Model Output Discussion 1200 hrs 30/09/14

[damianslaw]

Regarding GFS latest modelling - mmm I think it is just doing its usual today, throwing up various scenarios from run to run - usually a sign of uncertainty caused by background signals that don't necessarily favour a 'zonal' westerly set up, it often struggles in these kind of set ups where there is a possibility of height developments to the NW and NE and a complex trough development setting up shop over the country.

 

Reliable timeframe is relatively short at present - there is a strong likelihood of secondary low development early next week and the trough becoming unstuck over or just to the west of the country - this would aid warm air advection into scandi and no doubt stronger heights to our NE which would have the effect of preventing the trough from moving eastwards, all eyes then on where the jet decides to position itself , whilst such developments would certainly be conducive in moving the trough back NW and allowing azores high to ridge NE again, equally a more southerly positioned jet as forecast would enable strong heights to develop to the NW and force the trough to move SW leaving us exposed to a easterly or northerly source of air..

 

A lot going on at long long last - after a lengthy period of little 'weather activity' - if there is a month for enthusiast weather model watchers to hibernate it is always September!

[Summer Sun]

ECM has problems this evening so the update will be later than normal

 

EDIT

 

Problem fixed 12z run almost complete

Edited October 1, 2014 by Summer Sun

[IDO]

Clearly the latest GEFS update hasn't read the memo about this being brief, especially for the West!

 

 

Yes the hi res are only garnering about 25% support amongst its members:  

 

The MJO going for high amplitude , moving from stage 6-8 during October: 

 

The composites are as follows:   

 

Those are for all amplitudes; the >1 amplitudes show stronger above height anomalies, e.g. phase 8: 

 

This could be the signal why CFS is modelling higher heights and maybe why GFS hi-res runs are moving in that direction? ECM has flipped from this morning's trough at D10 to tonight at D9 when heights are building in again:

 

 D10:  

 

A move towards GFS...

[Summer Sun]

After ECM's problem its now updated and after a late start Autumn is set to arrive from Saturday with low pressure taking temperatures should be around average though with stronger winds and some rain it will be feeling cooler than of late.

 

 

Towards the end of next week the low begins to move away and we may begin to see things improve from the south as pressure starts to rise

 

[knocker]

Tonight's anomalies have the blocking HP in the western Atlantic weakening although strong enough  for the GFS to retain surface HP and a fairly inactive Atlantic with the trough still established in the east giving low pressure and a generally unsettled outlook. THe ECM has a variation with the trough more centrally orientated vis a vis the Atlantic and it goes on to develop this theme with the HP block dissolving and low pressure dominating the Atlantic with a zonal jet, albeit not that strong. Need to watch how this develops.

 

[johnholmes]

 

 

This could be the signal why CFS is modelling higher heights and maybe why GFS hi-res runs are moving in that direction? ECM has flipped from this morning's trough at D10 to tonight at D9 when heights are building in again:

 

ECM1-216-15.GIF  D10: ECM1-240-19.GIF

 

A move towards GFS...

an interesting post there

[johnholmes]

re the anomalies, all 3 show similar ideas in the 6-10 day time scale and NOAA has done this for at least 3 days now. A similar consistency also in its 8-14 day outlook.

Some thought provoking posts above this as well. I do enjoy reading this type of post so much better than the hype we are almost certain to get come  the winter frenzy.

Edited October 1, 2014 by johnholmes

[Frosty.]

I'm looking forward to the winter frenzy and the very unsettled outlook next week with the PFJ to the south of the UK at long last..yipee :-)

[Due South]

Looks like things settle down again buy the end of next week.

[Captain Shortwave]

Still looks unsettled next week with showers or longer spells of rain at times. The worst always the further north and west you go. Still a question mark regarding the end of next week as heights might try to rebuild over Europe, it should turn drier and warmer from the south east. How far could this progress.

[knocker]

I can see where you are coming from Captain. The ECM is pushing this but not GFS and last nights NOAA wasn't that keen. The ECM is tending to push the trough further west which could accommodate increasing heights from the SE

Edited October 2, 2014 by knocker

[Gibby]

HERE IS MY LATEST TEXT ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY THURSDAY OCTOBER 2ND 2014.

NEXT UPDATE FRIDAY OCTOBER 3RD 08:00

 

THE CURRENT GENERAL SITUATION. An active cold front will edge SE across the far NW later with a strong to gale SW flow affecting the North ahead of it. A ridge of High pressure will be maintained across Southern Britain for the time being.

