45 replies to this topic

[Tellow]

Ooh the 06z GFS keeps a rather sustained cold outlook, with northerlies (noreasterly) producing snow more widespread and including western areas in FI.

It is the 06z though, again the run with the lowest verification stats, but if 12z follows it will certainly be looking good.

Edited by Tellow, 04 February 2012 - 12:42 .

[phil n.warks.]

The 12Z models have come up with a full house for cold and snow fans by the seems of it.
Here are some images from the different runs at T144hrs. which show the onset of another Easterly as heights are shown to rise to the NE again.





Further on we see the trend for vortex splitting again with the likelhood of Greenland Blocking in week 2.
See the mean Ht.Chart here for days 8-10 from the 12z GFS/ECM runs.



If we also view the tropical MJO forecasts and the matching composite for it`s high amplitude and it`s placement in Phase 8 of it`s cycle then again we see a familar trend of Northern Blocking suggestive of a North or North easterly flow in the medium term.



If we consider the 12z outputs and those others i have shown along with Chiono`s.data in the Strato Thread there is good agreement that an Easterly and then a Northerly are the likely patterns to expect in the next 10-15 days.

Pretty good stuff for those looking for more cold and snow before Winters end. Indeed these outputs signal the strong chance of a very cold February.

Edited by phil n.warks., 04 February 2012 - 21:58 .

[weathermaster]

Thoughts on the weather models today,

GFS

One interesting thing about the models recently is we see low pressure tracking across the Atlantic around Tuesday and Wednesday they all come up with different ideas on this. The GFS shows a low pressure system move near the far West of the UK which then drops in pressure and heads up to Iceland. While this happens the UK is under high pressure with settled weather. An increasing trend is appearing after this on all models now. With high pressure building up in the Atlantic but with some low pressure systems in there as well. The GFS shows the Russian high move over to Greenland by next weekend and from then on it gives us a good solid Northerly not just a short cold spell. It shows this Northerly lasting well into the mid month. Very good charts tonight from the GFS and a trend that's still going strong.

JMA

Not the best charts tonight but still okay. It tries to build high pressure up in the Atlantic and over our North but it sends a large low pressure system over Greenland and Iceland stopping any blocking happening it would leave the UK under high pressure though.

ECM

Showing very nice charts as well tonight and agrees with the GFS although it makes the Northerly happen a bit quicker. We see the Atlantic weather coming pretty much to a grinding stop by Thursday. After this high pressure from the West and East join but we have a low pressure system in the middle of this all which actually helps us get the Northerly. The ECM solution tonight is a very complicated one and when you throw in a low pressure system that makes things extremely hard to handle because there are endless ways things could end up. But at least its still showing a cold outlook with a Northerly in place, a good trend from it and the GFS in the past few days.

GEM

Had us excited early on this week showing a possible shortwave for next Wednesday however most models dropped this idea last night and today the GEM seems to be the last one to drop it. Anyway its also giving us a nice outlook possibly not the best but still good. It has high pressure to our North East and in the Atlantic but a low pressure system over Greenland. That's what it shows up to 144 hours beyond that is unknown what it would show, I would think the low would go under the blocking helping us get a stronger blocking to occur in the North.

NOGAPS

Also agrees on this trend and actually the 144 hour chart looks similar to the UKMO. It has high pressure to our North East and high pressure out in the Atlantic. It then eventually leads to another Easterly later on.

UKMO

Its very good to see this model agree with a cold set up. Although its hardly surprising the ECM and GFS have been keen all week on a colder outlook and even the ensemble run was showing good signs. The UKMO shows high pressure to our East and West with a shortwave for next Friday to the West of the UK.

Overall not to much attention it seems on the weather models today with all the snow. So after this current cold spell its time to look for the next and the models are already showing us nice charts although they all differ in exact detail the trend is there for some sort of blocking to happen some time soon. Interesting model watching continues.

Edited by weathermaster, 04 February 2012 - 21:09 .

[damianslaw]

All models agree on blocking ruling the roost for the foreseeable future with the atlantic making only splashes into western parts before being forced to retreat mid-week thanks to a resurgence of those heights to our east nosing into the country. Indeed the outlook looks a carbon copy of the week just gone -slightly less cold uppers, but a predominantly dry outlook away from the west, frosty nights and cold days- keeping the CET well below average.

