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

MJohnston

lucernarian wrote: »

Don't feel strongly on this but I'm inclined to disagree. We shouldn't place numbers on things without reasonable evidence to do so, right? Or are you talking about current reports and the like?

That's then an issue for the general thread, not for here - it's their lookout if they can't use their own sense.

Maybe mentioning trigger words like "downgrade" or "upgrade" is the bigger problem if any. Temperatures are themselves relative (and unfortunately for us, the differences in marginal situations like Friday are such that "colder" can mean going from +0.5 to -0.5 when the band arrives, completely changing the meteorological outcome. It ends up being disingenuous when there are cliffhangers to deal with.

Met Éireann get around this by issuing practically no forecast for Friday...

What I'm talking about is the "downgrade" type language - something that neither specifies an old estimate, or a new one, just a kind of doom word. Same with something like "18Z not looking as good as the earlier run" though, for example. People seem to take that as "it's all falling apart", and while, as you say, exact numbers are still a mystery, you can still provide context that helps others understand. Downgrade/upgrade or even better/worse are like shouting fire in a crowded room right now!

Sky King

stephenjmcd wrote: »

Any chance this could be put in basic terms. Don't know TAFs all that well

I'm a bit rusty at decoding them (havent done uit in a while) so i'm open to correctioin, but here's the jist attached

DOCARCH

Mod Note: Some posts moved/removed. Can we try and keep this thread non chit chat. Thanks.

And....in relation to TAFs....it was previously outlined that people posting TAFs should give a brief explanation/brief de-code.

lucernarian

MJohnston wrote: »

What I'm talking about is the "downgrade" type language - something that neither specifies an old estimate, or a new one, just a kind of doom word. Same with something like "18Z not looking as good as the earlier run" though, for example. People seem to take that as "it's all falling apart", and while, as you say, exact numbers are still a mystery, you can still provide context that helps others understand. Downgrade/upgrade or even better/worse are like shouting fire in a crowded room right now!

There's already one thread where we have to watch our step lest we inadvertently troll someone or kick off a mad discussion.

I notice there's no mention of problem words like "upgrade", "whiteout" etc. either. But there are charter rules to help prevent making vague/unsubstantiated statements, plus the announcement in the forum. And it's important that it go both ways, not just if someone leaves

And why should it be anyone's job or onus to provide more context to some random reader who may never have been here before? It's the technical thread for a reason. It's totally different if someone asks for an explanation on something, but as for people jumping to crazy conclusions? Nah.

MJohnston

lucernarian wrote: »

There's already one thread where we have to watch our step lest we inadvertently troll someone or kick off a mad discussion.

I notice there's no mention of problem words like "upgrade", "whiteout" etc. either. But there are charter rules to help prevent making vague/unsubstantiated statements, plus the announcement in the forum. And it's important that it go both ways, not just if someone leaves

And why should it be anyone's job or onus to provide more context to some random reader who may never have been here before? It's the technical thread for a reason. It's totally different if someone asks for an explanation on something, but as for people jumping to crazy conclusions? Nah.

You can obviously do whatever you'd like to do, I'm only making a small request that people here be mindful that there is now a substantial audience relying upon this thread for genuine weather information, and that audience will no doubt grow even more tomorrow.

Lumi

Mod Note

Posts with technical content relating to this event only please.
Keep your argument for another day/thread

Thanks

Oneiric 3

Estonian Hirlam 12z model for Thursday 18z.



Given this model's conservative and high standards for what constitutes 'snow', these blues (full snow) coming up over Ireland from that front are interesting. Pink donates wet snow/sleet, and is usually what is shown over Ireland under more normal circumstances.

Gremlin

Lots of talk (for obvious reasons) about the setup Thurs/Fri but I'd love to hear from the experts about the setup overnight tonight for example. The GFS is showing plenty of precip especially around the dublin area. But the current radar isn't filling me with joy.

sdanseo

12Z ECM is a thing of absolute perfection

Can’t share on mobile but continuous moderate snow from 15Z Thu to 15Z Fri clearing straight to clear skies without rain. This is SE of a line Galway to Belfast.

Certain red warning tomorrow if 00Z shows the same.

Barnaboy

Casualsingby wrote: »

Euro4 accumulations to 6am Thursday. Sweet spots for highest totals Westmeath, Offaly my interpretation winds so strong they blow showers away too fast from East and slow down over this area. Other sweet spot for highest total is around South Cork area. Large patches of no accumulations in South East.

I live directly under that dark pink spot in the midlands. I will let you know how accurate that forecast is!

munsterlegend

sdanseo wrote: »

12Z ECM is a thing of absolute perfection

Can’t share on mobile but continuous moderate snow from 15Z Thu to 15Z Fri clearing straight to clear skies without rain. This is SE of a line Galway to Belfast.

Certain red warning tomorrow if 00Z shows the same.

Its very similar to the 00z with the heavier precipitation up the east coast and unlike the GFS in that respect i think!

highdef

Gremlin wrote: »

Lots of talk (for obvious reasons) about the setup Thurs/Fri but I'd love to hear from the experts about the setup overnight tonight for example. The GFS is showing plenty of precip especially around the dublin area. But the current radar isn't filling me with joy.

