FI Charts ( T120+ onwards) Winter 2020 **READ MOD NOTE IN FIRST POST**

Nqp15hhu

Gaoth Laidir wrote: »

That's not true. The 850 level will not be raised at all.

For the Internation Standard Atmosphere (ISA), sea-level pressure is 1013 hPa and 850 hPa is at 1450 m amsl. This actual height varies greatly day-to-day, depending on both surface pressure but also mean airmass temperature. The colder the airmass the lower 850 hPa will be for the same surface pressure. For that time next Tuesday the GFS has 850 hPa at 1300 m in the south to 1400 m in the north.

Lifted index is meaningless in this case as convection will be limited to below 500 hPa. There will be plenty of low-topped convection (up to around 700-600 hPa) and steep low-lelvel lapse rates (around -18 °C at 700 hPa). Graupel and snow, but still some residual moisture at the very lowest levels could mean some melting at times.

Sorry, yes it is. You have posted soundings yourself that have shown that the 850hPa level does vary.

This is true and a direct result of changing air pressure. The 850hPa level is a pressure level after all.

Gaoth Laidir

Nqp15hhu wrote: »

Sorry, yes it is. You have posted soundings yourself that have shown that the 850hPa level does vary.

This is true and a direct result of changing air pressure. The 850hPa level is a pressure level after all.

...and airmass temperature. The colder and drier the airmass the lower 850 hPa will be (and vice versa).

Nqp15hhu

No.. increased geopotential height with increased air pressure.

Gonzo

just taken a look at this mornings ECM run, it is a very snow run indeed. However a large pinch of salt is required from next Wednesday onwards as the ECM keeps the lows running to the south keeping the colder air with us for several days longer than is predicted by the GFS and some of the other models.

This is their precipitation charts for the next week based on this mornings models. This evenings ECM run could look very different. Blue is rain and Green/yellow is sleet/snow.

Saturday see's showers heading into Leinster, could be a fairly miserable day if showers band together to form frequent bursts of cold rain.



Very little action is showing up for Sunday, it looks like the Irish sea may fail to get going on Sunday and we may have to wait till Monday for the action to start.

Snow showers get going on Monday and these will become more widespread



Tuesday will produce widespread snow streamers in off the Irish sea, particularly the northern half of Leinster. This is based off the wind direction with the longer sea fetch suiting Dublin to Louth. By Tuesday the wind direction could be slightly different and i'd expect this positioning to be adjusted a little bit.



From Wednesday everything is up in the air and from here large pinch of salt is required. This could easily revert to a milder solution with rain

The streamers in off the Irish sea may move north as the wind direction changes. A frontal system could engage with the south-west with rain turning readily to sleet and snow as it moves into the south-west.



This band of sleet and snow may move northwards and bring widespread snow to much of the country. The tracking of these lows will be very important as it will determine if we let the mild atlantic air back in or sliding lows keeping the cold going.



Milder air tries to get into the country later on Thursday with snow turning back to rain in many areas.



ECM goes for another slider low on Friday dumping sleet and snow across most of the country.

Kermit.de.frog

Some of those charts are from the 12z yesterday

average_runner

So are we looking at 2 inches or more for dublin?


Is it worth booking a day off to play with the kids in the snow on Tuesday

Stevieluvsye

average_runner wrote: »

So are we looking at 2 inches or more for dublin?


Is it worth booking a day off to play with the kids in the snow on Tuesday

Mrs said she's looking for 6 inches at least

carltonleon

Calibos wrote: »

...intense bands of precipitation on the lee side of the mountains or the upwind side??

So in terms of Bray nestled into the Wicklow and Dublin Mountains, does the orographic lift give the intense snow to the mountains...or...Kildare/Carlow. Or does it give the intensity to the upwind side of the mountains which would be Bray. Is the orographic friction slowing down the cells causing them to dump more on the upwind side??

It must be the former I assume because it feels like Bray always gets less than most areas not more even under a Streamer....or....is it the case that Bray should be in prime position in an ENE with a long Sea Track to Morecambe Bay in front of it and the Wicklow Mountains behind our backs for the Orographic lift.....but the problem is we hardly ever get an ENE wind and are instead usually in an Angelsey or IOM Shadow??

