Model Output Discussion

[Tom D]

Looking at the GFS Ens from this morning (With my Data Analyst hat on - which is what I do for a living) There is something seriously wrong with the OP run around 5th Feb. Either missing data or corrupt data, as shown by the big decline then subsequent sharp rise in such a short timeframe. This then goes on to effect the outcome in the mid term, as you would expect if something is not right earlier on in the run.

You can clearly see its a massive mildy outlier in the mid term and in my opinion bin it.

There is something wrong with it looking through ensembles around Europe...

In Athens 2m temps it's a massive cold outlier.

In Oslo 2m temps it's a mild outlier.

In Kiev air pressure it goes highest and lowest (above 1050mb then down to about 994mb in the space of 2 days between 7-10 Feb)

This is similar for Moscow.

[chionomaniac]

Not sure how long it would last though Ed.

Using the mid-December pattern as a blueprint, that went on for some 10 - 12 days in the south, longer in the north. It threatend to be a west based -NAO but height rises back towards Iceland helped sustain the pattern.

Synoptically, west based -NAO are more likely in February during Ninos and the wavelengths may not necessarily favour the same evolution or extent of the December event. The challange in front of us though are how will further warmings in the stratosphere manifest themselves ? I suspect that we will feature a substantive blocking structure over the Canadian Arctic throughout Febraury into March.

My thoughts are that the current forecast positioning of the displaced stratospheric vortex may delay the blocking pattern somewhat though, which would leave us with a slightly longer shot of cold. If we can get a good cold pool in position and have a slow transition to the west based -NAO then that could lead to more fun and games in the meantime for possibly the mid third of Feb.

Edited January 29, 2010 by chionomaniac

[Bobby]

ECM bit of a cold outlier... little worrying.

[TEITS]

Quick word about the ensembles.

Do not feel comforted just because the OP is an outlier. I have known occasions when the OP is correct but the ensembles take a few runs to trend the same. Also bitterly cold upper temps do not always mean a good thing. Any runs showing -17/-18C are more likely to come from a SE,ly flow. So you could say a NE,ly with upper temps of -10C is much better wrt to snow than a SE,ly with upper temps of -18C. However NE England/E Scotland would do well.

Could do with a decent set of 12Zs to raise my confidence once again. I will add that the pattern I often notice is these situations is this. At +240 we see Feb 1947 synoptics but then around +144/+168 we see downgrades. However around +72 we then see upgrades. So if the current +144/+168 charts remain the same at +72 then I would expect the block to be further W than progged with SWs being less influencial.

[swilliam]

ECM bit of a cold outlier... little worrying.

Yes a definite shift to many more mildsolutions. The GEFS ensembles are interesting in that they are split into two groups.

Between 3-6 feb there are a group of cold solutions - presmably due the early start of an Easterly - and a group of milder ones - probaly indicative of a S/SW flow. Then again between 7-11 Feb there a group of v.cold solutions and some not so cold. Interstingly I think I can only see one that at no stage bring v.cold air in.

Edited January 29, 2010 by swilliam

[La Bise]

Wasn't there such a pattern for the last two spells, with early signs of cold/snow then steady downgrades all the way before the whole setup coming back into frame?

I'm finding it quite hard to follow the thread at the moment, with believers and sceptics trending (ah!) more and more towards their interepretations to the detriment of a dispassionate analysis of the facts. What would be the worse case scenario for the next 5-10 days - slack continental flow?

[TEITS]

What would be the worse case scenario for the next 5-10 days - slack continental flow?

Probably yes.

Despite the disagreement the one common pattern amongst most of the models is blocking to be influencial. As you can see on the link below the SLP mean for Cambs is at 1030mb.

http://charts.netweather.tv/ensimages/ens.20100129/06/prmslCambridgeshire.png

Great to see the Met O disregard the UKMO and back the ECM on the latest forecast.

[Frosty.]

Wasn't there such a pattern for the last two spells, with early signs of cold/snow then steady downgrades all the way before the whole setup coming back into frame?

I'm finding it quite hard to follow the thread at the moment, with believers and sceptics trending (ah!) more and more towards their interepretations to the detriment of a dispassionate analysis of the facts. What would be the worse case scenario for the next 5-10 days - slack continental flow?

There are very conflicting signals from the models at the moment but I am now beginning to think the chances of an Easterly are beginning to fade as pressure eventually falls in the iceland area and high pressure slips south leading to mild sw'ly winds beyond the next week.

[La Bise]

Far worse scenarios we could be in I'd say then plus I suspect sporadic incursions of deep cold are possible, obviously for favoured areas in SE/E.

