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10-01-2010, 14:40   #751
Ally Dick
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Originally Posted by glimmerman123 View Post
If this mild weather breaks through will we see another cold spell before the winter is over or is the mild weather going to last for weeks?
Please god we will get several months of decent weather now. This bad weather has been no fun at all
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10-01-2010, 14:57   #752
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I just hope we don't go back to the heavy rain and floods we had a few weeks back. I can't see us having several months of fine weather after this cold spell.
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10-01-2010, 18:24   #753
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UPDATE _ Sunday, 6:20 p.m.
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Currently, milder air has pushed into most parts of Ireland, although remnants of the bitter cold are found in the southwest where snow continues to accumulate. The situation is now rather complicated; there will be a slight cooling of the general easterly flow but a decrease in precipitation due in part to a slacker wind gradient by early Monday. The net effect of all that is likely to be occasional light sleet, snow grains, or other mixed forms of precipitation, not accumulating very much in any case, with temperatures fairly steady in the 0-3 C range until late Monday.

Then, a surge of milder air will arrive on strong SE winds (30-50 mph) with periods of rain that may turn rather heavy in the south. Temperatures by Tuesday morning will be up to near 8 C in the southwest, 6 C in the southeast and east, about 5 C central and west, and 3 C in Ulster. At higher elevations it won't warm up that much, and some of the heavier snow packs on hills and mountains may remain intact, but otherwise one could envisage a near total meltdown of the snow as well as a releasing of any freeze in the ground, after a few hours of the mild rainy weather. The results are likely to be minor flooding in places, and a general clearance of the roads and pavements except for some higher secondary roads which may remain icy.

The rest of the week then looks a bit on the cool, foggy side again as a weak further push of Atlantic air begins to mix with remnants of cold air still lurking over parts of the U.K., all of which combined may result in a very low cloud ceiling and temperatures near 2 or 3 C. A further thaw and rainfall with strong winds will follow, according to the model runs this morning that is, by about Friday night or Saturday.

Just a note about the Tuesday system -- it has the potential to change at the last moment if colder air takes firmer hold over the region Monday, and it could become a snowstorm at the last moment at least in the north and east, I think the mild, rainy interval is more certain in the south and west at this point. I don't see that much cold air locking in on Monday to hold this system back from eastern and northern counties, but possibly others have a different idea as I am hearing all sorts of forecasts. So I should at least underline the uncertainty involved here.

Also, this system tends to die out as it passes west of Galway late Tuesday; it isn't likely to be followed by a flood of mild, Atlantic air, but rather, it will come along and do its business with a brief shot of energy, then skulk away towards Iceland leaving Ireland with a decaying swirl of moist maritime air; winds may never veer from SE to S or SW in eastern or northern counties, but just remain SE backing to E once the disturbance fades away. The wind shift further west will be gradual and rather subdued (not likely to see SW gales, just SE gales as the storm approaches).

Anyway, I will keep watching and updating as required.
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11-01-2010, 03:54   #754
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BBC are now giving a warning for heavy snow for southern and eastern(Irish) counties on Tuesday.
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11-01-2010, 04:47   #755
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Monday, 11 January, 2010
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This forecast may be updated at any time ... bear in mind that the unfolding situation will be subject to significant forecast changes if the systems are even a small distance removed from their model predicted positions.

TODAY will continue with similar trends to Sunday, although the heavier snow in the southwest should abate, becoming more of a sleety drizzle by morning. Most other regions will be seeing a mixture of rain, sleet and wet snow, with snow accumulations only on higher ground, as temperatures hover around 2 or 3 C. A few colder areas will see dense fog forming as this milder air sits over deeper snow cover. Winds will ease somewhat for most today, while increasing in the southwest due to better mixing of the air there. This will leave all regions with ESE winds of about 15-25 mph.

TONIGHT will have a low overcast and patchy dense fog over hills mostly, with sleet or wet snow at times, turning to a steady rain in the south after midnight. It is possible that a heavy wet snow will develop especially at elevations above 200 metres in the southeast and central counties before warmer air arrives. It is also likely that a nasty mix of freezing drizzle, sleet and snow will hit Ulster and some other north-central counties. The overnight lows will be near 2 C in the south and zero elsewhere.