For the past while, it had looked like nothing was going on in the Irish sea, going by radar images but if you had looked at the infrared satellite imagery, you would have seen that clouds were building but just had not got enough oomph to drop precipitation however in the past 15 minutes or so, radar is beginning to show that these showers are getting their act together.

Wow. Serious stuff if this came to pass IMO.

Gremlin

highdef wrote: »

however in the past 15 minutes or so, radar is beginning to show that these showers are getting their act together.

I assume that's down to the temperature gradient increasing as the sun sets and air temps drop?

lucernarian

I really expected a red warning for eastern areas for tomorrow, firstly for the windchill (maybe they have no criteria for that specifically) and more so for the snowfall expected along parts of the east coast by tomorrow night. Or do they want to "forecast" based on radar and flash alerts like the Met Office in the UK have?

The model output shows >12 cm tomorrow at areas below 250 metres, this is sufficient criteria for a red warning.

SleetAndSnow

To my eyes the latest ECM looks like pretty heavy consistant snowfall for both the south (Cork, Waterford etc) along with the east, with little to no rainfall after it passes. I can see a red alert for the south and east becoming a thing. Please correct if wrong!

highdef

Gremlin wrote: »

I assume that's down to the temperature gradient increasing as the sun sets and air temps drop?

Temperature over the sea is not changing by any measurable amount due to lack of sun. It's due to the air high above getting colder by the very nature that it is the very cold air arriving from Siberia.

But with regards to the temperature gradient, you are correct. It's just the reason for it that you are incorrect about.

aidanodr

SleetAndSnow wrote: »

To my eyes the latest ECM looks like pretty heavy consistant snowfall for both the south (Cork, Waterford etc) along with the east, with little to no rainfall after it passes. I can see a red alert for the south and east becoming a thing. Please correct if wrong!

I know you guys might not like apps, but I looked at the snow radar on Weather Channel app. It has Snow starting over a large area of Cork city and surrounds kicking off about 7:30pm and lasting until about 9:30pm. This on the money I wonder?

3 Screen shots for 7.30 .. 8.30 .. 9.30

Tues nite1.jpg

Tues nite2.jpg

Tues nite3.jpg

Villain

ECMWF Snow totals haven't changed much in 12z, although these charts should be taken with a pinch of salt, (get it )
https://twitter.com/CarlowWeather/status/968559341627412484

ninebeanrows

EC 12z is a strange one-

Keeps cold in initially but quite progressive thereafter and going by the spread for 850hPa temps from the 0z EPS it would certainty be in the top end of the ensembles suite from Sunday....so I personally am taking its evolution beyond T72hrs with a large pinch of salt.

highdef

aidanodr wrote: »

I know you guys might not like apps, but I looked at the snow radar on Weather Channel app. It has Snow starting over a large are of Cork city and surrounds starting at 7:30pm and lasting until about 9:30pm. This on the money I wonder?

3 Screen shots for 7.30 .. 8.30 .. 9.30

Tues nite1.jpg

Tues nite2.jpg

Tues nite3.jpg

In this particular instance, it may well snow in parts of Cork but it's still not very cold so probably won't stick except maybe on the higher parts.

Villain

Met Eireann precip:

https://twitter.com/meteireann/status/968570571754754048

policy75

is Emma definitely to pass on the East side of Ireland or could it be pushed up the West coast instead in which case the heaviest snowfalls could happen more westerly than easterly later this week?

SeaBreezes

aidanodr wrote: »

I know you guys might not like apps, but I looked at the snow radar on Weather Channel app. It has Snow starting over a large area of Cork city and surrounds kicking off about 7:30pm and lasting until about 9:30pm. This on the money I wonder?

3 Screen shots for 7.30 .. 8.30 .. 9.30

Tues nite1.jpg

Tues nite2.jpg

Tues nite3.jpg

Bang on for the start time

Donegal Storm

Looks like we might have lift off for streamer activity in the Irish Sea, a few distinct trains getting going.



Weak and scattered for now but should hopefully start to really pick up in the coming hours. Only had a couple of fairly brief showers here so far today but already have a covering of 1-2cm of powdery snow so encouraging for later

munsterlegend

policy75 wrote: »

is Emma definitely to pass on the East side of Ireland or could it be pushed up the West coast instead in which case the heaviest snowfalls could happen more westerly than easterly later this week?

The east and south east going on current charts is where the precipitation is going. Still should be plenty to go around provided Emma makes it as far north as predicted.

Periscal

How often does it happen that we have 100% of snow probability for 4 days in a row! That is one for archives!

GFS is delaying the mild incursion by each run for my area in co.Wicklow

Deank

Just an FYI for the Mods, there's something buggy with this thread.

Lads as you're moving posts from here into the event thread the two of them seem to merge for a bit, click on the last post for this thread and you're brought to the the general event thread, the only way to view this thread is to go to the last post on that thread then "shift F5"

ninebeanrows

As guessed. EC is a huge mild outlier from Sunday.

Not that it can be discounted but an unlikely outcome to say the least

policy75

is there a post to explain stratosphere, troposphere, arctic temperatures being out of sync, jet stream gone to sleep as a description of how we come to witness this weather event to help our TV3 weather 'experts'? Or is that an essay?