Model Output Discussion - 23rd Jan - 12z onwards

[carinthian]

I think we all need to learn a lesson , Just be carefull of the every day run from the models . follow the trends and you will be happy...    

The trend is for high pressure to centred over the British Isles in 10 days. Its where it locates after that is the intrigue, the UKMO seems to think a more westerly flow will take over again and others ( my source have a fairly high probability of Arctic Continental flow as opposed to Atlantic .

C

[summer blizzard]

Another trend run. Northerlies followed by a fat high.

 

[SE Blizzards]

Kind of  but kind of not. My point all along has been that this risks being a 2-3 day wonder. The pressure out west from a powerful, non amplified and non bifurcated jet suggests to me from past experience considerable likelihood that the whole event will be shunted east nearer the time and we may then have a toppler. That's what the ensemble scatter seems at least to consider possible. Hopefully not and this digs in, and we see some proper upstream blocking in evidence.

Well the 12Z ENS that you posted rather contradicts a 2-3 day wonder as they clearly show at least a week of cold weather!? That surely can't happen from 'a toppler', or can it? If so - that would be one of the longest topplers i've ever seen that's for sure.

 

Anyway, all will be revealed over the next few days. 

 

Let's hope the 18Z has been on an all-dayer and goes on to show a 1963 freeze.

Edited January 26, 2015 by SE Blizzards

[Rocheydub]

non amplified and non bifurcated jet 

OK! OK! We get that you've found a new word!!! You've used it in loads of posts these last few days!!!!!  :-)

This does really have a feel of a push east as we near the weekend and beyond, but just because that's what's happened in the past, doesn't mean it will again! (He said hopefully) 

The actions of some of the systems around Greenland suggest this block may have some teeth, time will tell.

[Snowman.]

GFS on snow.

 

By midday Wednesday, the front has pushed SE where on its front edge it falls as rain but on its back edge it's likely to fall as snow over places with elevation or further north but even possible to lower levels as the DPs plummet but the temps are little on the marginal side or won't allow for settling snow.

 

 

 

Front clears SE and this is where the potential starts. Decent snow showers in the west begin to pile in so I would expect some settling snow here but how much is up for debate and those with elevation are likely to get some decent falls.

 

 

 

By T60 (Very far out so don't take this as set in stone yet!) the GFS introduces a front pushing east in the South subject to change could be further north or further south this is likely to give some of the very first snow fall in nearly two years to the south maybe even some settling but lets not get carried away. All this time it's STILL snowing in Scotland(Something that isn't unheard of) and the west.

 

 

This is as far as I will go but it's likely a mild sector will flow south from the north. May I also not from Wednesday onwards this is the WARMEST the DPs get. Still subject to change.

 

 

But short lived as colder air sweeps back through.

 

 

I won't continue any further but for at least this week we should be happy with what coming up.

[damianslaw]

Well beyond the reliable timeframe, but very much worth discussing is the ECM output this evening and to some extent the GFS. ECM is showing the azores high ridging into the country and quickly building over the country with little energy in the atlantic, indeed signs of dare I say it 'retrogression', it may well be gone tomorrow, but it is yet another possible option on offer after the cold northerly spell retreats.

 

The northern hemisphere is undergoing quite a change at the moment, the PV set to weaken once again, a high pressure build over the country would very much have every chance of eventually ending up in a northerly position or more favourable position for sustained cold, and mid Feb certainly not to late for sub-freezing conditions still.

 

This is certainly not a forecast of how I think things will pan out, its just a possible scenario. If we look at the current spell of westerlies, they have only lasted barely 4-5 days..

[Man With Beard]

Just a note on the ECM mean at T240 - that's the most organised PV I've seen all winter and it is centred around... Greenland. I know the mean is sometimes wrong but this one looks a strong bet.

I'm guessing then that longer term hopes for cold weather are based on High Pressure ridging to the NE ... because I can't see that PV shifting too quickly from there, if the mean is anywhere near right.

[Mucka]

Some great charts for cold lovers this evening, particularly after ECM 12Hz run.

 

Are there any sources of EURO4 which has higher resolution dewpoints.

 

Not that I know of unfortunately.

 

Will the temperature plummet suddenly once the front clears or slowly over the six hour period?

 

Most of England should find the temperature drops by several degrees Celsius over a couple of hours. So if you are bathing in 8/9C in the South at mid day you could be in 4 or 5C by 2PM for example so a noticeable drop if you popped indoors just before the cold front passes through and then back out once it has passed, especially when we add in the wind chill.

Edited January 26, 2015 by Mucka

[Frosty.]

We have had a nice upturn in fortunes since the 0z runs and I hope it continues tomorrow, the longer the cold lasts the better! Here are a few promising GEFS 12z perturbations for next week.

Edited January 26, 2015 by Frosty.

[johnholmes]

Enjoy the cold folks, many will see snow, from tomorrow on, and I would suggest the snow risk remains for favoured areas for some days to come?

The latest major anomly charts do not, to me, suggest any marked change in the 6-10 frame. Nor any major signal, backed to some extent by the GFS MJO version in the longer frame. Not deep cold but probably a spell of more surface type cold looking at the NOAA 8-14 chart this evening.

Edited January 26, 2015 by johnholmes

[East_England_Stormchaser91]

Im having doubts as to whether the PV at 240hrs is being well over exaggerated. The models seemed to over do the Atlantic and PV after the last cold snap, and now look whats happened. 

With the Stratosphere over the Canadian Arctic being substantially warmer than the Siberian side, I expect more blocking to occur as we move further on into February. The earlier GFS may just have been a teaser of what could possibly happen...

