Forecasts for Cold Snaps/Spells and Snowy Weather only.

LookingFor

LookingFor wrote:

but doesn't mention the east..

Uhm thats because it only goes to sunday..
After sunday and all next week the winds are North East which essentially means a dry WEST,NORTWEST and SOUTH but a very showery EAST.

The winds are N or NW for 2 days Max but are mainly progged NNE or NE after that.

By the way they'd be mentioning the East if this came off
-10 850's blown down from aberdeenshire!

http://www.wetterzentrale.de/pics/Rtavn902.html

Snowbie

Tristrame wrote:

An artic source like this one certainly should deliver that even with the modification of higher sst'sin the Irish sea.

I would agree with that to a certain extent but with the nature of cold mass running over a warmer sea will deliver heavy showers at that (depending on how high the atmospheric pressure is too)and towering cumulus.Also showers would start off of rain/sleet and temperature will plummet a degree or so in a heavy shower with the downdraught turning what rain/sleet into snow.No lying snow on coastal fringes but on higher elevations.

Take into account that even if we get onshore winds here coming from a modified SSTs, the coastal temperature/DPs will be that much higher and have to rely on heavy showers to peg back temps.I really cant see lying snow where i am at 30m asl and 1.5mile from the coast.Ben of Howth could get a dusting as it is 1c colder up there even though Howth juts out to sea.

This above theory is almost always put into practice.Interesting times ahead.

EDIT:It be perfect if the DPs fell to a minus level alright,as we know air temps will be low enough,DPs is nearly the key in this instance.

At the moment snowbie NOTHING is certain which is what I'm getting at.
That air source should have negative dp's despite it's sea track-look at the origin.
That air source should cause heavy showers in the Irish sea which should be mostly sleet and snow rather than rain.

IF showers were to develop along the lines of the October '03 showers then you would have lying snow at times along even coastal margins,this is after all mid january and not mid february.-10 850 air on monday and tuesday with pressure sub 1020 would deliver snow.

As I said None of this is certain as every model on every run is coming up with something slightly different.
The best I can say I suppose is that I wouldnt rule out something...

I might add that this 12z declines in snowness as the week progresses so thats not good.

ninebeanrows

For some reason i like the 12z GFS even though many will say otherwise!

Why you ask!

Well over this winter i truly expected not to see any snow in my location nor any change of cold easterly winds affecting Ireland.

But the 12z suggests otherwise.. cold air slowly drags south during Sunday with widespread wintry showers. As we move towards Monday winds are set to veer ENE.. with showers building in the Irish sea, by now 850hpa temps will be nearing -10c and dewpoint going below freezing. Bt Midday Monday temperatures will be falling to 3/4c and the showers will begin to push onto the east coast beginning to fall as snow, towards Monday evening the shower activity will increase and temperatures will fall well below freezing.. Overnight and into Tuesday lots of snow showers are predicted to affect the east coast and seen as DP's will be below freezing and temperatures below freezing it should all stick!

Thats why i like the 12z.. all that is predicted in the T+84hr timeframe! After that it's ifs and buts! While the cold is expected to continue until Thursday with rain/snow in many areas!!

Snowbie

Tristrame wrote:

At the moment snowbie NOTHING is certain which is what I'm getting at.
That air source should have negative dp's despite it's sea track-look at the origin.
That air source should cause heavy showers in the Irish sea which should be mostly sleet and snow rather than rain.

IF showers were to develop along the lines of the October '03 showers then you would have lying snow at times along even coastal margins,this is after all mid january and not mid february.-10 850 air on monday and tuesday with pressure sub 1020 would deliver snow.

As I said None of this is certain as every model on every run is coming up with something slightly different.
The best I can say I suppose is that I wouldnt rule out something...

True no certaintity yet even this close except it be colder.18z will be interesting.

darkman2

hmmmm I get the impression there is a little misplaced optimisim here. Yes Wintry showers possible for Sunday and possibly Monday. However on Monday I would like to point out the SSTs in the Irish sea 6 - 7C - ouch. Also the wind may be ENE on Monday but on Tuesday its very much NNE which im pretty sure will see showers drift harmlessly down the Irish sea (those that actually develope with the pressure that high). Also one very big factor that has been overlooked I feel is the DAM thickness. The 528 line is gone by Wednesday night - not good.


The only thing I could think of that would back up Tristames and WC's case would be high lapse rates on the Irish sea due to the high ssts. (this will increase shower activity regardless of pressure) - Now I could be wrong (hope I am) but im not confident atm.

What I would look out for is possible retrogression of the high back toward GL late next week (remember you heard it here first):D

http://moe.met.fsu.edu/tcgengifs//ukm/2007011912//slp20.png

UKMO chart at 120hrs

Supercell

Any fetch with an easterly component will be good for eastern county areas probably.

Personally am hoping we get a straight NE as this historically seems to be the best, at least in the Dublin area.
I'm trying to keep a sane head, there's a fantastic chance that artictree and myself could see something significant, all depends on the positioning of the Atlantic high.

Just hope it starts here before Monday - do NOT want to be stuck in work while its blizzards here!!

