Model Output Discussion

[TEITS]

As others have said an absolute shocker from the UKMO this morning. However I would be more concerned if the ECM agreed which thankfully it doesn't. Having said this I will be very cautious if the UKMO shows a similiar trend on tonights 12Z.

The best model runs this morning are obviously the ECM but also the GEFS mean.

http://91.121.94.83/modeles/gens/run/gens-21-1-192.png?0

Very consistent once again. The control run drops as low as -18C!

http://91.121.94.83/modeles/gens/run/gens-0-0-252.png?0

Still a long way to go yet before we have some clarity. For the time being im just going to watch and wait and not make any assumptions. If all models show an E,ly at +72 then I will be happy.

[Wayneywoo]

According to NetWeather Snow Forecast maps, the central belt of England hovers around the 60% mark for snow on Tuesday according to the GFS 00z. Looking at the ensembles, the Control was a bit of an outlier with regards to PPN for the London area - Ensembles all clump around the 5mm mark. Control is up around 10mm. Other areas, Manchester, Aberdeen - control is within the ensembles so not an outlier for these areas.

Snow forecast - 06-12

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=gfs&MODELLTYP=1&BASE=-&VAR=prty&HH=108&ZOOM=0&ARCHIV=0&WMO=

12-18

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=gfs&MODELLTYP=1&BASE=-&VAR=prty&HH=114&ZOOM=0&ARCHIV=0&WMO=

Interesting. Seems the Atlantic is losing the battle against the cold to our east all the time. Who's gonna win the war? My money is on the Siberian High sending it's troops to us

Edited January 29, 2010 by Wayneywoo

[SussexmarkyMark]

According to NetWeather Snow Forecast maps, the central belt of England hovers around the 60% mark for snow on Tuesday. Looking at the ensembles, the Control was a bit of an outlier with regards to PPN for the London area - Ensembles all clump around the 5mm mark. Control is up around 10mm. Other areas, Manchester, Aberdeen, control is within the ensembles.

Snow forecast - 06-12

http://www.weatheron...0&ARCHIV=0&WMO=

12-18

http://www.weatheron...0&ARCHIV=0&WMO=

Interesting. Seems the Atlantic is losing the battle against the cold to our east all the time. Who's gonna win the war? My money is on the Siberian High sending it's troops to us

Just a word of caution about those snow % charts. A number of times in the last couple of weeks there has been above a 90% chance of snow in this area in the 'now cast' and it was raining!

Edited January 29, 2010 by SussexmarkyMark

[stewfox]

ECM has 850's of -14C across a chunk of England at 216Z, like CC says it would be absolutely bitter, 850's tend to be a little higher in an easterly so this would chill the willies off people, particularly in the East. Still that's enough long range detail as it will change next run.

Are people dismissing UKMO T144 ?

Some seem to back to post charts from T200+ for the new second coming

A mix bag with BBC Oxford (this morning) saying wintry showers for Tuesday but with a chart at 8c

Edited January 29, 2010 by stewfox

[Essan]

The 0z GFS to be quite honest looks like a dogs dinner today and decides not to bother with the easterly, instead brings in a cold southerly, followed by high pressure centred over England.

00z GFS has a lot of snow for next week! And despite being a mild outlier, still produces very low surface temps. Looks great to me within the more reliable timeframe as Britain turns into a snowy battle ground

[Eugene]

Yeah people saying GFS 00Z OP is poor frankly havent a clue what they are on about, its cold throughout with stalling fronts next week giving the potential for some heavy snow in places, anyway aloft its one of the warmest runs at times anyway not that at the surface the same would be true

http://www.wetterzentrale.de/pics/MT8_London_ens.png - anybody downbeat about these ensembles or GEM or ECM which we are told is always the best model by the doomsters when mild then they obviously love mild weather.

[Duane S.]

UKMO not brilliant but I believe it is a fairly extreme version of what we are going to have to endure (a mild(ish) 'transition period') before we draw in a continental feed. The GFS is OK, the control run brings the lowest 850s I have ever seen showing for Dorset BTW. The ensembles are still excellent and the ECM is a lot lot better than yesterday.

We want to see the PV head as far west as possible, any further encroachment East is going to seriously test this evolution but I really don't think that won't be an issue once the shortwave exiting the states has sorted itself out. That SW is going to be a player though in how this evolves and its impact on ridging from the AH will vary from run to run for a while yet. Likewise the weakening trough to our east currently bringing in the Northerly to the UK could add to the froughtness on here as it threatens to outstay its welcome later on.

