Focussed Model Discussion

[IDO]

O Downwelling, Downwelling, wherefore art thou Downwelling? 

Anyway, the wait continues, anyone for a cold Spring?

The GEFS have a small cluster doing their best to disrupt the PV (lobes) but all in all, if a full downwelling is happening, then it is only showing subtlely on the 500hPa charts.

It appears there remains interference blocking any MJO Pacific forcing and that does not look like helping with a more blocked pattern.

The story, mostly, appears to be wedges of heights pushing north-east maybe veering north, directing the cold towards our sector. But seeing no sign in the medium term for any hardcore cold.

The long-wave pattern with a flat upstream and HP cells moving west to east means an active Atlantic wave. With some well-placed disruption or LP phasing, we may get some wedges further north that may lead to some surprises, but it does look like repeated shots to try and get a more amplified HLB is going to be painful to watch and not really a solution for a long term block.

Now is the winter of our discontent made glorious summer...

 

[Sky Full]

Looking at the way the models handled yesterdays events, here are the charts which the main models were showing on the 23rd January for the 29th January:

UKMO       ECM 

GFS          GEM 

....and here is what actually happened (GFS 0Z and 12Z from yesterday:

             .            

For me, the UKMO is the winner in getting the most detail right, but in terms of the general shape of things I don't think any of them did too badly at +144hrs having successfully predicted the position of the main weather influences - the Azores high and the large area of low pressure to the north east. They have therefore managed to predict the direction of the air over the UK and the low pressure area moving into central Southern Europe.  The main feature they all missed is the small low pressure in the bay of Biscay which brought the rain and snow to many parts and which was a late development.  This reinforces my impression that for local events (i.e. events affecting the UK alone) we can't rely on the models for detail at much more than +72hrs. 

 

[knocker]

Deleted

Edited January 30, 2019 by knocker

[knocker]

44 minutes ago, IDO said:

O Downwelling, Downwelling, wherefore art thou Downwelling? 

Anyway, the wait continues, anyone for a cold Spring?

The GEFS have a small cluster doing their best to disrupt the PV (lobes) but all in all, if a full downwelling is happening, then it is only showing subtlely on the 500hPa charts.

It appears there remains interference blocking any MJO Pacific forcing and that does not look like helping with a more blocked pattern.

The story, mostly, appears to be wedges of heights pushing north-east maybe veering north, directing the cold towards our sector. But seeing no sign in the medium term for any hardcore cold.

The long-wave pattern with a flat upstream and HP cells moving west to east means an active Atlantic wave. With some well-placed disruption or LP phasing, we may get some wedges further north that may lead to some surprises, but it does look like repeated shots to try and get a more amplified HLB is going to be painful to watch and not really a solution for a long term block.

Now is the winter of our discontent made glorious summer...

 

And I feel the upwelling is pretty much guaranteed

[Zakos]

An interesting period of cold and unsettled weather ahead, giving an opportunity for significant snowfall in the south, aswell as country wide snow showers.

Not a snow-fest by any means but a welcome relief from this rather drab winter we have had so far I'd say.

Thereafter, tentative signs of some notable cold encroaching from the east. The 06z is a drastic improvement... with high pressure centred over Scandinavia. This is what we want to see in the output IMO.

A potently cold and snowy spell of weather could soon be upon us...

The 06z unfortunately fires up the PV over Greenland, scuppering the cold spell just as the cold air gets to our shores...

The CFS output for the month however would have us locked into a cold pattern for weeks on end.I personally feel this is the more likely scenario, it has been hinting at this for several days now and the blocking signal grows ever stronger.

 

 

Edited January 30, 2019 by Zak94

[Vikos]

EC MJO favors a quick 7

 

(preview is not actual, click to acutal chart)

Edited January 30, 2019 by Vikos

[Man With Beard]

My views on where we are headed towards mid-February are starting to become clearer. On the face of it, a chart such as this:

suggests a very simple High pressure just to our east, without any prospect of major cold or major mild (apart from in the NW). Quite a standard chart.

What the mean doesn't tell you is that the vast majority of ensembles have much stronger highs; typically 1040mb or more. And, as I noted a couple of days ago, these highs are in random locations close to the UK. The mean doesn't really help us to see that. However, the clusters do:

It's clear pretty instantly that we have members with strong highs to the NW, strong highs close to the UK, strong highs to the NE, and strong highs to the SE (anomaly not as strong here but will still represent a good high as mean pressure in this location in historically higher than in the other locations).

To me, the balance is starting to favour the northern blocking scenarios of clusters 2, 4, and to some extent 3. 

The mean temperatures do not look exciting for cold

but I think this is initially due to a lag created by a temporary infusion of SWlies around D8-D10, and the impact of the "mild cluster" (25%) which takes temperatures close to the teens. As D15 approaches, the clustering of temperatures moves more and more below 5C.

So all in all I think prospects of another cold blast are looking good as we go into the second week of February, but I think the models indicate there may have to be a milder period for a few days before then, and even if a block does set up to the north then cold may not be instantaneous as milder air would need to be worked out first.

There is, of course, a reasonable chance of the milder spell bring more prolonged, and high pressure getting stuck to our east rather than north - but right now I'm putting the odds of milder air staying in place throughout the first half of February as 30%, and the odds of another colder period as 70%. Those types of odds tend to be significant

 

[stodge]

Afternoon all

I must confess the story of rising pressure to the NE is becoming more interesting with each model run:

To compare (as we should) day to day rather than run to run:

GFS 06Z T+222 yesterday:                       GFS 06Z T+198 today:

The 06Z Control becomes very anticyclonic as does the Parallel in the end. 

