week is likely to remain unsettled, with showers for most, but also some longer spells of rain, these most likely in the west and southwest. Temperatures next week probably closer to average for most areas, but perhaps very warm at times in the east and feeling close here too. Towards the end of the period, there are indications that the unsettled conditions may persist for most, particularly in the north and west."

 

The last couple of GFS op runs suggests the potential for substantive local downpours especially for the south/SE initially  

 

Some unstable weather for fans of this, also on the cards:

Edited May 14, 2014 by i'm dreaming of...

[shaky]

12z rolling out!!fingers crossed for the continuation of the warm humid theme for next week!!

[Summer Sun]

12z rolling out!!fingers crossed for the continuation of the warm humid theme for next week!!

 

Still looking quite warm for those in the east to start next week certainly can't rule out some thunderstorms at times if the warm air does hang around the east could become very humid at times as well

 

 

UKMO and GFS look in pretty good agreement at t120

 

 

GFS showing the warmer humid air starting to move to a wider area by t168

 

Edited May 14, 2014 by Summer Sun

[Gordon Webb]

well providing it's in the east I won't mind

 

warm humid thundery weather is not my cup of tea

Edited May 14, 2014 by Polar Maritime
Please keep Model ramps & moans in the correct thread thanks.

[IDO]

No surprise that 2m temps are forecast to be around 4c lower on the 12z compared to the 0z on Day 6:

 

12z:   0z: 

 

Though the east and NE still looking at better temps than yesterday's runs. NAVGEM also now hinting at this:

 

GEM the most optimistic still: 

 

The continued trend for after the trough slips away (around D11 on the op) is for heights to build from the Azores to Scandi; so by well into FI:

 

 Early days.

 

 

Edited May 14, 2014 by i'm dreaming of...

[Captain Shortwave]

Still a lot of runs needed until we get even next Monday right. very tight situation here. Still questions on how far south the low will go and hence how warm the flow will be into the UK. The next is what happens to that low?

 

One thing I will say is with the Russian/Scandi block trying to push westwards again next week, I'm surprised no model has tried to link the high with the Amplified Atlantic ridge and fully cut off the low. That outcome is worth watching to see if it crops up in the next day or so.