Model Output Discussion 1200 hrs 30/09/14

[phil nw.]

ECM longer range ensembles showing high pressure anchored over Europe for the next couple of weeks. Beyond that, although suggesting a cool down, it's only back to more average conditions.

Yes ECM mean at D10 ht anom and 850 temps

 

 

a little warmer for us,by day anyway but chances of frost and some fog night times under any slack conditions.Conversely note the cold  to the east over Scandinavia/Russia .digging well south by that time.

The lowest polar heights being modelled around Siberia and with the Atlantic flow quite sluggish this may well be a period where the cold pool further east starts to establish.

[Newberryone]

Looking at the Jetstream forecast it does look like next week will see a slack set up with atlantic trough action never fully getting in on the act allowing for stronger heights to dominate - frost and fog could be a strong feature.

Stronger heights to dominate further east maybe, but still these charts would suggest sufficient Atlantic trough action to eventually bring high enough precipitation to Ireland.

[knocker]

The ECM and GEFS anomalies are in pretty much agreement at D10.  Cold pool Russia/Siberia, ridge just to the east of the UK and western Atlantic with the dominate feature regarding the UK a low to the south west. NOAA 6-10, 8-14 are in transition from next week and the dominant east Atlantic low. With regard to the ECM and GEFs the surface analysis is slack low pressure in the eastern Atlantic. In fact there isn't any indication of a more dynamic Atlantic with a weak jet that is slightly meridional according to the ECM and the GFs has it split anyway.

 

[Nick F]

Intriguing the difference between GFS and ECM in their 12z output next week. 12z ECM deter has quite a bit of support from its EPS for a deep low moving NE from Biscay across S/E England Monday, around 50%, with support form JMA and GEM too. Whilst UKMO and GFS are shallower and track low further east across France/Low Countries:

 

 

Then, as others have said, the differences widen with ECM indicating low pressure muscling back in from the Atlantic, while UKMO and GFS build pressure down from the north. Be interesting to see which way this goes.

[knocker]

The GEM is quite similar at D10 in going for a slack low pressure over the Atlantic with HP to the east. A case of being poised waiting for something to give. I blame the Pacific cyclones and the PV naturally

 

 

[Nick F]

18z GFS seems to have gone more 12z ECM's way with Monday's low - taking it further west and bringing heavy rain north across much of England and east Wales during the day.

[Man With Beard]

Intriguing the difference between GFS and ECM in their 12z output next week. 12z ECM deter has quite a bit of support from its EPS for a deep low moving NE from Biscay across S/E England Monday, around 50%, with support form JMA and GEM too. Whilst UKMO and GFS are shallower and track low further east across France/Low Countries:

EPS96.gifEPS120.gif

Then, as others have said, the differences widen with ECM indicating low pressure muscling back in from the Atlantic, while UKMO and GFS build pressure down from the north. Be interesting to see which way this goes.

It's well worth keeping a eye on this Monday low - with it originating near Portugal, plenty of warmth in tow and deepening quite quickly near us, I smell some torrential rain being involved.

Bigger picture, a weak jet in October is very interesting, isn't it often at its strongest around now?

[Polar Maritime]

The GFS is showing a very unsettled/cool end to the run, With Lows spilling in off the Atlantic bringing heavy rain and strong winds.

 

[knocker]

Yes I was just thinking the same PM. The trough mid Atlantic on the anomaly chart seems to be having some influence and the jet has a bit more oomph.

 

Regards the low mentioned by rjbw above the GFS has it 998mb English Channel at 00z Monday with a wet southern England.

 

 

 

Edited October 10, 2014 by knocker

[Summer Sun]

ECM showing an increasingly settled run for for England and Wales this morning and warmer for all

 

Edited October 10, 2014 by Summer Sun

[shaky]

ECM showing an increasingly settled run for for England and Wales this morning and warmer for all

 

also has sunday night/monday mornings low further east now!!!

[knocker]

also has sunday night/monday mornings low further east now!!!

 

Yes slightly more NE than the GFS

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY FRIDAY OCTOBER 10TH 2014.

 

NEXT UPDATE SATURDAY OCTOBER 11TH 08:00

 

THE CURRENT GENERAL SITUATION. An unstable and slackening SW flow covers the UK over the next 24-36 hours.

 

MODELS-2 WEEK HEADLINE  Changeable weather with rain at times and strong winds too later but with some dry and bright weather for some next week especially in the East.