 

MODELS-2 WEEK HEADLINE  All areas look like being unsettled and windy with rain at times in cool conditions. Possibly a little drier and less cool in the SE later.

 

THE JET STREAM ENSEMBLE FORECAST A change in the position and orientation of the Jet stream is expected soon as it transfers SE to lie in a position from Greenland or Canada, across the Atlantic and over Southern Britain through next week and probably beyond.

 

GFS The GFS operational this morning shows Low pressure in control of the weather across the UK over the coming couple of weeks as a deep centre drifts SE towards Western Britain and carrying troughs of Low pressure with wind and rain across all parts next week. Longer term improvements shown are slow this morning with further Low pressure and cool, rainy weather under further Low pressure coming up from the SW especially across the South before finally High pressure pushes a ridge across the UK from the East at the end of the period with a direr and brighter if cool interlude.

 

THE GFS ENSEMBLES. The GFS Ensembles remain supportive of it's operational through Week 1 with Low pressure close to northern Britain keeping things windy and wet at times next week with only slow improvements in Week 2 as a temporary ridge passes East ahead of further deep Low pressure across Britain to end the run in two weeks time.

 

UKMO UKMO this morning shows a deep Low pressure area having slipped SE from the NW to lie in a position close to Western Britain with basically SW winds and spells of rain and showers dominant across the UK through the first half of next week at least.

 

THE FAX CHARTS  The Fax Charts show an active and squally cold front crossing SE over the UK over tonight, tomorrow and Saturday with squally winds and heavy rain for a time. A ridge is then shown to give a quieter interlude across the South briefly before Low pressure moves down from the NW with active troughs crossing east and SE over all areas to start next week.

 

GEM The GEM operational brings unsettled, often windy and wet conditions across the UK next week as Low pressure becomes deep and extensive close to or over Northern Britain with any improvements very slow as it only edges away slowly to the NE later filling slowly with further showery rain and quite cool conditions lasting all the way out to day 10.

 

NAVGEM NAVGEM today is little different to the other output all supportive of a deep Low close to NW Britain delivering spells of rain and showers across the UK in blustery Westerly winds through the week and probably beyond.

 

ECM The ECM operational maintains the basic theme of all other output in bringing a deep Low down towards and probably to the West of the UK next week with rain and wind at times for all. With the thrust of Low pressure slightly further West and lifting out North of the UK later as well as filling it does hold the chance that temperatures would be quite mild at times across the SE and holds a chance that rather less unsettled conditions could develop across the South and East with time.

 

NOTABLE TREND CHANGES FROM PREVIOUS RUNS There is no change in the trend towards much more cyclonic based weather holding firm across the UK for all of the output term this morning though any marked improvements hinted at from some output longer term is more restricted to ECM this morning.

 

MY THOUGHTS  Low pressure is going to become the driving force of the UK weather over an undetermined time destiny this morning. The main thrust of Low pressure will arrive early next week from the NW, this following a brief but active transitional cold front finally ending the warm and static conditions the South of the UK have seen for so long with some heavy and squally rain. Once the main thrust of Low pressure arrives early next week it will be cool and windy with spells of rain or showers for all, some heavy. Longer term we still have embryonic signs of a pressure rise from the SE again in week 2 bringing drier, brighter and relatively mild weather back into the South and East later but this is a little more tempered this morning by the chance of further Atlantic Low pressure coming back in from the West later, shown by the GFS Ensembles and more restrictive to the extreme SE from ECM. So all in all a much more seasonal feel to things is just around the corner with the wind and rain accompanied by lower temperatures culminating together to produce quite a shock to the system for many, especially those living in the South.

[Polar Maritime]

A real contrast in Temps as the Cold front pushes S/E on Saturday. With some locally heavy Rain and strong winds.

 

[IDO]

I can see where you are coming from Captain. The ECM is pushing this but not GFS and last nights NOAA wasn't that keen.

 

 

Last night's NOAA was based on yesterday's 0z and 06z and this was only picked up by GFS and ECM on the 12z. The hi res GFS are picking up this signal:

 

 

The 8-10 day mean tentative improvements from the SE: 

 

But it is not convincing yet. However all three main models are now backtracking on the runs of a few days ago that suggested a rather stalled LP system close to the UK. They are now suggesting around 3 days influence for the S/SE before the Low retreats N/NE. We then have a transitional period where HP tries to edge in and the slack upper trough meanders east. D10 charts:

 

 

 

An improvements of sorts, especially for the south.  GEFS showing several clusters after D10 so all just guesswork from then, though the return of higher pressure still with good support:

 

 

I know October can be important as to how Winter develops so some interesting weeks ahead.

