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Vizual Pics

MT what did you mean earlier about a wave in the system? Is this when the front breaks down and begins to mix with the colder air?

Vizual Pics

pmccormack wrote: »

Quick Question, Whats the difference between freezing rain/drizzle and Sleet/hail?

This is what freezing rain is...and you know what the others are?

http://en.wikipedia.org/wiki/Freezing_rain

thetonynator

forkassed wrote: »

Such a slow moving front can only aid the chances of snow fall with cold air undercutting...?

I'm in the suburbs of Dublin right by the coast and am hoping for a whiteout instead of the usual sleet fest to end this epic weather event.

it won't be the end, there are more cold temps forecast for next week, not as cold but enough for the thaw to be very slow . .

forkassed

thetonynator wrote: »

it won't be the end, there are more cold temps forecast for next week, not as cold but enough for the thaw to be very slow . .

I realize that and its fairly evident on the ensembles.

I just have reservations about whether snow will occur tomorrow morning at lower levels by the coast in the east.

On the positive side i have never witnessed such a scenario where the front is coming in from the northwest so eastern areas are favoured .

Usually the cold spells are ended fairly abrubtly by a front coming in alot quicker from the southwest and Northern areas are favoured for snowfall.

M.T. Cranium

A wave in this case would be a low pressure centre forming in the trough and forcing any milder air to remain south of its track, rather than mixing further north ahead of a front.

Warm frontal waves are often tricky to forecast as models don't always catch them and once they form, they tend to slide easily around any entrenched cold air. Discussions of decades-old cold spells are full of references to mild air that never arrived (in the U.K. for the most part) and cold air that hung around -- so despite the advance in the models in recent years, we'll have to see how this plays out, the amount of warming shown on the most recent model run was not very impressive -- without the warm ocean around Ireland, there would be no chance of this even changing from snow to rain at all.

TheMilkyPirate

Snow reported in ballina, mayo from this front just now.

M.T. Cranium

Friday, 3 December, 2010
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TODAY ... Snow is likely to develop across most of eastern, central and northern counties this morning, while rain moves into the west and later south coast, and some sleet or freezing rain occupies a band between these zones, inland west and inland south. Various places may have changes of precip type, but in general, the snow will be heavier over existing snow cover in the east and inland north, and may reach 8-12 cms in places. Very slippery conditions will develop especially in the south and inland west due to sleet and freezing rain. Wind (WSW 20-30 mph) may become a factor in some places but the stronger winds may not mix down to the ground in all locations, and some dense fog may develop during this mixed precip event. Highs will be about -1 to +2 C for most, and a bit higher in coastal areas (to +5 C). Specifically for Dublin, expect some snow, mixing at times with sleet, and amounts dependent on elevation (3-7 cms). Conditions may become quite sloppy at low elevations and in the city centre. Some of the heavier snow is likely to be in a zone from Laois north to Westmeath and into Ulster.

TONIGHT will see most of this precip ending, with some light snow or sleet persisting, with fog patches becoming quite dense in some areas, cold with lows dropping back to -4 or -6 C inland, -2 C coastal areas. Winds near the west coast will become NNW 20-30 mph, and somewhat weaker northerly elsewhere.

SATURDAY will bring variable cloud, some patchy light snow or sleet, but also some sunny breaks, and moderate northerly winds, with highs of about 3 C.

SUNDAY will be a generally dry day with some sunshine, a cold start with ice fog developing in many areas, lows to about -6 C, then highs of about 2-4 C.

MONDAY will bring wintry showers in a northwest to north wind, and a temperature range from about -5 C to +3 C.

TUESDAY and WEDNESDAY are looking breezy, showery (sleet or snow mostly) and cool, although temperatures might recover a bit towards the west where highs of 5-7 C are possible. Further east it may stay closer to 2 or 3 C.

All through this period, some snow melt may occur, but I don't foresee all of the current snow pack melting in heavier snow areas, and there will be a certain amount of freeze-thaw activity leading to more ice at times.

The further outlook is for much colder weather to return ... I suspect that the models may begin to shift the Atlantic high west and allow in a renewed northerly perhaps faster than indicated, but in any case, the models have nothing but cool high pressure and then cold northerly weather patterns on offer. The main question is timing and balance between them. Just keep the time period 19-22 Dec in the back of your mind for some kind of winter storm potential.

Meanwhile, Thursday here was rather bland, cloudy with some hazy sun earlier, light rain more recently, and a high of about 7 C. It has turned a lot colder across most of central and eastern North America.

