Model Output Discussion - Heading Away From Easter

[Summer Sun]

The big positive again this morning is the next 2 weeks is looking very dry so other than the odd light snow showers here and there in the north and east we are slowly moving away from any significant snowfall now

Edited March 29, 2013 by Gavin.

[picog]

The big positive again this morning is the next 2 weeks is looking very dry so other than the odd light snow showers here and there we are slowly moving away from any significant snowfall now

Yes, the dry outlook is really important. The snow melt has made all the fields soaking wet again, pools of water everywhere. Even in the garden, standing on grass is squelchy, and water comes around your foot. Hopefully, the ensembles are right and it really is a dry outlook for a couple of weeks at least.

[snowking]

I am not about to say the 500mb anomaly charts show a pattern change, however!

The output this morning from the ECMWF-GFS outputs is different from their issue yesterday. Not GFS it continues with what seemed to be the pattern developing over the past 4-5 days. That is a gradual build of heights just north of the UK and the main Atlantic flow going towards Iberia and the Med. It does this again this morning much as the NOAA 6-10 and 8-14 did last evening. ECMWF has a different idea, from itself over the past few days and the other two. An instantaneous dismissal of the upper ridge or a shift of many hundreds of miles west with a fairly deep trough in its place allowing a marked northerly upper flow into the UK.

You all know my views on consistency with one another and themselves over several days for belief in any pattern showing, especially any marked changes. Just what ECMWF is up to I have no idea but it certainly is a change from its outputs over the past 5-7 days.

Time will tell, ask me again in 3 days or so?

anyway below is the output from ECMWF and GFS this morning.

http://www.meteo.psu...0z/hgtcomp.html

copied into the other thread as well

It will be an interesting one to monitor John as the EC det. has been pretty good in recent months in picking up an overall trend

However, for the time being, it remains an outlier against the EPS suite:

SK

[Summer Sun]

Latest ECM monthly outlook continues to show temperature staying below normal by mid month the average gets to around 10c around 4c below average

[johnholmes]

A positive from a flood threat and snow melt is that snow melt is going to be slow based on any of the models. This should ensure that river levels in the prone areas should stay below any danger level as the snow at height slowly melts over the coming couple of weeks.

[-uksnow-]

ECM mean @240 is one for the archives surely, whole country apart from the far south western tip of the UK in -5 uppers as the mean

Incredible

[lorenzo]

ECM is insane this morning, in the immediate a final squeeze west of the coldest air from the Scandi pool we have been draining out.

Then it all goes off on one.

120 hrs and the Scandi High begins its travels, stretch North of the UK and by 144 the block extending to Greenland.

168 and the Greenland High is in place, beyond that a strong Arctic High in position hints of cross polar flow. At 192 it is almost a massive variation of a double Omega block, vortex either side to the Greenland and Arctic Highs, the Northerly comes firing in.

At 144 the continent is heating and our cold trough even more evident, perhaps FI around here as this appears to be where things are in balance prior to a tip to colder solutions. By the end of the run you can see the additional cooling added from the Northerly.

These are also Ensemble means ! Not an operational off on one..

Mean Heights out in FI..

Way out at the end of the run the NH view highlights again in mean the continued blocking.

Looking at the TC's quite a period now of prolonged negative phase of both NAO and AO.

If Winter is finally losing it's icy grip around the second 10 days of April then it is going out after serving up some amazing model runs.

Edited March 29, 2013 by lorenzo

[Frosty.]

There is still no end in sight to the current remarkably prolonged cold spell, the next few days look more anticyclonic (benign) with rather lighter winds so it will at least feel pleasant in the very strong sunshine but with widespread frosts returning soon after sunset. The high to the north of the uk looks like strengthening even more from early next week so we are well and truly stuck in a major blocked pattern for at least the next 10 days and probably nearer 15 to 20 days. The Gfs 06z shows a realistic view of next week with easterly winds returning to southern britain with wintry showers, rather more benign to the north with lighter winds nearest the core of the high, further on looks very anticyclonic with nice sunny days but frosty nights and temps remaining below average. At least the remaining snowcover will continue to slowly thaw by day as temps reach 5-7c but freezing over at night, so although british summertime starts this weekend, nobody told the weather and the long extension to winter will continue with widespread sometimes sharp frosts and wintry showers at times, mostly in the south and east.

Edited March 29, 2013 by Frosty039

[Summer Sun]

A rise from the ensembles now to the end of the run

[Purga]

A rise from the ensembles now to the end of the run

Still a couple of beauties like P1 keep the faith right to the end.

lovely jubbly

Rain for the Irish though.

Edited March 29, 2013 by Purga

[Mucka]

I think there are two competing longwave signals across the output at the moment so quite likely this evenings ECM will be quite different again.

The models are toying with a mid latitude block but are unsure whether to to send energy under it and retrogress it while setting up a Scandi trough or slowly have the energy push over the top and give us a pattern change.

