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01-11-2018, 09:56   #1
Rebelbrowser
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9th Annual Boards White Christmas Thread

Its that day again, 1 November, when, with Halloween over us, thoughts turn to the next big event on the horizon - yup Christmas is coming....

This is the 9th installment of this particular thread - if you don't believe me the first from 2010 is still available at - https://www.boards.ie/vbulletin/show...php?p=68686802 but in fact I found White Christmas threads dating back to 2004 (when there was a White Christmas for many!) at https://www.boards.ie/vbulletin/show....php?p=2209623 . Some familiar names posted in that thread too I note!

As usual this thread is solely concerned with the weather over the Christmas period, primarily 24 & 25 December and, in particular, is concerned with whether it might snow on Christmas day itself.

The last white Christmas (as in lying snow) for most of us was 2010 of course. However I don't think there was any Christmas day snowfall that year. The last actual white Christmas in my part of the country (1cm of falling snow I think?) was 2004.

The CFS is probably the best source at this stage for making any sort of guess as to what weather we might have on the big day. At present it shows the following:-

Uppers



Generally



Day time lows



Thickness



Subject to correction that's a very cold, settled day with a biting northerly wind and max temps of 2c to 4c or so. Uppers are of about -6c or -7 (typically you need -8c uppers for snow). There seems to be some shower activity in the NW in particular. So at the moment its all in all a very seasonal Christmas day with a definite chance of snow for some. Not a bad way to start the thread.....

Lest you think this is ridiculously premature (and I appreciate it probably is), a few websites have had a White Christmas page on the go for a while now. theweatheroutlook.co.uk are always the most enthusiastic and run a forecast from 1 September each year. They have updated theirs today actually and are saying (admittedly on a UK centric site):-

Update 9 makes no change to the percentage chance of a White Christmas. The possibility of snow is considered higher than normal in both the north and south of the UK.
The primary reasons for this are:
1) The QBO is switching back to a westerly phase. A westerly phase is associated with an increased chance of milder winters in the UK.
2) We are close to a solar minimum.
3) Since the Sudden Stratospheric Warming (SSW) in February there has been an ongoing signal for high pressure blocks to have more influence on the UK's weather than normal. In the late winter and early spring northern blocking led to widespread snow as the Beast from the East made its presence felt. That was followed by one of the warmest (it could turn out to be the warmest once all of the data has been collated) summers on record in the UK due to the persistence of anticyclonic conditions. As we head through the meteorological autumn the elevated signal for high pressure still appears to be present.
4) Some of the latest seasonal model updates are pointing towards a colder than average winter.
5) Medium range models are suggesting quite an unsettled pattern during early November. Cold conditions in the early part of winter are considered more likely if November is cool and wet.
Chance of snow on Christmas Day
North of Yorkshire / Lancashire:25%
South of Yorkshire / Lancashire: 15%
The Computer says
• It's expected to be too mild for snow in the south
• It's expected to be too mild for snow in Wales
• It's expected to be too mild for snow in the Midlands
• It's expected to be too mild for snow in the north
• It's expected to be too mild for snow in Scotland
• It's expected to be too mild for snow in Northern Ireland
• It's expected to be too mild for snow in the Republic of Ireland
• It's expected to be too mild for snow in the Netherlands
Forecast issued 01/11/2018 07:49:30


Which is actually all very promising really.

I will update this every 5 days or so in November but will update it more frequently in December, especially if things are looking in any way promising. Usually by 10 December or so we know that our goose (or turkey?) is cooked however.

Until then, here's a seasonal pic to whet the appetite courtesy of theweatheroutlook.co.uk…

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01-11-2018, 10:00   #2
Artane2002
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The uppers required for snow depends on the wind direction (source of air mass really, because each air mass has different characteristics). Northwesterlies require lower uppers for snow than easterlies do.
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20-11-2018, 15:44   #3
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Meant to update this regularly. Damn work commitments...

Suffice it to say its still looking good on the CFS for a cold run in to Xmas. This tallies with other LRFs like MTC's on this forum.

On phone so not sure if the following link will work. See https://expert-images.images-weather...22312_1900.gif

Will do proper post shortly

Last edited by Rebelbrowser; 20-11-2018 at 17:02.
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21-11-2018, 13:47   #4
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Looks cold for the next few weeks on the majority of runs but a few mild ones come and go.