Watch for updates, and monitor the threads on the forum for information about the spreading snow, sleet, freezing rain and rain.

Just to anticipate a few questions -- snow should arrive in Dublin and Wicklow around 0900h ... Cork is likely to start out with snow or sleet, turn to either freezing rain or a cold rain that will be just as bad on top of the frozen ground, then back to sleet ... Waterford looks more like a transition from snow to sleet to a brief period of freezing rain then back to snow ... similar for Wexford ... Limerick would be likely to see a bit of everything but may not get quite as much as the precip develops more further east ... Galway likely to see mixing by elevation and distance inland from the bay.

Stay safe if you have to travel.

Musicman2000

Just keep the time period 19-22 Dec in the back of your mind for some kind of winter storm potential.

Would this be a winter blizzard or more mild atlantic rain?

M.T. Cranium

Comments I make about distant potential events are based on research into trends and tendencies -- so all I can really say at this point is that a colder than average trend is likely through the month (although not as cold as recently for a while now) and a significant storm event is likely around that time (20-21 Dec) ... it is more likely to be a wintry storm than a mild storm but if it were to prove to be a mild event it would probably become very windy and pull down cold air rapidly as it departed ... but the current model runs are suggesting a colder period just before then and some sort of reload of the severe cold, so possibly a northeast wind streamer event would be favoured, perhaps enhanced by low pressure moving by to the south. Anyway it's a long way off and we have some active weather to consider in the next 24 hours, so here's an update on that.

UPDATE _ Friday, 6:00 p.m.
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More wintry showers are likely overnight and through Saturday in a westerly flow turning more northwest to northerly on Saturday. Temperatures will fall back a few degrees and these wintry showers will take a variety of forms, with rain more likely in western counties, near the south coast and in city centre Dublin, while sleet or snow will be more likely in most other regions.

Except near the west coast where lows will remain 0-2 C, the overnight lows will fall to about -3 or a bit lower where it clears for a while and some very icy conditions are likely as slush freezes. A few places could see 1-3 cms of new snow but falls will not be widespread or very organized. During the day tomorrow the balance between rain and wintry types of precip will swing more to rain but there will continue to be a mix -- amounts of precip in any case will be fairly light, in the range of 2-5 mms which would give a few places (likely higher and well inland) 2-5 cms of snow.

The pattern beyond tomorrow remains about as predicted earlier and will be generally a bit milder than last week but not as mild as average -- this means a freeze-thaw cycle for areas that still have snow, some limited melting, and frequent returns to icy conditions especially outside the warmest part of the day (which is 1100-1500h).

thetonynator

M.T. Cranium wrote: »

Comments I make about distant potential events are based on research into trends and tendencies -- so all I can really say at this point is that a colder than average trend is likely through the month (although not as cold as recently for a while now) and a significant storm event is likely around that time (20-21 Dec) ... it is more likely to be a wintry storm than a mild storm but if it were to prove to be a mild event it would probably become very windy and pull down cold air rapidly as it departed ... but the current model runs are suggesting a colder period just before then and some sort of reload of the severe cold, so possibly a northeast wind streamer event would be favoured, perhaps enhanced by low pressure moving by to the south. Anyway it's a long way off and we have some active weather to consider in the next 24 hours, so here's an update on that.

I'm dreaming of a . . .

https://www.youtube.com/watch?v=PA45TnJQxhU

M.T. Cranium

Saturday, 4 December, 2010
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TODAY ... Cloudy with some afternoon sunny breaks, continuing rather sloppy with temperatures just above freezing inland, to 4-6 C around coastal regions, possibly 6-8 C in the southwest. Widespread rather light showers of rain turning to sleet or wet snow over higher inland areas. Accumulations slight, 2-4 mms of liquid and in a few places 1-3 cms of snow (higher up, a bit more could fall). Moderate westerly winds turning more to northwest then north 15-20 mph.

Very slippery conditions will continue, with a slow thaw of lying snow at lower elevations, not much if any melt above 300m asl.

TONIGHT ... Clearing in some northern sections, mostly cloudy further south with a few remnant sprinkles of sleet. Some freezing fog developing as lows reach -5 C on average over snow, -1 C over bare ground. Light winds.

Icy roads and pavements may become quite treacherous in some parts of eastern and northern counties.

SUNDAY ... Variable cloud, some sunny intervals for most, only a few widely scattered light wintry showers, rather chilly again with highs of about 2-5 C.

