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

kod87

GFS has it all over by saturday morning, any precipitation will be rain by then, disapointing considering that this time yesterday the models were showing a more prolonged cold spell. If the GFS is correct (a big if) then this will be short and sweet.

Kermit.de.frog

UKMO going all out snow event

nacho libre

kod87 wrote: »

Not very impressive it has to be said, but i don't normally pay much heed to snow accumulation cahrts

Neither do i- especially when streamers are involved. Places like Norfolk and parts of Kent could see 15- 20 cm by the end of the week due to them. Maybe parts of Ireland too;)

patneve2

Time to start looking at next week more closely. Late Tuesday/Wednesday holds enormous potential for the E Coast. -12 to -15 uppers, long ENE fetch and most importantly the wind doesn't look excessively strong. If current charts were to verify I should get my 10cm on Wednesday, with larger amounts about 10 to 30 km inland. Snowfall occurring at a temp of -2 at times. Thursday doesn't look as favourable due to a stronger wind, but this might change. Not even thinking about the Friday low yet.

Kermit.de.frog

The temperatures in the Irish sea on Wednesday night.

Kermit.de.frog

patneve2 wrote: »

Thursday doesn't look as favourable due to a stronger wind, but this might change. Not even thinking about the Friday low yet.

Why do you think that?

If the Irish sea temperatures were 4 or 5c maybe.

Not so.



The wind could be the same speed as on Neptune and anything that comes off the Irish sea would be snow.

patneve2

Kermit.de.frog wrote: »

Why do you think that?

If the Irish sea temperatures were 4 or 5c maybe.

Not so.



The wind could be the same speed as on Neptune and anything that comes off the Irish sea would be snow.

I agree, it would snow at -200 meters with these uppers. What I am trying to say is that at times a very strong wind isn't good for convection. Showers find it hard to form over sea and tend to blow over quickly. The north easterly with -13 uppers in 2013 is an example of this...and yes obviously that was a much smaller event. I may be completely wrong about this and anyways in any case we are going to get plastered over the next few days. Major major event incoming.

M.T. Cranium

With the stronger winds though you could have double streamer action that starts in the North Sea, partially unloads across a narrow part of northern England then enters the Irish Sea ready to reload, moderate to strong winds are not known to be a hindrance to lake effect snowfall but just organize the streamers into narrower bands sometimes.

I agree the pre-Friday period has lots of potential and then it seems almost 50-50 that snow on Thursday night into Friday morning could hold on against this first mild wave. I think we all know this spell will likely break down either this way or through some sort of long slow relaxation of the block (2013 never really broke down if I recall, it just slowly transitioned to average through April).

Anyway, lots of questions for the "king" to address at 0600-0700h. Arpege has gone its full 102h and only brought the low to northwest Spain with no real indications of a northward trend, looks more like it's heading for France on the last two panels.

M.T. Cranium

It strikes me that a solution not shown on any particular model but which could be a weighted average would be a tight loop of this low south of Ireland around 50 N and then for it to head east into the Channel. That could be a best case scenario for snowfall (or worst case scenario for snowfall impacts).

Worth noting -- good streamer formation over Baltic Sea in parcel of air mass roughly equivalent to Tuesday Irish Sea, streamers are nearly continuous and making plenty of progress inland in northern Germany tonight.

Kermit.de.frog

M.T. Cranium wrote: »

With the stronger winds though you could have double streamer action that starts in the North Sea, partially unloads across a narrow part of northern England then enters the Irish Sea ready to reload, moderate to strong winds are not known to be a hindrance to lake effect snowfall but just organize the streamers into narrower bands sometimes.

I agree the pre-Friday period has lots of potential and then it seems almost 50-50 that snow on Thursday night into Friday morning could hold on against this first mild wave. I think we all know this spell will likely break down either this way or through some sort of long slow relaxation of the block (2013 never really broke down if I recall, it just slowly transitioned to average through April).

Anyway, lots of questions for the "king" to address at 0600-0700h. Arpege has gone its full 102h and only brought the low to northwest Spain with no real indications of a northward trend, looks more like it's heading for France on the last two panels.

Going for some decent shower activity off the Irish sea too

Kermit.de.frog

GFS control run has up to 36 hours of continuous snowfall pretty much nationwide away from south facing coasts on Thursday night and Friday/night.

M.T. Cranium

We are writing an exam that only nature can grade, and the only reward for passing is to write another one.

igCorcaigh

Kermit.de.frog wrote: »

GFS control run has up to 36 hours of continuous snowfall pretty much nationwide away from south facing coasts on Thursday night and Friday/night.

