Model Output Discussion - 16th Jan 12z onwards - Smile While You Post!

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY THURSDAY JANUARY 22ND 2015.

NEXT UPDATE FRIDAY JANUARY 23RD 2015 08:00

THE CURRENT GENERAL SITUATION An area of slack winds will be maintained across the UK today followed by a trough of Low pressure moving in from the west tomorrow.

MODELS-2 WEEK HEADLINE Changeable with rain at times but some drier spells too. Less cold. Possibly turning more generally unsettled and colder again later with some snow in places, especially over the North.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream Forecast shows the trough in the flow over Europe receding East and then settling into a West to East motion across the UK with occasional tilts slightly North of West over the South of the UK on it's way to Europe later in the period.

GFS OPERATIONAL The GFS operational today continues to show the UK under the influence of West or NW winds around a strong Azores Anticyclone and deep Low pressure areas moving East and SE to the North and East of the UK. Things change little over the course of the run this morning with all areas seeing spells of rain on successive cold fronts passing over and followed by colder NW winds and wintry showers most prevalent towards the North and East of the UK especially later in the run.

THE GFS CONTROL  The GFS control run mirrors the operational run well with strong confidence in West or NW winds dominant across the UK over the enxt couple of weeks. Temperatures will fluctuate day to day but it will never be desparately cold with wintry showers between the rain bands restricted to the North. At the end of the run the model deepens the unsettled weather over the UK with all areas seeing strng winds and rain and more coherent colder weather filtering into the North later.

THE GFS CLUSTERS The GFS Clusters today show very mixed messages none of which show any particularly cold evolution for the UK. We have a 30% each spread in Low pressure to the North and a strong Westerly flow likely to a High pressure cell to the East and a Southerly flow across the UK with coldest conditions in the continental flow over Eastern Britain to Westerly winds with High pressure close to the South which would mean mild weather for all.

UKMO UKMO this morning shows High pressure close to the South and SW at the start of next week with further weak cold fronts crossing East across the UK with some rain chiefly over the North followed by fresher weather with patchy night frosts and bright days.

THE FAX CHARTS The Fax Charts show a series of fronts moving East and SE across the UK over the next 5 days with alternating spells of rain and milder air mixed with short periods of colder and clearer conditions with some wintry showers in the NW and frost at night in places.

GEM GEM today shows a spell of west and NW winds strengthening later around a large Azores anticyclone and strengthening Low pressure areas moving East and SE across the North Sea and NW Europe later. Spells of rain followed by clearer and colder conditions will continue across the UK throughout the period with the depth of the cold periods increasing later with more frequent incidences of wintry showers for may later next week.

NAVGEM NAVGEM also keeps the same trend and pattern as West or NW winds carry spells of rain followed by colder and clearer conditions with wintry showers in the NW. As with GEM the colder NW winds become more coherent for the rest of Britain instead of just the NW later next week with wintry showers between further rain bands extending to all areas.

ECM ECM this morning continues yeaterdays theme of West and NW winds around a High pressure area persistent to the SW of the UK. Southern and Western areas will maintain the driest and mildest weather with the colder air between successive cold fronts coldest over the North and NE where some wintry showers ccur at times. As of yesterday the run indicates a passage into much colder weather for all in a more direct Northerly feed late in the run with wintry showers of sleet and snow for all for a time but it looks like the Azores High will once more send a toppling ridge across the UK with milder westerly winds returning soon after Day 10.

ECM 10 DAY MEAN The ECM 10 Day Mean Chart today continues it's promotion of cold NW winds around Low pressure over Scandinavia in 10 days time with wintry showers and rather cold weather most likely across the UK though it never looks like becoming desperately cold.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The trend today is for the models to of slightly watered down the return to cold North or NW winds later mostly due to the strength of the Azores High.

MY THOUGHTS It appears that the spell of somewhat less cold conditions alternating between cloudy conditions with some rain and brighter and fresher conditions with some sunshine looks set to be dominat across the UK for some considerable time to come. There is still indications that a more coherent dip into rather cold NW or even North winds later for all areas as Low pressure sinks South over Europe and veering winds as a result so that most places could see some sleet or snow showers later. However, the problem continues to lie out to the SW where the Azores High continues to have one of it's strongest strangleholds on UK conditions in Winter I have seen for years. This coupled with a persistent strong vortex up to the NW of the UK shortens the duration of any cold interventions we have from the North and despite the cold look of some of the synoptics in 10 days time particularly from ECM it looks very transitory as the Azores High fails to ridge sufficiently North over the Atlantic and the inevitable toppling of a ridge from it cuts off the Northerly feed to bring milder westerly winds back fairly quickly. GFS doesn't offer much in the way of hope for cold in it's clusters this morning all showing variations of fairly mild options unless the clump showing High pressure East of the UK moves on later to provide something more fruitful. However, all the above is decribed as just one run in a very fluid situation longer term but one thing is for sure in that unless the Azores High moves or weakens then any excursion into cold weather will be short and less sharp across the UK.

