JH and a look into the period from T+144, usually

[PB22]

Following on from my post a few days ago, we can see how things have changed as we look into the 5-10 day period.

I had thought the models may have sorted themselves out a bit by now, but still we can see that as soon as T+96 hours out, just four days the models still diverge greatly:

GFS:

UKMO:

ECM:

Again, the basics are in place, the high to the south, the low over Scandinavia, the ridging of the high to the south northwards, the area of nothingness to our northwest. As we can see, the GFS puts us under a weak northerly for Monday with a ridge of high pressure over the UK by T+120. The UKMO has high pressure ridging northwards across the country before a low appears at T+120, whilst ECM has a weak high over Iceland having more influence but low pressure developing over the UK by T+120. These are relatively small differences in the grand scheme of things, but as I explained the other day it is these small differences that could end up making a difference and affecting what eventually happens further down the line.

Again, this is shown by what each model produces later on down the line. UKMO shows high pressure re-building over us. The ECM has a ridge of high pressure moving across the country before the Atlantic returns. Meanwhile, GFS is somewhere in between, with a stronger ridge across the country, but again the Atlantic wins out.

Lets see what the FAX charts devised by the boys at Exeter show:

They have gone along the lines of this mornings UKMO and ECM output, delaying this ridge of high pressure moving in. Ok, lets look at the GFS panel maps (from the 06Z run for Monday):

Interesting, they all show high pressure ridging in at T+120, the opposite of the UKMO and ECM. Who will win this I wonder?

Looking at the various GFS ensemble charts doesn't enlighten us any further really.

For West Midlands:

Pressure:

Pretty good agreement on high pressure taking more control as we go into next week.

850hPa temperatures:

Quite a split for early next week, but generally its a rather mild outlook.

2m temperatures:

Now this is rather interesting, quite a wide range to be found. This suggests to me that whilst there is good agreement on high pressure becoming more of a feature over the UK, there is considerable uncertainty over where it will be centred, which will in turn affect the air source and if we develop an inversion with high pressure over the UK. As we can see, several runs suggest a possible inversion situation developing.

So where could this potential high be situated if it wasn't over the UK? Well looking through the European ensembles, we can see a clear suggestion of pressure being high to our east and northeast after next weekend:

Nothing paticularly high though, especially when compared to Paris:

I think that tells us all we need to know, high pressure to the south or southeast of the UK is likely to ridge north or northeastwards, meaning that the UK will generally stay on the mild side, with winds from off the Atlantic. There is no sign of pressure falling over France or Iberia, and until that happens nothing will change greatly. Combined with that, we would also need heights and pressure rising over Greenland, and again, there is no sign of that happening with the Polar Vortex continuing to take up residence over Greenland.

To conclude we are likely to see high pressure to the south playing more of a role in the UK's weather as it ridges in, but unless it actually builds over the UK, then we are unlikely to see anything in the way of cold. I would suggest that southern areas will become more settled with time, but it will stay rather mild, whilst northern parts are likely to see more in the way of unsettled conditions. I would also suggest that this pattern won't change for some time yet, meaning much of the rest of January will be very depressing for cold and snow lovers.

Edited January 17, 2008 by Paul B

[Peter Henderson]

I would also suggest that this pattern won't change for some time yet, meaning much of the rest of January will be very depressing for cold and snow lovers.

It certainly looks that way Paul. Take a look at the charts on this great site:

http://www.ukweather.freeserve.co.uk/nwp.htm

Here's Feb. 2nd:

http://85.214.49.20/wz/pics/Rtavn3841.png

http://85.214.49.20/wz/pics/Rtavn3842.png

That actually looks quite promising but, it's over two weeks in the future and it does keep changing every six hours or so. The other depressing thing is that the mild air has pushed well into central/northern/eastern Europe now as well. It's very mild over Austria, Germany, and Scandanavia for example so even if things do change it'll take a while before it can become really cold. Here's the charts for five days ahead:

http://85.214.49.20/wz/pics/brack4a.gif

http://85.214.49.20/wz/pics/Rtavn1201.png

http://85.214.49.20/wz/pics/Rtavn1202.png

It looks depressingly mild/wet and windy

Edited January 17, 2008 by Peter Henderson

[acbrixton]

Paul many thanks for an admirably clear and readable analysis.

regards

ACB

[PB22]

Time for another analysis. Lets see if we can get any consenus for the 5-10 day period.

