Model Output Discussion

[snowmadchrisuk]

Funny how some keep on referring to downgrades and yet my summary on Saturday hasn't changed today. Always said E areas especially E Anglia/SE are most likely to see the most frequent snow showers from Wed-Fri and that outlook hasn't changed. Maybe some didn't properly read this because they were too busy complaining about being biased towards the SE. The only difference is the showers might not move as far inland as I currenrly thought. However at no stage did locations such as Bristol ever look favoured because with a convective E/NE,ly they never will be!!

Beyond and to be honest at this stage its a complete and utter mess looking at the ensembles. Some of these suggest turning milder with SW,lys, others suggest heavy snowfalls with LP tracking along the channel, some even suggest an E,ly via a Scandi HP!

Lets be realistic for some locations this week will only bring dry, sunny, cold conditions before turning slightly less cold during the weekend. Beyond and it could be possible that some regions turn much milder. However at this stage I wouldn't come to any assumptions because surely the past 7 days of model output has taught us that. The HP moving to Greenland looks very likely but that is about the only reliable pattern beyond +144.

In some respects I wish the mild SW,lys had occured due to the constant moaning on this thread!!

Agree totally , and when people talk about downgrades most are just looking at precipitation charts and basing things on that. I imagine the next 48 hours precipitation charts will be different on the 12z to the 6z . I'm Still in Weston-Super-Mare until tomorrow and the Snow has reached here and is settling . This is a seaside resort and you would expect the Snow to melt. Mark my words the next 2 weeks are going to throw up a few surprises .

[Optimus Prime]

The UKMO has just taken over the ECM in accuracy for the last few days. Maybe the one to watch.

[Lewis]

The UKMO has just taken over the ECM in accuracy for the last few days. Maybe the one to watch.

Agreed, already the UKMO is showing a fair few features/troughs.

I'm looking forward to the 12z GFS, i think it'll be a super upgrade, for then only the ECM to backtrack and show what the GFS was showing this morning, thus causing the model output thread into a meltdown of negativeness if thats a word lol.

[SussexmarkyMark]

I think the use of terms such as 'upgrades' and 'downgrades' is unhelpful on a model discussion thread. It appears to me that models just change, which means some area will 'upgrade' and some will 'downgrade' depending on how the models change. There have of course been many changes in the models over the last ten days viz-a-viz a cold spell and things have changed further over the last 48 hours, particularly with regard to a full-blown long- lasting easterly. If you look back at last week, many were posting charts for later this week showing an easterly from western Russia to mid-Atlantic, with a double HP over Scandinavia and Greenland, which obviously raises expectations. This may of course still happen, but does not seem that likely.

I think some of the more experienced (and dare I say older) contributors should be more aware than there are many younger posters on here (not me unfortunately) that might read more into the post than you are meaning and therefore when a lot of FI charts showing deep cold at +240 are posted, you have to accept a certain degree of disppointment when these disappear, as there is excitement when the post is originally made. (And no TEITS, I am not aiming this comment specifically at you.)

And for what it's worth, I think TEITS' summary for this week looks pretty realistic to me.

[Optimus Prime]

Here's some definition to the models were view on a daily basis so hopefully help with peoples judgement;

Global Forecast System (GFS): The Global Forecast System (GFS) - The GFS is a global spectral model used primarily for aviation weather forecasts. The GFS provides guidance out to 384 hours at 00, 06, 12 and 18UTC.

European Center for Medium range Weather Forecasting (ECMWF): Contour plots from the European Center for Medium range Weather Forecasting (ECMWF) forecast model. This model runs to 10 days (7 days public) and provides data at 24 hour intervals for sea level pressure, 850 mb winds and temperatures and 500 mb heights. These plots are generated once a day at approx 8:45 PM EST.

RGEM: 00z Initialization | 12z Initialization Short-range regional forecast model from CMC Environment Canada. 48 hour forecast updated twice daily (00 UTC and 12 UTC).

GGEM: 00z Initialization | 12z Initialization Medium-range global forecast model from CMC Environment Canada. 240 hour forecast updated twice daily (00 UTC and 12 UTC).

UKMET: The UKMET has a resolution of 75 kilometers, which is better than the GFS resolution of 150 km. The model also gives forecasts for the entire northern hemisphere like the GFS. The UKMET is run twice a day

http://www.emc.ncep.noaa.gov/gmb/STATS/html/acz6.html

That chart shows the dfaily accuracy rate for each model. Top Northern Hemisphere, bottom Southern. UKMET is currently top with ECMWF 2nd with GFS well third.

