Prelude to Cold Weather/Snow - Sun 25th Feb (Onwards)

sdanseo · 20-02-2018 8:44pm

Weathercheck wrote: »

The EC 12z moderates the 850s which may result in marginality near coasts. The shortwave over the top of block leads to a concern it may be stronger in upcoming runs and result in more high pressure influence and pushing the Siberian plunge further south. The shortwaves in the North Sea modify the flow reaching Ireland giving uppers around -9 instead of -13, which at this time of year could be difference between hail, wet snow and dry sticking snow

My knowledge of shortwaves is pretty much non existent but is it not fair to say that if the easterly flow is so dominant and followed by such a depth of extreme cold, that the shortwave would be but a brief feature doomed to inevitably be beaten into submission by the cold flow which we believe will keep coming?

I'm seeing the shortwave as David and the cold mass as Goliath here?

Reckless Abandonment · 20-02-2018 8:45pm

Weathercheck wrote: »

The EC 12z moderates the 850s which may result in marginality near coasts. The shortwave over the top of block leads to a concern it may be stronger in upcoming runs and result in more high pressure influence and pushing the Siberian plunge further south. The shortwaves in the North Sea modify the flow reaching Ireland giving uppers around -9 instead of -13, which at this time of year could be difference between hail, wet snow and dry sticking snow

Would only be an issue with day time snow. Going by the charts we would have plenty falling at night to
.

lucernarian · 20-02-2018 8:46pm

Weathercheck wrote: »

The EC 12z moderates the 850s which may result in marginality near coasts. The shortwave over the top of block leads to a concern it may be stronger in upcoming runs and result in more high pressure influence and pushing the Siberian plunge further south. The shortwaves in the North Sea modify the flow reaching Ireland giving uppers around -9 instead of -13, which at this time of year could be difference between hail, wet snow and dry sticking snow

Or it could be the difference between a cold but dry few days, and regular troughs in sub -6 850 hPa air. 2010 was quite marginal at times but it was able to deliver repeated and prolonged precipitation. Totally different event I know.

Agree completely with the shortwave heading to iceland, not what I want to see.

And the cold getting here quicker does seem to reduce the severest cold, but that may not be an issue just yet. We had dream runs earlier so I'm not that worried. I'd love access to the ECM ensembles to see how many signal that development near Iceland.

lucernarian · 20-02-2018 8:47pm

nacho libre wrote: »

Yes shortwaves in the wrong place normally scuppers a cold spell, but in this case shortwaves are good because once that cold air is entrenched ( and movement will always be west of the general pattern), then we have shortwave snow making machines on our hands. The more shortwaves the better because the large Greenland block will keep us embedded in deep cold.
That shortwaves over Iceland won't do anything to our block, it can't develop into a powerful low resulting in our blocked being sunk. I will eat my socks if it does.

Do you see much in that shortwave near Iceland in the latest ECM run?

nacho libre · 20-02-2018 8:49pm

sryanbruen wrote: »

A lot of the 2010 upper air temperature synoptics don't seem that impressive to me given what had taken place. However, the thing with them is that the cold was well and truly locked in before them.

Wasn't there - 15 upper air on the 16th of December 2010? Or am I mistaken? Anyway we don't need wholly impressive uppers when it is coming from a landmass that is already frigid.

nacho libre · 20-02-2018 8:50pm

lucernarian wrote: »

Do you see much in that shortwave near Iceland in the latest ECM run?

I don't, but then i could be wrong. Gaoth Laidir and Weathercheck are the pros.

sryanbruen · 20-02-2018 8:50pm

nacho libre wrote: »

Wasn't there - 15 upper air on the 16th of December 2010? Or am I mistaken? Anyway we don't need wholly impressive uppers when it is coming from a landmass that is already frigid.

-10 for us.

lucernarian · 20-02-2018 8:51pm

nacho libre wrote: »

Wasn't there - 15 upper air on the 16th of December 2010? Or am I mistaken? Anyway we don't need wholly impressive uppers when it is coming from a landmass that is already frigid.

I was looking at the reanalysis chart for that day, the -15 contour didn't seem to reach Ireland.

BLIZZARD7 · 20-02-2018 8:54pm

lucernarian wrote: »

I was looking at the reanalysis chart for that day, the -15 contour didn't seem to reach Ireland.