TUESDAY will see moderate to heavy rain moving north, replacing any sleet or snow rather quickly after sunrise. Winds will start increasing before sunrise in the south and just afterwards in the east and central to western counties, reaching SE 30-50 mph. As temperatures rise to about 8 C in the south and 5-6 C in the east, central and west to northwest counties, most of the existing snow and ice will rapidly melt. This process will be slower in Ulster and some other north-central counties as the milder air only arrives late in the day and pushes temperatures there to about 4 C. Rainfalls of 20-30 mms appear likely. Flooding is quite possible due to stream overflow, or urban ponding around snow banks -- you may be able to avoid this locally by clearing your street drains on Monday if possible. Also, watch for landslides, mudflows or bridge washouts on secondary roads especially near mountain drainage, as a lot of melted snow and rain will be combining to turn small streams into torrents.

Note there is some uncertainty built into this forecast, if the low were to prove slower or weaker, a band of heavy snow or sleet would probably linger through much of the day in some northern and eastern counties.

TUESDAY NIGHT into WEDNESDAY, the winds will rapidly die down, low cloud and drizzle will remain from the storm, and temperatures will drop back to about 3 C so melting will slow again. Higher mountain snowpacks will probably survive this brief thaw but will become unstable (not sure if Ireland has ever seen avalanches as such, but minor snowslides coming with mudslides would seem quite possible in this weather). Wednesday will continue overcast, gloomy and rather foggy in places, with the slowly melting snow and ice adding moisture especially in the north. Highs will be 3-5 C.

THURSDAY appears likely to remain about the same, overcast with some fog, light winds, and temperatures in a fairly narrow range of about 2-6 C, unless it happens to clear a little on Thursday morning, in which case a frost and freezing fog could easily reappear.

FRIDAY-SATURDAY now appear likely to warm up even more, with a strong southerly flow, temperatures rising to 11-13 C in many areas, and moderate rain at times. This may cause more minor flooding if there's any snow left to melt, and it could even start to melt snow at higher elevations rather quickly. This part of the forecast is of course subject to more uncertainty than the shorter term. It would not amaze me if we were rolling back this strong thaw later in the week, but this is what the early model runs have been saying.

We already have this sort of weather here and it's not doing much good to the lower Olympic venues, perhaps we will have to move them to Mayo after all. It was about 12 C here on Sunday and quite comfortable outside in just a light jacket (and of course some other clothing).

I have no doubt that there will be a wide range of opinions about what's ahead for the next few days, so just remember, this is one idea out of many, and I acknowledge the uncertain nature of the forecast.
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11-01-2010, 10:46   #756
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UPDATE _ Monday, 1045h GMT
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I will attempt to update tomorrow's developing weather situation with each new run. Based on the 06z GFS, I am not seeing anything radically different from the forecast above. Some details that I have also discussed in the other threads ...

The storm will probably have a rapid onset around 0300-0600h as moisture sweeps in from the south. This may begin as sleet or heavy wet snow in some eastern counties at least some distance inland and 100-200m above sea level. It may remain mostly snow in counties north of Dublin and generally to the east of Roscommon. This may lead to snowfalls of 5-15 cms on Tuesday in those counties, mainly in Ulster and possibly Westmeath and inland parts of Meath, Longford and possibly a few other areas.

Otherwise, expect the storm to bring a driving rain (with this mixed start that occurs mainly before people are generally up and about) and winds increasing to SE 30-50 mph in general, but possibly 40-65 mph in Waterford and Cork where a very strong gradient is indicated by 0900-1200h.

Temperatures will likely rise rapidly in the south to 6-8 C and more gradually around Dublin to about 5-6 C, this being about the same for a string of counties across south-central Ireland from about Laois to Clare. Rainfalls of 30-45 mms are now indicated, and where snow is present today, you could reasonably expect some flooding to begin mid-afternoon Tuesday lasting well into Wednesday as the rate of melt slows down.

By late afternoon and evening, colder air is going to be wrapping around the storm from the Atlantic and possibly turning some of the rain back to sleet or heavy wet snow before the whole thing winds down with lighter precip of a mixed variety on Wednesday, in temperatures closer to 2-4 C.

