Winter Model Discussion 12Z 22/1/13 onwards.

[SMU]

I think that currently this is a fair reflection of what is expected in the 10 day time frame. Only time will tell whether an amplified Azores ridge will grow into a stronger Greenland block with undercutting.

Overall we are seeing some more alignment of the MJO pattern with the forecast anomaly pattern around day 10.

http://www.cpc.ncep....clivar_wh.shtml

The average MJO forecasts take us into phase 8 at the start of February - the expected H500 anomaly here is for a northerly displaced Azores ridge and west based -ve NAO.

No true GH is forecast here but we may not need it to still get cold sourced directly over the UK. In fact the only Feb MJO H5 anomaly that showed greater raised heights in Feb is phase 3 (ECM takes us there in the extended range)

There is a lot of support for the amplified Azores ridge from the ensemble anomaly charts - both the GFS and ECM

So we will be positioned on the cold side of an Atlantic ridge as we enter Feb.

This is supported by the lower strat charts as well as can be seen from the 100hPa chart at day 10

So a cool/cold start to February with the chance of a greater northern blocking once the pattern becomes established especially if the Pacific ridge can wane allowing the Greenland ridge to develop more.

Hi Ch-

I noticed you mentioned a Sheared GH in a post earlier- that seems a good way of presenting it- a 'chunk' or wedge if you like moving away east & settling over Svalbard-

The ECM presentation at day 10 tonight lends support to this: ( ive added the jet in purple for those newer people to understand & the circle in red is the wedge of high pressure-

If we are going to get cold from the NE or East it will be born out of this- not a true GH

It does look a little transient at this stage- however they always do....

S

Edited January 27, 2013 by Steve Murr

[damianslaw]

Jaffus

Indeed it is.....and a classic 'descending' winter

BFTP

[Polar Maritime]

Yes plenty of support for this to happen up to the northerly as stated.

After that period it is a punt as stated but not a wild guess.

- Jet going south.

- Blocking to become established.

- SSW Effects to take effect.

I have said it is a punt and a punt it will remain even if it comes off as planned. I am not a forecaster & nor are you however we both have intrest in the weather the diffrence being i am trying to read between the lines and make a punt where as you are just reading the models into fi which has just as much of a chance of coming up as my forecast coming up.

Whatever will be will be & time will tell.

How on earth do you know what im doing...? Anyhow I agree the Northerly is a dead cert as forecast by the METO, I just wonder'd if you had any other reasons behind your forecast/punt eg not taking certain model's at face value, but picking up on certain small indicators that can lead to outcomes that maybe the models are slow to pick up on, which could heed to your punt.. Im well aware of the strong background signals, im just waiting for the models to pick up a stronger signal of these.

Edited January 27, 2013 by Polar Maritime

[damianslaw]

Another interesting month to look at synoptic wise is feb 05, the month started with the atlantic in charge after a Very atlantic domimated jan, however, after a couple of tame northerlies, just after mid month heights built overid atlantic and stayed there preety much for a month, we were then exposed to a Very blocked spell with easterlies and northerlies galore quote superb wintry synoptics, yet ssts were very high and the continente much milder than usual, what on papershould have been à v cold period wasnt quote so, but it was à very blocked pattern all the same, not saying we will see the same this feb, but if we did things would be much colder. It is a Good example of a v decending winter, i remember Many people were amazed to see such synoptics after a long long run of no major blocking, indeed prior to feb 05, you had to go back to dec 96.

[shotski]

Looks like good support from JMA long range ensembles for an outbreak of northern blocking

as we head into Feb.

[chiller]

Another interesting month to look at synoptic wise is feb 05, the month started with the atlantic in charge after a Very atlantic domimated jan, however, after a couple of tame northerlies, just after mid month heights built overid atlantic and stayed there preety much for a month, we were then exposed to a Very blocked spell with easterlies and northerlies galore quote superb wintry synoptics, yet ssts were very high and the continente much milder than usual, what on papershould have been à v cold period wasnt quote so, but it was à very blocked pattern all the same, not saying we will see the same this feb, but if we did things would be much colder. It is a Good example of a v decending winter, i remember Many people were amazed to see such synoptics after a long long run of no major blocking, indeed prior to feb 05, you had to go back to dec 96.

I recall that February 05 very well. There was a low that stalled right over the SE and it just kept dumping and dumping snow for hours. Was probably the biggest snowfall the SE saw since maybe 96 and what I regard as the return of decent winters following the wilderness years post 91. Sorry off topic. Hope your synopsis is right especially with colder air to draw on...

