Model Output Discussion 06Z, 13 Sep. 2013 ---->

[Frosty.]

I may not expect it to verify - but there is always a pleasure to see a great synoptic looking chart at any time!

Here here, that's the best thing about looking at the models every day, waiting for exceptional charts to appear.

[Summer Sun]

Notice towards the end the Greenland high vanishes on GFS

 

Edited September 20, 2013 by Summer Sun

[Captain Shortwave]

A Chilly FI from GFS. Temps taking a tumble to Oct average.

 

graphe_ens4.gif

 

Looks like this upcoming warm spell has been toned down looking at the 5 day forecast for London this morning using the meto data, temps of  Sat 19c, Sun 20c, Mon 21c, Tues 20c.

 

Temps approaching 25c seem highly unlikely otherwise i would have thought meto would actually be forecasting it. Maybe the GFS overcooked the temps instead of undercooking.

Well during the summer, the GFS was pretty good, better than the BBC/Metoffice on many occasions, especially in situations like this where high pressure has set up near or over the UK. I would put more faith in the GFS at the moment on that ground and also the suppressed temperatures would suggest 100% cloud cover, especially in the south east despite a south westerly flow which has a continental influence to it. I have to admit I find it hard to believe that the whole weekend and even into next week would be completely cloudy to be honest.

ECM ens, look pretty average after about day 6, this would either suggest that conditions would either return to average, or that the model hasn't got a clue what's going to happen after Tuesday.

Edit just watched the BBC forecast and just as I suspected the temperatures are entirely based on 100% cloud cover. Helen Willetts (the forecaster) said temperatures could reach 20-22C on Saturday which is exactly where the GFS pitches the maximum to be on Saturday. 

Edited September 20, 2013 by Captain shortwave

[AWD]

Struggling to see a Scandi high in those charts you posted SS!

Notice you edited post, no worries!

In terms of cloudcover, I think this weekend will see a lot of cloud but as the flow turns more southerly and we pick up drier continental air, Monday & Tuesday should see much more sunshine and very good September temperature.

Thereafter is rather uncertain, although declining temperatures and SLP values are favoured, just to what extent is up in the air.

Edited September 20, 2013 by SeasonalWeatherWatcher

[Summer Sun]

Latest from Gibby

 

Hi everyone. Here is my report on the midnight outputs from GFS, UKMO, GEM, NAVGEM and ECM for today Friday September 20th 2013.

 

All models show a very confused and mixed pattern beyond the start of next week with a variety of different outcomes on offer this morning. In the short term the weather will be straightforward enough with a fine day today with sunny spells

under a ridge of High pressure. A weak warm front tracks NE across the UK tomorrow injecting milder Atlantic air across the UK with more cloud, hill fog and light rain and drizzle to the north and West before the weather brightens again from Sunday with some warm or very warm sunny periods developing in the South. Then things begin to diversify between the models as we progress through next week.

 

GFS shows lowering temperatures creeping down from the North later next week along with falling pressure with an eventual Low pressure belt developing from the Azores, across Southern England all the way to a deep centre over Russia. The result would be to increase the risk of rain over the UK with potentially rather cold conditions developing over the North as a NE flow develops. This Autumnal feel continues as pressure patterns reset to Low pressure developing over the UK vigorously and meaning rain and gales in rather cold conditions for all at the end of the run.

 

UKMO today has Low pressure slipping South towards Norway with another centre well to the SW while Southern Britain clings on to High pressure with fine and dry weather maintained for most at this stage with mist and fog issues at night a probability while the days stay bright and warm but less so in the North.

 

GEM shows colder air gradually sinking South across the UK next week as high pressure leaks away to the SE. Some rain or showers could well affect the North later next week in a cool NW flow while Southern areas come under attack from the SW later as Low pressure troughs edge in from the SW as part of a deep parent Low well out in the Atlantic Ocean.

 

NAVGEM is very much more relaxed in it's output today offering some influence from the Low to the SW early next week when some rain may occur in the far SW for a time as High pressure declines SE. However, later in the week the Low fills and High pressure is shown to build back up over the UK maintaining fine and dry conditions for all of the UK once residual cloud and any rain leaves the SW in relatively mild conditions.

