General Model Output Discussion

[Cumulonimbus Tower]

Well, the ECM looks like it fancies a trip down the undercutting route this evening as opposed to squashing the block from the North West as was this mornings output. A very good sign IMHO. Tomorrow morning may well show tha a quick return to something colder is very much on the cards. I for one hope so anyway. I'm sick of these +1 temps already. Time to turn the heating off....

[MR EXTREMES]

I apologise aswell. Im having a bad day as some might be able to tell!

ECM at +144 is showing why I thought the UKMO had potential. You can see the LP system going under the block with both models being very similiar at this timeframe. However look at +168!

http://www.wetterzen...cs/Recm1681.gif

If the models continue with this trend then in a few days time I shall share my little secret. Like I said earlier some will be amazed and most probably laugh!

i wont laugh,

but what i will say this output was always a possibilty with a strong build from the east north east,

and classic from old skool cold developments.

thats a exciting chart with ukmo with similar idear.

Edited January 12, 2010 by badboy657

[Nick F]

ECM shows a rather extensive 1065mb Siberian high pushing out west by t+168, a pretty formidable block.

By t+192, the Atlantic trough develops an increasingly negative tilt and undercuts the block, we need this undercut of upper energy to prevent the high sinking. This undercutting by the Atlantic troughing has quite a bit of support from the 12z GFS ensembles too.

Ok we don't get the easterly in the end but that's one of many possible paths, but the building blocks are appearing by t+168.

[PB22]

ECM FI shows the problem that the high to the east has to deal with, an active Atlantic and jet stream, with low heights towards Greenland and Iceland. Plus there's no real deep cold on offer:

http://www.wzkarten.de/pics/Recm1921.html

http://www.wzkarten.de/pics/Recm2161.html

[john w]

Andy i think you are probably on the ball there.

People interested in weather often like extremes or (off average) I think because we have been so spoilt with the extremes (relative to the last few winters) the now less cold spell (but by comparison to previous winters by no means mild) and the way we dont want to see the mild atlantic make too much of an incursion means that looking ahead has come down a bit. Excitement ahead perhaps is less as we are on a downer.

I did wonder about the pressures linking up towards t184 but wasnt sure about it. Mainly as I always assume ridges wont make it to scandi. I was worried actually that if the siberian high became too cold and strong it would extend SW across europe and that low in biscay may have limited options....and sit there and gradually move North up france and then over germany...skirting a strong euro high.

[MR EXTREMES]

a little while ago gp had idears of scandi linking with iceland high is this possible still?

or would the scandi high at t168 be robust enough to hold firm?

it looks mega to me.

[nick sussex]

ECM FI shows the problem that the high to the east has to deal with, an active Atlantic and jet stream, with low heights towards Greenland and Iceland. Plus there's no real deep cold on offer:

http://www.wzkarten.de/pics/Recm1921.html

http://www.wzkarten.de/pics/Recm2161.html

Yes but this is evolving and low heights to the NW aren't a problem, many cold easterlies have occured with PV to the north west. The surface flow will still be cold which is a whole lot better than mild Atlantic dross. The key thing is that the models agree on the cut off low, if the Atlantic trough becomes negatively tilted this will likely send shortwaves under the advancing block. I'd expect to see some very cold ECM ensemble members this evening.

[MR EXTREMES]

ECM FI shows the problem that the high to the east has to deal with, an active Atlantic and jet stream, with low heights towards Greenland and Iceland. Plus there's no real deep cold on offer:

http://www.wzkarten....s/Recm1921.html

http://www.wzkarten....s/Recm2161.html

i must admit a strong jet and low heights around greenland is 9times out of 10 a big blow for good cold.

but is that low to progessive it maybe that its over cooking that low it may not even track in that direction,

also in regards to the jet its been very south this could continue.

[gottolovethisweather]

Hello all,

I don't really know which section I should post my query in so I've plumped fo this one.

Anyway, concerning the more immediate period say, next 24-36 hours isn't it somewhat unusual for a low pressure system (the one heading towards Ireland as we speak) taking the route indicated by the following link http://www.metoffice.gov.uk/weather/uk/surface_pressure.html truly bizzare Can someone, confirm how often such a thing could happen and why is taking that route back to Greenland and maybe even back to the US. My personal take on it is that block is currently too strong?

