| Possible Wintry Weather For East - Mon | |
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| Tweet Topic Started: January 27 2012, 12:05 PM (742 Views) | |
| Mark (IWO) | January 27 2012, 12:05 PM Post #1 |
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This thread is dedicated to general discussion about the prospects of wintry weather for higher ground in eastern counties later on Sunday and into Monday. Confidence of wintry arriving occuring is low at about 30% but could increase significantly if models continue to upgrade today. The 06z GFS upgrades cold potential for that same period bringing cold further west than shown in the 0z. Here is a comparison of the two charts at midnight Sunday (0z run first and 06z run second). The GEFS seems to have followed the lead of the ECM, GEM and UKMO. ![]() ![]() Peter indicated in his morning forecast that wintry weather could affect parts of the East coast during this period and on into next week. SUNDAY ... Mostly cloudy, occasional light rain, may mix with wet snow or sleet in parts of eastern Ulster and inland north Leinster, and on higher parts of Dublin and Wicklow mountains. Cold across the east, winds backing to SE at 10-20 mph, highs 3-6 C. Variable cloud, some showers possible, milder further west, highs 7-10 C. OUTLOOK for NEXT WEEK ... Much of the time, there will be a marked temperature contrast from east to west as a rather diffuse front will settle in over the Irish Sea and eastern Ireland. This will lead to outbreaks of sleet, with snow possible at times especially higher elevations, but largely confined to eastern Ulster and northeast Leinster. Dublin will remain very close to this frontal boundary, and further west it will tend to stay mild except for brief intervals when the front drifts further west. Temperatures to the east of the front will be as low as -2 C at times, and generally in the range of 1-4 C. To the west, it will stay considerably milder, around 6-9 C on average, and 10 or 11 C on outer west coastal margins. This pattern could persist for several days or even the entire week. Confidence is rather low concerning details, watch for updates because as we get closer to the time, the forecast models may begin to pick up on the details which will help us with the timing. I still consider it quite plausible that a snowfall event could develop eventually, as things are in a rather fine balance between a weak Atlantic flow trying to hold its position, and a very wide-ranging cold blocking high which could at some point begin to push west more vigorously. |
| The coldest winter you will ever experience is a summer in West Clare. | |
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| Mark (IWO) | January 27 2012, 02:02 PM Post #2 |
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Uncertainty defined by UK Met Office Outlook for Sunday to Tuesday: Some uncertainty but eastern parts of the UK mainly dry and cold with overnight frosts. Elsewhere, "cloudy with rain at times and a risk of some snow". Updated: 0605 on Fri 27 Jan 2012 |
| The coldest winter you will ever experience is a summer in West Clare. | |
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| pistolpetes11 | January 27 2012, 03:59 PM Post #3 |
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Not sure if you can put a youtube clip on here , but I made a short vid of the snow accum charts for over the weekend , based on the 6z gfs Not to be taken as gospel by any means. ADMIN NOTE: Nice vid, Pete. To embed videos use the FLASH option instead of the URL option. Just copy the url in after click FLASH. |
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| cherryghost | January 27 2012, 04:50 PM Post #4 |
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There's still too much variables at the moment to determine anything. However the last 2 days have seen the cold air shift slowly further westwards in the charts. It might be only a matter of time, but the East coast may be onto a good dumping of snow, depending how slow the system moves (or doesn't move!) over the country. |
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| Mark (IWO) | January 27 2012, 04:58 PM Post #5 |
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The 12Z GFS is often regarded as the most accurate of the four daily outputs from the model. The potential is there for a dumping for someone in the UK and Ireland. The potential is also there for mild muck. If the GEFS backtracks at 12z (rolls out from 3.30pm) then that is more than likely that for the next week or so. However, I am going for the GEFS to either hold it's own or follow the ECM/UKMO with an even further progression westwards of cold (not severe cold) within the 96hr timeframe. |
| The coldest winter you will ever experience is a summer in West Clare. | |
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| Mark (IWO) | January 27 2012, 06:10 PM Post #6 |
