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Model Output Discussion - 1st February Onwards 12z--->


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Posted
  • Location: West Dorset
  • Weather Preferences: Warm summers, Snowy winters.
  • Location: West Dorset

Think this is whats known as Shannon Entropy - http://www.wetterzentrale.de/pics/MT8_Nuuk_ens.png   :D  

 

I don`t think you need to be called Shannon to see when the medication starts to wear off but through the mayhem I see a 60/40 split in favor of keeping the cold for a while longer yet and possibly even colder (GEFS).

 

Norwich:

03492_0200.gif

 

ECM in the short term pretty similar, especially around the 6th/7th

03492_0112.gif

 

You cannot deny pressure building, even if you use Kraftwerk`s model but on the slide again at the end of the run.

03492_0112.gif

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Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .

Regarding the ECM ensemble spreads:

 

Lower pressure in the North Sea:

 

post-1206-0-06216800-1422866443_thumb.gi

 

Low pressure over northern France, high to the nw.

 

post-1206-0-85866400-1422866459_thumb.gi

 

You can see by the lack of spread to the west that high pressure there is almost certain to verify but the uncertainty is re any jet cut back into the UK.

 

The spreads still want to sink the high later but its a case of trying to squeeze out some more interest before then.

Edited by nick sussex
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Posted
  • Location: Ski Amade / Pongau Region. Somtimes Skipton UK
  • Weather Preferences: Northeasterly Blizzard and sub zero temperatures.
  • Location: Ski Amade / Pongau Region. Somtimes Skipton UK

I wasn't talking about snow showers at T168hrs, that potential is mainly for Wednesday and Thursday of this week. I thought I made it clear that I wasn't sure about the renewed cold from the ECM. That could still go either way, just waiting to see the ECM ensembles and spreads if theres a cluster with a more favourably aligned high.

 

PS you look in a decent location for those snow showers, fingers crossed you get a decent covering.

 

PSS interesting ECM spread for T144 and T168hrs!

The Southern part of Britain will have a good 5 days of cold in prospect with a keen wind later in the week making it feel very cold. Still a snow risk for the Southeast Wed night into Thursday. Will be able to update snow portal forecast later today. Yes, Nick still time for changes for a more favourable positioning of the high and the European Low to develop a surprise !

C

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Posted
  • Location: Kilmersdon Radstock Somerset
  • Weather Preferences: None Really but a snow lover deep down
  • Location: Kilmersdon Radstock Somerset

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 ridge of High pressure across the UK will slowly give way to a cold NE flow of winds across the UK tomorrow.

MODELS-2 WEEK HEADLINE Remaining cold with some snow showers especially near Eastern coasts. before becoming largely dry and possibly less cold in the North later.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream Forecast shows the deep trough in the flow across Europe lifting as the Jet flow over the Atlantic then rounds the Northern periphery of a UK based High pressure from later this week.

GFS OPERATIONAL The GFS operational today shows the cold weather continuing with High pressure gradually taking control of the UK weather in the coming week. The current Northerly flow is shown to veer NE with snow showers affecting Eastern and Central areas of England for a time through the week before High pressure ridging in over Scotland and Northern Ireland gradually cuts the cold flow off but leave calm, dry and bright and cold weather with frosts at night the largest factor of the UK weather from then on throughout week 2.

THE GFS CONTROL  The GFS control run shows little significant differences in weather at the surface to the GFS operational with just small but subtle differences in the positioning of the High near or over the UK making local variances in the amounts of cloud and temperature levels the only major comparison day to day in the sustained High pressure pattern throughout.

THE GFS CLUSTERS The GFS Clusters show a 45% likelihood of High pressure across Southern Britain in 14 days time while 50% go for a Low pressure based pattern with the UK under Westerly winds. The remaining 5% shows a cold Northerly flow between High pressure to the West and Low to the East.