 

ECM shows a period of slack winds and pressure for a time next week as our weekend High declines. Thereafter a new High forms close to the NW in much colder air which infiltrates down over the UK beyond midweek. Towards the end of the run milder Atlantic winds battle the cooler Autumnal air lying over much of Northern Europe with the North and East staying largely cool and bright while the SW become at risk from some heavy rainfall from slow moving troughs in a cool ESE wind.

 

The GFS Ensembles paint a strongly cooling trend this morning with uppers falling below average for a while following the warm interlude of the next few days. After a settled start the weather is shown to turn more changeable from most members with considerable spread at a quite an early stage of the output so much indecision is still likely with some stark changes run to run over the next few days likely.

 

The Jet Stream shows the flow being pushed north of the UK over the next few days before high pressure over the Arctic pushes it slowly back South over the UK and potentially to the South later next week, a pattern that we have seen so often over recent Autumn and Winter seasons, a trend that looks like it could be replicated again at the start of this season.

 

In Summary today there is a real cocktail of options on offer between the models and the ensemble members within each model. The next 4-5 days should be OK with benign and settled weather likely with some warm sunshine to be found, especially over the South. However, from early next week things become very complex as the surge of cold air over Northern Europe is shown to be considerable on some output. It is the interaction of this along with warm Atlantic air added to the fact that pressure is high over the Arctic that could set up some interesting synoptics over the next couple of days and I wouldn't be surprised to see a major and intense depression shown somewhere soon if these two opposing air masses are allowed to interact. As it is currently a gently cooling trend is shown with the risk of rain increasing from later next week as Low pressure gradually squeezes the life out of any UK High pressure later next week but will the rain come from the cold air to the North or warm air to the SW is anyone's guess this morning. Very interesting synoptics nonetheless.

 

http://www.norton-radstockweather.co.uk/Model-Analysis%282859336%29.htm

[Summer Sun]

Not too bad a run from ECM this morning with pressure rebuilding across the north

 

 

Temperature falling but in any sunshine it would still feel pleasant

 

NAVGEM on the other hand wants to rebuild pressure from the south keeping the UK fairly mild

 

[Frosty.]

The UKMO 00z shows a very summery spell from sunday until near the end of next week, temps up to 23c by sunday, closer to 25c on monday and peaking somewhere between 26-28c through the middle of next week with lots of sunshine and light winds, superb late september weather but by T+144 hours, look to the north, bottled up arctic air set to surge south?... it seems to me as though a much colder unsettled spell would sweep down across the uk by the very end of next week into the following week with strong N'ly to NE'ly winds, heavy rain and showers with snow on northern hills, it would be a shock to the system and very exciting at the same time. 

[SMU]

that confused me... i didnt agree with what was posted, and being new and not so technically minded/experienced in these charts i was wondering whether id got it wrong... doesnt that chart show a westerly upper flow? (with slight high anom to our east).

 

either way its still unreliable that far off .

 

 

Hi Mushy-  I have never not once - EVER used those charts-  Waste of time mate-  because they incorporate the super Ensemble mean- which is often similar to your name. - MUSH

 

The models continue to show mid term fluctuations- however the 'overall' trend is edging to another 'something' from the north-

 

I suspect the CET could get to the Norm by say the 26th & then tiptoe down to around ~0.3-0.5c below at the end of the month.

 

S

 

 

[Frosty.]

The ECM 00z ensemble mean is a peach of a run with increasingly very warm and sunny conditions by the start of next week, I would say we could even use the word HOT to describe the weather across the southern half of england and wales for most of next week, or at least very warm with temps in the mid to high 20's celsius, the summery weather would also be across the rest of the uk but not quite as warm and sunny as further south but very pleasant for the time of year with low 20's celsius, just a bit more unsettled across the far northwest corner of the uk. Looking further ahead, a slow decline in conditions with cooler air filtering south but remaining fairly calm and fine the further south you are with temps drifting down to around average with increasingly chilly nights and fog patches, Further north it would eventually become more unsettled. There is a suggestion at the end of the mean that warmth would start to spread north again.

