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Model output discussion - the beast arrives


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2 hours ago, nick sussex said:

In terms of the cold pool, a few days back there were concerns it might miss the UK because of the quick evolution to the omega block.

There seems to be a myth surrounding Scandi highs that they can last for weeks, simply not the case.

To extend the cold you need a signal to retrogress the high , the issue isn’t that signal but it’s taken the high too far to the west .

Thats always a risk , a west based negative NAO .

But going forward it’s premature to assume that the weekend is game over, all the outputs still have the jet tracking to the south.

I wouldn’t entirely agree Nick. I remember Scandy highs lasting weeks during my years growing up with very high central pressures. For whatever reason this time the high didn’t set up shop to maintain the deep cold flow. It retrogressed quickly and allowed the low to approach from the south. It’s a pity as it looked set for a prolonged spell but it is what is is. On East coast of NI and bone dry. Nothing special for us I’m afraid.

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Evening Guys  Officially signing off for the winter from my window - still all but 5 inches on the ground - have a great year ! Current   favourite   See

First rule of GFS model watching. Never trust a dartboard low....... But especially in this type of set up.

See you next Saturday then, Steve?

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3 minutes ago, johnny1972 said:

I wouldn’t entirely agree Nick. I remember Scandy highs lasting weeks during my years growing up with very high central pressures. For whatever reason this time the high didn’t set up shop to maintain the deep cold flow. It retrogressed quickly and allowed the low to approach from the south. It’s a pity as it looked set for a prolonged spell but it is what is is. On East coast of NI and bone dry. Nothing special for us I’m afraid.

Normally long cold spells have a rinse and repeat scenario. Scandi high to Greenland high and back again.

The block in this instance goes west too quickly and it goes towards a more west based negative NAO.

However the AO and NAO are expected to remain negative for the next few weeks and the jet tracking to the south of the UK.

Of course the issue as you head into March is you need a deeper cold pool to produce but there’s no sign of spring weather  at the moment and northern areas may well remain in the cold and that could well extend south again.

 

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Does anyone have a similar (or better) animation than this that doesn't show Russia's output frozen in time, as it would be interesting to visualize the water vapour or lack of it coming from the east et al'

http://mp1.met.psu.edu/~fxg1/SAT_NHEM/animweur.html

What has happened so far - (from my interpretation) is that the warmth from the south has been flattened by the so called beast... i just wonder what strengths are left behind in the high to the east of us?

Edited by Pixel
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I'm backing the GEM :D:yahoo: got to love the underdog. Seriously tho it's showing the jet so far south. Wouldn't this allow all low pressure systems to to take a more southerly track? I know we have lost the highs to canada by t132 but by t204 it tries to build highs over scandi of 1020. With the surface cold holding the low pressure systems at bay, a south tracking jet not putting real pressure on the cold air and highs trying to build over scandi I think this could be the outcome. Very finely balanced tho. Or I might just be miss reading the entire situation :pardon:

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I thought it was interesting what Catacol said about the teleconnections that caused this cold spell were just too perfect/powerful and it's all got overcooked. Like the lead guitar turned up the amplifier to 11 - it was incredible for a while, but then the amp blew up. If the amp had been set at 10 or 9, it might have lasted longer!

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1 hour ago, Mac_SE said:

Two basic questions re the models for those with far more weather grey matter than me:

1. is the northerly track of Friday's low simply down to the lack of blocking, especially given the lack of jet energy?
2. given the stunning and comparable synoptics to '87 & '91, what is the big difference/reason between the sudden-ish shift of that block and those from the historic spells?

Have a broad understanding of reading the charts just not enough (yet)...

Thanks

 

There is a cruel irony in the answer - if you are into cold and snow. So often the Azores High is public enemy number one in preventing cold easterlies reaching the UK. But in 1991 it was an Azores High that was our friend and ridged northeast, after that major cold pool that gave snow in 1991 had passed , and prevented it from moving too far west.

