Model Output Discussion 1200 hrs 30/09/14

[Hocus Pocus]

As others have said regardless of the duration of the potential Northerly it's still a pattern change  to something more seasonal. Longer term the building blocks are slowly locking into place for something more interesting down the line but I feel that November will come in around average with neither mild or cold being able to dominate one particular pattern.

[Man With Beard]

The big thing for me, though, is yet again the PV is getting nowhere on almost any models in terms of proper organisation. Is this a precursor to a negative AO this coming month? The models I assume have an inbuilt bias to build the PV at this time of year, and so if they are now failing to get it organised even in FI, does that suggest that it will fail to get a grip at all next month - and leaving lower latitudes such as the UK vulnerable to northerly outbreaks, or periods of HLB, if the gaps in the PV work themselves in our favour?

[Stormyking]

Here we go then with the 18z starting to roll out, hopefully the trend will still be there for the Northerly and cooler conditions

[johnholmes]

The big thing for me, though, is yet again the PV is getting nowhere on almost any models in terms of proper organisation. Is this a precursor to a negative AO this coming month? The models I assume have an inbuilt bias to build the PV at this time of year, and so if they are now failing to get it organised even in FI, does that suggest that it will fail to get a grip at all next month - and leaving lower latitudes such as the UK vulnerable to northerly outbreaks, or periods of HLB, if the gaps in the PV work themselves in our favour?

 

Can we get one thing clear about synoptic models, be it GFS, ECMWF or UK. There is NO bias. Each model starts with the T+00 data and runs according to the programmes using the laws of thermodynamics out to the end. There is no bias fed into any run at synoptic level.

 

link to Met O info re their computer models.

I stand corrected if anyone does find text that shows their model has any bias in the sense of the post from rjbw

http://www.metoffice.gov.uk/research/modelling-systems/unified-model

Edited October 29, 2014 by johnholmes

[Altohumorous]

If that northerly comes off at all it's certainly a pattern change. A weak toppler looked the only possibility, this would be (though short-lived) more of a real deal, and could also herald the potential for more. Even the fact that the trough and tropical air coming out of the NE States/Canada slows down and fills is a pattern change, along with the actual incursion from the Arctic, and the way the trough over the NE Atlantic/Scandi heads/extends south to drag that incursion down and sustain it as far as it does.

Oscillation shift of the Jet also happens. Cooler or possibly colder maritime & still meridional pattern looks possible beyond the fairly reliable timeframe.

[johnholmes]

The 500mb anomaly charts all favour a more westerly and somewhat less mild pattern, fairly unsettled much of the time with just quite brief interludes with surface high pressure the dominant feature.

 

links

NOAA

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

 

ECMWF-GFS

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

Edited October 29, 2014 by johnholmes

[Captain Shortwave]

Whilst we will probably see some rather chilly air descend from the Arctic, it will likely get watered down as the trough becomes squashed between the Azores and Euro high pressure cells. I suspect the likely result beyond this will be a westerly flow with near average temperatures. Higher heights probably establishing over Western Russian/Eastern Europe. Nothing out of the ordinary really, though a couple of widespread night time frosts could be on the cards next week.

[Mucka]

The 500mb anomaly charts all favour a more westerly and somewhat less mild pattern, fairly unsettled much of the time with just quite brief interludes with surface high pressure the dominant feature.

 

links

NOAA

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

 

ECMWF-GFS

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

 

But they both support something I mentioned earlier. troughing into central Europe which should be helpful in building pressure to the E/NE of the UK. ECM doesn't really go for this but the GFS anomaly chart does show heights getting into that region which of course could result in a Scandi high, especially if the jet splits or rides under.

If the jet just rides over the top I still expect things to be quieter for the UK with LP being pushed further North with time but we will see and it will be worth seeing if the ECM anomaly charts move toward GFS or vice versa.

 

Still we are looking out toward mid month for any real potential blocking that might bring colder air to the UK.