Edited January 27, 2013 by chiller

[london-snow]

How on earth do you know what im doing...? Anyhow I agree the Northerly is a dead cert as forecast by the METO, I just wonder'd if you had any other reasons behind your forecast/punt eg not taking certain model's at face value, but picking up on certain small indicators that can lead to outcomes that maybe the models are slow to pick up on, which could heed to your punt.. Im well aware of the strong background signals, im just waiting for the models to pick up a stronger signal of these.

Did not mean to come across rude to you there PM if that is what you are refering too?

Anyway those factors as stated are related to how i see things shaping up into feb and i do feel that the models will pick up more & more on this in the coming days.

It is a punt and not a statement to say that this will happen take my advice ect.

L-S

[Timmytour]

i have to admit..... the Met office approach of caution in the recent cold spell was well founded....they handed a difficult situation well and, despite the urges of many (even GP I seem to recall) didn't go over the top in their advice.

But worth reflecting for those who can't see anything in the current model output for sustained cold, that they even they, with their access to higher resolution models, can still get it wrong...(posted by tollgateiow on 21st December)

This is what the UKMO were predicting on 6th December for the period we are just entering, just about the opposite of what we are getting and about to get I would say. So hopefully their current predictions will be wrong too! I know it doesn't always work like that but you can but hope....

UK Outlook for Friday 21 Dec 2012 to Friday 4 Jan 2013:

Temperatures by both day and night are most likely to be below average during this period, with a greater incidence of overnight frost and, at times, fog or freezing fog. The signal for rain and snowfall amounts during this period shows a high degree of uncertainty, however, on balance, slightly drier conditions compared to average are favoured for most of the UK. Even though there is a drier-than-average signal for much of the UK, where precipitation does occur, there is a greater chance that it will fall as snow compared to normal.

And there was no talk of "shannon entrophy" around this time.

there's potential in the current model output....but, as ever, nothing is nailed on. And nothing, zonal, Bartlett, northerly topplers or Beast From The East, can be ruled out. which is refreshing from how things sometimes can be!

[Jason M]

Slightly better amplification at 126 on this run. Subtle and maybe wont impact the AZH steamrollering in, but positive all the same.

http://www.meteociel...&ech=126&mode=0

Jason

Edit: Nasty little low next weekend. Not good news for flood hit areas as rain will last many hours and be very heavy

Edited January 27, 2013 by Jason M

[Polar Maritime]

Did not mean to come across rude to you there PM if that is what you are refering too?

Anyway those factors as stated are related to how i see things shaping up into feb and i do feel that the models will pick up more & more on this in the coming days.

It is a punt and not a statement to say that this will happen take my advice ect.

L-S

Not at all LS! good luck with your punt ! As you say the background signals are in your favour, as with most other forecast's from the professionals, with the N/E E being favorable.

Congrats winning SM's the snow pile competition !

Edited January 27, 2013 by Polar Maritime

[chionomaniac]

With a little nudge here and there next Saturday could be quite interesting. Could be a fair amount of hill snow for Wales and the Peak District.

Edited January 27, 2013 by chionomaniac

[mulzy]

A big problem i see with any sustained cold is the Azores high - it is known as the "winter killer" for obvious reasons. I do appreciate that the AZH can be subsumed into a Scandi high or forced up towards Greenland but with heights reamining high to our south-west, sustained cold will be harder (but not impossible) to achieve. That is my BIG worry.

[Weathizard]

Not that I am one to rain on peoples parades or anything, just to add balance. For most of winter so far I personally recall seeing these high pressure anomalies quite a lot since mid-November it has been predicted and still the lesser spotted Greenland high and the elusive true Scandi heights haven't come to fruition, in fact I even remember at one point earlier this month we had the BLACK hole anomalies for a few runs for pressure over Greenland. Not to say it won't occur this time as we have the aid of the SSW effects that are probably soon to come into play but just seems a consistent trend for this winter that has not yet occured. In my personal opinion if we are to get cold in the next 10 days it will be via a Scandi high with low heights from the east rather than a Greenland block at this juncture.

ECM and GFS ens definitely showing a colder trend though, certainly the GFS looks more 'bullish' with around a -5 MEAN for most of the UK in about 10 days time.

[Jason M]

With a little nudge here and there next Saturday could be quite interesting. Could be a fair amount of hill snow for Wales and the Peak District.

Just a shame that at present there is nothing to tap into the other side of the north sea. As you say though, small changes and all that. Just a little more amplification and things can change.

Jason

[london-snow]

Not at all LS! good luck with your punt ! As you say the background signals are in your favour, as with most other forecast's from the professionals, with the N/E E being favorable.

Congrats winning SM's the snow pile competition !

I did not even know i won lol thanks for the heads up PM.

[Ice Day]

Into FI, but 228's a nice chart. Will it be a toppler or are we in for some prime FI eye candy?

