Model Output Discussion - 10th Jan Onwards

[snowking]

Would love to know why Piers Corbyn at Weather Action is saying his Feb 45 day forecast is the most important event since 2010 but I can't bring myself to spend £25 to find out…without being unfair to Mr Corbyn and revealing his forecast or offering anything too specific, does anyone have any idea what he's on about, i.e. is he predicting a particularly snowy month which is, I suppose, my inference due to the 2010 comparison? Piers_Corbyn tweet BI FEB 45d IS LOADED "WA's most important fcst since Dec 2010"

For informational purposes (as I've seen a couple of comments about this) the Feb 45 day that I've read suggests a very mild February - think the mentioning of December 2010 is just a sales ploy and bares no relation to the forecast for Feb '14But if you would like some more comforting news his forecast this winter so far has been (as ever) very hit and miss, with two previously forecast snow events across England and Wales having failed to materialise, so I wouldn't hang too much upon his words.SK

[CongletonHeat]

As we are on the topic of BBC forecasts is there usually this much uncertainty past 5 days in the possible minimum/maximum temperatures? For my location there there is a difference of 10 degrees between possible minimum and maximum temps for Friday and the same for the following week. Surely the BBC forecast isn't usually so non-committal and must reflect the current uncertainty that exists despite some advocating a certain continuation of Atlantic dominance. If it is always like that at day 6 I apologise for this post.

It is.

 

I only really replied to this as I think it is weird why you become a teapot.

Edited January 19, 2014 by CongletonHeat

[Paul White.]

Winter is coming..nuff said

The words of winterfell

[fergieweather]

As we are on the topic of BBC forecasts is there usually this much uncertainty past 5 days in the possible minimum/maximum temperatures? For my location there there is a difference of 10 degrees between possible minimum and maximum temps for Friday and the same for the following week. Surely the BBC forecast isn't usually so non-committal and must reflect the current uncertainty that exists despite some advocating a certain continuation of Atlantic dominance. If it is always like that at day 6 I apologise for this post.

We show ensemble spread on web temperatures now into that range.

[Tamara]

In the light of hearing of the apparent MOGREPS backing to the UKMO (at least at the present time)and a rather more favourable set of latest ensembles from the GEFS it might be worth revising the prospects for next weekend in terms of the colder solution as *unlikely* to *cautiously possible*...at least for the time being. I mentioned earlier about skewed individual sets of ensembles and waiting for further subsequent clarification - well if we take a look at the ECM ensemble maps as far as we are allowed to see them nowadays (which is day 5) then we can clearly see the larger percentage of progressive solutions and just a minority that look more like the UKMO solution

 

This set of data, as a suite, might show apparent overall consensus - but then it is not uncommon for subsequent suites to show a consensus at the other end of the spectrum. Most especially in a complex set of pattern ingredients as we have at present.

The overall trends remain as stated, and the premise of my earlier post obviously doesn't change at all as a result of this in respect of the jetstreak programmed thereafter out of NE Canada and all the other points that were made in association to it - polar height rises etc. However, clearly as nick s has rightly said, any earlier westward adjustments of the pattern (if they were to occur) are bound to help our cause later on too.

 

My suspicion has always been (and still is on balance) that too much westerly energy still resides in the pattern to allow such adjustments certainly as soon as next weekend, but we have been in this situation for some time whereby any westward upper air pattern adjustment (it only requires slight adjustments) if and when it occurs, will have quite a significant effect on the surface pattern for our small Island with all that cold air sitting to our east and north east. The UKMO 850 chart shows how this could arrive on our doorstep in what is realistically probably the most bullish coldest scenario achievable at this time.

 

 

If (and it is a big if !) any late westward adjustment can occur prior to the programmed energy transport from NE Canada, then this obviously increases short term snow potential next weekend, but also subsequently increases the chances of the next jet energy spitting out from the Canadian vortex immediately afterwards being disrupted much better downstream, thereby downgrading westerly progression, and allowing the more favourable colder, longer term solutions to verify as well...i.e better atlantic amplification in its wake as heights rise to the north with the troughing deeper into Europe. This is the proverbial pin question that blue army has alluded to with so many upper features vying for supremacy at the same time as an Arctic High appears.

 

So, this is where the waiting for comparisons of ensemble and other data comes into its own - the ECM and GFS ensemble data edging the way of the UKMO/MOGREPS solution would be a large bonus to take into a programme of arctic height rises to follow, but will it happen?...

 

Thanks very much Ian for that modified chart - slightly adjusted eastwards as might be expected but not by too much

Edited January 19, 2014 by Tamara תָּמָר

[fergieweather]

Reference Tamara's post above, it'll doubtless help discussion if I copy here how the Dep Chief modified the UKMO-GM last frames from the 00z run. Clearly, longevity of the ridging to E is critical here (12z suites thus awaited with interest):

[Mucka]

I think Ian's "lack of coherent signal" sums things up nicely.

We all use different terminology to express the same thing, uncertainty.