But - remember, there has rarely been an Easterly here in the UK which didn't first have to overcome such obstacles. The vast majority have failed to deliver, not just in recent years either I hasten to add. This time, the chances are higher than usual due to various signals in our favour. Timing and luck will need to play their parts too though for us to get the 'big one' but I fail to see the Atlantic winning out, we will get an Easterly. Now whether that is a feeble end of line slack Sou'Easterly or the real M'Coy is anybody's guess at this stage!!

[Eugene]

Also it seems people when predicting weather for next week don't take into account the weather we have had since mid Dec, even since the severe cold ended a few weeks ago winds have mostly been from the north,northwest,northeast and east, when was the last time we had prolonged westerlies or proper atlantic wet and windy from the southwest, on this evidence and the overwhelming support on the ensembles for cold you would have to back more cold as the form horse.

[Frosty.]

Yeah people saying GFS 00Z OP is poor frankly havent a clue what they are on about

The GFS 00z is a ludicrous run relying on a trigger low forming in the iceland area @ T+228 hours. The ecm 00z shows a more straighforward evolution to very cold and the less said about the ukmo 00z the better. There are signs now that there won't be a mild incursion pushing in from the west during next week so it should remain cold once the N'ly blows itself out.

[John London]

UKMO not brilliant but I believe it is a fairly extreme version of what we are going to have to endure (a mild(ish) 'transition period') before we draw in a continental feed. The GFS is OK, the control run brings the lowest 850s I have ever seen showing for Dorset BTW. The ensembles are still excellent and the ECM is a lot lot better than yesterday.

We want to see the PV head as far west as possible, any further encroachment East is going to seriously test this evolution but I really don't think that won't be an issue once the shortwave exiting the states has sorted itself out. That SW is going to be a player though in how this evolves and its impact on ridging from the AH will vary from run to run for a while yet. Likewise the weakening trough to our east currently bringing in the Northerly to the UK could add to the froughtness on here as it threatens to outstay its welcome later on.

But - remember, there has rarely been an Easterly here in the UK which didn't first have to overcome such obstacles. The vast majority have failed to deliver, not just in recent years either I hasten to add. This time, the chances are higher than usual due to various signals in our favour. Timing and luck will need to play their parts too though for us to get the 'big one' but I fail to see the Atlantic winning out, we will get an Easterly. Now whether that is a feeble end of line slack Sou'Easterly or the real M'Coy is anybody's guess at this stage!!

I think I'm starting to get to grips with some of this model watching mainly thanks to some of your excellent posts. Would you be so kind as to explain what you mean by "but I really don't think that won't be an issue once the shortwave exiting the states has sorted itself out" as I did find that a little confusing. Thanks in advance.

Edited January 29, 2010 by John London

[BLAST FROM THE PAST]

Posted 24 January 2010 - 23:16

Quote

I dont see any more model swapping and changing than usual. Very nice ECM, a mid Atlantic block with the potential for a northerly has been a regular feature for a while now and is now the definite trend. I never had much faith in the easterly and this sort of set-up with the mid Atlantic block has always been where I thought we would end up. Hats off to BFTP, as this is pretty much in line with his thoughts as well.

Thanks W E but you too have called for the Atlantic ridge for sometime. Re Coolclimate comment, correct the stormines seems to steer away from us but for sure we are going to see some mild temps this week as the warm front moves south, so mild [and always relatively speaking as it has been darn cold] 24-31 period but I have no issues if it turns cold by 29-30th.

Now we really see the models pick up on and show the evolution. Now in FI any quick collapse of the cold pattern with PV over Greenland IS FALSE...bin it. The block to to our W will become NW, nearly all the energy in feb will be in southern arm of the jet. Any breakthrough the block in early Feb will just produce a very cold LP on a NW to SE axis with very cold N to NE'lies to follow..so no concerns there. Any mild inroads will be to the SW.

The block will gradually move ESE to settle over Scandi bringing us E'lies as we enter half way onwards. Very interesting to see GP mention a 'sudden' update mentionng he may have to withdraw the mild call....I think he will.

BFTP

Right guys

Do we believe the models or not? On face value, run per run, this winter in particular...no. However, with ENS and all model runs put together then a pretty fair 'forecast' could be made.

I said last night expect ECM to be on board with the evolution today...and look at the ECM 00z [Yes I grabbed the controls]. It really has 'changed' and the idea of the Atlantic ridge holding and keeping everything further WEST is IMO correct. Then the ECM builds pressure to our NNW and then we see the pressure transfer mainly to our NE [indeed it covers the northern quadrant.]. That for me IS the correct signal as ECM shows and I believe UKMO will fall in line and I along with IB am not concerned with it. A cracking ECM and more to follow?

