Forecasts for Cold Snaps/Spells and Snowy Weather only.

Trogdor

Each run seems to upgrade each this cold snap which is making me happier and happier the only downside is that it can downgrade just as fast but the change in the charts has been amazing it's gone from zonal to easterly in 36 hours. If the wind were to pick even a slight easterly component it should be good for the east coast with a feed of showers:D
P.S.18z doesn't start to come out for another hour yet

lucernarian

As this run progresses, the Greenland High is weakened but it might hold off further into the Atlantic. This is just based on what looks likely and fits into the pattern - nothing really scientific in my method so this could be crap.

I'd also say that higher precipitation will be a feature of this run.

Edit: after looking at the t+120 chart, there's a definite increase in precipitation:p The Icelandic low in the run which is much stronger this time is the one forecast to hit us next weekend.

ninebeanrows

They say a week is along time in politics-



Somebody pinch me... is this January 2007 or have i been taken to some fantasy planet...

Stunning charts tonite just immense.. getting better all the time too..
How long will it last

boardsdotie

darkman2 wrote:

May aswell start with the ensemble chart on this thread:




Ive decided not to post charts from the models for the time being until we get over the more uncertain period and also so as not too build up too much expectation. Until then check out the ensemble chart ive just posted. As you can see really good agreement for a marked drop in temperature from the 20th. Where the average starts to rise is well into FI and should not be taken much notice of atm. Clear indication there of a very cold period of weather from this weekend. Indeed by the 22nd temperatures will be hardly getting above freezing on that chart. After that it could go anywhere from an Easterly to a Southwesterly. Fingers crossed for the former:D

I always wanted to understand this model. Is this true ....

Ignore all other lines except for the thick red line, as this is the average of all runs ?

lucernarian

Having seen the run up to t+168, I'm going to leave it at that. I'm pretty pleased, though the polar jet is doing some curious things on the chart 1 week ahead which I can't tell the significance of. I also notice heights are rising more strongly near/over Scandanavia. The +174 chart identifies an individual high pressure cell at this stage. This looks like a much better chart for long term prospects.

The HP positioning is not as good for those in the pale as the wind direction is much more of a northerly/northwesterly bearing as a consequence of the HP being a little further south. But the amount of small LPs at the beginning of events is terriffic for Ireland as a whole!!! There could be spells of light wintry precip. as early as Saturday evening!

*takes off dunce cap*

Those LP systems are lovely but the change between the two runs is startling. The first LP that hits us is developed totally different on this run. It can very easily change again. It's impossible to tell who will end up with the rain and who will get the snow and if the cold air will reach our shores before or after the rain has passed.

It's still very borderline...

Trogdor

boardsdotie wrote:

I always wanted to understand this model. Is this true ....

Ignore all other lines except for the thick red line, as this is the average of all runs ?

Sorry about going OT but the red line is the average temperature of the last 30 years. The white line is the average of all the runs and the blue is the control run that is displayed in full detail. The precipitation is on the bottom of the graph and 850hpa temp on the top.

EDIT: been keeping an eye on Wednesday's cold blip since last week and there is definately a bit of potential there too:D

boardsdotie

trogdor wrote:

Sorry about going OT but the red line is the average temperature of the last 30 years. The white line is the average of all the runs and the blue is the control run that is displayed in full detail. The precipitation is on the bottom of the graph and 850hpa temp on the top.

Thanks for that

Is there a plot on this graph where the precipitation meets the temp that predicts snow.

Trogdor

boardsdotie wrote:

Thanks for that

Is there a plot on this graph where the precipitation meets the temp that predicts snow.

OT again, sorry:o
Not really from this chart. There are so many different factors that have to be right to get snow that's it's very difficult to forecast. On this chart there is only temp and precip so it's not that great for predicting snow. To forecast snow the main variabes are the 850hpa temp which needs to be below -5C generally
http://85.214.49.20/wz/pics/Rtavn1802.png
the air thickness which needs to be below 528dam generally
http://85.214.49.20/wz/pics/Rtavn1803.png
and obviously the precip and
ground temp althought as i said there are many, many more aswell
http://85.214.49.20/wz/pics/Rtavn1804.png
http://85.214.49.20/wz/pics/Rtavn18017.png
they can all be found at
http://www.wetterzentrale.de/topkarten/fsavneur.html
and for just a snow prediction chart as i posted in a differnt post above you can go here http://www2.wetter3.de/animation.html
and click on niederschlagsstaerke und-form is the slide down box. Pink is snow and blue is rain

darkman2

boardsdotie wrote:

I always wanted to understand this model. Is this true ....

