Model Output Discussions 12z 03/05/2016

[Man With Beard]

Anyone else thinking we might as well suspend this thread for a day or two? Or rename it the "Model Confusion Discussion"? Such is my level of confidence in the model output this morning. The lack of Atlantic activity together with weaknesses in Euro heights results in a cocktail of small, unstructured and unguided disturbances floating around Western Europe by the end of the week. Placement differences of just a couple of hundred miles will mean vastly different localised ground-level conditions. Taking the UKMO/GFS/EURO for Sunday morning:

This, the UKMO, is probably the simplest, and that's not very simple. Probably an easterly for the south (which might be very good for S/W coasts and Wales) and variable winds further north. Possibilities of fronts both to the south and north, but could also stay dry. Warm continental air knocking on the door of the south. Not really sure what comes next - probably high pressure building in from the west but there could also be various splits/convergences of troughs, so low confidence

On to the GFS, and the problems really set in. On the one hand, heights are building to the north and seem to be heading west. There's the tiniest hint that heights are also trying to build mid-Atlantic, which may cut-off the low next to Iberia completely and lead to a NEly shortly after. Heights are building north from Italy and might combine with heights north of Scotland or from Russia, depending on how the disturbances over S England and Norway develop - disturbances so small that anything could happen really (this is born out in GEFS ensembles which by T216 have heights all over the place). The likeliest scenario from this chart is that two areas of heights with establish, one north and one south of the UK, with a trough sandwich through the middle and the UK eventually affected by it - so an unstable Bank Holiday Monday, though still with some lucky places seeing sunshine and low 20s, maybe even mid 20s

Finally the ECM at T144 - this is more of an abstract work of art than model output, so many curves and kinks and highs and lows ... so I'm not even going to start trying to assess where it would go next as I haven't got a clue. And be honest - neither have you.

Edited May 23, 2016 by Man With Beard

[Nouska]

  That sums it up well @Man With Beard

 

38 minutes ago, Man With Beard said:

disturbances so small that anything could happen really

.... and therein lies the problem - longer range output not able to identify these 'polka dots' of upper troughing. 

Cannot remember which year it was when a similar thing occurred - all mid/longer range output was pointing to a nice high pressure situation over most of the European view but as time got nearer, these little disturbances appeared and continued to meander around.

[stodge]

Afternoon all

Yes, the 06Z GFS OP plays the blocking game pretty well and with the LP spinning up from the south and deepening as it does, we might get away with a fair Bank Holiday but next week isn't looking too clever especially for England.

Even FI provides little or no relief - only at the furthest reaches does the LP over northern Siberia spin west across the Pole toward Greenland hinting at a lowering of heights but that's an eternity away. 

 

[knocker]

Can''t say next week looks to bad to me on the 06 but then what do I know?

[phil nw.]

Yes it's getting to the time of year where the jet is much weaker around the hemisphere and often segmented.As Singularity pointed out much weaker thermal gradients from north to south with the warmer Arctic these days.

A look at the 006GFS T96hrs as an example  

As been said earlier ill defined wave lengths and cut off shallow upper cold pools make pinning down surface detail more difficult.A very slow moving pattern and split in the jet with as much energy going south into Europe.Therefore the tendency for lower pressure across the near continent and higher to the north as we head through to the BH period.

GFS/ECM means at T168hrs

A trend to a slack easterly pattern perhaps and the south more likely on the face of it to see rain/showers at times although it may be best to follow the fax charts at closer range to best view surface features.

 

 

[knocker]

The latest GFS det illustrates the foible of reading too much into individual runs. The 12z has a far better outlook for the weekend and following day or two than the previous run. Of course the next run could well backtrack but I'm a little more optimistic except perhaps for eastern parts late on. Having said that the GEFS are still pretty solid post BH

Edited May 23, 2016 by knocker

[knocker]

Of course having said that the ecm is still looking to track the depression north into the Netherlands next Monday and then sharply west bringing a very wet day to the UK on Tuesday. More runs needed. I've always wanted to say that.

