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Model Output Discussion - 10th Jan Onwards


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Actually as of last night, 50% of MOGREPS members heralded an easterly by next Fri and that suite is currently exhibiting near record high levels of Shannon entropy out through day 10 onward. Given some support (albeit still minority) in EC ENS for cut-off low to SE and easterly feed, UKMO urging caution on being too prescriptive end of next week onwards, despite majority westerly solutions. In short: nothing yet discounted.

Thanks for that Ian, I was obviously going on old data. I'm certainly tempted to be a bit more positive about some cold potential based on your comments but still maintain a healthy dose of doubt based on both previous experiences and the comment about the dreaded high Shannon Entropy present at the moment in the forward picture. Overall though good news for coldies.

Edited by Purga
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Some interesting members in the extended range of the 06z GFS ensemble suite. 

 

http://www.meteociel.fr/cartes_obs/gens_display.php?x=306&y=141&run=6&ville=Londres&runpara=0&type=0&ext=1

indeed not very cold but I expect cold enough for something wintry at times although nothing extreme in regards to air temps but that could change if fallen snow and clear skys at night.

 

so on we all march with our snow shovels and dew point android apps waiting with anticipation for the all important timeframe Posted Image

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Ecm 00z ensemble mean shows a very interesting twist to the current unsettled pattern developing with something of a standoff between the cold block to the east and the atlantic, the mean shows a trough breaking forward from the main atlantic low and it digs further south which sucks colder continental air into the uk in the process and the combination of that and low pressure could spell SNOW for at least higher ground. There is nothing I would call mild in the pipeline, indeed, the winter so far hasn't been mild, just rather average on the whole, temperature wise but there are signs that our weather may possibly turn rather more wintry next week and onwards, and not just for the hills.

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post-4783-0-11187600-1389874373_thumb.gi

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Ian F a request please

 

I am not alone it seems in not totally understanding what this part of your post means

that suite is currently exhibiting near record high levels of Shannon entropy out through day 10 onward

 

Could you explain this for folk please-?

many thanks

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Ecm 00z ensemble mean shows a very interesting twist to the current unsettled pattern developing with something of a standoff between the cold block to the east and the atlantic, the mean shows a trough breaking forward from the main atlantic low and it digs further south which sucks colder continental air into the uk in the process and the combination of that and low pressure could spell SNOW for at least higher ground. There is nothing I would call mild in the pipeline, indeed, the winter so far hasn't been mild, just rather average on the whole, temperature wise but there are signs that our weather may possibly turn rather more wintry next week and onwards, and not just for the hills.

 

Sorry, the statement in bold is just false.  The winter so far has been very mild as indicated in the CET:

 

December 2013: 6.3C

January 2014 (to date): 6.2C

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Tamara my what a fantastic post absolutely enjoyed that.

 

as for this quote:

She is displaying the patience of many females in this respect Posted Image and I'm sure many members will keep hoping she will pounce at her first opportunity to strike westwards.

 

ive clearly been looking in the wrong places for woman that display patience Posted Image 

 

but still your post was absolutely informative and as direct and realistic and reminded me of the great glacier point post many thanks. 

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That is quite a change Ian, correct me if I am quoting wrongly, but Jo suggested that <10% showed that on the 00z run?Is it normal, if my comment is correct, for MOGREPS to show such large swings in such a short time. Second question is how much credence does the senior man at Exeter give to this suite?

No, as of their assessment published last night based on 12z MOGREPS they say "nearly 50%" of MOGREPS offered easterly by next Fri/weekend. They haven't clarified proportion in 00z run but merely note "nearly record high" levels of Shannon Entropy and similar high levels in EC with 25% members offering the cut-off deeper vortex to SE. This still not favoured but not discounted either. MOGREPS given v high credence at Ops Centre, re your second query.
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Yes- there has been a consistent but not dramatic drop of the ens, and less showing mild

 

Definately, the 06z ensembles are the best we have seen for a seven days from the GEFS  

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post-4955-0-86005700-1389875174_thumb.pn

Edited by Nicholas B
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Actually as of last night, 50% of MOGREPS members heralded an easterly by next Fri and that suite is currently exhibiting near record high levels of Shannon entropy out through day 10 onward. Given some support (albeit still minority) in EC ENS for cut-off low to SE and easterly feed, UKMO urging caution on being too prescriptive end of next week onwards, despite majority westerly solutions. In short: nothing yet discounted.