Edited October 29, 2014 by Mucka

[knocker]

Some simple thoughts on the two or three weeks.

 

Essentially the basic change is the jet moving a little south and the PV becoming more active leading to a cooler more active Atlantic. Bur it is indeed possible with the jet being blocked by increasing heights to the east ( there is a large warm temp anomaly in eastern Europe) That the HP will spread east. Of course this down the line a tad. The ECM is suggesting this route and the GEFS is tagging along.

Edited October 29, 2014 by knocker

[Man With Beard]

Can we get one thing clear about synoptic models, be it GFS, ECMWF or UK. There is NO bias. Each model starts with the T+00 data and runs according to the programmes using the laws of thermodynamics out to the end. There is no bias fed into any run at synoptic level.

link to Met O info re their computer models.

I stand corrected if anyone does find text that shows their model has any bias in the sense of the post from rjbw

http://www.metoffice.gov.uk/research/modelling-systems/unified-model

Perhaps I've - incorrectly - taken some quotes on here as gospel - but I do remember in June a chap on here claiming - convincingly - met office connections (I'll try and dig it out) - and he/she stated the UKMO had a bias to destroy blocks over the UK as per the climatic norm? Since then, I've been convinced that models are programmed to some extent to follow the climatic norm (which is what I mean by bias)

Edit: here it is, Mark Canning MOD thread in June:

"...Not sure if common knowledge or

not...but GM ( UKMO) breaks

down blocks faster than it should

as a function of the statistics

that output the verification

index..so in short, more often than not, it gets it

right, as more often than not, HP does not

dominate and GM pushes us back into a zonal

pattern consistent with climatological mean.

(the model looks better, scores higher, we get it

right most of the time). So, if GM keeps block

for a long time, this is quite interesting as it is

going against its internal revert..."

Edited October 29, 2014 by rjbw

[nick sussex]

Still not convinced any of the models can be trusted as that low in the ne USA is still difficult to forecast accurately.

 

The GFS 18hrs run deepens this later than the earlier 12hrs and for a moment looked like it was going to push everything east, the GFS P looks similar to the earlier 12hrs.

 

The models still toying with a pressure rise to the east, you'll see when looking at the NH charts that the PV wants to send a chunk west near the pole this then is likely to try and feed the Atlantic trough.

 

Good points if you're in the cold camp is that the models are still not relishing sticking one foreboding PV to the north, at this time of year the PV is desperate to set up there and the longer we see the PV splitting the better.

 

So going forward a chance of a cold snap but nothing out of the ordinary at present, the ridge near Iceland then toppling towards Scandi, its likely then the Atlantic troughing will try and edge in towards the UK.

 

After that it could be a stalemate for a while but keep an eye on the gap near Svalbard incase the GFS 18hrs is onto the right trend by sending the PV chunk westwards and then splitting this. Bearing in mind that originally the models had a flatter pattern upstream before the ECM developed that amplification near the eastern USA which in turn is the catalyst for the possible cold snap.

 

Before then however if you're looking for that cold snap to verify hope for a earlier deepening of that USA low and more of an inland track, this does help increase the margin for error and likely to develop a better ridge near Iceland.

[Yarmy]

Of course the detail will be all wrong, but the vortex on the 18z is...well...see for yourselves:

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=288&mode=0&runpara=1&carte=1

[SMU]

HI John.

 

Theres so much bias on the GFS theres actually a whole page for it in the model suite.

 

http://www.hpc.ncep.noaa.gov/mdlbias/

 

Also in reference to your post, All models will have a starting platform & somewhere deep in the mix will be the long term mean & part of the build in terms of what the broad pattern characteristic will look like.

If the starting patter was the total INVERSE of what the characteristic should be - ALL models would mute out the signal over time to return to that normal base state- Time X

The GFS due to its eastward bias resets the pattern a lot quicker than the euros hence its hopeless in extended blocking scenarios..

