Model Output Discussion - 12th December Onward

[phil nw.]

Judging by the overwhelming response to the ECM rolling out everyone is not loving the latest run....

The most entertainment I found was following this shortwave from now round to about 144-168 hrs, and watching the evolution to another low NW of UK.

Am wondering about these charts, Theta E or Theta W as they are known, think you have posted a couple Phil, how best to interpret these?

No mate i havent used these--not sure of their usefullness for the casual model watcher,although i have stumbled on them.

I believe Theta E stands for Equivalent Potential Temperature.ie,the temperature of a parcel of air if it was condensed.That chart shows those temps. at 850hPa,i think.

Maybe one of the Forecast team can explain better.

[nick sussex]

As for the Bartlett.....Ive done my research as you well know.....If that jet stays north the Azores High stays South and COULD well join with an EasternEuro high becoming a seudo Bartlett.....A bit more realistic than Svalbard heights.......

I don't think I was being nasty.

I have no problem with people wanting to see a Bartlett, as i said in my other post everyones entitled to their preferred weather type. Anyway I think it's best we move on from this, I certainly don't want to drag the festive spirit out of this thread.

Lets agree to disagree and forget about the last 30 mins.

Edited December 16, 2011 by phil n.warks.
removed sniping from the copied post

[Robbie Garrett]

Theres not much chance at the moment of a proper Greenland block and any cold will more likely have to come from the jet tilting nw/se as it has done recently, the area I would keep an eye on is to the ne with some pressure rises to help force lower heights back into Europe.

Given the strat profile things could have been alot worse and so really the first half of December has broken with past tradition, somehow we've managed a more favourable jet angle and generally once you get that background signal which wants to reduce the influence of the Azores high then theres always a chance for some PM incursions.

Theres plenty of winter left and so lots of time for things to develop more favourably.

Similar to what we had in 2009 I guess? easterlies (not northerlies) - and of course I agree, but we are blasting through winter like we blasted through 2011, and things wont get going or develop till at least mid January?

[ChartViewer]

I don't think I was being nasty.

I have no problem with people wanting to see a Bartlett, as i said in my other post everyones entitled to their preferred weather type. Anyway I think it's best we move on from this, I certainly don't want to drag the festive spirit out of this thread.

Lets agree to disagree and forget about the last 30 mins.

Agreed Nick will be interesting how New Year turns out...i think SM calls it butting

Edited December 16, 2011 by ChartViewer

[Nick L]

No mate i havent used these--not sure of their usefullness for the casual model watcher,although i have stumbled on them.

I believe Theta E stands for Equivalent Potential Temperature.ie,the temperature of a parcel of air if it was condensed.That chart shows those temps. at 850hPa,i think.

Maybe one of the Forecast team can explain better.

I gave an explanation based on my understanding above

Theta E is equivalent potential temperature of an air parcel. This is the temperature the air parcel would have if it released all of its latent heat (i.e. completely condensing), and then descended adiabatically* to the 1000hpa level. Although I know what it is, I'm not really sure why they are being posted rather than normal temperatures or the 850s, it is usually related to the stability of the atmosphere I believe when you take into account it's rate of change with respect to height.

*Adiabatic descent is where the air parcel descends without any energy exchange with its surroundings, it will contract due to the increase in pressure surrounding it and cause a temperature rise.

[Paul]

I call it a pain in the backside. Any chance we can just stick to the models and lose the petty squabbling please

[Robbie Garrett]

Similar to this I am guessing Nick? Or do you have a better example?

[January Snowstorm]

Dreadful runs tonight, not even a toppler in sight over the next 10 days

Christmas is looking very green at the moment though we just have time on our side.

Hopefully things will change for the better by tomorrow and the one grain of hope we have is that this month has been colder than anyone thought possible

[pyrotech]

• asked this earlier but noone seemed able to answer
  
• can anyone answer now
  

• 
  

Posted Today, 13:52

Can some one comment at the end of the run on current GFS , obviously deep in Fi but what are 850mb temps of +12 doing over Canada?

I can not remember temps like that for the time of year, can someone with more knowledge enlighten me on the chance of that happening, how or what could cause it and if its normal. Is it a data failure by the GFS or feasable.

I just really did not expect to see such high 850mb temps over the UK let alone Canada ( further North)

Anyone able to comment on this? Or is it a stupid question?

[nick sussex]

Agreed Nick will be interesting how New Year turns out...i think SM calls it butting

Lol!

In terms of the New Year I'm not making any firm predictions!

I do feel strangely optimistic though and I haven't even had anything to drink! The overall NH pattern really shouldn't have delivered anything wintry but the UK has done an unusual thing with clutching victory from the jaws of defeat instead of the other way round.

