Model Output Discussion October 2012

[BLAST FROM THE PAST]

The GFS model is definitely picking up on a blocking pattern in FI. A trend to keep an eye on as we move into next week. Could we be in for a cold north easterly floe as we finish Ocotober?

One might say that the blocking pattern is already in place? I agree though an increasingly cold signal for latter 3rd to backend of October

BFTP

[SMU]

http://modeles.meteociel.fr/modeles/gfs/runs/2012101018/gfs-3-108.png?18

theres your chance of snow for Eastern Scotland at 108 on GFS now- ~ 12 hours behind the ECM-

ZDL at 400M- Snowline 250M- mix at 150/200 M

S

[Cloud 10]

http://modeles.meteo...fs-3-108.png?18

theres your chance of snow for Eastern Scotland at 108 on GFS now- ~ 12 hours behind the ECM-

ZDL at 400M- Snowline 250M- mix at 150/200 M

S

Is that a small hatched area over eastern Scotland? i think it is!

http://modeles.meteo...2-108.png?18?18

[SMU]

yep- To be fair im sure a few may have spotted it on the ECM this morning when I posted it-

but it wasnt a real easy one...

S

[Swave Snow]

the fun begins this i hope is going to be a belter of a winter bring it on

[Frosty.]

A very low pressure dominated gfs 00z op run for next week and temps look a little below average for most areas. The next few days bring a risk of localised flooding but for areas which haven't previously been affected, northeast scotland looks in line for around 3 inches of rain from tonight, tomorrow and into saturday as the front more or less grinds to a halt and little ripples run along it to pep up the intensity of the rainfall at times. Most of the uk having rain at some point this weekend, a risk of some heavy rain in the south and the far north but details are still a bit sketchy and need to be firmed up more before we have a clearer picture, although low pressure is covering the uk next week, there should be plenty of dry and sunny weather between the downpours. rainfall looks showery in nature and some areas may escape relatively dry while others get local flooding.

[Gibby]

Good morning folks. Here is a rather different looking report this morning from the 00zs output as it is the first time since doing these that all models sing from the same hymn sheet throughout their respective runs duration. There is very little difference between all the outputs with only day to day variations on an unsettled theme.

The models all show the UK to be governed by Low pressure over or just to the North and West of the UK. All models shows troughs delivering periods of rain followed by heavy showers. The showery spells may mean that some areas in shelter and away from windward coasts see some longer drier spells given we are now in mid October. Winds will blow from a Westerly point, strongly at times. Temperatures will be a little below normal at times and it will no doubt feel cold in the breeze and rain. Flooding problems could become an issue at times, especially in those areas where ground catchment areas are already very delicate.

The GFS Ensembles all look very normal for this stage in Autumn with rain and wind in abundance under a Westerly Atlantic based flow. Things look drying up a bit for SE locations late in the run indicative of a possible pressure rise.

The Jet Stream unsurprisingly goes back to a position near Southern Britain or even further South in the next few days as we move out of the current broken phase over the UK.

In Summary a very unsettled spell is on the way. Low pressure will continue to be steered Eastwards from the Atlantic towards and over the UK where they will often stagnate delivering periods of rain or heavy showers in cool and blustery West winds. There is no sign of anything shown this morning that could break us out of this pattern to something drier and colder from what I have seen.

[shedhead]

Some pretty impressive blocking showing up on the overnight runs, particularly ECM, which if it transpires should ensure a colder final third of October.

Edited October 11, 2012 by shedhead

[Nick F]

Yes, a persistent northern blocking signal into the medium range and perhaps longer term too. 500mb heights remain high from Svalbard west to Greenland, with the resulting block forcing a disturbed and highly zonal flow across the UK and western Europe for the foreseeable. Which means a succession of lows across us and lots and lots of rain and windy at times too!

Hints that the block will shift west with highest heights eventually centred over Greenland/NW Atlantic, so this may open the door for colder air to sink south later this month. Though this early on, high ground of Scotland only likely to receive anything wintry.

[Glacier Point]

The presence of a substantive block centred around Svalbard is very consistent with where the GWO / MJO forcing is right now, allied to a weak zonal wind anomaly prevelant in the upper atmosphere which has prevented any real polar vortex to establish.

Moving forward, this pattern should persist into November with the suggestion that we may see a more meridional flow around the North Atlantic, probably with a focus around Iceland and mid Atlantic for any ridge development (ECM a bit progressive in this respect but right long term idea). Either way, I'm very happy to endure what is quite an unusually autumn phase.. with good cold going where it should.

[Frosty.]

I could not resist posting this chart because it would be a dream looking synoptical set up for all cold fans on here, a developing northerly blast of some potency and longevity, if this pattern trend continues, I will be very happy, and so will the scottish ski industry. A lot to mention about the 6z before we hopefully get there, a very unsettled phase coming up with low pressure in control for long periods, it looks on the cool side initially but the 6z shows a warmer sw'ly or s'ly in FI with a briefly more settled trend for the south and east in particular although the north and west would remain more unsettled but milder, then that possible trend towards a shock early wintry blast towards the end of october into early november..shame the gfs run ended before the really interesting stuff arrives.

Edited October 11, 2012 by Frosty039

[bluearmy]

i notice a weak ncep trend to shift the lowest heights this side of the NH in a fortnight with the major emphasis of the blocking towards the aleutians. for the blocking to move around doesnt bother me - as long as the NH remains blocked with no strong vortex forming. if the block was to stay centred in one area for weeks on end, i would expect the pattern to eventually break down and we are a fair distance from when the current setup would deliver anything really wintry. if the NH remains with a meandering blocking signal for the next month, i think thats a better option for a cold start to winter.