[SMU]

Well, some synoptically stunning charts in FI from the GFS there. Won't bring anything of note in early October but as Steve Murr has pointed out on several occasions, that polar profile is breathtaking.

 

Whats also notable is ALL the long range models including the ALL important Glosea4 which the Met use is showing significant + VE blocking for the NDJ ( nov dec jan ) period-

All the blocking is focussing on a spread from Greenland to Scandi with a southerly tracking jet....

 

I sense there is an air of expectation around winter this year-

 

 

S

[Tamara]

I think a lot of these synoptic charts with the wintry appeal are very common most years at this time of year  In fact higher latitude blocking often features as a prelude to the polar vortex seasonally organising itself through the autumn. As the upper stratosphere starts to cool in line with cyclical seasonal trends, it starts to push warmer anomalies below it to the surface and this manifests itself as high pressure at higher latitudes

 

The outlook maintains a pleasant, fairly warm and settled outlook for the foreseeable future through most of next week with still that signal for something maybe more unsettled before months end. I think that the duel between ferrel and polar cells will continue for some while yet to muddy the water and taking a snapshot of the EPS member ensembles at day 7 (end of next week) depicts this Heinz 57 mixture quite well this morning with an assortment of tropical and polar solutions in the mix with weakness of pressure featuring to the south west and also that deeper troughing signal to the NE with pressure high over the eastern side of the arctic above it. That leaves the UK in something of a transitional (one way or the other) no-mans land with either high or low pressure on the peripheries of the UK..although there are also some solutions that place a trough right over us and bring that potential unsettled end of month solution rather earlier.... This is quite likely too progressive..although the blocking signal to the north does point towards this maybe therafter

 

Conclusion?..much the same thinking as before..and the most likely outcome, at least for now, is that the fairly settled weather should last through most of next week for many, and the very uncertain question remains will the signal recyle for a more unsettled spell (thinking of our pincer movement) and then perhaps renewed high pressure into the first part of October..or will a more semi permanent signal take charge of the patterns in line with seasonal wavelengths? And will another tropical feature like Humberto come along in the meantime anyway to offer yet another further script?   The models are already too much of a dogs breakfast at the end of next week anyway to try and second guess how the t/c's signals might influence them, without adding uncertain tropical feature development and movement in the mix..maybe simply because there is something of a duel background signal right now as described

[Captain Shortwave]

06Z GFS showing the warmth persisting in the south up to Wednesday

Breakdown from the north west on Thursday

 

Again not exactly many similarities between individual runs, with other models, anomalies or even ensembles.

[Bogman]

Whats also notable is ALL the long range models including the ALL important Glosea4 which the Met use is showing significant + VE blocking for the NDJ ( nov dec jan ) period-

All the blocking is focussing on a spread from Greenland to Scandi with a southerly tracking jet....

 

I sense there is an air of expectation around winter this year-

 

 

S

 

 

And this time, it's not just wishful thinking. Tentative signs of things to come.

[Severe Siberian icy blast]

The UKMO 00z shows a very summery spell from sunday until near the end of next week, temps up to 23c by sunday, closer to 25c on monday and peaking somewhere between 26-28c through the middle of next week with lots of sunshine and light winds, superb late september weather but by T+144 hours, look to the north, bottled up arctic air set to surge south?... it seems to me as though a much colder unsettled spell would sweep down across the uk by the very end of next week into the following week with strong N'ly to NE'ly winds, heavy rain and showers with snow on northern hills, it would be a shock to the system and very exciting at the same time. 

Frosty I'm afraid your temps are way out . Again . You search and search for the holy grail in every model , but they fail to materialise mostly . The temps this wkend will be 20/21c , maybe a 23 in the southeast in London . But 26/28c middle of next week I'm afraid is way out . Why don't you just offer a balanced and more realistic forecast rather than chasing the most extreme solution possible when in reality has little chance of verifying . As we no especially given the time of year the models are very volatile , and anything past Monday is far from certain .

