Winter Model Discussion - Cold Hunting - 20th Dec

[Gavin Hannah]

Hopefully this weekend will be the last above avg spell. I'm going north snowboarding between Xmas and early jan...!

[nick sussex]

Changes upstream at last given tonight discussions at NOAA.

Possible plus PNA

East coast troughing

More typical negative AO pattern

Theres hope folks that we might see some changes as we head into January.

The full discussions can be found here:

http://www.cpc.ncep....day/fxus06.html

I should elaborate for newer members, east coast USA troughing with a more amplified upstream pattern in the USA generally at least gives you a chance of some northerlies, with a ridge to the nw, even if you don't get a full on block you at least have a better chance of some colder snaps with snow.

Much of the winter season in the USA has seen a negative PNA and this is why people on USA forums in the ne have been moaning like us at the lack of wintry weather.

A more typical negative AO or as NOAA like to call it a canonical type neg AO normally sees that east USA troughing.

The ECM at 240hrs does look like its trending that way especially as the PV is expected to pull away from our north.

So just a bit of good news but we wait to see this translated into concrete outputs across the board that don't implode nearer the time!

Edited December 21, 2012 by nick sussex

[Frosty.]

Changes upstream at last given tonight discussions at NOAA.

Possible plus PNA

East coast troughing

More typical negative AO pattern

Theres hope folks that we might see some changes as we head into January.

The full discussions can be found here:

http://www.cpc.ncep....day/fxus06.html

Thank goodness for that nick...13c in southern areas tomorrow will feel more like march than december.

Edited December 21, 2012 by Frosty039

[bluearmy]

Changes upstream at last given tonight discussions at NOAA.

Possible plus PNA

East coast troughing

More typical negative AO pattern

Theres hope folks that we might see some changes as we head into January.

The full discussions can be found here:

http://www.cpc.ncep....day/fxus06.html

And 'potentially important stratospheric changes'

Edited December 21, 2012 by bluearmy

[nick sussex]

And 'potentially important stratospheric changes'

Yes it was good to see that, I'm sure Chiono will also be happy.

[Zenarcher]

Summary of the models this evening using the GFS, ECM, UKMO, GEM, NOGAPS, JMA.

This weekend - Now that we are in the reliable time where all the models agree on we can look at this weekends unsettled weather,

First of all the wind it will be very windy across most of the UK on Saturday morning where gales are likely,

Saturday night into Sunday morning for the far North of Scotland is where it will get stormy average wind speeds there around 55mph,

The rain is the real main concern for the weekend where we will see long lasting rain continue over a widespread area for 2 days,

Saturday

Sunday

Christmas Eve - All the models show a weak low now covering much of the UK around 985mb, winds will be lighter but rain during the morning will still be a problem for England,

Christmas Day - ECM snowfall maps still restricts any snowfall to the Scottish highlands while the GFS is a bit more kinder and gives us wintry weather over Northern parts of the UK so the models still uncertain where and if we will get any wintry weather for now.

Certainly doesn't look to be a mild Christmas though as the GFS still gives us low minimum temperatures,

Boxing Day - Some large changes in the models begin here they still show high pressure to the West of Greenland and low pressure to the East but it's the Atlantic lows that are causing uncertainty, most seem to show a low around just to the West of the UK. As for the UK it does still look cold with a NW wind.

144 hours and beyond - GFS keeps the Atlantic in charge but does end up building heights up over Greenland, ECM also shows Atlantic driven weather although the lows look weaker they would still bring in wet and windy weather, towards the end of the run it breaks PV up, NOGAPS gives us a very wet and windy outlook and JMA also shows Atlantic lows move in.

Overall - Don't have much time tonight to write up anything in better detail but the models show a very wet weekend and stormy at times in the far North. For Christmas time still unsure if we will get any wintry weather but the models do show cold temperatures. After Christmas the models show the Atlantic to move in and bring more wet and windy weather to finish off the year but the ECM and GFS both break up PV and build pressure over the Northern Hemisphere.

