Model Output Discussions 12z 08/03/17

[skifreak]

I wouldn't discount the cold Northerly option, it's been showing up quite a bit in various operational runs, there's been at least some members going for it in every GFS ensemble set I've looked at over recent days. The winters that panned out as similar to this in terms of snow in the Scottish Ski Areas were 2012 and 1998, in both cases the best conditions of the season came in late April onwards into May in the Northern Cairngorms. I'd say it's almost the form horse here, if it goes the other way and we do get a high pressure dominated April into May, I'll certainly be hoping it pans out like 2003 and not 2007 thereafter!

Just to illustrate the point, some photos looking down / up Coire Cas on CairnGorm in mid March, then mid May 2012:

Edited April 1, 2017 by skifreak

[Frosty.]

Tonight's Ecm 12z ensemble mean is showing a fine pleasantly warm anticyclonic spell developing next week, especially for southern uk but by the end of next week the high is pushed away further south with lowering heights to the NE and height rises to the W / NW with a much colder (arctic) unsettled spell on the way..as did the earlier 12z op.

Edited April 1, 2017 by Frosty.

[knocker]

Before a quick overview of this morning's GFS it's worth noting one thing within the ten days and that is the difference between the 18z and 00z runs starting around T126 even though they both end up with an upper trough in the vicinity of the UK. Quite stark.

Anyway still looking at the passage of the decaying fronts Monday into Tuesday so cloudy with some patchy rain in in west and north west before the HP reasserts itself, albeit quite windy in the north as the trough tracks into Scandinavia. The high centre establishes itself to the SW/S of the UK until around 00z Saturday when the next burst of energy from the north west makes inroads as a trough tracks east north of Scotland. Simultaneously a weak trough deconstructs in mid Atlantic and the high cell weakens and begins the move south east. All this means that most areas will be under the auspices of high pressure for the week, so a period of quiet pleasant weather with the usual geographic and diurnal caveats vis cloud and temperature.

From this point we have another surge of the Azores in mid Atlantic, impaired somewhat by the cut off upper that resulted from the deconstruction, so that by Tuesday midnight we find a major trough area the the NE and high pressure to the south west with the UK in quite a strong NW, showery flow. Given the run to run variations during this period extreme caution should be attached to any detail and just to note the indicated more unsettled period is on the cards.

It should also be noted that this mornings GEFS anomaly supports the scenario of height rises in mid Atlantic with a trought to the N/NE and thus a cooler NW upper flow.

Edited April 2, 2017 by knocker

[NO LONGER POSTING]

The current colder spell being modelled needs to be removed quickly. Now is not the time for cold and it would be super destructive! I have blossom all over my apple and less trees seedlings going and loads of other plants! 

[knocker]

At the moment I don't think it's justified to go overboard on the 'cold' potential. Certainly looking cooler with temps dipping below average a tad but hopefully that's all

[Frosty.]

50 minutes ago, Surrey said:

The current colder spell being modelled needs to be removed quickly. Now is not the time for cold and it would be super destructive! I have blossom all over my apple and less trees seedlings going and loads of other plants! 

I don't see any problems for the south, or even the north judging by the Ecm 00z.

[knocker]

The evolution of the ecm is not dissimilar to the GFS up to the weekend where 00z on Sunday it has a pronounced trough disruption mid Atlantic with the high pressure just about hanging in there. From this position the trough from the northern part of the disruption (the perennial cut off low moving south) tracks east to be over the UK by 00z Tuesday. Thus the indicated and idea of more unsettled and cooler weather by the beginning of next week is gaining traction.

[Frosty.]

1 hour ago, Surrey said:

The current colder spell being modelled needs to be removed quickly. Now is not the time for cold and it would be super destructive! I have blossom all over my apple and less trees seedlings going and loads of other plants! 

However, I do see a problem if the Gfs 00z is right

Edited April 2, 2017 by Frosty.

[Polar Maritime]

A chilly outlook into Wk2 from this mornings GFS with a Northerly type flow/blast over the UK bringing widespread -10 uppers as far South as the Midlands, Certainly not unusual for the time of year.

Edited April 2, 2017 by Polar Maritime

[Summer Sun]

Bar some patchy rain in the north and west next weekend looks mainly dry according to UKMO/extended

[Frosty.]

Although the Gfs looks severe, it's chances of verifying are extremely slim to zero..in the meantime, enjoy the high pressure during the coming week or so. It still looks like becoming a bit more unsettled and a little cooler, at least for a time during week 2.

Edited April 2, 2017 by Frosty.

[johnholmes]

Forget the anomaly charts for any guide to 6-10 day upper air. Last evening NOAA did a complete back track on what I had posted yesterday, GFS this morning is still going for that type. It is unusual for NOAA to do such a change within 24 hours. During the change over seasons winter to summer and summer to winter there is quite often a spell when these charts are rather variable. Maybe this is why NOAA has done such a change.

just for info the links below

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

On balance I would suggest a coolish possibly rather unsettled spell in the 6-14 day period based on what I have seen on a variety of charts over the past week.

[Frosty.]

The GEFS 00z mean shows high pressure becoming the dominant feature during the week ahead with plenty of pleasantly warm sunshine and chilly nights where skies clear, just a mini blip on tuesday as rain clears southeastwards, wed / sat are looking good..but then becoming cooler and more unsettled during week 2.

