Model Output Discussion 26/10 2012 >

[bluearmy]

which gefs member do you prefer, number 1, 4 or 5 ?

[SMU]

1 is the best in the long run-

S

[legritter]

It does look very interesting going by current charts and data .im sure the modells will strugle this week . there is the potential for some sort of pressure change out at plus 168 hrs .a big reminder today that there is some cold air to tap into if the synoptics develope .perhaps we will see a gradual pressure rise from the east eventually ,but nothing at this stage guaranteed ,i stated to my friends last night ,hvy rain with a bit of sleet ,built slushy snowman this morning early ,oh well thats Weather for you .

[phil nw.]

Whilst the thread is reasonably quiet i thought i would look a little further out for any signs of Scandi high development--this really just for fun as they say.

Some interesting patterns showing up at T240hrs in the GFS06Z run in the way the vortex is shaped allowing some heights to develop to our east.

Here are the ones that show good heights towards Scandinavia.

compare to the mean-bearing in mind the mean tends to smooth out the wave patterns somewhat.

so no strong signal for this yet but maybe something to monitor further on say from week 3 but looking at the Ops and mean outputs no real change to the more westerly type before that by the looks of it.

[SMU]

Remember the 06z MEAN will be as useful as a chocolate teapot- as will all the GFS ensembles for the next 72 / 96 hours-

However once they do get a whiff of scandi blocking expect some stella ensemble runs to go with it...

S

[johnholmes]

I would agree with that post phil. Whilst it is fine, and I have no disagreement with the recent posts from Steve. He would be the first to agree he is an outright coldie, nothing wrong with that but it can skew ones view of what seems likely to happen. So caution for the time being would be my advice. There is nothing this morning that changes my view of the next 2 weeks or so from the pdf I did on Friday. This largely agrees with what phil has just posted.

That is the weather will not come from north or east but somewhere between north west and west south west in that time period. Cold enough at times for hill snow for more northern areas and also for the kind of 'surprise' parts of the SW had this morning. That should not have been too much of a surprise though as UK Met had suggested this as a possibility on Friday and the posts from Ian F and his blog re Exeter outputs support this.The track and development of the low also followed my pdf about how it was likely to evolve in spite of one run from GFS yesterday that dropped it altogether.

Edited November 4, 2012 by johnholmes

[Methuselah]

Remember the 06z MEAN will be as useful as a chocolate teapot- as will all the GFS ensembles for the next 72 / 96 hours-

However once they do get a whiff of scandi blocking expect some stella ensemble runs to go with it...

S

I might well be misinterpreting you here, Steve...But are you saying that, until such time as the ensembles start showing a Scandinavian block, they are all but useless?

[SMU]

HI John-

I think after 7 years on here its still frustrating, just like the other week when I forecast at Day 9 what the weather is likely to do based on the failing of all the models & that commentary which was based on the 12z GFS @ day 9 was pretty much at spot on for the longwave & shortwave pattern-

over the time here despite ALL the upgrades the models still behave in exactly the same way & also in exactly the same wrong way with particluar bias-

its become slightly annoying now that people such as yourself at a higher level cannot differentiate someone posting model bias & know failures within the models to present what is expected to develop Versus just plain ol cherry picking cold charts,

You are right, I love the cold, but would I waste hours like the last time writing stuff to try & highlight these things last time just on a whim- No, if I thought the mild weather was coming I would say it-

i have laid out over 2 or 3 posts what I expect to happen-

If you have followed everything i have posted back since the september model thread then its all been about pattern persistence around the zonal Mean anomaly & SSTA over Greenland & all about blocking around 60N - with 2 wave 3 wave or even 4 wave patterns.

You may be right to start- at day 5 -6 our weather will approach from the west/ north west, but as the jet splits & energy moves north & south so blocking will push back so eventually the mean flow will start to come from the SE ..

Not that cold to start- however certainly not very mild either unless we stay in the small wedge of mild air which will sit inbetween the returning Pm air from teh NW & the colder continental air from the East..

Your UKMO model at day 6 is a perfect example of that

S

[phil nw.]

I would agree with that post phil. Whilst it is fine, and I have no disagreement with the recent posts from Steve. He would be the first to agree he is an outright coldie, nothing wrong with that but it can skew ones view of what seems likely to happen. So caution for the time being would be my advice. There is nothing this morning that changes my view of the next 2 weeks or so from the pdf I did on Friday. This largely agrees with what phil has just posted.

That is the weather will not come from north or east but somewhere between north west and west south west in that time period. Cold enough at times for hill snow for more northern areas and also for the kind of 'surprise' parts of the SW had this morning. That should not have been too much of a surprise though as UK Met had suggested this as a possibility on Friday and the posts from Ian F and his blog re Exeter outputs support this.The track and development of the low also followed my pdf about how it was likely to evolve in spite of one run from GFS yesterday that dropped it altogether.