Looking at the 00z runs, the models are now in good agreement for the T+96 time frame:

GFS:

UKMO:

ECM:

So a deep low to the south of Greenland, high pressure to the south of the UK and the country under mild southwesterly winds. Just the pattern a lot of us don't want to see in January! The key thing is the agreement between the models, and this stretches further out, with both GFS and ECM developing that high to our south even further (up to 1040mb+) and it moves northwards a touch.

Looking at the GFS ensemble panel map for T+168, we can see very good agreement for a strong high pressure to be sat close to or just to the south of the UK:

Looking at the various GFS ensemble graphs further backs up the evidence of a good agreement.

For West Midlands:

Pressure:

Pretty good agreement on high pressure taking more control as we go towards the end of next week.

850hPa temperatures:

Again, reasonable agreement. A couple of colder snaps, but generally the evidence for agreement on the general set up is there.

2m temperatures:

Consistent once again. This suggests to me that there is good agreement on high pressure becoming more of a feature but that it will probably sit just to the south of the UK, thus preventing a potential inversion with colder weather setting itself up. Going by all of that, it seems that we will remain in a relatively mild flow from off the Atlantic for some time yet, with the odd exception in the first part of the coming week as shown by the 850phPa chart.

For confirmation of high pressure being centred to our south, lets check the Paris ensemble:

Again, that tells us all we need to know, high pressure will be centred to the south or southeast of the UK, meaning that the UK will generally stay on the mild side, with winds from off the Atlantic. Pressure begins to fall by the end, but thats too far away to take any notice of really. Combined with that happening, we would also need heights and pressure rising over Greenland, and again, there is no sign of that happening with the Polar Vortex continuing to take up residence over Greenland.

To conclude then and its more of the same following my round up the other day. For the 5-10 day period we are more than likely to see high pressure to the south of the UK, but it may ridge into southern Britain at times bringing some drier conditions to the south at least, but not necessarily sunny. Northern and western Britain look like seeing the more unsettled conditions, demonstrated nicely by these two ensemble charts for precipitation - one for the southeast:

And one for the northwest:

In all probability, this set-up looks like taking us into February. Perhaps things will change then?

[Greyowl]

Thanks for carrying this thread on Paul. Nice and easy to understand.

[PB22]

Thanks Greyowl and everyone who commented earlier.

If anyone else wants to add their detailed analysis to this thread, then please feel free to do so. All detailed contributions are welcomed!

[PB22]

Time for another analysis. There are some signs of some changes in the 5-10 day time frame, and the chance of things turning colder perhaps.

Looking at the 12z runs, we can see that the models are in good agreement for the T+96 time frame:

So a deep low to the west of Iceland, another low to the north or east of Scandinavia, and high pressure to the south of the UK over France, leaving the country under mild southwesterly winds. The key thing to longer term developments can be the agreement between the models, and this stretches out as far as T+144. By that stage, most models are developing an Atlantic high, which looks like it may potentially be part of the change to a colder pattern as we head towards February. Lets try and find out more by looking at the GFS ensembles.

Looking at the GFS ensemble panel map for T+168, we can see reasonable agreement for an Atlantic high pressure with a possible link up to Greenland:

Looking at the various GFS ensemble graphs further backs up the evidence of a change to colder conditions as we head into February:

For West Midlands:

Pressure:

A wide range of options by the start of February, so not a lot of confidence to be gained from that.

850hPa temperatures:

Reasonable agreement of things turning colder as we go into the new month.

2m temperatures:

Consistent with regards to a cooling off in a week or so's time

Precipitation:

Indications of conditions turning wetter at the same time as it gets colder. This could mean northwesterly winds bringing showers or more unsettled conditions moving in from the Atlantic, or something else altogether!

Lets see whats forecast to happen to the high pressure thats going to be the dominant feature to our south over the next few days - here's the pressure ensemble for Paris:

Interesting, all runs are going for a slight fall of pressure, but a great deal of uncertainty then sets in once pressure has fallen somewhat.