S

Edited October 29, 2014 by Steve Murr

[Duane S.]

Never mind the details, this is what we want to see happen. A propensisty to drop energy down through us into Europe via a NW - SE jet to our W. If this is a sign of things to come this winter, it's going to be a good one!

 

Edited October 29, 2014 by s4lancia

[knocker]

Still not convinced any of the models can be trusted as that low in the ne USA is still difficult to forecast accurately.

 

 

Main Maine snow band moved east with ECMWF 12z ... blend of GFS and EC for past couple days ... cold behind front will feel winter like

[summer blizzard]

Interesting output for the Arctic but for the UK it looks like standard Autumn to me with a cold front bringing our first real shot of winter on Monday before a continuation of the westerly regime.

 

[A.J]

a  friendly reminder to stay on topic.....met office forecasts, whilst interesting, are not model output related discussions I'm afraid

[knocker]

Very much an Atlantic dominated run from the GFS this morning with very unsettled weather next week with much cooler temps but with a cold snip.

Edited October 30, 2014 by knocker

[Polar Maritime]

Morning all, Yes Knock a much cooler/wetter flow than of late from the W/N/W after the initial Northerly next week.

 

Edited October 30, 2014 by Polar Maritime

[Captain Shortwave]

Looks like a very ordinary spell of weather for the time of year. The models are struggling to get anything remotely cold into the UK from this northerly, 850s of -1/2 looks about the best we can do and the south never drops below 0. Beyond that the Atlantic looks very much like taking control of the weather with showers and longer spells of rain at times.

Temperatures after a brief cool blip look like returning to near normal levels.

The GEM again looks the most out of kilter with the rest of the suite with a very unsettled mid-range before building high pressure in later. Again the ECM/GFS solution looks more likely.

[johnholmes]

re comments about bias if mod/admin will allow, to clear this up I will e mail UK Met and ask; maybe someone might like to do the same with ECMWF and GFS?

Edited October 30, 2014 by johnholmes

[mushymanrob]

It is indeed a major pattern change given the warm synoptics for weeks now,,,,

 

sir, i dont call a few hours of cold a pattern change, because it doesnt herald a new pattern of recurring northerlies.... according to current outputs. yes it might be cooler overall, but the pattern is still unsettled recurring run of atlantic driven low pressure, thats the pattern, the temps are irrelevant.

anyway its all acadaemic now as this mornings models have dropped the severity of the potential cold snap.

[ANYWEATHER]

It is indeed a major pattern change given the warm synoptics for weeks now,,,,

Well, here we are again , models have watered any real cold for next week into virtually nothing now, which is not surprising! Looks like it will still be cold enough at times though for some wintry stuff on the highest mountains in Scotland......

sir, i dont call a few hours of cold a pattern change, because it doesnt herald a new pattern of recurring northerlies.... according to current outputs. yes it might be cooler overall, but the pattern is still unsettled recurring run of atlantic driven low pressure, thats the pattern, the temps are irrelevant.

anyway its all acadaemic now as this mornings models have dropped the severity of the potential cold snap.

Yes indeed!

[Frosty.]

850's dropping from +10 / 12 down to 0 / -2 or 3 would still be a welcome change from the persistent mild mush..winter is still a month away and this is still an evolving situation, the trend is turning colder.

[Severe Siberian icy blast]

When the models are predicting a northerly in 7 days time as they have been , the first thing that stood out clearly to me was the fact that as it gets closer the northerly will dwindle out to nothing , and this mooring it's began that process, it's very early in the season and although not impossible , it's unlikely to get 850's down to -5 during early November . Especially a glancing 24/36hr northerly , so to me 850's at around 0/-1 seem much more likely next wk with temperatures during the day at 6/7's in the north and 9/10's in the south .
 

Edited October 30, 2014 by Polar Maritime
To remove off topic reverences.