My guess is a nice wkend , temps into the low twenties at best , lasting till tue , then all we can look for is trends , and that looks like to be in the form of an attack from the north as low pressure pushes down from the northeast , how cold and how far south the cold air gets is unknown , but it's likely that the models will tone down any cold northerly outbreak nearer the time , once the models settle down after picking upon a pattern change

[Scorcher]

06Z GFS showing the warmth persisting in the south up to Wednesday

Breakdown from the north west on Thursday

 

Again not exactly many similarities between individual runs, with other models, anomalies or even ensembles.

 

Yes that run is a big improvement on the 00Z, it would actually remain warm in the far south to Thursday- basically the further south you are the longer the warmth will hang on, but I suppose that's how it usually works! The run then shows cooler air coming in from the north later on, but it struggles to get into the south of England at all- temperatures are still shown to be above average there until Friday.

 

The GFS has certainly come more into line with the ECM and UKMO with this run. Any changes to much cooler air are in FI at the minute.

[Frosty.]

@ severe siberian icy blast....Actually the met office expect 23c by sunday and then higher than that for much of next week, remember we can get over 80F in october, 21-22c max tomorrow, 25c by monday, then a touch higher, I think that sounds realistic based on what the Ecm 00z ensemble mean shows, and the ukmo 00z.

Edited September 20, 2013 by Frosty.

[Captain Shortwave]

Frosty I'm afraid your temps are way out . Again . You search and search for the holy grail in every model , but they fail to materialise mostly . The temps this wkend will be 20/21c , maybe a 23 in the southeast in London . But 26/28c middle of next week I'm afraid is way out . Why don't you just offer a balanced and more realistic forecast rather than chasing the most extreme solution possible when in reality has little chance of verifying . As we no especially given the time of year the models are very volatile , and anything past Monday is far from certain .My guess is a nice wkend , temps into the low twenties at best , lasting till tue , then all we can look for is trends , and that looks like to be in the form of an attack from the north as low pressure pushes down from the northeast , how cold and how far south the cold air gets is unknown , but it's likely that the models will tone down any cold northerly outbreak nearer the time , once the models settle down after picking upon a pattern change

26C has been predicted on a few GFS runs so it's not out of the realms of possibility if we get a decent southerly feed.

As for trends, the ECM ens speak for themselves, there is really nothing to go on which is no surprise given we have two split flows developing in the Atlantic at the same time. One of these has the ability to cripple model output reliability but 2. We might have Tuesday resolved by about Sunday at this rate, let alone the rest of the week. The ECM northerly has been dropped by the ECM now and well the GFS has picked it up, and then delayed it by a good 36 hours on it's latest run. We are seeing the warm spell last over a week on one run, then only 2 days on the next. Yay for model uncertainty

Edited September 20, 2013 by Captain shortwave

[Suburban Streamer]

the MJO also doesnt suggest a sustained settled spell.  We have been in (weak) phase 5 since around 15th September and forecast to move through to phase 6.  10-12 day lag brings us to the end of next week to see something more benign before turning more unsettled into first week of october?

 

Edited September 20, 2013 by Suburban Streamer

[Scorcher]

@ severe siberian icy blast....Actually the met office expect 23c by sunday and then higher than that for much of next week, remember we can get over 80F in october, 21-22c max tomorrow, 25c by monday, then a touch higher, I think that sounds realistic based on what the Ecm 00z ensemble mean shows, and the ukmo 00z.

 

Yes I agree it's very possible- a lot will depend on cloud amounts though. Looking at the charts this morning it seems that Saturday will be mostly cloudy for most but then the wind seems to turn more of a southerly direction from Sunday which should aid the cloud breaking up. In sunshine those 15C uppers should allow temperatures into the mid 20s for Monday, possibly over a quite widespread area of England and Wales.

[johnholmes]

@ severe siberian icy blast....Actually the met office expect 23c by sunday and then higher than that for much of next week, remember we can get over 80F in october, 21-22c max tomorrow, 25c by monday, then a touch higher, I think that sounds realistic based on what the Ecm 00z ensemble mean shows, and the ukmo 00z.

