Model Output Discussion - Spring 5th March Onwards 6z--->

[Summer Sun]

From Tuesday the ECM ens has a lot of settled weather away from the far north

 

 

With winds generally coming in from the south west I think we can expect a fair amount of cloud with some rain in the far north and west the best of any cloud breaks could be the further east your are, given the wind direction temperatures should be around average

 

Then towards the end of next week the ECM ens shows the high settling things down nationwide

 

 

Again cloud amounts could be quite high but in any breaks and with light winds it would feel very pleasant though the risk of frost cannot be ruled out next week where skies are clear overnight and you have no breeze

[Milhouse]

Before the main rise in pressure in FI, the ECM mean has disturbances running SW-NE indicating occasional pulses of rain spreading west to east, likely to occur Sunday-Wednesday prior to the main rise in pressure from the South. Good growing conditions for sure with temperatures on the mild side.

[damianslaw]

Models painting a rather quiet picture away from the NW quarter of the country. A predominantly dry and very mild outlook for the SE in particular, but the far NW is in for a rough ride with persistant rain and a nagging SW wind.. the dreaded southwesterly springs to mind for the NW...

 

Longer term - signal for a more pronounced pressure rise from the SW building over the country and in towards Scandinavia with the Jetstream well to the NW. Where we go from there is uncertain..

 

March is a battle line month the atlantic often winning out during the first half, but becomes often less influential during the second half and our eyes are often drawn to the north and east.. From a personal perspective after September it is a month I am least enthusiastic with weather wise. I often wish we can fast forward to the second half of April around this time of year - just like early September when I want to fast forward to mid October, it always feels a bit here nor there during the next 6 weeks.

Edited March 5, 2015 by damianslaw

[winterof79]

The PV modelled to shift to Siberia on GFS this morning,with a cool easterly flow.Some lovely NH charts in the latter stages.It could be a very different scenario for March and April than we have experienced in a while.

Edited March 6, 2015 by winterof79

[Captain Shortwave]

The PV modelled to shift to Siberia on GFS this morning,with a cool easterly flow.Some lovely NH charts in the latter stages.It could be a very different scenario for March and April than we have experienced in a while.

Actually the day 8 scenario is pretty mild for the UK

Double figures for all but the upper regions of Scotland and Eastern Scotland in general. The GFS is pretty stunning in week 2 if you want pleasantly warm sunshine with high pressure building strongly just to the east of the UK. In fact the GFS builds the high in that location at day 4 and keeps it there to the end of high resolution.

 

The UKMO is flatter though with a weaker ridge

 

GEM

Flatter but with a more substantial ridge which brings fine weather until day 10, though some fronts in the north west bring rain here at times.

Next week is looking okay actually, with a spell of rain on Monday night into Tuesday but otherwise conditions look set fair and rather mild with winds generally from a west/south westerly direction. Maybe still some rain in the north west at times. Beyond this signs of more robust heights to the east/north east a south easterly developing which at this time of year and set up would bring some pleasant conditions.

This clarified by the GFS ens

Edited March 6, 2015 by Captain shortwave

[winterof79]

Well GFS and ECM have a "slight"disagreement at 168z but the pressure build is only delayed by ecm as it makes more of the feature running n/e off the Atlantic.The flow is much cooler than GFS when the high finds its home ,IF that is where it resides

Edited March 6, 2015 by winterof79

[Duane S.]

The dire late winter period continues but so does the potential for a very late winter cold blast. Not just NCEP, all the MJO forecasts are showing high amplitude 6/7/8 to one degree or another, I remain convinced we are finally going to see proper HLB setting up after mid month. Too late for long lasting lying snow but plenty earlier enough in spring for some very decent snowfalls

Edited March 6, 2015 by s4lancia

[IDO]

Looking at the London rainfall totals and GFS has been consistent with the upcoming dry period: 

 

Temps in the next few days look like being at least 2-3c above average though with the potential to be 5-6c above where we see a period of unbroken sunshine. Would not pay any attention (as usual) after D6 on the GFS op as it blows the pressure up and is looking an outlier on various charts. The London mean pressure remains above 1023mb right through to D16. No surprise as week 2 has always IMO been more certain than week 1. Ignoring the over amped GFS op in FI the Control is more the way it may go; D10 and it ties in nicely with the mean:

 

 

 

D13 and D16 means:   

 

Maintaining an average to milder than average theme. That is not a cold mean. Last night's ECM extended mean has a strong cluster 3-5c above average for that period:

 

 

As expected in week 1 the jet is now being projected in the middle ground, ECM was too far south and GFS too far north. GEM was consistently in between. The net result is the south misses any storms and any fronts track north of Birmingham:

 

 

At D10 all models are pointing towards maintaining the settled period towards the end of week 2:

 

  

 

So confidence remains high for 13 days at least of dry, sunny at times and mild as a whole weather for the south. Not so good in week 1 further N/W, but it will improve in week 2 up north.

[John Badrick]

Delete if you must mods, but I just wanted to express my frustration of how much comments completley contradict each other, the last 2 are a perfect example, we are in for cold snow and warm sunshine apparently

[IDO]

Delete if you must mods, but I just wanted to express my frustration of how much comments completley contradict each other, the last 2 are a perfect example, we are in for cold snow and warm sunshine apparently

 

There is near to zero chance for snow in the next 13 days. The MJO composites suggest HLB'ing is possible later in March, however that is a guide and the placement of that positive pressure anomaly could easily be further south. That is assuming that the GFS MJO signal is not over done. Lots of ifs and buts so we might as well go with the current output and at the moment it looks more likely temps will be average to above, rather than below.

 

A blog from WSI suggests that the GFS MJO signal is not backed by other models: http://www.wsi.com/blog/energy/europe-possible-effect-of-the-madden-julian-oscillation-later-in-march/

 

I am going to enjoy the mild early Spring weather.

Edited March 6, 2015 by IDO

[Captain Shortwave]

Delete if you must mods, but I just wanted to express my frustration of how much comments completley contradict each other, the last 2 are a perfect example, we are in for cold snow and warm sunshine apparently

This can be answered with another question. When does an easterly stop being cold and become warm/hot?

March 2013 of course saw an easterly which produced ice days, meanwhile March 2014 saw a east/south east flow which saw temperatures of 20C in the south east. It comes down to how cold the continent is at the time and of course whether you pull very cold air down from the arctic.

Whilst the GFS shows above average but not warm 850s, the continent will have warmed up substantially with temperatures in the mid to high teens widely so when the wind swings to the east/south east, the air pushing in from the continent is not cold any more and as it is March then you cannot develop cold at the surface level.

The ECM does pull a cold pool in from the east, but again this would result in chilly/cloudy conditions rather than a truly cold scenario (5-8C with a raw wind along eastern coasts). The ECM though is probably one of the coldest solutions in the model suite this morning.

 

@S4Lancia I can't really see this happening to be honest, the high amplitude phase 7 signal from the GFS is completely backed up by the model output of heights north east of the UK with a south easterly feed.

I can't really see it to be honest and backs up the week 2 claims from the models of heights east/north east of the UK with an east of south flow. Dry and blocked sum it up, how cool/mild it will be will be dependent on what kind of feed we get from the continent. Obviously the hope is that we can shift the MJO signal to phase 8, which would be more interesting for cold, but that is miles away (week 3 onwards).

We would also need the phase 8 signal to be high amplitude, or you just end up with a UK trough with near normal temperatures, that's if the MJO is the main driving force for our weather at this given time.

(low amplitude composite)

Edited March 6, 2015 by Captain shortwave

[Gibby]

HERE IS MY LATEST ANALYSIS USING DATA SUPPLIED BY THE NWP OUTPUT COVERING 5 OF THE WORLDS MOST POWERFUL WEATHER COMPUTERS.

 

THE CURRENT GENERAL SITUATION A mild SW flow, strong in the North covers the UK with a slow moving trough near NW Scotland.

 

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

 

MODELS-2 WEEK HEADLINE A lot of dry and reasonably mild weather with some sunshine in the South and East but occasional rain possible at times especially over the Northwest.

 

THE GFS JET STREAM ENSEMBLE FORECAST The Jet Stream Ensemble Forecast shows the flow continuing to blow from the Atlantic to a position to the NW of the British Isles where it remains for the next week or so. The flow remains weak and well away to the West and North of the UK later before repositioning more towards a Southern latitude late in the period.