I feel this Winter will be "different" to most others.

Will Christmas Day?

No real Atlantic activity presently but by end of November the next stage will go a long way to determining if the Atlantic breaks the block and brings regular Winter rain and wind.
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21-11-2018, 17:57   #5
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I like this thread. Glad to see it here again

I just hope we don't get a repeat of Christmas day 2009. We had a very cold surafce layer, but due to warmer air aloft we ended up with freezing rain. Horrible.
If Carlsberg did a white christmas, it would start snowing very heavily on Christmas eve night for nine hours straight, with every bit of it sticking, so that when we woke up in the morning to look outside there would be 8 inches of snow on the ground.
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22-11-2018, 07:44   #6
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We are in Belfast for Christmas, at quite a high elevation....... here's hoping for a little drop of snow, the kids would be thrilled...... .never mind me!
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22-11-2018, 14:45   #7
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Just to quickly update this. CFS still showing a (shortlived) cold outbreak around Christmas Eve. MT seems to hint at similar in his outlook this morning. See below from today's CFS. That's probably cold enough for some Irish sea streamers but not a whole lot and shortlived.



Otherwise the Net Weather Christmas forecast from yesterday stated

"...

We're still with the CFS model for now, and we're still trend hunting too. And that trend is on the way to becoming our friend, with quite a few hints that colder weather could be a regular visitor as we move toward the Xmas period.

Christmas weather forecast:- Tonight's chart shows a bit of eastern cold coming with us on Christmas day, which is indicative of some of the patterns being shown quite frequently. Could we be on Beast from the East watch as we move toward the big day?

As usual, Santa has been updated with the lates snow risks, not too much changing from the last update at this point, as the positive start to this years forecast continues".



The TWO equivalent from today states:-


"...Update 12 makes no change to the chance of a White Christmas in both the south and north. The possibility of snow is considered notably higher than normal.

The primary reasons for this are:

1) Medium range models continue to show colder and blocked periods, although there is a lot of uncertainty about how things will develop.

2) Since the Sudden Stratospheric Warming (SSW) in February there has been an ongoing signal for high pressure blocks to have more influence on the UK's weather than normal. In the late winter and early spring northern blocking led to widespread snow as the Beast from the East made its presence felt. That was followed by one of the warmest (it could turn out to be the warmest once all of the data has been collated) summers on record in the UK due to the persistence of anticyclonic conditions. As we head through the meteorological autumn the elevated signal for high pressure still appears to be present.

3) Some of the latest seasonal model updates are pointing towards a colder than average winter.

Chance of snow on Christmas Day

The Computer says
It's expected to be too mild for snow in the south
Snow is expected in Wales 
Snow is expected in the Midlands 
Cold conditions in the north are expected, marginal for rain or snow.
Snow is expected in Scotland 
Cold conditions in Northern Ireland are expected, marginal for rain or snow.
Cold conditions in the Republic of Ireland are expected, marginal for rain or snow.
Cold but dry conditions are expected in the Netherlands
..."

All in all, pretty promising for those of us hoping for a white one. Its been 14 years without a White Christmas (2010 doesn't count as it was lying snow) so we are due one.
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27-11-2018, 02:20   #8
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One factor which makes me think the chances are a little better this winter would be that an energy peak is likely to occur around 22-23 Dec which raises the chances that the wind direction on the 24th and 25th will swing around to a northwest or northerly direction even if it's mild and rainy a few days earlier. Realistically, the chances of a white Christmas for most parts of Ireland from one year to the next are about 10% at best rising to perhaps 20% in the higher northwest hilly regions, but maybe this year as high as 30%. That's not bad.
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27-11-2018, 04:04   #9
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Quote:
Originally Posted by M.T. Cranium View Post
One factor which makes me think the chances are a little better this winter would be that an energy peak is likely to occur around 22-23 Dec which raises the chances that the wind direction on the 24th and 25th will swing around to a northwest or northerly direction even if it's mild and rainy a few days earlier. Realistically, the chances of a white Christmas for most parts of Ireland from one year to the next are about 10% at best rising to perhaps 20% in the higher northwest hilly regions, but maybe this year as high as 30%. That's not bad.
(the northern max event is the most reliable storm correlative in my research model too, just tuck this factoid away, the next full moon almost simultaneous with the northern max as is always the case with late December full moons, so 21-23 December a possible stormy period, if the upper level pattern conducive to Ireland being in a storm track).

