Cold Spell Late Feb/ Early March Technical Discussion only MOD NOTE POST #1

DOCARCH

Rebelbrowser wrote: »

Amazing charts. Just a slightly depressing thought though. A lot of us pass our winters on here looking for snow to show up on day 10 of some model. Presuming this upcoming spell is anything like as now modelled, isnt it going to be hard to muster up the enthusiasm in future to post on threads regarding the possibility of a nw incursion having -7 uppers which might, just might give wet snow for a time if you are above 150m?

People have short memories!

Meteorite58

As a guide looking like Tues evening for the first chance of substantial snow amounts down over the country. Models not in agreement yet as you would imagine, track and intensity nearer the time.

Cloudio9

Meteorite58 wrote: »

Temperatures across Europe last 24 hrs

Love watching that chart. It’s like someone is pouring a big jug of blue ink over Eastern Europe.

Reckless Abandonment

Question. The flow looks to be east north east for most of the week with is fantastic for streamer development .But Could the little front/disturbances in the flow reduce overall snow amounts for some?? as they would reduce convection by increasing cloud cover. I know they would bring snow to more people but at the risk of redusing streamer activity.

Meteorite58

Rebelbrowser wrote: »

Amazing charts. Just a slightly depressing thought though. A lot of us pass our winters on here looking for snow to show up on day 10 of some model. Presuming this upcoming spell is anything like as now modelled, isnt it going to be hard to muster up the enthusiasm in future to post on threads regarding the possibility of a nw incursion having -7 uppers which might, just might give wet snow for a time if you are above 150m?

Indeed but the cold looks so entrenched by this stage and the models atm in good agreement of a deep area of LP close to Ireland coming up from the S laden with moisture would give rise to the probabilities of substantial snowfalls. Track and intensity more near the time. No doubt early stages and evolving but that is the aim to try to determine what is going to happen.

Meteorite58

https://twitter.com/severeweatherEU/status/967311172553854977

https://twitter.com/severeweatherEU/status/967323567896612864

https://twitter.com/severeweatherEU/status/967321841080635392

Gaoth Laidir

Reckless Abandonment wrote: »

Question. The flow looks to be east north east for most of the week with is fantastic for streamer development .But Could the little front/disturbances in the flow reduce overall snow amounts for some?? as they would reduce convection by increasing cloud cover. I know they would bring snow to more people but at the risk of redusing streamer activity.

There's very little land-based convection at this time of the year, only sea-based, so cloud cover won't really have much effect. A kink in the isobars is a signal of an upper level forcing which will actually help boost convection. That's the kind of thing were looking for.

typhoony

Wednesday is an ice day for the whole country, no doubt somewhere will get above freezing but some parts of the country could struggle to get above -2c

Donegal Storm

Not far off 40cm of snow in Cork city centre on this mornings ECMWF from the potential storm on Thursday/Friday, GFS has more of a nationwide event but with a quick thaw afterwards. I suspect it'll be Wednesday before we have a clearer idea of how that low is going to behave but potential definitely there for something big


With thestreamers from Tuesday night to Thursday, while the charts look great at face value for snow, wouldn't the strong winds be a problem in that the airmass will have very little time over the Irish Sea to pick up moisture?

pad199207

Donegal Storm wrote: »

Not far off 40cm of snow in Cork city centre on this mornings ECMWF from the potential storm on Thursday/Friday, GFS has more of a nationwide event but with a quick thaw afterwards. I suspect it'll be Wednesday before we have a clearer idea of how that low is going to behave but potential definitely there for something big


With thestreamers from Tuesday night to Thursday, while the charts look great at face value for snow, wouldn't the strong winds be a problem in that the airmass will have very little time over the Irish Sea to pick up moisture?

Yes I’d be weary of those strong winds in off the sea during the week if I was on the immediate coast

Snow angel

I posted this in chat but I might get better clarification here.

Please excuse my ignorance on this but people have mention the gfs shows blizzard like conditions in the FI next weekend. I was wondering how this can happen when the 850 temps are only -4 at best in the south? Can someone explain to which chart shows these conditions as I only understand 2-3 of the charts personally. Is it the low pressure that signals blizzard conditions. Just want to learn, not doubting anyone.

JanuarySnowstor

Snow angel wrote: »

I posted this in chat but I might get better clarification here.

Please excuse my ignorance on this but people have mention the gfs shows blizzard like conditions in the FI next weekend. I was wondering how this can happen when the 850 temps are only -4 at best in the south? Can someone explain to which chart shows these conditions as I only understand 2-3 of the charts personally. Is it the low pressure that signals blizzard conditions. Just want to learn, not doubting anyone.

