Model Output Discussion - 31/8/14 Onwards.

[Captain Shortwave]

Looks like the game is up, ECM just a variation on the overall theme for week 2 as we see a transition to more unsettled weather this coming weekend.

That Atlantic ridge looks like a sure bet now. Low pressure has no where to go except for dropping near or around the UK. Of course the placement of the low will determine where the wettest and coolest places will be.

[knocker]

Quite right Cs. Is the appropriate word OUCH There is snow on them there hills..........................

Edited September 29, 2014 by knocker

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY MONDAY SEPTEMBER 29TH 2014.

 

NEXT UPDATE TUESDAY SEPT 30TH 08:00

 

THE CURRENT GENERAL SITUATION. A slack pressure gradient remains in place across the Brtish Isles with a front reaching NW Britain tomorrow and a shallow pool of instability in the upper atmosphere crossing NE over Southern Britain today.

 

MODELS-2 WEEK HEADLINE  Continuing largely benign this week with a lot of cloud and a little rain at times especially in the NW. Becoming more unsettled and cooler for all later with more widespread rain at times.

 

THE JET STREAM ENSEMBLE FORECAST

The Jet Stream remains positioned to the NW of Britain for much of this week before it troughs South over the UK next weekend and persists in this trough pattern close to the UK for most of week 2 with varying strengths.

 

GFS The GFS operational this morning shifts High pressure steadily East and declines it later in the week as pressure falls across the UK from the NW. After a benign start to the period SW winds freshen everywhere late in the week with a much more unsettled feel to the weather everywhere across Britain in Week 2 with occasional rain or showers and fresh winds too lowering temperatures towards the seasonal average as Low pressure engulfs the UK or lies just to the West.

 

THE GFS ENSEMBLES.

The GFS Ensembles are symbolic of the operational through the first half of the run and while some continuation of occasionally wet and windy weather remains through Week 2 pressure is shown to be High to both the East and SW and a linking ridge could cut off the unsettled weather later with just the extremities North and South liable to see further showers in an otherwise return to more benign conditions again.

 

UKMO UKMO this morning shows High pressure declining later in the week. After a weakening trough crosses East over Wednesday with just a little rain SW winds freshen more markedly by next weekend with more active fromts bringing rain SE across the UK by the end of the run with temperatures falling back towards average values.

 

THE FAX CHARTS  The Fax Charts agree with the pattern of the raw data and remain unedited in any major way. Therefore the weather will be benign through the week but not discounting a little rain midweek as cold fronts are shown to slip SE. A ridge following shows a couple of drier and for some fresher weather days before wind and rain moves down from the NW under a more active SW flow by the weekend lowering temperatures then.

 

GEM The GEM operational also manintains the trend shown by other output this morning with a shift away from the fine and quiet conditions of much of this week with just a little rain for a time midweek to a much more active weather pattern with a concoction of Lows and troughs circling the UK next week with rain at times along with fresh winds and temperatures generally much cooler than of late.

 

NAVGEM NAVGEM too shows a decline in conditions by next weekend and the start to the new week with Low pressure becoming resident close to northern Britain with troughs swinging East in the flow. Temperatures will fall back to average after most of this week stays somewhat warm at times and winds will be much more noticeable.

 

ECM The ECM operational today completes the set with unsettled and windy weather arriving from the NW by the weekend as a deep Low moves down across the UK giving strong cyclonic winds with spells of rain and showers in much cooler weather than of late to start next week.

 

NOTABLE TREND CHANGES FROM PREVIOUS RUNS There is finally good cross model support for the trend to cooler and more unsettled, windier weather for all areas by the end of the week lasting through week 2.

 

MY THOUGHTS  The models continue to strengthen there trend towards a much cooler and more unsettled period of weather starting at the end of the working week and extending SE to cover all of the UK by the end of next weekend. Changes will feel marked as we have enjoyed some very protracted warmth and calmness to the weather of late so the increase in wind and more pronounced rainfall events will enhance the feel of the lower temperatures we will receive. The change of weather will move down from the NW and with the Jet buckling South to engulf the UK in a trough like form at the weekend and sustaining this pattern well into next week if not beyond. So once the unsettled weather arrives it will probably remain sustained, in particular as some cold air advecting West across Scandinavia next week is shown by several model runs this morning which once engaging with the unstable air over the UK could give rise to even more potent depressions towards the end of the period. However, as always there are always exceptions to this theory and the GFS Ensembles do show a return to High pressure as heights to the East and SW remain High possibly with a linking ridge over the UK late in the period to bring extensive mist and fog problems if that theory evolves rather than wind and rain. Having said all that this morning offers good overall support for Autumn proper to arrive next weekend with some decent amounts of rain and fresh breezes for most areas at times from then on with the much cooler feel of conditions becoming the main talking point as daytime temperatures fall some 5C or more from current daytime values across the South.

