Model Output Discussions 12z 03/05/2016

[wishingforsnow]

10 minutes ago, Nouska said:

I'm not aware of any hi-res output for that far ahead but he'll probably have access to more of the ECM suite than we do.

The EC32 was showing warmth for the last week of the month but as that run was initiated prior to the big swing in model output, it has to be viewed as suspect till the run next Tuesday.

This was central Europe on week two from the Thursday run - anticipating the pattern would include a warm UK in part.

This mornings EPS mean (day 15) has average 850 temps for the bulk of the UK and the Z500 is also looking to be the average north south divide - not seeing any indication of strong, warm ridging.

  MSLP spread day 15 

The big swing in model output for next week was due to the fact that the models had firmed up that low pressure was set to hit the UK in the next 7-10 days which was uncertain before but unfortunately looks set to be the form horse for next week now. Hopefully the next EC32 run and further model outputs won't see all prospect of hot weather returning for the end of the month eliminated especially as we'll be closer to the end of May by then. The jury is still out on that. 

Edited May 14, 2016 by wishingforsnow

[knocker]

1 minute ago, wishingforsnow said:

The big swing in model output for next week was due to the fact that the models had firmed up that low pressure was set to hit the UK in the next 7-10 days. Hopefully the next EC32 run and further model outputs won't see all prospect of hot weather returning for the end of the month eliminated. The jury is still out on that. 

I wasn't aware of any big swing in model output. The upper air has been fairly consistent regarding an Atlantic driven unsettled period for a wee while now. Given that upper air is the driiver the surface details will always vary from run to run and model to model until all is agreed nearer the time frame.

[Nouska]

13 minutes ago, knocker said:

I wasn't aware of any big swing in model output. The upper air has been fairly consistent regarding an Atlantic driven unsettled period for a wee while now. Given that upper air is the driiver the surface details will always vary from run to run and model to model until all is agreed nearer the time frame.

That's my fault - he was quoting me.

What I meant was that at EC32 initiation at 00Z Thursday, this was the day ten prognosis ....

.... just a couple of runs later, a very different picture emerged.

Edited May 14, 2016 by Nouska

[phil nw.]

There are suggestions that by day 10 the troughing over our locale weakens and the Azores high trying to ridge this way-the ECM  run seems keener on the latter.

at this stage it's all very tenuous though with the south as usual likely to benefit mostly if it does happen.In addition later gefs indicates it may only be temporary.Certainly more runs needed before we can look forward to any late month warm and settled conditions with any confidence i think.

Currently the mean outputs still show a reluctance for a general shift north of the jet to leave it free and clear for our Summer friend(Azores High) to move in.Still shallow upper troughing being shown around our neck of the woods.

Edited May 14, 2016 by phil nw.

[wishingforsnow]

8 minutes ago, phil nw. said:

There are suggestions that by day 10 the troughing over our locale weakens and the Azores high trying to ridge this way-the ECM  run seems keener on the latter.

at this stage it's all very tenuous though with the south as usual likely to benefit mostly if it does happen.In addition later gefs indicates it may only be temporary.Certainly more runs needed before we can look forward to any late month warm and settled conditions with any confidence i think.

Currently the mean outputs still show a reluctance for a general shift north of the jet to leave it free and clear for our Summer friend(Azores High) to move in.Still shallow upper troughing being shown around our neck of the woods.

Yes, it's still very much a question of whether the upper troughing will clear allowing the settled and warm/hot conditions to stick around for a while or if we will be alternating between periods of warm/hot weather and cool Atlantic wet weather with a troughing v Azores High battle. Though it looks to me like it wouldn't be too difficult for the troughing to be cleared as it doesn't look very strong. Taking into account the heat across Continental Europe and the fact that the cold pool in the Atlantic is smaller compared to last year, the Azores High shouldn't have as much difficulty moving North over the UK as it did last Summer.