Ignore all other lines except for the thick red line, as this is the average of all runs ?

The white line is the average of the runs currently being displayed. The red line is what we should expect this time of year. (its the average over 30 years)

lucernarian

The 06z GFS looks good for 5 days of quite cold weather in a very unstable airstream. It starts off with NWely winds and finishes off with NEely winds so there should be something to please everyone in that run.

ECMWF is not very good at all to be honest. It portrays just what I feared: Atlantic HP forcing the LP away from us and then it moves right over us, or close enough to prevent extra convective showers or troughs from approaching us. What I saw on the ECMWF is something to be looked at before we get the snow shovels out.

http://www.wetterzentrale.de/topkarten/fsecmeur.html

Snowbie

Today and tomorrow are very crucial in the model saga.Already there has been a split in some models of which way the high is going to go.WC posted a nice chart above and one in which we want.A close enough GL high wiil do fine if there is a chance of the white stuff.Some of the models (GME) has it parked on top of us.

We will get some sort of reality today and more tomorrow for sure on what to expect.

arctictree

OK - looks like Met Eireann have acknowledged this up and coming cold spell:

"The rain will eventually clear away east later on Friday night or early on Saturday allowing winds to veer northwest or north, and bringing a change to noticeably colder weather. "

Getting closer......

A

Cornilius

So what are the chances for us here in the east in seeing any of the white stuff?Will that Northeasterly make any difference for showers coming in off the irish sea on Tuesday?

ninebeanrows

The 12z is very interesting for Eastern Ireland and much of Ireland tbh.:D

From this coming Sunday through to at least the following Wednesday if the 12z were to occur there would be a number of periods of snow across the east and elsehwere across the country!

First possibility is sometime Sunday - http://www.wetterzentrale.de/pics/Rtavn1261.png

The Monday as the winds veer easterly - notice that little LP
http://www.wetterzentrale.de/pics/Rtavn1441.png

Then Tuesday general showers off the Irish sea
http://www.wetterzentrale.de/pics/Rtavn1681.png
http://www.wetterzentrale.de/pics/Rtavn1682.png - Very cold
http://www.wetterzentrale.de/pics/Rtavn16817.png - very low maxima

All in all a good innings this evening

Will be interesting to see how my new gfs forecasts interprate things later
http://weathercheck.net/wetter/hw3_986php_flatfile/hw3.php?forecast=intwx&alt=inttest&interval=3&placeid=eidw

Snowbie

I would use caution in predicting snow this far WC as the charts are subject to change.
It is more than likely that it will become colder but we could also have the HP sitting over us too dampning down the showers.The charts you posted would produce snow but you know how fickle they are.
Id say it is too early to start a general ramp about snow lets be certain that we know the source of the cold air mass and the direction to which we have to look.:)

Besides the charts look a whole lot better each day

Supercell

12Z is VERY encouraging imho, getting closer now, gowd it this turns into another letdown I'll go mental!

darkman2

The UK met office has issued an early warning for all areas including NI.


I am still reluctant to comment on this past 120hrs because there is uncertainty in how this may occur. The GFS looks good obviously but we need agreement from the other models. The ECM was good this morning but was an outlier in its ensembles so lets wait and see later this evening.

JamesM

Weathercheck wrote:

Somebody pinch me... is this January 2007 or have i been taken to some fantasy planet...

Or back to January 1947

arctictree

Still looking good for snow Mon/Tue and then cold HP conditions for the rest of the week. Might not happen or could be very alpine'ish. We'll know for certain at the end of this week and will also have an idea if there any fronts involved.

A

Gonzo

lookin at the charts now and it seems to been weakening slightly for monday/tuesday with the high pressure much closer to Ireland now:(?

Villain

Yep the 12z looks to be removing the slight chances we had of snow, but these charts will change alot before Monday.

The low pressure for thursday looks nasty.

arctictree

Gonzo wrote:

lookin at the charts now and it seems to been weakening slightly for monday/tuesday with the high pressure much closer to Ireland now:(?

Yes, but Sunday is looking interesting now though. If that low moves anymore to the east we could be in for a shock....In fact, may happen Sunday night.....

A

Snowbie

18z GFS has given up on the HP moving towards GL alright and wants to pay us a very close visit with a presure prediction of 1040mb.The chances of snow will have been downgraded alot for this country according to this run and as artictree said it might be just Sunday as our day of hope with the early days of next week will be clear cold and frosty.

