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26-11-2010, 19:49   #1
Sleety_Rain
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Cold Spell Forecasts and Synoptic Forecast Discussion - 26/11/1020 onwards

Please use this thread to discuss the medium term outlook for the Cold Spell and Detailed chart analysis.

And use this one for more general Snow Reports & Chat.

Good Luck
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26-11-2010, 20:19   #2
 
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Snow predicted on the north east and west coasts tonight. The Midlands and south/south west shouldn't see any snow.



A pool of very cold air over all of Ireland tomorrow and Sunday which would ensure any precipitation would be snow. Could be heavy at times over the weekend. There could also be a bit of a dumping on the far south east according to the models tonight.



For the 1st of december the cold has continued to say with us and has become much more pronounced. -8 uppers all over Ireland with pretty much all falls during the period of snow.



This doesn't sound like RAMMMMPPPPINNNNNNNGGGG does it?
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26-11-2010, 20:22   #3
Artfu1Dodger
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The models seem to be droping the idea of a deep low pressure system coming up into south east england.
Heres the GFS, UKMO and ECM at 120hrs.
Keeps us in a very cold easterly wind well into next week.





Attached Images
File Type: png gfs.png (116.7 KB, 4148 views)
File Type: gif ukmo.gif (53.6 KB, 4048 views)
File Type: gif ecm.gif (65.2 KB, 4040 views)

Last edited by Artfu1Dodger; 26-11-2010 at 21:29.
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26-11-2010, 20:25   #4
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That precipitation chart you posted is for an hour ago. The east and south east snow is not till later tonight and into the morning.

In other news, That low feature that was missing from the latest GFS run was quite pronounced on the 6.1 news and weather, What's the reason for this i suppose it's them using different models. which one would that be based on?
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26-11-2010, 20:26   #5
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Whats the chances of any snow making it as far as Laois over the weekend?
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26-11-2010, 20:29   #6
Redsunset
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Originally Posted by bkelly86 View Post
Whats the chances of any snow making it as far as Laois over the weekend?
Tomorrow morning looks best chance
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26-11-2010, 20:32   #7
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From previous thread

Darkman2:
Quote:
Keep an eye on the M2 buoy for those in Dublin. We need the Dew Point out there (30km's east of Howth Head) to be BELOW 1C for snow to be realistic at coastal fringes. (The reason I don't say below zero is because of it's distance from land) Currently it is 1.1C having fallen .6C in the last hour. This will be crucial so Dubs should keep an eye on that.

http://met.ie/latest/buoy.asp

If the DP reaches within .5C of 0 on the buoy snow is a dead cert on immediate coasts.
DP down to 0.1C now.
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26-11-2010, 20:40   #8
 
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Some info from the upstream 12Z Castor Bay, Lerwick, Albermarle and the 12Z and 18Z Valentia soundings.

Castor Bay (Lough Neagh)

T850:
-7.9°C
Thickness 500-1000: 5201m
Thickness 850-1000: 1292m
Steering Winds: Northerly 35-45kts

Lerwick (Shetland Islands)

T850:
-9.1°C
Thickness 500-1000: 5146m
Thickness 850-1000: 1285m
Steering Winds: Easterly 25kts

Albermarle (Northeast England)

T850:
-7.5°C
Thickness 500-1000: 5183m
Thickness 850-1000: 1285dm
Steering Winds: Northerly 20kts

Valentia 12Z
T850:
-4.9°C
Thickness 500-1000: 5244m
Thickness 850-1000: 1300dm
Steering Winds: NNW 30kts

Valentia 18Z
T850:
-6.3°C
Thickness 500-1000: 5244m
Thickness 850-1000: 1302dm
Steering Winds: Northerly 30kts

The Albermarle sounding is the key one for the southeast tomorrow as it is most representative of conditions upwind. It's showing quite a moist profile, but it should lose some of this moisture through precipitation over land. Northeasterly flow will bring this airmass over Wales before coasting out over the Irish Sea. With the short sea track, it may not generate very heavy showers, but with less modification, they have a good chance of being snowy but shortlived.