Simply looking at all the outputs-not just 06z GFS- shows evidence of lower heights to our north west for the next 10 days or so.

The energy coming from there is our pattern for now that`s for sure.

Yes there is signs of those heights building to our east within that period but i think any development from there seems unlikely to impact our weather within this timescale.

Further on- as i said earlier- then maybe.

Edited November 4, 2012 by phil n.warks.

[bluearmy]

1 is the best in the long run-

S

and no 1 is the 'coldie run' that fits best with current fi trends. (which may change by tomorrow). the mean gefs is always tricky to make sense of without checking against the spreads. that continues to reveal the most likely place to find the lowest heights in the NH will be n greenland/far ne canada over the next couple of weeks. however, the mean does show heights generally rising to our north in week 2 so worth watching if subsequent gefs runs maintain this theme.

and i agree with steve about those times when you can see that something is brewing in the nwp rather than just picking out the odd ens member that shows snowmageddon.

Edited November 4, 2012 by bluearmy

[SMU]

I might well be misinterpreting you here, Steve...But are you saying that, until such time as the ensembles start showing a Scandinavian block, they are all but useless?

YEP.

THe GFS enembles esp the 06z & 18z will not see the blocking at 168, because of their resolution. As a result the atlantic will be loaded & go over the top-

We are however reaching the point where the operational is seeing the correct distribution of energy at 144-168, the ensembles will follow suit usually 24- 48 hours later-

So when they latch onto it there will be a lot of swing in the ensemble mean & outputs-

Any ensemble at 168 that has no scandi blocking at all with a zonal flow is for the bin..-

s

[lorenzo]

1 is the best in the long run-

S

1 carves heights right across the polar field. 5 however looking very tasty at the extreme end of FI if you are on the hunt for cold synoptics and some eye candy.

[johnholmes]

HI John-

I think after 7 years on here its still frustrating, just like the other week when I forecast at Day 9 what the weather is likely to do based on the failing of all the models & that commentary which was based on the 12z GFS @ day 9 was pretty much at spot on for the longwave & shortwave pattern-

over the time here despite ALL the upgrades the models still behave in exactly the same way & also in exactly the same wrong way with particluar bias-

its become slightly annoying now that people such as yourself at a higher level cannot differentiate someone posting model bias & know failures within the models to present what is expected to develop Versus just plain ol cherry picking cold charts,

You are right, I love the cold, but would I waste hours like the last time writing stuff to try & highlight these things last time just on a whim- No, if I thought the mild weather was coming I would say it-

i have laid out over 2 or 3 posts what I expect to happen-

If you have followed everything i have posted back since the september model thread then its all been about pattern persistence around the zonal Mean anomaly & SSTA over Greenland & all about blocking around 60N - with 2 wave 3 wave or even 4 wave patterns.

You may be right to start- at day 5 -6 our weather will approach from the west/ north west, but as the jet splits & energy moves north & south so blocking will push back so eventually the mean flow will start to come from the SE ..

Not that cold to start- however certainly not very mild either unless we stay in the small wedge of mild air which will sit inbetween the returning Pm air from teh NW & the colder continental air from the East..

Your UKMO model at day 6 is a perfect example of that

S

hi Steve

I have no intention of belittling what you are saying. I suspect your view is based on what you feel will happen outside the period my pdf was focussed on, did you read that? As phil has suggested there seems little probability of an east based flow of either upper or surface air BEFORE day about day15 or so. Would you agree on that?

My previous post simply attempted to suggest folk be cautious about what MAY happen beyond about day 7-10. Perhaps all of us with a reasonable knowledge should actually be specific in T+xyz times that we are talking about so everyone knows just what time scales we are dealing with?

[Frosty.]

The only thing I noticed on the Gfs 00z ens mean was the rise in pressure to the south and east at the end of FI with a more benign pattern with increasing risk of fog and slight frosts but pleasantly mild days in the sunnier areas, this is outside the next 2 weeks though but surely the current unsettled pattern will have to take a rest at some point, well actually it does in the next 5 days, less unsettled, turning milder but still with some patchy rain around despite slightly higher pressure, the best of the sunshine probably tomorrow.

Edited November 4, 2012 by Frosty039

[SMU]

Yeah no worries John-

Day 5-6 Scandi block forming-

6-10 building & sustaining- Final location TBC- However expect the 'prediction' to go further west with time!

S

[Glacier Point]

Very interesting nuances developing in longer range stuff over the last couple of days. Remember waxing and waning.