 

THE JET STREAM ENSEMBLE FORECAST The Jet Stream in this morning's GFS Ensemble run shows the flow remaining generally South of the UK although quite weak at times over the coming three to four days. It then strengthens somewhat all the way down over Spain and Southern France before slowly migrating North across the UK for much of week 2 and possibly further North still right at the end of the run.

 

GFS The GFS operational today shows relatively slack areas of low pressure dominant across and around the UK in a slack airflow over the coming 4-5 days. This means showers or rain at times for all with some dry and bright periods too when mist and fog plus some frost patches occur overnight with a rather cool feel developing generally. Then deeper into next week milder Southerlies develop as an Atlantic Low moves in closer to the west with rain and fresh winds becoming commonplace for many in the west and North extending East with time. This then sets up a potentially stormy spell late in the run with deep Low pressure near NW Britain steering periods of rain and SW gales across all areas at times to end the period.

 

THE GFS ENSEMBLES. The GFS Ensembles are quite harmonious to the operational in theory this morning though the differences at the surface could be more marked in Week 2. It, as the operational suggests a spell of quiet and unstable conditions with rain at times in cool weather lasting into the middle of next week but then holds High pressure closer to the SE of the UK which in turn focuses more dry and potentially mild weather for these areas as a Southerly airflow develops. The slower advancement of the deep Atlantic Low  to the west by then is also indicative of less wind and rain than the operational shows and subsequently shows less deep Low pressure late in the run mainly affecting the North and West with rain while the South and East stay mainly dry, bright and mild.

 

UKMO UKMO this morning shows  a ridge of High pressure extending South across the UK from the North midweek with dry, bright and rather cool weather with mist, fog and frost patches quite extensive at night. The SW will become cloudier with some rain by Thursday's end of run chart as a deep Low to the west extends it's influence slowly East.

 

THE FAX CHARTS  The general thrust of the Fax Charts follows the raw data quite closely with a small but active low near the SE on Monday possibly delivering some copious rainfall and cool weather for a time early in the week before the cool ridge from the North takes hold midweek.

 

GEM The GEM operational today shows slack Low pressure in control over the coming few days with further rain and showers at times before a small but active area of Low pressure affects all of Southern Britain early in the week. Once this passes a quieter few days are followed by milder  Southerly winds as a deep Atlantic low makes slow progress East. Rain will then edge West to East slowly across the UK to set up a windy SW dominated airflow by 10 days time with rain and strong winds at times, heaviest towards the North and West.

 

NAVGEM NAVGEM also brings this troublesome small Low up across Southern Britain at the start of next week with a spell of cool rain for many in the South before a ridge behind it settles things down for a time. Then as winds settle South or SE rain will edge in from the West in association with a deep mid Atlantic Low. This appears to set up a milder period under SW winds and rain at times to end the run as a troughs moves slowly NE across the UK. 

 

ECM The ECM operational today brings a similar sequence of events in the short and mid term of it's run but then goes the opposite way to GFS and indeed much of the other output in ridging High pressure up across Southern and Eastern Britain in a week or so with fine and warm weather affecting England and Wales by next weekend in balmy South or SW winds.

 

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The trend is still showing a conflict of interest in whether Low pressure to the West and North overcomes the power of High pressure to the SE in the longer term outlook this morning.

 

MY THOUGHTS  The synoptic long term outlook is no more clear this morning as the models struggle to deal with the effect of the mid Atlantic Low next week and how it determines the events of weather over and around the UK thereafter when coupled with the anticipated rise of pressure over France and Europe later next week. Most output and particularly GFS keep the Jet flow well South and powers up some big storms later which would bring rain and gales for all but this is less marked within it's ensembles. It's hard to see where UKMO would take us given it's relatively short model run span with GEM and NAVGEM offering a somewhat half-way house between GFS and the more interesting ECM operational today. Should the ECM operational verify then Southern and Eastern Britain will receive unseasonably warm temperatures with dry conditions prevailing under the Southerly breeze with the Atlantic Low pressure much weaker and held well at bay for the time being. It will be interesting to see where the operational sits within it's ensembles released at around 09:30 but I wouldn't mind waging a bet it is on the better side of the pack with the most likely scenario ending up more akin to being something like GEM but we will see. So having said all that and to summarise it looks like next week will start cool and wet in the South before all places see a quieter and perhaps misty and/or frosty risk midweek before a slow transition to milder and perhaps wetter weather extends slowly East across the UK late next week with Week 2 then being in the land of the gods ranging between potential gales and heavy rain and mild and dry in the South and East. As always more runs are needed but I think we can safely say that no early wintry shocks to the system weather-wise look like occurring over the coming two weeks.