MONDAY ... Cloudy with some breaks, more frequent wintry showers, hail, sleet and some snow prevalent, rain near coasts. Lows near -4 C and highs near 5 C on average (a bit cooler over remnant snow as a slow thaw continues).

TUESDAY ... Slightly colder again with flurries in Ulster, mixed wintry showers elsewhere, in a northerly flow of 15-25 mph. Lows near -5 C and highs near 2 C northeast to 7 C southwest.

WEDNESDAY ... Breezy and milder especially in the southwest. Scattered showers in gusty W to NW winds. Variable cloud and mixed showers elsewhere, warming rather restricted in northeast, so highs in a range from about 4 C northeast to 10 C southwest.

THURSDAY-FRIDAY ... Yet another brief cooling interval Thursday on strong northwest to north winds, flurries, but quickly turning milder again during Friday. This topsy-turvy weather pattern will have the freeze-thaw cycle on full throttle and some road damage is likely as deep frost comes out of the ground gradually. Snow melt will continue rather slowly and will not be complete especially in wooded areas and on higher ground.

FURTHER OUTLOOK ... Around the weekend of the 11th-12th it should once again start to turn colder but this time perhaps in a much more organized northerly outbreak that may return temperatures to near freezing. Remember, we're keeping a close watch on the period 19th-22nd for a winter storm.

I hardly noticed, but today was partly cloudy and mild here with a high near 7 C. It continues rather cold further east and there was a heavy lake effect snowstorm near Buffalo NY, but otherwise not too much happening, just a dry cold pattern although not too extreme.

I plan extensive rest this weekend (having been through the weather wars all week) so you may have to hunt for scraps from the weather forum although I imagine the resting impulse will be quite widespread there too. :cool:

Have a good weekend and watch for ice. I imagine there will be more of these snow slides from flat roofs as well.

yachtsman

Thanks

Thanks MT, love reading your forecasts.

irish147

19th-22nd for a winter storm.
would be nice

Caitriona

I know it's a very basic question, but what exactly is involved in a wintry storm? Would there be more snow? (Sorry, I'm only a beginner here)

M.T. Cranium

Just my way of saying the period could produce a storm with wintry weather conditions, so yes snow likely to be involved, but we'll have to wait about two weeks for the details to become clearer. My research shows that in Dec and Jan the full moon is often a time for a strong low pressure system and as the pattern looks cold (after perhaps a slightly milder period mid-month) putting it together I speculate on a wintry storm for the days in that period, 19th to 22nd. The full moon is precisely at 0813h GMT on the 21st, if visible in Ireland you would see it setting around 0730-0800h on 21 Dec as it enters a growing eclipsed state; where I live, if it's clear we'll see a lunar eclipse around midnight (20-21 Dec local time).

Sponge Bob

While temperatures were above zero with rather nice sunshine in the west today a very sharp frost has already set in as I type. As the air was still the ice from friday night melted but did not dry out owing to the lack of a drying breeze.

The grit was washed off the roads in most areas by yesterdays rain and has not been replenished. At 4pm the sun went down and the roads and footpaths were pretty uniformly wet everywhere at that time.

By around 8-9pm this evening there will be a serious ice covering absolutely everywhere it rained yesterday. Be very very careful out there tonight and tomorrow morning unless you are on a road you know to have been gritted since the rains on friday.

HornyDevil

M.T. Cranium wrote: »

where I live, if it's clear we'll see a lunar eclipse around midnight (20-21 Dec local time).

where you live is Vancouver . . . . Canada

hmmm

Tae laidir

The National Weather Service in the US are indicating a strong La Nina event around now and lasting throughout the winter.
Do you think this is significant for us?

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.html

M.T. Cranium

The La Nina effect factors into most long-range forecasts that have already been made, but to be honest the range of past conditions in Europe in La Nina winters covers almost the entire range of possibilities, so for somebody to say "this will be one of those La Nina winters" means very little away from the source region. Even here on the west coast of North America, I think we can only rule out the mildest third of outcomes, and deal with the other two thirds, so either very cold or near normal, and with snowfall, about the same thing, it's unlikely to be one of those snow-free winters we sometimes get here, but as to very snowy or just average, all that's in play (from the starting point of saying it's a La Nina winter).