OK, now as there is the chance our weather may eventually come from the northwest, lets check out Iceland:

Pressure:

This explains a lot. A brief rise of pressure over Iceland around the month's end, but good agreement on low pressure soon returning.

Sure enough, a quick look at the 850s for Iceland shows a cold snap before it turns less cold again:

Finally, a look at the ECM ensembles for De Bilt in Holland: http://www.knmi.nl/exp/pluim/Data/PLUIM_06260_NWT.png

Reasonable agreement on things turning colder for a time over there, but again it looks like it may be shortlived.

Conclusions: Definitely suggestions of a change in the medium term, with the prospect of a colder snap from the north or northwest developing. At the moment a lot of the output indicates that if a cold snap does occur, then it will be a very brief one. We're still a long way from a change, and things will undoubtedly change over the coming days, but at the moment I would put my confidence at 40% of a brief cold snap occuring around the turn of the month.

Edited January 23, 2008 by Paul B

[johnholmes]

I'm re starting this topic with looking into what the models seem to be suggesting to me in the LRF time frame, that is T+120 and onwards out into lal la land!

this is posted 1937Z Thursday 31 January 2008

the two charts above do seem to suggest that NOAA are not unhappy with the LRF part of the GFS latest runs. Its been tending to show this for a while so maybe, and the |UK Met O also seem to believe it, that HP is going to build in our area. Just what its exact position will be remains to be seen. If we look even further ahead, say T+240 with GFS

and it continues with the build of pressure.

By T+384 well into lal la land usually, and its still there

This is the current 200mb circumpolar chart

If we take a look at some of the ensembles, say Iceland, Lisbon and Helsinki just to give an idea what do we see in terms of pressure?

Iceland= mixed signals after about the 7th with pressure having been quite low it then has a wide spread 1030-<980mb !, the main body suggests pressure rising slightly but still fairly low, say around 1000mb.

Lisbon

By the 7th the pressure is pretty uniformly shown at around 1030mb, tending to tail off a little with some spread, generally about 10-15mb, to 1020mb

Helsinki

From about the 6th, falling generally but with a largish spread, around the 1010mb mark, the 'mean' shows a value of around 1010mb by T+384 but with a wide spread through the period, 1040mb to < 980mb.

So really not that much help here, although I suppose one could try and imagine HP as the dominant feature but probably south rather than north of the UK. This would be at variance really with what the T+384 shows(the operational run).

So it will be interesting to see how T+384 turns out at T+00, we only have to wait 2 weeks. By then winter will be almost over!

Just to add that the 12z outputs on the models all carry on in the LRF period with a similar idea.

charts following

Edited January 31, 2008 by johnholmes

[Roger J Smith]

I spy with my little eye

something beginning with B.

-----------------

The strong high depicted on the 12z GFS over Ireland in the FI time frame is probably a total figment. When has there ever been a 1050 mb high over Ireland since the last ice age ended? Expect the rather mild SW flow to continue into that period instead, and a peak of mild weather around the 15th to 22nd with a number of fairly strong lows moving along to the north of the British Isles.

Then there may be a northerly type event, near the end of the month or into very early March.

Otherwise, I think this two-day polar express is about it for the winter of 2008.

[johnholmes]

is that an answer to my post Roger? I don't see a 1050mb high on any of the charts I've posted?

[Roger J Smith]

No, it was a comment on what I saw on the 12z GFS earlier, some time well into FI they had a high building up to near 1050 mb over Ireland. I think it was gone by the 18z run. It could happen, if Ireland happens to be joined to Iceland by an ice bridge, I suppose. Been a while since that last happened.

I am beginning to think that the GFS programming for FI could use a bit of RJS theory, because the RJS model generally avoids 1050 mb highs over Ireland and such like.

[johnholmes]

Update on Friday evening 1st February

T+240 charts are not as far ahead as I looked last night but they are rather interesting

Here is the GFS and this is from ECMWF

They are not that different, certainly at this time scale, 10 days away. Both continue with the idea of HP somewhere in mid Atlantic,

GFS migrates its high east to be here at T+360(for comparison with the T+384 last night)

This is the 500mb predict chart issued today by NOAA

Again with not too much imagination it suggests some kind of higher pressure in mid Atlantic. That said it has no sign showing of lower values to the east of the UK, along with lower values over the Iceland area, so the GFS extension east seems quite plausible at the moment.