Confused and intrigued

STORMBOY

[cooling climate]

I think what the models are also showing is that the Siberian high is primed and ready to

show its hand and if we were to get some help from a MMW (major midwinter warming) -AO

then the true beast from the east could be just a couple of weeks down the line.

I am still of the opinion that a real freeze is still post 23rd as I said yesterday although cold to rather

cold weather is not out of the question.

[bluearmy]

nice to see the p/v stretching and ultimatly splitting in ecm fi. plus trough disruption in the atlantic and one has to ask what will happen if the atlantic isnt as potent as it looks to be over the next 10 days. the siberian high seems to head slowly in our direction as the p/v splits and drops its main segment into siberia. plenty to watch and with each run we swing to and fro between an atlantic and continental influence. this year, my money is on the east as the southern arm is forecast to become the main driver again.

[weather eater]

I apologise aswell. Im having a bad day as some might be able to tell!

ECM at +144 is showing why I thought the UKMO had potential. You can see the LP system going under the block with both models being very similiar at this timeframe. However look at +168!

http://www.wetterzentrale.de/pics/Recm1681.gif

If the models continue with this trend then in a few days time I shall share my little secret. Like I said earlier some will be amazed and most probably laugh!

Certainly an interesting run from the ECM Dave, but rather like recent GFS runs which have also hinted at an easterly set up, the ECM is fairly quick to push the high away further east, personally I don't think its wise to read to much into output past 144hrs and all that we are seeing is pretty standard model runs toying with various post mid term evolutions. One consistent is this huge Scandi/Russian Block sitting tantalisingly close.

[Thundery wintry showers]

ECM FI shows the problem that the high to the east has to deal with, an active Atlantic and jet stream, with low heights towards Greenland and Iceland. Plus there's no real deep cold on offer:

http://www.wzkarten.de/pics/Recm1921.html

http://www.wzkarten.de/pics/Recm2161.html

I agree with the early to mid part of the sentence- the low pressure to the W and NW and the active Atlantic are a real barrier to that high ridging west from Scandinavia. Undercutting and a slowdown of the northern arm of the jet will be needed to give us a direct easterly. Note that the easterly outbreaks of February 1991 and November 1993 were both preceded by a lot of low pressure and SW'lys out to the NW.

But regarding the "no real deep cold" it depends on how deep the cold has to be to meet that criteria. If 850hPa temperatures are around -8C or below, and 1000-500mbar thicknesses are around 522 dam or below, I would generally expect sunshine and snow showers to be the result from an easterly incursion. If either of those are not met, stable weather cloud and/or a marginal wintry mix of precipitation become more likely. The airmass that the ECMWF sends towards us looks like it would easily satisfy both of those criteria- we don't need a "11-14 January 1987" in order to bring heavy snow showers across eastern parts.

But, of course, all of this will be moot if the cold air never quite reaches us.

[cold snap]

Yes but this is evolving and low heights to the NW aren't a problem, many cold easterlies have occured with PV to the north west. The surface flow will still be cold which is a whole lot better than mild Atlantic dross. The key thing is that the models agree on the cut off low, if the Atlantic trough becomes negatively tilted this will likely send shortwaves under the advancing block. I'd expect to see some very cold ECM ensemble members this evening.

Nick i love it when you like this mate.brilliant.I so hope your right Nick

GFS,UKMO.ECM model output are all singing the same story at the moment.no cold snap next week .

However Met office text says its still on.

The question is Are all the models barking up the wrong tree ?

Or is Nick and Met office text is correct?

Also Irish Met are also thinking we are going back to cold

[TEITS]

Certainly an interesting run from the ECM Dave, but rather like recent GFS runs which have also hinted at an easterly set up, the ECM is fairly quick to push the high away further east, personally I don't think its wise to read to much into output past 144hrs and all that we are seeing is pretty standard model runs toying with various post mid term evolutions. One consistent is this huge Scandi/Russian Block sitting tantalisingly close.

Certainly need more runs although im quiet happy with the trend at +168. I do also agree with Nick S that whilst the GEFS ensembels are promising I would ideally prefer to see this in the operationals.

What we have to remember is we can have an E,ly with the PV in its current projected position. However ideally I would prefer this to be further W to allow the Siberian HP to fully flex its muscles. Thankfully this sign that im seeing is helping me choose between the Siberian HP & the Atlantic.

[john w]

Stormboy I think its excellent you have picked up on that and entirely relevant to this discussion as in the end it is showing on the model and thus is model output.

