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24-01-2010, 10:49   #1
darkman2
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Turning progressively colder through the week, Very cold with snow showers later

Morning! It looks like things will be turning colder from the North with each day through this week with frost becoming severe later in the week. To start with the Jet Stream profile is getting much more condusive to a Northerly plunge that could end up being a longer duration then is currently modelled by the GFS.




Everything North, South.

The result is actually quite a potent, allbeit, brief incursion of very cold weather










GFS goes on to sink the Northerly by the end of the weekend but still very cold for Sunday and milder Westerlies follow on.



ECM has a similar outlook.




UKMO is the coldest of them all with something probrably a bit more sustained.



That is next weekend though so plenty of time for things to change. In the mean time turning colder this week with a strenghtening Northerly wind. Frosts becoming severe again at night.





Tuesday night typical of the temperatures to expect during the week at night.


Fog should not be as much of an issue generally next week. It should be mostly dry though to Thursday at least. Then those snow showers at the weekend with the North, West and East all at risk.

It's a developing situation for the end of the week. Frost, Ice, and Snow returning. The only question is for how long?

More later...

Last edited by darkman2; 24-01-2010 at 10:58.
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24-01-2010, 14:07   #2
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Something to prepare for.

I noticed on the Met Eireann charts on the farming forecast for the week it is starting like the previous cold period - the high pressure will move to the west of us, low to the east or north east - a northerly flow and the high possibly heading towards Greenland with a ? mark there, have to wait and see.

Definitely does look a return to the cold...can't say I'm looking forward to it. Still have a tiny bit of snow leftover from a drift here...its waiting for more....
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24-01-2010, 14:34   #3
darkman2
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Something to prepare for.

I noticed on the Met Eireann charts on the farming forecast for the week it is starting like the previous cold period - the high pressure will move to the west of us, low to the east or north east - a northerly flow and the high possibly heading towards Greenland with a ? mark there, have to wait and see.

Definitely does look a return to the cold...can't say I'm looking forward to it. Still have a tiny bit of snow leftover from a drift here...its waiting for more....

The North Atlantic Oscillation is positive so that is mitigating against a proper retrogression of high pressure into Greenland.

The Polar Vortex, the excitable atmospheric conditions depicted by the deep blue and purples on the charts above, for a long cold period like we had earlier this season would have to go into Scandinavia and stay there and preferably move south then.

There is little sign yet of a big pressure rise over Greenland but we have seen this forcast change in the past much closer to the time. For the moment it looks like the much colder weather will be temporary 48hr thing. However that can change. And given recent events there is not much reason to believe it won't change. My own feeling is that the cold will last longer then currently forcast and will get deeper during the coming weekend. At least lasting into the early days of next week. That's just my own interpretation. It could pan out exactly as forcast but that's unlikely.


Keep an eye on the NAO forcast. It is still positive or neutral but is forcast to go more negative in the next few days which could have interesting consequences in the next few forcast model runs.




The Artic Oscillation menwhile continues it's slide into deeper negativity




These signs look ominously familiar. The risk of a prolonged colder period is increasing. But we are not there just yet.

Last edited by darkman2; 24-01-2010 at 14:49.
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24-01-2010, 15:18   #4
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Mmmnnnn...interesting!
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24-01-2010, 15:19   #5
 
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SUNDAY NOON LONDON TIME
Winter spreads back west


If one looks at the London-Berlin example I was using as a contributor to the global temp challenge of Jan 1-10, we find the idea of a return to normalcy posted here a couple of weeks ago was right. The first 15 days of the month ran 7.5 below normal, by far the most widespread cold in populated areas of northern Europe for this harsh part of winter since the 80s. The last 8 days have seen Berlin stay in the cold, and this is what I had said, the further east you went the more the cold would hold... they have been -6.5 SEVERE COLD is taking hold over Germany. However London is 1.6 above normal since Jan 16.

The cold is getting ready to expand west again!

So folks in the battle of Britain and France that at least has allowed winter to let up a bit here ( mind you the "thaw" is to around normal and part of the winter forecast... that cold centered over the east and maritime air masses would do battle) is going to come to a crashing end later this week. And while when its all said and done the CORE OF COLD WILL BE WHERE IT WAS IN 02-03 its simply that this winter is even colder than that one for the areas targeted.

Now you want to see a real thaw... and by the way winter is returning to the states also, look at the Us contributors to this: Chicago and NYC the first 15 days of the month...-3.9. Since then: PLUS 8.4 So they got a major break but winter is about to close in on them also.

So make sure the winter woolies are ready anew... its coming later this week

ciao for now

joe b
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24-01-2010, 15:44   #6
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Potential Cold Incursion

Quote:
Originally Posted by darkman2 View Post
The North Atlantic Oscillation is positive so that is mitigating against a proper retrogression of high pressure into Greenland.