Interesting to see how it shapes up as we count down towards, first the current T+240 on Monday 11 February and the extended one of GFS at T+360 today for Saturday 16 February.

Just a comment on what I've been trying to do, with the 2 week break in mid January off skiing, is using various outputs, NOAA 200mb, their 500mb progs for about 6 days ahead, ensemble outputs for various places over northern Europe/Scandinavia, southern Europe, and seeing if anything seems to fit.

Its very early days but the 500mb prog by NOAA does seem to have some relationship to the subsequent 200mb northern hemisphere chart at about 6 days. This is encouraging but no more as its based on very little data.

I'll persevere with it and try and refine it as I go along. It may, I say MAY, give additional support to what GFS/ECMWF appear to be showing in the 6-10 day time frame. Beyond that and I've yet to see any way to try and check, similar to the events just described above.

Its very good for learning more about models and ensembles though, to me at any rate.

Edited February 1, 2008 by johnholmes

[Roger J Smith]

Well, I notice that the 1050 mb high is back at 216h for Ireland ... that may flatten out some of those big hills they have over there.

I am not that convinced that such a creation is possible, 1042 mbs, sure why not, but 1050, once in a decade perhaps. If it comes off, it should be rather cool at night despite the bland upper pattern supporting it.

Then it should subside into Europe and form the basis for a Bartlett of long duration (what again you say).

I used to work with a guy in a weather office who said, big low big high, and at first I just thought, well maybe he's nuts, then I learned what he was intending to say was, after a really deep low passes a certain point, nature likes to balance the books with a really strong high later on. So this 1050 mb high should be over Kirkwall if that's the case.

[johnholmes]

Just a very quick update for Saturday evening 02 February

The GFS chart for T+216 is pretty similar to the one last night for T+240

As is the ECMWF for the same time/date

both continue with the idea of a mid Atlantic high, just what its orientation will be at T+00 we will have to wait and see.

GFS in the longer term continues to move it east which is not surprising if you look at the jet stream over the same period, and by T+384 the surface high has almost disappeared with the jet as below

On the ensembles, using the usual places, the usual fairly wide spread on them apart from the usual fairly close agreement at Lisbon, fairly high as usual. It would suggest HP over Europe with low pressure over Iceland and lowish pressure for Scandinavia and Russia. This is largely based on taking the ‘mean’, which can be quite different from the control or operational runs on the models.

The NOAA predict for the period 8-12 February(similar to the T+216 GFS and ECMWF) also supports HP in the Atlantic into the UK and Europe with low pressure north west of Iceland into Greenland.

Thus we are in about the same situation as the past 48 hours with high pressure developing in the Atlantic in the period and then drifting east into the continent by the end at T+384 or rather T+360 now.

[mountain shadow]

Excellent summary John, but I'm not so sure the High would sink into Europe. The ECM 240 chart has a decent depression over Italy which would prevent such an event and perhaps allow retrogression into scandinavia, although I admit any retrogression would be short lived due to La Nina jet forcing.

[johnholmes]

to be updated this evening once ECMWF and Ensemble data is in and studied.

[johnholmes]

Update on Sunday evening 3 February 2008

This evening I'll do things in a bit more detail regarding GFS and ECMWF in the far reaches of F!, along with comparing the ensembles for various places, and taking a peep into the NOAA take on things.

The chart below is the GFS version at T+192 and alongside the T+240 for the same date/time to compare from doing this on 1st February.

HP is about the same and so is the LP in the Greenland area. However the LP over Scandinavia at T+240 has disappeared at T+192 to be replaced by a ridge of HP.

Note that the 500mb flow is quite different in the west between the two time scales.

And below is ECMWF for T+192=Monday 11 February 2008 with its earlier T+240 alongside it.

Its T+192 is quite similar to the GFS version re the HP and its position but with a different orientation (so important when we get to T+00), no suggestion of a ridge into Scandinavia. Its T+240 version is really rather different in that ECMWF did have quite a nw type flow down its eastern flank, this is not so on the T+192, at least over the UK.