Longer term - the models picking up on upstream northern hemispheric changes - scandi trough being shown by both ECM and GFS, ECM a bit more progressive in its timing, heights quickly transferring to Greenland. So an easterly followed by a northerly/northeasterly and an unstable one meaning excellent chance of heavy widespread snowfalls thanks to trough/shortwave action and energy going into the southern arm of the jet.

I think there are going to many snow lovers happy in the next month.

[TonyH]

My take on the coming week from a regional perspective:

Weather guide Monday 6th to Sunday 12th February (west Wales and central MIdlands)

Headline: Becoming cold and mostly dry again


The battleground event happened on cue yesterday with 3- 5 inches of snow falling across Coventry and Warwickshire, while the milder air won out over west Wales. The continent has been bitterly cold of late, in Paris the temperature falling to -9c, and heavy snow in Rome for example. Llanwnnen got down to -10c Friday morning, this nowhere near as cold as the -17c recorded on Christmas Day 2010!

During the early part of this week we are in a 'No Man's Land' neither in cold nor mild air, being within a slack area between high and low pressures.
Messy weather too, some sun, some cloud, bits of rain or drizzle about, but dry in places too! Not cold enough for snow, but cold enough to freeze overnight with potential ice problems for morning commuters. Maxima on Monday and Tuesday between 4 and 8c, mildest over Pembrokeshire.
Rather debatable Wednesday onwards with the models showing some slightly differing trends, but with greater consequences in weather terms.

Strongest indications are for high pressure to reform over Scandinavia again with this ridging cold air back over England and Wales from Wednesday. During Wednesday itself though, a niggle, as Atlantic fronts may progress close enough to west Wales to bring some sleet or snow here, however this is a low probability at this stage, but don't be too surprised to see some wintriness this day perhaps. Cold easterly winds look likely again to end this week, with crisp sunny periods by day, but hard frosts overnight, and also freezing fog could linger well into the day in places. Maxima between 1 and 3c generally, although staying below zero locally, should freezing fog persist well into the afternoon. With the high pressure in control, snow is unlikely, apart from the odd rogue light flurry into the Midland perhaps.

Next weekend, as always at a distance, and greater doubts cast as to what may happen. It looks like the high pressure will be over or close to the UK by then, so it would still be cold and frosty, although should the high sink to our south-west, as GFS suggests, turning milder. However, I would bet on the cold holding on well into next weekend.

For supportive model charts see the Welsh thread:

http://forum.netweat...64#entry2255764

[phil n.warks.]

Some understandable sense of frustration from cold seekers wrt the Operational outputs today which still continue to shy away from true Arctic blocking,more particularly around Greenland where the vortex continues to show on later frames.

I thought i would revisit some medium range data and so called background signals to see where we might be going.

First of all a view of the 12z Mean Outputs-rather than the Ops-for days 8-10.taken from ECM and GFS.



Now the MJO forecast showing entering phase 8 in a few days and it`s composite NH pattern.


See the similarity with the mean chart above-not quite there but time for minor changes to that 500hPa pattern as we are looking at week 2 for this.

Now a look at tonights 500hPa mean hts anomol forecast for days 6-10(automated at weekend)which has been remarkably steady for days.


Again compare that with the previous images-all the same approximate pattern-Heights to the North,Lower to the South.
It doesn`t scream zonal in any way as we go further into the 10 day period.

Finally from the Strato.data and on the left mean zonal winds show a reversal at high latitudes indicating a complete disruption of the vortex and the other 2 images are forecasted pressure patterns at the lowest level ie100hPa of the Stratosphere taken from both the ECM and NCEP(GFS) sites.



We can see the vortex split with troughing indicated over Scandinavia and Canada and the gap for heights over the Greenland area.
These are all indications for a cold blocking pattern in high latitudes around the approximate Greenland /Iceland or mid Atlantic (north) area in 10-14 days.

[johnholmes]

phil n.warks., on 05 February 2012 - 21:55 , said:

totally agree with that post phil-the 500mb pattern has been pretty solid from about 17-29 January if my memory is correct. I normally have all the charts saved but was on holiday and just copied them to paper, once I got back and saw that the first 5 days back simply carried on that pattern I threw them away!
Prior to that date they had been not too much in agreement from day to day or with one another. Even though the Stratosphere ideas by then were already suggesting what we have now.see below for my 'snapshot' view using the 30mb temperature

Even before I went away though there were signs of a suggested building of heights at 500mb, although at that stage well west, see below


so the 'signals' have and continue to be for blocking not mobility. I simply do not understand, other than for some the enjoyment of deep analysis of every model run, why there is this obsession with 4x2 and 2x2 outputs each day. Fun to look at and maybe compare and discuss but not terribly scientific I feel at the risk of upsetting some folk.

