Model Output Discussion 4th Dec.2013-12z onwards.

[Paul]

Nice one Paul, a query though, in that first link I don't notice anything different from before? Should they not look like the equivalent GEFS ensembles or am I missing something?

 

 

They're means from the ECM EPS, so single maps, but different to the deterministic ECMWF model here

http://www.netweather.tv/index.cgi?action=ecm;sess=

[gottolovethisweather]

They're means from the ECM EPS, so single maps, but different to the deterministic ECMWF model here

http://www.netweather.tv/index.cgi?action=ecm;sess=

 

Thanks I'll have to stick to other websites who I shall not name for my fix of those ensemble spreads for now.  Nonetheless, sterling work netweather towers.

Edited December 12, 2013 by gottolovethisweather

[Newberryone]

Yes, the trend that began a few days back to erode the influence of the High pressure most especially across SE UK is moving further up the gears with the latest ECM really ratcheting up these secondary lows that are forming on the boundary of the polar front jet as bitterly dense cold Canadian arctic air meets moist warm atlantic air and spawns some very intense cyclogenesis.

 

Hopefully, at a weeks distance the intensity and track of that low is adjusted to something much less ominous than suggested on the ECM - but the MSLP spreads make it easy to see the areas in which these rapidly deepening secondary lows might develop, and where in future outputs they may track

 

 

We should not expect much amplification within the 10 day period with the pattern very fast and flat, and therefore polar maritime incursions will be restricted further north and very temporary as one low replaces another. This isn't unusual at this time of year with a very deep polar vortex in situ over Greenland and NE Canada, but on the basis of how significantly cold it has been in parts of Canada and the US, then we should expect some deep lows to develop and then sent downstream across the atlantic towards the UK

 

Edit: The charts look a bit squashed , but they open ok when clicked on 

Just six days ago who would have thought we'd be about to enter such a possible turbulent spell of weather as all the pointers then indicated strongly towards a continuation of the bartlett style setup.

While many of these lows admittedly may come to very little if anything, I can't help but feel the potential for some significant windstorms is very real at this juncture. 

Even as far ahead as Sun week, Dec 22nd, despite the fact there's slightly more amplification, one need only look to the North Atlantic to see the next potential low heading out of Newfoundland and very little I would imagine to suggest it won't follow the same route as previous lows. 

[EML Network]

The Control run on this mornings 06 GFS run can only be described as SCROOGE.

 

Total zonality showing for XMas day, that's about as zonal as it gets :-(

 

[nick sussex]

Morning all

 

Just perusing the latest outputs, not much change since last night but the models do seem to at least resist from keeping the PV as one uniform blob to the north, there are occasionally  some disruptions shown with fragments of this moving around.

 

That's not to say we're going to see something wintry pop up but indications that the jet sinks a little further south with time, there is still a reluctance though to lower heights in central Europe.

 

Looking at the ECM De Bilt ensembles the main clustering windwise is still towards the south/sw, a few runs showing a more nw component but these are very much in the minority.

 

http://www.weerplaza.nl/15daagseverwachting/?r=midden&type=eps_pluim

 

The models are still unable to push low heights sufficiently se to take De Bilt on the western side of any low.

 

As a rule we can often correlate the pattern with what happens in central Europe because this is like the bellwether for the UK when you're trying to move from a flattish west/sw set up to a more favourable nw/se jet axis.

 

The ECM for several days has tried to show an improved polar profile aswell as troughing digging further south in its latter stages but at the moment this does seem to be marooned there, also noticeable has been its morning operational being generally flatter than the 12hrs, I wonder if this is some sort of bias we're seeing or just coincidence.

 

Moving forward I think any changes won't be quick but more gradual in terms of lowering heights in central Europe, we know that the PV isn't going to suddenly take a holiday and move completely away from the Greenland area however its whether we can see some disruption to it and some forcing applied to help the pattern edge further south and east.

 

 

That's the T240hrs from this mornings ECM run, you can  see there the main PV located towards Canada , some pressure rises near the pole and a lifting out of those lower heights over Greenland, the low stuck over the UK, going forward its possible get a more favourable jet axis even with the PV there if we can see that high to extend a little more influence towards Greenland.

 

I think that's a realistic way towards a colder form of zonality, however we need to see these charts moving in towards the more reliable timeframe.

 

Todays horror rating has dropped to 7/10!

 

Snow rating within T240hrs has crept up a little to 1.5/10

 

My new White Xmas rating!  3/10, given the UKMO view of this in terms of just snow falling rather than laying in this type of pattern theres always the chance you might get lucky and be in the colder PM air between lows, especially for the north and Scotland.

 

[Tim Bland]

I think recent winters have really changed our perception / expectations. What we are seeing is "Typical" UK winter weather. I just hope we dont see another run of mild winters like the end of the 90s!

[snowmadchrisuk]

Well it is now official it was the quietest hurricane season since 1982 , I have just checked the archive for the Winter 82/83 and what an awful Winter that was, started off in December where we are right now, then the Euro High built back in over and over and the P/V remained strong throughout , all I could find was 2 24hr topplers throughout the whole winter... Let's hope conditions over the other side of the Atlantic won't have quite such an effect this year... In that Winter Feb was the best month , but most of the month was close but no cigar... 