[nick sussex]

Very good agreement now between the ECM/UKMO and GFS at T120hrs with the overall pattern. It's taken some time after the initial Euro troughing differences.

 

The UKMO seems to have done quite well on that front, the GFS until today has modelled that poorly.

[bluearmy]

The 18z is less amplified upstream at day 5/6 ( but strangely pretty well recovers itself within 12 hours ..... Interesting)

More clues re the envelope for next week

Edited January 26, 2015 by bluearmy

[southbank]

Frustrating that despite the warming going on the Canadian side of the pole , as alluded in the strat forum , it doesn't deliever a knock out blow to allow the Pesky AH ridge northwards and give a true HLB , still the week ahead is looking cold with snow for some

[Freezing-Point]

This run showing the colder air more established over the UK by Saturday.

[Biggin]

I must admit - there's been an improvement for cold

The improvements are based around a seperate blocking HP cell forming around SW Iceland

Will be monitoring this closely over the coming runs

Wow

Edited January 26, 2015 by Biggin

[Geordiesnow]

Very good agreement now between the ECM/UKMO and GFS at T120hrs with the overall pattern. It's taken some time after the initial Euro troughing differences.

 

The UKMO seems to have done quite well on that front, the GFS until today has modelled that poorly.

 

The UKMO still has the troughing further East than the ECM/GFS so mild sectors will be less of an issue and your in the Northerly flow quicker as a result. The questions still remains of how far eastwards the troughing gets,how much amplification in the Atlantic and how will that nuisence low pressure system/shortwave play out, the general trend has been set for a few days now, its kind of down to the detail and this will decide how long this cold shot could last for and how much snowfall there could be.  

[Severe Siberian icy blast]

Could be a split vortex in fi , could be very interesting keep watching over Greenland , if we can pull that that vortex northwest we could be in a prime location for some deep cold .

Edit: yuk or maybe not ! But to be expected I suppose the mods will always flatten out the pattern in fi .

Some good upgrades today as the days worn on . Be nice to get some cold and snow to low ground for the first time widely for a long old time .

Edited January 26, 2015 by Severe Siberian icy blast

[nick sussex]

The GFS 18hrs run was somewhat nervewracking as the shortwave ahead of the ne USA low took quite a while to separate and clear se'wards,the overall trend is similar though.

 

I think if you get an earlier separation then an extension to the cold looks a decent bet.

[Nick F]

Well it looks like the upgrades continue on 18z GFS with the Nly this weekend into beginning of next week, certainly with regards to the depth of cold based on a lowering of T850s.

What's nice to see both from ECM and GFS this evening is keeping the amplified ridge to the west for longer and, also, perhaps more crucially, the secondary lows following the jet dive south to the west of the UK rather than SE over the UK ... so without those pesky warm sectors!

I suppose the only negative maybe the 'wishbone' effect of a northerly, whereby coastal areas hog all the wintry showers while it stays dry, sunny and cold inland, unless we get some trough or frontal activity pushing south - of which I'm sure there will be.

[J10]

Very much a case of you take money and your choice, for example on the GFS a beaut of a NNW flow over the UK for Sunday morning, however on the negative side its comprises the longevity of the run later on (A little).

 

 

GFS seems a bit cleaner than earlier runs.

 

So in that sense not an upgrade or a downgrade but a variation on a theme.

Edited January 26, 2015 by J10

[J10]

Well it looks like the upgrades continue on 18z GFS with the Nly this weekend into beginning of next week, certainly with regards to the depth of cold based on a lowering of T850s.

What's nice to see both from ECM and GFS this evening is keeping the amplified ridge to the west for longer and, also, perhaps more crucially, the secondary lows following the jet dive south to the west of the UK rather than SE over the UK ... so without those pesky warm sectors!

I suppose the only negative maybe the 'wishbone' effect of a northerly, whereby coastal areas hog all the wintry showers while it stays dry, sunny and cold inland, unless we get some trough or frontal activity pushing south - of which I'm sure there will be.

 

I think we are due a good Northerly they have been in scarce supply this decade although Dec 10 was tasty. ,

Edited January 26, 2015 by J10

[Cloud 10]

Well it looks like the upgrades continue on 18z GFS with the Nly this weekend into beginning of next week, certainly with regards to the depth of cold based on a lowering of T850s.

What's nice to see both from ECM and GFS this evening is keeping the amplified ridge to the west for longer and, also, perhaps more crucially, the secondary lows following the jet dive south to the west of the UK rather than SE over the UK ... so without those pesky warm sectors!

I suppose the only negative maybe the 'wishbone' effect of a northerly, whereby coastal areas hog all the wintry showers while it stays dry, sunny and cold inland, unless we get some trough or frontal activity pushing south - of which I'm sure there will be.

 

 

The updated 96 and 120 hrs fax charts are a one way ticket to troughs-ville.

 

96..  120..

[kold weather]

Notbad runs today, cyclonic northerlies always can produce little features at short notice and I wouldnt be shocked if that happens again here.

[The Enforcer]

Dewpointwatch update (number of GFS frames above freezing for South Midlands area between Wednesday 3pm and Sunday 9pm:

 

25/1/06z - 10

25/1/12z - 1

25/1/18z - 2

26/1/00z - 7

26/1/06z - 12

26/1/12z - 9

26/1/18z - 4

 

Have come full circle with the 18z producing the most favourable output of the day. Friday 'danger period' now focussed around the middle of the day. Saturday reduced to a small window.