UKMO UKMO this morning shows a strong build of pressure from the Atlantic lying to the West of Ireland by next weekend extending a ridge across the UK. The weather would stay cold and bright with sunny spells by day and frost at night. Winds will remain NE but light over Southern England while a slightly stronger NW flow over the NW brings less cold and more cloudy air over these areas at times next weekend.

THE FAX CHARTS The Fax Charts differ little from the UKMO raw output data this morning.

GEM GEM today shows High pressure gradually taking control of the weather as we move through the latter part of this week as an intense High centre positions itself close to the West of Ireland late this week and then just meanders around close to the UK for the remainder of the run. The weather would become benign and rather boring in type with successive days of bright and dry weather with some sunshine but with variable and sometimes large amounts of cloud especially over the North. Temperatures would ease up with time but frosts at night would remain commonplace where skies clear.

NAVGEM NAVGEM today maintains the High pressure theme of the rest with the positioning crucial in whether the weather be cold or not. The South is shown to stay cold with something of an east or NE breeze whereas the North may see less cold air filter across from the NW at times later in more cloud cover.

ECM ECM this morning also shows High pressure becoming the dominant feature of the UK weather over the period once we lose the Cold and unstable North and NE airflow over the UK until later in the week. The High then slowly sinks from a position over or to the West of the UK to a point to the SW with milder and stronger Westerly winds gradually taking hold for many by Day 10 though any rain looks largely restricted to the North.

ECM 10 DAY MEAN The 10 Day Mean this morning indicates the trough currently over Europe relaxing away East as pressure rises to the South of the UK (including to the S) indicating a slow return to Atlantic Westerly winds and milder air by the middle of next week.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The trend has maintained universal support from the models for High pressure to be situated near the UK from later this week on with modified cold conditions persisting in fine and benign conditions.

MY THOUGHTS Well if you like large mid latitude Winter High pressure areas near the UK then this morning's outputs should float your boat as almost without exception all models show a period of a week at least where such a High will dominate the weather over the UK. We first have to lose the cold North then NE flow of this working week with snow showers numerous in the East for a time but lose them we will over next weekend. The High through the period will be ridging in towards Scotland and will intensify too bringing sustained dry and bright weather with overnight frosts and bright days. The positioning of the High will be crucial in how things are at the surface but with most models looking like keeping it just to the West of the UK a slack NE flow could be maintained over the South while a slack NW flow in the North will most likely encourage a gradual infill of cloud from the Atlantic though much in the way of rain seems unlikely. Temperatures look like being on the cold side of average especially in the South though daytime maxima are likely to ease upwards with time while night minima will be reflected upon whether there is cloud cover or not though it seems inevitable that frost at night will feature prominently especially in the Central and Southern regions of Britain. Then the longer term ensemble members of GFS and ECM in general indicate a sinking High gradually bringing more and more of the UK in milder and perhaps more changeable Westerly winds with rain at times by the end of next week and the second weekend though the speed and extent of this is speculative given the time range. So in summary if it's snow your after I'm afraid it is looking increasingly unlikely that anymore large scale snowfalls look like happening under this current cold spell with the window of any opportunity closing further as the week progresses and the fine, bright and rather cold conditions of a large slow moving High pressure area takes hold.

Issued at 08:00 Monday February 2nd 2015

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Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .

The Southern part of Britain will have a good 5 days of cold in prospect with a keen wind later in the week making it feel very cold. Still a snow risk for the Southeast Wed night into Thursday. Will be able to update snow portal forecast later today. Yes, Nick still time for changes for a more favourable positioning of the high and the European Low to develop a surprise !

C

Yes still time and the ECM control run looks to keep the cold to the 13th:

 

http://www.weerplaza.nl/15daagseverwachting/?r=midden&type=eps_pluim

 

We do need though to see some improvements in the upstream pattern especially with that deep low at T120hrs to get the high into a better location.