The Polar Vortex, the excitable atmospheric conditions depicted by the deep blue and purples on the charts above, for a long cold period like we had earlier this season would have to go into Scandinavia and stay there and preferably move south then.

There is little sign yet of a big pressure rise over Greenland but we have seen this forcast change in the past much closer to the time. For the moment it looks like the much colder weather will be temporary 48hr thing. However that can change. And given recent events there is not much reason to believe it won't change. My own feeling is that the cold will last longer then currently forcast and will get deeper during the coming weekend. At least lasting into the early days of next week. That's just my own interpretation. It could pan out exactly as forcast but that's unlikely.


Keep an eye on the NAO forcast. It is still positive or neutral but is forcast to go more negative in the next few days which could have interesting consequences in the next few forcast model runs.
Interesting update Darkman 2.

A couple of points also if I may. Firstly, the NAO is actually currently in a weakly negative phase, as indicated by the charts you have posted above. This was confirmed by NOAA in their Extended Forecast Discussion yesterday. However, it is only weakly negative it has to be said, at least at the moment.

I would tend to agree with your own feeling on the longevity of any cold incursion. Or at least, maybe it is a case that a slight interlude may be reached only for blocking to return again. Each NWP Operational evolution is subsequently building stronger pressure over Greenland for the timeframe on the previous run - a clear example of this being the overnight UKMO Evolution.

Apart from the NAO & AO Signal, by far the most interesting at the moment is that of the 30mb Temperature Profile. Latest observations indicate that immediate downwelling, or penetration to the troposhere, of the warming event, is taking place. The general signature of such warming at the tropospheric level is for largescale blocking to develop.

Overnight multi-model guidance is certainly in favour of a rather potent variable Northerly flow during the second half of the coming week. Again, there is much emphasis upon a semi-retrogressive block with at least some real height rises over Greenland, associated with this HP Block centred in the High Northwest Atlantic. Forcing, generated by the segment of the Polar Vortex dropping into Scandinavia will aid in the Westward progression of this block.. Longer term signals are very mixed, with no clear pattern emerging. It is quite possible that we will remain in a Polar Maritime airflow, after a Polar flow later in the coming week. There is even no general trend beyond Day 7 at the moment, however most Guidance overnight models a gradual collapse of this Block, by the end of the week.

If the overnight 00Z Guidance from ECMWF & UKMO were to verify, then we would be looking at rather widespread and relatively severe frosts during the second half of the coming week, with the threat of sleet & snow showers mainly across Northern districts and in coastal areas, but also into Eastern areas if the general evolution were to occur as modelled on the overnight UKMO 00Z Evolution. A certain amount of cold troughing is likely across the continent in the latter part of the week, with deep cold air in place.

A cold incursion does look increasingly likely during the second half of the week, but is by no means a certainty at this time.

The 30mb Temperature is now quite some way above average, still rising almost vertically, at about an angle of 87 Degrees overall. If we are to see another 5 - 7 degress of warming, we could be very optimisitc for at least some influences at the tropospheric level later into February.



SA
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24-01-2010, 17:59   #7
 
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Yes, all very interesting indeed. It looks like the Arctic outbreak currently down the Davis Strait and Labrador Sea will deepen the west atlantic trof, forming a cut-off low southweswards of the Azores, allowing the retrogression of the European high to mid Atlantic, a setup very similar to the early January situation. But it looks with the polar vortex never showing proper splitting, there could be enough energy coming from northern Canada next weekend to shove the High southwards, as the global pattern takes on a more progressive 7-wave pattern.

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24-01-2010, 20:30   #8
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Will we be getting as cold temperatures as we had ??
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24-01-2010, 20:33   #9
 
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It has gotten noticeably colder today and yesterday, maybe this is Part II of the 'Big Freeze', hopefully!!!
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24-01-2010, 22:32   #10
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Will we be getting as cold temperatures as we had ??
no. - 5 or -6 at most, by night, i'd say. the cold won't last too long either - three-four days at most.
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24-01-2010, 22:39   #11
 
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The Eagle said the northerly would be dry, apart from a few wintry showers for the north and west. He mentioned frost as being the main event by the end of the week.

The exact details of the week ahead are likely to change back and forth a bit, but certainly January looks like ending the coldest month relative to averages for a helluva long time!

Last edited by Su Campu; 24-01-2010 at 22:41.
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24-01-2010, 23:24   #12
 
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I don't see too much to get depressed/excited about. Not enough to close the schools anyway!
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24-01-2010, 23:26   #13
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A bit of cold weather and the masses will come flocking back to the weather forum

I am only managed to get signed in again myself this evening after the outage !
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24-01-2010, 23:27   #14
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so no chance of an active trough or polar low crossing down over us then

just to see a bit of snow falling at this stage would be enough to get me excited

Last edited by nacho libre; 24-01-2010 at 23:29.
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24-01-2010, 23:33   #15
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A small snow flurry on the east can cause an avalanche on the forum.
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