 

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

 

GFS OPERATIONAL The GFS operational today shows a lot of dry weather across the UK over the next few weeks with weak troughs interrupting the High pressure based weather at times and possibly more extensively later as High pressure close to the South of the UK at times becomes replaced by new centres first to the NE and then away over Europe to introduce the more unsettled end to the run as Low pressure feeds in from the West.

 

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

 

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

 

THE GFS CONTROL The GFS control run looks broadly similar with various High pressure areas building then receding away to the East as occasional weak troughs retract their influence over the UK on their passage through the North and West of the UK. More generally unsettled conditions are shown moving in from the West late in the period.

 

THE GFS CLUSTERS  The GFS Clusters show as much as 85% of members suggest High pressure being dominant centred somewhere across the UK in 2 weeks time with only 15% showing any Atlantic Westerly influence over the UK with some rain.

 

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 UKMO this morning shows High pressure developing behind Mondays trough early next week before it too relaxes away to the SE with SW winds and troughs returning to the NW by soon after midweek.

 

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

 

THE FAX CHARTS The Fax Charts show a weakening cold front moving SE on Sunday with a weakening band of rain crossing SE followed by a small but significant Low pressure running NE to the NW and being replaced by a strong build of pressure across the UK at the end of the 5 day period.

 

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

 

GEM GEM today shows a SW flow to the NW of High pressure over the near continent being the main driving factor of the weather over the coming 10 days. Northern and Western parts could see occasional rain as fronts pass through at times but here too some dry and fine weather is likely on occasion.

 

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

 

NAVGEM NAVGEM too shows building and receding High pressure close to Southern Britain over the period with a SW flow the most likely prevailing winds delivering plenty of dry and bright weather but with short spells of cloud and rain moving through especially towards the North and West on occasion.

 

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

 

ECM ECM this morning shows a mostly SW flow across the UK at first with occasional troughs delivering rain in the North and West at times. Later in the priod the SW flow decays as High pressure relocates to the NE of the UK and intensifies further. The end of the run shows fine weather under a strong ridge West across the UK from it's centre over Eastern Europe

 

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

 

ECM 10 DAY MEAN The 10 Day Mean Chart shows High pressure well in control of the UK weather in 10 days with a centre to the east allowing a SE flow across the UK with troughs held well away to the NW along with the Jet flow.

 

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

 

NOTABLE TREND CHANGES FROM PREVIOUS RUNS Yesterdays weaker High pressure influence has become more muted again this morning with many places seeing a lot of dry weather in the 14 day model period with meaningful rain very occasional and affecting only the far NW. 

 

31 DAY HISTORICAL VERIFICATION STATS FOR GFS, UKM & ECM The current verification statistics for the past 31 days shows ECM leading the way at 3 days with 97.6 pts followed by UKM at 97.1 pts and GFS at 96.4. At 5 days ECM  continues to lead the field at 90.1 pts over UKMO at 88.5 pts and GFS at 86.7. At 8 days ECM remains the leader with 67.2 pts over GFS's 60.5 pts. Then at Day 10 ECM retains superiority at 49.9 pts over GFS at 42.2. 

 

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.prig

 

 

MY THOUGHTS The weather over the next few weeks remains focused on the behaviour of High pressure and it's positioning in relation to the UK over the coming weeks. There has been increased support this morning for the influence to be greater and more extensive than was shown yesterday with amounts of rain from weak Atlantic fronts grazing the High pressure area weak and more restricted towards the NW as the High pressure looks most likely to lie close to the South and SE of the UK than anywhere else. However, some output does show the odd trough making it through the High pressure block with a little rain possible even in the South very briefly but this is the exception rather than the rule until very late in the run. I have been careful this morning in not making much comment on temperatures within the individual model runs as the positioning of the High and the prevailing winds around it being crucial in determining surface temperatures across the UK. What I can say is that it is unlikely to be particularly cold at any juncture through the period especially by day and with many output runs showing a High just to the SE some very mild weather can be expected at times in the prevailing SW wind. Some output particularly ECM carry High pressure across Europe later with a strong ridge lying West over the UK and I suppose it is feasible that any Easterly drift on the Southern flank of that ridge could drag colder air across from Europe though as it stands the air across Europe never looks particularly cold as things stand this morning and the desire to push the ridge further South and bringing back a SW feed is more likely given that the Jet flow is programmed to remain well to the North and NW of the UK throughout. So finally it looks like we are in for a spell of very decent weather across the UK with small amounts of rain for most expected away from the high ground of the NW, sunny and cloudier spells alternating day to day and reasonably mild weather on offer too with frost and cold weather levels largely infrequent through the next few weeks.   

