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

Kermit.de.frog

Deleted User wrote: »

Close up of that +96 hrs chart. Looks decent for the midlands, east and north for me.

Important to remember we don't need particularly low temperatures at 850 level in situations like this for snowfall.

So long as the layers below are cold enough, and by all accounts they should be, it's not as important as with an Atlantic flow.

dacogawa

heffoo wrote: »

Evelyn ramping blizzards for Thursday night just there

And for Friday morning "battle ground" was used also "more like 1982 then 2010"

George Sunsnow

Quality control?
How can a forecast of rain be allowed out and no mention of uncertainty when the emergency group are meeting and emphasizing blizzards
It beggars belief

munsterlegend

George Sunsnow wrote: »

Quality control?
How can a forecast of rain be allowed out and no mention of uncertainty when the emergency group are meeting and emphasizing blizzards
It beggars belief

It actually does beggar belief. I thought Evelyn was much less confident re Thursday/Friday on the news but that reflects the forecast I suppose.

mickger844posts

The ECM outcome looks very messy to me especially with three lows South West of us at 120hrs. Something not right there.
Not model related but ridiculous having the Eagle playing the whole thing down this week and Evelyn ramping Blizzard conditions. They should be all sending the same message whether we like it or not.

cian1500ww

Position of the low for Thursday and Friday according to ME's 6pm forecast this evening:

George Sunsnow

Franz Von Peppercorn wrote: »

Where’s the rain forecast?

The 6pm radio forecast presented by John eagleton
Let’s leave it at that in this thread and come back to it Thursday
There are many charts on this thread discussed at odds with the eagles forecast
The situation is not resolved

DOCARCH

Mod Note: Can we keep the chat stuff to the chat thread. Thanks.

Gaoth Laidir

Dewpoints getting pretty low now in the east.

Casement -7.2
Johnstown Castle -7.1
Dublin Airport -6.8

Down mainly in the range -8 to -10 over England.

Gaoth Laidir

We can see the higher cloudtops (green colour, ~6000 m)) out over the North Sea at the moment, compared to much lower tops further west over us (yellow, ~2000-3000 m). Heavier showers should be getting into eastern UK in the next few hours.

So far today there have been plenty of snow reports in England but there has been no real accumulation as of yet (F = patchy cover).

pauldry

I think the models will trend towards the end of this by Friday.

Wednesday and Thursday look extreme by all accounts and I think some people will actually be pleased to see milder weather though i think the charts are consistently showing blue so it will be no better than 4 to 7c

The Friday chart is very borderline so it may be just rain in South and sleet and snow for the rest of us. Hence Met Eireanns conflicting forecasts. They have a hard job. The will be closer to correct than the most of us bar about 10 people here

ninebeanrows

Interesting that 12z EC is one of the slightly less old runs through Friday night / Saturday

The median t2m on the EPSgram is around 1.5/2deg lower.....0/1 degrees instead of 2/3 on the Op.....interesting...

DOCARCH

The 'good stuff' now appearing on the UKMO radar in the North Sea.

https://www.metoffice.gov.uk/public/weather/observation/map/#?map=Rainfall&zoom=5&lon=-4.00&lat=55.01&fcTime=1519631700

Gaoth Laidir

Imagine if these depths came to pass come Friday evening. The ECM says yes.

sdanseo

Gaoth Laidir wrote: »

Imagine if these depths came to pass come Friday evening. The ECM says yes.

And you say that's based on 10x multiplier?

What multiplier is most likely from the low pressure attack?

Gaoth Laidir

sdanseo wrote: »

And you say that's based on 10x multiplier?

What multiplier is most likely from the low pressure attack?

I would imagine higher than 10 starting off, but heading more towards 10 and below later on as the snow becomes wetter. Either way, Friday's looking interesting!

BLIZZARD7

sdanseo wrote: »

And you say that's based on 10x multiplier?

What multiplier is most likely from the low pressure attack?

Probably in and around that, alot more marginal than the stuff midweek so won't be quite as high a multiplier. I may be wrong on this though.

