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Model Output Discussion - The Run In To Christmas


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I know the ukmo doesn't go out as far as Gfs or ecm but it says alot to me when we are not waiting for it to come aboard.I know from previous years if the ukmo wasn't on board we wouldn't be getting so excited. I wonder why it hasn't be preforming as well this winter?

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I'm not going to get too drawn on the details around xmas time because there does appear to be a lot of uncertainty but the encouraging trends for me is a stronger cold pool towards Svalbard and the most significant cold pool heading into Scandi that we probably had so far this season, we also got some height rises in the Atlantic although nothing overly convincing, these can still help in sending cold air over the UK. 

 

The main trend for me however is that we look like to be heading into a period of more mild days than chilly ones with strong heights over Europe.... Infact it could get quite significantly mild for the time of year but maybe sometimes you have to go through the very mild weather to get the rewards at the end of it?

 

Despite that, I think there is some encouraging signs for cold and snow lovers but I'm not quite getting carried away by it yet. 

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Most of the GEFS go cold at some point, but lots of west based set ups still showing and a good few struggling to remove the heights over Iberia. That said though, Much better charts today but this is far from a done deal IMHO.

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I mentioned the spread in the 12z GEFS and the 2m temps for London highlights this: post-14819-0-00095500-1418843414_thumb.g

 

Very variable temps from around D8 but further uncertainty from D10. The hi-res are picking up the colder signal more than the members. For the south (IMBY) very little chance of snow for the rest of December, 10% best.

 

The D10 ensembles: post-14819-0-87581400-1418843587_thumb.p

 

I would expect plenty of chopping and changing for the next few days.

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This comment may get lost in the excitement of the ECM but can I ask, is this modelling output along side the kind of timescales we saw the cold outbreak start to be modelled with the 2010 snow events (I can't remember!) just wanting to get a grip on the situation... Don't want to get my hopes up for it all to go wrong. Thanks.

 

2010 well, the final third of November at least, saw the signal picked up some four to five days in advance, if my memory serves me right. At this stage, we need the current charts at t+192 hours onwards (the wintry charts) to verify by less than t-120 or thereabouts in order to give us all a better clue as to what should happen to be the weather type experienced over the festive period. It is all a question of consistent features showing up over differing timeframes. Only when the Christmas period is within the reliable timeframe (judged best by looking at ensembles spreads) can we be sure that your patch may have a chance of the white stuff. Too far away to call on the specifics but the NH picture is looking fine for a pattern change to colder snow-producing synoptics spreading South over time.  :good: Kind of like, one Swallow does maketh a Summer, rather like one Run does not make a Winter SNOWMAGGEDON.  :shok:

Edited by gottolovethisweather
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If we stick to trends and themes rather than specifics shown in the model, it is clear all are suggesting a much colder evolution from Christmas Eve onwards, however, the Christmas period still remains beyond reliable timeframe, so we still need to be cautious on calling such an evolution.

 

There are very encouraging signs though for a colder shot by Christmas thanks to projected events on the other side of the atlantic - an amplified flow is being shown and it is this which will allow for mid atlantic heights to build northwards with cold air advection down to our shores and the promise of warm air advection western side of Greenland.

 

GFS does tend to perform better when it comes to forecasting pattern changes on the other side of the atlantic, and I do rate it over ECM when it comes to heights building over Greenland, ECM tends to perform much better when we have heights to our north east and east - so not surprised to see ECM playing around with shortwaves to our NW.

 

 

If the models continue with the theme of the last 24 hours over the next 72 hours i.e. by Saturday then the odds of a cold evolution by Christmas occuring will be almost nailed, alas we have a number of days still to go through.

 

The Met Office remain ominously silent - but to be expected until such an evolution is within reliable timeframe they won't mention it.. for snow cold lovers the weekend could make many happy..

Edited by damianslaw
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For the south (IMBY) very little chance of snow for the rest of December, 10% best.

 

I would expect plenty of chopping and changing for the next few days.

 

If you expect plenty of 'chopping and changing' in the next few days, how you say theirs very little chance of snow in the next 13 days?

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I mentioned the spread in the 12z GEFS and the 2m temps for London highlights this: attachicon.gifgraphe6_1000_306_141___Londres (17).gif

 

Very variable temps from around D8 but further uncertainty from D10. The hi-res are picking up the colder signal more than the members. For the south (IMBY) very little chance of snow for the rest of December, 10% best.

 

The D10 ensembles: attachicon.gifMeteociel_-_Panel_GEFS 4.png

 

I would expect plenty of chopping and changing for the next few days.

I am not too concerned about the chance of snow as that is exactly the kind of detail we simply can't predict at that time scale. At 10-14 days the trend is excellent and that's the key here.