[chionomaniac]

Quite a few towards the -10c range, haven't seen that much the last few years....even if it doesn't verify.

Up til now all the ensembles have offered alternating periods of colder/milder interludes - a few (and I mean 1or 2) are now showing lower 850's and remaining there. Just an observation.

[BlueHedgehog074]

It looks as though the weather will act like a 'yo-yo' as the models shows the Uk becoming influenced by up and down a milder and colder interludes. Low Pressure mostly invasive to the North with the Azores High Pressure system holidaying in it's location to the South-West.

Friday will see a cold front sweep South-East across the country bringing heavy rain and hill snow to places - clearing to cooler conditions on Saturday with some wintry showers to the North-West. The chilly Polar Maritime airflow developing on Saturday with -5*C or colder 850 hPa temperatures getting into the mix should enable sleet and snow from showers to the North-West to fall to some reasonably modest levels at times - perhaps down to around 200 meters in the heavier showers. Maybe even a bit of sleety stuff down towards 100 meters, especially towards Scotland. Sunday then looks to become milder again as the flow backs to the South-West along with Low Pressure to the North-West bringing another spell of rain across the country. This again clearing to a chilly Polar Maritime flow from the North-West later on Monday with a fresh set of wintry showers towards the North-West. The models do then seem to suggest that the flow will generally back from a cool North-Westerly direction the further into next week we go, as Low Pressure systems try to dig South-East into Mainland Europe along with the Azores High getting held out to our West or South-West. This could help bring something more widespread in terms of wintry weather if enough cold air can get dragged down from the North-West or North. North-Western areas, though, would continue to benefit the most from this kind of setup with Northern areas likely to see the coldest temperatures. Frost could be possible at night during clearer skies at night, especially to the North.

Compared to the last few runs, though, the GFS looks a little bit underwhelming with regards to its Polar Maritime flows next week with the Azores High struggling to amplify much to allow freezing air to drain down from the Arctic. It would still be quite cold at times, but you would probably still have to be towards the North or North-West to see something wintry.

Personally, I think with 500mb heights continuing to look very Low towards the Greenland and Canada area at times, this will probably continue to spit out Lows towards the UK keeping us locked in a fairly Westerly, Atlantic, drivern pattern. Clearly it's possible things could further improve for cold weather prospects and there are models, such as the ECMWF, which shows something more potent towards the end of its run with a cold Northerly occurring (though it could be argued it might just be over-amplifying things in deep FI). It could just turn out to be one of those standard topplers where the amplified Azores High Pressure gets flattened by the next Low coming in from the West, unless the Azores High can send some of its heights up to Greenland. I guess it's not really worth going into too much detail as what does seem evident, for now, is that the Jet Stream should end up taking a more North-West to South-East direction through the UK during next week and help with dropping Low Pressure systems East into the continent.

The 8 to 14 Day 500mb Outlook from the NOAA does paint a generally rather cool picture with a flow at the 500mb level backing North-West through the UK with troughing going East into Europe. Some decent amplified opportunities upstream over Northern America with some fairly notable troughing over Eastern Northern America with ridging on the Western side of Northern America. This ridge may back towards Greenland and perhaps deliver something cold from the North for the Bristish Isles should the Azores High ridge far enough North to connect to the ridge close to Western Greenland. Otherwise no real Northern blocking seems likely at present.

Although I don't really know much about the MJO, I'm guessing this would should show us entering Phases 6, 7 or 8, which I guess would be good for amplied solutions to deliver cool/cold weather for the UK (apparently seems the case that Phases 1 to 5, or that 'Circle of Doom' people talk about on this thread, being a no-go for cold weather opportunities).