I think 1987 was the last time it reached Ireland, not sure when before that.

mojesius · 20-02-2018 8:56pm

Thank you all for the analysis and predictions, very exciting stuff. Husband and mam are laughing here at me with my excitement, they don't realise I'm excited at the prospect of a few days snow in so they can share daytime baby duties with me. I'll be the one laughing then!

(Based rurally, neither car is snow worthy)

sryanbruen · 20-02-2018 8:57pm

BLIZZARD7 wrote: »

I think 1987 was the last time it reached Ireland, not sure when before that.

Yep. 1991 failed but it had the potential as the -20c isotherm just barely made it into the UK.

ninebeanrows · 20-02-2018 9:06pm

EPS mean below -8C from 144hr to 240hr in eastern Ireland

George Sunsnow · 20-02-2018 9:08pm

nacho libre wrote: »

Given the source, -9 uppers should be more than enough to get powdery snow at this time of year

Absolutely
No fears to measure at all

MissMoc · 20-02-2018 9:08pm

People on here that can interpret charts and runs far better than the vast majority of us are doing is a service - for free!! They are not in control of Mother Nature and can’t predict the final outcome but I for one value their insights and enjoy following.

George Sunsnow · 20-02-2018 9:11pm

sryanbruen wrote: »

-10 for us.

And higher dewpoints than are likely in next weeks flow

davidsr20 · 20-02-2018 9:23pm

What’s the current status. Looking at weatherchevks posts he doesn’t seem convinced is there a downturn?

M.T. Cranium · 20-02-2018 9:33pm

joe40 wrote: »

I recall a few years ago there was very cold snowy weather in England and eastern parts of Ulster. Farmers in antrim had trouble rescuing sheep. But only mild conditions in western parts. I live in Donegal and remember been all jealous. Is this likely to be a similar set up. It might even have been feb, I can't remember the year

I believe that was in March 2013. Some parts of eastern and southern Ireland got snow during that cold spell, but it wasn't anything to rival Dec 2010. I had a look at some charts from that period and uppers briefly got below -10 C but in any case the month is more remembered for a dry cold that persisted for about three weeks (roughly 9th to 1st of April).

Have been catching up (my sleep cycle has shifted well away from what would be appropriate to the local time zone, I just slept from 0500h to 1100h so it takes a while to review all the new data then read through the threads here and (skim mostly) NW. Looks like my prediction of 62 pages by 2100h is going to verify, I can always influence that prediction of course (by posting a lot) too bad you can't do that with a weather forecast!

My overall impression was something along the lines of very slight downgrades on GFS, not quite so apocalyptic on GEM, ECM a somewhat different route than last night, but probably equally impressive in its own way.

This is a massive outbreak and I think the larger weather services will come under increasing pressure to warn of its potential as models keep churning out roughly the same scenario run after run. That NMM animation was a good illustration of how the westward progress of the cold air is likely to accelerate and with that you get a wider spread of possible arrival times.

George Sunsnow · 20-02-2018 9:34pm

davidsr20 wrote: »

What’s the current status. Looking at weatherchevks posts he doesn’t seem convinced is there a downturn?

He’s just over analyising this run a bit
For example despite that Iceland SW,he says the mean 850 temp on the ECM from the start to its last modeled date doesn’t go warmer than -8
That from the east is a fantastic mean because if you get cold and snow cover in Britain and the low humidity in that air traveling over it there’s no marginality

What he’s concerned about is the Iceland SW pushing the high a few hundred miles too far south so we are left with a dry easterly
It’s possible but a bit counter intuitive to my mind in this set up
The overnight ECM will answer that
I think it will drift west tbh
There’s nothing only hostility to its east

Jumpinjames · 20-02-2018 9:38pm

I see Met Eireann have a low temperature warning for tonight.... for -3. Seems a tad over the top. If next week materializes, then could we see red warnings being issued or do they do those for extreme temperatures?

Meteorite58 · 20-02-2018 9:39pm

ECM showing some very cold temperatures. Perhaps the main mass of cold Easterly air taking a more S'ly route as the week progresses and showing more of a Northerly aspect aided by the Jet from around Thursday, in itself coming from very cold route straight out of Greenland. That looks to set up a very interesting convergence over Ireland where it reaches the cold E'ly air . Line of Thunderstorms along the Atlantic Coasts and dumping snow inland ?