I tend to use a lot of other factors in my long-range forecasting and figure that these will be built into the La Nina signal anyway. All La Nina means is that water temperatures in the equatorial Pacific will be cooler than average. This tends to be balanced by a warm bubble of sea surface temperatures in the mid-latitudes near the middle of the vast Pacific (near the IDL). That's the more relevant factor because it tends to favour ridge development into Alaska, something that then favours cold air coming south into central North America. But you can see that if that's just a broad general picture, the variations in it are significant. How strong will that ridge be? How many times will it break down? A month's climate often depends on a few singularities and not on the background pattern. Consider November 2009 in Ireland, a month that will be remembered mostly for two days of very heavy rainfall.

And this month is already heavily influenced by three days of extreme cold and locally heavy snow, even if the rest of the month proved bland and near normal, that's what people would remember and also those stats would have a heavy influence on the final figures for the month.

inabina

MT your knowledge is just amazing. Even my mother is now asking me "can you please read out the latest from that man in Canada". I just want to say thankyou, we really appreciate your contributions!

Tae laidir

Thanks MT.
But what has happened to our 'normal' Gulf Stream depressions that pass between Ireland & Iceland? We haven't seen the in months!
The Carribean seems to be as warm as usual & you' ve ruled out La Nina!
Any depressions seem to be limp, and are easily pushed up towards Baffin Island & Western Greenland, or more likely, wander over towards Iberia & the mediterranean Sea.
Anything to do with Solar minimum?
http://solarscience.msfc.nasa.gov/images/ssn_predict_l.gif

M.T. Cranium

I can't go into all my reasoning but that is certainly one of the factors keeping the jet stream and storm track further south this winter. Another important factor, I believe, is that retrograde motion has set in which is keeping pressures high around Iceland and Greenland in general. Some weak lows are breaking through up there but they are not strong enough to dislodge the cold air in a vast trough over Europe. I don't think we're quite locked into this pattern, one or two breakdowns may occur and then it would turn a lot milder for a few days, possibly.

This may be the wrong time to mention it, but I don't claim 100% accuracy in these long-range questions, actually probably overdue for a reversal of form -- this is not easy stuff and people who claim really high accuracy rates are usually hoping people have short memories or just started reading. I would say we are making some progress (as a group) and with so many people busy at it, there will always be somebody close to having the right forecast which keeps interest up, I suppose. :cool:

M.T. Cranium

Sunday, 5 December, 2010
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New moon occurs today at 1736h GMT.

TODAY ... Rather cold and generally dry with some sunshine at times, except for some brief and light wintry showers, these more frequent in Ulster, Connacht and nearby parts of Munster and Leinster. Winds northerly at about 10-20 mph. Highs 4-7 C in most areas, but 2-4 C over snow cover.

TONIGHT ... Cloudy with some clear intervals, frosty especially inland, lows reaching -5 C around midnight but then possibly becoming a little milder ... scattered wintry showers developing ... some freezing fog.

MONDAY ... Variable cloud, passing wintry showers, mostly rain western counties, mostly snow Ulster, hail and sleet elsewhere ... winds NW to N at about 10-20 mph ... highs 3-5 C (5-8 C west and south).

TUESDAY ... Variable cloud, longer sunny intervals south and west, rather cold, lows near -5 C and highs near +4 C on average. Freezing fog in morning over the snow cover that remains.

WEDNESDAY ... A bit milder in the south and west with a few showers in rather gusty W to NW winds 20-30 mph ... staying cold east and north with mixed sleety or wintry showers. Highs near 6 C.

OUTLOOK ... Slightly colder again on Thursday as a renewed northerly flow develops, risk of some light snow in the east, but turning milder on Friday, possibly quite mild for a day or two, before a colder trend begins near the end of the weekend.

Possibly the most significant weather impact in the next week is going to be cumulative -- with all the freezing and thawing, there may be some road damage and it will certainly remain icy in some eastern and central counties.

M.T. Cranium

UPDATE _ Sunday, 10 p.m.
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A frontal trough moving in from the northwest will arrive over Donegal about 0300h and move through Ulster before sunrise, then will continue south all day tomorrow ... expect some outbreaks of snow with this mainly to the east of a line from Mayo to Lough Derg to Waterford, but at higher elevations to the west of that also. At lower elevations in the southwest showers are likely to be hail, sleet and some rain but mixing at times with snow ... in the north and east where the snow is heavier, some amounts of 3-7 cms are possible. This will hold temperatures down to about -1 to +2 C in that zone and perhaps 3-5 C in the southwest. Tuesday will stay quite cold with some further snow possible especially near the Irish Sea, and Wednesday is looking quite chilly with further snow likely for Ulster and Leinster now as the track of a slightly milder infusion from the west appears to be only as far inland as Monday's somewhat indistinct rain-snow divide that I mentioned above.