BFTP

Edited January 29, 2010 by BLAST FROM THE PAST

[weather eater]

Firstly I’m not concerned about the UKMO 144hr chart, frankly like Ian I don’t rate its performance at that range. What we have is a fascinating situation as the models try to come to grips with the synoptic evolution towards some sort of easterly, there is no doubt in my mind about the trend to that pattern. What is not yet clear is how that will affect us in in terms of cold and snow. Unfortunately we were rather spoiled the other day, by a superb and rather unusual display of model agreement for a mega cold easterly. This has lead a number of people, some of whom should know better, to believe that this evolution was in the bag and all that remained was a nice stately procession via a model inspired TARDIS, back in time to Feb 1947. Now I’m not saying that we won’t get there, the future is unwritten, but it was never going to be a ride in the Queens Bentley, it was always going to be on a roller coaster ride and its perfectly possible that just like the easterly we have just passed through, it wont be half as good as what was hinted at on that day. I seem to recall the same 1947 claims being made about the fleeting easterly we have just gone through, on the back of one set of very good runs. Model watching is easy if you remember that small details will emerge that change the evolution, it happens every run of every day, climate is dynamic, those small detail changes are inevitable, the models past the first few days are always error ridden. No matter how appealing the output looks, caution should always be applied, those that make forecasts using the models but not employing caution or common sense are just trying to appeal to an audience.

[Guest North Sea Snow Convection]

There is a fine margin of error at t120 to t144 in terms of the amount of energy that comes off the trough to the west in the atlantic and the connective ridge to the south joining up with the block to the north east.

I would expect that UKMO shows the absolute worst that could happen and has probably overdone the energy eastwards, however it is a warning that this isn't resolved yet by any means and therefore any glitzy output in FI on other modelling is only just that atm. My own humble experience shows actually that the UKMO is these situations has been the one to call the party off, and often has been right. In this situation, taking into account the background factors that might be less likely - however it is a clear demonstration that a wait and see policy carries on.

There is still a good chance that we might see high pressure close to the UK with a modest continental flow but the coldest air remaining to the east, much as GEM seems to suggest. Yes, the ensembles atm are still good - but to me that doesn't mean much at this range because there is still a long time available for that to change.

It could well all come together but more work to be done imo.

Edit: I agree with the thoughts on the stratosphere thread and the uncertainties there. That underpins the cautionary note.

Edited January 29, 2010 by North Sea Snow Convection

[D KARLSON]

Also it seems people when predicting weather for next week don't take into account the weather we have had since mid Dec, even since the severe cold ended a few weeks ago winds have mostly been from the north,northwest,northeast and east, when was the last time we had prolonged westerlies or proper atlantic wet and windy from the southwest, on this evidence and the overwhelming support on the ensembles for cold you would have to back more cold as the form horse.

I suppose its not a question of if ,but when and how the next cold outbreak returns what one must not forget is not to take the models as gospel they are inference and only suggest possible outcomes; and not that any particular model or outcome will be the victor.

Its a case of looking at them and reading between the lines or isobars ;dont forget people were worried about us getting dry south easterlies ,now the models are suggesting other outcomes non of the outcomes are actual they are only real when you get to the day forecasted itself and then you will find the charts forecasted are rarely the same as what actually occurs.

so lets have a look ,after looking at the charts over the last couple of days ,there has always been the suggestion of the British isles being on the edge of the cold pool ,with no proper push from the east ,well at least not in the short term,so the charts today merely reflect this again with UKMO 144 and this low coming in on tuesday could possibly play a part at least a small part in how the cold spell prgresses ,because there does seem to be some scope for errors here eg ;how deep and how it interacts as it moves through the north sea.

Strange thing is i prefer it this way ,with the models in flux its just more fun !!!!!!!!

[BLAST FROM THE PAST]

Where can I view this 'incredible' UKMO model at t144? I would like to see it before it changes its outlook.

BFTP

[Frosty.]

The 6z gfs building an anticyclone over the uk in the same timeframe we had a big low pulling bitterly cold air towards us on the 00z, take your pick.

Edit: RETROGRESSION followed by EPIC COLD AND SNOW

Edited January 29, 2010 by Frosty039

[KTtom]

Well, GFS at +156 is almost identical to the UKMO with a resounding NO to the potent easterly

[nick sussex]

I think its going to be a frustrating wait for people regarding the easterly, the Siberian block really can't ridge properly west until the Atlantic trough weakens and so patience is going to be needed, as we see the first attempt fails because energy spills east off the trough, then its a slow process waiting for the trough to fill and disrupt which should eventually send a shortwave se under the block.