ECM this morning showed a big push of very cold air (-16 850s) coming west and north west out of Russia but it's hard to see that getting near us looking at the synoptics on offer.

A step forward so far but a very long way off at this time.

 

[Vikos]

slight pattern change predictited if I see this one correct...

[knocker]

A widespread frost in the morning and quite severe in northern Scotland. Some freezing fog around in parts of central and eastern England

[bluearmy]

Berlin reveals that yesterday’s op showed a reversed flow in the trop 60/70N for days 1 through 9. 

Given that we see an AO of -3 by Friday and we are currently in a wintry set up, we will be quite unlucky to see a form of zonality return next week (which doesn’t dive or split favourably) 

i suspect glosea did a good job in spotting this reversal but not such a good job in having the Canadian vortex so deep 

its tough on our little island to see winter - shows how incredible last feb/March’s beast really was ! 

[O'Maille80]

9 minutes ago, bluearmy said:

Berlin reveals that yesterday’s op showed a reversed flow in the trop 60/70N for days 1 through 9. 

Given that we see an AO of -3 by Friday and we are currently in a wintry set up, we will be quite unlucky to see a form of zonality return next week (which doesn’t dive or split favourably) 

i suspect glosea did a good job in spotting this reversal but not such a good job in having the Canadian vortex so deep 

its tough on our little island to see winter - shows how incredible last feb/March’s beast really was ! 

 

Last year was good but shortlived, 2009/10 was the real daddy. Will not see a winter like that again for a long time.

[knocker]

The 'low' at 1500

[knocker]

According to the gfs after the end of the week trough slips east, a transient ridge before the next trough with an active frontal system arrives at the beginning of the week with rain and snow on Sunday with snow proceeding the front over the higher ground in the north, For the next two or three days it's the east bound energy battling against the resurgent subtropical high ridging north east and weak fronts do manage a break through on Wednesday bringing some rain with them  But thereafter the battle continues afresh Variable temps during the week swinging around the average

Edited January 30, 2019 by knocker

[knocker]

The ecm has frontal wave bringing some rain, sleet and snow to the northern half of Britain on Monday. Then a brief skirmish with the amplifying ridge before the next trough arrives on Wednesday

 

[knocker]

Quite incredible in North America at the moment. Looking some of the soundings like Wilmington in Illinois there is vrryually no troposphere and in Manitoba there is none

 

[cheeky_monkey]

7 minutes ago, knocker said:

Quite incredible in North America at the moment. Looking some of the soundings like Wilmington in Illinois there is vrryually no troposphere and in Manitoba there is none

 

Temps collapse into the -30's over the weekend here as another cold plunge occurs...this time a bit further west

[johnholmes]

1 hour ago, knocker said:

Quite incredible in North America at the moment. Looking some of the soundings like Wilmington in Illinois there is vrryually no troposphere and in Manitoba there is none

 

Is that faux cold then?

[bluearmy]

@Man With Beard will be along with some encouraging clusters for approaching mid feb ........

[ICE COLD]

21 minutes ago, bluearmy said:

 

Edited January 30, 2019 by ICE COLD

[Man With Beard]

50 minutes ago, bluearmy said:

@Man With Beard will be along with some encouraging clusters for approaching mid feb ........

Something like this? 

[knocker]

The 500mb and surface analysis for midnight and the 0300 UK surface chart

The key to the next 36 hours is the movement of the low to the west of Ireland which will determine that of the front and thus that of the band of rain, sleet and snow.

A cold start to today as can readily be seen glancing at the temps at 0300 with fog in many central southern and eastern areas, Where this lingers it will remain pretty cold during the day. But by 0900 rain will be effecting Cornwall and during the day this band will track steadily north east turning to snow as it goes as it hits the entrenched colder air. Thus a dodgy rush hour this evening in many areas so take care.

During this evening and overnight is where it becomes tricky as the low tracks south east to be west of France because this pivots the front which pushes north a tad before it stops and it starts to fizzle out. Thus still some uncertainty on intensity and type, in the south east in particular.

The rain, sleet and snow should clear the south east during Friday morning resulting in a much better day, albeit still cold, with some wintry showers along the east coast and north west Scotland

Overnight Friday and through saturday the trough moves away south east and high pressure nudges a tad north east resulting in a dry and sunny day for most but cold.

Over Sunday and Monday an active frontal system with developing waves pushes through the ridge to bring some rain, sleet and snow before clearing on Monday But at the same time a low is undergoing explosive cyclogenesis in the western Atlantic as it tracks north to be south east of Greenland and a front associated with this will bring rain through the country on Tuesday. A cold day on Sunday nut less so Monday

Edited January 31, 2019 by knocker

[knocker]

To continue briefly with the gfs. The front clears in the early hours of Wednesday but by now the Atlantic is dominated by the upper trough and more frontal systems sweep through overnight Wednesday with some heavy rain and strong winds, possible gale force in exposed areas. And this is repeated on Friday

Edited January 31, 2019 by knocker

[knocker]

Some quite low temps on the 0600 chart, although currently +5C here, with freezing fog around. Rain expected shortly

[knocker]

Nothing much different with the ecm

A waving front passing through on Monday with the deep low tracking north towards Greenland. And then the front associated with this brings some heavy rain on Wednesday which deconstructs courtesy of the burgeoning ridge to the north east

 

Edited January 31, 2019 by knocker