 

Regardless the recent spell has brought a big improvement for the Alps and Pyrenees, some resorts in the western Pyrenees have received as much as 200cms of new snow!

 

We even had some here lower down and more expected tomorrow which is a vast improvement on last winters dismal attempt at winter.

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Posted
  • Location: Stroud, Gloucestershire
  • Location: Stroud, Gloucestershire

We have had an interesting period last week, with a brisk northerly delivering snow on several places across the UK. There seems to be a change in the pattern underway, with high pressure activity probably taking foothold over Western Europe. How does this pattern evolve, and how can high pressure activity still cause a lot of uncertainties? In this post, I will try to give an answer to these questions.

 

For the first 96 hours, I will use the GFS 12Z/18Z runs as a general guide.

 

Current synoptics

 

For the current situation, take a look at the GFS chart below:

 

attachicon.gifGFS_00_EDIT.png

GFS surface level pressure and 500 hPa heights (Colours) 18Z run T0

 

As can be seen from the image, a large 500 hPa trough (blue colours) extends over the center of Europe down to the Mediterranean. A complex area of low pressure at the surface is associated with this feature.

 

This trough has been influencing our weather over the past few days. Northerlies blew on the western side on the trough. Also, because the 500 hPa temperatures (not shown here) were very cold at the center of this trough, the air was very unstable (expressed by a big difference in temperature between the surface and aloft). This made formation of showers possible, which were carried southward by the northerly flow, bringing rain and snow toward the UK.

 

Aside from this trough, a 500 hPa ridge can be seen building over the Atlantic (orange colours edging northward), also visible by high pressure at the surface. This ridge will be important for our weather over the next week.

 

Transition to high pressure activity

 

Looking 48 hours later, the same general pattern as described above is maintained, but with a few crucial differences.  Check the GFS chart for 2 days ahead below:

 

attachicon.gifGFS_48_EDIT.gif

GFS surface level pressure and 500 hPa heights (Colours) 18Z run T48

 

The 500 hPa trough located over central Europe is still there. However, there are two important things happening, being:

  • The trough is weakening, as the dark blue colours (indicative for very low 500 hPa heights) are now longer visible.
  • A piece of the trough is willing to dive southwestward (indicated by the black arrow). This movement will be very important for future developments.

Also, the 500 hPa ridge (orange colours edging northward) is still visible, but has moved some westward and is now located just to the west of the UK. Also note the orientation of the high has shifted some into a NE-SW orientation, basically pushing itself over the piece of the trough (over France) which is trying to move southwestward under the ridge.

 

Another 48 hours later, the developments mentioned above have continued, as can be seen below:

 

Rtavn961.gif

GFS surface level pressure and 500 hPa heights (Colours) 18Z run T96

 

The ridge which was located to the west of the UK 2 days before has now moved over the UK, yielding a strong area of high pressure at the surface (up to 1035 hPa).

 

Furthermore, the 500 hPa trough which was located over central Europe has been separated into a part that has shifted out of Europe, and another part which has become partially cut-off over Italy (blue colours). As a refresher, a cut-off low is a low pressure area that is separated from the mean flow by means of high pressure activity to the north of it.

 

The result is a high-over-low situation, which can be seen as a blocked pattern. This can also be seen on the Jetstream patterns as given by Netweather, which can be found in the following image:

hgt300.png

Netweather Jetstream analysis from the 12Z GFS run valid for 96 hours out.

 

Note that the jet stream is very wavy and inactive, indicative of a blocked pattern.

 

(Un)certainties in future outlook

 

The situation described in the previous outlook is not expected to change much over the days to follow. However, small differences develop between the models, which may have significant implications for the weather across the UK. For example, compare the GFS and ECMWF MSLP forecasts for 7 days out:

 

http://www.wetterzentrale.de/pics/Recm1681.gif ECMWF

http://www.wetterzentrale.de/pics/Recm1681.gif GFS

 

As can be seen from the models, both agree that a strong 500 hPa ridge will be present over the UK (as indicated by the orange colours).  This provides enough certainty to conclude that high pressure activity will be likely by the end of next week.