Hopefully, for those in the South who still really want to see the white stuff that some widespread wintry weather can develop, and that the weather patterns can indeed amplify enough to help drag some very cold weather down from the North. Or even North-East. At least there are some encouraging signs that the weather should generally remain on the cool side for those that want it. But otherwise still fairly ordinary for January with ridges and troughs at times perhaps leading to something colder from the North, especially if that Azores High can amplify enough to drag down some chilly Arctic air Southwards through the Bristish Isles.

Edited January 22, 2015 by DiagonalRedLine

[snowking]

I can only offer advice on the overall longwave pattern in the day 10-15 range (and those are the only details anyone can really pay attention to at that range) but it would be this - be very wary of any NWP showing more vortex strength to our NW compared to that to our NE.

Whether you look stratospherically, tropically (MJO) or even in terms of seasonal ENSO analogues, there is very little to suggest a roaring vortex to our NW. Of course we don't always need that to cause spoilers for the shortwave pattern, but even under such conditions transient northerlies would likely keep things feeling seasonal overall.

For now it is a reasonable assumption to make that the ECM EPS, with their entirely superior resolution (across both axis) would be better at mapping the overall longwave pattern in the 10-15 day period, and that essentially suggests that infamous deep euro trough, fed by the upper vortex aligned through Siberia, with positive anomalous heights somewhere to our west.

Probably worth noting we are making assumptions here that NWP is resolving all of the above correctly at present, and there is still a fair bit of ambiguity in relation to the MJO signal (and indeed how much of an effect any MJO wave may have on the triposohere vs signal from above) but if those reasonable assumptions are correct then to summarise - be very wary of any output ramping up the vortex to our NW, and consequently not developing the Siberian elongated vortex

SK

[Ali1977]

With it only being later next week we are talking about a potential Northerly flow, by this weekend we should have a good idea wether this could materialise.  The long range BBC weather may start mentioning it in the next few days if they believe it could happen, and no doubt Ian will give his thoughts from the METO.  The ECM solution should give UK wide wintery showers for atleast a day, that would be a start for the coldies starved so far this winter, which by the way has been better than last years gales/rain whatever happens.

[MR EXTREMES]

The ecm today brings the deep lower heights dropping them East and South into Central Europe.

This morning has moved this one day closer of coarse more runs needed.

The gem is similar but lower heights a bit further east but on a broad spectrum the models are all similar in a more realistic time frame.

29th being around the date when the changes look to start but undoubtedly interesting signs showing.

[Captain Shortwave]

The way I read that chart is northerly will last 24 hours as the low just to the south of Greenland has one name on it, the uk , toppling the high, the segment of vortex over the U.S will join back up with the main lobe , I don't think this notherly is going to happen to be honest , certainly nothing to get excited about . Hope I'm wrong but been burnt to many times . May get some interest a week or so later but untill I see cross model agreement then I don't believe it.

Having the strat on side is all well and good but it rarely delivers to our tiny island.

Well the ens at least give the operational some decent backing.

 

I think the ultimate goal for us would be to get the Pacific ridge to sever the Canadian lobe of the polar vortex from the Siberian one, once that happens the Canadian lobe will simply sink deeper into north America (ultimately putting central/eastern states into the freezer). Once this happens and the US trough deepens, this will finally allow the Azores high to ridge northwards and allow the Siberian lobe to align for a cold northerly blast heading towards the UK and most of Europe. TEIT's diagram from yesterday summed this up perfectly.

Pure speculation at the moment as the American models are less keen on this and keep the polar vortex more robust. 

[bluearmy]

I can only offer advice on the overall longwave pattern in the day 10-15 range (and those are the only details anyone can really pay attention to at that range) but it would be this - be very wary of any NWP showing more vortex strength to our NW compared to that to our NE.

Whether you look stratospherically, tropically (MJO) or even in terms of seasonal ENSO analogues, there is very little to suggest a roaring vortex to our NW. Of course we don't always need that to cause spoilers for the shortwave pattern, but even under such conditions transient northerlies would likely keep things feeling seasonal overall.

For now it is a reasonable assumption to make that the ECM EPS, with their entirely superior resolution (across both axis) would be better at mapping the overall longwave pattern in the 10-15 day period, and that essentially suggests that infamous deep euro trough, fed by the upper vortex aligned through Siberia, with positive anomalous heights somewhere to our west.