Edited May 14, 2016 by phil nw.
Amended my quote

[Summer Sun]

UKMO and GFS show quite a difference at t144

[knocker]

The transition to some more settled weather is stil indicated around the 24th with weakening of the upper trough and some build up of heights adjacent to the UK. So a few days of drier conditions, particularly in the south, but it would appear to fairly short lived as more zonal set up is in place by the end of the run. Having said that I have no great confidence about which way this going to swing until there are some fairly consistent indications from all three anomalies.

Edited May 14, 2016 by knocker

[Tamara]

With official summer just over a couple of weeks away, a highly interesting stage of model watching is evolving for this coming period.

The last update referenced the likelihood of an atlantic westerly driven period of weather to follow the cool down from this weekends toppling northerly. The coming week has this in focus - changeable and quite unsettled from Tuesday. But for how long?

Extended ensemble data has appeared fickle (at face value) this week and has seemed to put back any prospects of improvement beyond the 10 day rolling forward period. However, as per last update, there was never any real indication of this happening till the last week or so of May at the earliest. This is actually more a case of the modelling being somewhat progressive with a signal and therefore giving the illusion of faster improvement than had been the case a week back

What of this signal? Long term extended means signals are very often the result of a strong tropical convection (MJO) component. And there is indeed such a very interesting signal driving the extended term at the moment - but more of that in a bit. 

Tropical forcing is only one part of the overall angular momentum budget though, and we must also consider the extra-tropical component.

Global torque tendency has dropped sharply negative from a high base at the start of the month. Partly because of the activation of tropical convection in the Indian Ocean but also assisted by a  -ve North American mountain torque (blue line on the chart below)  pulling atmospheric angular momentum down as reflected by the Global Wind Oscillation which has shallow orbited Phase 8 into Phase 0 in the last few days

The translation of this synoptically is the current retrogression of the pattern (as discussed in the last update).  As a consequence, an inability of the current toppling ridge to continue stretching north eastwards into UK and Europe beyond the early part of the week, and instead withdrawl westwards of the Azores High and the rather supressed jet streak programmed next week across the atlantic - with the trough dropping down towards the UK as advertised in the models.

Before the weather improves, we need to see the lagged effects of these negative torques flushed out.

The importance here, as detailed in the previous post, is that the base atmospheric state is still fully engaged with oceanic El Nino despite the on-going cooling occurring in the Pacific. Its noteworthy that the GWO continues to be keen to embrace high angular momentum 5/6/7 orbits, and that the decaying Nino signature continues to have its floor limit at Phase 8.

So with torques bottoming out, the way is up. And we have a strong tropical signal to help pull frictional torques upwards.

The models are currently hyper sensitive to MJO modelling.  There is a general consensus to take tropical convection eastwards erratically, but the problems are forecasting both the amplitude (which is currently quite robust) and the extent

.

 

We should bear in mind that MJO modelling is prone to vicissitude. I would not be taking any of these forecasts at face value.

That said, its still worth looking at the UKMO modelling though. Taking into account where the atmosphere/ocean coupling is right now - still firmly embracing El Nino, there is some credible chance that tropical convection will make its way eastwards through to Phase 5 and then perhaps 6. This is not what the modelling agrees on by consensus, but bearing in mind the extended ensemble means are wobbling around these predictions, any under estimation of forward motion and amplitude of signal is going to have continued proportionate size effects on changes within NWP. 

What is the significance of further eastward motion and amplitude of the tropical signal?

Essentially that the further eastward the signal heads, it, adds westerly momentum to the atmosphere which boosts AAM and creates northwards and eastward propagating Rossby waves from the tropics, which downstream act to spin up anticyclones at mid latitudes over UK and western Europe.

The extended signal is there in the models for some rise in pressure around and beyond the 10 day period. The further eastward tropical convection gets, the greater significance there is for the longer term - and not just a hoped for more settled spell to see out May and start June.