 

However, there are small differences in the placement of the surface high pressure, with the GFS being much further east with the high pressure area than the ECMWF. Also, the 500 hPa ridge (and associated surface high) on the ECMWF is somewhat stronger  than on the GFS.

What makes these differences so important is that placement of the surface high to the east or west of the UK has major implications on the weather expected there. If the ridge would appear to be located to the east of the UK, a southerly flow will be present over the UK bringing mild weather. On the other hand, placement of the ridge to the west of the UK would result in a cool northerly. This uncertainty is reflected nicely in the wind distribution of the ECMWF ensemble for the Netherlands:

 

epsroos_260.png

ECMWF wind distribution of 50 individual calculations 00Z run, 1 February.

 

The image indicates a set of wind vanes, each for a different time step. Each sector stands for a different wind direction. For example, the upper segment indicates northerlies, while the right-hand sector denotes easterlies, analogously for the lower and left sector. The distance from the center is the strength of the wind expected. The further away a run from the center is, the higher the wind speed will be. The green triangles denote a single ensemble run forecast for the wind speed and direction. The blue and red triangles are the Control and the OPER run, respectively.

 

When the triangles are very close together, it means there is a high certainty of the expected wind, while a large spread indicates uncertainty.

 

What can be seen is that from about 168 hours, a large disagreement between the various ensemble members develops regarding wind direction. Basically everything except a southeasterly is possible, with equal chances for each of the other wind directions. All models do agree, though, that the wind speed will not be high.

 

This spread can be linked to the synoptic situation discussed earlier by the high pressure area positioning near the UK. A very small deviation in the positioning of the center of the high may result in a complete turnaround of the wind direction to be expected, and the expected temperature.

 

Regardless of this spread, the fact that high pressure activity seems to be dominating our weather for a significant period of time is pretty certain. To illustrate this, take a look at the precipitation ensemble ‘pluim’ from the ECMWF:

 

eps_pluim_rr_06260.png

ECMWF ‘pluim’ of precipitation for the Netherlands, showing 50 individual model calculations of the ECMWF model regarding precipitation (green lines). The red line is the operational run, while the blue line is the ‘control’ run.

 

Over the next 15 days, almost no model is calculating any precipitation to fall. It does take up to 13 February to see some members calculating a decent amount of precipitation. As high pressure is often accompanied by a lack of precipitation, this is good evidence that high pressure activity will dominate for the next several days.

 

Boundary-layer and high pressure activity

Of a final note, even if the location of the high pressure is certain, the weather over the UK can still be uncertain even up to the day itself (say, 12 hours out). This has to do with boundary layer dynamics, which are crucial in high pressure activity. The boundary layer, in general, comprises the lower 100m to 1 km of the atmosphere (the area where we ‘live in’).

 

Questions like: “What will be the height of the subsidence inversion caused by the high pressure area?†and “What will be the humidity of the surface air and?“ are of high importance. This can be the difference between a day full of sunshine, a day of cloudiness, or in the worst case a day of only fog. Therefore it has to be kept in mind that even if the general synoptic pattern is clear, the forecast for the actual weather being observed may not be that certain at all.

 

Conclusion

 

A pattern change is about to occur at the beginning of next week, with high pressure activity taking over. There seems to be a fairly high level of confidence that this will last for a week or even more. However, there are still small disagreements on the placement of the surface high, which will have major implications for the weather experienced across the UK; directly by means of wind direction and indirectly by boundary layer dynamics. Therefore, the models can be watched with interest.