[chionomaniac]

The amplification on this run is further west and will bring a better displacement north of the Azores ridge.

Even a toppler can manage a northerly from Svalbard to North Africa!

Edited January 27, 2013 by chionomaniac

[Grimsby Snow Lover]

Another GFS run and the TRENDS remain. Build of pressure towards Greenland after this week, followed by something that is not a million miles away from an E/NE later in FI.

http://www.wetterzentrale.de/pics/Rtavn3001.png

[Jason M]

Looks like a toppler pattern around the displaced AZH. Not an uncommon Feb pattern to be honest but a frustrating one as cold dry days would be interspersed with cold rain (uppers would not be cold enough as Atlantic sourced so heavily modified in lower atmosphere plus fronts from NW would have warm sectors).

Still, too far out to get overly worried. I still think that if (and big if) its coming the cold will be courtesy of Scandi high and not a GH. Trouble with these set ups is that the ensembles can tease with phantom easterlies that just get slowly dropped as time goes on.

If we got stuck into this pattern, Feb would probably come in below average but with nothing particularly notable occuring. The AZH out west would be good news for SW England though as it would help to reduce the potency of any rainfall events in the SW.

One positive is that there was slightly better amplification at days 5-7 and if this further improved tommorow things could easily look up.

Jason

Edited January 27, 2013 by Jason M

[mulzy]

Another GFS run and the TRENDS remain. Build of pressure towards Greenland after this week, followed by something that is not a million miles away from an E/NE later in FI.

http://www.wetterzen...s/Rtavn3001.png

Agree about trends but I wouldn't classify that as a good chart for sustained cold - Azores High too much of an influence.

One thing coming out of today's runs is the dominance of the (displaced) Azores High - not great to be honest. In my opinion, we've taken a step backwards today.

Edited January 27, 2013 by mulzy

[Weathizard]

Agree about trends but I wouldn't classify that as a good chart for sustained cold - Azores High too much of an influence.

One thing coming out of today's runs is the dominance of the (displaced) Azores High - not great to be honest. In my opinion, we've taken a step backwards today.

Isn't a displaced Azores high normally a key ingredient of high lattitude blocking? Not a bad thing if we want a Greenland/Scandi block to my eyes, just need that vortex over Canada to weaken enough, that's been the killer for Greenie heights this winter

[Jason M]

Agree about trends but I wouldn't classify that as a good chart for sustained cold - Azores High too much of an influence.

One thing coming out of today's runs is the dominance of the (displaced) Azores High - not great to be honest. In my opinion, we've taken a step backwards today.

I'd agree with that. I personally don't like to see the AZH displaced like this as its not usually good news. The AZH can ridge up towards Greenland but rather than ridging, were seeing a closed high in the mid atlantic. In effect its just like a pebble in a river with the rTM air alternating with PM air across the top of the high. Its a quasi zonal set up tbh.

A GH looks as far away tonight as it has all winter.

Jason

Edit: Might not happen that way though as still a long way out :-)

Edited January 27, 2013 by Jason M

[bluearmy]

Agree about trends but I wouldn't classify that as a good chart for sustained cold - Azores High too much of an influence.

One thing coming out of today's runs is the dominance of the (displaced) Azores High - not great to be honest. In my opinion, we've taken a step backwards today.

Depends if you're only watching the ops in low res?

naefs looks good to me and the ecm day 10 mean anomolys show the atlantic may have a tough time just riding through in week 2.

And just for good measure

http://www.meteo24.fr/fr/home/meteo-france-et-europe/passion-meteo/ensemble-de-previsions.html?eps=london

Not wall to wall countrywide snowcover (yet) but not a bad mean at two weeks out !

Edited January 27, 2013 by bluearmy

[Cloud 10]

Depends if you're only watching the ops in low res?

naefs looks good to me and the ecm day 10 mean anomolys show the atlantic may have a tough time just riding through in week 2.

And just for good measure

http://www.meteo24.f...html?eps=london

Not wall to wall countrywide snowcover (yet) but not a bad mean at two weeks out !

Yes BA,a nice heart shaped anomaly in the atlantic at day 10,hopefully it will show

some love for Greenland as we head towards valentines day!

[LomondSnowstorm]

I'm not entirely sure how people envisage a high latitude block setting up other than through the northward ridging of a mid latitude high. The problem for me is entirely not with the Azores high, but rather the low heights to the northwest which is stopping it from retrogressing towards Greenland. The northward ridging of the Azores high fits nicely with the currently MJO state and also to an extent fits with the stratospheric vortex placement and both of these would suggest that there is a decent shot that at some point we'll get the amplification upstream needed to establish a proper high latitude block. In the meantime, a few Pm shots from the northwest is an entirely welcome development compared to some of the milder runs we were seeing just a few days ago.