Essentially though both models out to T+192 and if you take a look at their T+240 outputs both keep the idea of HP near to the UK.

First the ECMWF, a fairly marked trough over the country with the Atlantic ridge elongated into the southern part of Europe and another centre west of it appearing to be trying to ridge towards Greenland.

The GFS version alongside it prefers a single HP also with some suggestion of a link to the north west trying to develop but it is really quite a different looking chart. Particularly with reference to the marked 500mb trough in the far west.

So the two main models continue with this HP in the central Atlantic. Its orientation, as ever, crucially important if you are a cold/snow lover! They also differ in a very crucial area, the far west and the 500mb trough shown on the GFS chart.

So what about the NOAA take on things?

This seems to suggest they expect a 500mb trough over the eastern areas by next Sunday (T+168) which fits in with what we see being predicted over the central Atlantic by GFS rather than ECMWF. Their comments are that they have adopted the idea of a 500mb trough over the eastern side by Sunday (T+168).

Their latest 500mb predict for the period covering out to 9-13 February(T+240 by 13/02) shows this:- a large positive pressure anomaly just west of the UK extending west towards the southern tip of Greenland and into Novia Scotia with negative anomalies for most of the USA/Canada region.

How about the ensembles?

This is the map I'll plot what I feel are the majority pressure values for the sites shown, not necessarily the official means. By all means look yourself and challenge my suggestions.

You will have to believe me that I entered the pressures as honestly as I could

The pressures are for 13 February and do bear a pretty good resemblance to the GFS chart from the operational for that time. There is no data further west so its impossible to compare with the ECMWF feature further west in the Atlantic.

Taking this lets see where the T+384 12z run today would try and take us

For it to get to this position, a brief explanation. It steadily declined the high, in about the same position, having tried to link with pressure rises to the north west, to an elongated ridge from south west England out to the Azores. From there (T+336) it then moved to the chart below

Well a fascinating 60 minutes trip for me and I have no magic version to give you. But it is a pretty convincing idea out to about T+264. Beyond that I am uncertain of its path but, as I often say, time will tell, and this post will still be around for us to all look at when we get to the various time points. The first being Monday 11 February and then Tuesday 19 February.

I will not do any more in depth looks until that date but will keep entering brief updates for comparisons to be made on the two models.

bear with me whilst I TRY and get all the charts up in the right order!

Edited February 3, 2008 by johnholmes

[johnholmes]

Brief Update tonight as strapped for time

To compare like with like it's the T+168 for Mon 11 February, first GFS. Its still going for HP as a major player but its position is a little different tonight from its original idea, but it still suggests a ridge out to the north east. The T+192 had less ridge but made more of the Russian trying to link towards it.

The ECMWF at T+168 shows more of a ridge to our north west with the main deep low not over Iceland but out over the far north of Scandinavia and much less of any sign of a 500mb trough to our east, the one to the west is slightly more pronounced than that with GFS. Its original was a bit different but still with a suggestion of a ridge to the north west and a deep low to our east, much closer than tonight's version which also showed pronounced 500mb troughs east and west with the main surface lows.

No time for anything further other than to show this ensemble for 'middle England'

It can't be that often that GEFS control and GFS Operational are that different by the end of the run, over 35mb on this!

adding this from NOAA and their perception of what differences from normal to expect on the 500mb chart in a similar period.

it suggests the area of +ve anomolies drifting slightly further east.

Edited February 4, 2008 by johnholmes

[johnholmes]

Update on Tuesday evening 5 February

Picking up where the T+96 from Paul B leaves off with HP looking fairly certain to be close by the UK as Paul indicates at that time frame.

Below is the T+144 for direct comparison at `12z Monday 11 February with the original T+240

GFS does tend on its next T+168 to show more like its original T+240 'look', in as much as it tries to link with higher pressure showing in the Greenland area.

Below this evening from ECMWF with its initial T+240 alongside, its pretty similar to GFS as far as I can see, the two major lows are in similar positions; the high is rather further east than GFS. Its backed away over time from its T+240 positions which had the high further west.

The net result is that as you run the set through the high is, apart from two early frames, over and east of the UK, like GFS thus the main cold plunge goes east of the UK.