[swfc]

Ill say it now, anyone writing winter off now, is like writing the summer off in the middle of June. Yes winter hasn't been great so far, but we still have the whole of January, February and March left, I say March because April can often see some potent snow falls too, one of which about 5-6 years ago, I witnessed thundersnow one morning from a potent snow shower in Lincolnshire. Odds even stack up for Easter to have more of the magical white stuff than at christmas time. I think we are going to see some proper cold from mid January on into February. We even saw a spine chilling low of -16c here in Cambridgeshire during the cold snap in February earlier on this year from the 'deadly cold' snap in Europe. Now had that huge high pressure have been placed 500 miles further west, we would have seen copious amounts of snowfall like Ukraine, Romania and much of the Adriatic. Have faith people, we will see the cold, we just need the right pattern to set itself up. We have 2 solid months yet at least folks.

hi there.Do you have any reasoning behind your thoughts or is it just a hunch?The uk could go threw winter totally zonal but id be guessing if i said that .all the "fi strat warming and nao values"aside id be interested to know why you come to this???thanks

[etched Chaos]

hi there.Do you have any reasoning behind your thoughts or is it just a hunch?The uk could go threw winter totally zonal but id be guessing if i said that .all the "fi strat warming and nao values"aside id be interested to know why you come to this???thanks

It's just common sense, with two months left, writing off winter now is a ridiculous notion.

[LomondSnowstorm]

hi there.Do you have any reasoning behind your thoughts or is it just a hunch?The uk could go threw winter totally zonal but id be guessing if i said that .all the "fi strat warming and nao values"aside id be interested to know why you come to this???thanks

It also couldn't be a winter that was mild and zonal in its entirety even if the rest turned out that way (which it rarely does anyway):

The AO has been negative pretty much all winter, the NAO very slightly negative but there are good reasons other than just FI output to suggest that it will start to really tank in the New Year, while the strat warming had been both flagged up at the start of the winter and also fairly consistently modelled so far with a likely warming date around the 7th/8th. No guarantees of deep cold and snow as the rather nice looking anomaly chart above demonstrates, but by definition you can't get a mild zonal spell and you're very likely to see below average (as the start of December has been, albeit not massively) temperatures with a significantly negative NAO and a decent blocking signal. Snow is of course a different matter but most of us usually see at least one decent snowfall even in a poor winter so there's no reason to suspect that this won't be the case again.

[bluearmy]

Really very little of interest for at least 10 days. on northern hills or possibly lower down over scotland, there may be something from a 'runner'. Looks like we have low heights over greenland and high ones over iberia. (In general). Tenuous signs that more solid northern blocking establishing in a fortnights time. Lets hope the iberian ridge decides to retrogress into a greeny height rise. We should now begin to see the back end of gfs runs reflecting any immediate trop response to strat warming. At least that mitigate against the likely boredom from the runs prior to this.

[BLAST FROM THE PAST]

Thank goodness for that nick...13c in southern areas tomorrow will feel more like march than december.

Don't panic Frosty, look at this for Xmas Day 1986 [wonderful 16c in Swansea and had a great Christmas lunchtime beer in The Plough and Harrow], and we know what followed that.........should be some interesting chart watching over Christmas period. as I think there'll be something 'brewing' shall we say.

BFTP

Edited December 21, 2012 by BLAST FROM THE PAST

[-uksnow-]

Well at t84 the 18z makes less of the blasted Russian block than the 12z

18z.....

12z

Small differences, but every little helps.

Edited December 21, 2012 by -eded-

[Panayiotis]

The only good at 84hrs on the 18z is that the high to the west of Greenland is stronger than it was on the 12z, however everything else has downgraded IMO.

