Cold Snap, T0-180Hours Only

Musicman2000

The UKMO fax charts have stuck to their own raw output, That would put an end to the cold spell Friday.

Trotter

From memory in December 2010 and February 2011, it was this kind of setup that gave the south east the few serious dumpings that stayed on because of the temperature. If I remember right, we had no sustained snow, just 3 or 4 very heavy prolonged showers that didnt melt. Those streamers are our key to snow and with the Irish sea temps not getting a chance to drop off gradually, I think we might be in luck.



Even if thats total rubbish, didnt it sound really like I knew what I was at!?

Sponge Bob

Cold but that is all.

pistolpetes11 wrote: »

The Cold is further West again !

GFS 18z @ 96 hr



GFS 12z @ 102 hr

If there are no streamers off the Irish Sea under that then there will be nowt other than cold.

Look at the Precipitation value at that the same time as those cold uppers.

A very dry atmosphere is shown in the GFS from late Tuesday to late Saturday.

JFKIRELAND

OK, GFS or ECMWF? I ask as the ECMWF 12z today in my opinion was useless for anything except a couple of hard frosts between now and Saturday.
The GFS looks much better, are they on to something that the ECM is not?
Btw, what would be considered FI at the moment - 72hrs?

John.Icy

Streamers form on a NE wind. Hence the IOM shadow. We're looking at a weak SE/E flow, not enough sea track for snow trains and pressure abit to high to sustain alot of moisture. Don't expect more than a few brief flurries, unless we get really lucky!

pistolpetes11

Sponge Bob wrote: »

Cold but that is all.



If there are no streamers off the Irish Sea under that then there will be nowt other than cold.

Look at the Precipitation value at that the same time as those cold uppers.

A very dry atmosphere is shown in the GFS from late Tuesday to late Saturday.

True ,

And there would no be much of a chance of streamers off this wind direction either,

(Correlates to the precip chart posted above)

Trotter

pistolpetes11 wrote: »

True ,

And there would no be much of a chance of streamers off this wind direction either,
(Correlates to the precip chart posted above)

But wouldnt that be an ideal setup for streamers for us on the South East coast?

Su Campu

I would imagine the south and southeast coasts will see the best of any flurries that do form over the next few days. Relatively warm upper levels will prevent deep convection, and although we will see vigorous low level convection, the drier airmass may preclude widespread showers. Those that do form should extend to around 12-15,000 ft. With the larger sea track in the east/southeasterly flow, areas from say Cork to Wexford should see the heaviest. Wales may get in the way for much of the east, but maybe northern Irish Sea coasts will see something.

ninebeanrows

UKM Fax chart is really a bold call.

The 18z GFS Ensembles are very very different.

blackius

Trotter wrote: »

But wouldnt that be an ideal setup for streamers for us on the South East coast?

Yes

Sponge Bob

Be nice to look at that Fax wouldn't it. ??

BLIZZARD7

Ok - While I cant see 40cm of snow in Dublin/Wicklow from streamers- I do see the potential for smaller streamers, I know its a shorter sea track than a direct north-easterly but I still reckon some part of the east is going to get a fair bit by the end of the week if the GFS is right. Also the sea track seems very long for the Co.Down *(as trogdor has shown in chat thread-this could also be case for Louth/Dublin/Wicklow/wexford if we get a sse wind)* area from tomorrow til thursday- possible dumping there from streamers or am I barking up the wrong tree?

On friday winds will be coming from the north-east and there is definitley snow potential for louth/Dublin/Wicklow/Wexford for a time.








And I see the UK met have gone with the UKMO raw output for their fax charts-
The only reason I am dubious of this been correct is that the 18z Gefs show absolutely zero support for the fax chart over france- not one member has the breakdown happening that quickly. I think the UKMO is understimating the strength of the siberian/scandi high. All will be revealed in the morning.


Im also liking the long-term trend for the complete destruction of the polar-vortex and increased northern blocking for rest of feb. stratosphere very supportive of northern blocking and the AO is forecast to take a huge hit. Hopefully another reload is coming in a week or two's time.




Dan

darkman2

UKMO 96hrs




GFS ensemble mean 96hrs (18z)




Now this is a pickle. If it were not for the distortion of the very progressive UKMO it would be much easier with a blend of the GFS/ECM at this range. 00z's are going to be absolutely vital. We will know later today what way this is going definitely.

Still a chance of us holding on to colder air through next weekend or the Atlantic bulldozing the setup before then. Impossible to call at this stage.

Sponge Bob

I thought the 96hr UKMo FAX that I posted earlier was most peculiar. Smacks of a massive row in the office and a come back tomorrrow to discuss it all again. And there have been tweets since.

I am attaching it for future reference because the link above will change soon. There may well be a good story in this after the event.

nacho libre

More tweets from Ian Fergusson:


Ian Fergusson @fergieweather
@Nick_Durham ie., albeit they include GFS prog in their briefing, they are inclined towards the temp breakdown of block, not GFS longevity..


Ian Fergusson @fergieweather
@Nick_Durham not allowed to post their graphics to illustrate the point! But their latest modified (stress modified) GM v different to GFS.


Ian Fergusson @fergieweather
@SJC2331 I suspect it's too progressive; equally GFS: too stubborn!! UKMO GM has been modified anyway to slower consensus. So middle ground.