How about NOAA

This taken from the NOAA assessment this morning

TELECONNECTIONS RELATIVE TO DAY 5 FCST

POSITIVE ANOMALIES CENTERED NEAR OR JUST E OF GREAT BRITAIN

suggests they see things rather similar at about the same time.

There is no new 500mb anomaly chart out yet but the previous one also suggested the main centre over/east of the UK.

new one just in at

2050

and continues to show the main +ve anomoliy over/east of the UK but a touch further north than the last one.

A closer look also shows that the 500mb flow is now a good deal more buckled than earlier predictions.

Looking at the ensembles over the area I've used before and trying to be objective not selective on what they appear to show in pressure values at T+144.

The Derbyshire one shows a good agreement out to T+144 even 48-72 hours later its not too bad in spread.

So to look at the map

so how far are each of these rough diagrams of the possible pressure pattern from the GFS Operational?

T+144 looks pretty similar, so how about T+192(the output today not the original?

It is not violently different, but has the high further north and west.

T+144=T+192=

as a conclusion I would say that the coldest air will go to the east of the UK and there has really been nothing to suggest otherwise over the past few days. The upper air pattern remains such that with happenings over N America, IF they go as predicted then the upper pattern will keep the deep cold air mostly to the east of the country.

Notice also between T+144 and 192 how the 500mb flow changes.

I'll keep updating this thread every day if I get the time but not always in as much detail as tonight.

Edited February 5, 2008 by johnholmes

[johnholmes]

Update Wednesday evening 6 February

We are now in what is often looked upon as the reliable time frame so what is GFS showing this evening with the comparison with its T+216 initial chart

T+120

Certainly HP is going to be the dominant feature for most by this date, after what looks increasingly like a very pleasant spring like week end for much of the country. That is apart from any fog patches on Sunday morning lingering around.

How does this compare with the initial chart?

One has to say not that much in the position of the high. T+240 suggested over/just west of the UK, T+120 has it over the Polish/German border, at least 15-20 degrees further east. The chart yesterday was pretty similar, so GFS seems to have decided where its going to start life, so to speak.

What about ECMWF?

Tonight it has it not that far from the GFS position.

and at T+240 it had

Even further west than GFS with the cold plunge looking to at least clip some parts of the UK.

We can now start to compare these two models with the Met O output and their human intervention showing the 12z Monday Fax chart

Supporting the idea of the surface high being even further east.

This does now seem the most likely situation with little sign of any cold plunge on their Fax chart other than over and east of Greece.

NOAA outputs continue to suggest HP is most probably going to be over or east of the UK/Scandinavia region. This in spite of the 200mb circumpolar chart showing signs of flow buckling developing over the western Atlantic. The position of the main trough (one of the Rossby waves) is crucial as to where the ridge sets up and it may still be that it settles down rather further west than is currently being indicated.

However the purpose of this LRF was to try and see what if anything might give pointers to where the surface high would begin to settle around 11-13 February. Currently almost all the evidence from charts from any source I’ve looked at suggests the most likely place is east of the UK. This means that the T+216 guidance both from GFS and ECMWF, whilst showing that a surface high would develop did not get its longitude very accurately. What I don’t know is why?

I’ll update each evening into the weekend just to see how much the actual positions change but the overall impression from both models, especially ECMWF 10 days out looks like being somewhat wide of the mark in the surface high positions.

The best guide in this case appears to have been the NOAA 500mb anomaly chart for

6-10 days ahead. This gave the expected 500mb set up pretty well with the surface high expected to be somewhat east of the UK, against both ECMWF and GFS at the time.

[bluearmy]

JH, you will no doubt have noted that the two 500mb charts that had the block a bit too far west were the weekend automated ones which refelcted the GEFS output. the forecaster (modified with other model input) issued charts have been more accurate with the block averaging just to our east over the 4 day period.

[johnholmes]

yes quite noticeable and certainly something to be aware of. Initially it did fool me until I had a closer look at the dates of issue.

Not dissimilar to the Fax charts from UK Met and their own model charts which are not infrequently at variance.

I'm interested in how the 200mb circumpolar charts show the upper flow getting more wave like but I still feel the major trough/ridge system is going to be in the wrong place for any possibility of the surface high being further west.

