Model Output Discussion 1200 hrs 15/11/14

[carinthian]

What a horrible mess in the Alps this weekend. Massive amount of rain in parts of the Italian and Swiss Alps. Even in our location rainfall warnings still in place.  Certainly the models 7 days ago showed no sign of this amount of rainfall. Not really a Genoa Low set up, but I think fronts just staying situ with no advance eastwards, a lot of moisture and warmth aloft feeding this energy. I think this huge cold block further east is playing havoc with the forecast models for this weeks later developments. Will be interesting to watch how quickly things change. The rainfall should hopefully die in situ as our airflow should come from dryer colder direction as the week progresses.

C

[Midlands Ice Age]

 

For all the dataholics, ECMWF have a page devoted to data collection sources for its daily model runs.

 

http://old.ecmwf.int/products/forecasts/d/overview/monitoring/coverage/dcover!AMVs-Infrared!00!pop!od!mixed!w_coverage!latest!obs/

Thanks Nouska,

I found that interesting. (Probably says a lot about me)

After going through the charts at the high level, it was obvious to me that the area of the world still relatively uncovered (sparsely covered ) is south and central Greenland. As far as I could see the main coverage of that area appears to be from flights from the UK to Vancouver and Calgary. Very few other airgraft are in that corridor.

Satellites seem to stop their coverage from the equator just south of there and the polar satellites do not come that far south.

In the winter our major driver of changes seem to be exactly that area . Could it be the reason we seem not to have totally seemless forcasts in winter?

MIA  

[Polar Maritime]

Some lovely Pm shots continuing to show on the GFSP. With -3/4 uppers over the UK and fronts rattling in from the N/W, There's a very good chance of Snowfall especially for elevated locations from this set-up, And it would feel cold in a biting wind. A good start to Winter if this played true, But what with Shannon about we will just have to wait see..

 

 

Edited November 17, 2014 by Polar Maritime

[knocker]

Odd that this subject came up the other day but I readily admit this is new to me.

 

Ryan Maue â€@RyanMaue 5h5 hours ago

Explosive cyclone --> Warm seclusion + tropopause fold in Labrador Sea w/downstream Rossby wave thinning into Azores

[mushymanrob]

I feel the safest prediction based on the model output is a stalemate between the blocking to our E and the Atlantic with neither really dominating our weather. So weather wise this would result in SE,lys with E/SE likely to remain dry but extreme W areas might be threatened by rain at times.

 

Looking at the GEFS SLP mean for my location suggests pressure will remain relatively high above 1010mb.

 

https://max.nwstatic.co.uk/ensimages/ens.20141117/00/t850Cambridgeshire.png

 

However this stalemate could easily swing in either direction in the models from a colder E,ly to a full blown attack from the Atlantic.

 

exactly... and this bit of hope for those of you looking for something colder appears to have been overlooked so far this morning

 

now IF im right (and please feel free to correct me if im not) but this chart suggests an easterly to me. ok, its along way off but does make an easterly possible i believe.

until then though, we have a pretty dry and largely mild week ahead IF we get a southerly sourced south/southeasterly draft. the more of an eastern element to it will probably lower temps... but so what, its late november.

[492]

With an upper cold pool sitting close to the south, 850 mb temperatures around 2 C and surface temps of 8 - 9 C we are currently in a colder interlude before  models predict a surge of tropical continental air to move north from north Africa over the next few days. The warm ridge to the east which has been such a persistent feature over recent weeks giving the UK a warm autumn looks likely to persist and there are hints that this warm ridge may result in a dominant Russian high taking hold. A resurgent  Atlantic will at times inevitably erode the block to the east as shown by this mornings output but at times when the Atlantic flow weakens the Russian high may well extend westwards producing drier, chillier spells.  

[phil nw.]

Any posts not strictly related to model outputs may have been moved here

https://forum.netweather.tv/topic/81281-model-banter-moans-and-ramps-autumnwinter-2014/

 

where more general model related chat/ramping or moans are acceptable.

 

A reminder too that there are Met Office threads open for questions or comments around their forecasts.