In other words, the models are responding to the usual principle that cold air is hard to shift without massive upper support and that just isn't really part of the equation ... although I still think it will turn a bit milder end of the week and next weekend, this may be also a rather brief and subtle warming that perhaps touches normal values for a day before falling back in the next cold wave to follow.

Will update at 0530 or so. Check with the active discussion thread for more detailed analysis as I am heading out for a few hours now.

Pangea

M.T. Cranium wrote: »

UPDATE _ Sunday, 10 p.m.
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expect some outbreaks of snow with this mainly to the east of a line from Mayo to Lough Derg to Waterford,

For a moment there I thought it was Lough derg in Donegal, but seeing as u mentioned it between mayo and waterford Im guessing its the one in the south of the country you are talking about.
Pheww

M.T. Cranium

Monday, 6 December, 2010
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TODAY ... Foggy and very cold in many parts of Ireland for a considerable part of the morning into mid-day over snow cover ... snow moving gradually south, covering much of Ulster this morning, north Connacht and north Leinster before mid-day, and then petering out to scattered flurries further south. This band of snow will also begin to mix with hail, sleet and cold possibly freezing rain in some western and southern counties as it moves south. Heaviest snowfalls are likely to be about 3-5 cms over parts of inland Ulster, tapering down to about 1 or 2 cms in the inland southeast later. Highs will be restricted by the fog in some places to -2 C but around the coasts and in the southwest in general it should reach 2-5 C. Winds will be quite light or even calm as this precipitation develops and moves south but some west coast headlands will feel a slight westerly inflow of milder air for a while.

TONIGHT ... More fog, bitter cold and scattered flurries or snow grains, with lows generally -3 to -8 C. Dense freezing fog will lead to icy roads and pavements.

TUESDAY ... Foggy in some places for much of the day, and very cold again, with sunshine breaking through in a few spots, as scattered wintry flurries move from north to south in a developing NNW breeze of 10-15 mph. Highs only -2 to +2 C for most.

WEDNESDAY ... Slightly milder in the west and southwest, although possibly not much more than 5 C there; staying very cold with outbreaks of sleet or snow in the east, not too heavy (1-3 cms) as temperatures reach about zero to +2 C at peak after a morning low near -7 C.

THURSDAY ... Breezy or windy and cold with passing wintry showers, highs to about 5-6 C west and only 2-4 C east.

From FRIDAY to about MONDAY or TUESDAY, the models want to bring in some milder air ... I hope this is true to give you all a break from the bitter cold and melt some of the ice and snow, but there are two things that can go wrong with the "mild" concept (limited though it is anyway) ... first, there is strong high pressure forming nearby which could keep an inversion in place over the snow cover, and secondly, the models may just abandon this mild concept in a day or two and leave this high way out to the west with more of this modified arctic chill. We shall see how this plays out, but regardless, there are strong signals of a renewed blast of arctic air later, once this mild spell (or less cold spell) comes and goes.

Meanwhile, I think I overlooked my local weather yesterday (Saturday) -- it was sunny and cool then, and today (Sunday 5th) was also sunny to start, but it turned cloudy, with highs near 5 C. There is very little snow here at low elevations but plenty on the local mountains. It has also turned a lot colder in the eastern parts of the U.S. with heavy lake effect snow in a few spots. Otherwise, it's a dry cold.

Watch for updates and visit the ongoing discussion thread. I'm thinking that the fog and freezing mist may be a bigger hazard than the snow in some central and southern districts, but the snow may be significant by mid-morning in the northern half of Ireland and whatever holds together as far as Dublin might be arriving there around mid-day. My current prediction for Dublin would be 1-3 cms of snow.

GavinH

Thanks for the forecast. But does it not look like the frontal system has moved over to Scotland, or am I mistaken.

Keep up the great work.

glossy

no snow here in Dublin

Sheba891

Big snowfall just ending here in Letterkenny:)

Tae laidir

Snow?? Met Eireann says it's +5 degrees in malin.That 'percipitation' belt is moving a lot slower SEwards than expected.Wonder what will happen to it when it reaches Dublin?

TheMilkyPirate

I think alot of people here would prefer if this thread was kept to just MTs forecasts and keep all the chat and comments to the relevant threads.