[chionomaniac]

Yes the pre Xmas cold spell had a similar signal for a western based negative NAO although Chinio mentioned that the current MMW might lead to a further pulse of negative zonal mean winds which could back the pattern further west. Lets hope the models edge the pattern eastwards with time and we don't end up seeing that low stuck over the UK.

Sometimes it can be a real battle in trying to work out how the negative mean zonal winds will translate themselves onto the troposphere. However it is worth looking at the MJO phase and seeing if there is any compatability with the lower stratospheric profiles currently.

We see that the MJO is bordering around phase 8 and set to stall here before perhaps returning into phase 7.

Now the 500hPa analogue for phase 8 is as follows:

We see three main troughs with a west based -NAO.

So now to the lower stratospheric profile at 100 hPa for T+144. Does it show some kind of consistency with the MJO profile?

And to my mind there is a lot of compatability between the two charts suggesting that the tropospheric drivers are in line with the lower stratospheric drivers. The main difference that I can see is that the west based -NAO may not be quite as pronounced. This can give us a big idea of where the models will be heading in a weeks time or so with the proviso that we should allow some margin of error into this.

[Lewis]

HP much further south (even further south again) the rate the GFS is going at, it will have all of the cold air in france, with the entire U.K missing out (even the S.E)

Don't get the rope yet though folks, ecm is important.

[Interitus]

I think the use of terms such as 'upgrades' and 'downgrades' is unhelpful on a model discussion thread. It appears to me that models just change, which means some area will 'upgrade' and some will 'downgrade' depending on how the models change. There have of course been many changes in the models over the last ten days viz-a-viz a cold spell and things have changed further over the last 48 hours, particularly with regard to a full-blown long- lasting easterly. If you look back at last week, many were posting charts for later this week showing an easterly from western Russia to mid-Atlantic, with a double HP over Scandinavia and Greenland, which obviously raises expectations. This may of course still happen, but does not seem that likely.

I think some of the more experienced (and dare I say older) contributors should be more aware than there are many younger posters on here (not me unfortunately) that might read more into the post than you are meaning and therefore when a lot of FI charts showing deep cold at +240 are posted, you have to accept a certain degree of disppointment when these disappear, as there is excitement when the post is originally made. (And no TEITS, I am not aiming this comment specifically at you.)

And for what it's worth, I think TEITS' summary for this week looks pretty realistic to me.

What was interesting was the uniformity and agreement amongst models which I think led people to expect a full on easterly. Maybe a deficiency of data for initialising the models has meant they have changed closer to the time with the high pressure having more of an influence to the northwest.

[TEITS]

HP much further south (even further south again) the rate the GFS is going at, it will have all of the cold air in france, with the entire U.K missing out (even the S.E)

The difference between the 06Z/12Z is around 30miles!!

Makes no difference to the weather on the surface.

[Lewis]

The difference between the 06Z/12Z is around 30miles!!

Makes no difference to the weather on the surface.

Sorry TEITS, although the difference is only 30miles if it's a continous trend, come the time frame all them extra miles add up. And make a subsequent difference.

I thought you especially would know that.

Edited February 8, 2010 by Storm Force Lewis

[TEITS]

Sorry TEITS, although the difference is only 30miles if it's a continous trend, come the time frame all them extra miles add up. And make a subsequent difference.

I thought you especially would know that.

How do we know its a continous trend the 18Z might have the HP slightly further N?

Lets wait for the ECM/UKMO and also the 18Z before suggesting this is a trend!

[Neilsouth]

It's only a 30mile distance if that ! , hardly even worth worrying about... The east well the south east is still at risk from the most snow or cold , gfs/ukmo/ecm still the same in that regard

[Lewis]

The difference between the 06Z/12Z is around 30miles!!

Makes no difference to the weather on the surface.

There you go;

[Neilsouth]

There you go;

More intensive pooling across the south east , still the same direction of flow from the north east. Looks ok still

Edited February 8, 2010 by neilsouth

[Lewis]

More intensive pooling across the south east , still the same direction of flow from the north east. Looks ok still

Did you forget to notice how close the HP becomes to the E/SE?

And TEITS, it is becoming a trend, the past 36 hours have seen the GFS constantly shift the HP much further South.

It's not just one run now is it?

[yamkin]

The UKMO has just taken over the ECM in accuracy for the last few days. Maybe the one to watch.

Over a week ago, GFS was showing Easterlies. ECM started to show Easterlies then backed down. UKMO never showed Easterlies and stuck to it's guns. This seemed confusing as the MetO's LRF mentioned cold in the East with wintry showers. As TEITS mentioned several times that the MetO were using their human skills which have proved correct where the models fell into place accordingly. The MetO must have known the models were having difficulties, so I commend them for their human input.