As i said before it is probably the 18z on wedensday evening before we can paint a picture.Still time for an upgrade again or a downgrade.

Gonzo

unfortunately for us 9 times out of 10 its almost always a downgrade:(

MetLuver

I hear ya Man!!! We never seem to get a break in this country.

rc28

morning everyone,
has anyone been looking at the radar this morning? there is a well organised band of precipitation moving over the west now, i hope some of it is half wintry. met eireann sem to have upgraded the amount of showers because on the radio it said "prolonged" showers of sleet, i'm so desperate to see cold weather i'll take sleet anyday!

ch750536

Had some sleet here this morning, but we are elevated.

Snowbie

Please use this thread for forecasts and models only.

Post [thread=2055023550]here[/thread] for wintry stuff.
Cheers.

MetLuver

Had some very heavy sleet here in Navan , bout 9.35 turned to snow for a few minuits, Wind is very strong in showers too! WELCOME WINTER 07!!!!

Met luver Snowbie already told you to post that in the thread made for those reports that he linked to in his last post.
This thread is for forecasts only!

As for next week-850's arent low enough imho and sea temps are too high so theres probably going to be too much modification of any cold sourced air feed.
Theres a big difference you know between cold 850's heading this way via a Scandi/Europe North sea area that has been historically warm than say if they were coming down to us via an already frozen Europe.
The only positive is its happening in january which is ideal but also all this is too far on the wrong side of reliable at the moment.
We know theres cold air coming but we dont know what track it will take and the exact positioning of all the factors that determine that track.

A slack cold flow is no use given the historically high sea temps,it will be modified too much such that showers wouldnt be as heavy and they would be more sleety in nature near the coast and on low ground.
Worse than that it will be sapping its cold into areas of Europe and Britain that will be drawing on its cooling powers before it gets here and then still it has to pass over a warmer than usual Irish sea and Atlantic (in the case of a northerly)

So I'm not enthused by whats coming at all (yet)

All eyes to the models in the next few days and see what they firm up on.

arctictree

Is that a LP over Munster on Monday on wetterzentrale?

Monday still looking very interesting.

A

darkman2

Snow looks very likely later Sunday and Monday depending on where you get precipitation. Dew points will be low enough and the 528 DAM thickness line is well south of Ireland. The 850s will be around -6, -7 and that well low enough for snow. Thats as far as I can go atm because there is far too much uncertainty after this. There is plenty of time for unpgrades or downgrades. The ECM is not too bad at all for example.

darkman2

darkman2 wrote:

The 850s will be around -6, -7 and that well low enough for snow.

Well we had rain last february with 850's of -8 on the East coast so thats not a certainty.
You are dealing here with a lot of uncertainty imho - air at height will be well cold but there will be a lot of surface warming on it making snow a touch and go subject.
Lets be realistic about this.

arctictree

Tristrame wrote:

Well we had rain last february with 850's of -8 on the East coast so thats not a certainty.
You are dealing here with a lot of uncertainty imho - air at height will be well cold but there will be a lot of surface warming on it making snow a touch and go subject.
Lets be realistic about this.

Yes but we have snow falling today on a predominantly westerly flow. Charts for next week are definitley colder.

Also, Jan 21st is statistically around the coldest time of the year. (1 month after the solstice). (is this correct??)

I would say, all in all if there is precipitation, chances are it will be of the wintry kind.

A

darkman2

Tristrame wrote:

Well we had rain last february with 850's of -8 on the East coast so thats not a certainty.
You are dealing here with a lot of uncertainty imho - air at height will be well cold but there will be a lot of surface warming on it making snow a touch and go subject.
Lets be realistic about this.

I am being realistic. I never said it would snow from the East coast. Im talking about the northerly and given we are not windward any precip that comes inland will fall as snow IMO. Look at today for example. Sunday and Monday imparticular will be colder. We have the trough coming south on Sunday night too. So opportunities there. BTW I have been very cautious with the upcoming spell. Nothing is certain yet. From the charts im expecting wintry showers of sleet and snow on Sunday and Monday. Mostly in the west and north.

http://cirrus.netweather.tv/fax/PPVN89.png

Snowbie

artictree wrote:

Yes but we have snow falling today on a predominantly westerly flow. Charts for next week are definitley colder.

Mainly over the higher ground in the west.I would imagine sleet on the lower ground and by the coast with the higher DPs.

Also, Jan 21st is statistically around the coldest time of the year. (1 month after the solstice). (is this correct??)