Edit: The slack flow scenario, not the bloody SW muck...

Edited January 29, 2010 by La Bise

[Frosty.]

Great to see the Met O disregard the UKMO and back the ECM on the latest forecast.

Are they using today's data though or yesterday's, very confusing.

[BLAST FROM THE PAST]

Synoptically, west based -NAO are more likely in February during Ninos and the wavelengths may not necessarily favour the same evolution or extent of the December event.

A good point Stew BUT...this winter has not done as the Nino has told it...and why should it now? I think a shot close to Dec set up is very much on the cards, if not more robust longterm.

BFTP

This reads like the ECM 00Z is showing, very good.

UK Outlook for Wednesday 3 Feb 2010 to Friday 12 Feb 2010:

Generally cold with overnight frost and ice through much of the period, but a good deal of dry and bright weather for many parts of the UK by day. However, cloud and rain, and some hill snow is likely to affect many central parts at first on Wednesday, but it should become mostly dry later on Wednesday and during Thursday. Wintry showers near the east coast are likely to spread further inland towards the end of the week as winds become more easterly. The mainly dry weather with some frost and ice, is likely to continue for much of the rest of the period, with temperatures mostly below normal. However, wintry showers or more persistent sleet or snow could affect eastern and southern areas later in the period.

Updated: 1213 on Fri 29 Jan 2010

Edited January 29, 2010 by BLAST FROM THE PAST

[La Bise]

MO use 0z data as per query by a member direct to them but another member has an insider there who says they use 12z data...

[BLAST FROM THE PAST]

There are very conflicting signals from the models at the moment but I am now beginning to think the chances of an Easterly are beginning to fade as pressure eventually falls in the iceland area and high pressure slips south leading to mild sw'ly winds beyond the next week.

Sorry Karl, I think you are not reading the picture but getting sucked into individual runs.

BFTP

[Frosty.]

MO use 0z data as per query by a member direct to them but another member has an insider there who says they use 12z data...

Not according to Paul B, but thanks for the reply. It will be very interesting to see which way this goes. Anyway, according to the models it will be cold until wed/thurs next week at least.

Sorry Karl, I think you are not reading the picture but getting sucked into individual runs.

BFTP

Hi Fred,

The models seem more confused than they did yesterday which is why I am edging towards a milder outlook but I have the greatest respect for your methods and forecasting skills so I hope you are right.

[BLAST FROM THE PAST]

Not according to Paul B, but thanks for the reply. It will be very interesting to see which way this goes. Anyway, according to the models it will be cold until wed/thurs next week at least.

Hi Fred,

The models seem more confused than they did yesterday which is why I am edging towards a milder outlook but I have the greatest respect for your methods and forecasting skills so I hope you are right.

Karl

For the moment forget my method and lets look at the models. Last weekend they didn't show the cold evolution then on Tues they jumped on board, then pulled away [then GFS fancied it] and then look at 00z ECM this morning...that is, IMO, significant. It has happened ALL winter with models umming and arhhing and then hey presto. The Meto 6-15 day outlook reads just like the ECM and no model no matter how hard it tries NEVER gets the Atlantic to push through. Indeed overall it is all backing west. Its still is confsing because next week is FI....so much going on across the pond to deal with yet.

Now on my method the signal is that energy in Feb will not push north BUT MAINLY south or some up west side of Greenland.

BFTP

[Glacier Point]

A good point Stew BUT...this winter has not done as the Nino has told it...and why should it now? I think a shot close to Dec set up is very much on the cards, if not more robust longterm.

Updated: 1213 on Fri 29 Jan 2010

Arguably Fred we have followed a west-based Nino pattern.

http://www.netweather.tv/index.cgi?action=other;type=winterbulletin;sess=

Here are the composite reanalysis for Nino 4 correlation and west-based El Ninos during February:

What they very clearly depict are an absence of positive heights to our east and block centred towards Greenland / Canada.

Just how much ridging we get from the south will determine I think the modification of colder airmass situated over Europe.

[BLAST FROM THE PAST]

Arguably Fred we have followed a west-based Nino pattern.

http://www.netweather.tv/index.cgi?action=other;type=winterbulletin;sess=

Here are the composite reanalysis for Nino 4 correlation and west-based El Ninos during February:

What they very clearly depict are an absence of positive heights to our east and block centred towards Greenland / Canada.

Just how much ridging we get from the south will determine I think the modification of colder airmass situated over Europe.