I have mentioned both as possibilities, originally suggesting a way out may be for the block to be slowly modelled further SE (which it has) and for the Atlantic to slowly get in and sink it into Europe gradually bringing milder more unsettled conditions from the NW (which has been sporadically modelled here and there but nothing convincing) and then if that failed I mentioned the possibility of an icy blast from the NE as we head into the second week of April as the high moved NW and I believe the signal for this has strengthened a little.

The majority of the output still shows high pressure remaining close to the UK however with a slack Easterly flow so temps a little below average past the mid term and settled but I think we will slowly see these solutions go for something a little more dramatic one way or the other.

Purely subjective and unscientific but I would say a pattern change to milder toward the end of the first week of April has about a 25% probability based on output from the last couple of days (best chance I have seen in a long while) with perhaps the chance of a very cold set up developing again a touch higher and I think the majority of the no man's land output that is undecided with the high will slowly move one way or the other.

If that is correct then we may see a split in the ensembles (rather than just scatter) developing or alternatively flip milder or get colder from around the 6th April.

All just fun conjecture on my part at the moment.

Edited March 29, 2013 by Mucka

[rory o gorman]

The gfs 06z are starting to show a return to more typical spring weather with a good southerly influence developing.

[Scorcher]

Purely subjective and unscientific but I would say a pattern change to milder toward the end of the first week of April has about a 25% probability based on output from the last couple of days (best chance I have seen in a long while) with perhaps the chance of a very cold set up developing again a touch higher and I think the majority of the no man's land output that is undecided with the high will slowly move one way or the other.

I'm just wondering what you consider 'very cold', as we've got uppers close to -10C over much of the country today but temperatures have reached 5C for many already, really can't see -10 uppers being repeated after this weekend. Sub 5C maxima are starting to become very hard to achieve even with cold uppers.

[Tim Bland]

The gfs 06z are starting to show a return to more typical spring weather with a good southerly influence developing.

It's the 06z an it's almost a mild outlier. Going to be a long road to anything springlike IMO

[J10]

Latest SKi Blog out for Easter weekend and week ahead.

GFS synoptic charts included as normal, and no return to mild weather according to this, although perhaps a slow rise in temps

[Summer Sun]

The end appears to be in sight again with today's met office updates

UK Outlook for Wednesday 3 Apr 2013 to Friday 12 Apr 2013:

Towards the end of this period, there are signs that this prolonged cold period may start to wane, as winds become more westerly in nature.

UK Outlook for Saturday 13 Apr 2013 to Saturday 27 Apr 2013:

There remain signs of a transition from the current colder than average conditions to more typical conditions for the time of year taking place during mid-April. This would leave the rest of the month with nearer average temperatures, albeit still with a risk of overnight frost. Meanwhile, in the absence of any strong signals for trends in precipitation later this month, the most probable scenario is for rainfall to be nearer average. Given that the first half of April is expected to be drier than average, this does imply that at least some parts of the UK are likely to be more unsettled during the second half of April.

Its going to be interesting to see if the models start to pick up on this trend during the next week ECM picked up on a trend to something less cold last night but dropped it this morning

If ECM is to be right then it will be hats off to it by picking up this trend so far out

Edited March 29, 2013 by Gavin.

[snowking]

The end appears to be in sight again with today's met office updates

UK Outlook for Wednesday 3 Apr 2013 to Friday 12 Apr 2013:

Towards the end of this period, there are signs that this prolonged cold period may start to wane, as winds become more westerly in nature.

UK Outlook for Saturday 13 Apr 2013 to Saturday 27 Apr 2013:

There remain signs of a transition from the current colder than average conditions to more typical conditions for the time of year taking place during mid-April. This would leave the rest of the month with nearer average temperatures, albeit still with a risk of overnight frost. Meanwhile, in the absence of any strong signals for trends in precipitation later this month, the most probable scenario is for rainfall to be nearer average. Given that the first half of April is expected to be drier than average, this does imply that at least some parts of the UK are likely to be more unsettled during the second half of April.

Its going to be interesting to see if the models start to pick up on this trend during the next week ECM picked up on a trend to something less cold last night but dropped it this morning

If ECM is to be right then it will be hats off to it by picking up this trend so far out

Im going to guess its largely based (as usual) on the ECM 32. Certainly promoting something far milder (though still below average) for Heathrow:

It has shown pretty good consistency in this regard over the past 3 issues (below, Red is most recent, Black is previous, and Blue is last Thursday's issue)

So initially last Thursday's issue was too progressive with its idea of a warm up in the shorter term, but there is now good consistency from the ECM in the longer term in terms of the temperature trend.

A split in the last few runs of the CFS in this regard, a generally less anomalously cold picture than currently:

However, still variation within the h500 forecast:

vs

So still some uncertainty in the overall weeks 3/4 pattern, but the natural warming beginning to come through one would think over the next few weeks

SK

[Jax]

So still some uncertainty in the overall weeks 3/4 pattern, but the natural warming beginning to come through one would think over the next few weeks

SK

Hi Kris

I think we have to accept that natural warming must begin to show it's hand this coming month, it may be slight, but it has to be there I would expect.