Thats the first i heard of that tbh.January of late has been one of the milder winter months.March 06 last year was colder than Jan 06.

darkman2

The 12z GFS is out and its excellent. Check out the ice days on Tuesday and Wednesday:D

The snow too;)

http://www2.wetter3.de/Animation_12_UTC/138_30.gif

Nice upgrade there. Still a long way to go but the 850s get down to -11 on this run:eek:

ninebeanrows

Very good 12z tonight prolongs the cold spell and it gets very cold.

Not much precip about though but we will see closer to the time.

As for the whether it will be cold enough debate.

The air from Monday of next week as progged on tonights 12z run would be cold enough for snow ie. 850's of -8c - -10c amd dewpoints below freezing.

During Sunday it may well be 50:50 however with higher ground recieving snow but the snowline will lower to sea-level as we move into Monday morning.

It is all about dewpoints for me... i have found there crucial in the last few years.. If the dewpoint is below freezing your half way there IMO and 850's of anything lower than -6c with a freezing or below dewpoint is good enough.
850hpa temps of -6c with a dewpoint of +1c / +2c is a different story however

Good post WC.
Yes it's all about the dp's too given the awkwardness of the recent lower athmosphere warm up.

Longfield is practically guaranteed snow in his location imho from the start.

I've noticed that it seems par for the course that model output is better for snow on one run,less better on the next and great on the next etc etc-so the happy pills come if the better runs are still showing within 96 hrs or so.

Having said that this is nice though unreliable being 8 days away-However it is still a possible indication of things to come.

http://85.214.49.20/wz/pics/Rtavn1802.png

darkman2

Check out some of the ensemble runs on meteociel:D

Supercell

Tristrame wrote:

Good post WC.

Longfield is practically guaranteed snow in his location imho from the start.

Jaysus don't hex it now Tristrame

Agree with WC post, well thought out and pretty much sums it up exactly.
Its still a long way to Sunday onwards in meteorological terms, not going to get carried away till Friday

Snowbie

The best run of the winter without doubt the 12z.I would take it now:p.
The 18z has been decent the last few days with little variation.Lets see later on what we can expect as this will be a very good time frame were in.18z out about 9 pm.

Weathercheck wrote:

It is all about dewpoints for me... i have found there crucial in the last few years.. If the dewpoint is below freezing your half way there IMO and 850's of anything lower than -6c with a freezing or below dewpoint is good enough.
850hpa temps of -6c with a dewpoint of +1c / +2c is a different story however

Spot on WC.

Just to keep in mind that we on the coast or close to the coast will have to contend with an Irish sea SST being higher at this time of the year than normal for obvious reasons and which will effect the coastal DP and temperature.The longer the northerly persists the better but if we get a NE wind or east direction too early then forget about snow at low levels.A persistent northerly and gradual NE over a couple of days will be perfect and which seems to suggest so in the models now.:)

Im new to this: check this out: http://www.metoffice.gov.uk/weather/uk/surface_pressure.html

skip the chart to T+84 (hours)
where do you all predict the high over the atlantic will move? (also where would you HOPE it to go to help our chances of snow?

here is a short range forecast site specifically for mountain regions
http://ukie.accuweather.com/ukie/mountain-forecast.asp?

Villain

12z looks good, still far off though and I'm sure it will change again tomorrow, although I was expecting a downgrade tbh.

Hmmm

Met Éireann are expecting the HP to the Northwest to move down over the country.
Goodbye snow and hello frost if thats the case-ie boring

Scubadevils

6.01 weather wouldn't inspire much hope for snow early next week - high pressure moving in from the west?

darkman2

Tristrame wrote:

Hmmm

Met Éireann are expecting the HP to the Northwest to move down over the country.
Goodbye snow and hello frost if thats the case-ie boring

Hardly supprising really since they use the ECM charts. Alot of varying outcomes as soon as Sunday. Its gonna be Friday I think before we can be sure of anything.

Snowbie

It can go either way imo.More than likely it was always going to move in from the west,it whenever it is going to move in from the west.I didnt see the rte weather at 7 but at the 1 o clock news they said it was going to settle down for next week.

darkman2

darkman2 wrote:

Hardly supprising really since they use the ECM charts. Alot of varying outcomes as soon as Sunday. Its gonna be Friday I think before we can be sure of anything.

Yes but the problem is as you know ,GFS is more accurate in dealing with mobile zonality.
It's usually kack when it comes to blocking scenario's.

You'd be raving at how good ECM was if it was predicting blizzards wouldnt you? and understandably so.