Fascinating spell of weather coming up.

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Youngpensioner · 20-02-2018 9:41pm

Jumpinjames wrote: »

I see Met Eireann have a low temperature warning for tonight.... for -3. Seems a tad over the top. If next week materializes, then could we see red warnings being issued or do they do those for extreme temperatures?

They issue wind warnings when Gerry gets bloated these days

Mullaghteelin · 20-02-2018 9:42pm

The lowest 850hpa temps of recent times may have been the easterly of March 11th/12th 2013.
We managed -13C or thereabouts.

This site is great for looking back at upper air data.
http://weather.uwyo.edu/upperair/europe.html

I remember it well
Dew points were around -8C, with powdery snow that blew around like clouds of talc, in gale force winds.

Youngpensioner · 20-02-2018 9:44pm

M.T. Cranium wrote: »

I believe that was in March 2013. Some parts of eastern and southern Ireland got snow during that cold spell, but it wasn't anything to rival Dec 2010. I had a look at some charts from that period and uppers briefly got below -10 C but in any case the month is more remembered for a dry cold that persisted for about three weeks (roughly 9th to 1st of April).

Almost everywhere saw at least some snow in that march. Was East ulster that got buried at the end of the month in the blizzard while the rest of us suffered.

pad199207 · 20-02-2018 9:46pm

Meteorite58 wrote: »

ECM showing some very cold temperatures. Perhaps the main mass of cold Easterly air taking a more S'ly route as the week progresses and showing more of a Northerly aspect aided by the Jet from around Thursday, in itself coming from very cold route straight out of Greenland. That looks to set up a very interesting convergence over Ireland where it reaches the cold E'ly air . Line of Thunderstorms along the Atlantic Coasts and dumping snow inland ? Fascinating spell of weather coming up.

Forget about Greenland, anything coming in from that atlantic direction can get lost no matter how cold it is. Let the gates stay open for everything from the east!

Reckless Abandonment · 20-02-2018 9:46pm

Youngpensioner wrote: »

Almost everywhere saw at least some snow in that march. Was East ulster that got buried at the end of the month in the blizzard while the rest of us suffered.

I cant remember any snow in Dublin in 2013 .

Rougies · 20-02-2018 9:52pm

Reckless Abandonment wrote: »

I cant remember any snow in Dublin in 2013 .

Neither can I, if there was any it must have been very short lived and I missed it.

sryanbruen · 20-02-2018 9:53pm

Reckless Abandonment wrote: »

I cant remember any snow in Dublin in 2013 .

I had snow showers on 22 January, 23/24 February (very very weak ones), 11/19/20/26/27 March. Here's an example of a picture of it snowing in Dublin on 19 March 2013:

Dublin Airport on 11 March 2013:

EDIT: I had forgotten where I found the Dublin Airport photo at the time, but a similar one can be found in an article on the Journal - Lumen posted the link below. The top one I forget too.

Lumen · 20-02-2018 9:54pm

Reckless Abandonment wrote: »

I cant remember any snow in Dublin in 2013 .

I guess it depends on what you mean by "snow" and "in Dublin".

Snow at Dublin Airport
http://www.thejournal.ie/dublin-airport-snow-delays-827194-Mar2013/

Hail at Grand Canal Dock
http://www.thejournal.ie/hailstones-dublin-pictures-834987-Mar2013/

Saganist · 20-02-2018 10:00pm

Reckless Abandonment wrote: »

I cant remember any snow in Dublin in 2013 .

Yep. March that year was pretty cold. I had small amounts of lying snow, which melted pretty quickly a few mornings in North Dublin that year.

sryanbruen · 20-02-2018 10:02pm

Saganist wrote: »

Yep. March that year was pretty cold. I had small amounts of lying snow, which melted pretty quickly a few mornings in North Dublin that year.

Yeah, the only time I woke up to lying snow that March regardless of the snow showers and how cold it was (it was down to persistence than extremes, it's a very forgettable March in terms of extremes) was the 27th which had my neighbourhood covered in white courtesy of the snow showers and severe frost.

Prelude to Cold Weather/Snow - Sun 25th Feb (Onwards)

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