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

Musicman2000

munsterlegend wrote: »

I note Met Eireann in their update have the dreaded rain word from Storm Emma. The harmonie model must be showing that closer to the coast.

Far south west towards Kerry looks like rain . Rest of the country is fine for snow

M.T. Cranium

With the guidance available rain is going to have to be inserted into any forecast but that doesn't mean a colder outcome won't happen when Emma tries to move all that cold air, she looks a bit out of shape to do that much heavy lifting, rain to south coast possibly but not much impact further inland ... GEM actually looks most reasonable of all models this morning, maybe having Canadian weather all over the northern hemisphere is improving its performance.

mirrorwall14

The first shower on the radar that has stuck together across England looks to be entering the Irish sea now. Can any of the technical experts say what happens, does this beef up again? Or stay the same? Or join whats forming?

downwiththatsor

munsterlegend wrote: »

I note Met Eireann in their update have the dreaded rain word from Storm Emma. The harmonie model must be showing that closer to the coast.

It's going to be touch and go for parts of the Kingdom
Freezing level 9am Friday from this mornings Ecmwf.

cherryghost

HIRLAM snowfall last night was pretty nailed, expected 15 and got 12, but 15 was recorded in many areas (ME also mentioned it). HIRLAM has no let up in heavy showers for Red alert areas today, and later this evening a slight shift to Wicklow/Wexford/Carlow. Tonight heavy falls expected along the south coast as a wind direction change pushes precip from the sea. HIRLAM also wants an almost nationwide disruptive event starting as early as rush hour tomorrow.

DOCARCH

cherryghost wrote: »

HIRLAM snowfall last night was pretty nailed, expected 15 and got 12, but 15 was recorded in many areas (ME also mentioned it).

Evelyn said 16cm recorded at Casement.

Villain

Interesting Harmonie has the precip as rain on the East coast at Dublin later tomorrow morning, I wonder is that why John didn't want to commit

Villain

Villain wrote: »

Interesting Harmonie has the precip as rain on the East coast at Dublin later tomorrow morning, I wonder is that why John didn't want to commit

The Eagle was fairly specific on the 7.55 forecast. ME aren’t committing to the late Thurs/Fri event until model runs later in the day.

munsterlegend

Villain wrote: »

Interesting Harmonie has the precip as rain on the East coast at Dublin later tomorrow morning, I wonder is that why John didn't want to commit

How is the rest of the country looking for tomorrow in terms of snow and not rain? Thanks again.

downwiththatsor

Villain wrote: »

Interesting Harmonie has the precip as rain on the East coast at Dublin later tomorrow morning, I wonder is that why John didn't want to commit

Next Harmonie update is what they are waiting for then?

ninebeanrows

Villain wrote: »

Interesting Harmonie has the precip as rain on the East coast at Dublin later tomorrow morning, I wonder is that why John didn't want to commit

There are some higher DPs around parts of north Leinster in that long maritime fetch but the HARMONIE in my experience can be a little too pessimistic with regards to snow. However certainly a risk of the snow turning a little wet right at the coast along Dublin northwards and also along the south coast, Wicklow coast should do okay as shorter fetch so less modification of the flow from Wales.

However a few miles inland and it is all powder. I wouldn't get too fused about the edges on bands of the harmonie showing rain this is just how it goes sometime,

Sure it is progging some the showers as rain for the east today!

Weathercheck

Weathercheck wrote: »

There are some higher DPs around parts of north Leinster in that long maritime fetch but the HARMONIE in my experience can be a little too pessimistic with regards to snow. However certainly a risk of the snow turning a little wet right at the coast along Dublin northwards and also along the south coast, Wicklow coast should do okay as shorter fetch so less modification of the flow from Wales.

However a few miles inland and it is all powder. I wouldn't get too fused about the edges on bands of the harmonie showing rain this is just how it goes sometime,

Sure it is progging some the showers as rain for the east today!

DPs appear negative out to sea away from the English west coast currently.

Reckless Abandonment

Even EURO4 had rain on the edge of all the showers over night and today. certainly didnt happen so far

George Sunsnow

Weathercheck wrote: »

There are some higher DPs around parts of north Leinster in that long maritime fetch but the HARMONIE in my experience can be a little too pessimistic with regards to snow. However certainly a risk of the snow turning a little wet right at the coast along Dublin northwards and also along the south coast, Wicklow coast should do okay as shorter fetch so less modification of the flow from Wales.

However a few miles inland and it is all powder. I wouldn't get too fused about the edges on bands of the harmonie showing rain this is just how it goes sometime,

Sure it is progging some the showers as rain for the east today!

It also progged yesterday’s front as sleet and rain and it was all snow and graupel

Not a flake of snow in Arklow last night
Not one flake and that’s likely to be the same today
Southern extent of activity is about kilcoole/greystones co Wicklow.
Anglesea shadow and welsh shadow
Straight easterly doesn’t work here

Dew point here is -9c though :O

cherryghost

GFS rolling out now. Says moderate/heavy snow spreading down the East coast, and continuous feed of shows further inland, maybe as far as Galway. South coast to get another bite of the cherry tonight.