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Slight progression westward of cold airmass by Sunday night really presenting a potential battleground scenario with cold air pushing up a warmer Atlantic airmass. One to watch but interesting to see that the GEFS looks to have completely backed off a swift return to zonal conditions by Sunday. Looks like the west will remain much milder than the eastern half of the country at this point 1pm on Sunday, Snowline reaches Irish sea
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| The coldest winter you will ever experience is a summer in West Clare. | |
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| ConorLK | January 27 2012, 06:15 PM Post #7 |
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Still very much underwhelmed by what I've seen from an IMBY point of view, looking like a pretty average week for most of us away from the east coast with plenty of rain. A fascinating situation to watch though and with the continued westward march of cold over the past few days there's still potential later on. The 12z GFS seems to have gotten stuck at 48h and I have to head out for a while so guess I'll find out the latest twist later! |
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| Mark (IWO) | January 27 2012, 06:22 PM Post #8 |
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It's all about the trend, Conor and things most likely will not happen overnight for Ireland when a potential easterly is brewing. It will turn gradually cooler rather than cold very quickly. The trend is pointing in the direction of a potential prolonged cold spell for at least Britain. When the source of this cold is the East then of course the potential for Ireland is significant. Very interesting times ahead as the GEFS has upgraded the cold outlook on two successive runs. It is now more in line with the ECM, UKMO and GEM. The latest upgrade for midweek brings -10 uppers over England. Compare the most recent run with the previous run below. ![]() ![]() |
| The coldest winter you will ever experience is a summer in West Clare. | |
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| ConorLK | January 27 2012, 07:31 PM Post #9 |
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Couldn't resist a quick look and yeah another twist indeed! Big upgrade again from GFS, UKMO and GEM which is quite a shock considering what we were seeing just last night. Important to remember that this time last night everyone was saying that it was pointless looking beyond 72h and today as soon as some proper cold shows up that idea is thrown out the window, still massive uncertainty with such big swings over a short period. But enough of the negativity, after a pathetic January it looks as if we're finally set for a taste of winter which I'll welcome with open arms if it keeps the Atlantic away for a week
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| Mark (IWO) | January 27 2012, 07:36 PM Post #10 |
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Because the models could not agree on anything. They are pretty much all singing from the same icy hymn sheet now Best model run of the winter. All downhill from here (slalom perhaps?)
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| The coldest winter you will ever experience is a summer in West Clare. | |
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| ConorLK | January 27 2012, 08:00 PM Post #11 |
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But they were largely in agreement on the cold making as far as eastern England leaving us with nothing all week, that seems to have been totally wrong but just shows how poorly they're performing. This morning was the first time the easterly flow actually beat the Atlantic. Anyway GFS was a massive cold outlier with ensemble runs diverging as early as tomorrow so you can pretty much bin the 12z for anything after the weekend![]() Onwards to the ECMWF then, hopefully it'll provide a bit of clarity for next week! |
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| Mark (IWO) | January 27 2012, 08:22 PM Post #12 |
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i do believe we will see a transition to colder weather but think it will take another week to take hold here. models are underestimating the Atlantic and the fact it has controlled our weather for months. cold will arrive as all models are tending that direction, but patience may be required |
| The coldest winter you will ever experience is a summer in West Clare. | |
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| Patrick (IWO) | January 27 2012, 10:41 PM Post #13 |
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ECMWF 12z 850's from Sunday through to Wednesday next: ![]() Keeps any substantial cold just to our east and never really gets in thereafter. Very similar to yesterday's 12z run in that it amplifies the Atlantic thereafter. Will be interesting to see how this run sits within the ensembles when they are released. |
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| pistolpetes11 | January 27 2012, 10:46 PM Post #14 |
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Hopefully this will come out properly Edited by pistolpetes11, January 27 2012, 10:47 PM.