Kermit, can I please ask you, from that same GFS run, how long before than snowfall turns to rain? I'm thinking of the southern counties; are we looking at a slushy mess or a more gradual thaw?

Strictly a literal interpretation of this run that is, not a projection.

Kermit.de.frog

igCorcaigh wrote: »

Kermit, can I please ask you, from that same GFS run, how long before than snowfall turns to rain? I'm thinking of the southern counties; are we looking at a slushy mess or a more gradual thaw?

Strictly a literal interpretation of this run that is, not a projection.

The operational GFS run currently would give quite a few hours of heavy snowfall to southern coastal counties on Friday but is progged to turn back to rain here briefly before the main band of snow moves north.

Rain follows for Saturday night.


That's the shortest interpretation for your location. All subject to change.

kod87

The ECM brings the low pressure right over the country at 144 hrs but crucially the uppers remain at -4 to -6, cold air winning that battle

Kermit.de.frog

ECM has, what seems to me, to be a major snow event for the end of the week. Similar to UKMO and better than GFS in that respect.

To paraphrase - "the kettle is on the boil"

kod87

I like the ECM run for next weekend, lots and lots of potential

M.T. Cranium

All of these solutions can only be taken as approximate at this point, but the ECM scenario looks like a prolonged snow event that just tapers off to drizzle and near freezing temperatures rather than a heavy rain and thaw.

munsterlegend

M.T. Cranium wrote: »

All of these solutions can only be taken as approximate at this point, but the ECM scenario looks like a prolonged snow event that just tapers off to drizzle and near freezing temperatures rather than a heavy rain and thaw.

Does that not tie in with Met office uk thinking as well?

Villain

ECMWF OP on milder side

JCX BXC

kod87 wrote: »

GFS has it all over by saturday morning, any precipitation will be rain by then, disapointing considering that this time yesterday the models were showing a more prolonged cold spell. If the GFS is correct (a big if) then this will be short and sweet.

Not completely, has another reload with another countrywide band of snow Wednesday week.

Artane2002

This is what the ICON 06Z is showing for Friday.

downwiththatsor

Artane2002 wrote: »

This is what the ICON 06Z is showing for Friday. Credit to radiohead on Netweather. Sorry about the link, I'm not sure how to post the picture directly on phone

ThaitaniumM

GFS 06Z just rolling out now. It seems we have slightly cooler uppers and hint of that low just a slight fraction to the E. Also a reload of the cold into FI too.

Artane2002

Looks like the low is further southeast on the GFS 06Z.

dacogawa

Looking at the GFS if there is some sort of thaw from that low that could push up on Friday/Saturday there could be another issue with the very high Spring Tide (4.51m in Dublin on Sat, Friday 4.48m) and winds.

Very unlikely but I've said before it would just take 3 things timed together to turn Grand Canal Dock into Venice (spring tide, big low & lots of rain before) I've seen it over the edge of the Liffey with less going on.

Something worth keeping in mind, we don't need a big thaw and a spring tide at the same time...



I still don't trust the GFS above the ECM so probably nothing to see here

JCX BXC

Current GFS would be a very slow thaw if anything, although how much will a foot of snow thaw in a temperature of 1c

JanuarySnowstor

dacogawa wrote: »

Looking at the GFS if there is some sort of thaw from that low that could push up on Friday/Saturday there could be another issue with the very high Spring Tide (4.51m in Dublin on Sat, Friday 4.48m) and winds.

Very unlikely but I've said before it would just take 3 things timed together to turn Grand Canal Dock into Venice (spring tide, big low & lots of rain before) I've seen it over the edge of the Liffey with less going on.

Something worth keeping in mind, we don't need a big thaw and a spring tide at the same time...



I still don't trust the GFS above the ECM so probably nothing to see here

Glad you mentioned this.
Cork always suffers with high tide and Easterly winds. Could become a secondary issue

Artane2002

Here is what is shown for Saturday morning by the GFS 06Z. Correct me if I'm wrong but this looks like an all snow event in Ireland to me? The South is in -4c uppers while the far north has -6c uppers.

LEIN

Artane2002 wrote: »

Here is what is shown for Saturday morning by the GFS 06Z. Correct me if I'm wrong but this looks like an all snow event in Ireland to me?

Hopefully, it will not drag air up from the med or it cloud be curtains for some.