Edited December 21, 2012 by Panayiotis

[swfc]

It also couldn't be a winter that was mild and zonal in its entirety even if the rest turned out that way (which it rarely does anyway):

The AO has been negative pretty much all winter, the NAO very slightly negative but there are good reasons other than just FI output to suggest that it will start to really tank in the New Year, while the strat warming had been both flagged up at the start of the winter and also fairly consistently modelled so far with a likely warming date around the 7th/8th. No guarantees of deep cold and snow as the rather nice looking anomaly chart above demonstrates, but by definition you can't get a mild zonal spell and you're very likely to see below average (as the start of December has been, albeit not massively) temperatures with a significantly negative NAO and a decent blocking signal. Snow is of course a different matter but most of us usually see at least one decent snowfall even in a poor winter so there's no reason to suspect that this won't be the case again.

Thanks for your reply.As i thought anything is possible but nothing probable!

[LomondSnowstorm]

Thanks for your reply.As i thought anything is possible but nothing probable!

Absolutely, well other than rain, rain is always probable at some point in a winter

[swfc]

It's just common sense, with two months left, writing off winter now is a ridiculous notion.

??? Iwasnt writing off winter.My point is saying the weather will probably turn much colder in january is impossible to back up!look whats happened over the last six weeks or so after three "so called severe spells"imploded at short range.Whatever background signals they may be it means jack up till they varify.

[Panayiotis]

Oops talked to soon, lovely northerly on boxing day.

[nick sussex]

Although the models agree on the overall pattern upto 144hrs they still disagree between runs on the detail, so here on the GFS 18hrs run although the colder air takes longer to head south when it does theres a better chance for some snow in the north.

I thought zonal patterns were easy to forecast!

[cyclonic happiness]

??? Iwasnt writing off winter.My point is saying the weather will probably turn much colder in january is impossible to back up!look whats happened over the last six weeks or so after three "so called severe spells"imploded at short range.Whatever background signals they may be it means jack up till they varify.

I was always lead to believe from my relatives and teachers and such that, the coldest time of the year is in late January and early February, so don't worry :-)

[Zakos]

While the bigger picture remains the same for the next 144 hours, the flow is continuing to be moddled differently.

This really isnt that much of a change, simply a change in the tilt of the jet stream results in a more favourable airflow, giving quite a decent cold shot.

[nick sussex]

I certainly wouldn't read too much into the detail here as the models seem to be in a bit of a muddle with these shortwaves forming.

It's not really your typical limpet PV to the north set up, so anyone especially in the north whose looking to know whether they might see some snow around Xmas/ Boxing Day, we best get back to you on that!

[BLAST FROM THE PAST]

Definite signs here of a shift southwards of the jetstream from the models, a theme that as we head into New year we'll see getting firmed up imo. That'll be step one.

BFTP

I certainly wouldn't read too much into the detail here as the models seem to be in a bit of a muddle with these shortwaves forming.

It's not really your typical limpet PV to the north set up, so anyone especially in the north whose looking to know whether they might see some snow around Xmas/ Boxing Day, we best get back to you on that!

And probably not til t24 Nick!!

BFTP

Edited December 21, 2012 by BLAST FROM THE PAST

[swfc]

I was always lead to believe from my relatives and teachers and such that, the coldest time of the year is in late January and early February, so don't worry :-)

For the love of god im not worrying!!!Ive been following weather patterns for fourty years.My point was regarding peoples comments on future weather in jan ete without being able to back it up

[peterf]

it'll snow,William Hill has just been on the phone and he's bricking it lol.

[nick sussex]

Definite signs here of a shift southwards of the jetstream, a theme that as we head into New year we'll see getting firmed up. That'll be step one.

BFTP

And probably not til t24 Nick!!

BFTP

Lol! I tend to agree with you there.

Historically PV to the north models overestimate southwards extent of jet and then take this north which they began to do till today where its back south again!

Of course we don't have the uniform PV to the north with this split which does add a different aspect to things.