Model output discussion 8th Feb - Cold for now, but then what?

[winterof79]

Ensembles not without interest today trending colder than average with some increasing cold clusters occurring too

Always interested in this data as a precursor to colder weather

If it is March when we see our coldest period of weather of the winter, so be it. There isn't a lot we can do to reverse it

[winterof79]

Pressure build over North America as the vortex starts to capitulate

In the medium term it is about what happens to the pressure build to our North

ECM

GEM

ECM slides it VERY quickly s/e in to the Continent

 

GEM has a slower progression which pulls in continental winds

 

 

 

Edited February 25, 2017 by winterof79

[jvenge]

GFS 0z keeping the UK at average or slightly above. Europe going on to enjoy a taste of Spring :-) 

 

[Summer Sun]

One to watch is Tuesday with the potential for a fairly widespread deep low with both the central belt of Scotland and London down to around 985mb

[knocker]

This morning the EPS has the pattern changing somewhat as it progresses from the 5-10 period.with the vortex becoming less intense and more diffuse but more to the point by the end it erodes the HP in the Greenland and to replace it with a trough into the eastern Atlantic. So although the zonal Atlantic remains the dominate feature with temps tending to be a little below average in the UK this set up is probably more inclined to some wintry Pm incursions.

Edited February 25, 2017 by knocker

[Frosty.]

Following all the unsettled trough domination the Ecm 00z has a happy ending with a nice ridge of high pressure.

[Nick F]

On 2/20/2017 at 14:02, Nick F said:

IMO we are beginning to see the models finally latch on to the upper flow amplification effects of MJO passing through P8-1  ... having passed through P8 at an unusually high amplitude. Also the troposphere will eventually start to reflect what's happening in the stratosphere too end of month and early March, i.e. a warming at the pole and displacement of the sPV across Scandinavia and NW Russia

What looks most likely, looking at medium range and extended EPS and GEFS is height rises near or just east of Greenland while the Candian trop PV sinks south and the jet + trop troughing sinks south over the Atlantic.

Remember, the models guidance for the trop can often play catch up with what the MJO and stratosphere precursors are indicating ...

 

Parts of a post I made last Monday looking ahead into early March and although model guidance is still fumbling around with the surface synoptics in the medium range they are generally converging on the upper/500mb pattern with the +ve height anomaly over Greenland and Iceland with troughing underneath as I highlighted from the EPS/GEFS mean 6 days ago. The lag effects of MJO P8/1 and the stratosphere warming / PV displacement IMO likely the precursor to the +ve heights around Greenland and Iceland.

Although I have lost the appetite now to hunt for snow and cold + the operationals aren't overly keen on lowering heights / developing troughing further east across central/eastern Europe, which keeps low pressure to the SW and a milder S to SWly flow at times, there is scope for pushing low pressure systems further east into Europe to our south in the medium range, 00z EC high res attempts too days 7-8 before trough disruption stops it. 

00z EC high res, at day 10 keen to extend Azores ridge NE toward UK, however the EPS z500 mean and the EPS mean and spread suggest perhaps emphasis towards lower heights to the SW than the high res

In the shorter-term, upper low dropping SE across UK and EIRE Monday / Tuesday brings quite low heights across the UK.

Fax chart for 12z Monday shows the 528 dam line moving into the west, steep lapse rates with the low heights/cold air aloft, so will be some heavy showers with hail, thunder and even some sleet and snow in the heavier burst across the north and west - as dew point lower from the west in the chilly Pm westerly flow

00z ECM on weatherbell indicating snow for western hills on Monday (Wales, NW England, western Scotland), then perhaps a more organised area of snow moving SE across southern Scotland and far N + NE England Tuesday morning which could be tied in with a trough / front moving S /SE as winds turn more Nly for a time

So don't be surprised to see some snow flakes early next week across the north and west, though settling snow moslty confined to hills daytime, though some spots in the north may see brief settling to lower elevations Monday night.

 

[johnholmes]

The above post from Nick is well supported by the 500 mb anomaly charts I inferred yesterday. They have not been consistent which is why I have hesitated to post them about a week ago. Latterly though they are coming to a more reasonable concensus to the ridging developing in the upper air pattern to the north west of the UK.