 

My question is is there any known link between really quiet hurricane seasons and the UK Winter. ? 

[Frosty.]

Hope i'm not exaggerating but the Gfs 06z op run looks even more disturbed than the 00z with several potential storms hitting various parts of the uk at different times, the coming weekend looks like becoming very windy with severe gales or storm force gusts, the most severe conditions could be the northwest corner of the uk as a nasty looking depression hits nw scotland, talking about temperatures seems academic when there are more serious problems such as the strength of the winds and frequent spells of rain, most of it heavy with sunshine and squally showers separating the persistent rain. As for temperatures, again it's the north of the uk, especially scotland which has the coldest zonal conditions with snow on hills and occasionally to lower levels but mostly at elevation, occasionally the colder polar maritime air digs further south into southern uk but there is rather more fluctuation across the south between milder temps / average & colder days whereas the further north you are, temps are generally on the chilly side of average, especially across northern hills and mountains where temps could be sub zero at times, for example at Munro levels of 3,000 feet (914 metres above sea level).

Edited December 12, 2013 by Frosty.

[nick sussex]

Well it is now official it was the quietest hurricane season since 1982 , I have just checked the archive for the Winter 82/83 and what an awful Winter that was, started off in December where we are right now, then the Euro High built back in over and over and the P/V remained strong throughout , all I could find was 2 24hr topplers throughout the whole winter... Let's hope conditions over the other side of the Atlantic won't have quite such an effect this year... In that Winter Feb was the best month , but most of the month was close but no cigar... 

 

My question is is there any known link between really quiet hurricane seasons and the UK Winter. ? 

I think its quite difficult to prove a clear link because of so many other factors, however from what I've read a quiet hurricane season especially one where there hasn't been a hurricane before September is more likely to correlate with a colder than average winter for Europe and NA. The exception being the far ne of the USA which was warmer because of blocking towards Greenland. Again though there are so many teleconnections that need to be brought into the equation that I think its incredibly difficult to come down clearly on either side of the debate.

[johnholmes]

for newbies this may help to see just how mild or cold it may feel.

Look at the dewpoint charts, say the Extra and msl I mentioned in an earlier post. Low values say 5C or below, especially if coupled with any marked wind speed and it will 'feel' cold. 5c probably represents what we call returning Polar Maritime air (rPM), that is air that started life way north, probably the far north of N America or Greenland but has then been brought way south before moving NE again. Characterised by sunny spells and showers, rain, hail, possibly sleet but with snow over higher ground especially in the north. At or below 0C then it is much more likely to be direct Polar Maritime (PM) or possibly with the isobars from the north then Arctic Maritime (AM). Values of Td above about 8C or so in winter usually indicate air from a southern region Tropical Maritime and usually characterised by fairly cloudy skies especially on windward coasts and hills, hill fog, it can brighten up east of the main high ground in the UK, sometimes aided by the Fohn effect.

This is not a totally fixed set of values, more to give new folk an idea of the numbers to look for with dewpoints.

 

hope that helps and thanks Jo for your comment, nice to see the modern generation of Met forecasters using the old ideas!

 

Finally, although it may take all the fun out of wondering what the weather will do, the 6-15 day outlooks and the 16-30 day variant, from UK Met is by far the most objective reading of what the models are showing than anything and I mean anything you will read either here or any other web site. Yes of course they do change, be a bit daft if they did not as the professionals analyse and decide which model(s) is the most likely to verify. Yes of course they get it wrong at times but not that often which is how it should be from them. No doubt folk on here will disagree and quote those occasions when they did get it wrong but take my advice they are correct some 80% of the time out to about 7 days, beyond that not sure what the statistics show, maybe Jo can help out with that?

Edited December 12, 2013 by johnholmes

[Man With Beard]

Frosty - agreed, the charts today bring back memories of a Christmas Day in northern France not so long ago, when a storm hit with more intensity even than our 1987 storm - it will all be about where the 'Mother low' sits (the giant one near Iceland) - an unfavorable position (or favourable if you like storms) could throw more than one dangerous storm (80mph winds+) over the UK as early as next week.

[Iceaxecrampon]

Interesting feature on GFS LP developing from the Azores for Wednesday the 18th - possible collision with the vicious cool temp low S of Iceland for ppn?

 

 

Thursday 19th December:

 

 

Ian

 

 

Edited December 12, 2013 by Iceaxecrampon

[Don]

 

In that Winter Feb was the best month , but most of the month was close but no cigar... 

 

 

Feb 1983 had a CET of 1.7C so there must have been a few wintry events that month?  My memory is rather vague for that month believe it or not!

[TwisterGirl81]

Just a quick question but why do most lows always seem to swing up towards the northwest of the UK?

 

Looking at the 06z GFS airpressure this morning looks like it is going to be really windy next week, possibly stormy, mostly in the northwest.....

 

I'd much rather have full on zonal weather rather them the high pressure cloud and fog in the winter so i was happy....I just hope we get a good storm in the south!