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| Fergal (IWO) | January 28 2012, 03:30 PM Post #15 |
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The overall outlook has not changed for me all week, and I still reckon the northeastern Canadian trough will persist and keep the Atlantic just strong enough the keep the major cold at bay over the next couple of weeks. We may get some cold lapping up to our shores, like wavelets on a beach, but I think the tide will go out and take them with it. Regarding the next 48 hours, it is really almost a perfect setup for snow in the east, but we're just not quite in the right position. But I can see the Wicklow mountains getting several inches of snow overnight tomorrow and through Monday. I would not be surprised to hear of several people stranded up in Sally Gap come Monday evening. In this setup, using theta-e and w values is not a reliable snow forecast, for the following reason. The GFS forecast sounding for Dublin Airport for 3pm Monday shows a perfect heavy wet snow setup, but just not quite to sea level. The deep saturated cold isothermal layer from 950 to above 700 hPa shows lots of preciptable water available, all of it below 0 °C. Calculating 850 theta-w from this sounding (by following the 850 hPa wet-bulb temperature down to 1000 hPa along the grey dashed saturated adiabat) yields +5 °C, which would normally translate to snow above around 500-600 metres, but we can see that the layer below 850 hPa shows a colder than dry-adiabatic profile, so snow should survive down to say 250-300 metres. Also, because of the saturated isothermal layer, thickness values will be higher than what we would be looking for, so instead of my usual sub-522 dam I would be more inclined to say 524 dam may be the snow descriminator. Whatever about snow, the northeast and east should see some pretty big precip totals over the next 48 hours, and I would say that eastern Ulster and eastern Leinster could see some sleet or very wet snow down to low levels for a time. It most likely won't stick, but as I said, the higher hills above around 300 metres should see some action. The Welsh mountains and moors should be fairly treacherous too.
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| mickger844posts | January 28 2012, 04:41 PM Post #16 |
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Excellent analysis Fergal. As you elude to in your post lots of rain is due to fall over a 48 hour period and that could be the story this week. Still all to play for i feel but should be an interesting week ahead no matter what the final outcome is. |
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| Mark (IWO) | January 29 2012, 01:53 PM Post #17 |
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Looks like snow for higher ground in Wales overnight and perhaps the highest peaks in Down![]() Snow possible above 150m in East Ulster tomorrow night and during early Tuesday ![]() |
| The coldest winter you will ever experience is a summer in West Clare. | |
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| Fergal (IWO) | January 29 2012, 02:31 PM Post #18 |
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I think it's a slighlty milder outlook for tomorrow, with snow only above around 400 metres in Ulster and 500-600 metres in Wicklow. The Welsh and Scottish hills will get the brunt. The ECMWF snowfall chart for later tonight shows chaos in the Welsh mountains.![]() |
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| Mark (IWO) | January 29 2012, 11:05 PM Post #19 |
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While the highest peaks of the Mourne Mountains and Wicklow Mountains will see some snow, the rest of the east coast will see sleety rain tomorrow eve/night. There is a possibility of some back edge snow for inland parts of Carlow, Waterford and Wexford as the front dissipates. The UK is a different ball game. Latest from UK WEATHER Issued For: Snowfall, Dangerous Conditions Valid: Sunday 29th - Monday 30th January Through the course of Sunday an advancing area of cold air will push Westwards across the United Kingdom, at the same time a weather front will attempt to push into Western areas and as this moisture clashes with the colder air it's likely to begin to turn to snowfall. Key areas look likely to be across Wales, particularly above 250M where we could see anything up to 10cm in exposed locations, areas below this elevation are likely to see a mix of rain, sleet and snow with accumulations locally of 2-5cm, though this is deemed fairly unlikely. Orange Zone - Weather Warning Issued: Those in the orange zone above 250M can expect to see a period of moderate-heavy snowfall through Sunday night and into Monday morning, local accumulations of up to 10cm seem likely and this could cause travel problems across higher routes, lower lying areas may see small local accumulations but a general wintry mix is more likely. Yellow Zone - Weather Advisory Issued: A weather advisory has been issued for parts of South-West England, as this weather front begins to clear Southwards, colder air will continue to mix in and could produce some snowfall for a time, particularly across higher levels, accumulations of 5-7cm are possible locally. Lower levels again likely to see a mixture of rain, sleet and possibly snow during heavier bursts, but accumulations are unlikely here. |
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