Edited May 23, 2016 by knocker

[mb018538]

Gale force winds and a washout bank holiday on tonight's ecm!

[Summer Sun]

16 minutes ago, mb018538 said:

Gale force winds and a washout bank holiday on tonight's ecm!

Looking at ECM the far north may get away with a half decent weekend different story further south

Windy at times yes but not gales not a total washout either

Edited May 23, 2016 by Summer Sun

[knocker]

8 minutes ago, mb018538 said:

Gale force winds and a washout bank holiday on tonight's ecm!

A slight exaggeration. A fairly light NE for most but a little stronger in the east and south east. Dry for everyone except the extreme east and south east with the rain spreading west and north by 00Z Tuesday,

[mb018538]

Ok maybe a slight exaggeration...but pretty windy for the time of year none the less. It'll be interesting to see the finer details emerge nearer the time, low pressure from the south is always a different ball game to the west.

[Singularity]

36 minutes ago, knocker said:

Of course having said that the ecm is still looking to track the depression north into the Netherlands next Monday and then sharply east bringing a very wet day to the UK on Tuesday. More runs needed. I've always wanted to say that.

Oops - too used to the usual west-east progression I expect. That low moves sharply west rather than east, which of course is very unusual - so I'll let you off for that one Knocker 

I'm watching for any upgrades to the ridge north of that low, which could serve to hold it further south and bring much of the UK a blast of warm air from the east - even if it is with rather strong winds! ECM wouldn't have to go much further with it, but GFS has a fair away to go; even after the recent update it still seems to be generally less keen on height rises northeast of the UK.

There's also the fact that these lows are often overcooked a bit when beyond 5 days range - though I hesitate to rely on such a tendency. If it does get adjusted to something weaker, that too will help it to stay further south. Fingers crossed we can at least keep it to the east of us until the long weekend has been completed.

[knocker]

Cheers for that. I have actually being doing that quite a lot lately. My senility is more advanced than I suspected.

[knocker]

Pretty fair agreement between the NOAA and ecm 6-10. According to the ecm mean the surface low doesn't actually get further west than the Netherlands on Monday but as it's very slow moving the UK, particularly the eastern half, remains under it's circulation for two or three days.

Thereafter in the 10-15 period ridging up to Iceland is the order of the day so quite pleasant period with temps a little above average, The EPS is not a million miles away from NOAA.

[northwestsnow]

GFS just not letting go with this trough and attendant high latitude blocking thereafter.

UKMO looks better at 144 so the hope is thats closer to the truth.

Either way its looking far less rosey as we head into June than it did 2 or 3 days ago, GFS 0Z is actually horrendous,the trough just hangs around like a bad smell.

[knocker]

A glance at the latest EC32 update

At 00z Tues sees the upper low to the south east with the surface low Northern Germany so the eastern UK still within the NE circulation of same. The detail for the weekend best left to the other models.

For the next week until June 8th high pressure to the north and ridging from the Azores is the order of the day so a dry spell with temps a little above average.

This then breaks down into a more zonal regime with the normal interplay between LP to the  north and the Azores HP to the south with perhaps in the latter half of the month the Azores HP becoming more influential. I wouldn’t read too much into this as it’s pretty broad brush taken from the means but as it stands not looking too bad for June.

 

[knocker]

At the moment the ecm is going for a reasonable BH weekend but from 00z Monday it is still bringing the low over Germany WNW ( definitely not ENE ) in the next 48 hours bringing some very inclement weather to the southern half of Britain Monday/Tues. This is still along way from being a done deal.

 

[Singularity]

Yes - the retrograde low continues to be advertised by ECM.

This is helped along by HP focused NE of the U.K. With GFS this process is not achieved due to HP being focused more to the NW of the UK and effectively trapping the low over the southern half of Britain. The way it just sticks around for days on end is somewhat distressing so it's good to see UKMO looking more akin to ECM as of +120 (I can't seem to access the sources that go to +144 on my phone).