The reason is...and I may be off the mark a bit here. The jet is so far south it cannot really guide the development of the lows. The blocks are so strong also due to temperature that the mild and less dense air (hence lower pressure) cannot make inroads. The clockwise circulation of the high is also helping to steer this low both North and then West. usually with the jet over of near the Uk...the associated area of divergence aloft would help to steer the low in the usual N/NW direction.

I think that is the main reason...but more experienced will elaborate...is there any vorticity related reasons due to the cockwise spin off the high hitting the low and intensifying the cyclone and westwards component?????

[phil nw.]

ECM FI shows the problem that the high to the east has to deal with, an active Atlantic and jet stream, with low heights towards Greenland and Iceland. Plus there's no real deep cold on offer:

http://www.wzkarten....s/Recm1921.html

http://www.wzkarten....s/Recm2161.html

I agree Paul.

As much as i prefer an Easterly rather than average murk the strength of that vortex will not enable sustained cold from the block.

If those low heights remain there we may well have stalemate for a week or more.

[Frosty.]

Hi Karl I'm not sure you're odds of 70/30 are much of a knife-edge, a blunt one maybe. In truth there's always a scatter on the ensembles, some colder some milder, I do feel however that the overwhelming trend is to keep the block to our east. It could well be that this will change, but I think there is little support for this from the models at this point of time.

Hi weather eater,

Yes the knife does need sharpening but there are more positive signs that there could be a realistic cold trend emerging in the models over the coming few days, the cold block remains intact and close to the east and while it's still there we have a chance at least, good signs from the gfs control run and the ecm 12z. The milder spell for this weekend is unavoidable though but hopefully it won't last long into next week and won't be particularly mild either.

[cooling climate]

Yes but this is evolving and low heights to the NW aren't a problem, many cold easterlies have occured with PV to the north west. The surface flow will still be cold which is a whole lot better than mild Atlantic dross. The key thing is that the models agree on the cut off low, if the Atlantic trough becomes negatively tilted this will likely send shortwaves under the advancing block. I'd expect to see some very cold ECM ensemble members this evening.

Steve Murr wrote a good post about this last winter in that the problem with many winters in the last couple of

decades we could not get pressure to fall around Iberia and over the Med.

Last winter we saw the first signs of this happening for a long time and this winter they are like buses (slight exaggeration).

I see on the ECM t240 northern hemisphere charts that the AO is negative again with a split vortex taking place again.

Although in FI very encouraging signs perhaps.

[nick sussex]

Nick i love it when you like this mate.brilliant.I so hope your right Nick

GFS,UKMO.ECM model output are all singing the same story at the moment.no cold snap next week .

However Met office text says its still on.

The question is Are all the models barking up the wrong tree ?

Or is Nick and Met office text is correct?

Also Irish Met are also thinking we are going back to cold

Thanks

Well IMO the trend is gathering now and the crucial cut off low appears at 120hrs, thats the important first step, we still don't know the exact set up of the Atlantic trough, on previous NOAA discussions they expected the PV to lock in over the polar region which is okay, we want the trough negatively tilted ie running at nw/se or ar worst north south.

NOAA sing the praises of the ECM this evening which is positive news for downstream in Europe.

THE DETERMINISTIC ECMWF HAS SHOWN STRONG VERIFICATION WITH SURFACE

PRESSURES ACROSS THE UNITED STATES...SOUTHERN CANADA...AND

NORTHERN MEXICO OVER THE PAST FOUR MONTHS...EDGING OUT THE

GFS...GEFS MEAN...AND EC MEAN FOR DAYS 3 THROUGH 6...WITH A

SIMILAR SCORE SHOWN AT DAY 7 TO THE GEFS MEAN. FOR TODAYS

FORECAST...THE 00Z/12 ECMWF...GEFS MEAN...AND EC MEAN CLUSTER WELL

DURING THE SECOND HALF OF THE PERIOD...

...THE ECMWF IS HARD TO BEAT OVER THE LONG

HAUL BEYOND DAY 4...AND UNLESS THAT MODEL OR ITS MEAN TREND

STRONGLY IN THE DIRECTION OF THE OTHER CLUSTER OF GUIDANCE...WILL

BE RELUCTANT TO DEVIATE MUCH FROM ITS SCENARIO.