There is also the risk of some thunder and hail embedded in this strong storm system in Kerry, Cork, Waterford, Wexford and inland to about Shannon to Thurles. I would imagine there could be some thunder further east but likely without the hail or possibly very strong wind gusts that may affect the south central counties.

Uncertainty remains significant, some forecast models are indicating a slower mixing of snow and rain which would put the accumulating snow a bit further south in the morning. I still have the feeling this is going to develop rapidly and force the arctic front to the north of Dublin but not that far north. The hail and thunder risk would be along the main storm system occluded front that will extend southeast from the low centre as it moves north.

Next update likely to be around 1600h.
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11-01-2010, 10:53   #757
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THUNDERSNOW ALERT.

not impossible.
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11-01-2010, 11:57   #758
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Quote:
Originally Posted by M.T. Cranium View Post
UPDATE _ Monday, 1045h GMT
_______________________

I will attempt to update tomorrow's developing weather situation with each new run. Based on the 06z GFS, I am not seeing anything radically different from the forecast above. Some details that I have also discussed in the other threads ...

The storm will probably have a rapid onset around 0300-0600h as moisture sweeps in from the south. This may begin as sleet or heavy wet snow in some eastern counties at least some distance inland and 100-200m above sea level. It may remain mostly snow in counties north of Dublin and generally to the east of Roscommon. This may lead to snowfalls of 5-15 cms on Tuesday in those counties, mainly in Ulster and possibly Westmeath and inland parts of Meath, Longford and possibly a few other areas.

Otherwise, expect the storm to bring a driving rain (with this mixed start that occurs mainly before people are generally up and about) and winds increasing to SE 30-50 mph in general, but possibly 40-65 mph in Waterford and Cork where a very strong gradient is indicated by 0900-1200h.

Temperatures will likely rise rapidly in the south to 6-8 C and more gradually around Dublin to about 5-6 C, this being about the same for a string of counties across south-central Ireland from about Laois to Clare. Rainfalls of 30-45 mms are now indicated, and where snow is present today, you could reasonably expect some flooding to begin mid-afternoon Tuesday lasting well into Wednesday as the rate of melt slows down.

By late afternoon and evening, colder air is going to be wrapping around the storm from the Atlantic and possibly turning some of the rain back to sleet or heavy wet snow before the whole thing winds down with lighter precip of a mixed variety on Wednesday, in temperatures closer to 2-4 C.

There is also the risk of some thunder and hail embedded in this strong storm system in Kerry, Cork, Waterford, Wexford and inland to about Shannon to Thurles. I would imagine there could be some thunder further east but likely without the hail or possibly very strong wind gusts that may affect the south central counties.

Uncertainty remains significant, some forecast models are indicating a slower mixing of snow and rain which would put the accumulating snow a bit further south in the morning. I still have the feeling this is going to develop rapidly and force the arctic front to the north of Dublin but not that far north. The hail and thunder risk would be along the main storm system occluded front that will extend southeast from the low centre as it moves north.

Next update likely to be around 1600h.
M.T. - your forecasts on here have been remarkably accurate over the course of this cold spell - far better than Met Eireann or MetO IMO so thankyou for providing this invaluable service! What do you think is the chance of seeing snow here (Bangor) tomorrow. It's been raining all morning here with a temp of 3.5C, dew point 0C - are these temperatures likely to fall enough to produce snow tomorrow do you think? The rain today has reduced my confidence somewhat!
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11-01-2010, 17:33   #759
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That is a very good question, I'll try to give an answer in this update.

The 12z GFS and GEM runs have not added much new information. So I am going to maintain the forecast above, but stressing the uncertainty about snowfall in Ulster and other counties generally north of Dublin. Much will depend on how the storm comes together overnight, with rapid development expected well to the south of Valentia after midnight, and this weak warm advection as described in Snowjon's post above, extending even into areas where snowfall might develop. Quite often a storm like this will pull back some of the colder air that has been gradually retreating, as it creates a stronger circulation. This is probably the thinking behind any snowfall forecasts, even those which are more aggressive than mine (if those still exist, I haven't been reading the threads yet). Now I don't see this storm pulling back the arctic front 200 miles but 50-100 seems possible, which is why I think there could be an outbreak of heavy snow in these northern counties late tonight and through parts of tomorrow. On the other hand, the coast may not see as much snow as places further inland, as the wind will tend to be blowing in from the still-warmish waters, so I would hazard the guess that Bangor near sea level would see more sleet than snow and possibly changing to rain.