We have a developing (anomalous) high pressure cell over Siberia. This is Cohen's first response to anomalous snow cover advance in October. The eastern flank of this has begun to pull the blocking structure over Kamchatka back west.

We also are seeing developing anomalous ridge over wester Russia and eastern Europe in response to lowering heights over Greenland phasing with a longwave trough digging through the North Atlantic. This has important potential ramifications w/r/t stratospheric temperatures in December.

I agree with the sentiments above, the weakness in NWP to place and model troughing in the Atlantic this year. We are likely to see any toughing further south the closer we get, allowing for trough disruption and downstream ridges to get reinforced. We are now effectively early into a winter synoptic, and models are generally pretty weak with the presence of a strong Siberian High pressure cell.

That sets us up with an intriguing prospect. Heights building over the far NE and long term signal to restrogress the ridge towards Greenland (waxing).

Longer term still sees CFS week 4 advertising Greenland High, and NAEFS also leading to this with the rebuilding of a wavelength lead by Kamchatkan ridge.

[BLAST FROM THE PAST]

The timescal IMO is day 10 to 14 for developments of pattern to control backend of November. Interesting...no v interesting reading the PDF from JH, Steve M's posts above and I'm sure we'll have imput from GP soon.

lol, he just has...

BFTP

Edited November 4, 2012 by BLAST FROM THE PAST

[SMU]

Very interesting nuances developing in longer range stuff over the last couple of days. Remember waxing and waning.

We have a developing (anomalous) high pressure cell over Siberia. This is Cohen's first response to anomalous snow cover advance in October. The eastern flank of this has begun to pull the blocking structure over Kamchatka back west.

We also are seeing developing anomalous ridge over wester Russia and eastern Europe in response to lowering heights over Greenland phasing with a longwave trough digging through the North Atlantic. This has important potential ramifications w/r/t stratospheric temperatures in December.

I agree with the sentiments above, the weakness in NWP to place and model troughing in the Atlantic this year. We are likely to see any toughing further south the closer we get, allowing for trough disruption and downstream ridges to get reinforced. We are now effectively early into a winter synoptic, and models are generally pretty weak with the presence of a strong Siberian High pressure cell.

That sets us up with an intriguing prospect. Heights building over the far NE and long term signal to restrogress the ridge towards Greenland (waxing).

Longer term still sees CFS week 4 advertising Greenland High, and NAEFS also leading to this with the rebuilding of a wavelength lead by Kamchatkan ridge.

Hi Stewart-

Did you know the SAI >>> + Positive Siberian Height anomaly have positive feedbacks to a slower vortex- offsetting the downwelling from Stratospheric > tropospheric Coupling-

S

[Glacier Point]

Yes Steve - anomalous ridge to our E setting up wavetrain with enhanced wave 2 activity leading to decceleration of upper level westerlies.

[EML Network]

Looks to me like were stuck in a cycle of Low Pressure systems squeezing between the gap under Greenland Block and above the Atlantic High out to our West, and it's been that way for some time now.

I think it's quite clear, in this type of set up we need to start looking to the East for high pressure, if we can get High pressure moving in from Siberia / Russia, it would force a northerly incursion, and those Low Pressure systems barreling through the Gap would force the Atlantic High out of the way , the Lows would take it's place, the High would inhibit any further Eastward movement and open then flood gates for a Northerly / North Easterly incursion

I did say that we should start looking East !! :-)

Edited November 4, 2012 by EML Network

[Biggin]

Yes Steve - anomalous ridge to our E setting up wavetrain with enhanced wave 2 activity leading to decceleration of upper level westerlies.

Blimey thats a mouthful

[SMU]

When we refer to ZDL ( Zero degree level) falling rapidly & Evaporational cooling - heres a perfect example from the met office of what happened today for all those in the SW-

Worth a look as this type of scenrio happens a lot for the UK

http://www.bbc.co.uk...atures/20199175

When you see the cold surface air coming from the North- this is the same as cold surface air from the East in undercut situations.....

12z out to 102 & the wave over the atlantic that morphs into the Scandi ridge is already slightly more amplified ( of course as expected)

http://modeles.meteociel.fr/modeles/gfs/runs/2012110412/gfsnh-0-102.png?12

S

Edited November 4, 2012 by Steve Murr

[A Winter's Tale]

Good afternoon. The channel low that brought snow to parts of the south west and rain to other southern areas should make it's way to the north sea but some light rain may continue in East Anglia through this evening before the rain eventually fizzles out. Showers may continue along the channel coast and south western parts of England and Wales in the westerly wind. Elsewhere, other than odd shower it should be largely dry through this afternoon and evening as winds across northern areas changes to an easterly. Some sunny intervals may be possible across northern Ireland and north western parts of England and some western parts of Scotland but cloud cover may increase in some eastern areas with the winds coming off the north sea. Temperatures should max at 5 to 11C. Overnight, clear spells should develop Scotland, northern England and parts of Ireland but there should be showers during the night in coastal parts of northern and eastern Scotland and north eastern England. Cloudier in the southern third with showers continuing in the south west and along the channel coastline. A cold night too with lows of 0 to 7C.