[Summer Sun]

The most unsettled spell of Autumn coming up from tomorrow / Saturday with wind and rain becoming the main feature for most of next week, later on in the week we do have some hints again that things could settle down for a time from the south as pressure try's to rise

 

 

In the short term we have some heavy rain which will be moving across the country during tomorrow and Saturday which could be torrential in places

 

[knocker]

But is this signal transitory ido? A case of watch this space I feel.

Edited October 2, 2014 by knocker

[Summer Sun]

The NAO looks like reaching its most negative point since mid August in the next few days

 

[No Balls Like Snow Balls]

Between 1.5" & 2" of rain could fall in parts of the North between Friday lunchtime and Midnight Sun according to both the UKMO & GFS.

[johnholmes]

Between 1.5" & 2" of rain could fall in parts of the North between Friday lunchtime and Midnight Sun according to both the UKMO & GFS.

ukmo.gif

gfs.gif

 

interesting that two totally different models are relatively alike for amounts and areas predicted to be affected.

[IDO]

I mentioned that October H500 correlates well for the upcoming winter re AO. This is shown through the October Pattern Index (OPI) and can be monitored on the below link. The final figure will be at the end of the month. For "coldies" the more negative, the better chance of a weaker PV.

 

Link: http://app.til.it/opi/

 

Latest JMA for week 2:   Week 3-4: 

 

Looking like trough driven for the next few weeks with the chance of maybe a drier interlude for the E/SE. Looking worse the further west you are for rain. However the models are showing some uncertainty, so no definitive conclusions at the moment. For instance the mean at D8 tonight:

 

 Is a bit quicker than the 06z mean to push the mean Low north: 

 

Expect lots of changes in the GEFS FI in the next few days.

 

 

[SteveB]

Well tomorrow looks like the last decent day for what might be until next Spring.....

 

Wet and windy for most next week & into FI

 

 

There are drier periods in-between the rain, but an unsettled picture is being painted by GFS tonight.

[Captain Shortwave]

ECM still showing the rebuild of heights over Europe

Low pressure setting up west of Iberia with warm air trying to pile northwards.

GFS and GEM also try to place the trough in a similar position, but the surface detail is a little more unsettled than the ECM, especially in the east where the ECM shows some improvement in this regard.

Given the longwave pattern, there is potential for a very late in the day plume event if the pattern slackens off enough.

Edited October 2, 2014 by Captain shortwave

[Frosty.]

Tonight's GEFS 12z mean shows autumn as it should be with temperatures returning to normal, give and take a degree or two but because it's been so warm in the last 4 weeks, normal is going to feel cold, especially when it's accentuated by strong to gale force winds, and rainfall should return to normal so all our gardens should get a good soaking, however, as ever there will be regional variations and it's generally the northwest of the uk which looks most unsettled throughout the next few weeks with persistent lower heights to the NW. We are all going to see spells of rain and strong winds but the SE corner of the uk looks like having the best of the drier, milder and brighter weather between depressions with lighter winds and in the southeast it's likely to be pleasantly warm at times with pressure rising a little from time to time from later next week due to the ebb and flow of the european anticyclone,  eventually an increasing risk of overnight fog and chilly nights when the calmer condtitions occur, but nowhere is immune to wind and rain next week, it looks particularly unsettled during that period, again, especially for the n & w but beyond that, the worst of it is likely to be across more western and northern areas..autumn is finally here.

Edited October 2, 2014 by Frosty.

[ANYWEATHER]

The late summer warmth goes out with a bang tomorrow with a Big full stop behind it!  Ouch! for all of us on Saturday as cold air arrives .A big welcome to  Autumn by then , Just look at the difference between the air mass a 10 degree difference,..... and for the rest of the outlook , you may as well watch your washing merchine  doing its cycle!!!    

Edited October 2, 2014 by ANYWEATHER

[Polar Maritime]

Yes another very unsettled and cool/cold run from the GFS. As has already been said, Some big changes on the way over the next few days with rain and gales spinning in off of the Atlantic from a cool N/W flow. I think we will continue see lot's more chopping and changing out in the runs, As the Models get a grip of the up-coming pattern change. Some -4 850s showing clipping the far North out in the run.. Very interest Model watching indeed.

 

  

Edited October 2, 2014 by Polar Maritime