Nick_DURHAM @Nick_Durham
@fergieweather modified on the basis of experience/knowledge/the human factor?
Ian Fergusson @fergieweather
@Nick_Durham all those, by Exeter ops staff. Remember, only the raw output goes to free websites & it's often miles off the modified version

whiteandlight

Sponge Bob wrote: »

I thought the 96hr UKMo FAX that I posted earlier was most peculiar. Smacks of a massive row in the office and a come back tomorrrow to discuss it all again. And there have been tweets since.

I am attaching it for future reference because the link above will change soon. There may well be a good story in this after the event.

I'm slowly getting used to the charts but the fax ones are beyond me yet. Any chance you could explain why it would be causing a massive row in the office. Sorry for interrupting the model discussion but I'm trying to learn from all you intelligent/experienced posters in this thread. Tyvm

nacho libre

Musicmental85 wrote: »

I'm slowly getting used to the charts but the fax ones are beyond me yet. Any chance you could explain why it would be causing a massive row in the office. Sorry for interrupting the model discussion but I'm trying to learn from all you intelligent/experienced posters in this thread. Tyvm

because it suggests that opinion is divided on their own output- it could be some forecasters are quite dismissive of what it suggests, while others back it. there is an indication of the confusion in the tweets I posted above. It's plausible that some senior forecasters think it's too progressive, while others feel it will play out as the fax chart suggests.

patneve2

Striking analogy to the 1956 February cold spell, exact same dates also :eek: was reading about it on another forum

Sponge Bob

Musicmental85 wrote: »

I'm slowly getting used to the charts but the fax ones are beyond me yet. Any chance you could explain why it would be causing a massive row in the office. Sorry for interrupting the model discussion but I'm trying to learn from all you intelligent/experienced posters in this thread. Tyvm

Good question . I will give you MY opinion.

The UK Forecast is the front line. Ireland is behind that front and out of reach of the heavy artillery at present. Our forecasters can relax a bit.

A majorly wrong call on what is actually incoming to the UK will affect all of reputations, careers and funding for research. We can get it wrong around here on Boards and it will not have financial consequences for anybody. Well maybe for Wild Bill but so what about that.

However the UKMO Fax is probably the oldest and most 'venerable' of all forecast charts and comes with an aura of legend. And the Fax is where the humans take over from the models and call it. If the models beat the Fax there shall be no more Fax. Only model output. End of an era.

The 96 Hour above is so different from every other model I have recently seen that it looks like a minion was instructed to bang it out so that none of reputations, careers and funding are affected. But they will resume their deliberations tomorrow.

HTH!

Danno

Pah, its still 5c here and the Atlantic is the king this year, apart from a few flurries and disturbance overnight snow on Friday night, you can write off this week for snow. We need a greenie high and a scandi vortex for proper winter on this emerald isle. if it dont all reload next week, forget this winter apart from perhaps a northerly come feb 24th to 27th. end of. why you may ask? over 25 yrs watching winters and have seen it all before. there is always next year! sorry to sound so cruel, but its true.

mickger844posts

GFS 0Z first impression is that the colder uppers are about 100 miles further East on this run compared to the 18z. Lets see how the rest of the run pans out.

mickger844posts

GFS 0Z is a disappointing run in the long term. Cold and frosty for a few days with maybe a few snow showers in the East/South East then back to mild by Saturday evening.



UKMO 0Z an upgrade on their previous run with the cold further East and deeper. So basically the roller coaster continues

ninebeanrows

Pretty poor runs this morning especially the ECM.

However, again the ECM output is at the mild side of its ensembles.

Disappointing though is the lack of real cold air encroachment in the early timeframes, however there remains a decent % of the ensembles members going for a much slower progression from the Atlantic and much snowier breakdown than the OP. What some do is eject a shortwave SE but the High Pressure over Scandy reasserts itself and cuts this off, bringing back the cold from the east.

High uncertainty remains around T96

Redsunset

Matt Hugo
Without question the ECM Oper/ Det and Control run ate mild outliers against the overall ENS mean once again

ninebeanrows

I realise it may be painstaking at this stage, but very good set of ECM Ensembles at T168hrs with signs of another Easterly flirt possible :eek::o

ninebeanrows

ECM OP and DET 2m temps for somewhere (i think Reading)?.

Showing how big outliers they are.

blackius

Still positive dewpoint here +0.7c (arklow)
No easy access to models as am on phone.
That would mean sleet not snow flurries here.
Air temp is much the same as yesterday 3.9c.

You can access this online temporarily at :

http://www.arklow.741.com/summary.gif

ninebeanrows

blackius wrote: »

Still positive dewpoint here +0.7c (arklow)
No easy access to models as am on phone.
That would mean sleet not snow flurries here.
Air temp is much the same as yesterday 3.9c.

You can access this online temporarily at :

http://www.arklow.741.com/summary.gif

I don't think we are going to be in real snow air until Wednesday evening, if it gets here! Althought we will have colder dews than that from this evening, but the uppers will hit -7c this evening, then rise to -4c tomorrow before retreating to near -8c tomorrow night/Thursday

but we shall see, fingers crossed.

Tom Cruises Left Nut

Eyes down for the GFS

ninebeanrows

Latest GFS does not appear to be the last minute upgrade we were hoping for