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Model Output Discussion - 23rd Jan - 12z onwards


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Short answer   The short answer to your question is yes, the presence of low pressure (at higher altitudes, being coincident with very cold upper air), makes the air more unstable, as the gradient i

Welcome to "Celebrity Model Discussion". Let's go out to our reporter, who has managed to corner the miracle man himself, Jesus Christ, for his thoughts: Reporter : Thanks for joining us Jesus, first

If people will insist on analysing the 850mb temperatures every single run here's something to bear in mind when viewing the output for the upcoming period - -6c is a baseline figure to put snow/rain

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The icing on the cake tonight is provided by the Ecm 12z ensemble mean, it shows arctic air flooding south across the UK from later next week onwards, so it looks to me like our first nationwide arctic spell is on the way with most of us having snow, frosts and ice but also gales, severe gales and perhaps storm force winds. This could be a high impact wintry event we are facing in around a weeks time.

It's a long way off at this stage and we can only look at the models last Thursday week showing a very good easterly for the following week only for it to never materialise.  I would take these latest outputs with a pinch of salt. 

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Completely agree Steve on this.

One thing it will do though is hopefully drag some cold enough uppers South that we will have something to work with if the flow turns NE at any point. The failure (in relative terms) of the spell this week had its roots in the initial northerly not happening.

A few really cold GEFS tonight and that is at least progress.

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Ha Steve,

 

I love the reverse psychology. I remember when you last went cold (forgive the pun) on the chances of cold a few years ago.....

 

......the cold arrived!

 

Can lightning strike twice?

Haha I'm sure I can remember thinking that...can't recall which cold spell though?? Surely wasn't one of the majors from a few years back?

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Increasingly strong signals now that a major deep euro trough will develop through middle of next week, ushering in a potent polar/arctic blast in time with very strong winds. Azores high sent packing to the west and forced northwards into a mid latitude block with tentative signs for heights to build over SE Greenland, though there will be energy in the jet which could well produce further shortwave/low pressure activity which will get sucked into the euro trough maintaining a very unstable more polar maritime airflow as opposed to arctic, but still a very cold one all the same.

 

Anyone hoping for cold and snow, will be very pleased with the model outputs of the last 24-48 hours, with only a couple of milder blips ahead in the short term.

 

 

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Just a little question and please forgive/be tolerant if it is obvious, but if we get a northerly wind in a week's time, is it going to be surface air coming towards us from e.g. Kiruna or somewhere northern, in which case can we get an idea of what temperature it will be for us by looking at their current weather outlook? or would our air in a week's time be coming from the high atmosphere above Kiruna etc? In which case, where would their surface air end up?

 

post-22381-0-25650900-1422049775_thumb.p

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For the general trend then look at the 500mb 6-15 day charts, reasonable consistency it seems to me from here, and the flow is predicted to be North of west and relatively cold. It will happen, detail of course from the synoptic models once they also show consistency in a similar time scale. Correction the detail will not be known until about 72h for each particular day.

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It's a long way off at this stage and we can only look at the models last Thursday week showing a very good easterly for the following week only for it to never materialise.  I would take these latest outputs with a pinch of salt.

This is different to last time, much more support and I expect our first arctic blast will hit the UK later next week with reload potential further on, i also expect to see sub -10 T850 hPa to surge down across at least the north with 510 dam thicknesses into the far north. The bottom line is I expect upgrades nearer the time.

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Cold , windy and heavy rain on latest long range from BBC, but showing a Nw'ly flow. I guess that bit is guaranteed, now a few days wait to get an idea of how cold it will get before knowing a if we are to get a potential very cold spell. If charts are the same tomorrow evening then maybe the long range may start to mention the S word.

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The charts are looking good around T+144 hrs ,may I also add there is still a good 6" covering of snow on higher routes near me with little thaw of late.