Edited January 12, 2010 by nick sussex

[weather eater]

Certainly need more runs although im quiet happy with the trend at +168. I do also agree with Nick S that whilst the GEFS ensembels are promising I would ideally prefer to see this in the operationals.

What we have to remember is we can have an E,ly with the PV in its current projected position. However ideally I would prefer this to be further W to allow the Siberian HP to fully flex its muscles. Thankfully this sign that im seeing is helping me choose between the Siberian HP & the Atlantic.

Hi Dave as someone who doesn't pay the ensembles that much attention I too would prefer to see more operational support. Still it’s keeping interest up, and a return of the Atlantic is not a foregone conclusion, although a spell of somewhat milder weather is. To be honest a thaw would be no bad thing for us, as our bins have not been collected for 5 weeks and the logs we ordered before Christmas have still not been delivered.

[gottolovethisweather]

Stormboy I think its excellent you have picked up on that and entirely relevant to this discussion as in the end it is showing on the model and thus is model output.

The reason is...and I may be off the mark a bit here. The jet is so far south it cannot really guide the development of the lows. The blocks are so strong also due to temperature that the mild and less dense air (hence lower pressure) cannot make inroads. The clockwise circulation of the high is also helping to steer this low both North and then West. usually with the jet over of near the Uk...the associated area of divergence aloft would help to steer the low in the usual N/NW direction.

I think that is the main reason...but more experienced will elaborate...is there any vorticity related reasons due to the cockwise spin off the high hitting the low and intensifying the cyclone and westwards component?????

Thanks very much John, clearly put to someone who needs it in plain english.

Of course, this is clearly a reason why many folk would never post in here, fear of coming across as stupid, whether its relevant and of course, possibly potentially an embarassing episode.

Thanks for saving my blushes.

I do truly believe with all the media coverage, continuous snow cover over many parts of the u.k. currently, the u.k. has introduced many many newbies onto the art of weather discussion and all its theories etc.

Again, many Thanks.

STORMBOY

[tinybill]

Thanks

Well IMO the trend is gathering now and the crucial cut off low appears at 120hrs, thats the important first step, we still don't know the exact set up of the Atlantic trough, on previous NOAA discussions they expected the PV to lock in over the polar region which is okay, we want the trough negatively tilted ie running at nw/se or ar worst north south.

NOAA sing the praises of the ECM this evening which is positive news for downstream in Europe.

THE DETERMINISTIC ECMWF HAS SHOWN STRONG VERIFICATION WITH SURFACE

PRESSURES ACROSS THE UNITED STATES...SOUTHERN CANADA...AND

NORTHERN MEXICO OVER THE PAST FOUR MONTHS...EDGING OUT THE

GFS...GEFS MEAN...AND EC MEAN FOR DAYS 3 THROUGH 6...WITH A

SIMILAR SCORE SHOWN AT DAY 7 TO THE GEFS MEAN. FOR TODAYS

FORECAST...THE 00Z/12 ECMWF...GEFS MEAN...AND EC MEAN CLUSTER WELL

DURING THE SECOND HALF OF THE PERIOD...

...THE ECMWF IS HARD TO BEAT OVER THE LONG

HAUL BEYOND DAY 4...AND UNLESS THAT MODEL OR ITS MEAN TREND

STRONGLY IN THE DIRECTION OF THE OTHER CLUSTER OF GUIDANCE...WILL

BE RELUCTANT TO DEVIATE MUCH FROM ITS SCENARIO.

great reading on here to-night are the models barking up the wrong tree well i hope nick and co are right i think they might be with a fax chart like this nothing stand much chance going any were

[rich1]

A lot of people are keen to write off any chace of colder weather coming back next week but that might end up being a tad premature

ECM is thinking about it IMO...

doesnt really get all that mild over the weekend, average for many at best seemingly then...who knows?

cant see a flip back to the standard pattern this winter at this time. it could happen but my unscientific view is that this is one of those winters...

[phil nw.]

A lot of people are keen to write off any chace of colder weather coming back next week but that might end up being a tad premature

ECM is thinking about it IMO...

doesnt really get all that mild over the weekend, average for many at best seemingly then...who knows?

cant see a flip back to the standard pattern this winter at this time. it could happen but my unscientific view is that this is one of those winters...

Even though the Uk is at the edge of the block to the East it wouldn`t require much of change to get the colder upper air Westwards towards us

ECM T216hrs

Shows the really cold air on our doorstep in quite a slack flow.