[Summer Sun]

GFS shows temperatures much lower from Saturday with temperatures on Monday just making it into double figures

 

 

So after a warm and fairly settled start to Autumn it does look as if things are going to turn wetter, windier and cooler

Edited September 29, 2014 by Summer Sun

[Polar Maritime]

Models starting to firm up on the breakdown, With the GFS showing the Atlantic influencing the BI by the 4/5th, With much cooler/unsettled weather which will be a real shock to the system. The Low then being cut off and stalling/spinning over the UK maintaining the unsettled theme through-out the run, With Height's pushing North. As has already been mentioned, Some very strong blocking over Greenland towards the end of the run, Interesting synoptic's indeed. 

 

Edited September 29, 2014 by Polar Maritime

[knocker]

Gibby, I'm no doubt being a bit thick but I'm not understanding what you mean by. "before it troughs South" and "persists in this trough pattern".

 

 

 

THE JET STREAM ENSEMBLE FORECAST

The Jet Stream remains positioned to the NW of Britain for much of this week before it troughs South over the UK next weekend and persists in this trough pattern close to the UK for most of week 2 with varying strengths.

Edited September 29, 2014 by Polar Maritime
To remove long quote.

[knocker]

This depression is producing hurricane force winds and a mega-blizzard in SE Greenland,

Edited September 29, 2014 by knocker

[phil nw.]

Models starting to firm up on the breakdown, With the GFS showing the Atlantic influencing the BI by the 4/5th, With much cooler/unsettled weather which will be a real shock to the system. The Low then being cut off and stalling/spinning over the UK maintaining the unsettled theme through-out the run, With Height's pushing North. As has already been mentioned, Some very strong blocking over Greenland towards the end of the run, Interesting synoptic's indeed. 

 

Yep much more Autumnal looking next week PM that's for sure.

Some more images from the GFS 00z ens suite to illustrate the change.

These for next Tuesday when the Atlantic trough has moved in.

Postage stamps,members all modelling a similar picture with the low centre stage along with the mean 850hPa temp. chart and Warks.2mtr  temperatures showing a dip after the weekend as the colder air moves down from the north west.

 

 

A big difference in the feel of things coming up then with cooler and wetter weather around after this week.  

.

[Summer Sun]

Autumn very much on its way looking at GFS

 

 

 

After a clam start to Autumn next week is likely to see some big changes, whether this lasts for a lengthy time or not remains to be seen

[Gibby]

Gibby, I'm no doubt being a bit thick but I'm not understanding what you mean by. "before it troughs South" and "persists in this trough pattern".

 

Sorry for the delay in replying. What I mean is that when looking at a map of the UK the Jet Stream troughs South (turns South to the West of the UK) and then turns back North (to the East of the UK) creating a U shape image which in the Northern hemisphere means a trough or Low pressure lies within these parameters thus near to or across the UK and it was this that I was referring to persisting. Hope that helps.

[knocker]

Sorry for the delay in replying. What I mean is that when looking at a map of the UK the Jet Stream troughs South (turns South to the West of the UK) and then turns back North (to the East of the UK) creating a U shape image which in the Northern hemisphere means a trough or Low pressure lies within these parameters thus near to or across the UK and it was this that I was referring to persisting. Hope that helps.

 

So basically meridional flow and following the long wave pattern as here with the cold air north of the jet. I take it then it would be ridging (using your terminology) in the western Atlantic? I'm not trying to funny just haven't come across that way of expressing it before. A very good web site by the way.

Edited September 29, 2014 by knocker

[Frosty.]

BIG change on the way, Hooray I hear some of you say   we will see a marked change to very autumnal weather by the start of next week according to the Gfs 06z op run with a dartboard low finally bringing autumn with a vengeance, very disturbed charts for most of next week with the vigorous depression only filling slowly more or less in situ. Considerably cooler & windier next week with temperatures much closer to where they should be for early / mid october with persistent, sometimes heavy rain alternating with sunshine and squally showers, temperatures around mid teens celsius at best and rather lower than that across much of the north.

 

By the end of the run, high pressure makes another appearance which would probably mean a lot of fog and a risk of frost around mid october if it verifies but it doesn't look as though it would hang around for more than a few days. Proper autumn is on the way, the transition from settled to unsettled occurs during next weekend, sooner in the NW but very unsettled for all of us next week based on this run.

