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26-02-2010, 22:49   #1
darkman2
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Remaining very cold - Bitterly cold Easterly winds later - Snow at times

A thread for the next 7 days. Remaining rain and sleet will die out in the North on Saturday to leave a cloudy but mostly dry day there with a thaw setting in. Cloud is likely to remain in those areas but sunnier skies elsewhere. For the next 7 days in general it will remain cold and very cold at night with frost and Ice. But it will be becoming drier up to midweek next week when a little rain or snow is expected. Daytime temperatures typically around 3 - 6C, a little higher on South coasts and winds variable but mostly light so not feeling too bad. Later an Easterly will develope as an area of High Pressure builds to the North around day 5 or 6 and it is likely to get exceptionally cold once again though the longevity and severity of this particular spell won't be determined for a couple of days suffice to say Eastern and Southern areas most at rsk of significant snowfall. Also in transition to the Easterly a more significant spell of snow may occur next week preceded by rain but this is uncertain at this stage. So remaining very cold and wintry for the forseeable future.

Last edited by darkman2; 28-02-2010 at 00:17.
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27-02-2010, 00:44   #2
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cheers DM2,easterlys would make things interesting again,anyting but the boring s**t at mo,if it were the summer would we want the easterlys as well? i presume that would drag warm air to us
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27-02-2010, 04:36   #3
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Im sorry but i can't resist posting this,because its holding a trend,long may it last.MASSIVE HEALTH WARNING as its fantasy island but got to keep the prospects going.






That high pressure forecast next week could bring savage cold dry air and just maybe we'll have a low to our south banging into it,and hey presto snowstorm.
All sounds very wonderful in my La La land head but you never know.
Winters far from over.
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27-02-2010, 05:57   #4
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That chart just means another non snow event, just like last night!

Another mild morning here, 3.2c.
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27-02-2010, 05:59   #5
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Quote:
Originally Posted by redsunset View Post
Im sorry but i can't resist posting this,because its holding a trend,long may it last.MASSIVE HEALTH WARNING as its fantasy island but got to keep the prospects going.






That high pressure forecast next week could bring savage cold dry air and just maybe we'll have a low to our south banging into it,and hey presto snowstorm.
All sounds very wonderful in my La La land head but you never know.
Winters far from over.
I think I just wet myself. That's weather porn right there.
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27-02-2010, 09:24   #6
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every where in ireland except cork yet again is gonna get snow? not fair
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27-02-2010, 09:51   #7
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Renewed Wintry Phase?

The latest available overnight Guidance sees a continuation in a trend towards the development of an Easterly flow. Notably, present indications would suggest that the main area of High Pressure will build quite a distance further north than was the case with the Easterly flow earlier in February. Of course this is subject to change, however that's what the latest indications suggest.

The latest 6/10 & 10/14 Day CPC 500mb Height anomoly charts indicate the pattern quite well, with a mean variable Easterly flow, generally varying between Northeast & East. Suggestions have been there for more than 5 days now of a transition to this pattern, but exact details will be uncertain for some time yet.

http://www.cpc.noaa.gov/products/pre.../814day.03.gif

As DM2 has mentioned, there is a threat of wintry precipitation towards midweek or slightly later as a residual disturbance/energy in the flow backs Southeastwards, as HP builds to the North. This risk is primarily indicated on the overnight UKMO Guidance:



The latest 00Z GEFS Mean Guidance has a mean Easterly flow developing at T+120:



ECMWF remains relatively constant on the pattern indicated last night, with much colder conditions spreading across the country from the Northeast towards T+120 (Day 5). Notably, there has been a shift on the last two ECMWF evolutions away from a dry stable Easterly flow to a more unstable Easterly/Northeasterly flow, with an intensification of the cold.

The latest ECMWF Ensembles for De Bilt, which are important in an Easterly flow, show a significant cooling of conditions across the near continent. Indeed, indications suggest exceptional anomalous cold for the first 10 Days of March - considering increasing solar influences etc. There is also an increasing signal for precipitation (sleet & snowfall) in that region as the flow back Northeasterly, trending Easterly.

