Model Output Discussion - 31/10/2014 and Beyond

[BLAST FROM THE PAST]

As folk know I'm anticipating a big cold switch backend of this month leading to an early winter outbreak with December bringing at times early cold and snow.  Watching the models as we go, anyone else get the feeling that the hemisphere is beginning to load itself up?

 

 

BFTP

[Nick F]

This is often pointed out at this time of the year but you need to treat pressure modelling over Greenland with a pinch of salt, there are problems, something to do with the height of the plateau? It may show a 1060mb high but you can tell by that chart that the model has exaggerated the prediction.

 

Yes, the NWP pressure modelling over much of Greenland interior, which is high plateau, is essentially ficticous as the pressure is basically an estimation of what it would be at sea level, rather than 1000s of feet on top of the plateau - hence the sometimes rather high pressure shown by models. Models will often try to reduce pressure to sea level from, in this case, the top a high plateau, be calculating the isothermal temperature between SL and the higher level. Though the estimation often looks rather exagerated!

 

A 1060mb high at sea level is not necesarily a blocking high either, as you need to look at the upper pattern too, the 500mb height may show low heights above the surface high - which is not indicative of a blocking high, as pressure/heights need to be high stacked through all levels of the troposphere. Though in the case of the charts posted, there is a 500mb ridge over Greenland - which would infer some blocking or slowing of lows trying to move out of NE N America.

Edited November 2, 2014 by Nick F

[SMU]

GFS is up & running -  I suspect there will be a considerable swing to the ECM / -AO on this run.....

[Hocus Pocus]

A quick question regarding the GFS and ECM, would the consensus be that the ECMF has the better handle on Greenland or as I thought the GFS?

[phil nw.]

An off topic post has been removed.

Just a reminder to keep to model discussion in here please.

Thanks all.

[Barry12]

GFS is up & running -  I suspect there will be a considerable swing to the ECM / -AO on this run.....

 

The GFS looks more like the ECM at 120

 

 

and at 144

 

Edited November 2, 2014 by Barry95

[knocker]

A pretty good agreement at T336 between NOAA, ECM and GEFs considering. The jet still just south of the UK with a pretty slack Atlantic I'm feeling a little underwhelmed.

 

[johnholmes]

How you can call the NOAA chart a 'pretty slack' flow is not apparent to me mate?

Strong flow with anticylconic curvature across the Atlantic into a diffluent trough in the UK area. Ripe conditions for unsettled weather in that time scale with the probability of at least one severe gale in western/northern areas at least.

[knocker]

How you can call the NOAA chart a 'pretty slack' flow is not apparent to me mate?

Strong flow with anticylconic curvature across the Atlantic into a diffluent trough in the UK area. Ripe conditions for unsettled weather in that time scale with the probability of at least one severe gale in western/northern areas at least.

 

True enough, badly put as I was actually referring to the surface but even then, as you say, inappropriate.

Edited November 2, 2014 by knocker

[summer blizzard]

Core anomaly still too far south in Scandinavia to allow a proper undercut however GFS tries even inside the high resolution. 

 

Come winter you'd want a smaller warm sector but it could work out well.

 

[johnholmes]

True enough, badly put as I was actually referring to the surface but even then, as you say, inappropriate.

that chart is interesting with the amount of surface highish pressure across much of the chart. I wonder what the avergae one for early November looks like?

[knocker]

that chart is interesting with the amount of surface highish pressure across much of the chart. I wonder what the avergae one for early November looks like?

 

Indeed so I'm wondering what the ECM monthly update will come up with tomorrow.

[SMU]

True enough, badly put as I was actually referring to the surface but even then, as you say, inappropriate.

 

Hi knocker.

 

You have posted the day 14 ECM ensemble Mean of the jet.

 

That's the 14th day of 50 ensembles run.

 

This is the spaghetti plot for 20 GFs runs at the same timeframe.

http://www.wetterzentrale.de/pics/Rz50014.gif

 

posting the ECM with 50 is about as underwhelming / pointless as it gets.  Not quite sure what you are searching for, as any anomaly will have been muted out anyway. All you will get is an ordinary jet pattern.

 

S

[chionomaniac]

Hi knocker.

 

You have posted the day 14 ECM ensemble Mean of the jet.

 

That's the 14th day of 50 ensembles run.