Coming into the start of summer on bolstered AAM - with the GWO attraction to Phase 5/6 cycles, promotes the establishment of Branstrator ridges (mid latitude ridges) strung out across Western Europe and the UK and into the Atlantic and some proper sustained very warm summer weather.

The longer that the atmosphere can keep embracing a weakening Nino signal, then shortening seasonal wavelengths strengthen the signal for a persisting GWO orbit through Phases 5/6/7.  Interestingly if any Nina-esque pushes associated with the cooling Pacific and Indian Ocean stage cycle of tropical convection can continue to be restricted, as at present, in terms of drops in AAM to a GWO flooring of Phase 8 - this will translate from the UK trough this phase teleconnects to at present, retrogressing westwards into the Atlantic the more time goes on towards the latter part of June. Clearly that would suggest warm air advection promotion on its eastward flank and sustained Branstrator ridges...

That is the best case scenario. The one for many summer hopes.

The alternative scenario whereby eastward amplitude is restricted and lost, will as a consequence lose AAM tendency momentum and restrict any settled warmer weather and return changeable conditions more readily. At present, natural caution and belt and braces approach from the professionals will support this hypothesis until clear evidence emerges in NWP modelling.

A good test for early summer signposts ahead though nevertheless. The current westerly wind push underway in the tropics has high significance as a test to the decaying Nino. A progressive push of westerlies, courtesy of tropical convection, towards the western Pacific earns a lagged effect on the atmospheric circulation that has its rewards in a decent first month at least to the season and postpones the threat of growing Nina type influences and the associated potential cooler and more changeable regimes gradually gaining greater frequency and the upper hand.

Edit: @Singularity - its the GWO orbit phases (as a whole representation of the AAM budget) that is significant in terms of translation to the synoptic pattern.  The tropical component composites in isolation are not reliable in that sense as you suggest  

Edited May 14, 2016 by Tamara

[Singularity]

Thanks as always Tamara 

Funnily enough I looked at the MJO for the first time in a while yesterday, and was struck by the wanderings toward phase 4, which correlates to a westerly regime in May, such as we see for next week, but a much finer, more settled regime for June, such as the longer range ensembles have been hinting at of late.

 

The ultimate scenario is, as Tamara has put across in great detail, a faster move right on to phase 5. Phase 5 looks great for May. Conversely, it looks a bit tragic for June, suggesting that a slow wander of the MJO would be a serious problem - but of course, these composites aren't adjusted for the influence of the El Nino atmospheric state on the AAM budget, so the composite can't be taken too seriously. The same goes for the others as well - but their general agreement with what Tamara describes is noteworthy.

 

 

Fingers crossed that the models (aside from UKME, which is usually way more keen for some reason) are underestimating the eastward progression of the MJO such as they have done often over the past year.

[stodge]

Evening all

For me, the big signal from this evening's 12Z OP output has been the return of northern blocking toward the end of the month. GFS has been playing with this option for a while and GEM has come on board as well while ECM admittedly isn't quite there yet.

The two options are stalling LP to the west or south west as we saw at the beginning of the week or a southerly tracking jet which of course wouldn't be such good news. I'm concerned at the apparent lowering of heights over Europe which would enable the trough to set up to our south and we all know how that ends..

 

[knocker]

Needless to say neither the ecm or NOAA are having much to do with building adjacent to the UK when this unsettled period comes to an end. that's if it actually does that is although certainly the rain and gales should ease a little.

In the 10-15 period the EPS has the trough mid Atlantic, more progressive than NOAA, and with the HP NW Russia we are looking at south westerly streamlines. So continuing changeable with the worst of the weather to the north and west, and more drier spells to the south with perhaps average or a little above.

Edited May 14, 2016 by knocker

[knocker]

Predictably we are looking at a pretty wet and windy week from Tuesday onwards with systems tracking in from the west. Next weekend rather depends on the track of the perturbation that currently is looking as if it might be running south of the UK but there is plenty of time for a slight correction to the track and it impacting the south. By the 24th the GFS is suggesting more influence from high pressure to the SW but here we are entering dog's dinner territory.