It gets annoying having to wade through all the chat to find the forecast.

M.T. Cranium

UPDATE _ Monday, 6:20 p.m.
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The band of snow continues to advance very slowly south towards Dublin ... and reports indicate that snow gradually changes to sleet and a cold rain in this band further west ... but expect this liquid precip to change to snow as the band continues further south tonight as much colder air is spreading into the system from the north at higher levels, and there is more extensive cold air banked up in the southeast ahead of the front.

In general, I think this snow will hold together for most of the period to about 0600h before finally reaching the southeast ... this portends a period of three to six hours of moderate to heavy snow for many places south of the current location of the snow band and amounts of 5-10 cms with isolated 15 cms possible especially when a northeast wind develops to enhance the snowfall along the Dublin and Wicklow coasts later.

Will update again around 9:30 p.m. ... I'm sure most of you are watching the radar and have a good idea when the snow might begin in your location, but expect the forward speed of the frontal band to remain about 10-15 mph perhaps picking up to 20-30 mph later.

Tomorrow is still looking very cold indeed for almost all of the country, the southwest may struggle above 2 C but highs could average -2 C in the rest of Ireland.

Longer term has the same questionable looking warmup for the weekend followed by another cold plunge fairly early in the new week now.

lucy2010

Hi MT, Thanks for always giving such an accurate forecast. Follow you all year round - first thing I read every morning.
Just a query the radar is showing its just about finished. http://www.raintoday.co.uk/ But according to MET 3 hour its showing hasnt even passed us yet ( Im in Bray south of Dublin) Is there a second band of heavier stuff to come if we were to follow all the forecasts? Has is moved much quicker than expected ? We have freezing rain at the moment. Very light but even in 4wd its treacherous.

M.T. Cranium

This next batch of snow is not so much a front as an area of unsettled weather that will arrive with colder upper level temperatures. I think a lot of the moisture from it will fall over Ulster (incl Donegal) and nearby parts of Connacht and north Leinster, so would just suggest that its impact on Dublin is likely to be restricted to passing flurries. Before that all arrives tomorrow, there is the slight chance of a localized streamer band setting up later tonight that I am watching at present but so far no real signs of danger.

So once the current dissolving front is fully clear of the region, probably could expect mostly foggy and cold conditions to return, but nothing to help with the icy conditions until at least Thursday.

M.T. Cranium

Tuesday, 7 December, 2010
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TODAY ... Continuing very cold and mostly dry with some sunshine breaking through the fog and cloud ... snow may continue for a while in the southeast giving 2-4 cms further accumulation ... snow showers, mixing with sleet near the coast, will move into Connacht and Donegal, parts of north and west Ulster during the morning, also giving scattered outbreaks of 2-4 cms snow ... later this afternoon some streamers may develop near the Dublin and Wicklow coasts, brushing shoreline districts at times (this will need to be watched and updated, 5-10 cm potential) ... highs today will vary from about -2 C over central snow-covered regions, to +2 C around south and east coasts, Donegal and Mayo, to about +4 C in Clare, Kerry and Cork where any showers will be mixed (snow on higher slopes). Winds today will be moderate north to northeast (variable to start in southeast Ireland).

TONIGHT ... Clearing in most areas with a few streamers continuing near southeast and northwest coasts, lows falling to -8 or -10 C inland, about -3 C around the coasts including most of Dublin although the airport could be as cold as -7 C.

WEDNESDAY ... Continuing cold, a few flurries or sleety showers (in the west) with northerly winds backing to northwesterly, more cloud than sun, highs generally -2 to +4 C.

THURSDAY ... After another rather cold night near -5 C, a milder trend will set in ... the mildness may not be felt very much in some of the east-central counties that have heavy snow cover, but otherwise, highs will be about 5-7 C, and a slow thaw will develop especially where snow is not too deep at that point.

FRIDAY ... Partly cloudy and reasonably mild again, highs 7-10 C except perhaps 3-4 C over heavier snow where fog may persist ... some light rain may develop near the northwest coast and affect a few areas of Donegal and Mayo as winds become moderate westerly. This may be the mildest day of the month (or Saturday).

SATURDAY ... Continuing rather mild but winds falling off to light southerly, the nights through this spell may remain sub-freezing, except near the west coast, and any thaw will be gradual and could end at about this time. Highs will vary from 4 to 8 C with the milder readings south and west coast.

SUNDAY ... Slowly cooling down again in clear to partly cloudy weather, light east winds, highs 3-6 C and morning lows quite possibly falling back to about -6 C or so with dense fog possible.