[johnholmes]

24 hours and things can look a bit different!
Taking a closer look at 'things' this morning.
The 30mb temperature is now diving down below average. The AO is pedicted to rise well above the zero line, while the NAO has not really changed from 4 or 5 days ago. The MJO has suddenly moved further from the origin than it has been for many weeks, currently in 6/7 so still suggesting blocking. Its forecast to return to near the origin and be close to 8/1, so not so blocked is my take on that.
The 500mb anomaly charts are not that close to one another in the past 24 hours. ECMWF and NOAA seem the closest with GFS showing some difference. Indeed this morning ECMWF and GFS deal with things rather differently. GFS maintains its block shape in the UK area, ECMWF shows a flatter type and they disagree on the two main troughs, shapes and positions and depths; the European and that over NE America.
So having been convinced up to last evening that everything continued to suggest major blocking well into February I am now not so sure. Certainly a cold week to come and into the weekend. beyond that then things may be starting to change to a more mobile type of upper pattern but that is a long way off. We have to watch the links I've mentioned over the next 5 days or so.

[WhiteFox]

Thanks John. I like your updates because they are almost the UK equivalent of the NOAA forecasts regularly posted by Nick (albeit written in plain English). Nice to have an idea of the thoughts of the Met Office forecasters as they prepare their output!

[johnholmes]

some may like to read through this-its an attempt to show what the models are showing without any personal bias at T+144, 240 and other indicators further out.
Will it stay cold or will it get less cold and more unsettled?

 Models as of 7 feb 12.pdf   769.34K   229 downloads

[phil n.warks.]

johnholmes, on 07 February 2012 - 15:33 , said:

some may like to read through this-its an attempt to show what the models are showing without any personal bias at T+144, 240 and other indicators further out.
Will it stay cold or will it get less cold and more unsettled?

Models as of 7 feb 12.pdf

Thanks John.I think you picked a tricky time to do this one.Some differences recently with the 500hPa patterns,Certainly as you suggest not clear cut on cold or milder towards day 10.

[MisfitDog3]

"Certainly as you suggest not clear cut on cold or milder towards day 10." ...to be honest I don't think there is any clear cut from the weekend. I don't buy into the ECMRWF evolution from 96 to 120 hrs because the position of the High to the west just looks wrong..particularly at this time of year. Mind you I'm hardly enamoured by the middle term GFS projection either! We will see some major changes again on several models as we go towards Friday. At the moment it looks like a change signal is in the early evolutionary stage which is throwing out some odd pressure placements on a few of the models. That doesn't necessairily indicate mild weather either...

[MisfitDog3]

And what on earth is happening with FAX plus 84 hours...some very off jumps and an evolutionary speed of a fleeing zebra....

[Isolated Frost]

MJO and GWO still seem to favour HLB n/ of UK. Strat still warm and some reversal in zonal winds and all the characteristics for local wave breaking events to occur. Alas, where is the NWP response to this? Coming I say, patience still.

Up to +48 it seems that high pressure will be over the UK in some way or another, allowing some potentially harsh frosts and sunshine for most. The high pressure cell in the mid-atlantic attempts to transfer it's blocking heights to Greenland via a ridge, but ultimately fails, and thus bringing a close to any persistant arctic cold at +72. At UKMO, the +96 shows a better chance as the blocking heights have moved into S Greenland, and WAA is very much apparent, however, the HP cell is too far south-west, just west of the UK allowing milder air from the mid-atlantic to interrupt the flow, giving mild nw/n'lies to western parts while the eastern parts miss much of the cold action that occurs in Denmark/Benelux.
UKMO +120 gives up on the ridge, and the trough sinks, giving the UK temporary NE/N'lies, allowing colder air to seep in to the east.
By +144, the PV is back in action, the Atlantic high moves into the azores, and despite the trough sinking, it appears we are too far west as the high gives us mild nw'lies.

Preferably, we want good WAA up w greenland, a stronger ridge, firstly the heights more strong towards Greenland/Iceland and the HP cell further north-west. Next, we want the trough to first move W towards the benelux/n sea so much of the UK enjoys a potent northerly, and then, sink preferably, allowing height rises to the north, shunting away any vortex attempts, and creating a spell of NE/E winds.

Entirely possible when looking at the teleconnections. Patience.