Hi Stew

thanks for that. I fully agree that blocking is to develop to NW and will control our weather, and as you are showing that is West Based Nino composite. I also think that it won't be too far west until after mid Feb at earliest. Has the first 2/3rds of winter been west based nino correlated? I seem to remember that wasn't the case and so am wondering if this next episode will be coincidence as regards to Nino, and if not why it is now looking to drive the set up when previously it couldn't.

regards

Fred

Edited January 29, 2010 by BLAST FROM THE PAST

[Lewis]

Another reason why i like looking in reliable time frame/ short term.

Polar low here; (Now that is something in RT)

Edited January 29, 2010 by Storm Force Lewis

[Glacier Point]

Hi Stew

thanks for that. I fully agree that blocking is to develop to NW and will control our weather, and as you are showing that is West Based Nino composite. I also think that it won't be too far west until after mid Feb at earliest. Has the first 2/3rds of winter been west based nino correlated? I seem to remember that wasn't the case and so am wondering if this next episode will be coincidence as regards to Nino, and if not why it is now looking to drive the set up when previously it couldn't.

regards

Fred

West-based Ninos Dec - Jan:

Winter so far:

I think there's good correlation there in terms of Pacific and Atlantic wavelengths.

Our second westerly wind burst of the winter is now well underway which will enhance the Nino signal to the atmopshere. This wind burst is centred around the Dateline and the latest OLR plots suggest eastward motion in the convective centre driving an MJO phase 7/8 transition.

Composite reanalysis for convection located in these areas:

Again another forcing for the high latitude block to migrate towards Canada / Greenland.

Edited January 29, 2010 by Glacier Point

[Iceni]

Another reason why i like looking in reliable time frame/ short term.

Polar low here; (Now that is something in RT)

Well spotted — she's there alright. I know they're short-lived, will it make it down to EA?

[Lewis]

Well spotted — she's there alright. I know they're short-lived, will it make it down to EA?

Thats the same question i'm asking myself lol.

If it makes it's way South some areas are inline for a fun afternoon/evening.

[Duane S.]

Slightly improved NAO forecasts.

MJO excites me the most with some considerable stalling looking likely around phases 7 and 8.

Still looking odds on for a continental feed (of some desription) from around next weekend IMO. Increasing signs of blocking to the NW later on and with that Siberian block likely to try and muscle Westwards, could we get goalside of a much fabled link up in about 10 days time?? Not beyond the realms of possibilities, if unlikey by its very nature.

[cooling climate]

No Dave it hasn't, but the models reading of it and the range at which they can be relied upon has not changed.

Further more, I think its wise to remember that just because 47 style synoptics don't show their hand every run that's not a reason to throw in the towel. It rather seems at the moment that no matter what changes occur in the early evolution, we still manage to get there in the end. I would say that in itself, that's a pretty unusual thing to see, particularly over so many runs on different models.

Very much agree with this. It is the same as what I was talking about yesterday the MMW, downward propagating

easterlies, Siberian high are dictating the pattern, this is all moving in a westerly direction and no matter what

the models throw up the pattern is still a very cold and wintry one.

I still believe we will see a east of north airflow embedded over the country by the end of next weekend

with bitterly cold weather to follow.

[Yeti]

Slightly improved NAO forecasts.

MJO excites me the most with some considerable stalling looking likely around phases 7 and 8.

Still looking odds on for a continental feed (of some desription) from around next weekend IMO. Increasing signs of blocking to the NW later on and with that Siberian block likely to try and muscle Westwards, could we get goalside of a much fabled link up in about 10 days time?? Not beyond the realms of possibilities, if unlikey by its very nature.

Yes the NAO is forecast to go slightly negative but perhaps we shouldn't worry too much about just how negative it actually goes:

http://www.wetterzentrale.de/pics/Recm1441.gif

If you look at the ECM - so far the best of the models today - the NAO is only slightly negative, with the Azores high not displaced very much and the block more E based than GL based. A strongly -ve NAO will be recorded when there is a large GL block forcing low pressure over the Azores. But this setup, as we know, isn't necessary to produce long, deep cold...

[kold weather]

The easterly suddenly does look a lot more fragile again, I remember the very cold runs for mid Feb last year got un-done by something very similar to what the UKMO is prediciting. However there is a huge signal for blocking to develop around the Greenland region onthe models, that sort of large signal is not the type that should be ignored and more ofen then not it'll come off in one form or another its just the exacts that are uncertain.

What I said yesterday still stands, the milder air IMO will get across most of Britian however cold air is going to win out making any milder blip just that, a milder blip!