Probably worth noting we are making assumptions here that NWP is resolving all of the above correctly at present, and there is still a fair bit of ambiguity in relation to the MJO signal (and indeed how much of an effect any MJO wave may have on the triposohere vs signal from above) but if those reasonable assumptions are correct then to summarise - be very wary of any output ramping up the vortex to our NW, and consequently not developing the Siberian elongated vortex

SK

Extended eps continue to trend away from the Alaskan ridge getting into greenland

However. As I discussed with nick yesterday, this still only begins in low resolution and at day 10, one would think it a reasonable chance looking at the output. If this trend continues, we could get to the point where the extended have to go a different route as the n greeny region will show heights!

[Nick F]

My latest synoptic outlook takes us to the end of January:

 

http://www.netweather.tv/index.cgi?action=news;storyid=6415;sess=

 

- ... in a nutshell, turning more changeable from tomorrow, with days of milder weather but also days of colder weather as the westerly jet meanders across the UK. Spells of wind & rain at times, especially in the milder interludes ahead of weather systems passing to the north Drier and brighter spells, with wintry showers in the north, associated with the colder interludes as systems move away to the north. Uncertainty for last few days of Jan and into early February with regards to whether or not we stay on the cold polar side of a NW to SE aligned jet for a longer period, depending how far east or west the Euro trough sets up, too far east and it lets the Azores high ridge in with higher chance of milder conditions.

[Nick F]

Quiet in here ... more amplification on 06z GFS mid-Atlantic by next weekend compared to the 00z - still not enough amp to head us into a full on northerly though ...

[bluearmy]

Just to add - in respect of the ecm op and ens, the spread west days 8/10 on the low heights probably relate to a 'runner' scenario as evident in the ecm op and gem op and now 06z Gfs op.

I would suggest that this potential feature offers the more wintry opportunities for those not excited by a possible northerly flow.

[Nick F]

Just to add - in respect of the ecm op and ens, the spread west days 8/10 on the low heights probably relate to a 'runner' scenario as evident in the ecm op and gem op and now 06z Gfs op.

I would suggest that this potential feature offers the more wintry opportunities for those not excited by a possible northerly flow.

 

ECM op furthest south with that secondary wave/low late next week and more favorable for wintry conditions further south, 06z GFS has the wave further north and thus snow confined to NE Scotland. But this secondary features seems to be the trigger to carve out a deeper H500 trough across southern Europe with the Genoa low to allow the northerly flow - helped by more amplification upstream over the Atlantic too. But hard to have any confidence this far off on any such secondary features.

 

All in all, any cold incursions may only offer brief wintry potential, more particularly Midlands north, unless we get rid of those low heights over Greenland and Iceland.

[492]

http://meteocentre.com/analyse/map.php?map=Europe&date=2015012211&size=large〈=en&area=eur

A rare easterly has arrived across more southern parts. Not spectacular but relatively cold compared to the winter so far. Patchy light snow is evident upwind over the near continent at 1100hrs.

[TEITS]

Considering the scatter I think this is one of those times when looking at the GEFS mean is a waste of time. You are better off viewing each member and noting whether the much colder NW,ly/N,lys are increasing in each run.

[legritter]

Quiet in here ... more amplification on 06z GFS mid-Atlantic by next weekend compared to the 00z - still not enough amp to head us into a full on northerly though ...

but hopefully some good signs emerging today ,lets hope 12z gfs shows a less strong azores high and tonights runs also show plenty of scope .Last frames of ECM this morning also promising but you can just see that big fat lardy azores awaiting to pounce but i could be wrong ,a diving south of the jet is my straw clutch today plus a possible rising of pressure on our side of the pole .do feel though that we need a big player on scene soon but we are only just half way through winter so all to play for ,catch you all up later ,Sausage sandwich brown sauce here i come .  

[TEITS]

This chart below is why I am sitting on the fence at the moment.

 

http://modeles.meteociel.fr/modeles/gens/run/gensnh-0-1-204.png?6

 

The trough and the Azores HP are far too E. We need to see this set up further W and that bloody Azores HP is getting on my T**s!

[IDO]

The JMA update not really going with the expert's consensus of the PV ebbing away from Greenland/NE Canada: 

 

That is the week 2 anomaly and it is quite strong. It is very similar to the last couple of days of GEFS for that period, where we get a push of positive heights from upstream (US) that push the Euro trough east. It maintains the main vortex over Greenland, dispatching a cold zonal flow from the NW, keeping the UK at the end of the zonal train. We have the Pacific & Siberian positive anomalies as per recent model output.