Looking at the 8-13 anomaly it is suggesting, and has been for a while. a cessation of the very unsettled period without any noticeable permanent build up of heights adjacent to the UK. We are still looking at a pretty mobile westerly.

Edited May 15, 2016 by knocker

[Summer Sun]

In the space of 24 hours UKMO has gone from a northerly to a westerly on Thursday still some rain or showers around but it wouldn't be felling as cold as it would have done with a strong northerly

Yesterday morning

This morning

 

[Polar Maritime]

Certainly a more unsettled period coming up than of late for the next 7-10 days at least, As has been well advertised by the GFS, And anomalies over the past week as posted by John & Knock. With a strong West flow turning N/W at times as Lows pass, Giving avg temps at best with bouts of rain crossing the country as fronts spill in off the Atlantic.

Edited May 15, 2016 by Polar Maritime

[knocker]

The ecm is bringing next weekends low straight into the south west.

[Gibby]

HERE IS MY LATEST ANALYSIS USING DATA SUPPLIED BY THE NWP OUTPUT COVERING 5 OF THE WORLDS MOST POWERFUL WEATHER COMPUTERS ISSUED AT 09:00 ON SUNDAY MAY 15TH 2016

THE CURRENT GENERAL SITUATION High pressure lies just to the West of the British Isles with a slack and slackening further Northerly flow across the UK

http://www.wetterzentrale.de/pics/Rtavn001.gif

CURRENT SNOW FORECAST AND/OR FREEZING LEVEL OVER THE UK The freezing level across the UK will remain near 5000ft across the far east to above 6000ft in the extreme West with a slow rising of the level in the East over the next few days while the highest levels over the extreme West falling back somewhat towards midweek.

http://www.snow-forecast.com/maps/dynamic/uk

http://www.natice.noaa.gov/pub/ims/ims_gif/DATA/cursnow.gif

MODELS-2 WEEK HEADLINE After a dry start becoming changeable with rain at times.

THE GFS JET STREAM FORECAST The current slack flow in the Jet Stream will align West to East and strengthen markedly by midweek as it surges East across the Atlantic and Southern Britain by the end of the working week. After spending several days in this form it breaks up and becomes anticyclonic around the UK for a time in the second week.

http://www.netweather.tv/index.cgi?action=jetstream

NEW GFS OPERATIONAL The New GFS Operational Run today shows the current ridge of High pressure weakening over the coming days as Low pressure moves in from the West with rain for all by midweek. The period following that will keep the weather unsettled for all with rain and heavy showers at times on a Westerly breeze as Low pressure is maintained to the North and later NE. Eventually pressure rises with more settled conditions developing, first in the South and then all areas later as High pressure builds strongly to the North of the UK again late in the run with Low pressure from Spain to the Med bringing the risk of thundery showers up from the South in rather warm conditions in an Easterly flow.

http://www.wetterzentrale.de/pics/Rtavn1441.gif

http://www.wetterzentrale.de/pics/Rtavn3841.gif

GFS CONTROL RUN The Control Run follows a broadly similar path with the main difference being the less extensive spread of High pressure across the UK in the second week, instead restricting any improvements to the South and East albeit temporary before more Atlantic drives in towards the North soon after with no real change in pattern shown until the final day of the run.

http://www.meteociel.fr/modeles/gefs_cartes.php?code=0&ech=144&mode=0&carte=0

http://www.meteociel.fr/modeles/gefs_cartes.php?code=0&ech=384&mode=0&carte=0

GFS ENSEMBLE DAY 14 DATA  The clustering today for day 14 shows us back to Low pressure domination over the UK in 14 days time with the exact patterning uncertain while only around 15% of members indicate a more High pressure based pattern with a centre close to the North.