OUTLOOK ... Turning quite cold again in an easterly flow, possibly rather variable mid-week before even colder weather arrives from the north.

The weather here on Monday (6th) was cloudy and rather mild with a high of about 8 C. Rain is expected by morning. It continues very cold east of the Rockies across most of North America.

M.T. Cranium

UPDATE _ Tuesday, 4:30 p.m.
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Scattered outbreaks of snow will continue this evening in the southeast, heavier in areas west of the Wicklow Mountains as well as in some parts of coastal Wicklow. A mixture of rain, sleet and wet snow will continue in some coastal areas around Dublin and Wexford. Some hail or snow from streamers could develop later this evening in Meath and Dublin, but mostly after 8 p.m. so watch for updates on that potential.

There will also continue to be a few scattered wintry showers near the northwest coasts this evening.

Tomorrow, while still rather cold, looks like being more transitional for showers as temperatures generally rise about two degrees, but a more organized thaw will begin on Thursday. This will probably remove the snow cover where it is currently 10 cms or less (over the period Thursday to Saturday) but deeper snow cover will probably persist, in part because it will anchor colder air near the ground in an inversion that will create a blanket of fog and somewhat cooler temperatures than most of the country will see (those being 7-10 C).

TURRICAN

So MT is the cold front covering europe going to come back
Or is there more powerful warm stuff over the Atlantic which could be more dominant?

M.T. Cranium

The milder spell in some ways leads to its own downfall by swelling up high pressure so that as soon as it shifts away to the west, another surge of cold air is likely from a generally northeast direction -- the models at this point have slightly different details but this is the essential outcome on all of them -- three days of somewhat milder weather, then back to colder conditions.

By the way, looks as though streamer activity in the Irish Sea may be either weak or non-existent but keeping an eye on it, wind direction is slowly improving for this to set up.

H2UMrsRobinson

M.T. Cranium wrote: »

The milder spell in some ways leads to its own downfall by swelling up high pressure so that as soon as it shifts away to the west, another surge of cold air is likely from a generally northeast direction -- the models at this point have slightly different details but this is the essential outcome on all of them -- three days of somewhat milder weather, then back to colder conditions.

By the way, looks as though streamer activity in the Irish Sea may be either weak or non-existent but keeping an eye on it, wind direction is slowly improving for this to set up.

You get spoilt with an epic streamer once and you want them all time...:)

Vizual Pics

M.T. Cranium wrote: »

The milder spell in some ways leads to its own downfall by swelling up high pressure so that as soon as it shifts away to the west, another surge of cold air is likely from a generally northeast direction -- the models at this point have slightly different details but this is the essential outcome on all of them -- three days of somewhat milder weather, then back to colder conditions.

By the way, looks as though streamer activity in the Irish Sea may be either weak or non-existent but keeping an eye on it, wind direction is slowly improving for this to set up.

Great updates as usual MT, just curious why streamers rarely affect North Mayo regions when they have a whole tract of sea to cross on a northerly wind, is it because a northerly wind is warmer than an easterly and hence less convection?

M.T. Cranium

Yes, a better setup for north Mayo seems to be a strong northeast wind that has come down from northern Scotland. The problem with long-fetch northerly winds is that the air mass spends 3-4 days over the Atlantic and is likely to be modified enough to be warm enough for hail or rain showers. Also, for sea-effect as with lake-effect, the ideal setup is for land-cooled air with very low dew points to spend 6-12 hours over open water, modify to the extent needed to form streamers, then hit land cold enough to dump most or all of their load as snow. I would imagine that you could get some extreme cases with very strong northerly winds that would dump a lot of snow in Mayo, the strong winds might allow the arctic air to get from ice or land sources to Ireland in less than two days and this might be alright for snow streamer development to hold together.

I think it's worth reflecting on the fact that, even in the coldest phases of the Maunder minimum or Little Ice Age period, it was probably never colder than it has been the past ten days to two weeks at this early stage of winter. Of course, it has been colder in mid-winter, but not by that much.

From a statistical point of view, it seems quite possible that a colder ten day stretch will materialize, because it's rare for the coldest part of winter to come this early.

up for anything

M.T. Cranium wrote: »

From a statistical point of view, it seems quite possible that a colder ten day stretch will materialize, because it's rare for the coldest part of winter to come this early.

I'm loath to thank you for that but I will because I will be a wise virgin and order lots of oil for my lamp.