Edited September 29, 2014 by Frosty.

[Summer Sun]

After a delayed start Autumn looks like getting started next week with low pressure replacing our prolonged period of high pressure, consequently temperatures will be a lot lower than we've had so far this Autumn we'll also be seeing some winder and wetter conditions

 

 

GFS

 

 

Northern blocking very much on show early next week

 

Edited September 29, 2014 by Summer Sun

[knocker]

Sorry for the delay in replying. What I mean is that when looking at a map of the UK the Jet Stream troughs South (turns South to the West of the UK) and then turns back North (to the East of the UK) creating a U shape image which in the Northern hemisphere means a trough or Low pressure lies within these parameters thus near to or across the UK and it was this that I was referring to persisting. Hope that helps.

 

Actually although in this case that is correct it isn't necessarily so every time in the northern hemisphere. You could have an anticyclone NW of the UK with the jet running around to the south and then NE.as it's the thermal gradient between cold and warm air not LP and HP.

[Polar Maritime]

Again the GFS maintains the theme for a pattern change, To a much cooler and unsettled N/W flow off the Atlantic by the 4/5th, And continuing out into the run, Autumn proper..

 

Edited September 29, 2014 by Polar Maritime

[Frosty.]

Tonight's GEFS 12z mean is about as emphatic as you can get supporting a very unsettled outlook, low pressure swinging SE and bringing real autumn weather, the kind of which we haven't seen during september which has been mainly anticyclonic, well this run is very much anti anticyclonic with frequent bouts of wet and windy weather separated by sunshine and showers and in any brief calmer slots, a good chance of night frost and fog patches but overall it will become much cooler than so far this autumn, especially for the NW with the SE tending to have the best of any fine weather between weather systems, especially towards mid october and temperatures that bit higher across the southeastern ½ of england but it's a major pattern change on the way for all of us.

[tinybill]

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=6

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=204

 

evening all looking at the  models i think its safe to say our late summer  over  as for fantasy world  2  words    VERY  WET!!!

[ANYWEATHER]

At last there is a model consensus  from the the ecm and Gfs  of a major pressure change ,,,,Cold wet and windy sums it up....     :Not saying I like that  scenario

Edited September 29, 2014 by ANYWEATHER

[Frosty.]

Tonight's Ecm 12z op run emphatically rubber stamps the very unsettled outlook, I thought last nights 12z was unsettled but it has nothing on this, I think this run can be described as a locked in unsettled pattern in the making with high pressure to the east and out in the atlantic but the uk having low pressure in control for a change, and really no sign of the weather settling down again by T+240 hours either. quite the opposite in fact..so..turning progressively cooler & unsettled from the weekend onwards, very unsettled next week and probably beyond.

[damianslaw]

Strong agreement from the all models today of a major pattern change by the end of the week, a case of the cold pooling to our NW displacing itself over our shores with cold air advection heading our way and warm air advection both to our west and east heading northwards - a locked in set up for the trough to neatly settle over our shores and a very meridional flow - something we haven't seen hardly at all this year. Interestingly some of the long range model forecasts for the winter suggest a very similar pressure pattern...

 

Turning very windy in the NW as well, wet and much cooler for all, chance of wintry showers on higher ground in the north I would expect and localised frosts into next week.

 

Quite often lengthy settled spells come to a crashing end with something very different taking their place (mother nature finding an equilibrium..).

[bluearmy]

The week 2 Northern blocking that the GEM op was showing a few days ago looks like verifying and bringing the onset of autumn to nw Europe. Will be quite a shock in terms of precip and temps.

[Polar Maritime]

Yes well spotted, And a good call regarding GEM op's Blue.

Edited September 29, 2014 by Polar Maritime

[knocker]

The anomalies in much agreement with the blocking ridge in the western Atlantic with trough over the UK, Looking further ahead the pattern seems set to continue with a fairly weak meridional jet around a fairly slack Atlantic leaving most of the activity in the eastern section covering the UK. Thus a general area of low pressure looking relatively constant with unsettled weather and lower than average temps. It's a case of how to say the same as others with different words.

Edited September 29, 2014 by knocker

[sundog]

Some of the charts from todays output remind me a bit of some of the charts from early Oct 81 which ended up a rather cold month.

[Frosty.]

Some of the charts from todays output remind me a bit of some of the charts from early Oct 81 which ended up a rather cold month.

And Dec 81 was a very cold and snowy month,I hope history repeats itself :-)