-4 from the Atlantic is rain or sleet but -4 with a cold frigid airmass already in place would mean snow. Air is much dryer from the East so you don't need such cold upper temps

kod87

JanuarySnowstor wrote: »

-4 from the Atlantic is rain or sleet but -4 with a cold frigid airmass already in place would mean snow. Air is much dryer from the East so you don't need such cold upper temps

But with those higher uppers you will need surface temps to be at 0 or below surely, that won't be the case next weekend which is why I feel snow would be marginal in the GFS set up (which I feel is an unlikely setup anyway)

Oneiric 3

850 hPa temp anomaly analysis (GFS) for the last 30 hrs up to 6z. Western edge of that cold air over NE Europa now pushing west

Kermit.de.frog

Temperatures for Wednesday, Wednesday night, Thursday

km79

Kermit.de.frog wrote: »

Temperatures for Wednesday, Wednesday night, Thursday

That wouldn’t be TOO bad s regards frozen pipes

Kermit.de.frog

The distribution of the snow showers across the models (low and high res) is gradually getting more widespread and with intensity being upgraded as we get closer...ECM going for isolated thunderstorms now in the east. The models never handle streamer action well to be honest.

snowstorm445

Looking further ahead, the GFS seems to be firming up on a breakdown of the cold spell by next weekend as Atlantic lows moving up from the south beginning to break down the block (but not without dumping a load of snow over us beforehand).

The ECM keeps us in frigid air right through to the end of the run, as the lows are kept further away and a northeasterly flow is established.

Gaoth Laidir

Snow angel wrote: »

I posted this in chat but I might get better clarification here.

Please excuse my ignorance on this but people have mention the gfs shows blizzard like conditions in the FI next weekend. I was wondering how this can happen when the 850 temps are only -4 at best in the south? Can someone explain to which chart shows these conditions as I only understand 2-3 of the charts personally. Is it the low pressure that signals blizzard conditions. Just want to learn, not doubting anyone.

That's why looking at forecast sounding is important. At that time of your chart, the forecast for the vertical profile of the atmosphere over Dublin is shown below. The temperature curve (red) and dewpoint curve (green) are together through a deep layer of the lower atmosphere, and they're all pretty much to the left of the 0-degree isotherm (blue). Just the very lowest surface layer is around or just above zero, and that's where the marginality comes into play. In that sounding it looks like very wet snow or sleet.

But if you look at the 850 hPa temperature (3-4 degrees, as you say), on its own sometimes doesn't show the whole picture. It's below it that's important.

Mickeroo

So the east is getting the worst/best of it with a decent but more manageable covering in the west if I'm interpreting the models right?

Temps not as crazy low as 2010 but the amount of snow coming is what makes this exceptional?

snowstorm445

Mickeroo wrote: »

So the east is getting the worst/best of it with a decent but more manageable covering in the west if I'm interpreting the models right?

Temps not as crazy low as 2010 but the amount of snow coming is what makes this exceptional?

It would seem that way. The cold is certainly not to be scoffed at though, could reach negative double digits in places given the right conditions.

Oneiric 3

Just looking at temp stats for Moscow, and the lowest minima recorded their during February was -27.1 in 1956, most likely early in the month when eastern Europe was under a big easterly freeze.



Will be interesting to see if this record is broken over the next few days, with the ECM at least going for a minima of -26 sometime early Tuesday for the Moscow region, if it does, and the possibility is there, then it would be extraordinary given that we are now at the end of the month.

Interestingly, temps got down to -8.2 at Dublin Apt on the 19th of that month, with an average monthly minima of -0.7c, and -8.3c at Shannon Apt on the 26th, with a mean monthly minima of an even colder -1.9c.


Interesting discussion on the February 1956 cold spell both here in Europe and over in the States here:

ftp://ftp.library.noaa.gov/docs.lib/htdocs/rescue/mwr/084/mwr-084-02-0066.pdf

Soccarboy11

GFS 12z looking good at +84hrs. Similar to earlier 6z run it looks like

850Hpa


500hpa


Looking even better at 90hrs

850hpa


500hpa

patneve2

Late Tuesday/early Wednesday looking very snowy on the E Coast

Kermit.de.frog

Cold air being difficult to shift. GFS eyes snow machine for end of the week. Very serious conditions if it verified.

patneve2

Kermit.de.frog wrote: »

Cold air being difficult to shift. GFS eyes snow machine for end of the week. Very serious conditions if it verified.

A mad set up alright. Would be NE gales or strong gales, with moderate to heavy ppn. Surely would rival 1982.

Kermit.de.frog

UKMO also shows the prospect of a major snow event.

Gaoth Laidir

Here are the latest water temperatures, with up to 8-9 °C the most we're looking at.



By Wednesday, this translates to enormous latent heat energy transfer from the sea to the air above it, with up above 400 Wh/m² getting that convection going. That's equivalent to around 1% of the maximum solar irradiation available over land at midday if the skies are clear, but in the case of the sea convection this energy pump is working 24-hour shifts as we're not relying on solar heating.



Sensible heat transfer

Gaoth Laidir

Radiosonde 500-1000 hPa thickness analysis for 12Z today (blue lines and brown station figures (m)), with surface isobars in green. We're currently above 540 dam and the 510 dam line is over central Poland. The latter is what will make it over to us by mid-week, with even the 504 line threatening.

Meteorite58

Tuesday getting more into focus, weak front moving down over the country. Not much precipitation showing up on the ARPEGE yet.