 

Sources:

http://www.weerplaza.nl/15daagseverwachting/?type=eps_pluim

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

http://www.wetterzentrale.de/topkarten/fsecmeur.html

http://www.knmi.nl/exp/pluim/kansverwachtingen_staafdiagram.php?run=00&type=precip0618

 

Just catching up on last evening's posts and, as someone who does not feel qualified to reply in depth to many of the posts. I have to say that this is possibly the best post I've ever read on here in the past few years. A beautiful explanation of your thoughts, which took me quite some time to read as I was able to click on and digest your explanations at every stage. A perfect post for those who might be new to this thread.

 

Thank you so much Vorticity 0123. You have restored my faith in this forum!

 

Peter

Stroud

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Posted
  • Location: leicester
  • Location: leicester

gfs 06z agrees with the ukmo and ecm now regarding cold air making its way in from the east Wednesday/thursday! ! Has colder 850s further west and north compared to 00z!!

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Posted
  • Location: chellaston, derby
  • Weather Preferences: The Actual Weather ..... not fantasy.
  • Location: chellaston, derby

the noaa anomaly charts suggest the coming high pressure dominated pattern will see the high centred just to our west or south of west? after a breif northeasterly as the 6-10 dayer suggests.

 

post-2797-0-37001000-1422871517_thumb.gi post-2797-0-16956700-1422871501_thumb.gi

im still expecting it to be a dirty or cloudy affair by the end of weekend as 'less cold' air is drawn down across the country in the anticyclones circulation.

but the good news is that its looking dry....

 

 

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Posted
  • Location: Peterborough N.Cambridgeshire
  • Location: Peterborough N.Cambridgeshire

I do have to question the interpretation of the model output by some members. Saying the ECM only has slightly colder upper temps in the reliable timeframe isn't correct. At +168 (9th Feb) the difference between the GFS 0Z & ECM 0Z is just a mere 10C!!

 

Like I said last night im going to remain open minded with regards to the placement of the HP. Just look at the difference between the 0Z ECM at +168 and the 06Z GFS!

 

http://www.wetterzentrale.de/pics/Rtavn1622.gif

http://www.wetterzentrale.de/pics/Recm1682.gif

Edited by TEITS
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Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth

Quite a big model divergence appearing by T168; ECM as already mentioned keeps the High out west leading to northerlies, but the GFS once again shows no interest and instead brings the High over the UK, slowly sinking into Europe - still not warm. Although by T192 we're potentially headed for a southerly!

gfsnh-0-192.png?6

Where we would go from that not too sure but I can't see a quick return to deep cold. However, since UKMO/ECM agree on keeping the High to the west, I'm inclined to believe that is the direction of travel, which leaves the pattern open to further troughing diving into Europe over the top of the High.

 

One more thing that is bugging me - why does that Aleutian low keep reappearing? Is there a meteorological reason for this, anyone? Can't remember any other year like it. 

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Posted
  • Location: Reigate Hill
  • Weather Preferences: Anything
  • Location: Reigate Hill

I do have to question the interpretation of the model output by some members. Saying the ECM only has slightly colder upper temps in the reliable timeframe isn't correct. At +168 (9th Feb) the difference between the GFS 0Z & ECM 0Z is just a mere 10C!!

 

Like I said last night im going to remain open minded with regards to the placement of the HP. Just look at the difference between the 0Z ECM at +168 and the 06Z GFS!

 

http://www.wetterzentrale.de/pics/Rtavn1622.gif

http://www.wetterzentrale.de/pics/Recm1682.gif

 

Hi. ECM op is notorious with fails when we have a transition from trough to HP (or vice versa) and the op has been against its mean for the last few runs. The ECM op and mean uppers clearly show the op solution is at the cold end of its members:

 

post-14819-0-91860200-1422873309_thumb.g  post-14819-0-40903800-1422873310_thumb.g

 

Its solution re the westerly placement of a second pulse of HP at around D4-5 is still rejected by the GFS 06z op and I suspect it is wrong, and it appears that it's members agree.