 

Hi Ian,

 

Thats quite a turnaround from a few days ago of less than 10% I believe it was ? What has changed ?

 

A lot of members throwing around the term Shannon Entropy as of late. If you try and Google what this means, it offers very little of understanding !

 

I believe, and correct me if I am wrong anyone, what Ian F refers to an output the DECIDER model from the Met Office ?

 

I found the following chart:

 

Posted Image

 

So we can see what Ian is referring to re "Record Highest Entropy" - I am not sure if this is still the latest record or not.

 

For those with slightly poorer vision, albeit it's difficult to read with 20/20 vision, the text on the image states:

 

 

High Entropies indicate a wide diversity of synoptic types across the ensemble members.

 

 

Low Entropies indicate that most ensemble members fall into a small number if synoptic types.

 

So basically, High Entropies = Several outcomes possible (In this case 50/50 Easterley VS Atlantic)

 

Low Entropies = Smaller number of outcomes

 

**If this is wrong, someone can correct me !!**

 

Hope this helps, as it sure helped me.

 

Glenn

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A few bits from a last post simply for continuityPosted Image

 

...And pretty much as expected we continue to wait as nothing, essentially, has changed too much. Though a corner is continuing to turn, albeit we wait to see if/when we might benefit.

 

As the models continue the on/off tease of ongoing trough disruption beyond 5 days away, I see there has continued to be a lot of posting analysis through the last couple of days over the possibilities (or not as the case may be) of getting that ever elusive fledgling easterly into the UK to at least get some surface cold from the continent and do a few other very useful things in the process.

 

Apart from bringing (at least marginal) snow potential to some of the UK, it would do another very useful thing we are badly crying out for and that is produce much lower dewpoints for the first time properly in weeks and weeks, and downgrade the relentless downpours that are taking a bigger and bigger toll around the country.

 

This is the problem with the extreme cold in parts of the US and Canada, courtesy of the section of vortex long established over that section of the arctic - since the start of December in fact, when as predicted at the time, it relocated over the pole from Siberia and kick started the zonal pattern. This  Canadian vortex may be relatively weaker than it was through the festive period and into the start of the New Year, but it is still the route of the low pressure production line that is plaguing the UK as the cold air meets the warmer moister air and spits the low pressure energy towards us.

 

With the atmospheric and upper air patterns stuck in a rut with this upper trough to the NW, the  Siberian/Scandi High is also persisting and sitting there quietly and patiently (much as expected over the last week or so that she would stick around after being computer modelled to say 'Hi' from NE Europe) . She is displaying the patience of many females in this respect Posted Image and I'm sure many members will keep hoping she will pounce at her first opportunity to strike westwards.

 

Within the context of the present pattern the Scandi High is proving on the one hand a carrot/stick  hope of getting out of the awful micro pattern the UK is stuck under to dry things out and give households, roads and infrastructure a much needed break - but also a source of considerable frustration in terms of just too much energy still remaining in the upper vortex pattern to the NW to enable even that slightly higher degree of trough disruption to the UK that would allow the High closer and provide the colder interest we are looking for.

 

It might still require a fair bit more to advect the embedded deeper upper cold tucked around the eastern and southern peripheries of the High over western Russia, but not too much at all to produce something of interest to parts of the UK, albeit marginal in nature.

 

The EPS members show that stalemate and frustration evident still at day 5 from todays modelling. It looks as though the ECM hasn't updated for several days looking at those maps.....!!

 

Posted Image

 

It has always been a long game this winter with such a strong vortex pattern, but to give a large negative a relatively encouraging positive - I remain struck how since the initial recent attack on the winter time vortex that the jet stream wants to split and at least try to disrupt low pressure into Europe against the background of the remaining westerly energy budget in the overall pattern. This reminds us that we are still firmly in the alleged post mod-ern period since 2007 even during a highly discouraging winter pattern, the last such we saw in 2006/07 which featured a turbo charged zonal deeply +AO profile. That one remained flat and steadfastly refused to show trough disruption until it was too late. Much later than we see apparent this winter.