Daniel2590

06z GFS has -16 uppers just off the east coast 1am on Thursday

Daniel2590

Sorry for double posting, GFS has Storm Emma ever so slightly further north east, certainly not further west

Elmer Blooker

How many years have we waited for a chart like this? How far north that front gets is still uncertain as the Eagle on the radio earlier couldn't go beyond 36 hours! If only that Azores low headed towards Spain!
I checked NW and the MOD forum is as dead as a dodo, you can tell by this chart that most members are concentrated in southern England and have lost interest for the time being.

Villain

Hiram looks very tasty for Thursday Night into Friday


Full model: http://www.dmi.dk/vejr/til-lands/vejrkort/

DOCARCH

Mod Note: Moved a number of posts over to the other thread.

No matter how busy the other thread is, need to keep this one clear for technical discussion only, so everybody can easily reference.

Northernmost extent of the precipitation appears to be sometime during early Friday according to the 6Z GFS.

Daniel2590

GFS out to +102h

HIRLAM wants to drive it further north than the GFS.

cherryghost

HIRLAM is meltdown territory countrywide! 48 hours acc (most coming Thurs eve into Fri):

Snowmaker

cherryghost wrote: »

HIRLAM is meltdown territory countrywide! 48 hours acc (most coming Thurs eve into Fri):

I think you'll find HIRLAM doesn't differentiate between precip types on their accumulated precip forecast. That's all snow up to +48h :-)

EDIT: Or it's just a poor choice of words and I misunderstood the use of the word 'melt' there?? :-)haha.

Akrasia

Looking like a lot of snow for the bottom 2/3 of Ireland on thursday evening into friday

munsterlegend

Met Eireann forecast for tomorrow just updated and Friday is momentous. I think Hirlam and Harmonie are on the same hymn sheet.


Tomorrow

Snow showers will continue on Thursday morning, though they may ease for a time. However later in the afternoon and evening blizzard-like conditions will develop across Munster and Leinster as heavy snow together with strong winds spread northwards. Daytime temperatures will stay around freezing. Strong easterly winds will reach gale force later in the day on east and south coasts.

Outlook

Thursday night: Heavy snow will extend northwards through the country during Thursday evening and overnight in driving easterly winds leading to blizzard conditions. Munster and Leinster will see the worst snowfall but all parts will get significant snow accumulations. Temperatures will range -1 to -4 degrees.

Friday: The snow will clear from the south of the country during the day but it may persist across more northern counties until evening. It will be another cold day with highest temperatures around 1 or 2 degrees but there will be a slight rise in temperatures to around 4 to 6 degrees for southern counties. East to northeast winds will be strong and gusty. Widespread frost on Friday night.

M.T. Cranium

It would be hard to make all this up without actually seeing it happen.

The snowfall now to mid-day Thursday could be significant before that storm arrives, so let's say conservatively 10 to 20 cm on the ground in many parts of the east and 5 to 10 near south coast before the storm begins.

Then also conservatively 15 to 30 cm from the storm event. You could add the two parts together and come up with 25 to 50 cm east and 20 to 40 cm south. Further north where there might not be much snow pre-storm, and the storm not as strong, 15 to 20 cm.

Strong winds will be setting in soon and they won't often let up until most of this snow has fallen. When weakened Emma is pulling away to the west, winds will weaken about the same time as the mixed precip on the south coast and snow further north taper off to drizzle or snow grains. (Friday night or Saturday morning).

There are weaker solutions still on the table, few of which would leave behind less than 15 cm of snow. There are also stronger, 200-year return type solutions that you could imagine if both streamers and storm max out. And why not, the uppers are near their limits, at some point we're going to have -15 C at 850 mb and 504 dm thickness. Those are both close to the limits around Ireland.

But personally I think it will end up being closer to the top end of the 25 to 50 cm range, not outside it, but some place higher up on eastern slopes of Wicklow might max out around 60 or 70 cm.

Cork presents a real challenge and here's what I would say for now -- heavy wet snow at times Thursday night into Friday morning, 10-15 cm accumulations in city, 15-30 cm some areas higher in elevation and mainly north/west of the city, changing to sleet or ice pellets, rain perhaps right along the outer coast, then back to all snow but weakening rapidly. End result, 10-15 cm saturated snow cover and a lot of ponding from slush.

We may get totally different looks from models later today though, just trying to fit a forecast to model consensus at this early stage.

Any chance of slight modification to the precipitation in the afternoon? The DP reading immediately to the east of Dublin has risen to -0.6 C according to the latest report.

arctictree

George Sunsnow wrote: »

It also progged yesterday’s front as sleet and rain and it was all snow and graupel

Not a flake of snow in Arklow last night
Not one flake and that’s likely to be the same today
Southern extent of activity is about kilcoole/greystones co Wicklow.
Anglesea shadow and welsh shadow
Straight easterly doesn’t work here

Dew point here is -9c though :O

Funnily enough, only a light dusting in Roundwood. Maybe 2 or 3cm. South Dublin seems to have scored a direct hit from the streamers. When its this cold, elevation doesn't seem to matter as much. Very cold here this morning, -3c at 9am when I was feeding the sheep. All water pipes and troughs now frozen solid. I'd say we'll have an ice day here today.