[Radiating Dendrite]

Hopefully I won't be accused of cherry picking too much but I thought I would post this chart because it would be a dream looking synoptical set up for all cold fans on here, a developing northerly blast of some potency and longevity, if this pattern trend continues, I will be very happy, and so will the scottish ski industry. A lot to mention about the 6z before we hopefully get there, a very unsettled phase coming up with low pressure in control for long periods, it looks on the cool side initially but the 6z shows a warmer sw'ly or s'ly in FI with a briefly more settled trend for the south and east in particular although the north and west would remain more unsettled but milder, then that possible trend towards a shock early wintry blast towards the end of october into early november.

Very similar synoptics to that of the 17th December 2010! Obviously not as potent, but very interesting given the time of year!

[johnholmes]

re the comments in this and other threads about the blocking way north with mobility between 50-60N. I's an unusual set up and one I cannot recall seeing before in October - perhaps one of you can show a sequence of 5 days or more where it has occurred before?

The 500mb anomaly charts have been touting this idea for several days now so I would give a fair degree of confidence to this actually occurring in the latter half of this month and possibly extending into November. The actual location of surface features will be hard to pin down for some time, hence the changes we see in the 2x and 4x synoptic issues from those models predicting patterns into this time scale.

Currently we do not have a 'stationary' upper wave length, that is 4 major troughs around the northern hemisphere, the prediction is that this is what we will get post T+168-its highly probable in my view. Once that wavelength is set up then they do tend to persist, hence I suspect why UK Met and their 16-30 day temperature outlook has not changed for a week now. They must feel that the overall model guidance, a huge variety they both make and receive, on balance suggests below or even rather cold weather into the first week of November. Eventually this 4 wave pattern will break down, regardless of what the Stratosphere shows but a warming Stratosphere must help for it to re establish that type of wavelength again.

Far too early to make forecasts about winter but by the end of the next 2 weeks fairly considerable evidence should be available to give decent guidance into the start of winter, that is December. Beyond that who knows I certainly don't.

But it is an unusual set of anomaly charts and similarly with the synoptic charts at the moment.

Perhaps this should be in one of the other threads admin/mods-so please feel free to move it if you think the same?

Edited October 11, 2012 by johnholmes

[phil nw.]

Those Arctic height anomolies are also responsibe for the unsettled and at times very wet conditions that the UK are expecting over the next week to 10 days.

The jet stream now on course for the UK with troughs crossing west to east from the Atlantic.The chart for T120hrs from the UKMO shows this pattern established.

Just to underline the fairly untypical setup and looking at trends i had a glance at some other data.

The graph shows the NAO index based on the overnight outputs

all going negative soon.

The 2 Ens 500`s for the expected NH pattern at day 10

continue with those heights over the Arctic and a somewhat disrupted vortex.

[Methuselah]

Here's an interesting chart from 2000:

[MR EXTREMES]

Here's an interesting chart from 2000:

stuck in a rutt wet windy and cool. but 2000 was chilly but not a 2010.

[Frosty.]

The uk looks like being boxed in by various troughs of low pressure from this weekend onwards with high pressure developing over the western atlantic and with more high pressure across the far east of europe towards russia, the PFJ well to the south over france so next week looks cooler than average with showers and longer spells of rain, windy at times and a increased risk of further local flooding chaos, the gfs 12z then shows a warming trend as winds go around to a s'ly to sw'ly direction and tropical air is pumped northwards but it remains unsettled, more unsettled than the 6z showed in the same timeframe as the whole pattern has been shunted further east which means the arctic blast shown on the 6z has been reduced to a brief Northerly toppler and the arctic supply is soon cut off but with a cold high pressure pushing in from the northwest with overnight frosts.

[johnholmes]

I like the tv forecast clips frosty

[Frosty.]

I like the tv forecast clips frosty

Thanks John, i'm going to post them regularly from now on.

[johnholmes]

Thanks John, i'm going to post them regularly from now on.

I suspect they could become quite popular especially in possible snow set ups, and if you could get the day showing that will also help?

[BLAST FROM THE PAST]

Thanks John, i'm going to post them regularly from now on.

Frosty interesting post. Its new moon and perigee within 4 days 11-15 Oct. Looking at that Sunday chart and this from GFS....I am a tad concerned about flooding and possible 'extreme' event. Are MetO putting any warnings out yet?

BFTP

[Frosty.]

I suspect they could become quite popular especially in possible snow set ups, and if you could get the day showing that will also help?

Yes John i'm looking forward to posting them for snowy set ups and when the weather pattern is so unsettled as the models are showing for the next few weeks.

And to BFTP..I agree about this weekend and there is still some uncertainty about the track of that system on sunday but it's been closely watched as the south could have a nasty day on sunday with very wet and windy weather with flooding due to the already saturated ground.

Edited October 11, 2012 by Frosty039

[AWD]

No question about it, its certainly looking very unsettled for the foreseeable future. All models show a strong jet crashing into Britian, bringing low pressure sytems with it.

GFS

UKMO

ECM

There seems to be some mega depression over the Eastern Seaboard in the coming days, is it an ex hurricane or something?

[BLAST FROM THE PAST]

Yes John i'm looking forward to posting them for snowy set ups and when the weather pattern is so unsettled as the models are showing for the next few weeks.

And to BFTP..I agree about this weekend and there is still some uncertainty about the track of that system on sunday but it's been closely watched as the south could have a nasty day on sunday with very wet and windy weather with flooding due to the already saturated ground.

Keep us all posted mate

BFTP