 

I think you are mis reading the values Met are actually quoting, at least for the SE, this link shows their expected max values for that region out to Tuesday

http://www.metoffice.gov.uk/weather/uk/se/se_forecast_temp.html

 

maybe you are thinking of another region frosty but the key to any high temperature is IF there are prolonged sunny periods. Nothing in any model to me suggests more than sunny spells?

[Newberryone]

Whats also notable is ALL the long range models including the ALL important Glosea4 which the Met use is showing significant + VE blocking for the NDJ ( nov dec jan ) period-

All the blocking is focussing on a spread from Greenland to Scandi with a southerly tracking jet....

 

I sense there is an air of expectation around winter this year-

 

 

S

I too share in your optimism and desperately hope it's not like last winter in that it may just be the beginning of a series of false dawns  

[Frosty.]

I think you are mis reading the values Met are actually quoting, at least for the SE, this link shows their expected max values for that region out to Tuesday

http://www.metoffice.gov.uk/weather/uk/se/se_forecast_temp.html

 

maybe you are thinking of another region frosty but the key to any high temperature is IF there are prolonged sunny periods. Nothing in any model to me suggests more than sunny spells?

Yes John, I just meant somewhere in the uk could potentially reach 23c by sunday, then even warmer on subsequent days, although it does look very decent for all areas for a while next week under anticyclonic conditions, nothing to be sniffed at for sure.

[Captain Shortwave]

The only certainty here is the verification stats for one or more of the big models is going to seriously tank over the coming days 

[Frosty.]

Yes I agree it's very possible- a lot will depend on cloud amounts though. Looking at the charts this morning it seems that Saturday will be mostly cloudy for most but then the wind seems to turn more of a southerly direction from Sunday which should aid the cloud breaking up. In sunshine those 15C uppers should allow temperatures into the mid 20s for Monday, possibly over a quite widespread area of England and Wales.

Exactly scorcher, to the east of high ground looks best with clouds breaking to allow longer sunny spells and temps into the 70's F, then mid to high 70's F next week with increasing amounts of sunshine, looks great to be honest.

[johnholmes]

The ECM 00z ensemble mean is a peach of a run with increasingly very warm and sunny conditions by the start of next week, I would say we could even use the word HOT to describe the weather across the southern half of england and wales for most of next week, or at least very warm with temps in the mid to high 20's celsius, the summery weather would also be across the rest of the uk but not quite as warm and sunny as further south but very pleasant for the time of year with low 20's celsius, just a bit more unsettled across the far northwest corner of the uk. Looking further ahead, a slow decline in conditions with cooler air filtering south but remaining fairly calm and fine the further south you are with temps drifting down to around average with increasingly chilly nights and fog patches, Further north it would eventually become more unsettled. There is a suggestion at the end of the mean that warmth would start to spread north again.

 

frosty I hate to spoil your summer party but you are getting a touch OTT in my view in your interpretation of how high temperatures are going to be, from whatever model you quote.

I simply cannot see that values will approach the 'hot' category for the 3rd week in September as you suggest nor do I see the temperatures actually reaching, other than in isolated spots where good cloud breaks occur, the values you quote.

I am trying to be objective.

the link below is from Greenwich showing the average values for 1981-2010 the maximum for September=19.7C. Met O definition for hot is +7C so it needs to get to 26C to be 'hot' for the London area at this time of year.

 

http://www.metoffice.gov.uk/climate/uk/averages/19812010/sites/greenwich.html

 

Look at the visual sat picc each morning to see how much low cloud is around for your area, look at the 925mb wind to see if this might clear or bring in some low cloud. If you can 'read' ske-t diagrams, take a look at the one nearest to you, note the low level wind direction re the comment about sat piccs, also is there a low level inversion with moisture around that level. If there is then as the temperature rises then the initial shallow Cu may well end up spreading out under that inversion, much as is happening outside my window at the moment after a mianly sunny morning. There are a lot of factors to take into consideration.

 

All that said like frosty and others I would love to see some late sumery type heat and sunshine this weekend and into next week. That is the biased side of me talking.

and re the later post from frosty-sure there is potential but potential only IF the factors I have outlined for cloud cover are not there on any particular day. 

Edited September 20, 2013 by johnholmes