Is this the potential white storm! Or is the mere thought of it going to guarantee the weather God's will inflict us with mild south westerlies until April : -)

Mmmmmm... Maybe not the outcome I was hoping but perhaps a sting in its tail. (Good weather God's, good :-) )
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28-11-2018, 12:21   #10
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Just to update this and right now the CFS (which we are still looking to) is predicting lots of atlantic based weather between now and the big day (just 650 hours away!). Still a few weeks before the more reliable (ahem..) models like GFS come into view.

For the big day itself the CFS has the mother and father of low systems sitting over Iceland pumping cold, but modified by the time it hits us, air all the way from north east Canada to us. It would be cold and wet, an awful day really. Some higher slopes might see some white stuff but nothing for most of us.

See:-

Northern Hemisphere



Ireland and the Former European Republic of Brittania



Upper Temps
https://expert-images.images-weather...22500_2800.gif


Theweatheroutlook.com have also updated their forecast as follows:-

"...
-Update 13 reduces the chance of a White Christmas in both the south and north. Despite that the possibility of snow is still considered notably higher than normal.

The primary reasons for this are:

1) Medium range are pointing towards more unsettled weather during early December but in the longer term there is a sign of a more blocked and colder periods.

2) Since the Sudden Stratospheric Warming (SSW) in February there has been an ongoing signal for high pressure blocks to have more influence on the UK's weather than normal. In the late winter and early spring northern blocking led to widespread snow as the Beast from the East made its presence felt. That was followed by one of the warmest (it could turn out to be the warmest once all of the data has been collated) summers on record in the UK due to the persistence of anticyclonic conditions. As we head through the meteorological autumn the elevated signal for high pressure still appears to be present.

3) Some of the latest seasonal model updates are pointing towards a colder than average winter.

The Computer says
It's expected to be too mild for snow in the south
It's expected to be too mild for snow in Wales
Cold but dry conditions are expected in the Midlands
It's expected to be too mild for snow in the north
It's expected to be too mild for snow in Scotland
It's expected to be too mild for snow in Northern Ireland
It's expected to be too mild for snow in the Republic of Ireland
Cold but dry conditions are expected in the Netherlands

Forecast issued 28/11/2018 08:59:43...."


Obviously still very much all to play for.
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28-11-2018, 15:21   #11
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Just one last quick point about the CFS and other indicators for 4 week's time. 4 weeks ago the same indicators were showing ice and snow right about now with a blocked Atlantic. So don't dispair - it would be an understatement to say nothing is written in stone!
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28-11-2018, 16:45   #12
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Eight years since my last white Christmas, same for most I would assume
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30-11-2018, 10:29   #13
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Very seasonal (but not a White Christmas) outlook from the CFS this morning.

Shows a cold plunge from the North / North East in days leading up to Christmas with Christmas day itself cold, dry and frosty ("cool and crisp and even...."). I'd take that any day....

Rain to snow event in the SE on 22nd Dec



A cold push from the north on Christmas eve with possible NE Streamers off the Irish sea (these are upper air temps)



A cold, dry Christmas day (min sea level +2m temps)



Nice
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04-12-2018, 09:30   #14
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Not a whole lot new to report here. MTC is hinting at a stormy Christmas Eve in his outlook this morning. Otherwise the CFS has, for a few days now, suggested a vist from the Azores High in time for the big day, meaning a cold Xmas Eve would give way to a mild (but dry at least) Xmas day.

Still about a week away from any of the major models modelling as far as 25/12 so 'tis all guesswork still really.
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04-12-2018, 09:34   #15
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Quote:
Originally Posted by Rebelbrowser View Post
Otherwise the CFS has, for a few days now, suggested a vist from the Azores High in time for the big day, meaning a cold Xmas Eve would give way to a mild (but dry at least) Xmas day.
In lieu of snow I will gladly accept a dry Xmas day. Hopefully any storms Christmas Eve don't materialize.
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