Edited by sorepaw1
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i cannot make a confident call on the longevity of this cold spell until i see the split vortex going within day 10. the low res eps seem too keen to rebuild the canadian prime segment around baffin.  what should be noted is that naefs and ecm extended have been consistent in this trend to rebuild the 'prime' canadian vortex in that locale. the siberian master all too short a feature for us this side of the NH.

 

Indeed.

 

I suspect that despite the slight propensity at 10mb to shift the vortex polewards once again as we see the decline of the geopotential wave 1 towards day 10, beyond that we are likely to see a significantly higher than average ensemble spread, courtesy of this ongoing signal through days 10-15:

 

gensbcnh-21-7-384.png

 

I suspect spreads and ensemble means are going to be a little difficult to track through this period in the days to come and as you suggest it's a case of hoping there is more clarification on offer once this reaches the higher resolution of the EPS suite.

 

I have very little faith in what comes after the initial Northerly right now and it is likely to be sometime towards the end of next week before I think we will see that one resolved.

 

SK

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This is different to last time, much more support and I expect our first arctic blast will hit the UK later next week with reload potential further on, i also expect to see sub -10 T850 hPa to surge down across at least the north with 510 dam thicknesses into the far north. The bottom line is I expect upgrades nearer the time.

it's too early to get excited, northerlies rarely deliver to the majority of the UK, our best option is from the east. All our notable winters have come from the east, not the North or northwest. There are some signs of height rises to the north so fingers crossed.
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-6c uppers and Snow Midlands North by Wed on last 2 GFS runs. This isn't FI, 5 days time isn't too far away so surely a possibility.

Edited by Ali1977
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Ha Steve,

I love the reverse psychology. I remember when you last went cold (forgive the pun) on the chances of cold a few years ago.....

......the cold arrived!

Can lightning strike twice?

maybe the turkey photo need to change to chicken lol ( only joking u know a cold spell is coming when Mr Murrs is posting! Edited by snowice
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Cold , windy and heavy rain on latest long range from BBC, but showing a Nw'ly flow. I guess that bit is guaranteed, now a few days wait to get an idea of how cold it will get before knowing a if we are to get a potential very cold spell. If charts are the same tomorrow evening then maybe the long range may start to mention the S word.

..........just as tonight's GFS is showing. No over excitement yet!

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The charts are looking good around T+144 hrs ,may I also add there is still a good 6" covering of snow on higher routes near me with little thaw of late.

Just pop your location in pls do we know where you are talking about, cheers.

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Ha Ha Chiono I remember that - i think 2+ years ago now - i think id just given up. Maybe end feb 13-

Anyway gfs out to 180 only -4 across the UK

Remember no blocking high = limited scope of CAA

Maybe things will develop favourably in FI

S

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Ha Ha Chiono I remember that - i think 2+ years ago now - i think id just given up. Maybe end feb 13-

Anyway gfs out to 180 only -4 across the UK

Remember no blocking high = limited scope of CAA

Maybe things will develop favourably in FI

S

I'm looking at a cutting off Euro low again to our SW after the slider - the way to deep cold (perhaps)

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Another run that extends the level of split within high res. wonder if low res will put the Canadian back together again as main lobe.

The higher res thing interests me as neatly all suites/models control runs have a significant neg -AO phase upcoming.

Edited by bluearmy
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Cold , windy and heavy rain on latest long range from BBC, but showing a Nw'ly flow. I guess that bit is guaranteed, now a few days wait to get an idea of how cold it will get before knowing a if we are to get a potential very cold spell. If charts are the same tomorrow evening then maybe the long range may start to mention the S word.

 

 

Met Office forecast is saying 'increasing risk of snow in the north' - probably the most definite they have been about the prospects of snow hitting a part of the country all winter - none of the talk of 'wintry showers' or 'sleet and snow'. Yes it only mentions the north at this stage, but its a start. I also noted yesterday's winter watch forecast which stated return of cold weather likely rest of winter after a milder spell coming days.

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