 

Subtle differences on the 06z re the core UK heights, slightly further east: post-14819-0-77391100-1422873500_thumb.p

 

Though the upper flow remains slack so although 850's above current numbers (+12c difference) the surface temps under the high may be very similar to the current synoptics!! That is more a reflection of the disappointing wintry output from this Euro trough. 

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Posted
  • Location: STEVENAGE, HERTS (100M ASL)
  • Location: STEVENAGE, HERTS (100M ASL)

GFS 06z is another borefest from next weekend.  ECM is the only model this morning that still brings a bit of interest and extends the cold spell by a coupIe of days. Personally I just pray that the high doesn't stick around too long as it is just waiting a week or so of winter. Hopefully we see something akin to the ECM and a bit more amplified so we can eek a little extra out of this cold spell before then. Met office are still talking about the Atlantic coming back in with rain preceded by snow. All i can see from the models is a High coming in and blocking the Atlantic. I expect this will change in their update today!?

 

"There is a risk of more widespread rain and snow over north-western parts from Saturday as conditions are likely to become more influenced by the Atlantic. Temperatures gradually becoming less cold here, although the transition period will have the potential for further snow in places."

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Posted
  • Location: Freshwater Isle of Wight
  • Location: Freshwater Isle of Wight

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

 

Latest 8-10 day 500mb charts both ECM and GFS show a sustantial block in the east Atlantic which has gradually evolved over the last few days. The slow but steady evolution and with little change from yesterday could be a sign of some stability to this pattern. The Azores high is displaced to the north being propped up by the upper trough that is shown to extend ever further westwards from the Med to the Azores. The cold spell originally predicted to end tomorrow looks likely to continue for a while yet at least in the south. 

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Posted
  • Location: st albans
  • Location: st albans

Extended London eps continue to trend to less 'continental type' blocked in the 10/15 day period with very few really cold T2Mx runs remaining. Whilst it looks calm and dry, the mean maxes now above 5c.

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Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .

The divergence upstream continues on the GFS 06hrs run with it resolutely sticking to its view. The ECM and UKMO in one camp, the differences are quite amazing given the timeframes involved.

 

Essentially tonight we're going to see an epic fail from either the GFS or the Euros with the rather embarrassing scenario of one camp calling the pattern wrong within T96hrs.

 

Last night I would have put the ECM as the outlier solution but that's now backed by the UKMO at T96hrs with the coastal low off the ne USA. The odds on both these models being wrong together at T96hrs is very low.

 

Anyway we await tonight to see which model/s reputation will either be enhanced or trashed!

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Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth

Looking very, very dry into early next week, according to the GFS ensembles. Very high pressure dominated, one way or another. Snowfall opportunities looking about zero after Friday now.

 

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=216

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Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .

In relation to my previous post here are the ECM,UKMO and GFS to the same time Midday Friday:

 

ECM:

 

post-1206-0-47508800-1422879251_thumb.gi

 

UKMO:

 

post-1206-0-82001700-1422879270_thumb.gi

 

GFS:

 

post-1206-0-30492300-1422879290_thumb.pn

 

You'll see the ECM and UKMO support each other with the pattern in the ne USA, the GFS overdevelops that shortwave south of Greenland and has a trail of weak shortwave energy towards Florida.

 

The reason these early differences are important is that any northerly next weekend relies on the ECM/UKMO view, the only reason the ECM has a chance to advect some colder air back in to the UK is the T96hrs low upstream, this runs ne and allows the high to retrogress more, the UKMO is weaker and flatter with that low but its set up is at least in the same ball park.

 

So tonight we'll see which model has called this correctly, even with the ECM we'd still need the upstream low to run more inland however its game over if the GFS is correct, you simply won't get the high in a more favourable position with its upstream set up.