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cpre&HH=372&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

UKMO The UKMO model this morning shows an unsettled spell developing for the UK this week starting from Tuesday as rain spreads East across the UK from the West later on Tuesday and is repeated again later in the week and extending into next weekend in association with low pressure centred to the North of Scotland.

http://www.wetterzentrale.de/pics/Rukm1441.gif

THE FAX CHARTS The Fax Charts show the slack High pressure ridge across the UK currently subsiding away South over the coming days as winds back westerly by Tuesday. Troughs ganging up across the Atlantic make their way across the UK towards midweek with rain shown for all followed by spells of sunshine and showers in a Westerly flow with further troughs in the flow too bringing longer spells of rain too in very average temperatures for mid May.

http://www.weathercharts.org/ukmomslp.htm#t120

GEM The theme of GEM too is for Low pressure to bring a change to westerly winds and rain at times towards midweek with further spells of rain and showers under a similar guise through next weekend before better weather develops in response to a reversal of pressure patterns to one of High pressure to the North and Low pressure to the South brings an Easterly flow back to the UK by Day 10.

http://www.wetterzentrale.de/pics/Rgem2401.gif

NAVGEM NAVGEM continues the well worn message printed above from the other models in that unsettled weather from the west returns to all parts of the UK by midweek culminating in quite a deep Low pressure across or near the UK over next weekend with rain and showers for all in average temperatures. 

http://www.wetterzentrale.de/pics/Rnvg1681.gif

ECM ECM today also shows the unsettled spell starting late on Tuesday with a period of 5-6 days of unsettled conditions with heavy showers and spells of rain in largely Westerly winds and near average temperatures. This run then shows a rapid change towards the middle part of the second week as High pressure builds rapidly from the South and settles just to the East with warmer and drier weather developing for many and probably lasting a while especially over the South and East. 

http://www.wetterzentrale.de/pics/Recm2401.gif

ECM 10 DAY MEAN (12z) The 10 Day mean Chart from ECM shows a favouring of Low pressure lying across the Atlantic and High pressure to the South and SE of the UK with a bias towards changeable weather with the best conditions likely towards the South and East. However, there is some other options from the other members which are inclined to distort the overall patterning of the Mean chart today.

http://www.wetterzentrale.de/pics/Reem2401.gif

NOTABLE TRENDS & CHANGES FROM PREVIOUS RUNS The theme from the models today continue to paint a more unsettled phase of weather to come before things become more uncertain thereafter.

31 DAY HISTORICAL VERIFICATION STATS FOR GFS, UKMO & ECM The verification Statistics of GFS, UKMO and ECM show at 24 hours ECM ahead at 99.5 pts with UKMO at 99.4 pts and GFS at 99.2 pts.  At 3 days ECM is leading with 97.3 pts to UKMO's 96.2 pts while GFS lags behind at 95.6 pts. At 5 days ECM leads with 88.6 pts to UKMO at 86.8 pts and GFS at 83.4 pts. Then at 8 Days ECM has the leading spot from GFS with 61.7 pts to 49.6 pts. Finally at Day 10 ECM has the lead from GFS with a score of 44.2 pts to 36.7 pts.

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day1_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day3_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day5_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day8_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day10_PMSL_MSL_G2NHX.png