Monday morning should start off with some sunny spells for many areas away from the far south coast - but skies should clear here later in the day as the shower activity sinks further south - parts of Ireland could have some cloud cover to start the morning off and possibly increased cloud cover across some eastern areas at times and the north of Scotland with the risk of showers here. Through the afternoon the shower activity should die down and sunny spells should become much more widespread but parts of Ireland and north western Scotland could end up cloudier. Maximum temperatures should be on the cold side at 5 to 10C. Through the evening there should be widespread clear skies for Bonfire's Night - particulary across the south west and central England. Still a reduced risk of showers for some north sea coastal regions and cloud cover should increase in the north west of Scotland with some drizzle developing. Monday night should be dry and clear for southern and eastern areas but cloud cover should increase in the north and west with rain arriving across northern and western Scotland. Still another cold night with lows of 1 to 8C.

Tuesday should be a cloudier day for the British Isles with and the overnight rainfall in Scotland should be over the eastern side of Scotland and southward into England. A much milder day with highs of 8 to 11C. Tuesday night should be a mostly cloudy night other than a few clear spells in places but mostly overcast across northern and western areas in particular as a band of rain arrives from the north west. A milder night too with lows of 5 to 10C.

Wednesday is also looking overcast with some outbreaks of rain across western areas and temperatures still milder than of late with highs of 9 to 12C. And the overnight period could also be overcast with further rain across western areas - particulary north western Scotland with general lows of 4 to 10C.

Thursday should still be on the cloudy side for most with a few isolated outbreaks of rain around western coasts. Some sunny spells can't be ruled out further east and maximum temperatures should be 9 to 11C. Thursday night should start off cloudy and dry but out to the west lurks the next frontal system that's set to bring widespread persistent and heavy rainfall. Possible lows of 4 to 10C.

Monday should be the last of the cold days with sunny spells and cold, frosty nights - should be nice crisp conditions for Bonfire's night - before we see temperatures becoming milder with typical highs of 8 to 11C and increased cloud cover for all of us with some outbreaks of rain for western areas and the threat of some frontal systems on one or two days.

The outlook beyond late next week at the moment is looking like a mostly unsettled picture with low pressure close to the British Isles but it's looking like a changeable picture with a mixture of showers and depressions with a mixture of polar and tropical maritime air so it's an interesting, active period to follow with changes from run to run. There is a presence of high pressure to the south west of the British Isles but interestingly there looks like air pressure should increase across western Russia. It will be interesting to see how long the high pressure stays there and to track the movement of high pressure possibly attempting to end up over Scandinavia so this really is an interesting trend so let's see how it goes. If we do end up getting heights to our north east then there could be an interesting stand-off between the block and the atlantic depressions.

[OldMetMan]

Although there are some fairly consistent model trends in the near to mid-term at present, namely a succession of deep LPs moving SE and settling over or near the UK, the longer term trends are somewhat difficult to read at this stage.

We currently have a somewhat static wave train at 500mb, with 4 major vortices, including one near the UK, roughly 90 deg apart. The jet configuration had made some changes but the strongest jet still remains over China and the W Pacific. Although I wouldn't call the overall flow particularly blocked, the pattern is not really showing any immediate signs of turning zonal, so I would agree with much of the model output as regards persistent LP near the UK, as the upper low remains close by,

A couple of things that have caught my eye however. First, most of the jet energy on our side of the hemisphere is pretty well south, with a rather disjointed polar jet at our latitude.

The other thing, for the longer term, is that I notice both the GEM and GFS are building HP over Russia and into Scandinavia - not unusual at this time of year - but it does suggest to me - based on what I have seen happen in the past - that the last LP in the train coming from the NW will finally sink away to our SE allowing some build of HP over us, from the E and NE. This, I think, would fit in well with a stronger southern jet and would coincide with a weakening polar jet, and would tend to reestablish the Omega block from earlier in the week. I don't have much to back that development up at this stage - as I said I have seen this kind of evolution in the past.

I think later runs might clarify but, in the meantime, expect plenty of rain and, at times, strong winds - and some cold nights!

[AWD]

A pretty compact thermal gradient over the Eastern Seaboard.

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=138&code=0&mode=1&carte=1

Expect some deep LP systems to form there and head into Southern Greenland and down into the UK in week 2 of this GFS 12z run.