 

 

 

 

 

 

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Posted
  • Location: winscombe north somerset
  • Weather Preferences: action weather
  • Location: winscombe north somerset

No guarantee but high pressure looks like setting up shop over our shores later in mid term .but looking out into longer range especially on ECM today the possibility of low pressure moving in to Scandy and a mid atlantic ridge setting up . i think give the models a couple of days and we could be chasing the next seperate cold spell  or the continuation of current, its that way at the moment with models trying to pin down the centre of our Anticyclone ,sudden surprise snow outside now very light but wasn,t expecting that ,lets hope for a big upsurge of interest tonight ,cheers gang  :drinks:  :cold:

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Posted
  • Location: South Essex
  • Location: South Essex

Looking through the GEFS, out of 21 possible solutions (ie 20 plus control), 20 of them have the high over the UK at 192 hours.

 

The irony of course is that despite the fact that this will no doubt sit nearby for days and days, the pattern isn't actually a 'blocking pattern'. The high just acts much like a small rock in a stream. The pattern is really zonal with weather systems simply flowing over the high.

 

For much of continental Europe it is potentially a cold pattern, but for us its just a bore fest unfortunately.  

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Posted
  • Location: Fazendas de,Almeirim, Portugal
  • Weather Preferences: The most likely outcome. The MJO is only half the story!
  • Location: Fazendas de,Almeirim, Portugal

The pattern as has evolved over recent days is a very good illustration of where, on a northern hemispheric level, things have actually accorded quite well with expectations (i.e Atlantic amplification and Euro trough) Then, also in follow up, the broad-scale suggestion of that ridge strengthening towards a blocked pattern with a further retrogression signal starting to come into view. It is the upcoming period and that longer range amplification signal that provides the next headache

 

I think it is on this basis that the use of longer range tools such as the AAM/GWO circulation and stratospheric modelling to try to predict opportunities for colder spells (and any other type of weather pattern obviously) has its true worth and value. The worth in learning about these tools is invaluable imo because, as I have discovered especially this winter, it is possible to spot some distance out when the next opportunities for a cold pattern might arise (as well of course what the problems might be in achieving those opportunities, or trying to decide whether any desired colder pattern might arise at all)

 

We have seen this winter just how enigmatic the signals have been -  we have only had at our disposal an atmospheric circulatory signal that has provided periodic Pacific > Atlantic pattern retrogressions and attendant amplification signals heading from upstream> downstream. It has not been driven by an anticipated Siberian -AO signal for northern blocking to evolve

 

The regularity of the cyclical nature of the atmospheric pattern has in truth made anticipating the way ahead relatively easy- even though it has not been the best of news. The GWO orbits this winter have featured  -AAM phasing between 1,2,3 and 3,2,1 in the first half of the winter - but have progressed to a higher amplitude phasing  (Phases 4/5 to 8/1) in the second half on the winter so far that have increased the same amplification signal of the first half of the winter and has also enabled the stratospheric profile to change through increased torques and MT's which has shaken up vertical wave activity and assisted us with a displaced vortex

 

However, this is a perfect example of where the atmospheric circulatory pattern has progressed to achieving macro scale improvements to a frustrating and enigmatic winter pattern,  but, these are still only improvements within the limitations that the dominant background pattern allows - and these better opportunities still cannot ever guarantee the precise 'will it snow' close  details that so many of us crave on this forum.  

 

The UK, is a micro dot, in that broad-scale hemispheric context, and as we know especially when we are restricted by a pattern that is not predisposed to HLB in the heart of the winter, then it is going to be even harder to come close to fulfilling the potential wintry parameters that such a broad-scale pattern offers.

 

This illustrates exactly why my own posting leaves the closer examination of possibilities to others to comment on - and we all hope very much that these are in our favour.

 

So, as to the way ahead?

 

That GWO orbit continues with repeated rinse and recycle signal. The MJO phase cycle teleconnects to underpin the anticyclonic Feb spell - and the constant retrogression signal remains (we see the ECM picking up on this).