 

Though the weather in the UK on the ground remains as miserable as ever (albeit the damaging gales are less prevelant) this is a distinct change in the weather pattern from much of the second half of December and the first week of January, and no longer do we see the most energetic storm systems approaching on an extreme temperature ignited flat jet stream pattern.

 

We require another, and bigger hit to turn wannabe trough disruption into something greater to force heights to the NE west. Also some help from a stagnant MJO would also help force the upper air pattern out of its rut and assist this happening. Wavelengths are changing seasonally, and such changes will surely come.

 

Painfully slow as it is, signs continue to indicate that the vortex will continue to decay through forecasted 'warming out' and dropping of zonal winds and there is still major warming 'interest' for the start period of February. We can never guarantee cold spells here in the UK but over the coming days we may well see the tide start to turn with the models showing the pattern incrementally gradually adjusting west. That glimmer is apparent today. 

 

Its a sequential programme of flushing out the extra westerly energy into the troposphere akin to slow teeth extraction and then waiting to see the improvement thereafter.  How much more anaesthetic is required?

 

Hopefully not too muchPosted Image

Well firstly , thankyou for sharing your understanding with us all , I always look for your updates and I'm very impressed as to how accurate your thoughts have been so far this winter , and sobering as your thoughts have been , it's always kept my feet well and truly grounded .

What I also know is a ramp when I see one !! And I'm not suggesting that's what you've just done , but it's also easy to see your thoughts are beginning to swing ?! Patience had certainly been required this winter , but I do finally see things changing , right on que with chiono's winter forecast actually , regarding the second half of winter , I do think many underestimated the vigorous vortex aiding the jet stream this year when the final winter forecast was made , because many people went for a very dry December , dominated by mid latitude blocking , but we know things didn't turn out like that .

But what was clear from the beginning was , with +QBO , solar maximum , cold stratosphere , and limited SSI , that this winter was going to be slow burner , and chiono excellently predicted the scandi high to become a major player as the winter progresses , and it clearly is .

As the vortex is (although quite strong still) on the ropes from the recent wave 1/2 activity , along with the fact it's past it's sell by date , it's only going to weaken further over the next month , along with the fact we have a much stronger warming in the pipe line (consistently showing in fi and getting closer) , it does look like we have a much better chance of seeing winter finally show its face as we head toward feb, lets not forget march can be nothing other than an extended winter month given the right Synoptics .

So It does look like the tide has turned somewhat , and next week looks like some of us may see our first snow fall of the season . Once we can get cold air in place , then things can look very different very quickly with the models , and I genuinely believe we will begin to see the models move toward undercutting scenarios over the next 5/6 days .

Interesting times and good to see the MORGREPS sniffing the coffee again .

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Sorry, the statement in bold is just false.  The winter so far has been very mild as indicated in the CET:

 

December 2013: 6.3C

January 2014 (to date): 6.2C

 

How is that Very Mild ? I think you may be reading them wrong.

 

The current CET is 6.2C for January, the average is roughly 4.2C, so thats just 2C above average.

 

NB - The data is generally taken from the Midlands Area. There has been quite a split/stark difference also with North/South divide. 2C above normal is no where near very mild.

 

Would you consider the North Pole at -50C and in 2014 it was -48C - Is that very mild?

 

Posted Image

 

Posted Image

Edited by Glenn W
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Tamara my what a fantastic post absolutely enjoyed that.

 

as for this quote:

She is displaying the patience of many females in this respect Posted Image and I'm sure many members will keep hoping she will pounce at her first opportunity to strike westwards.

 

ive clearly been looking in the wrong places for woman that display patience Posted Image 

 

but still your post was absolutely informative and as direct and realistic and reminded me of the great glacier point post many thanks. 

Very kind but far far too generous!Posted Image There are plenty other members with greater technical knowledge who would still work hard to try and approach his depth of ability as he demonstrated so often on herePosted Image

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Perhaps the word you're looking for is - realistic?

with MOGREPS only yesterday as IF suggests, 50% of possible more easterly outcome and related recent cross model flip flopping its no wonder at present the longer term remains unchanged via METO, thus shannon entropy ) amany of possible solutions outcomes. However it may take whole new reading should current trends hold firm, and upgrade surely? !
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Maybe some hope in Ian's recent comments re MOGREPS - If I remember correctly MORGREPS  was a big factor in the METO not backing the failed Easterly forecast last week, for this week?