Its been an interesting few days and I've learnt from it for sure.

ps

tks also for the initial 'heads up' some time ago about it.

Edited February 6, 2008 by johnholmes

[BrickFielder]

I think the models may have been confused by two seperate high pressure features. Looking at the world jetstream 24 hours out I see a low pressure system down around the canary islands which is taking some energy south. I see the jet ridging north to give our high pressure over the weekend, but I also notice the jet meandering north over eastern canada.

Its what happens to the high pressure over canada which intrigues me.Here it is at 24 hours out.

Early Saturday and it has been pushed out over the Atlantic.

Then it gets pushed north by an undercutting low.

By Sunday looks like it is really weakening, but is that another canadian high being pushed out to the atlantic to join it.

It seems to still be there on Tuesday with a low to the south heading towards spain propping it up.

Late on Tuesday and it has been shifted to the north of the UK.

The low system coming in behind powered up by warm and cold air meeting over the US means the high is very transient and unlikely to be very important to our weather.

The question must be is this a repeating pattern with low pressure undercutting towards the canary islands ,high pressure coming off northern canada and will a more blocked ridge take hold as a result Later.

Looking at the 100hPa layer I suspect it might just be a one off at the moment.

Edited February 7, 2008 by BrickFielder

[johnholmes]

for my update this evening I think this comment from NOAA duty forecasters explains it all.

THE 12Z/06 ECMWF AND GFS ANOMALY CHARTS FOR LATE NEXT WEEK

CONTINUE TO SUPPORT THE PATTERN OF A STRONG POSITIVE ANOMALY OVER

NORTHWEST EUROPE AND A NEGATIVE ANOMALY CENTRD SOUTH OF THE ERN

ALEUTIANS TELECONNECTING TO RIDGING WEST OF HUDSON BAY AND MEAN

TROUGHING NEAR THE DAVIS STRAIT INTO THE PLAINS. THE 00Z ECMWF

AND GFS SOLNS GENERALLY FIT THIS PATTERN.

In other words the surface high will settle over Europe with any cold air way east of here thus the initial guidance some 9-10 days ago was somewhat out. That is both GFS and ECMWF, even more so, did show the possibility, no more than that, of deep cold air skirting at least the east of the country.The long wave pattern continues to support the above NOAA comment.

Edited February 7, 2008 by johnholmes

[johnholmes]

just a very quick update this evening.

This to cover the original thread for Monday 11 February and also for later the same week as interest seems to have picked up in the model thread as another surface high tries to show signs of developing a link up to the north west of the country.

1) Monday 11th looks, as it has done for several days now with the high settling in over Europe with any cold air way east.

2) The next high looks like doing something very similar with the eventual position being not that different from the first one, although it may well have an 'arm' north west for a brief period. Its the wrong orientation though to bring any deep cold air over the UK.

Neither will give deep cold air over the country. Throughout the next days, probably reliably out to next weekend at low level air cooling down as the flow ends up off a cooling continent. Not that even there it will be 'cold' cold. Fog a problem for some parts of the east and central areas at times. Otherwise by day, away from the far west and north west reasonably pleasant days with fairly light winds for most and a fair amount of sunshine.

Certainly not winter in the sense of snow, harsh frosts and any possible ice days(whatever they were from old!).

On a slightly more technical note; the upper level flow suggests why the high(s) are unlikely to make any progress further north west than any of the models show. The wave length is just wrong. How much this has to do with events above the Tropopause I leave to those with a better understanding than I have. Read the sensible posts from GP etc in the model thread about that.

Nor is there anything in the NOAA forecast comments to suggest anything other than my take on events out into days 6-15.

The only very slight hint of anything the models seem not to have picked up is on the play through of the 200mb circumpolar charts. This shows a developing ridge for the western Atlantic/UK area but with a cut of low(at 200mb) way way south of Greenland. This has, in the past, seemed to be linked to a tendency for the upper flow to retrogress(move west rather than east). However its very tenuous and as I posted in the model thread early this evening I doubt if it even rates 20% as a chance at the moment. But I'll monitor it.

Edited February 8, 2008 by johnholmes