Otherwise, staying with the forecast from earlier and taking another tour of the guidance and the threads on various forums to see what's happening and what people are thinking. More updates if they seem necessary.
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11-01-2010, 17:45   #760
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Originally Posted by M.T. Cranium View Post
That is a very good question, I'll try to give an answer in this update.

The 12z GFS and GEM runs have not added much new information. So I am going to maintain the forecast above, but stressing the uncertainty about snowfall in Ulster and other counties generally north of Dublin. Much will depend on how the storm comes together overnight, with rapid development expected well to the south of Valentia after midnight, and this weak warm advection as described in Snowjon's post above, extending even into areas where snowfall might develop. Quite often a storm like this will pull back some of the colder air that has been gradually retreating, as it creates a stronger circulation. This is probably the thinking behind any snowfall forecasts, even those which are more aggressive than mine (if those still exist, I haven't been reading the threads yet). Now I don't see this storm pulling back the arctic front 200 miles but 50-100 seems possible, which is why I think there could be an outbreak of heavy snow in these northern counties late tonight and through parts of tomorrow. On the other hand, the coast may not see as much snow as places further inland, as the wind will tend to be blowing in from the still-warmish waters, so I would hazard the guess that Bangor near sea level would see more sleet than snow and possibly changing to rain.

Otherwise, staying with the forecast from earlier and taking another tour of the guidance and the threads on various forums to see what's happening and what people are thinking. More updates if they seem necessary.
That sounds very like a very plausible outcome. It's interesting how close the wintry stuff is - earlier today a litle pocket of cooler air reduced the air temp to 2.6C and the dew point to -0.8C which allowed some sleet to reach the ground. Since then, its been rain all the way - currently air temp/dew point is 2.9C/-0.2C. As you mentioned in some previous forecasts - a very messy picture this week!
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11-01-2010, 18:30   #761
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Well it is a close call for sure, I've been noticing that the Isle of Man has been reporting snow especially (the man says) above the lowest elevations, and it hasn't warmed up at all away from the southwest tip of Wales, Cornwall has seen a bit of a warming down in the lower parts so an arctic front is developing along a line from just marginally east of Belfast running approx SSE to the Channel Islands, and when this low starts pulling in a stronger circulation, that front is bound to move west rather than east overnight -- this is why some are forecasting snow quite a way back into the somewhat milder air mass that is stuck between the arctic front and the developing frontal wave (those fronts are still over a hundred miles offshore and won't make landfall until after 0600). If the Irish Sea wasn't there to complicate the situation, I might be quite tempted to say snow backing into the circulation but that's the foundation of this forecast, that the arctic front will buckle and sag further south over land in Ireland than over the sea.

Then that buckled front will probably get pushed back north to some extent, stall out again, the other fronts will slowly weaken, cold air will wrap around the whole mess -- I'm getting a headache just thinking about it. Some places are going to see an almighty mess out of this, not cold enough to snow properly and not warm enough to thaw, it will just add more slop that could later freeze.

Also I am concerned about the rainfall potential on Friday into early Saturday from the latest guidance, falling on what is likely to be a saturated countryside just in the last stages of a complete thaw. Maybe that will downgrade closer to the time.
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11-01-2010, 20:38   #762
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Hi MT are we likely to get any of this low in the Galway area ??
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11-01-2010, 21:31   #763
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Sky are forecasting serious amounts of snow for Devon, Corwall, South Wales and parts od southern Ireland tomorrow from about lunchtime onwards but next to no snow from RTE - strange!
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11-01-2010, 21:35   #764
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At 6pm news they said the Munster and Leinster would get all this rain and wind now at the 9pm news its going to move up over the whole Country.
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11-01-2010, 21:36   #765
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Sky are forecasting serious amounts of snow for Devon, Corwall, South Wales and parts od southern Ireland tomorrow from about lunchtime onwards but next to no snow from RTE - strange!
Not strange GSF - more a good sign that we'll have a white out in much of the country.
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