[Methuselah]

Can we please stick to discussing the models?

[Bristawl Si]

Good post...the standout thing for me here is just how anomolously warm Scandi looks set to be, particularly the southern half of Finland.  IF this verifies it's hard to see much lowland snow cover persisting south of the 65th parallel, with a steady thaw also likely across parts of NW Russia, especially if it rains heavily. What implications, if any this has for UK cold in the New Year remains to be seen.

Virtually nil.

Land masses cool v quickly when subjected to v cold temps. So IF it does turn v mild in Scandi, etc a return of cold air will soon cool the land again, with snow to follow.

[Tom Quintavalle]

Feb 1983 had a CET of 1.7C so there must have been a few wintry events that month? My memory is rather vague for that month believe it or not!

Hi Don,

A very localised event but I think you'll find that any snow junkies from the extreme east of Kent, had plenty to celebrate!

The 500 hpa chart below was roughly at the mid-point of a 36 hour East Kent snow streamer. I was fortunate enough to get to the Dover/Folkestone area and witness the amount of snow that had fallen, incredible! Back home in the extreme NW of the county we had a slight dusting but on top of the Downs at Capel-le-Ferne, overlooking the Channel and circa 550 ft asl, level snowfall amounts were just under 1 foot. There had been a huge amount of drifting though in the strong NNE/NE winds, with some drifts up to the eaves of the many bungalows that can be seen in the area.

The heavy and prolonged snow showers were accompanied by thunder at times and there were quite a few reports of lightning strikes on properties, along that coastline.

One of the reasons for the intensity of the snowfall was the anomalously high sea temperatures, for the time of year, in the S.North Sea and English Channel.

Edited December 12, 2013 by Kentish CZ

[Chris K]

Just a quick question but why do most lows always seem to swing up towards the northwest of the UK?

 

Looking at the 06z GFS airpressure this morning looks like it is going to be really windy next week, possibly stormy, mostly in the northwest.....

 

I'd much rather have full on zonal weather rather them the high pressure cloud and fog in the winter so i was happy....I just hope we get a good storm in the south!

 

I could probably provide you with one factor as a basic explanation.

 

The reason for these storms moving NW of the UK is due to the path of the Jet Stream coupled with how intense it is. Due to the injection of much colder air into the Atlantic meeting the warmer, moist air from the South, there is a higher temperature gradient which causes the Jet to intensify.

 

These storm depressions tend to form along the Northern flank of the Jet and follow the path of the jet stream until it finds it's 'exit point' and weakens after becoming 'detached' from it.

 

 

 

Overall though, I believe the prevailling direction of the Jet Stream as it nears the UK is from SW to NE, hence why they are following this rather 'classic storm track'.

 

Also, if the models have exaggerated how much energy is in the Jet as well as the direction of flow, as we approach T+0, the depressions may be weaker and/or move on a different path.

Edited December 12, 2013 by Chris K

[bluearmy]

general theme for the jet to sink south through the next fortnight continues. cool, possibly cold zonality with features in the flow to keep us interested. no sign that the high heights to our south will break to allow a euro trough to form (other than transient). by the end of week 2 on the ecm ens, we are not far from being completely north of the mean PFJ. if the winds recede for any length of time, could be a bumper new year on the scottish ski slopes. will be lucky dip though on timings as could easily be facing 70 knot winds!

[johnholmes]

I think I also remember John H mentioning that if the depression is stronger, they have a tendency to pull more West as they move along.(Correct me if I am wrong)

 

as the depression moves be it east or north east; if it deepens rapidly then the turn is to the LEFT of its previous track. I think that is what you meant?

[Chris K]

 

I think I also remember John H mentioning that if the depression is stronger, they have a tendency to pull more West as they move along.(Correct me if I am wrong)

 

as the depression moves be it east or north east; if it deepens rapidly then the turn is to the LEFT of its previous track. I think that is what you meant?

 

 

Yes that was it. Sorry John it made it look like I was misquoting you.

[shedhead]

Virtually nil.

Land masses cool v quickly when subjected to v cold temps. So IF it does turn v mild in Scandi, etc a return of cold air will soon cool the land again, with snow to follow.

A direct feed off of a solidly frozen Scandi would be much colder than a direct feed off of what we look like seeing up there next week. Of course this is all yet to happen, hence my point that we will have to wait and see 'what if any implications' there are for UK cold.

Edited December 12, 2013 by shedhead

[Paul]

Latest from Michael Fish:

 

https://vimeo.com/81715650

[mountain shadow]

Well the 12z's have been more amplified and offered more wintry prospects than the 0z's lately, lets hope the trend continues of more amplification in the mid atlantic and pressure loweing in central Europe towards Christmas and thereafter.

[swilliam]

A direct feed off of a solidly frozen Scandi would be much colder than a direct feed off of what we look like seeing up there next week. Of course this is all yet to happen, hence my point that we will have to wait and see 'what if any implications' there are for UK cold.

None I think,

this is the 850s for the middle of Sweden (taken as being the average)  mostly around -5C except for a couple of days. Given the existing snowcover and virtually no worthwhile daylight - not much of a thaw I would think.