Snowbie

Heh! Showers-they could miss us altogether and hit eh! Gonzo:D

Snowbie

Longfield wrote:

Personally am hoping we get a straight NE as this historically seems to be the best, at least in the Dublin area

Feb 7th 1991,nice blizzard in from the NE that day.Remember watchin Dr.Aidan McNulty on live at 3:o and he was talking about heavy snow moving in from the Irish sea to hit the Dublin area within an hour.His timing couldnt have been perfect.

Anyway you be certain to get lying snow up there any room to pitch a tent on your land.:p

lucernarian

I'm at a loss as to what will happen towards the end of next week. As someone, Tristrame I think, said sometime ago, this anticyclone is intense and will go wherever it pleases. The UKMO t+144 chart is sensational, another GH building up during next week.

This chart here: http://85.214.49.20/wz/pics/brack3.gif shows 2 interesting looking troughs on the chart. What exactly are those "branched" troughs, according to the UKMO? Descriptions such as "enhanced" and "intensive" would be very welcome:p

Anything beyond Tuesday is fairly meaningless in terms of reliability anyway, so we will have to contend ourselves with this upcoming cold snap. I think the window of opportunity for snow is too narrow for lying snow in Dublin for example. What was a good chance of widespread snow from Sunday onwards, has dwindled away, with warm sectors being just a little too warm. The Wednesday morning period looks likely to suffer the same fate of cold rain, this time preceded by sleet.

Monday and Tuesday should have a few showers of a snowy nature allright:D These 2 days are a bit of a lottery as to who will get the heavy snow showers. There will have to be extensive and organised precipitation for a covering of snow though. It's fingers crossed from here on in for helpful dewpoints. The cold air will not be particularly well established by the time the northeasterly starts so it could be a problem.

Parts of a region from Clare to Belfast, within 30 miles of the coast, stand a good chance of a light snow covering come Sunday night. That though, is not the easiest thing to predict and there could be smiles and sadness all round when Monday arrives.

Supercell

To_be_confirmed wrote:

This chart here: http://85.214.49.20/wz/pics/brack3.gif shows 2 interesting looking troughs on the chart. What exactly are those "branched" troughs, according to the UKMO? Descriptions such as "enhanced" and "intensive" would be very welcome:p

Put simply bloody heavy, possibly thundery showers

SpitfireIV

To_be_confirmed wrote:

This chart here: http://85.214.49.20/wz/pics/brack3.gif shows 2 interesting looking troughs on the chart. What exactly are those "branched" troughs, according to the UKMO? Descriptions such as "enhanced" and "intensive" would be very welcome:p

According to a couple of fellow's over on TWO, them symbols are:

"They mark where the forecasters believe there will be lines or zones of convergence. Convergence zones often enhance convective dynamics - it was such a zone that was responsible for the great deluge N Cornwall that lead to the Boscastle floods."

and

"They're a convergence zone, where winds from two slightly differing directions meet and they can give heavy and persistent precipitation. It was a convergence zone which gave Sheppey over a foot of snow in one sitting in 1987"

So maybe "intensive" would have been a correct guess


Anyway, how does Carlow fit into all this, I guess I'll see nothing, maybe some more rain, but you never know :rolleyes:

Supercell

Ahh found the official explanation on http://www.metoffice.gov.uk/weather/uk/guide/key.html

Convergence Line
A slow-moving trough, which is parallel to the isobars and tends to be persistent over many hours or days. They are quite common in cold northerly outbreaks down the Irish Sea, affecting west Wales, Devon and Cornwall in particular, but can be found in other areas also. This convergence line can gives hours of persistent precipitation over very localised areas, whilst a few miles down the road it is relatively dry, leading to some heavy snowfall/rainfall. In summer the convergence lines are not as easy to forecast, but then can still occur due to sea-breeze convergence, and are over the land, whilst in winter they are over the sea.

lucernarian

Sadly the Fax chart for midday on Monday has been updated with this: an easterly with no marked troughs or fronts. http://85.214.49.20/wz/pics/brack2a.gif

Supercell

To_be_confirmed wrote:

Sadly the Fax chart for midday on Monday has been updated with this: an easterly with no marked troughs or fronts. http://85.214.49.20/wz/pics/brack2a.gif

Are you nuts??, there's nothing sad about that chart at all!!
That's general sleet/snow for all eastern areas, no need for small convergence zones,its heavy showers/continuous precip for all!!(heavier in the south admittedly)

Fecking brill!

Supercell

Tbh, any precip fprecasts upto T+12 hours are probably not going to be very accurate, all depends on the eventual position of the atlantic high, is throwing up some great charts though on the way!

Well you're guaranteed something anyhow Longfield.
Not sure how showery the Irish sea will be but my hunch is very showery.

Those lines of convergence are also shallow low pressure areas by the way which were common in 80's winters and you know what happened then

You do need sub zero dp's though-without that ,Longfield and artic tree will still be sucking diesel but the coastal margins may only have rain or sleet.