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html

GEM & GME also indicate a relatively potent & prolonged Easterly flow on the 00Z Guidance.

Summary

In summary then, a pattern change is occuring as we head into March. There is an increasing signal for high pressure to develop North of the UK & Ireland in the coming 5 days approximately. While it may become somewhat less cold during the transition phase, present indications suggest mean troughing over Iberia & secondary cold troughing over the near continent. As a result, indications suggest a renewed cold phase is possible as we head into March, which would be quite remarkable indeed. We are some distance away yet from being certain, but the latest trends do favour a well below average & and quite possibly wintry pattern as we head into the first third of March.

However, with any Easterly flow, cross model continuity is needed at T+96 in order to have high confidence in the outcome.

SA
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27-02-2010, 10:13   #8
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SA, just want to thank you for your easy to read, balanced posts (and easy to understand for a noob !!)

I have leared a lot from them, keep em coming !
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27-02-2010, 11:27   #9
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On the top of kippure currently snowing lightly not much wind
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27-02-2010, 13:39   #10
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I must go up kippure soon for a bit of snowboarding. Hopefully the snow is holding up well up there? And maybe getting a good top up next thursday!
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27-02-2010, 14:53   #11
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BANK!!!!!!

Come on charts for once do what your told and give us a last hurrah to finally put to bed if this winter has been a classic or not.
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27-02-2010, 16:09   #12
 
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Spanish HIRLAM 850's charts show how this Atlantic ridge is forecast to ridge rapidly towards Ireland preventing any significant mildness from moving in our direction:

2/03/2010 7am:




2/03/2010 1pm:




2/03/2010 7pm:



It is crucial that this ridge remains as strong as is forecast for us to be in with a chance of another blast from the north or east. There is every chance that it may just collapse as well before it has a chance ridge in the right places.

Worth keeping an eye on either way.
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27-02-2010, 16:34   #13
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I agree Deep Easterly & I also think another crucial aspect to the evolution will be the residual trough development, as that, almost exclusively will determine as to whether any flow would be cold but dry or cold and wintry.

For example, the GFS 12Z Evolution moves this residual energy further north and it then fills, therefore even though 850mb temperatures of -11 spread across the country from the East/Northeast, the time period for snowfall potential is greatly reduced compared with the 06Z evolution because mean troughing is much further to the south.

It is paramount that we see the troughing as close to the south of the UK in particular as is possible, to support and undercut and Easterly flow.

In that regard, UKMO 12Z Operational is quite impressive at both T+120 & T+144 and follows the main evolution, similar to that of the 00Z ECMWF Operational, with a Northward, then Southward progression of the main area of residual energy. With pressure around 1000mb, then there would ample opporunity for wintry developments in a very strong Easterly/Northeasterly airflow.

It's a fine balance, between having the centre of the HP far north enough but not too far, the main area of HP being elongated but not too elongated, along with mean troughing close enough from the South to support and undercut the high, but not too close that it would lead to a mixing of the airflow.



Not asking for much is it

SA
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27-02-2010, 19:02   #14
 
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Some of this stuff being progged now is quite the snowfest for lots of places not exclusively the East but especially there.
There seems to be increasing cross model agreement.

I'm warey of that...these days,they can become fickle just like that.


It's a pity,it didn't happen a few weeks ago but at any rate some of those synoptics have the potential to give us a lot of snow cover and freezing temps.
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27-02-2010, 19:41   #15
 
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ECMWF still keen on building the Atlantic ridge northwards at 120hrs:



An encouraging trend, but we are getting into the territory where sudden shortwaves may appear in later runs which may dampen the effects of this potential build to the north, but so far, so good.

Such a set up would not really benefit the west regarding snow, unless there are active troughs contained within the flow, but with a good, stiff breeze, at least it will have super drying effects. Despite very little rain here over the last few months, everything is still quite damp, so this sort of set up will be welcome by me at least.
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Last edited by Deep Easterly; 27-02-2010 at 19:43.
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