[stodge]

Afternoon all

A rare opportunity for me to have a look at the current synoptic output:

http://modeles.meteociel.fr/modeles/gfs/runs/2013032906/gfs-0-144.png?6

GFS 06Z Operational - cold and dry pretty much sums it up. Hopefully some sunshine but the flip side of that would be some sharp and potentially damaging frosts.

http://www.meteociel.fr/modeles/ecmwf/runs/2013032900/ECM1-144.GIF

If anything, colder on first sight and more unstable though probably mainly dry. More of a NE'ly rather than E'ly component so supect this would be cloudier.

http://www.meteociel.fr/ukmo/runs/2013032900/UW144-21.GIF?29-06

Pretty much a halfway house though the positioning of the HP is significant in that while both GFS and ECM show the HP centre moving away from Greenland to the north or NE of the UK, UKMO keeps it much closer to Greenland

http://modeles.meteociel.fr/modeles/navgem/runs/2013032906/navgem-0-144.png?29-11

NAVGEM at 06Z . Elements of all the above but a large block of HP to the North of the UK and a E or ESE'ly flow, noticeably strong across the south.

http://modeles.meteociel.fr/modeles/bom/runs/2013032900/bom-0-144.png?00

BOM at 00Z sends the HP toward Scandinavia so the flow over the UK is more ESE'ly. Dry and cold.

http://modeles.meteociel.fr/modeles/cptec/runs/2013032900/cptec-0-144.png?00

CPTEC 00Z output. A more defined NE'ly with the HP kept over Greenland.

So by T+144 we have two main options on the table - one keeps the centre of HP over Greenland with a strong ridge to the N of the British Isles. This keeps the UK in a more E or NE flow. The second option sees the centre of the HP transferring either to the N of the British Isles or into Scandinavia in which case the wind flow becomes more E or ESE'ly. The former option says cloudy and cold, the latter sunnier and cold.

Perhaps not huge differences at this stage but I suspect they would have considerable consequences to the later evolution.

[lesta_snow]

I'm going away to Portugal in 2 weeks! Is our current cold spell having an effect on their weather? is it likely to be alot colder than normal there? I've been looking at the charts and can't really work it all out!

[Frosty.]

Well the latest met office update is a definate nod towards the Ecm 00z op run with winds trending towards Northerly by the end of next week so perhaps a final sting in the tail to the current persistent cold/very cold spell before the pattern becomes flatter and more seasonal but it's still only a signal for change and not set in stone, the models can make a mockery of our predictions sometimes so this amazing spell of cold weather is not finished with us yet, although it is loosening it's grip in the next few days (by day), it looks as though it will tighten it's icy feeling grip again during next week with freshening winds from the east or northeast making it feel bitterly cold once again, and after the drier interlude, it looks like wintry showers will become increasingly likely next week, especially towards midweek and beyond with snow showers in places, mostly in the north and east and on hills but not exclusively, frosts will again be widespread and sharp, even with the variable amounts of cloud expected, so, winter goes on for around the next 10-15 days but then there are hints of a change from around mid april onwards to more typical april weather.

[Mucka]

I'm just wondering what you consider 'very cold', as we've got uppers close to -10C over much of the country today but temperatures have reached 5C for many already, really can't see -10 uppers being repeated after this weekend. Sub 5C maxima are starting to become very hard to achieve even with cold uppers.

Indeed we have seen exceptionally cold air over us which should slowly moderate as we move through into the first week of April.

Thereafter the conflicting signals are apparent and whether energy will push under Greenland and eventually bring milder more unsettled weather or we see that energy forced NE up the West of Greenland and a strong Atlantic ridge with a Scandinavian trough forming. (or of course we may see a continuation of the pattern we see through the first week of April with high pressure close to or over the UK and less cold uppers (though still chilly in a predominantly East flow which is what the majority of the ensembles currently show -I think they will move away from this halfway house but we will see)

So, to answer your question - if we get the Atlantic/Greenland block then I expect we will see uppers of -8 or lower flood the UK once again from the NE somewhere close to or into the second of week of April. There are so many variables at play though at that range and we could get a similar pattern set up and the cold air plunge into Europe just to our East so admittedly it is quite speculative but that's part of the fun of trying to make sense of the longer range output and looking for pattern changes.

Edited March 29, 2013 by Mucka

[Mucka]

I'm going away to Portugal in 2 weeks! Is our current cold spell having an effect on their weather? is it likely to be alot colder than normal there? I've been looking at the charts and can't really work it all out!

My guess is your timing could be very good. There may be a significant warm up for the region by then whether we get a mid Atlantic block and the UK stays cold or high pressure sinks into Europe and we warm up too. You would be unlucky to see high pressure set up in such a way it was still taking a cold Easterly flow that far West IMO.

But hey, I'm just an enthusiast so best to check out what the pros are saying and either way the weather will do what ever the weather will do - just enjoy yourself!

[UV-RAY]

The gfs 06z are starting to show a return to more typical spring weather with a good southerly influence developing.

Ignore the 06z, well we are told that in winter so the same must apply the rest of the year.

[Snowman.]

Ignore the 06z, well we are told that in winter so the same must apply the rest of the year.

Just ignore the entire model simple!

Edited March 29, 2013 by SN0WM4N