See the links below for how they show this in the past 24 hours.

NOAA 6-10 link and the 8-14 is very similar, hence my comment 24 hours ago that it may be a spell of colder weather say 5-10 days or so.

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

and the ECMWF-GFS output this morning now supporting this view, with regard to the ridging positioning..

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

On both sets of charts the actual height of the contour immediately south of the UK looks to be about 552 DM so not desperately cold for early March at height and with a very long sea track. Remember though these are 'average' charts and individual charts over a 24-35 even 58 hours could well be from a more NW area and thus colder.

One thing it does not look like being a 'warm' 2 weeks which is what some of us would prefer!

 

[damianslaw]

Quite a significant pattern change forecast by all models for the start of March, with heights building to our NW, and the longwave trough making a direct beeline for the UK with the jetstream taking a more southerly path, locking much of northern half of the country on the cold side for the foreseeable future - hence a very disturbed cyclonic type spell of weather to end winter and start spring, indeed a major change from the generally anticyclonic pattern that has held greatest influence over the last 6 months or so. 

In this set ups, expect sudden trough formation, and secondary low developments with convection spawning sudden downpours and shower activity. It looks predominantly chilly for the north, with temps average at best, trending colder than average probably, further south nearer average, perhaps a bit above at time. Lots of snow for the scottish mountains, indeed the ski resorts will be very happy, but perhaps a bit too late to salvage what has been a very poor season snow-wise.

Whether we are seeing a sustained pattern change remains to be seen, but recent years have seen sudden pronounced switches in short spaces of time against long term background trends, we've been in a settled dry spell since July, quite lengthy and notably dry and quiet overall.. I'm reminded back to April 2012 the last time we saw a major switch from a lengthy dry settled spell to a very unsettled wet spell lasting a good 6 months.. mmm lets hope we aren't staring at an equivalent April - Sept 2012 spell.. but I've commented before many a time how recent decades have seen lengthy dry periods followed quickly by lengthy wet periods with little variation.

[Frosty.]

I have a feeling that northern uk, especially the hills / mountains will be enjoying the best cold and snow of the winter / early spring at times during the next few weeks or more with a more southerly tracking jet..at last some joy for the Scottish skiing industry!

Edited February 25, 2017 by Frosty.

[lassie23]

From the recent model output, Brian over on theweatheroutlook mentioned the F word, which we managed to avoid mostly this winter, I suppose it was too much to ask to end the winter without anymore of it.

[Frosty.]

15 minutes ago, lassie23 said:

From the recent model output, Brian over on theweatheroutlook mentioned the F word, which we managed to avoid mostly this winter, I suppose it was too much to ask to end the winter without anymore of it.

Indeed, there is a risk of local flooding this weekend across cumbria and looking at the models I can see further problems to come with plenty of rain, especially the w / nw.

Edited February 25, 2017 by Frosty.

[Chris.R]

1 hour ago, Frosty. said:

Indeed, there is a risk of local flooding this weekend across cumbria and looking at the models I can see further problems to come with plenty of rain, especially the w / nw.

Oh THAT F word. Lol 

Edited February 25, 2017 by Chris.R

[Fourty Point Three Degrees]

I do hope this upcoming rainy period will just be just a blink and miss event, after all didn't 1995 and 2006 see some rainy blips in early Spring?

[Eugene]

7 hours ago, winterof79 said:

Ensembles not without interest today trending colder than average with some increasing cold clusters occurring too

Always interested in this data as a precursor to colder weather

If it is March when we see our coldest period of weather of the winter, so be it. There isn't a lot we can do to reverse it

 

So true, find it strange how some feel March 1st means a sudden switch to Spring warmth, March can be a very chilly disturbed month, looks to me like a rather cold unsettled first half to March with temps around average at best.

 

[Lowestoft Weather]

The jet stream looking strong next week with 200+ mph winds aloft, so the potential for another wind storm or two possible.

Today's GFS 12z illustrates these.....

Wednesday PM - Widespread gales/severe gales sweeping Wales & Central/Eastern England. Inland gusts 60 - 70 mph once again!! This does whistle through quickly though, unlike dangerous Doris!!