I thought you said explain it like you are 5 ... some bleedin' 5 year old you are with your orographic lift

Mr_A

Met Éireann on 'high alert' as snow expected next week

https://www.rte.ie/news/2021/0204/1195067-weather-snow/

carltonleon

Mr_A wrote: »

Met Éireann on 'high alert' as snow expected next week

https://www.rte.ie/news/2021/0204/1195067-weather-snow/

Interesting that the article says that 'Met Éireann has said it is on "high alert" for the second half of next week, as significant snow is expected.'
Especially as it seems it is nailed on for early next week but that from Weds it is very unclear

nacho libre

carltonleon wrote: »

Interesting that the article says that 'Met Éireann has said it is on "high alert" for the second half of next week, as significant snow is expected.'
Especially as it seems it is nailed on for early next week but that from Weds it is very unclear

It might lead you to believe the Chief Forecasters intuition is telling her it will go our way for once. She is also seeing info that we don't see. I just wonder in potentially impactful situations do the UKMO share their own data with Met Eireann?

Calibos

Things to do and people to see.

See you all for the 18z!!

Dazler97

average_runner wrote: »

So are we looking at 2 inches or more for dublin?


Is it worth booking a day off to play with the kids in the snow on Tuesday

I'd say so as with most easterlys Dublin is in the firing line, hard to tell what will fall exactly depending on the upper temps and sea temperature from streamers etc

Calibos

Calibos wrote: »

Things to do and people to see.

See you all for the 18z!!

No commitment.

Rebelbrowser

Just to be unorthodox and post a chart in the technical thread:pac: the 12z Arpege doesn't show the same level of cold out to Tuesday morning as the 6z GFS. We in the SW in particular barely joining the party. Can't see streamers kicking off down here anyway with those uppers.



Think the low sliding under on Tuesday morning is holding temps up. More cold might travel west once it passes....



Curiously, it has streamers stretching to Co. Clare though!

TheMilkyPirate

Cold seems to be further north on the 12z

Villain

At a quick look the UKMO looks better but GFS goes other way.

+144 charts here

GFS:


UKMO:

ninebeanrows

Heaps and heaps of snow for England on that UKMO, the streamers coming in from the North Sea are going to be immense.

Over here the flow isn't quite as unstable

sicknotexi

Villain wrote: »

At a quick look the UKMO looks better but GFS goes other way.

+144 charts here

GFS:


UKMO:

I know which one my money would be on.

TheMilkyPirate

UKMO much better than the GFS keeps the low further south and extends the cold until late in the week.

Surely the UKMO is better at this range? (<120) or is that just hope casting from me

TonyMaloney

Icon at +144

Looking good.



Even better at 180+

bazlers

Remember MTCs forecast??

TheMilkyPirate

ICON more along the lines of the UKMO as well

munsterlegend

TheMilkyPirate wrote: »

UKMO much better than the GFS keeps the low further south and extends the cold until late in the week.

Surely the UKMO is better at this range? (<120) or is that just hope casting from me

Not hopecasting but will see what ECM brings.

TonyMaloney

TheMilkyPirate wrote: »

ICON more along the lines of the UKMO as well

The second low which the GFS has killing us, slides under instead and the ICON has it giving a glancing blow of precip.

Would fall as cold rain in Cork, and heavy snow for the rest of the South. Long way away though.

sicknotexi

Obviously that GFS 12z is a dreadful run but I'm delighted with the UKMO and ICON looks good too.

munsterlegend

TonyMaloney wrote: »

The second low which the GFS has killing us, slides under instead and the ICON has it giving a glancing blow of precip.

Would fall as cold rain in Cork, and heavy snow for the rest of the South. Long way away though.

Do you mean cork city on the coast or all of cork?!

KingdomRushed

GEM is rolling out too and looks good.

leahyl

munsterlegend wrote: »

Do you mean cork city on the coast or all of cork?!

No doubt Mallow will still get in on some of the action while Cork City will be drowning in freezing cold rain

nacho libre

It would be good if the ECM was similar to this rather the GFS. I'd like to think that low out west would disrupt.