Most of the conflicts in this thread are mere semantics - nothing more than degrees of uncertainty.

I don't like conflict but I do like uncertainty and that is what makes model output compulsive viewing for me - the more uncertainty the better and we have a high degree of uncertainty at the moment so I'm in hog heaven.

 

This mornings ECM was a bit of a shocker wasn't it?

While UKMO was like waking up and smelling bacon sizzling in a pan and coffee on the go. (at least for shorter term prospects)

The differences are stark by 144h yet very subtle differences in the much closer time-frame are responsible and that is the modelling of the Azores high or the way the jet is modelled - one and the same - chicken and egg. Essentially ECM has the Azores high ridging further Northeast thus we don't get the same benefits of trough disruption with more energy going SE later.

Ian explained that the MetO see ECM as being more progressive which ultimately it is but it is not faster. That's to say the differences are not so much the timing of low pressure advancing from the Atlantic for me but rather the way the jet is modelled.

If we look at these 48h comparison pressure charts we can clearly see that there is little difference in the westward advancement of the low pressure but ECM (and GFS) have the Azores high ridging further North and so consequentially the low pressure is being forced on a slightly more Northerly trajectory.

UKMO/ECM 48h comparisons

 

 

Although these differences seem negligible they are not at just 48h out and I have to wonder if the difference is more about data input than actual modelling.

Perhaps Ian can elucidate as to whether the data input for UKMO and ECM differs in any way.

 

By 96h the knock on effect is clear and the ECM now looks much more progressive because the low is not being disrupted as efficiently with most of the energy heading NE as it is not meeting as much resistance from the block. It is all about angle of attack for me rather than timing in this instance though timing is always important.

 

 

 

Overall the output has not developed from last night in a way that you would ideally want to see if you are looking for a cold spell to develop.

The models are generally giving the Arctic high a less influential role and as I expressed previously we really need that to force low pressure South into the continent later.

If we can get a good link up between high pressure over Scandinavia and the Arctic it is quite plausible we can get any troughing digging South far enough West to displace the Azores high and build heights to our NW (we are talking about 10 days or so here though) and drag in some cold air over the UK from the North/Northeast. That is not really the way the models are going at the moment but as Tamara has expressed a pattern change is afoot and we really shouldn't expect any of the output to fully represent what we will be looking at in the last week of Jan - particularly the end of Jan/early Feb.

We could easily see some very wintry looking charts for end of January as early as tomorrow evening but if that is the case we should still be cautious because the models will not easily resolve the battle between competing forces and as we know they do not model high pressure over the Arctic very well let alone the usual difficulty they have with the distribution of energy coming from across the Atlantic as it meets a cold block.

 

This has been a dire Winter for coldies thus far and it would be unusual to have a very cold and blocked February following on from a largely mild December and January but there is "potential" at least for a cold spell to develop end of Jan/early Feb even if it is not prolonged deep cold.

In the meanwhile there is at least some interest in the possibility of some short lived wintriness as shown by the UKMO which I must admit took me by surprise. I hope that isn't the outlier it first appears and it can be firmed up upon this evening and tomorrow - oh to see a flake of snow.

Edited January 19, 2014 by Mucka

[nick sussex]

Reference Tamara's post above, it'll doubtless help discussion if I copy here how the Dep Chief modified the UKMO-GM last frames from the 00z run. Clearly, longevity of the ridging to E is critical here (12z suites thus awaited with interest):Screenshot_2014-01-19-14-14-06-1.png

Given the ECM and its ensembles I'm surprised there wasn't more modification, that still looks very close to the UKMO raw output, if MOGREPS is more towards the UKMO version it does seem strange because the differences between it and the ECM would have to start from quite early in the outputs.

[fergieweather]

Given the ECM and its ensembles I'm surprised there wasn't more modification, that still looks very close to the UKMO raw output, if MOGREPS is more towards the UKMO version it does seem strange because the differences between it and the ECM would have to start from quite early in the outputs.

The modification is an advance of the frontal ppn 120NM compared to the raw solution (i.e. a nod towards the EC/NCEP ensemble means, in spatiotemporal sense).

[A.J]

This is how the beeb see things at the moment for the end of the week curtsey of Alex Deakin 15 minutes ago

 

Thursday

 

 

But its by Friday things could come interesting with high pressure over Scandinavia it could bring some cold air from the east or north east if it does it could be a very chilly day even a raw day across parts of England and wales, but weather fronts are trying to bump in from the west and they may eventually win out with the cold air in place for England and wales when the wet weather arrives there is just the possibility and thats all it is at this stage of some snow on Friday night

 

 

 

As we are on the topic of BBC forecasts is there usually this much uncertainty past 5 days in the possible minimum/maximum temperatures? For my location there there is a difference of 10 degrees between possible minimum and maximum temps for Friday and the same for the following week. Surely the BBC forecast isn't usually so non-committal and must reflect the current uncertainty that exists despite some advocating a certain continuation of Atlantic dominance. If it is always like that at day 6 I apologise for this post.

 

 

It is.