[Mr_Data]

Isolated Frost, on 10 February 2012 - 07:44 , said:

. Patience.

Don't mention that word to cold and snow lovers in the west, they might say its about time it bloody delivered!

[Seven of Nine]

Mr_Data, on 10 February 2012 - 07:56 , said:

Don't mention that word to cold and snow lovers in the west, they might say its about time it bloody delivered!

Yes but come May all this patience will pay dividends.

[TonyH]

My regionally selective take on the next 7 days

Weather guide Sunday 12th to Saturday 18th February (west Wales and central Midlands specific)

Headline: Milder with plenty of dry weather

The cold spell is on it's way out now, having brought heavy snow to the East this week, and with last night temperatures as low as -18c over the snow fields of Eastern England. Although winds are coming from a generally North-westerly direction this coming week, the air is greatly modified and it will not be cold.

The cold hangs on tonight with another hard frost for the Midlands. Sunday sees high pressure moving west across the UK, but with weak frontal systems within this. It's a similar picture for Monday too, with the high ending up to the west of Ireland. Bands of cloud will be tracking south across England and Wales on these two days, and perhaps bringing a little light rain or drizzle in places, with some sunny intervals too, especially later on Monday. There may be a touch of frost by night if skies are clear enough. Feeling chilly in the NW breeze, but temperatures reaching close to the February average of 6 to 8c, so much milder than the past week! Tuesday should be a dry, bright day but with a chilly north wind.

During Wednesday and Thursday the high pressure is positioned well south- west of Ireland, and the feed of air, although still from the NW, has tracked all around the high from the mild Azores region of the Atlantic, so that in spite of the wind direction, it will be a fairly mild couple of days. Due to the lengthy sea track of the air, it will be a rather cloudy spell this, but with a few sunny intervals, and frost is unlikely mid week, with afternoons reaching 8 to 10c. Dry for most, bar a spot of drizzle at times for west Wales.

By the end of the week, it looks like a low pressure passing close to Iceland and then into Scandinavia will influence us, the high edging further south-west into the Atlantic and away from the UK. A more unsettled theme for Friday and the weekend then, with bands of rain and some showers affecting the UK, most of the showers over west Wales. Although turning colder, temperatures are not far from average, reaching 5 to 8c, so any sleet or snow will be confined to the higher ground of Wales. Slight frosts will occur by night given clearances.

For supportive charts see here:
http://forum.netweat...5/page__st__460

[Yellowbelly]

I'm just an observer of the model threads, but I do like the objective style of TonyH's post. I hope this thread will develop like that, without the subjective qualifications such as 'poor', 'upgrade', 'downgrade' etc. applied to models according to the posters particular bias.

[johnholmes]

That is the general idea for when it gets totally frantic in the model thread some of us will post in here with, we hope, a none judgemental view on the models and any marked differences they show. Along with our view on how we feel the weather may turn out.

[TonyH]

Ah somewhere out of the limelight
My regionally selective take on the week ahead:


Headline: Becoming very mild. Changeable with some rain at times. Exceptionally mild on Thursday and Friday, especially the Midlands

Unless the next few months are very wet, then water shortages beckon for the Midlands this Summer, as the Winter has failed to produce adequate rainfall after the very dry 2011. The rest of February will only see small amounts of rain for Warwickshire once more.


High pressure over us tonight gives a frosty start to Monday, although this may be lifting by dawn over west Wales as a milder breeze spreads in. A dry, bright day for the MIdlands, but clouding over for west Wales, and drizzle possible late in the evening.

From Tuesday, a deep fetch of air originating from the tropical Atlantic, feeds in increasingly mild winds from the south-west or west.
Mostly cloudy and mild on Tuesday and Wednesday with rain and drizzle at times, most for west Wales; drier spells for Midlands. although even here there will be a spell of light rain late on Wednesday. Fresh to strong south-west winds.
Thursday and Friday will be mostly dry, bar the odd spot of drizzle for west Wales (typical!). Sunny spells are likely for the central Midlands meaning exceptionally mild days, reaching as high as 15 or even 16c. Even for cloudier west Wales, 13 or 14c is attainable on Thursday. These figures are not often reached in February and are 6 to 8c above the average. Still a fair bit below the record of 19c reached in the Midlands in February 1998 though.

A mainly dry looking set up for next weekend, although weak troughs may threaten a little rain in places. Should skies clear by night then slight frosts would occur.

For supportive charts please visit Wales:
http://forum.netweat...23#entry2273923