M.T. Cranium

Wednesday, 8 December, 2010
_________________________________

A thaw is coming -- but it will have the least effect where the snow is deepest. The deeper snow will create low-level inversions that will trap chilly air and fog and slow down any melting. The areas that have no snow today will warm rather nicely to about 8-11 C later this week. Areas that have a small amount of snow should see a total melt; areas with more snow will keep at least half of that snow before temperatures turn colder again after the weekend. At least the modified warmth should melt ice on roads and pavements fairly quickly and make getting around a lot easier in some areas.

TODAY ... Although continuing cold, a slight warming will be evident in the west with highs of 4-7 C and scattered mixed showers near the coast. Further east, one more cold day is likely, with some lingering freezing fog over central and southeast snow-covered counties. The east coast will see some sunshine at times, with offshore streamers possibly brushing parts of the coast south of Dublin ... radar watching time in Wicklow and Wexford ... but much of the time this activity will be just offshore. Highs today over the snow will be about 0-1 C and on the east coast 3-4 C.

TONIGHT ... Some clear patches and dense freezing fog over snow, lows to about -4 C, dense fog may create icy roads and near zero visibility. Other regions about -1 C with variable cloud, a few showers in the northwest at times, icy inland, a slow thaw near the west coast.

THURSDAY ... Partly cloudy with some milder sunshine in parts of the west and southwest, highs 7-10 C ... dense fog possible over snow in central counties, highs 2-5 C ... some low cloud, some weak sunshine east and southeast coasts, a bit milder, highs 4-6 C.

FRIDAY and SATURDAY will continue mild with roughly the same regional variations as above, possibly a degree or two milder as some of the snow melts, but continuing dense fog, with some overnight lows falling back well below freezing over the snow pack. Highs may reach 8-12 C near west coast and southwest counties (but local fog in valleys always a risk).

SUNDAY will continue a bit on the mild side and relatively dry, with a gradual cooling trend from light east winds setting in, highs generally 3-5 C over the snow, 6-9 C elsewhere. It will be partly cloudy to overcast but dry apart from some drizzle or fog condensation.

OUTLOOK ... turning colder again, with east winds, some risk of snow in the southeast mostly, then possibly a bit milder mid-week in advance of even colder conditions due to sweep in from the north around the 16th or 17th.

The weather here on Tuesday was mild and windy with rain, highs near 10 C. It continues quite cold across most of North America east of the Rockies, with highs only 0-3 C on the east coast and near -5 C in the Great Lakes region where there have been some massive snow squalls in a few locations in W-NW winds.

thetonynator

M.T. has been nominated as a legend of the boards here. Vote for him if you think he is a legend of the boards!!!

alfalad

thetonynator wrote: »

M.T. has been nominated as a legend of the boards here. Vote for him if you think he is a legend of the boards!!!

I'm new to this forum, like many during this cold spell, but he seems to be extremely accurate and detailed, so my hat is off to the man/woman. But my curiosity is getting the better of me, is he/she Irish? Why does he/she take such an interest on the weather in Ireland? What background/qualification does he/she have? Do they work in the weather industry? etc. Again this is just curiosity and his forecasts are eagerly anticipated and think they are sport on!

I also appreciate that the idea of usernames is to protect identity so that I certainly am not asking!

Iancar29

Hey M.T,
All this fog that we are gettin and thats forecast, is it radiation fog due to the warmish air passing over the cool snow covered surfaces?... or is it something else?

It truely gives a perfect winter picture scenery.

Darwin

alfalad wrote: »

I'm new to this forum, like many during this cold spell, but he seems to be extremely accurate and detailed, so my hat is off to the man/woman. But my curiosity is getting the better of me, is he/she Irish? Why does he/she take such an interest on the weather in Ireland? What background/qualification does he/she have? Do they work in the weather industry? etc. Again this is just curiosity and his forecasts are eagerly anticipated and think they are sport on!

I also appreciate that the idea of usernames is to protect identity so that I certainly am not asking!

If MT doesn't mind, this post will probably answer all your questions

alfalad

Darwin wrote: »

If MT doesn't mind, this post will probably answer all your questions

Curiosity satisfied! Thank you! Again the depth and knowledge that comes across is extremely impressive and given the fact MT is in Canada I couldn't help but ask. Hope I didn't come across as nosey and possibly should have kept quiet and been grateful!

YESROH

I always wondered too but was too afraid to ask. Your doing a great job.