[carinthian]

Morning all, not sure how the UKMO computer will handle the low on Sunday. I have a feeling there will be changes later today in the track. Could move on a more Nly course before exiting into the North Sea. If this were to be the case, more rain over Northern England than presently expected with a cold day on Monday. Into next week the Atlantic low deepens to about 940mb with a large circulation but not going anywhere fast. Obviously, this will affect our weather as next week progresses. The form horse will be a switch to a warmer southerly flow, probabaly drier mid week for most but the strength of the ridge to the NW may alter things with a stronger push of colder air into Scandinavia.

 C

[Nick F]

So, the GFS appears to have edged more towards ECM overnight with regards to more influence from Atlantic low pressure later next week, as fronts spread rain in from the west by Thursday. The trough over the Atlantic shows signs of stalling and amplifying to the west on both models in the medium range, ECM has more ridge influence over the UK than GFS - so could turn warm again given the deep southerly flow:

 

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

 

But, still uncertainty over Monday's low, with ECM taking the low further east across N France and into the N Sea, similar to last night's GFS, while GFS this morning seems to copy last night's ECM by taking it NE further west. Potential for some very heavy rain with this low, with warm moist air being drawn into its circualtion as it moves NE across Bay of Biscay/Wern France.

[shaky]

Yes slightly more NE than the GFS

hopefully means most of the heavy rain stays in the north sea!!

[knocker]

A glance at the ECM weeklies.

Edited October 10, 2014 by knocker

[Newberryone]

 As others have highlighted, the latest ECM op certainly painting a very different picture today with a far more robust euro block in the later stages. It would appear that only parts of Northern Ireland and Northwest Scotland would receive anything noteworthy in terms of rainfall should these verify. As ever, more runs needed I suspect.

[Frosty.]

The GFS 06z op run shows the current slack pattern with sunshine and sharp showers continuing this weekend with pleasant warmth in the sunshine but dropping several degrees in the downpours with a risk of thunder, there is then trough intensification by monday with more persistent rain for southern uk for a while. brighter and cooler with a few showers further north but then from midweek onwards, we start to see growing influence from a deepening atlantic low pushing NE and bringing breezier conditions with cloud and rain north and east along with progressively milder air, indeed, by the end of next week the 6z shows 564 dam thicknesses flirting with the south and a plume of warmth from france extending up across the uk for a time with temperatures soaring into the low 20's celsius across the s & e with the SE in particular enjoying a window of very warm and sunny weather for a time but then once that warm airmass has been shunted away eastwards, temperatures return closer to the mid / late october average with atlantic systems pushing into the uk. The 6z is a rather unsettled run overall but good potential is there for a short but noteworthy late summery burst across more southeastern areas by the end of next week. 

[knocker]

The 06Z GFS has the low 18z on Monday centred about Chichester 1000mb and wet over England and Wales. By 06z Tuesday over Norfolk 1002mb.

[nick sussex]

I think it could be a case of some unseasonable warmth for the UK followed by an eventual big drop in temperatures towards the end of October.

 

With the PV still showing no signs of gaining strength we could possibly see high pressure transferring further north with time.

[Polar Maritime]

Yes Nick, As you say with the latest GFS run continuing to show a disrupted Vortex towards the end of October. As ever with blocking, Struggling as to where the High Pressure pumps North.

[IDO]

Still lots of uncertainty for whether we are under the influence of a trough or ridge around D8-10. The GEM op was trough based for the UK but the GEM Control is more like ECM:

 

Control at D10:   

 

The GEM mean reflects the split in the ensembles, about 50:50:

 

   As does the ECM mean: 

 

So long wave differences as to where the meridional flow rests and also short wave variations with regard to the potential LP system in a few days time. Of course the latter may well have a direct correlation with the D10 outcomes in the ensembles.

 

Not discounting GEFS re the uncertainty, just looking at the pressure graph for London on the 06z sums up the scatter: 

 

Looking like a few more runs to see how the models resolve this.

Edited October 10, 2014 by i'm dreaming of...

[knocker]

The ECM progression of the low on Monday. No sign of dragging warm air up then or post journey.

 

[Captain Shortwave]

All models tonight are showing a new disturbance moving south east from Newfoundland into the Atlantic, this destabilises the trough and hence the ridge developing ahead of it. Simply put, that Euro ridge has been scuppered somewhat.

ECM

Other models are similar in this, this low wasn't on any of the models a day or so back. This suggests a bit more gusto in the Atlantic jet than first anticipated.