 

This is the spaghetti plot for 20 GFs runs at the same timeframe.

http://www.wetterzentrale.de/pics/Rz50014.gif

 

posting the ECM with 50 is about as underwhelming / pointless as it gets.  Not quite sure what you are searching for, as any anomaly will have been muted out anyway. All you will get is an ordinary jet pattern.

 

S

Hey - It's not entirely useless Steve!

 

If you look carefully then it is quite apparent where the blocks are situated, and considering that this is at day 14, then one has to feel that this is a pretty strong signal that the 50 ensembles have picked up.....

 

[SMU]

Its to far away to show the polar high - & also to obscure to resolve the shortwave pattern.

 

A little more amplitude In the jet across the atlantic & the whole pattern changes.

 

its of minimal use.

[IDO]

Its to far away to show the polar high - & also to obscure to resolve the shortwave pattern.

 

A little more amplitude In the jet across the atlantic & the whole pattern changes.

 

its of minimal use.

Quite the opposite, I believe that after around D8 the Means are the only sensible way to look at the longer range. This is backed up by verification stats, around 50% better in nailing the variables. Of course you should just use means for patterns and trends at that range but they are quite helpful. GFS continues to play down height rises to the north and it will be interesting when ECM gets into its more reliable seven day frame if those heights keep showing up.

[bluearmy]

Interesting chat - I would use the ens mean to back up my feelings as to where the general 'certainties ' might be beyond week 1. The ops are pretty useless post week 1 unless they are showing consistency across several models. where one op model shows consistency against the others and the ens mean, then that presents a problem for us.

[knocker]

My position on this is much along the lines of ido's post so I'll just leave it at that. In the less controversial time frame of T192 the ECM is not showing high heights over Greenland. HP north of Alaska, Scandinavia and western Atlantic with troughs Greenland stretching down into Europe and a low N. America.

The jet whizzes around this and then sets off for Morocco as mentioned by Nick yesterday resulting in developments in the eastern Atlantic such as troughing over the UK. Looking at the surface analysis the UK is in the middle of a pincer movement from the HP. Needless to say the GEFs. is not quite in agreement with this so the ECM ens is awaited.

Edited November 3, 2014 by knocker

[Purga]

Remarkably mild conditions for all of Europe throughout the whole ECM run this morning

The airmass is being sourced from way south over the North African desert.

I would imagine there will be some warmth records in line to be broken if this verifies, not what many would want but noteworthy nontheless.

Edited November 3, 2014 by Purga

[johnholmes]

We each have our favoured way of describing how the models are portraying how the weather will pan out. Provided each poster shows the charts to back up their suggestions I see no problem. Each must accept the other method and simply move on, no need for any digs at someone for what they are using.

I stick to the anomaly charts for beyond 5 days, my preference, not everyones' cup of tea but to me they give in 7 or 8 times out of 10 a decent idea of what is and what is not possible.

The latest ECMWF-GFS output is fairly solid in its upper air pattern, it fits the 6-10 NOAA from last evening. They have not been entirely consistent for sure whilst NOAA has but with all 3 suggesting similar patterns and even suggesting similar anomalies the upper air pattern 6-10 possibly out to 15 days looks reasonably secure as shown in the charts below.

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

 

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

Edited November 3, 2014 by johnholmes

[bluearmy]

Not sure it's something I dont want to see purga. Rather depends how far north this warm air can get. The set up in western Europe through the first half nov holds no wintry promise anyway. The building blocks are being built and Transportation of warmer uppers into the Arctic is one of them. If this warm air just rotates around a euro block and gets no further north than S Scandi then it's probably doing no good. A look back a few years will show a sustained period where the Atlantic trough striking the sceuro ridge threw warm uppers towards Svalbard - I recall that was a more than decent winter which followed for coldies.

[MR EXTREMES]

Remarkably mild conditions for all of Europe throughout the whole ECM run this morning

The airmass is being sourced from way south over the North African desert.

I would imagine there will be some warmth records in line to be broken if this verifies, not what many would want but noteworthy nontheless.

So we see that the flip flop model outputs have started but that don't matter keep your eyes on the northern hemisphere go to 144 hours the same as the ukmo limits,

And the ukmo is showing the wedge of heights from Scandinavia building into Iceland towards Greenland.

It's not likely this will sustain but it's a repeated pattern likely this November I'm sure.

Go to 144hrs and you can second guess after this time period were we are heading.