 

I seem to remember some wise words from days gone by on here: "get the cold in first and let the rest happen" :)

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short wave drama?ECM1-216.GIF?17-0

 

Shortwaves/Surface Lows/Depressions will always show up in the Atlantic as it truly is a rain-maker. :drinks: I would patiently wait until further consistency shows up deeper into the runs and watch for a blocked Atlantic. In truth, that is what I believe is on the way. When the winds veer to our North and maybe eventually the North-East, that's when the true fun and games begin.  :cold:

Edited by gottolovethisweather
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Just a point not really take a still frame in isolation.  T216 ECM is a beauty to develop on from there, overall the model pattern is really good today...let's see how we develop from here.  Apart from transient 18-32 hours mild is NOT in control

 

 

BFTP

Of course it is worth remembering that with the exception of Saturday, every day up to Christmas eve will see temperatures above the seasonal average, in fact for the southern half of the UK that will mean maxima in double figures. Only Christmas eve and beyond will we see temperatures at or below normal.

As for the ECM, lets hope for a cleaner solution and avoid all that shannon entropy

Edited by Captain shortwave
correcting terrible spelling
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If you expect plenty of 'chopping and changing' in the next few days, how you say theirs very little chance of snow in the next 13 days?

 

For people further north there are some good GEFS charts but the evolutions are different. eg Leeds has a 35% chance (snow chances are listed on the graph) of snow on one of the upcoming days:

 

post-14819-0-63104200-1418844282_thumb.g

 

So even with some changes there is still a better chance for snow. However of the 22 members only 2 at the most on a given day show snow south of the M4. So the south are going to have to get lucky for the right chart to verify for snow IMO.

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If we stick to trends and themes rather than specifics shown in the model, it is clear all are suggesting a much colder evolution from Christmas Eve onwards, however, the Christmas period still remains beyond reliable timeframe, so we still need to be cautious on calling such an evolution.

 

There are very encouraging signs though for a colder shot by Christmas thanks to projected events on the other side of the atlantic - an amplified flow is being shown and it is this which will allow for mid atlantic heights to build northwards with cold air advection down to our shores and the promise of warm air advection western side of Greenland.

 

GFS does tend to perform better when it comes to forecasting pattern changes on the other side of the atlantic, and I do rate it over ECM when it comes to heights building over Greenland, ECM tends to perform much better when we have heights to our north east and east - so not surprised to see ECM playing around with shortwaves to our NW.

 

 

If the models continue with the theme of the last 24 hours over the next 72 hours i.e. by Saturday then the odds of a cold evolution by Christmas occuring will be almost nailed, alas we have a number of days still to go through.

 

The Met Office remain ominously silent - but to be expected until such an evolution is within reliable timeframe they won't mention it.. for snow cold lovers the weekend could make many happy..

I've just posted in the ramp thread that Ian F mentioned the Christmas Period on the local forecast, and made the point that there is unlikely to be anything wintry over Christmas, just alternating between mild & cold between now and the big day, with the run up to Christmas being mild.

 

But he was only talking about of local though.....

Edited by SteveB
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Yes the ECM may not be as good as the gfs. But think about this time last year when we was all getting excited about a watered down northerly on Boxing Day. Think if we had been offered these charts last year we would of snapped is hand off. So let's all not get too hung up and enjoy the ride. And if it does all Pete tong we still got jan feb March to go.

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Mmm, the ECM op has really thrown a spanner in the works. I keep thinking about the infamous Matt Hugo tweet last night and lo and behold, the ECM sticks to rapid cyclogenesis over our shores in the 8 to 10 day period. Is that two or three op runs on the trot now? All I know is that when the ECM op stays with a particular solution that differs to the other models, these other models generally backtrack eventually and come in to line with the ECM.

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Mmm, the ECM op has really thrown a spanner in the works. I keep thinking about the infamous Matt Hugo tweet last night and lo and behold, the ECM sticks to rapid cyclogenesis over our shores in the 8 to 10 day period. Is that two or three op runs on the trot now? All I know is that when the ECM op stays with a particular solution that differs to the other models, these other models generally backtrack eventually and come in to line with the ECM.

sorry but how's it thrown a spanner in the works.? We're still talking 8 days away from any pattern change long way to go yet.
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Mmm, the ECM op has really thrown a spanner in the works. I keep thinking about the infamous Matt Hugo tweet last night and lo and behold, the ECM sticks to rapid cyclogenesis over our shores in the 8 to 10 day period. Is that two or three op runs on the trot now? All I know is that when the ECM op stays with a particular solution that differs to the other models, these other models generally backtrack eventually and come in to line with the ECM.

The real problems with the ECM occur past T168hrs and because of that I'd read less into it. Indeed if you look at a few of its operationals from the beginning of the week you'll see its been very volatile.

 

I used to be one of its biggest fans however whilst its still top upto T144hrs after that point I take less notice of it, if it pulls out a solution at T144hrs then I'd get worried but at this point I think we need to just see its solution as an outlier.

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The real problems with the ECM occur past T168hrs and because of that I'd read less into it. Indeed if you look at a few of its operationals from the beginning of the week you'll see its been very volatile.

I used to be one of its biggest fans however whilst its still top upto T144hrs after that point I take less notice of it, if it pulls out a solution at T144hrs then I'd get worried but at this point I think we need to just see its solution as an outlier.

Hi Nick, like I said though, it is the second 12z op on the trot to insist on the low in the atlantic splitting the high and heading straight for us. The ECM has a knack of spotting a trend even at 8 to 10 days that the other models don't even sniff. I fear this is one of those occasions unfortunately. The met seem to be agreeing with this scenario as well. Edited by blizzard81
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