 

Edited February 25, 2017 by Gavin Plummer

[sebastiaan1973]

8 hours ago, winterof79 said:

Ensembles not without interest today trending colder than average with some increasing cold clusters occurring too

 

If it is March when we see our coldest period of weather of the winter, so be it. There isn't a lot we can do to reverse it

Yet another winter with a positive NAO. The Finnish guys with the research are proving right. Declining solar activity -> Positive NAO. http://onlinelibrary.wiley.com/doi/10.1002/2013JD021343/abstract 

So, this is the final winter with this correlation for a while.

[Frank Trough]

53 minutes ago, Eugene said:

 

So true, find it strange how some feel March 1st means a sudden switch to Spring warmth, March can be a very chilly disturbed month, looks to me like a rather cold unsettled first half to March with temps around average at best.

 

Indeed. March can deliver all kinds of nonsense. Can't help feeling that the shallow surface high at some point in march is going to deliver something colder for the uk, not just the north. 

 

[Matthew.]

The JMA says no to spring and has the Jet running across the far south with Greenland heights establishing

[Frosty.]

Unsettled Ecm 12z throughout and temps dropping after this weekend with rather cold conditions early next week and staying on the cold side further north across northern scotland with temps tending to be closer to average further south. 

Edited February 25, 2017 by Frosty.

[Chris.]

Cant help but think going to need a bit more colder weather than 0c or -4c uppers for snow in the scottish highlands though.  But hopefully a spot or two of the low pressure will help deliver the goods.

[Summer Sun]

The beeb's week ahead forecast earlier mentioned the possibility of a 'potent low' later next week

One to watch for sure

[Frosty.]

29 minutes ago, Matthew Wilson said:

The JMA says no to spring and has the Jet running across the far south with Greenland heights establishing

Jma to the rescue? I guess there's a first time for everything.

[phil nw.]

The problem with a southerly tracking jet when Greenland heights are not strong is that it just leaves much of the UK under the influence of successive Atlantic lows,thus a wet and windy regime with frequent frontal systems traversing the country.

 

Really only the Scottish highlands are likely to see meaningful snowfall in the chilly air up there.

The real cold is locked to our north down to about 60N where the -6/8C uppers lurk

 No sign of northern blocking strengthening sufficiently to bring a taste of Winter any further south so we are looking at a mobile westerly unsettled spell going into early March.

My least favourite set up,wet and chilly at times but nothing out of the ordinary temperature wise.I think after a week or possibly two of this i will be willing the return of some mid-latitude blocking around the UK.

 

Edited February 25, 2017 by phil nw.

[Singularity]

It's been a long time since we last had a jet stream shifted south yet remaining quite strong and sending lows across the UK. With a few tweaks and occurring in the depths of winter it can be a snow-lover's nirvana - but on this occasion, due to the time of year plus quite possibly the overall warmer state of the climate, this will only ring true for up on the mountains in the north, and even there perhaps only intermittently.

   

We have a fairly strong bit of MJO activity in the IO at the moment, in terms of wind signals - convection is lacking. The odd run here and there has toyed with moving the ridge from our N to our NE seemingly by way of response, but it seems to me that with signs of the GWO nosing into phase 4, the models are finding too much of a subtropical ridge + flat westerly signal to let this really take shape. Whether that 'too much' is down to model judgement remains to be seen - I've often seen an MJO signal rise up to seize the day having initially been underestimated... but that was back before the winter of 2016-17 which if anything has displayed the reverse tendency, catching a fair few forecasters/climatologists out - including me of course; the MJO enthusiast.

Still - I believe the blocking high to our N should start to be able to exert a more direct influence in the 8-16 day range, though from what location exactly is hard to say. If the models keep trending toward MJO phase 3 to follow phase 2 then a failure of the blocking to move to our E/NE could mean that it sticks around to our N for a long time. Increasingly I worry that with GWO orbiting negative - albeit weakly - the jet might keep on firing across under such blocking to bring about an exceptionally unsettled and wet March. We could really do with the hints of El Nino in the Pacific forcing a bit of a kick in GLAAM to hold up the Atlantic lows. Hopefully a Kelvin wave will turn up to help things along.