 

Week 3-4 shows no clear signal for our region: 

 

Our first shot of cold PM air looks around T150 and that may give some snow to Northern regions. Before that classic sine wave signal for transient PM and TM shots:

 

 

Around D9 the GFS 06z hi res runs moved slightly closer to the ECM, further west and more amplified, but still no cigar just yet. Though the GEFS have moved slightly further west than the ops, and are more amplified still. However none really look like they can build  a sustainable Atlantic Ridge. The biggest cluster topples and flattens the pattern, some build a MLB like the Control:

 

D8:   D12: 

 

The mean at D12 still has the mean PV lobe over to our NW: 

 

So hard to see anything interesting developing in the next 12 days for a pattern change to a blocked cold setup. Just transient cold spells at best with runs like the control giving us 5 days of 2-4c above average 850s:

 

 

 

Though unlikely, it does represent one of the smaller clustering options.

 

 

 

 

[Troubleatmill]

GEFS clusters for t228, 40% going for some kind of north westerly, 35% northerly  

 

http://www.woeurope.eu/cgi-bin/expertcharts?LANG=eu&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cslp&HH=228&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

[snowblizzard]

This chart below is why I am sitting on the fence at the moment.

 

http://modeles.meteociel.fr/modeles/gens/run/gensnh-0-1-204.png?6

 

The trough and the Azores HP are far too E. We need to see this set up further W and that bloody Azores HP is getting on my T**s!

What is actually stopping that damned Azores High drifting West or South this year?

Edited January 22, 2015 by snowblizzard

[fergieweather]

Latest from UKMO unified model monthly suite (incorporating GloSea5) indicates unsettled phase first half of February. Thereafter, signal is more ambiguous, with increased number of blocked members. This *may* result in greater likelihood of colder episodes, but tonight's EC Monthly update is awaited to offer comparative prognosis.

[nick sussex]

What is actually stopping that damned Azores High drifting West or South this year?

The placement of the Azores high is just reflecting the overall set up and shouldn't be viewed as some entity that just decides to move in and stay.

 

The problem has been low heights to the nw and the lack of upstream amplification which is really the main cause.

[TSNWK]

Latest from UKMO unified model monthly suite (incorporating GloSea5) indicates unsettled phase first half of February. Thereafter, signal is more ambiguous, with increased number of blocked members. This *may* result in greater likelihood of colder episodes, but tonight's EC Monthly update is awaited to offer comparative prognosis.

Good afternoon Ian, many thanks for the insight - may I inquire on the unsettled phase 1st half of February please - basically is it what most might describe as standard zonal with lows scooting across west to east to our north on a strong jet, or are there any indications that the unsettled phase will be more amplified keeping the interest going coldies.

Cheers.

[Woollymummy]

here is the Azores beast in motion from EUMETSAT:

 

http://www.eumetsat.int/website/wcm/idc/idcplg?IdcService=GET_FILE&dDocName=VID_IL_14_12_16&RevisionSelectionMethod=LatestReleased&Rendition=Web

 

[IDO]

The placement of the Azores high is just reflecting the overall set up and shouldn't be viewed as some entity that just decides to move in and stay.

 

The problem has been low heights to the nw and the lack of upstream amplification which is really the main cause.

 

It has been a trend last Century to increase the strength of the Azores High. That cannot help the UK in years like this where all the blocking is on the other side of the NH:

 

"Statistically significant trend (95%) of the pressure in this High in both 1950–1989 (5.7 hPa per 100 years) and in 1970–1989 (12 hPa per 100 years)." (Hasanean (2004). Mächel et al. (1998))

 

We see the Azores at 1030-1040mb over the next 2 weeks when it's average is 1024mb. That is a strong block and not helpful in winter especially if it won't displace north. The Icelandic low IMO effects the position of the Azores, and as you say, the persistence of the low heights to the NW keeps the mean Icelandic low in situ, preventing a more ML-HL Block.

 

Its the chicken or egg causality as to what the drivers are. As we have seen this year with our weather (SAI, etc) it is a very complex as to the variables and the usual interactions.

[mountain shadow]

Good afternoon Ian, many thanks for the insight - may I inquire on the unsettled phase 1st half of February please - basically is it what most might describe as standard zonal with lows scooting across west to east to our north on a strong jet, or are there any indications that the unsettled phase will be more amplified keeping the interest going coldies.

Cheers.

I would think the zonality would be of the cold varierty due to the deep euro trough. This would indicate less South Westerly influence and a slightly more amplified Atlantic pattern as low pressure moves through.