The ECM run is actually fascinating - the way the blocking combines with the shallow trough to the south to feed in quite warm air with some instability across the south, most settled across the north - and probably very warm in western Scotland much as it was on a number of days the week before last.

[mb018538]

Looks potentially quite miserable for my neck of the woods from Monday onwards - and the GFS in particular just holds the trough down the eastern side of the UK throughout most of the run (though it is on the cooler side of the ensembles, so could easily be a bit of an outlier). UKMO looks a lot more promising today.

[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 TUESDAY MAY 24TH 2016

THE CURRENT GENERAL SITUATION High pressure lies to the North of the UK with a chilly NNE flow over the east of the UK and a less fresh flow further west. A trough of low pressure will move west from Europe into Eastern and some Northern areas.

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

CURRENT SNOW FORECAST AND/OR FREEZING LEVEL OVER THE UK The freezing level and snow forecast is now suspended until the beginning of October.

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

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

MODELS-2 WEEK HEADLINE Some thundery rain or showers at times but plenty of dry and fine weather too this especially in the North. Occasionally warm in the South.

THE GFS JET STREAM FORECAST The Jet Stream is expected to feature largely to the South of the UK over the next few weeks. It features in a cyclonic form around Low pressure to the South and SW later this week and over the Bank Holiday weekend this easing out only slowly through the second week as High pressure re-develops to the North and then West of the UK sending a flow South over NW Europe on it's Eastern flank at the end of the period

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

GFS OPERATIONAL The GFS Operational Run today shows Low pressure forming to the South and SW of the UK and High pressure to the North becoming the driving forces within the UK weather over the coming weeks. The situation develops over the next few days as an Easterly flow develops with some reasonably warm conditions but with an increasing risk of thundery showers first in the South from the end of the working week. Low pressure from Europe then becomes the driving force as it moves up into the South of the UK for a time before High pressure rebuilds to the NW and pushes the low pressure areas in the South away East and SE leading the UK falling under a cool Northerly flow by the end of the period with the best conditions then likely to be in the West.

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

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

GFS CONTROL RUN The Control Run shows a very similar sequence of events with some day to day differences between this run and the Operational only making marginal differences at the surface maintaining a largely showery theme across the South with quite warm conditions for a while before the same shift of High pressure out into the Atlantic late in the period opens the door to the North for cool and showery weather to affect the UK as we move deeper into June.

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 continues to show quite a muddly pattern with the bias looking like High pressure lying to the West or SW with a NW flow across the UK with varying degrees of influence of Low pressure towards the North and NW.

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 the North and NW the best place to be over the coming 5 days or so as High pressure lies close by to the North. Here there will be a lot of dry and fine weather. The further South one travels would see the risk of thundery showers increase with the weather slowly turning cooler later in the weekend as the North and NE wind increases across the South and East as the pressure gradient increases across the South.

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

THE FAX CHARTS The Fax Charts show High pressure to the North over the next 5 days with troughs of Low pressure straddling the UK over the weekend, all rather weak but significant enough to promote some showers to develop across the South, some thundery in increasingly warm and humid air.

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

GEM The theme of GEM this morning shows High pressure to the North and lower pressure to the South throughout it's 10 day forecast period with the main theme being North and NW being best for sunshine and dry weather while Southern areas see a risk of thundery showers at times in occasionally warm and humid conditions.

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

NAVGEM NAVGEM keeps High pressure to the North too with the same risk of thundery showers in the South lasting up to the middle of next week when the showers could ease due to High pressure edging closer up to the South as well.

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

ECM ECM today is maintaining the pattern of High pressure to the North strengthening next week with Low pressure to the South throughout. With that High pressure to the North strengthening the pressure gradient over the South is shown to increase next week making the rather warm and humid air across the UK at the weekend feel rather fresher but never removing the risk of thundery showers edging up from Europe at times right out to the end of the run.