Edited April 2, 2017 by Frosty.

[Captain Shortwave]

Well this week coming looks dry but I must admit the position of the high doesn't look overly conductive to deliver warm and bright conditions after a front moves eastwards late on Monday and into Tuesday. The high centred just to our west tend to pull mild air in over the top with the largest sea track humanly possible. There is a chance of something brighter and warm next weekend though before a trough becomes well established towards Scandinavia.

       

The high briefly moves east enough to bring a more southerly component (In the south at least). It then declines with heights lowering and temperatures falling towards or even below average. A northerly blast with wintry potential cannot be ruled out in the week up to Easter.

Spring has a habit of delivering a wide variety of weather types ranging from bitter cold to very warm with not a lot of time between the two, this could happen in the next couple of weeks after we saw some exceptional warmth last week. It is what makes Spring my favourite season.

[knocker]

The eps this morning continues with the theme of strong height rises mid Atlantic with the trough in the east and thus a brisk NW/NNW upper flow that would portend some unsettled cooler weather for a few days. I say a few days because as we move into the 10-15 period the amplification begins to relax and the pattern shift east thus the Azores may reassert some influence towards Easter, more so in the south although temps still not any great shakes.

[Cloud 10]

Probably more suited to the other thread but some big changes in the stratosphere over the next week or so as the final warming gets underway,with the polar vortex going into meltdown mode,which could explain some of the volatility in the anomaly charts John mentioned.

 

AO likely to go negative,so arctic air being pushed to lower latitudes.

 

 

[Frosty.]

3 hours ago, Cloud 10 said:

Probably more suited to the other thread but some big changes in the stratosphere over the next week or so as the final warming gets underway,with the polar vortex going into meltdown mode,which could explain some of the volatility in the anomaly charts John mentioned.

 

AO likely to go negative,so arctic air being pushed to lower latitudes.

 

 

I noticed Steve murr lurking earlier..I wonder if it could turn colder in week 2..we shall see.

Edited April 2, 2017 by Frosty.

[snowray]

58 minutes ago, Frosty. said:

I noticed Steve murr lurking earlier..I wonder if it could turn a little cooler in week 2..we shall see.

Well thats it then, I was thinking to myself just that, is Mr Murr starting to take an interest? bad omen if your a mildy and expecting another very mild month that.

 

Ensembles for London and Leeds, pretty well good agreement for a settled week coming up with close to average early April temps, turning a bit milder for a while then a lot colder from around the 10th. Some juicy charts for coldies in there, if only it was a few months ago.

[Frosty.]

Well there is a mention of wintry showers and occasionally colder weather in the extended outlook that wasn't mentioned before so after the settled anticyclonic spell a colder unsettled phase from the NW is a more realistic prospect than previously but it doesn't sound bad at all for the SE generally speaking, the most active weather is set to affect Northwestern uk the most.. but mostly after the week ahead.

Edited April 2, 2017 by Frosty.

[snowray]

25 minutes ago, Frosty. said:

Well there is a mention of wintry showers and occasionally colder weather in the extended outlook that wasn't mentioned before so after the settled anticyclonic spell a colder unsettled phase from the NW is a more realistic prospect than previously but it doesn't sound bad at all for the SE generally speaking, the most active weather is set to affect Northwestern uk the most.. but mostly after the week ahead.

Yes but it will feel a lot colder everywhere, I mean we have been used to temps of 15-22c recently so even high single digits and cold nights would be quite a shock. Probably just a temporary blip of course, and I don't suppose that anyone is expecting anything severe away from possibly Northern hills/mountains, but Welsh hills and places like Dartmoor could certainly still get snow on a cold and unstable north/northwesterly regime. 

Edited April 2, 2017 by snowray

[Cheshire Freeze]

Just a note- the ECM is just as severe as GFS has been showing. It doesn't matter as it's shown at day 10 but pressure is rising up towards Greenland. Day 11 would show us at the mercy of Scandi troughing and N Atlantic/Greenland heights. 

If we're to get a N'ly I just hope we get as clean a one as possible so that we get to see some great convective cloudscapes like at the end of April last year.

[Frosty.]

10 minutes ago, snowray said:

Yes but it will feel a lot colder everywhere, I mean we have been used to temps of 15-22c recently so even high single digits and cold nights would be quite a shock. Probably just a temporary blip of course, and I don't suppose that anyone is expecting anything severe away from possibly Northern hills/mountains, but Welsh hills and places like Dartmoor could certainly still get snow on a cold and unstable north/northwesterly regime. 

Agreed, I've been enjoying the warm weather so much I don't really want it to change but accept its looking likely by week 2.

[snowray]

26 minutes ago, Frosty. said:

Agreed, I've been enjoying the warm weather so much I don't really want it to change but accept its looking likely by week 2.

We can't complain though, its been lovely in March and at least another week of decent weather is on the cards with it should turning pleasantly mild again later next week.

But we should not be surprised to see at least one last cold spell in April.

[Summer Sun]

A quiet week ahead by the weekend the high moves into mainland Europe setting up a southwesterly flow for us on Saturday some rain for the far north and west by this stage but dry for many

[Frosty.]

The Gem 12z is looking good for most of the week ahead, especially between wednesday and saturday when the best of the weather would be..becoming more unsettled by week 2.

Edited April 2, 2017 by Frosty.