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

Gaoth Laidir

I think Emma's slipped on the snow on her way here. So far it's only the immediate east coast up to Bray that's showing any decent rates. It stops immediately inland. There's a huge snow shadow to the northwest of the Wicklow mountains, through west Dublin, Kildare, Meath and again further inland. Casement has only crept up to 23 cm, Dublin Airport 15 cm. Not too spectacular, considering.

There has been no accumulation at Cork Airport (still at 4 cm) but Roches Point is reporting moderate snow. Only Johnstown Castle has reported heavy snow. The traffic cams don't show exceptional overnight accumulations over what was already there.

51 cm is recorder in Devon/Cornwall, but a look at the radar shows that the snow wants to avoid land at all costs.

CirrusBusiness

Looks like the worst is yet to hit in the next 12 hours going by Hirlam snow depths on WXCHARTS.

SleetAndSnow

CirrusBusiness wrote: »

Looks like the worst is yet to hit in the next 12 hours going by Hirlam snow depths on WXCHARTS.

I'm not liking that look of that sleet just next to the cork city coast on the radar, it's been slowly moving it ways up.

SeaBreezes

According to ECM we are going to get the wind south coast only tonight in the wee hours, would this be right?
ICON seems to dissolve the low completely..

pistolpetes11

The thing is about that huge snow shad , its not correct ,

Snowed all night here in Newbridge and I know Naas got it really bad but we were in that "shadow" all night long

Granted Ive probably only got an extra 2/3 cm from all night snow but it was that fine snow pellet stuff , have some big drifts also .

I wont what is causing the radar shadow because it is snowing

This pic was from 2AM when it was coming down hard in Nass and heavy snow grains in Newbridge

Gaoth Laidir wrote: »

I think Emma's slipped on the snow on her way here. So far it's only the immediate east coast up to Bray that's showing any decent rates. It stops immediately inland. There's a huge snow shadow to the northwest of the Wicklow mountains, through west Dublin, Kildare, Meath and again further inland. Casement has only crept up to 23 cm, Dublin Airport 15 cm. Not too spectacular, considering.

There has been no accumulation at Cork Airport (still at 4 cm) but Roches Point is reporting moderate snow. Only Johnstown Castle has reported heavy snow. The traffic cams don't show exceptional overnight accumulations over what was already there.

51 cm is recorder in Devon/Cornwall, but a look at the radar shows that the snow wants to avoid land at all costs.

gozunda

sdanseo - update on below. Snow arrived last night but direction appeared to be variable with little significant wind from storm Emma evident

Snow deposited is 'wet' / dust and whilst accumulating has also been subject to an ongoing melt despite temperatures staying below -1.5c

sdanseo wrote:

Siobhan just specifically called out EPS (ECMWF) for its long term accuracy with this. 

Two elements to this.
The more obvious is that the side of a mountain facing into the wind gets hit harder. More drifting, much more exposed.

The lee side often suffers more snow because the air mass hits the mountain range, rises into colder air (1 degree per 500ft / 3 degrees per 500m) and condenses rapidly, dumping snowmageddon on the poor (lucky) souls below.

gozunda wrote: »

Re. RTE Six News Weather report "Snow on Lee side of mountains"

Ah ok thanks for that.
Further:
I am located close to the Galtee Mountains and depending on wind direction are sometimes sheltered from precipitation* being carried with wind hitting the other (windward) side of the mountain.

Notably we have had very little snow over the last two days.

I will report back tmrw as to whether the advancing front plus snow makes it across the mountain to this location ...

Edit: interesting article from wiki on this

https://en.m.wikipedia.org/wiki/Orographic_lift

Gaoth Laidir

Sounding for Newcastle (next to Casement) for now shows how mid levels are drying out. Precipitation normally occurs where r.h. at 700 hPa is >90%, but here it's not that. By midday more levels dry out so I wouldn't expect any heavy precip throughout the morning. I got a few more cms in Celbridge overnight but not what was expected.

Whehey!

CirrusBusiness wrote: »

Looks like the worst is yet to hit in the next 12 hours going by Hirlam snow depths on WXCHARTS.

Is this true? Because I'm just a later waking up and theres already definitely approx two foot of snow outside my house. I'm in wex Town. Unbelievable amount of snow has fallen! Ridiculous

Whehey!