Now this year, and lets just assume for the moment that the forecasts are correct, there is a major upper LOW and surface low over - yes the Azores, quite the opposite to 1991. Our cold pool, forecast to move west over the next few days, is expected to merge with this and the resultant vortex will be to the west of the UK. Winds at all levels are expected to blow around this and we will be receiving winds from the south ( we'l see whether they actually make it!). Coupled with this the block to the north is moving west rapidly, driven by the strong east winds at all levels, to its south.  The amazing thing this year is that a 1050 anticyclone over Norway tomorrow evening is forecast to completely disappear (by moving west) and lose 30mb within 48h. Scandi Highs used to be pretty resillient in late winter. The good old Azores ridge kept this going in 1991.

 

As a footnote I blame global warming. Given any excuse all that warm air to the south will blow north. I am sure the area north of the 546 thickness line is much reduced in our winters these days, making warming up a lot easier. The Arctic is certainly warming (see the post from ?1962-63 a few days ago) . Also a good website is 

http://nsidc.org/arcticseaicenews/

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14 minutes ago, nick sussex said:

Normally long cold spells have a rinse and repeat scenario. Scandi high to Greenland high and back again.

The block in this instance goes west too quickly and it goes towards a more west based negative NAO.

However the AO and NAO are expected to remain negative for the next few weeks and the jet tracking to the south of the UK.

Of course the issue as you head into March is you need a deeper cold pool to produce but there’s no sign of spring weather  at the moment and northern areas may well remain in the cold and that could well extend south again.

 

Well apparently it doesnt matter how far south of us the jet tracks. Random tiny lows will happily stop following the jet and randomly move North perpindicular to the airflow ahead of them.

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Just now, Snowy L said:

Well apparently it doesnt matter how far south of us the jet tracks. Random tiny lows will happily stop following the jet and randomly move North perpindicular to the airflow ahead of them.

I wouldn’t put the duvet away just yet.

Any less cold conditions going by the ECM ensembles and mean are going to struggle to get too far north .

The op is one of the warmest solutions , the mean flow for most of the UK remains more easterly throughout  , although the deep cold isn’t there no sign of spring and still a chance things could develop more favourably.

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6 minutes ago, lassie23 said:

I think anyone expecting this cold spell to extend will be out of luck this time tomorrow, it looks over.

You having a giraffe mate? solid 4 days of wintry weather yet, certainly not over by this time tomorrow!

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Just now, i luv snow said:

You having a giraffe mate? solid 4 days of wintry weather yet, certainly not over by this time tomorrow!

No i meant by tomorrow the models will be agreeing it's coming to an end come the weekend lol

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6 minutes ago, lassie23 said:

I think anyone expecting this cold spell to extend will be out of luck this time tomorrow, it looks over.

Quite possibly for the south, but far from certain for the north (see eps).

The 'warmup' in the south could only be temporary - time will tell as ever.

FWIW, the ECM Det only gives a maximum of 2C for London on Saturday. 

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I wonder if the precip coming from the south thurs /Friday actually moves that far north , and does the precip die out? Not being a party pooper but nothing is nailed this far out....:hi:the 06z and 12z gfs show a marked correction south on the latest....Watch this space...:rofl:

salt.png

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It's showing more to the South West which means cold wins out (for most of us) but no snow unless you are in the sweet spot which looks to be South Wales with the most North Easterly tip being Bristol. 

Edited by Lee Jones
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2 minutes ago, Paul said:

Can we keep it to model discussion in here please. Head over to the regional threads if you want to chat about local forecasts and the like. 

Certainly appology, Question was valid tho does the area of perc seem to split off one heading east and one heading west

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3 minutes ago, mrmonopoly said:

Certainly appology, Question was valid tho does the area of perc seem to split off one heading east and one heading west

You answered your own question already though, as you said there is some conflict with the model output with differing options being shown. If you're wanting more than that, then essentially you're beyond model discussion and back to talking about local forecasts and the like. 

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4 minutes ago, Lee Jones said:

Oh dear how are the BBC going to explain away that big blob of snow crossing the whole country for Friday which they were showing yesterday? I know the answer will be they don't have too, forecasts change etc but I thought at the time that ain't going to happen...like the news now it's over dramatised. 

Yeah its moved quiet a long way west! its now out to the irish sea. How will that effect the cold patterns moving forwards if that other area of low preassure follows the same path

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Well the pub run fails to get Fridays front north of the Midlands with snow showers continuing from Lincolnshire northwards even by Saturday with the -10C isotherm holding from the Washin in a line northwards.

Edited by Captain Shortwave
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