The Lerwick sounding is representative for the rest of the country tonight, and was slap bang in the middle of that "polar/non-polar low" system today. It's a similar profile to the Albermarle sounding, just slightly colder. There's a lot of high terrain between it and us, but a longer sea track by the Isle of mann when winds turn northeasterly tonight. So it should be generating streamers by the Isle of Mann and they shuold be directed southwestwards towards the east Coast, though I'd expect to see a clear slot in the lee of the Isle of Mann. Unfortunatley our friends in louth and north Meath may be in the wrong place again, like last year, with the northern Ireland landmass getting in the way too. From say east Meath south to Wexford should get the brunt of showery activity. SSTs are 12°C off the east coast, so showers will be beefy and likely thundery, but the big question remains what depth of melt layer there will be.

Latest GFS sounding forecast for Dublin Airport 12Z tomorrow shows around a 1000ft warm layer, with positive surface wet bulb temperature, so hmmm, on the wrong side of marginal for snow, but the showers should make it further inland, so I'd expect snow at the surface there. Things will be improving all the while though, and the snowline will retreat back towards the coast tomorrow evening and night. I'd say most people will see snow, but there will be some unlucky ones who won't.

Similarly for the northwest and west of the Shannon. Maybe by Roscommon, etc the showers from the north will have died out, but west of that shuld see sustained activity from the north Mayo coast. Plenty of places will see snow at all levels, but there will still be some dissapointed people at low levels, I would imagine.

Last edited by Su Campu; 26-11-2010 at 20:45.
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26-11-2010, 20:45   #9
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Originally Posted by Su Campu View Post
Unfortunatley our friends in louth and north Meath may be in the wrong place again, like last year, with the northern Ireland landmass getting in the way too.
Awww crap!! not again...boo urns
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26-11-2010, 20:47   #10
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With humidity so low and no real convection taking place, the M2 buoy is really saying that there's some not very cold but dry air off the east coast. For showers to develop tonight, that air mass will have to change. This is expected to happen later tonight, so the humidity required for shower development will be in place. The wind direction will change to offer a larger sea fetch with resulting shower formation.

The REAL problem with that reading is the air temperature, 5.7 degrees. As the wind direction changes, I want temperature to fall too. Unfortunately, for showers to happen there must be a decent sea fetch too. It will be a tall order to have more ENE winds over a fairly large area of water while also producing a drop in air temperature of about 3 degrees. I would want the air temperature to be below 4 degrees after it starts blowing from the ENE for a serious chance of snow along the costal parts of Dublin, Wicklow and Wexford.

Last edited by lucernarian; 26-11-2010 at 20:56.
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26-11-2010, 20:56   #11
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well if by chance we get anything tonight, be it hail or snow. it stick like **** to a shovel.

its like a ice rink outside after the big thew today.
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26-11-2010, 21:05   #12
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Can anyone explain to me how the Hirlam precipitation graphic has plenty of convection coming in over the East over the weekend:

http://www.dmi.dk/dmi/index/danmark/vejrkort.htm

whereas the new Met Eireann one doesnt seem to have much at all?

http://www.met.ie/forecasts/5day-ireland.asp

Am I missing something here or which is likely...please be Hirlam!
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26-11-2010, 21:12   #13
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[QUOTE=Su Campu; though I'd expect to see a clear slot in the lee of the Isle of Mann. Unfortunatley our friends in louth and north Meath may be in the wrong place again, like last year[/QUOTE]

what i was thinking but couldn't bring myself to say it,i dont think the showers are going to be heavy either(on the east coast),i think from what i can see it's after the weekend(late sunday night/into monday before most of meath see's any worthwhile snow.whats your input su on that?
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26-11-2010, 21:15   #14
 
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Originally Posted by Squeaksoutloud View Post
Can anyone explain to me how the Hirlam precipitation graphic has plenty of convection coming in over the East over the weekend:

http://www.dmi.dk/dmi/index/danmark/vejrkort.htm

whereas the new Met Eireann one doesnt seem to have much at all?

http://www.met.ie/forecasts/5day-ireland.asp

Am I missing something here or which is likely...please be Hirlam!

HIRLAM stands for 'High Resolution Local area Model'. It can pick up on minute features that might spring up more readily than its parent model the ECMWF. Working with a combination of the two is usually the best job.
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26-11-2010, 21:16   #15
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Awww crap!! not again...boo urns
Hey, I live in Meath and we got snow today, North Meath infact

So yay
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