I've often said you can get something interesting inspite of poorish teleconnections, just as you can get nothing out of good ones, they're not an exact science and its often difficult to decide which signal is holding the Royal Flush!

[phil nw.]

After a cold weekend then we revert to a flatter,zonal pattern with the Azores high becoming a major player next week.

As it ridges north it will bring some milder conditions for mid week but with the jet. meandering around the UK this will likely bring some colder air into the North at times.

http://www.wetterzen...cs/Recm1441.gif

http://www.wetterzen...s/Rtavn1441.png

http://www.wetterzen...cs/Rukm1441.gif

Certainly not a good pattern for a those looking for deep cold with that High so close to our South West.

Some buckling of the jet would allow chances of at least temporary cold shots further south which is the best we can hope until we see those low heights over the Arctic weaken.

I gave an explanation based on my understanding above

Yes thanks Nick.

As i said in my earlier post i have never used them in my model analysis but have come across them before.

Edited December 16, 2011 by phil n.warks.

[phil nw.]

• asked this earlier but noone seemed able to answer
  
• can anyone answer now
  

• 
  

Posted Today, 13:52

Can some one comment at the end of the run on current GFS , obviously deep in Fi but what are 850mb temps of +12 doing over Canada?

I can not remember temps like that for the time of year, can someone with more knowledge enlighten me on the chance of that happening, how or what could cause it and if its normal. Is it a data failure by the GFS or feasable.

I just really did not expect to see such high 850mb temps over the UK let alone Canada ( further North)

Anyone able to comment on this? Or is it a stupid question?

I have just seen your post and there is some+12c upper air in the N.States,almost to the Canadian border here,

http://176.31.229.22...nh-1-324.png?12

If it was on the 006z run-i can`t comment as i didn`t see that--however for Canada-yes very unusual-would have to be a long fetch draw from way down south and this has come from High pressure over the Pacific seaboard and deep troughing over the Eastern side of N.America.

It does look a very temporary warm patch as you would expect at this time of year.

Edited December 16, 2011 by phil n.warks.

[BLAST FROM THE PAST]

Temps even on Tues are progged to be 7c down here, only 4c on Mon so the mild isn't going to be that mild...not yet anyway. Re horrible charts, look it wasn't ever likely to be cold for Christmas but also there is no sign or real signal for a Bartlett to develop and entrench it self...a pattern change, if it occurs it will be in New Year ie early jan and it will be a very different set up to what we've had. Basically what I'm suggesting is that if the pattern changes it will be 'very' different to now and I have to say the 240 ECM is very interesting hinting at heights to far NE. For now mixed bag continues.

BFTP

[OldMetMan]

Others might not agree, but I think today's GFS and ECM show some interesting potentialities. First off, apologies if anyone has already discussed it, but has anyone noticed the intense HP forecast for central Asia in the next few days? So what you might ask. For one thing, bit unusual to see HP > 1060mb this early, for another, I have seen a tendency in the past for the HP to build westwards from that location, or to re-develop to the west.

We still have cold air feeding SE into Europe. Beyond 5 days, I think the GFS loses the plot somewhat, but the ECM looks more like it, a mobile pattern but the jet alignment NW-SE - likely to continue to introduce cold air here and into Europe at intervals. So I think we need to watch out for rising pressure over NW Russia/Scandinavia within the next 10 days or so as the cold deepens.

The GFS clearly has been defaulting to southwesterlies beyond a certain point in time for a while now so I think the UKMet and ECM will most likely pick up on any HP build up to the E quite early, if it is to happen.

[Grimsby Snow Lover]

A very interesting read there Old met man, I know most on here would love to see some weather from the northeast this winter. This would also fit in with those metoffice charts that were posted the other day. When would you expect to see any FI eyecandy following the influence of the Asian high?

[BLAST FROM THE PAST]

Others might not agree, but I think today's GFS and ECM show some interesting potentialities. First off, apologies if anyone has already discussed it, but has anyone noticed the intense HP forecast for central Asia in the next few days? So what you might ask. For one thing, bit unusual to see HP > 1060mb this early, for another, I have seen a tendency in the past for the HP to build westwards from that location, or to re-develop to the west.

We still have cold air feeding SE into Europe. Beyond 5 days, I think the GFS loses the plot somewhat, but the ECM looks more like it, a mobile pattern but the jet alignment NW-SE - likely to continue to introduce cold air here and into Europe at intervals. So I think we need to watch out for rising pressure over NW Russia/Scandinavia within the next 10 days or so as the cold deepens.

