Winter Model Discussion 18Z 16/1/13 onwards.

[Jason M]

Yes Jason lot's of uncertainty in the models, What JH was alluding to regarding the 500mb charts this morning seems very reasonable. I dont

think there will be any quick breakdown in the near future of this cold set-up, lot's more battleground snowfalls and severe frost's over the next week and let's face it the cold has only just got here.. Great model watching over the next few days.

And to be fair, a fair number of the ensembles in a weeks time are there or thereabouts with what JH was showing. I'm coming round to the view now that we won't see a breakdown next weekend.

Jason

[Frosty.]

Looks like a breakdown towards the end of next week not even sure if it will be a snowy breakdown either as temps in the south will probably on the wrong side of marginal. No signs what so ever of the Greenland HP coming into play this winter (so far).

you must have missed the gfs 00z then, it showed a powerful greenland high developing in FI and ridging well south into the atlantic, and any real change to the current pattern is still in FI so the cold spell could extend further and then be reinforced from the northeast or north. The latest gfs shows the cold block putting up a good fight against the might of the atlantic by the end of next week, any mild/less cold could be very brief indeed.

[UV-RAY]

Any breakdown would only be to slightly less cold temps away from the SW and coastal extremities, than now,.The outlook remains uncertain IMO.

[atrow]

whats peoples thought on the 12z upgrading, shifting east or west for sundays snow??

[Panayiotis]

whats peoples thought on the 12z upgrading, shifting east or west for sundays snow??

I would say a shift to the west, as the 06z always has everything further east on its run, seen it do that on all the 06z runs this week!

[Froze were the Days]

you must have missed the gfs 00z then, it showed a powerful greenland high developing in FI and ridging well south into the atlantic, and any real change to the current pattern is still in FI so the cold spell could extend further and then be reinforced from the northeast or north. The latest gfs shows the cold block putting up a good fight against the might of the atlantic by the end of next week, any mild/less cold could be very brief indeed.

Yeah I did miss the 0z run, occasionally the GFS does flit (over the last week or so) with a different FI but then goes back to it's default unsettled pattern but as of yet we have not experienced any conditions that have come about due to excessive heights in the Greenland region. I do see a break down to less cold conditions if not milder and then the outlook beyond that is very uncertain, didn't the MetO put out an outlook a few days ago saying they believed that Greenland HP would become very evident into February?

Edited January 19, 2013 by Froze were the Days

[snowking]

A lot of regions around the country are reporting rain, sleet, melting and marginality i think this is because there has never really been any sustained heights over iceland/greenland to completely block off the atlantic unlike 09/10 10/11 where we all know there were!! The atlantic is always trying to fight back when it isnt blocked off and it will be all next week as well, im not complaining about this cold spell and this winter is already better than last one because of it but i think through the rest of jan and feb we should be looking north west for our blocking

I think quite a few of those reports are because either observation station (or human error) are interpreting snizzle as light rain/sleet (as a lot of people tend to).

We have had the exact same thing all morning here so far but when you take a sweep around the country, dew points are widely sub zero, temperatures not really above 2c, and upper values as indicated:

Other than on the extreme coastal fringes with sea modification, its likely to be light snizzle.

Its also worth being careful when differentiating between sustained blocking and strong HEIGHTS.

Here is the situation from the 9th Jan:

And here we are today:

Strong heights? No (but thats not always required) but SUSTAINED blocking to our NE, well I guess it depends how you quantify sustained, but even in 4 days time:

Its still forecast to be there (incidentally, the reason I use +96 here is because thats about as far as i'm willing to trust the current output).

So thats 9th-23rd Jan - 2 weeks of blocking to our N/NE. Not on the scale of a 47/63 perhaps (yet...) but I would certainly describe that as sustained.

As for the need to look to our NW next, I would fully agree with that sentiment - as would current stratospheric signals (so long as we can get a complete movement east of the canadian vortex segment)

Kind Regards

SK

[Joker]

you must have missed the gfs 00z then, it showed a powerful greenland high developing in FI and ridging well south into the atlantic, and any real change to the current pattern is still in FI so the cold spell could extend further and then be reinforced from the northeast or north. The latest gfs shows the cold block putting up a good fight against the might of the atlantic by the end of next week, any mild/less cold could be very brief indeed.

The Greenland HIGH is likely to be the key to any possible Atlantic incursion. It's going to considerably dampen the energy of the jet and although temperatures may rise into the low single digits across the southern half of Britain, it will be short and sweet with cold uppers returning quite quickly. By next weekend I don't think we will be calling it a 'warm up' at all by any standards - just a little less cold!

[Frosty.]

didn't the MetO put out an outlook a few days ago saying they believed that Greenland HP would become very evident into February?

They don't usually say that in their daily updates but if they did, bring it on...the atlantic has tried and failed to displace our cold block but it will keep searching for a weakness and a battle is likely towards the end of next week, like I said before, the atlantic profile won't need much change for the uk to remain cold and blocked.

[atrow]

I would say a shift to the west, as the 06z always has everything further east on its run, seen it do that on all the 06z runs this week!

I looked at the gfs and it looked like heavy snow for me but the forecasts seen to be playing it down ?/

[Froze were the Days]

They don't usually say that in their daily updates but if they did, bring it on...the atlantic has tried and failed to displace our cold block but it will keep searching for a weakness and a battle is likely towards the end of next week, like I said before, the atlantic profile won't need much change for the uk to remain cold and blocked.

It might have been the EC32 outlook - Matt Hugo mentioned it.

[Panayiotis]

I dont get this from the NAE, it shows snow for almost everywhere at this time (which is +6hrs, on the 06z) but radar shows nothing, can anyone explain?

http://www.netweathe...ion=radar;sess=

[TheHumph]

It might have been the EC32 outlook - Matt Hugo mentioned it.