[kold weather]

GFS keeps with the idea of the high being probably just a little bit too far south, generally when the GFS carries this idea through to 72hrs it tends to be right I've found in the past.

As the block transfers westward just about anything is possible it seems, anything from a very quick transfer back to mild to a channel low set-up is possible

[TEITS]

Did you forget to notice how close the HP becomes to the E/SE?

And TEITS, it is becoming a trend, the past 36 hours have seen the GFS constantly shift the HP much further South.

It's not just one run now is it?

Ironic because the 12Z suggests more convection for my location than the 06Z.

The problem as I see it is the SE/E Anglia always look more favoured but many chose to ignore this because they were too busy complaining about SE bias.

Sorry if I sound harsh but I always tell it as it is!

[kold weather]

I remember in the December 2005 easterly the models constantly progged the HP to build too close by then probably just 48hrs out they had a big change ariound and showed a far stronger easterly airflow for at least the far eastern parts of the UK, so things can change even now.

Anyway GFS shows a little upper feature swinging through Ea/SE on Saturday but other thenthat HP generally a little too close still...

[Polar Continental]

Yes I can see why you'd say that. Peoples expectations have gone into overdrive, to be honest I was thinking twice about including my less than optimistic slant on the western based negative NAO in my previous post in case that was met with more hysteria!

I thought i'd get that out of the way and end with a positive in that its likely to stay cold for at least the next week. To be honest Dave I dread to think what will happen next winter if its an average or mild affair, Dec and Jan have led some people into forgetting the previous mild dross affairs of so many years.

We have been extremely fortunate with the winter so far but some members wouldn't be happy unless it was another 1963!

Well judging by some of the posts on here I think I would stop posting on this thread should we have a mild winter!

Quickly going back to some of the moanning on here. I do wish members would use their local knowledge of their weather. For instance I have a rough idea of what a NW/N/NE/E/SE,ly brings to Peterborough. Thankfully the NAE will be coming into range very shortly so we might have a better idea with regards to snowfall.

Afternoon all,

Just to back-up what Nick S and Dave the eye have been trying to get across to some model posters on here complaining about the current synoptics.

Here is a decade of winters past around this time when cold lovers did have something to grumble about.

Most of the charts below represent our recent winters, except 2009, which was when things changed.

Note the attempted northerly on a few, they all ended up 24 hour weak events and toppled

2010

[Lewis]

Ironic because the 12Z suggests more convection for my location than the 06Z.

The problem as I see it is the SE/E Anglia always look more favoured but many chose to ignore this because they were too busy complaining about SE bias.

Sorry if I sound harsh but I always tell it as it is!

It has nothing to do with SE/EA bias.

What a lot of members on here are failing to do is accept the GFS is showing a different evolution. It was clear the HP was going to kill things off for me, i'm more interested in what happens in the next 2 days and then after friday.

You have to accept that the 12z run has the HP much further South. There's not point in members for example you, NeilSouth and then there was another person that had their post removed biting when someone says it's a downgrade etc. It is, and btw regarding convection if that's what you call it, i see everything south of you.

People really need to chill out and stop biting, i'm discussing the model output. Some member are just clutching to a lost cause, learn when to let go, otherwise it will get the better of you.

Im sure, infact i'm waiting for someone to back me up on this, if not the threads all the same, and i feel like the only one other than Nick Sussex etc thats keeping a straight/level head.

The gfs continues to push the HP further South full stop, and if it continues to do so, come thursday/friday all of us will be under it.

Lets see what the ECM shows.

Edited February 8, 2010 by Storm Force Lewis

[Methuselah]

Guys??? Please keep teddies within prams??? Thanks!

[mountain shadow]

Incidentally, the longer the high pressure does take to move North West the longer the cold spell continues, snow or no snow.

I've noticed the tendency in the models to go for the west based -NAO too quickly especially in the low res part of the GFS runs.

The move north westards will be a slow progress hopefully allowing time for the trough to drop more favourably into Scandi. A west based -NAO isn't bad for everyone.

[Matty M]

Very disappointing 12z in the short term from GFS and UKM

Where does it all go wrong?

UKM at 42 hours looks good, all we needed was a trough to dig west and we would of got something.

As it is for my location, a few days ago we were definately getting the -10c sub pool not its about 100/150 miles to the south.

[kold weather]

Its not further south Lewis and in fact the high is at a slightly better angle on the 12z then the 06z, however the end result will stil lbe the same as the upper fetch isn't enough and the air probably will be overall a little too stable after Thursday for most.

Also past 144hrs there isn't enough of a trigger to really drag down any decent northerrly either so may get stuck in a broadly anti-cyclonic flow till it totally transfers into a west based feature...remaining cold though as long as it hangs nearby.