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

cherryghost

AFAIK HIRLAM and HARMONIE literally do sing of the same hymn sheet

Edit:

Since 2006, the HIRLAM cooperation shifted its focus to the development of meso-scale (convection-permitting) numerical weather prediction system (HARMONIE) through close collaboration with the ALADIN consortium (led by Meteo France) and the ECMWF (European Center for Medium-range Weather Forecasting). The HARMONIE forecast system is the main operational weather forecast system at HIRLAM weather services with a typical grid resolution of 2.5 km

munsterlegend

Its interesting that since earlier Met Eireann have removed references to Rain and Sleet in their update which I presume means they fell it will fall as snow mostly. I hope the models don't backtrack!

Mullaghteelin

[Deleted User] wrote: »

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.

It tends to shoot up in the showers and down again in any respite between them. It was above zero at times during the night already.

Oneiric 3

Elmer Blooker wrote: »

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!

Is that a smile I see Elmer :eek:

Accumulation of radar returns over the last 24hrs showing where most of the showers fell over the last 24hrs:

sdanseo

GFS snow depths going for national cover as below.

In real time, this chart is only showing about 10-20% of actual amounts for some places and predicted same. Do the maths.

Gaoth Laidir

Sun's out now in Talalght after a heavy snow shower. I measured 11 cm at 10 am and 12 cm at 11 am. Casement was down to 14 cm at 10 am but probably back up now at 11 am. There is, however, decent melting going on as I type.

The coldest cloud tops of around -42 °C are now in over the east. That should continue for the rest of daylight hours, so more on and off showers, with accumulations up and down.

https://weather.us/satellite/ireland/top-alert-5min/20180228-1050z.html

Thursday? Well, who knows? I like the way the ECM seems is still progressive in pushing the snow northwards and has a good 24 hours of continuous dynamic snowfall for much of the ecntral band of the country. I can't see 40 cm depths at low levels but certainly Casement's 27 cm of 2010 could be beaten.

downwiththatsor

Status Red Munster Leinster issued 11am

Deank

Looks like streamers continuing to bubble up, giving some action here in Kildare at the moment, near whiteout.

Gaoth Laidir

Anyone have the hourly precip totals for Casement this morning? From midnight to 6 am 0.3 mm liquid equivalent fell, and that dumped 16 cm of cover, which gives an average ratio of over 500!, which can't be right. But from 4-5 am, 10 cm of snow fell, so it we had that hourly precip total then we can see exactly what the ratio is.

Of course, it could be that the rain gauge could be frozen, but that's unlikely as they're heated to melt all precip.

sdanseo

Just took some more scientific measurements with a ruler, Malahide 2km from the sea & mostly graupel.

4.5 to 6 cm on flat surfaces - drifts up to 11cm against walls

>12cm (only ruler I had, a set square, got buried entirely) on grass. Probbaly close to 15cm.

Snowbie

ME have just issued Staus Red warning for the Blizzard Thursday evening covering Munster and Leinster

Donegal Storm

Gaoth Laidir wrote: »

Sun's out now in Talalght after a heavy snow shower. I measured 11 cm at 10 am and 12 cm at 11 am. Casement was down to 14 cm at 10 am but probably back up now at 11 am. There is, however, decent melting going on as I type.

Could also be a case of snow compacting more so than melting? Lots of hail and snow grains here so far today which has compacted the fluffy stuff from this morning. It's been near continuous all morning here yet only a couple of cm deeper than at 7am

Oneiric 3

Gaoth Laidir wrote: »

Anyone have the hourly precip totals for Casement this morning? From midnight to 6 am 0.3 mm liquid equivalent fell, and that dumped 16 cm of cover, which gives an average ratio of over 500!, which can't be right. But from 4-5 am, 10 cm of snow fell, so it we had that hourly precip total then we can see exactly what the ratio is.

Of course, it could be that the rain gauge could be frozen, but that's unlikely as they're heated to melt all precip.

Best bet is to email Met Éireann. Ogimet/Meteociel/Weatherobs only seem to report prep ever 6 hours which is of no use to anybody.

Oneiric 3

Just to keep it in the archives. Most stations below freezing as of 11am:

Gremlin

It seems then flow has changed to 090 now which would put the focus of the streamers on North Co Dublin Meath and Louth.

MidMan25

Oneiric 3 wrote: »

Just to keep it in the archives. Most stations below freezing as of 11am:

Roches Point at -2 is a rare thing at any time of the day/night. What with it being right on the south coast!

Gaoth Laidir

Donegal Storm wrote: »

Could also be a case of snow compacting more so than melting? Lots of hail and snow grains here so far today which has compacted the fluffy stuff from this morning. It's been near continuous all morning here yet only a couple of cm deeper than at 7am

There will be some compacting alright, but there is also melting taking place on exposed surfaces.

Reckless Abandonment

Irish sea gone very quite, Euro4 shows no more till late tonight. That front/end of streamer train coming of UK is killing convection,

thomasj

Netweather is showing a fair bit of activity still in the Irish sea?

And here in blanch still a very dark sky

Oneiric 3

'Lake effect'



Had to reduce image size due to file size limits.

KingdomRushed

Irish Sea has gone quietish now, wonder how long until it peps up again? I see some models like HIRLAM show it fairly placid until after dark this evening

ZeroSum76

Oneiric 3 wrote: »

'Lake effect'

Had to reduce image size due to file size limits.

Great image! You can kind of make out the Isle Of Man/Anglesea/Wales shadow effect. This has proven to be very significant as some areas on the East coast have had little/no snow as yet.

Oneiric 3

ZeroSum76 wrote: »

Great image! You can kind of make out the Isle Of Man/Anglesea/Wales shadow effect. This has proven to be very significant as some areas on the East coast have had little/no snow as yet.

Unfortunately the image size does it no justice. Will try to work out how to keep original size while reducing file size later. There must be a way!

red_bairn

Oneiric 3 wrote: »

Unfortunately the image size does it no justice. Will try to work out how to keep original size while reducing file size later. There must be a way!

You can change by the quality to reduce the size.

Streamer activity beginning to pep up again in the Irish sea north of Wales. Seem to be heading in a WNW direction.

http://www.met.ie/latest/rainfall_radar.asp

q85dw7osi4lebg

Winds appear to beyond 90 degrees now.

Gaoth Laidir

This morning's action was from a northeasterly, but it's swung easterly now and and I'm sitting in sunshine here in Tallaght courtesy of the Wales shadow and slighltly warmer upper pool. I don't expact much real activity for areas south of Dublin airport this afternoon, but north of it still in for a pasting as 500 hPa temperatures get down to -45 °C in north Leinster and southeast Ulster. Meath, Louth, Down, Armagh and Monaghan going to do well.

gluppers

What's the Wales shadow?

q85dw7osi4lebg

Much bigger fetch on these next few streamers in an hour or so.

Gaoth Laidir

gluppers wrote: »

What's the Wales shadow?

It's the reduction in showery activity due to the much shorter sea track between Wales and the east coast when the wind is easterly. Less sea track means less time for showers to form. North of Dublin has a much longer sea track all the way over from Blackpool (see chart above).