Nothing wrong with the outputs today as November 09 was wet and windy also.

I'm not at all concerned the models show pretty average November snow at times on the Scottish mountains in the more closer time frame possible sleet at lower levels in the north with snow fall very likely higher up.

Still very interesting very normal November weather forget deep freeze for this month not likely although possible but December looking a better possibility so far.

Vortex what vortex

[Yarmy]

Is Meteociel down at the moment?

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY MONDAY NOVEMBER 3RD 2014.

NEXT UPDATE TUESDAY NOVEMBER 4TH 08:00

THE CURRENT GENERAL SITUATION. A complex Low pressure will cover Northern areas filling slowly later with a cyclonic and unstable airflow covering all of the UK.

MODELS-2 WEEK HEADLINE  Generally unsettled and rather windy at times with rain or showers. Temperatures look like staying generally quite close to average though it will feel rather chilly at times.

THE JET STREAM ENSEMBLE FORECAST The GFS Jet Stream Ensemble forecats suggests the flow runs to the South of the UK for much of the next few weeks as a trough associated with Low pressure over or to the NW of the UK prevents it moving North at our latitude and longitude.

GFS Today's operational run shows Low pressure never far from the UK over the coming few weeks with the biggest feature being it's stalling nature over the UK having arrived from the NW. This is due to higher pressure than of late over Northern latitudes steering the Jet flow down to the South of the UK and making the UK fall on the cold side of the flow and keeping unsettled conditions with rain and strong winds at times and cold enough for some snow on Northern high ground and occasional incidences of frost and fog almost anywhere in the quieter and clearer overnight periods experienced at times.

THE GFS ENSEMBLES.  The GFS Ensembles today maintain Low pressure in control of the weather over the next few weeks, generally with a central position to the NW of the UK and the UK lying under a trough from it. This means unsettled weather with rain at times and average temperatures as a result look the most likely outcome over the period with fog and frost probelems minimalistic overall but possible given any clear night skies and light winds.

UKMO. UKMO today shows a deep depression just to the NW of the UK later this week which sinks slowly South to the West over the weekend as it fills slowly. This maintains an unsettled period of weather with rain and showers at times in sometimes windy weather with temperatures generally not far from average.

THE FAX CHARTS  The Fax Charts are fairly supportive of the raw data charts again this morning with the current Low pressure filling and moving away East midweek to be followed by a deep Low in the North Atlantic pushing troughs steadily East in time for the weekend.

GEM  GEM today follows a similar route to other models this week moving forward to take the Low to the West at the weekend on down into continental Europe as a cut off feature and setting up a chilly Easterly flow with some rain at times over the South though possibly somewhat drier over the North by then.


NAVGEM NAVGEM too feeds complex Low pressure South to the west of the UK at the weekend and like UKMO keeps unsettled weather with rain at times in a cyclonic flow with temperatures remaining close to average.  

ECM. ECM keeps the UK in a broad trough over the next 10 days with Low pressure feeding down from the NW over the UK blocked by very High pressure over NE Europe. As a result unsettled weather with rain or showers looks most probable and with temperatures at best close to average and probably a little below at times.


THE ECM ENSEMBLES  The ECM Ensembles show a predomiante trend towards keeping Low pressure just to the NW of Ireland with a broad trough down over the UK ensuring the most likely scenario being a continuation of unsettled weather with rain or showers at times in temperatures close to the seasonal average.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS There seems strong agreement between the models that shows a lot of Low pressure close to the UK slipping SE from the NW over or just to the West of the UK over the period.

MY THOUGHTS  The current unsettled pattern that has become established over the last few days looks like being maintained for the foreseeable future. It also looks that the Jet stream flow driving our weather will also continue to stay quite well South near the Greenwich meridian keeping the UK on the cold side of the flow and ensuring that temperatures are held quite close to average and even quite chilly at times. Through the two weeks there looks like being various periods of rain and showers and some quieter interludes when fog and frost might develop locally. Amounts of rain could become quite large should any stalling fronts get hung up over the UK and this looks quite feasible given that there is a large High pressure block to the NE looking likely for much of the period. Nevertheless being so early in the season there is no particularly cold weather shown as yet and the weather will just feel typically Autumnal for most with the unseasonable warmth and settledness of the weather of last week a distant memory now.

[knocker]

This fits in very neatly with the GEFS