MY THOUGHTS  Over the last few days the models have changed little in their interpretations of events likely across the UK in the next week. The further out in the outputs as usual the greater the differences and reliability become but moving forward from now it is fairly certain that after a few more days of fine and benign weather if rather cool at times it is likely to become unsettled from the West by midweek with rain followed by showers moving bodily East through the UK from the Atlantic. This theme is reinforced by further Low pressure later this week with next weekend too looking pretty poor for reliability of dry conditions with showers for many and probably still some longer spells of rain thrown in for good measure. The patterning becomes rather less well defined thereafter with some output bringing better weather up from the South and as happened in the most recent warm weather event some output shows this High pressure being sucked North to lie to the North of the UK while to the South pressure falls with a resultant warm Easterly flow developing again, this option shown by GFS and GEM. In the extended term taking us out to day 14 and using GFS Clusters at Day 14 as an indicator a lot of Low pressure is shown to be in control of the weather over the UK with just 15% of members showing any form of High pressure to the North while ECM at day 10 still likes the idea of High pressure closer to the South and East where the warmest weather would reside while the NW sees rain and showers in a SW flow. Given the rather poor verification stats shown above for GFS in the longer term of late I will side with the more likely option shown by ECM for day 10 meaning that after an unsettled period with rain at times for all pressure will build from the South in the second week with fine and warm conditions gradually spreading up from the South and East to more areas with time. So in the meantime lets enjoy the next few days of reasonable weather before things turn somewhat soggy for some for a week or so at least. Join me for another installment tomorrow to see if there is any change to the general theme. 

Next Update Monday May 16th 2016 from 09:00

[Man With Beard]

3 hours ago, knocker said:

Predictably we are looking at a pretty wet and windy week from Tuesday onwards with systems tracking in from the west. Next weekend rather depends on the track of the perturbation that currently is looking as if it might be running south of the UK but there is plenty of time for a slight correction to the track and it impacting the south. By the 24th the GFS is suggesting more influence from high pressure to the SW but here we are entering dog's dinner territory.

Looking at the 8-13 anomaly it is suggesting, and has been for a while. a cessation of the very unsettled period without any noticeable permanent build up of heights adjacent to the UK. We are still looking at a pretty mobile westerly.

Indeed knocker. The problem I see though is that the models are only building in weaker positive anomalies in the long term. These almost always seem to get eroded in the D6-8 period, perhaps because of a very slight prior underestimation of the Atlantic. I suspect we may have to go through another a full unsettled week after next weekend.

Edited May 15, 2016 by Man With Beard

[knocker]

The EPS this morning does have brief ridging on day ten but it's very short lived as it moves east and the Atlantic trough becomes more influential. This could easily result in the south having a few fine days with the more unsettled weather more prone to the west and north. And then as we get towards the end of the run the trough weakens and this rather indeterminate  zonal flow sets in. I'm still sticking to the opinion that the evolution in the latter stages is still up for grabs although the percentage play at the moment is not for any great build up of heights in the eastern Atlantic.

[knocker]

Given that the unsettled weather up to and including next weekend looks pretty much nailed on, albeit the details still to be finalised, focus is on how long the expected ridging adjacent to the UK will last, assuming it does occur of course, during next week.. Well things are looking optimistic looking at the 8-13 anomaly and even, heaven forbid tonight's ops run, for a few days of dry quite pleasant weather. Of course the next ops run could be completely different but if the ecm anomalies go along with this I shall remain optimistic.

[Summer Sun]

Once again t144 from UKMO and GFS offer 2 different options

[knocker]

The ecm anomaly tonight is not adverse to some temporary ridging next week as the upper trough to the north retracts. It is perhaps only temporary as the Atlantic trough nudges further east for a while before declining. So it's quite possible that next week could see some reasonable weather, more particularly in the south and east.

[knocker]

According to the GFS the next couple of days look fine until the first system moves in from the Atlantic late Tuesday. The unsettled for the next few days with low low on Saturday tracking NE to be 982mb norther Scotland by midday. Thereafter at the beginning of next week high pressure from the west becomes more influential. Question is will it stick around and for how long?

[knocker]

Further to the above the GEFS anomalies look promising for some more settled and warmer weather next week

[mb018538]

Well ECM throws a massive curveball in this morning!

GFS showing a 1035mb high to the west of the UK at 192 hours.
ECM showing a deep 990mb low in the same position at the same timeframe.

Talk about not having a clue what's going to happen!!

[I remember Atlantic 252]

12 hours ago, Summer Sun said:

Once again t144 from UKMO and GFS offer 2 different options

I certainly prefer UKMO option!, at least it will be mild! 21st May, can say that quote