CirrusBusiness wrote: »

Looks like the worst is yet to hit in the next 12 hours going by Hirlam snow depths on WXCHARTS.

Is this true? Because I'm just a later waking up and theres already definitely approx two foot of snow outside my house. I'm in wex Town. Unbelievable amount of snow has fallen! Ridiculous

Neddyusa

pistolpetes11 wrote: »

The thing is about that huge snow shad , its not correct ,

Snowed all night here in Newbridge and I know Naas got it really bad but we were in that "shadow" all night long

Granted Ive probably only got an extra 2/3 cm from all night snow but it was that fine snow pellet stuff , have some big drifts also .

I wont what is causing the radar shadow because it is snowing

This pic was from 2AM when it was coming down hard in Nass and heavy snow grains in Newbridge

[/IMG]

Not to be smart, but are you sure that all that snow was coming from the sky??
Plenty of snow blown in sheets here over-night in Roscommon, but it's coming from the ground rather than the clouds!
Drifts now over 4ft and plenty of bare ground in places.

What is the reason for the snow avoiding landmass GL?
Is it the low humidity at higher levels?

pistolpetes11

Neddyusa wrote: »

Not to be smart, but are you sure that snow was coming from the sky??
Plenty of snow blown in sheets here over-night in Roscommon, but it's coming from the ground rather than the clouds!
Drifts now over 4ft and plenty of bare ground in places.

What is the reason for the snow avoiding landmass GL?
Is it the low humidity at higher levels?

Yeah it was coming from the Sky for sure , the was some blowing snow about for sure but this was fresh stuff , the ice pellets if you will ,

Thinking the radar maybe has issues picking them up ?

harr

Neddyusa wrote: »

Not to be smart, but are you sure that all that snow was coming from the sky??
Plenty of snow blown in sheets here over-night in Roscommon, but it's coming from the ground rather than the clouds!
Drifts now over 4ft and plenty of bare ground in places.

What is the reason for the snow avoiding landmass GL?
Is it the low humidity at higher levels?

This was what was happening to us ,light snow all night but it was only what was coming off the rooftops ..a lot less snow this morning on the roof.
I was definitely in that Wicklow shadow.
Still hard to tell if it’s actually snowing.
+1 degrees here now and thaw definitely on.
Kildare/Laois border

SpitfireIV

pistolpetes11 wrote: »

The thing is about that huge snow shad , its not correct ...

It's correct for north Carlow, that's for sure, I'm in Carlow town and we only got a dusting, just enough to cover what disappeared yesterday. Very disappointing but the Blackstairs really shafted us :-(

SEPT 23 1989

I don't understand those Casement readings I live in Newcastle and we had a hell of a lot more than that

revelman

Gaoth Laidir wrote: »

Sounding for Newcastle (next to Casement) for now shows how mid levels are drying out. Precipitation normally occurs where r.h. at 700 hPa is >90%, but here it's not that. By midday more levels dry out so I wouldn't expect any heavy precip throughout the morning. I got a few more cms in Celbridge overnight but not what was expected.

I’m contributing this to the technical discussion to confirm that there are actually significant localized falls of snow taking place outside the East. We are now getting significant accumulation of snow here near Kinsale. It was sleet earlier but turned in the last hour to heavy dry powedery snow that is accumulating rapidly. I’m right on the coast by the way and we already had 20cm of snow measured on level ground yesterday evening. It seems to be getting heavier and heavier.

Gaoth Laidir

Casement readings are flat cover, not including drifts.

Having said all I said, I have 2-3-ft drifts here now and it's snowing lightly. It did deliver something overnight alright. It's the most snow I've seen since 1982. Far outweighs 2010 in my area anyway.

Reversal

Gaoth Laidir wrote: »

Casement readings are flat cover, not including drifts.

Having said all I said, I have 2-3-ft drifts here now and it's snowing lightly. It did deliver something overnight alright. It's the most snow I've seen since 1982. Far outweighs 2010 in my area anyway.

Not too far from casement myself. I can confirm a huge amount of snow has fallen so far since last night. Depths on open ground have increased slightly despite significant drifting. So while official readings have crept up, the amount of snow around the place has increased massively.