 

The uncertainty for me is what is likely to happen to the vortex, in terms of movement and re-organisation. We are losing the displaced signal, but we have further wave activity to consider and the GWO orbit tells us this. Phase 4/5 (which is the here and now) signals a second imminent +EAMT and this should assist to try and re-shuffle vortex energy back towards our side of the pole after the upcoming transfer across the pole to Greenland.

 

An example here of timing being the essence. Timing of an amplification signal with vortex energy transport across the pole is very hard to gauge - and it is here that the fate of the latitude of our current amplified Atlantic ridge has rested. Wave activity over Asia courtesy of EAMT is set to be followed by further vertical wave activity the other side of the pole as the GWO orbits through phases 8/1 and into the next Pacific retrogression signal... that the ECM is picking up on already.

 

So, in summary, we get some assistance (repeat circuit of late Jan) from another +EAMT for vortex movement to our side of the pole (GWO 4/5) and then we get a subsequent -MT for upstream Atlantic amplification (Phases 8/1/2). Sounds familiar.

 

http://www.atmos.albany.edu/student/nschiral/research/gwo/gfsgwo_1.png

 

Mention has been given before of eventual translation of this amplification pattern to an HLB scenario. This, with an underlying weak El Nino to hand (which traditionally favours the second half of winter for cold spells) has been perfectly plausible based on some reasonable expectation that the inner core of this (swear filter) vortex would burn. However, thus far it has managed as a relatively weak and unstable feature to escape such a torching.

 

The changing wave lengths will make a difference there is no doubt - the question is will this provide the optimum synoptics in the Spring, if they arrive at all, rather than the last part of February? Its still too early to answer that question, and there is time yet for sure - but for now eyes anyway on this next retrogression signal. There is another plunge of cold air on its way to supplement what exists to our north and east.

 

How much within the limitations of this cyclical quasi upstream>downstream amplification recycling can we squeeze out, without Europe to our east and south being the total beneficiaries once more?

 

@ john H. You might want to re-interpret what is meant by the rinse and recycling theme I refer to. The atmospheric signal might be repeating, but that does not automatically mean I am referring to one single outcome @ Woolymummy - thanks, and yes, I learn that way too :)

Edited by Tamara
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Posted
  • Location: Boar's Hill, Oxon
  • Weather Preferences: Interesting weather
  • Location: Boar's Hill, Oxon

Thank you so much Tamara for all your posts, I am learning so much from them and understanding more and more each time.

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Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

To me the pattern is pretty clear, a cold showery N-NE flow for 1-3 days then this being replaced by a more anticyclonic pattern out to about days 8-10 with a more westerly upper pattern following after that. Out to 15 days I see little signal of any 'rinse and reload' or whatever else term anyone wishes to use for a return to deep longer lasting cold?

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Posted
  • Location: STEVENAGE, HERTS (100M ASL)
  • Location: STEVENAGE, HERTS (100M ASL)

Incidentally, one thing we've been watching for since EC-EPS output yesterday is potential for another colder N'ly later next week, depending on high orientation. One to watch.

 

If Ian F is reading I (and i'm sure other readers) would love an update on HIS view for the potentail Northerly late in the week / next weekend.  He also mentioned in the SW thread about snow reaching quite far west (to the east of his region) on Thurs with "Bothersome" snow possible for the SE.  Does HE think the Meto to firm up on this & issue warnings soon?

Edited by Tim Bland
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Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

If Ian F is reading I (and i'm sure other readers) would love an update on EC-EPS view for the potentail Northerly late in the week / next weekend.  He also mentioned in the SW thread about snow reaching quite far west (to the east of his region) on Thurs with "Bothersome" snow possible for the SE.  Can we expect the Meto to firm up on this / issue warnings soon?

 

There is a difference between the interpretations Ian may give on here and what the senior man at Exeter actually posts within the confines of those able to read these outputs.

Perhaps I should have written the interpretations some on here may give to the posts that Ian makes?

Edited by johnholmes
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