 

Issued at 09:00 Friday March 6th 2015

[Summer Sun]

Looking at the ECM ens the south east is in for a lengthy period of settled weather with pressure here always high whilst the far north and north west looks prone to the heaviest rain we're looking at 50mm to 100mm quite widely over the next few days with the potential for up-to 200mm in the west highlands that combined with snow melt could lead to some flooding.

 

 

Into next week and ECM shows the centre of the high building to our east before a south westerly flow is re-established

 

 

Towards the end of the ens a light south easterly flow is established

 

 

After a very mild weekend temperatures next week are likely to ease off slightly but daytime highs for most should be around 8c to 12c

Edited March 6, 2015 by Summer Sun

[stodge]

http://modeles.meteociel.fr/modeles/gfs/runs/2015030606/gfs-0-192.png?6

 

GFS 06Z Operational at T+192

 

http://www.meteociel.fr/modeles/ecmwf/runs/2015030600/ECM1-216.GIF?06-12

 

ECM 00Z Operational at T+216

 

Not a million miles away from each other though if we are to believe the GFS low-res such a strong HP declines and is pushed aside very quickly which I would find unusual.

 

Positioning and orientation are everything in these situations - both HP are over Scandinavia but one is tilted more NW and the other more W so do you get a brisk SE'ly flow set up or a softer E'ly drift ?

 

Far too early to make that call of course.

 

Someone on top of a Surrey hill quoted the latest thinking on the MJO earlier - the AO continues to interest:

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao_index_ensm.shtml

 

Very high (up to 6) suggesting a strong HP (over 1050 MB) but after mid month a steep decline with more than one member going very negative very quickly. Have seen some evidence of that on a few runs recently but less so today oddly enough.

[winterof79]

The dire late winter period continues but so does the potential for a very late winter cold blast. Not just NCEP, all the MJO forecasts are showing high amplitude 6/7/8 to one degree or another, I remain convinced we are finally going to see proper HLB setting up after mid month. Too late for long lasting lying snow but plenty earlier enough in spring for some very decent snowfalls

image.jpg

There are signals late on in the GEFS for HLB 

They are toying with an Aleution ridge pushing into the Arctic and as the PV shifts Eastward.

Peturbation 9 when followed through is a thing of beauty....... even in March

 

http://www.meteociel.fr/modeles/gefs_cartes.php?code=9&ech=192&mode=0&carte=1

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=6&ech=384

[johnholmes]

Very high (up to 6) suggesting a strong HP (over 1050 MB

Can you explain that comment please Stodge?

thanks

[IDO]

Next 8 days rain totals show that in Spring being in the SE is of benefit, contrary to winter synoptics, though ECM wetter with four periods of rain, though far from convinced with that:

 

 

 

So strong signal for dry weather for the south. Just how warm will it be? Looks mostly 1-2c above average with a couple of warmer days:

 

 

Further on the UKMO update suggests dry in the SE till at least the 4th April. The D16 GEFS clusters have 80% of members under a UK high, just the placement open to debate, but nothing too cold there:

 

 

The Aberdeen mean uppers (850s) showing week 2 uppers between 2-5c above average: 

 

Signs at the end of FI that heights are trending down so possible signal for HP domination to waver in the last week of March? Early days for that yet.

[Frosty.]

6z looks increasingly blocked with high pressure across Scandinavia, eventually there is no frontal activity, it becomes fine with lots of sunshine from around the middle of next week in the south, the fine weather slowly spreading north as HP intensifies further east. Wind direction varies between easterly and southerly during the outlook period with a mixture of chilly and mild days but always feeling pleasant in the strengthening mid March sunshine sheltered from any chilly breezes.

Edited March 6, 2015 by Frosty.