Gaoth Laidir

And in a wicked twist, Knock is reporting zero snow cover! How often does that happen?!

Casement's description of its cover has changed from even to uneven loose dry snow this morning.

EDIT: Knock is actually reporting 1 cm of patchy snow cover.

PukkaStukka

Where I am here in North county Dublin, there has been little additional snow overnight. Looking at the Netweather radar, I confirms my suspicion that some of what fell was rain. Current temp is 0.C but the wind is vicious. Looking further into the Irish Sea, we may have more snow later but I forming the view that the worst of this event is over for us.

ZX7R

Gaoth Laidir wrote: »

Casement readings are flat cover, not including drifts.

Having said all I said, I have 2-3-ft drifts here now and it's snowing lightly. It did deliver something overnight alright. It's the most snow I've seen since 1982. Far outweighs 2010 in my area anyway.

I don't doubt you goath , but there was a kind of shadow on the met earann radar the whole night, more indicating mist, heavy perception seemed to move both sides of what you show, it did snow drift, but at a very low intensity

ascophyllum

5 - 10cm in southwest corner of Mayo, Hirlam and Arpege consistently showed a nice blob of moisture extending north through Connemara reaching us on their models yesterday. Delighted! GFS has the precipitation here continuing all day and into tomorrow...

Gaoth Laidir

Cork back up to 5 cm of even snow and Shannon got in on the act with 3 cm overnight. Wet-bulb temperatures in the south and southwest now hovering just below zero, so that'll do.

Mickeroo

ascophyllum wrote: »

5 - 10cm in southwest corner of Mayo, Hirlam and Arpege consistently showed a nice blob of moisture extending north through Connemara reaching us on their models yesterday. Delighted! GFS has the precipitation here continuing all day and into tomorrow...

Got barely a cm in Castlebar and roads from there to Claremorris were in better condition than they have been during some yellow warnings. Didn't quite get far north enough to get me off work today, which I think is what most of the models were showing anyway. Oh well!

John.Icy

You have to hand it to some of the hi res precip forecasts. Many of them decreased intensity just before Dublin City - and that's roughly what's came about with next to nothing here since 4am. I'd love to know the reason, seeing as precipitation has at least on radar moved far enough North to cover more of Dublin. Wicklow mts.?

Looks like it's about to fizzle out for most of Dublin on radar now though. Wicklow and Wexford are in for a right old day.

Call me Al

Can someone advise what is a blizzard defined as? I ask because here outside Dunboyne the wind is still howling with squalls, white-outs and swirling sideways snow.

RobertKK

Call me Al wrote: »

Can someone advise what is a blizzard defined as? I ask because here outside Dunboyne the wind is still howling with squalls, white-outs and swirling sideways snow.

Gale force winds with snow, sustained for at least 3 hours.

Rebelbrowser

SEPT 23 1989 wrote: »

I don't understand those Casement readings I live in Newcastle and we had a hell of a lot more than that

Yup, as per yesterday I am still befuddled by Cork airport readings. I am really close to it so can judge. We have at least an extra 6cm snow lying now that wasn't there at 8pm yesterday but it has gone up by 1cm only to 5cm.

Snowing away moderately all the while here.

Greenmotors

John.Icy wrote: »

You have to hand it to some of the hi res precip forecasts. Many of them decreased intensity just before Dublin City - and that's roughly what's came about with next to nothing here since 4am. I'd love to know the reason, seeing as precipitation has at least on radar moved far enough North to cover more of Dublin. Wicklow mts.?

Looks like it's about to fizzle out for most of Dublin on radar now though. Wicklow and Wexford are in for a right old day.

No snow in my village in Wexford all week, now I have drifts blocking the road at least 4ft high. Can leave the house with the driving snow as it is like sand paper. When is the wind due to die down in Wexford?

mhiggy09

What's the chance of more streamers in off the East coast later today. Here in south Cavan we go only really got hot by the wind off Emma, very little precipitation apart for a few showers of icy pellets. Disappointed as it looked like it would reach this far and we would be in for some more snow.

Oneiric 3

I am struck at how ill defined the whole structure of 'Emma' is.



Hard to make out any notable fronts or depressions.