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

ECM 10 DAY MEAN (12z) The 10 Day mean Chart from last night shows the UK still in very slack conditions at Day 10 as High pressure to the South and North are dissected by Low pressure over Southern Europe and well out in mid Atlantic. The most likely result would be a lot of dry and bright weather with a few showers particularly towards the South and SE..

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

NOTABLE TRENDS & CHANGES FROM PREVIOUS RUNS There remains no strong desire for the models as a whole to remove Northern blocking High pressure over the next few weeks at least, leading to an East or NE flow being maintained with thundery showers in the South to remain the main theme between the models.  

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 96.0 pts while GFS lags behind at 95.6 pts. At 5 days ECM leads with 89.0 pts to UKMO at 86.8 pts and GFS at 85.2 pts. Then at 8 Days ECM has the leading spot from GFS with 58.5 pts to 52.0 pts. Finally at Day 10 ECM has the lead from GFS with a score of 38.3 pts to 34.7 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 The main patterning that's shown between the models this morning is not an uncommon one for this time of year when parts of Scotland and the NW of the UK can often see the best conditions of their year with some good sunny spells and warm conditions prominent. For this to occur we need High pressure to the North and NW with Low pressure to the South of the UK and that's exactly what will be developing over the coming days, a pattern that once formed may prove to hang around for most if not all of the forecast period covered by the output this morning. So from that changes in the overall patterning will be slow but day to day differences in the weather will be small scale but significant. Firstly I would guess that Eastern coasts adjacent to the North Sea will be subject to cloudy and cool conditions as our old friend 'North Sea Haar' is brought in on a NE breeze. Secondly the warm and humid air drifting over Southern Britain from the continent will promote some heavy and thundery showers at times. These look like ebbing and flowing over the period with the main threat looking to come from an increasing and cooler NE flow next week as the High pressure to the NW of the UK looks like it could strengthen more with showers across the South and East in particular. However, that is just a possibility at this range and there will be plenty of warm and dry weather in the South too over the long weekend with just the risk of thundery showers rather than wall to wall rainfall. So as I've already indicated for the UK it looks like this patterning could be a protracted one with long term changes seeming very slow due to a weak Jet stream and pressure remaining very high towards the Arctic. So with little or no rain in the far NW to some heavy showers elsewhere it may well be that rainfall becomes well below average in the North over the next few weeks with some places in the South too seeing very little if you manage to avoid the scattered downpours. Temperatures should hold up well especially in the West and NW while cooler air could affect the SE later and the North Sea coast looks particularly prone to coolness with onshore winds. Nevertheless I have seen far worse charts for the beginning of June so my advice is enjoy the warmth and sunshine where you can. More from me tomorrow.

Next Update Wednesday May 25th 2016 from 09:00

[johnholmes]

If one compares the overall pattern shown on GFS and ECMWF 00z runs today for 144 and 168h they are neither of them that far from the anomaly output this morning for EC-GFS, see below. Remember the 500mb charts are for 500mb and the others show the surface isobars.

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

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

The NOAA view is less cyclonic in appearance last  evening than the EC-GFS this morning.

Summary would perhaps be, better the further NW one is in the 144-168 hour period?

[knocker]

A  couple of the ecm ens anomalies. The EPS 850mb chart for 12z Tuesday has the low centred over Belgium. The 10-15 still looking okay with ridging up through the UK into Iceland. Dry with temps a little above average,

Edited May 24, 2016 by knocker

[joggs]

Why could we not have this sort of pattern in mid winter aaaaargh.

[knocker]

Still looking at around the first of June for the next bout of good weather after a brief interlude.

 

[Summer Sun]

As the beebs chart shows Monday doesn't look a wash out by any means not spectacularly warm but plenty of usable weather

Beyond this ECM shows high pressure edging in temps pegged back a bit in the east but pleasant enough in any sunshine

 

Highest temps will be in the west

Edited May 24, 2016 by Summer Sun