The problem we have is that given the timeframe we're not sure what the upstream signals will be by then, will they still be condusive to allow the easterly in? Personally I don't like these slow evolutions, theres just too much time for further variables to appear. I think theres still a chance we will see some sort of continental flow but whether its a watered down se flow or a proper easterly with very cold upper air remains to be seen.

[Glacier Point]

The problem we have is that given the timeframe we're not sure what the upstream signals will be by then, will they still be condusive to allow the easterly in? Personally I don't like these slow evolutions, theres just too much time for further variables to appear. I think theres still a chance we will see some sort of continental flow but whether its a watered down se flow or a proper easterly with very cold upper air remains to be seen.

... and that variable is perhaps for the ridge over Siberia to lift out and head towards Greenland and ultimately the Canadian Arctic. There is a lot of merit to this idea, both stratospheric and tropical forcing will I think want to send us there, utilamtely with a west based -NAO.

Both ECM, GFS and GEM are starting to look a lot more realistic in their respective evolutions.

Day 11-15 mean height anomaly for GFS and GEM:

http://raleighwx.easternuswx.com/models/gfsensemble/00zENS11-15day500mbHeightAnomalyNH.gif

http://raleighwx.easternuswx.com/models/cmcensemble/00zCMCENS11-15day500mbHeightAnomalyNH.gif

and good support oin broad evolution from the 06z GFS.

Edited January 29, 2010 by Glacier Point

[TEITS]

Blimey what a messy picture.

For starters even on Tues we have uncertainity wrt to the precip moving SE. Will this fall as snow for E parts or will the colder air be further W with the precip also further W.

Beyond and the problem at the moment is these SWs prevent the block from backing W intially and because of this it allows the LP to our W to become influencial. However in saying this if the +144/+168 charts remain unchanged and appear at +72 then you find the models are overdoing these SWs and the block is further W.

Like I said earlier im not going to make any assumptions just yet of what may or may not happen. Probably best to leave that to the Met O 6-15 day forecast!

[bluearmy]

I think its going to be a frustrating wait for people regarding the easterly, the Siberian block really can't ridge properly west until the Atlantic trough weakens and so patience is going to be needed, as we see the first attempt fails because energy spills east off the trough, then its a slow process waiting for the trough to fill and disrupt which should eventually send a shortwave se under the block.

The problem we have is that given the timeframe we're not sure what the upstream signals will be by then, will they still be condusive to allow the easterly in? Personally I don't like these slow evolutions, theres just too much time for further variables to appear. I think theres still a chance we will see some sort of continental flow but whether its a watered down se flow or a proper easterly with very cold upper air remains to be seen.

Oo course, the futher south one is, maybe a 'halfway house' with the coldest uppers not making it but the flow always east of south with repeating shortwave energy sliding under the block to our east and north might be just the ticket

[weather eater]

The problem we have is that given the timeframe we're not sure what the upstream signals will be by then, will they still be condusive to allow the easterly in? Personally I don't like these slow evolutions, theres just too much time for further variables to appear. I think theres still a chance we will see some sort of continental flow but whether its a watered down se flow or a proper easterly with very cold upper air remains to be seen.

Highly likely in my book, it will fit the pattern of easterlies this winter. will Smaug get off his bed of treasure, emerge from under the lonely mountain and devastate lake town, or as has been the mode so far this winter, pop his head out for a couple of days, belch some fire and a couple of smoke rings then go back to bed.

[bluearmy]

... and that variable is perhaps for the ridge over Siberia to lift out and head towards Greenland and ultimately the Canadian Arctic. There is a lot of merit to this idea, both stratospheric and tropical forcing will I think want to send us there, utilamtely with a west based -NAO.

that was something that many individual ens runs from the 18z last night were showing via a diving shortwave. we ended up in a general w or se flow with the trough to our west. reminiscent to decembers cold spell but a bit more west based. i hope thats not where we go although the ride will be fun if not a bit shortlived compared to what many are expecting.

[Lewis]

This thread has come back down to Earth now, just goes to show, models change all the time, and looking into FI all the time and believing it, well it's suicide.

GFS and UKMO picked up on a different pattern, all it takes is the ECM to agree on the 12z, and then it's pretty much dead in the water. 06Z now shows a North Easterly even further out in FI..

[Frosty.]

I don't think we can trust the gfs as it changes so much from run to run but the good news is that it keeps finding a way to tap into the bitter cold uppers from northeast europe in FI but maybe there is no fast track solution to get there and next week is on a knife edge with milder air trying to push east but cold air fairly reluctant to budge from central and eastern areas.