I'm not going to call whether the dp's will be minus enough in time for the precip though.
The arrival of precip tends to rise dp's rather quickly so they would want to be lower than -3c realistically.
This is all possible but its a bit of an ask to be honest...

nacho libre

darkman2 wrote:

hmmmm I get the impression there is a little misplaced optimisim here. Yes Wintry showers possible for Sunday and possibly Monday. However on Monday I would like to point out the SSTs in the Irish sea 6 - 7C - ouch. Also the wind may be ENE on Monday but on Tuesday its very much NNE which im pretty sure will see showers drift harmlessly down the Irish sea (those that actually develope with the pressure that high). Also one very big factor that has been overlooked I feel is the DAM thickness. The 528 line is gone by Wednesday night - not good.


The only thing I could think of that would back up Tristames and WC's case would be high lapse rates on the Irish sea due to the high ssts. (this will increase shower activity regardless of pressure) - Now I could be wrong (hope I am) but im not confident atm.

What I would look out for is possible retrogression of the high back toward GL late next week (remember you heard it here first):D

http://moe.met.fsu.edu/tcgengifs//ukm/2007011912//slp20.png

UKMO chart at 120hrs

What do you mean by GL? According to the forecast the high will move westwards allowing troughs to come down from the North! which, if true, will mean some moderate accmulations for us here in the West on Sunday and Monday night!

ninebeanrows

Some good charts tonight although chances of a prolonged cold snap are now slipping away... the ECM is still sticking to its guns but slowly losing.. UKM has swung on the side of the GFS..

Basically

Sunday - Cold, Showery with wintry showersn turning to snow towards nightfall - areas affected northern,western areas.

Monday - Winds turning ENE, getting colder still, temperatures from around 1-4c with showery activity moving into the east coast - snow showers peppering the east coast from mid afternoon till late.

Tuesday - snow showers will continue in eastern areas but will slowly die out.. a general area of precip will move down from the north giving rain/sleet/snow to most areas...

Wednesday - cold returning for a short time before the high collapses - Mostly dry but with a harsh frost towards dusk.

That's a fair assessment of the UKM/GFS outlook

darkman2

nacho libre wrote:

What do you mean by GL? According to the forecast the high will move westwards allowing troughs to come down from the North! which, if true, will mean some moderate accmulations for us here in the West on Sunday and Monday night!

GL - short for Greenland.;)

I do think the west and north have a reasonable chance of a covering Sunday night.

Mainly on higher ground though.

Snowbie

9.30 RTE weather quote from Gerald Fleming"significant falls of snow moving down from the NE on sunday night"
Well thats a huge upgrade to the 6.1 weather when snow was not mentioned.
I wonder has this put speculation to rest.Seems certain now for sunday with Northerly winds.No onshore wind for the East so looks good.:)

Supercell

Significant in the north an at elevation on Sunday night maybe.

Thats a brave forecast tbh, wouldn't like to guess at what going to happen on Sunday until late Saturday tbh, this isn't normal zonal muck being predicted here, a half a degree either way will be the difference between cold rain and a blizzard.

Snowbie

As i said it looks good.See if he says the exact same later on.Temps could be low enough and espeicially during night time hours.It is unlike Met Eireann to forecast snow using the term "significant falls of snow" or is it i just havin heard this term in a long while.

Id even wait to Sunday itself to see a more accurate forecast.In a reliable time frame i thinks now.

darkman2

Snow event Tuesday night/wednesday for the East:

http://www2.wetter3.de/Animation_18_UTC/114_30.gif

ninebeanrows

Want snow? Let the 18z lead you to snowland!!:D

As for Sunday - not too sure on that really did he place his emphasis toward Monday?

Well the 18z is amazing.. Monday snow showers peppering the Irish sea coasts and turning heavy..

Tuesday heavy snow showers right down the Irish east coast..

Wednesday - small lp with warm sector tries to push east.. buffeted back = lots of precipitation and lots of snow across the east - low pressure pushed back cold from east pushes back - flurries push onto east coast for Wednesday nite..



Yehaaaaaaaaaaaaaa - Caution of course advised!!

Supercell

darkman2 wrote:

Snow event Tuesday night/wednesday for the East:

http://www2.wetter3.de/Animation_18_UTC/114_30.gif

Darkman those charts are a pile of shiite tbh for areas where snow is borderline.
If we were forecasting temps of -5°C and precip then they might have merit. Tbh any precip forecasts are almost worthless this far out as to be snow or otherwise, total and utter waste of time.

Those fecking pink charts are an utter waste of time to Irish users and I wish you didnt post them tbh.

Snowbie

Seen that looks like a PL formation in Irish sea at 108hrs on the 18z.Good run.

darkman2

Longfield wrote:

Darkman those charts are a pile of shiite tbh for areas where snow is borderline.
If we were forecasting temps of -5°C and precip then they might have merit. Tbh any precip forecasts are almost worthless this far out as to be snow or otherwise, total and utter waste of time.

Those fecking pink charts are an utter waste of time to Irish users and I wish you didnt post them tbh.

Is this post a joke?

Those charts are the most accurate we have access to and I can tell you from my experience they are supprisingly accurate and are part of the GFS model. Maybe you should give them a phone call and let them know your suggestions?