[Captain Shortwave]

GFS day 7 and 10 mean

 

ECM for the same time

 

 

Definitely a suggestion that settled weather in the south may become more widespread during week 2 as heights build to the east/north east of the UK. This backed up by the MJO predictions and the JMA monthly. I would expect at the moment that the middle part of March may be very dry for most and as a continuing trend of 2014 so far, probably a sunny one too with winds generally coming in from the south east.

 

The JMA shows high pressure waning by the end of the month with perhaps a westerly flow re-establishing in the north of the UK, ties in with IDO's post above. But that is a long way off and of course the high might not build in it's current modelled location, though the anomaly for heights over Scandinavia is very strong at the present time.

[stodge]

Very high (up to 6) suggesting a strong HP (over 1050 MB

Can you explain that comment please Stodge?

thanks

 

http://en.wikipedia.org/wiki/Arctic_oscillation

 

First, I start from this wordy tome, John, which points out the requirement for low pressure around the Pole but my understanding of the AO forecast is that it doesn't just look at synoptic pressure but at anomalies poleward of 20N.

 

http://modeles.meteociel.fr/modeles/gfs/runs/2015030606/gfsnh-0-168.png?6

 

This is a classic High AO chart and not for the reasons some on here might observe because not only do we have deep LP near the Pole, we have three strong HP cells within the range - two over Northern Canada an one over Scandinavia. These represent anomalies from the expected which would be HP to more southern latitudes.

 

Normally when we get HP over Scandinavia there's a cross-ridge over the Pole which is archetypal of a negative AO phase or we get a very northerly jet but still not very low pressure near the Pole but in this instance despite HP at quite high latitudes pressure remains very low near the Pole and that creates the pressure anomaly and the high positive index.

 

The normal set up of LP over the Pole and HP over the Azores is compensated for in the pressure anomalies and leaves AO as weakly positive. The unusual juxtaposition of quite northerly strong HP while at the same time maintaining intense LP near the Pole triggers, as I understand it, the high AO positive value expected mid month.

 

This is why simply saying a positive AO doesn't bring cold, is highly misleading. It's perfectly possible to get cold air from a positive AO phase but it's likely to be cold dry air rather than snow-laden air. 

[johnholmes]

 

I'll send a pm rather than clutter up this thread with chat

J

[Summer Sun]

GFS has a deep low crossing to the north of Scotland next Thursday with its centre just south of Iceland

 

 

Some rain with the low the bulk of which will be in the west

 

 

As it travels further SE it weakens and eventually fizzles out with the far south staying dry

 

 

Once the low pulls away it allows pressure to rise and that becomes the dominant feature from t168 with the high centred to our east and low pressure to our west we pick up a light south easterly it should also allow some good sunny spells so away from the coast it will feel very pleasant in the strengthening mid march sunshine

 

 

Temperatures as I said above look very pleasant for the majority given winds would be light where skies clear nights are likely to be cold and potentially frosty

 

 

 

[stodge]

http://modeles.meteociel.fr/modeles/gfs/runs/2015030612/gfs-0-216.png?12

 

A thing of beauty....

 

Were this January and were Britain and Europe snow covered, this would be utopia for cold fans in the SE.

 

In low-res regression doesn't quite happen and we end with what looks like a west-based negative NAO though that's not what I'm seeing in the NAO forecasts.

[Nouska]

http://modeles.meteociel.fr/modeles/gfs/runs/2015030612/gfs-0-216.png?12

 

A thing of beauty....

 

Were this January and were Britain and Europe snow covered, this would be utopia for cold fans in the SE.

 

In low-res regression doesn't quite happen and we end with what looks like a west-based negative NAO though that's not what I'm seeing in the NAO forecasts.

 

....and a perfect text book example of the MJO composites in operation. Not much sign of lag in this forecast.  

 

 

 

 

The EC32 doesn't show the amplification lasting for long.

 

[Frosty.]

The GFS 12z builds further on the 6z blocked outlook with two high's linking up to create a very powerful anticyclone (1040-1050mb) centred to the east of the BI which dominates the outlook. High pressure builds across the south next Tuesday but that is just to whet the appetite for things to come, the north / northwest still has low pressure to deal with for a while next week but even the north joins in the fine spell later in the week, then it's High Pressure all the way into the depths of low res with plenty of sunshine and pleasant temperatures by day but cold at night with a risk of slight frosts. A great outlook for the run up to Easter. :-)

Edited March 6, 2015 by Frosty.