 

I only really replied to this as I think it is weird why you become a teapot.

 

 

The words of winterfell

Come on chaps, at least try and mention the model outputs in your posts! 

[Summer Sun]

Latest NAO update shows it around neutral to start with before going positive for the remainder of the month

 

 

Latest AO update starts negative but it heads positive difficult to estimate when but probably somewhere around the 23rd onwards

 

[bluearmy]

First out of the blocks is the gme and at T72, it looks ok re the ukmo 00z solution. Interesting hour coming up!

[Cloud 10]

First out of the blocks is the gme and at T72, it looks ok re the ukmo 00z solution. Interesting hour coming up!

 

A step in the right direction compared to its 00z run (or is that the left direction)

 

00z..  12z..

 

 

Colder uppers getting into the far east on wednesday.

 

 

 

edited cos i don't know what day it is!

Edited January 19, 2014 by Cloud 10

[radiohead]

UKMO at T120.

 

[AWD]

Latest UKMO RAW falling into line with 0z FAX and EC output now with limited scope re colder air fluctuating east coast;

Edited January 19, 2014 by AWD

[Summer Sun]

UKMO keeping the lowest 850's away this afternoon compared to the 00z run where they clipped the east it looks like the low will win out as we move into the weekend so we could still have some leading edge snowfall

 

[MR EXTREMES]

I think its worth noting that once again the jet or vortex does not favour much.

I give up totally I don't see winter at all in any of them charts its a none runner even with the split vortex being around the Canadian area and the jet stream its a no go theres nothing positive to be honest I think this year has been awful and for this reason I bid you all good night I cant take no more all the more experienced posters have made it perfectly clear that there really is not much hope.

Edited January 19, 2014 by phil nw.
removed ot comment

[Bobby]

Rather grim charts from the GFS and UKMO 12z, UKMO backed off that cold push from the east as thought.

 

GFS looks a wee bit zonal at +240

 

PV to our NW + strong Azores high = bad for cold.

[draztik]

Rather grim charts from the GFS and UKMO 12z, UKMO backed off that cold push from the east as thought.

 

GFS looks a wee bit zonal at +240

 

PV to our NW + strong Azores high = bad for cold.

 

Yep Bobby! In line with the ens, for the last umpteen days now! It was always the likely route... and the window we were chasing, seems to be closing fast. Variations to come this week, but cold.... can't see it!

[TSNWK]

Oh my my... UKMO has backed away from the little carrot it dangled this morning, Azores high ridging in at 120 and 144, we might get a a couple of chilly days Wednesday and Thursday. I notice that there is not one single comment on 12z GFS silence speaks volumes I guess... But I'm feeling brave and about to dive in and take a peep wish me luck..

My god I think I deserve a medal for valor after quickly skipping through the 12z GFS.. Azores high is the main player from around 144 to the end of the run..

Edited January 19, 2014 by TSNWK

[chrisbell-nottheweatherman]

Rather grim charts from the GFS and UKMO 12z, UKMO backed off that cold push from the east as thought.

 

GFS looks a wee bit zonal at +240

 

PV to our NW + strong Azores high = bad for cold.

 

Even I, as a total newbie and nowhere near knowledgeable enough as yet to post my views on the models, know that most if not all of the most experienced posters here say that the GFS is too progressive in bringing zonality in around +240 hours.

[Joe Levy]

To those who say that Winter is over (no names mentioned) which is a silly thing to say itself given that we're only half way through and that we can still get cold weather in March and April, I present this chart to you - the SSW is still in the output and is gradually getting closer as the GFS maintains it. If it continues to do so, then I'm sitting firmly in the camp who think that February, traditionally one of the coldest months anyway, has the most potential.

[IDO]

The GFS 12z is horrible end to end. 

 

No prolonged cold, no HLB, no Arctic high, etc

 

By T192 the PV has moved to Greenland: 

 

It then takes a week to move east just north of the UK, by T300: 

 

It then hits the Siberian high and by the end of the run its back where it started: 

 

Not conducive of a cold spell but certainly transient wintry stuff for hills and up north. 

[Summer Sun]

GFS 8 day temperature anomlay once again shows a west east split for England and Wales

 

Average to Slightly below average in the east with the exception of the east Anglia and SE coast line, in the west its average to slightly above average

 

For Scotland and northern Ireland temperatures range from slightly below average to slightly above average

 

 

Normal temps left, expected temps right

 

[gottolovethisweather]

Snow for some on Friday though, yes it does look highly likely that it will be a transitional event, however. Where we go from there, even those "in the know" with their additional supercomputer power don't know. Next weekend could go either way, as SM stated earlier, we all need to focus on that five to six day timeframe. My expectations from this Winter have been greatly reduced given the vortex's power alongside other factors, however there often is widespread snowfall even during the mildest of Winters. Stratospheric signals also look very encouraging and with that in mind, it is possible we could witness another 2013 style Winter into Spring period, we just don't know at this juncture.

Edited January 19, 2014 by phil nw.
removed quoted ot post now deleted