Gaoth Laidir

More snow grains up to 11 pm in the TAF for Casement. Eastlery wind, 10 knots, broken cloud at 3500 ft.

TAF EIME 262000Z 2621/2706 09010KT 9999 BKN035 TEMPO 2621/2623 -SHSG=

Snowbie

Thursday night/Friday event is well inside the reliable timeframe but expect a few more wobbles in track and heart palpitations between now and Wednesday evening 12Z when it should be locked in by then, somewhat.

Storm Emma is apart of a complex area of low pressure system and its going to be tugged by the other series of lows within the system. It can advance Nw of Ireland, it could slide further into the UK keeping us within an Icy and low Dp grip and a possible reload of an E’ly or just move direct north over the island with maritime mix in the wake.

Either way, the prospect of snow and heavy snow looks indeed likely at this stage but for how long is still undetermined. Its either going to turn to a slushy sleety mess in the wake of the front of perhaps stall over the island and keep us in the colder airmass and dump a ton of snow on us which is why its bring referred to 1982 which was a stalled front over the eastern half of the island for those of us who remember that spectacle. 2010 indeed snowy was a more organised potent bands of streamers that affected the entire island at times but will stand out on how lengthy and record breaking it was for its cold.

Having said all that, expect more wobbles over the next couple of days wrt this event Thursday night, comparing runs on Wednesday 12Z will still differ from each of the NWP models I’d expect to nail track. Its just unfortunate we are a little dot in a big Ocean when track can be key to either a historic snowfest or a complete let down with a quick moving band of heavy frontal snow with less cold air in tow.

Enjoy the heavy snow showers from tomorrow evening and Wednesday in the meantime, they may give appreciable depths in places that could be classed as a good winter. Who knows, we may see a 1982 and a 2010 this week, the potential is there....

Interesting and exciting times ahead.

ninebeanrows

Just seen the latest EC EPS plumes and definitely a shift to more colder options from the 00z suite. Very interesting times now.

D9Male

Are you talking about Friday and Saturday only, or beyond?

sdanseo

Weathercheck wrote: »

Just seen the latest EC EPS plumes and definitely a shift to more colder options from the 00z suite. Very interesting times now.

Despite the lower uppers, ECM Snow line stays at sea level over the whole country into Friday morning.

Retreats to a line from Galway to Dublin by evening.

Nabber

Some tasty looking charts for for the days after


GEM predictions looking colder than the rest.
The position of that low by 50 miles will make some hell of a difference.
We could see up to 16c difference in uppers between NE and SW.

Very interesting times ahead.

ninebeanrows

EURO4 has nice streamer tomorrow night / Weds morning stretching from Dublin to Clare!

sdanseo

Nabber wrote: »

Some tasty looking charts for for the days after

GEM predictions looking colder than the rest.
The position of that low by 50 miles will make some hell of a difference.
We could see up to 16c difference in uppers between NE and SW.

Very interesting times ahead.

Looking more and more like the "beast" in the sense of -16, -18 uppers is not much more than a Jack Russel at this stage though. Nothing is going for a full on reload although of course that doesn't at all mean no more snow.

cherryghost

We dont need such high uppers to guarantee snow Friday morning, -4 will be enough for most areas based on DP

Snowbie

cherryghost wrote: »

We dont need such high uppers to guarantee snow Friday morning, -4 will be enough for most areas based on DP

As a decent enough guidance for sea level, 850mb temps of -10C for coastal areas, -8C inland is good for snow, DAM of 528 and lower etc.
850mb temp higher than this (towards 0C), the wedge of warm air riding over colder air will have uppers increasing which will head into freezing rain territory even when air temps at surface are below freezing.

Kermit.de.frog

Northerly extent on 18z ICON for Friday before snow slips away south

sdanseo

Kermit.de.frog wrote: »

Northerly extent on 18z ICON for Friday before snow slips away south

Not sure it's slipping much?

ninebeanrows

Yep DM - a beautiful ICON