I read that somewhere too FwtD but I can't remember who said it. It was definately some Organisation like the Met Office.

[bradymk]

I dont get this from the NAE, it shows snow for almost everywhere at this time (which is +6hrs, on the 06z) but radar shows nothing, can anyone explain?

http://www.netweathe...ion=radar;sess=

i use the rain/snowfall charts with the precipitations chart which are more detailed to where any precipitation is because the precip charts for the same time, do not show the same as the rainfall/snowfall charts. But using both together is more useful Edited January 19, 2013 by bradythemole

[coxxy22]

I dont get this from the NAE, it shows snow for almost everywhere at this time (which is +6hrs, on the 06z) but radar shows nothing, can anyone explain?

http://www.netweathe...ion=radar;sess=

it just shows what would fall in certain areas, so like brady says if you look at the precip charts for the same time then you can work out what will be falling where ! any precip within the pink area would more than likley fall as snow

[snowmackem]

I dont get this from the NAE, it shows snow for almost everywhere at this time (which is +6hrs, on the 06z) but radar shows nothing, can anyone explain?

http://www.netweathe...ion=radar;sess=

Yeah, don't believe everything you read

[chionomaniac]

I dont get this from the NAE, it shows snow for almost everywhere at this time (which is +6hrs, on the 06z) but radar shows nothing, can anyone explain?

http://www.netweathe...ion=radar;sess=

It's not too far off - that chart is suggesting that most places will see snizzle in a six hour period and if you look at the six hour accumulation charts on NW most areas have had that. I think that the NAE is quite accurate with that. Don't confuse the 6 hour NAE chart with the actual radar at any one time.

Edited January 19, 2013 by chionomaniac

[EGHH]

I dont get this from the NAE, it shows snow for almost everywhere at this time (which is +6hrs, on the 06z) but radar shows nothing, can anyone explain?

http://www.netweathe...ion=radar;sess=

It's the precipitation over a 6 hour period. It's showing the potential for some week convective showers I think. Basically a few flakes in the wind from 6am till noon.

[johnholmes]

answer Mike Meehan that I've lost as my pc played up re upper air features

hope this helps Mike

A quick one Mike as in a hurry packing etc?

Long waves are the main troughs-ridges you see on the 500mb charts I use, sometimes referred to as Rossby waves.

short waves are those that develop often around the base of one of these main troughs. Sometimes they will develop sufficiently to become the main trough themselves, often they disrupt the major pattern for a time before disappearing again.

Froze were the Days, on 19 January 2013 - 11:51 , said:

didn't the MetO put out an outlook a few days ago saying they believed that Greenland HP would become very evident into February?

that would not be the Met Office

Edited January 19, 2013 by johnholmes

[stratty]

It's not too far off - that chart is suggesting that most places will see snizzle in a six hour period and if you look at the six hour accumulation charts on NW most areas have had that. I think that the NAE is quite accurate with that. Don't confuse the 6 hour NAE chart with the actual radar at any one time.

....just to add to that we have had very light flurries on and off all morning, which is how i interpretate that chart. It doesn't mean a blanket of snow but more like Head and Shoulders stuff!

[Naturist-Holiday.com]

I dont get this from the NAE, it shows snow for almost everywhere at this time (which is +6hrs, on the 06z) but radar shows nothing, can anyone explain?

http://www.netweathe...ion=radar;sess=

The light shades are generally cloud cover. It's the following darker shade (Blue - rain/Pink - snow) that would likely cause light rain/light snow. Ignore the really light shade unless you are a fan of 8/8 cloudcover observing .

NH

[Wilxy]

its snizzling here now so i think NAE has it spot on.

And it got yesterdays event spot on very pleased with it, and suggests that its the SE turn next along with Northern and eastern england.

[Robbie Garrett]

They probably would have mentioned high pressure to the north or northwest. But not high pressure specifically over Greenland.

I read that somewhere too FwtD but I can't remember who said it. It was definately some Organisation like the Met Office.

[Frosty.]

Latest metoffice update very similar to yesterday with a very cold week ahead, the first half of the week still looks unsettled with sleet and snow at times and severe frosts, the second half becoming more settled and remaining very cold with hard frosts and freezing fog, towards the end of next week into next weekend, turning unsettled in the west with rain,sleet and snow, drier and cold for central and eastern areas, then more generally unsettled and less cold by early the following week with spells of snow pushing east, the less cold phase could be very brief before much colder weather spreads down across the uk again with a return to the type of conditons we have now. When reading this update, the gfs 06z run came to mind although a slower version with cold returning from the north after a brief atlantic/cold block struggle, I really can't see a full blown breakdown with a prolonged return to mild mush, probably more likely to be very cold, then becoming rather cold and then very cold again.

[Paul T]

For me the 06Z indicates the big potential for this cold spell to roll on and on.

The current set up for next week gives a continuous flow that continually undercuts us in the UK. The low pressure systems that the GFS had previously forecast as strolling across the UK next Wed/Thurs are now being programmed with much more potential for undercutting.

In my view what we are seeing is a flow would usually be a W/SW'rly zonal type flow, but the SSW and Northern blocking are combining nicely now and 'saving' us from this boredom.

7/8 days ago the GFS did at many times show milder Westerly’s for the UK today, however we are currently under an Easterly influence with snow lying across the UK.

Undercut central:

Undercut tomorrow:

undercut on Tuesday:

Undercut on Wednesday:

Increasing undercut potential next Friday:

More undercut potential next Saturday?:

The snow potential from these charts is really strong. Not least mentioning that during tomorrow, Monday and Tuesday there are pretty chunky snow events happening at different areas of the UK.

Good times.

Edited January 19, 2013 by Paul T