The GFS clearly has been defaulting to southwesterlies beyond a certain point in time for a while now so I think the UKMet and ECM will most likely pick up on any HP build up to the E quite early, if it is to happen.

Yes, am watching and I believe something to watch over next 10-14 days. Chart watching could become very interesting come Christmas week.

As an aside, ECM and BOM suggest Boxing Day stormy, very windy / wet / snowy for NI and Scotland and High levels to NW. A period to keep and eye on with hints that a pronounced NW/SE axis wants to develop.

BFTP

Edited December 16, 2011 by BLAST FROM THE PAST

[OldMetMan]

A very interesting read there Old met man, I know most on here would love to see some weather from the northeast this winter. This would also fit in with those metoffice charts that were posted the other day. When would you expect to see any FI eyecandy following the influence of the Asian high?

Thanks for that, hard to say, as I mentioned, most likely the ECM would pick it up soonest, perhaps within the next few days.

[pyrotech]

I have just seen your post and there is some+12c upper air in the N.States,almost to the Canadian border here,

http://176.31.229.22...nh-1-324.png?12

If it was on the 006z run-i can`t comment as i didn`t see that--however for Canada-yes very unusual-would have to be a long fetch draw from way down south and this has come from High pressure over the Pacific seaboard and deep troughing over the Eastern side of N.America.

It does look a very temporary warm patch as you would expect at this time of year.

Thanks for taking the time to answer

This is actual image Top left , perhaps im reading it wrong

[bluearmy]

the trend today is to take the jet back south again after a short northern sojourn next week. a mainly west-east flow with a hint of north rather than south looks like the mean. cant see a tilt far enough se to encourage height rises to the northeast within the next couple of weeks. it really looks to me as though we can expect more of the same. that stubborn cold trough eastern canada continues to spit energy into the atlantic where it meets the warmer uppers coming around the azores high. until we see the p/v in eastern canada lose strength or migrate elsewhere, i dont see too much changing.

certainly doesnt seem like a mild outlook, given what the pattern has delivered so far this month. the models have been determined to change the flow sw/ne. looks like it is likely to carry on the same way its been.

Thanks for taking the time to answer

This is actual image Top left , perhaps im reading it wrong

something is wrong with that map pyro. the 12c isotherm is in the deep south of the states at that timescale. well spotted.

[BLAST FROM THE PAST]

Looks like GFS wants some of it too......lively Boxing Day weather that is.

BFTP

[Liam J]

GFS seems to have shunted things further south on the 18z? Depressions taking a more direct hit over the UK instead of more emphasis on ridging from the south/south west as previous runs were showing.

Edited December 16, 2011 by Liam J

[OldMetMan]

Yes, am watching and I believe something to watch over next 10-14 days. Chart watching could become very interesting come Christmas week.

As an aside, ECM and BOM suggest Boxing Day stormy, very windy / wet / snowy for NI and Scotland and High levels to NW. A period to keep and eye on with hints that a pronounced NW/SE axis wants to develop.

BFTP

Indeed. Another unusual thing I've noticed is the presence of high thickness values in mid-Atlantic, >564dm (or "red air" as I have always called it!). The low that zipped up the Channel yesterday was essentially sub-tropical in origin if you track it back - strange thing to happen in December. The implications of this high thickness could be an increased chance of very intense LP over the Atlantic, with a very strong baroclinic zone and jet. Or if the upper pattern amplifies, a strong mid-Atlantic upper ridge and corresponding deep downstream trough over us.

[Uncle_Barty]

Dreadful runs tonight, not even a toppler in sight over the next 10 days

Christmas is looking very green at the moment though we just have time on our side.

Hopefully things will change for the better by tomorrow and the one grain of hope we have is that this month has been colder than anyone thought possible

It is only a 'dreadful' run if you want cold weather. Personally (and especially at this time of year) I prefer lighter heating bills and no disruption to transport or sports events, so I am pleased with the output at the moment! Now if we can keep it like this till March.... I'm sure we won't though, of course.

ECM is the milder run, tending towards a southwesterly airflow, GFS 18z keeps things more westerly or perhaps a touch more north. In any case it is looking like settling down at times for the south, rather more unsettled in the north.

It does strike me this winter that if you don't like the output, go away for a few days and when you come back it will probably look a lot better!!

[phil nw.]

Thanks for taking the time to answer

This is actual image Top left , perhaps im reading it wrong

Yes that looks like it.

[pyrotech]

Yes that looks like it.

Thanks to you and bluearmy for replying, so it is unusual to see on 850mb but its not quite what it looks like on there, still trying to fully understand your answer from earlier, in weather terms. Its great that i can still come on here and learn something new with the models, and i thought i had a good understanding of them.

Cheers both