 

Also, regarding the high level of 'shannon entropy' could this also be a positive thing? I've heard it time and time again that the models struggle with reverse zonality/NE blocks, but are very good with zonal/Atlantic driven weather, so the fact they cannot forecast with high confidence what they are 'good at' suggests to me that Atlantic driven weather is less likely?

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So having read Ian F's update it looks like complete chaos has broken out in the modelling.

 

The interesting trend from the last few days has the been the stubborn resistance of the high to the east and the suggestion of another lobe of high pressure appearing over the Arctic and extending se towards the Svalbard region.

 

Theres often a domino effect with the ensembles because if the troughing disrupts more favourably initially then everything after changes because of that, the ensembles members which have no undercut will simply drive the pattern much further east, and when the next low approaches there will be less blocking to divert the energy.

 

So you do end up with a very skewed picture, its not like a northerly toppler or say a bog standard PM flow, its a bit like tennis modelling blocking to the ne moves the NWP from the Challenger circuit to the Masters Series, its a whole different league!

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How is that Very Mild ? I think you may be reading them wrong.

 

The current CET is 6.2C for January, the average is roughly 4.2C, so thats just 2C above average.

 

NB - The data is generally taken from the Midlands Area. There has been quite a split/stark difference also with North/South divide. 2C above normal is no where near very mild.

 

Would you consider the North Pole at -50C and in 2014 it was -48C - Is that very mild?

 

Posted Image

 

Posted Image

 

An anomaly of around 2C for a period of 1.5 months is what I would call very mild (when referenced over the winter period in the UK). Put it this way, it isn't average!

Edited by mulzy
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A better overall trend on the 06z ENS with the OP on the mild side at the end & diverging notably from the Control run, highlights still a lot of uncertainty of course

 

Posted Image

Edited by Purga
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How is that Very Mild ? I think you may be reading them wrong.

 

The current CET is 6.2C for January, the average is roughly 4.2C, so thats just 2C above average.

 

NB - The data is generally taken from the Midlands Area. There has been quite a split/stark difference also with North/South divide. 2C above normal is no where near very mild.

 

Would you consider the North Pole at -50C and in 2014 it was -48C - Is that very mild?

 

Posted Image

 

Posted Image

 

 

I listened to something on the BBC website recently that said that December was the 6th warmest since records began. January is running at similar levels so far.

 

If you feel that this isn't worthy of being categorised as very mild, then I hope I never see a winter that you do feel worthy of this title Posted Image . Our climate is governed by relatively modest temperature swings during winter months so whilst a 2C swing might not be significant in some climate zones it sure is for us.

 

Meanwhile back on topic.............

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So having read Ian F's update it looks like complete chaos has broken out in the modelling.

 

The interesting trend from the last few days has the been the stubborn resistance of the high to the east and the suggestion of another lobe of high pressure appearing over the Arctic and extending se towards the Svalbard region.

 

Theres often a domino effect with the ensembles because if the troughing disrupts more favourably initially then everything after changes because of that, the ensembles members which have no undercut will simply drive the pattern much further east, and when the next low approaches there will be less blocking to divert the energy.

 

So you do end up with a very skewed picture, its not like a northerly toppler or say a bog standard PM flow, its a bit like tennis modelling blocking to the ne moves the NWP from the Challenger circuit to the Masters Series, its a whole different league!

Hi Nick -Looking at all the NWP output over the last 24 hours we have more chance of a PM flow than a cool continental flow within T+168 perhaps with a bit of snow. Beyond that if zonality digs in again but further south, the cold can flood into central Europe opening the door to our east, with something more realistic to deliver

how's the snow in the Pyrenees'

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Shannon Entropy was the buzz word on here last Winter thanks to Ian. It basically means chaos theory rules and no certainty can be given to one outcome or another.

 

Another less pleasing phrase, might be, fence sitting.

 

Or, "we don't know"?

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