 

Thanks.

[nick sussex]

Firstly thanks for all the support in ref to the last post I made; much appreciated. Sorry I don't couch my comments in obscure forum jargon or include all the things I look at or take in to account before posting; I'm sure I'll get better as time goes by or be beaten into submission just so I can fit in :-) .

 

Just to put the record straight: I LOVE SNOW! I'd love to see 3 foot of snow fall here in Dublin so I can get out my brand new Salomon Rocker2 90s and scoot down Bridge Street. But I'm a complete pragmatist and have been watching weather models for years and I simply don't see the weak blocking pattern developing into a "snowmageddon" or anything remotely like that; not for another few weeks at least.

 

Now considering both GFS and ECW are showing an Atlantic feed of low pressure systems winning over the weak blocking to the east and this is reflected in the ensembles....sorry for my naivety of my posts; but looks like I was right ...is it too soon to dust off my "I told you so" T-Shirt... :-) (that's a joke, don't worry I'm often more wrong than right)

 

and Mods...in future I'll keep my comments strictly on topic! 

Dublin is really not a great location for snow, I imagine its pretty frustrating at times in the winter.

 

In terms of whether you should dust of the " I told you so t-shirt" NWP is just that, prediction and so I'd wait a while longer. However being a pragmatist is probably a good way to deal with winters in your neck of the woods aswell as in the rest of the UK;

 

Going back to your  t-shirt theres been several Atlantic returns false dawns, only last week if the longer range output was to be believed then theres already been a climbdown.

 

This suggested return may well not happen or indeed the nature of the return may well be somewhat different than what people assume as bog standard Atlantic type weather.

 

Its a volatile situation as you can see by just the differences between one output to another.

[nick sussex]

Heres the ECM postage stamps at T120hrs:

 

http://old.ecmwf.int/samples/d/inspect/teasers/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!120!pop!od!enfo!enplot!2014111700!!/

 

Note just how many different ideas of the low at that timeframe. That is crucial for how the pattern might evolve afterwards, this low is what the models generally want to phase and take ne however you'll see on some that its much further se or indeed a shallow feature.

 

Unfortunately we don't get the upstream view here but theres also uncertainty as to how amplified the ridge will be to the west, its for this reason that any forecast be it towards colder or milder could implode quickly.

 

The GFS 06hrs run had that shallower feature which was better if you're in the cold camp, this then ran ne and back sw towards Denmark, this cut back in the jet is what you want to see:

 

 

Its always this part of trying to get to an easterly that's very difficult because without that cutback any cold is pushed se, the shortwave that you see on the pressure charts is what would usher in the colder uppers.

 

 

 

 

 

 

 

[johnholmes]

Satellites seem to stop their coverage from the equator just south of there and the polar satellites do not come that far south.

 

Polar orbiting satellites cover the whole globe.

below is just one example of the north Atlantic sector courtesy Dundee Uni

http://www.sat.dundee.ac.uk/abin/piccygridhtml/avhrr/2014/11/17/1339+19/ch5.jpg

You can get satellite images of varying types, visual, infra red etc, from pole to pole if you log into the right web site for this. Some of them you have to pay for.

Edited November 17, 2014 by johnholmes

[jules216]

Very uncertain as to where are we heading next, looking at all the ensembles 06gfs, the spread just at 180hrs around Iceland is amazing, just shows that we should use the long range forecasts cautiously,

[knocker]

Heres the ECM postage stamps at T120hrs:

 

http://old.ecmwf.int/samples/d/inspect/teasers/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!120!pop!od!enfo!enplot!2014111700!!/

 

Note just how many different ideas of the low at that timeframe. That is crucial for how the pattern might evolve afterwards, this low is what the models generally want to phase and take ne however you'll see on some that its much further se or indeed a shallow feature.

 

Unfortunately we don't get the upstream view here but theres also uncertainty as to how amplified the ridge will be to the west, its for this reason that any forecast be it towards colder or milder could implode quickly.

 

The GFS 06hrs run had that shallower feature which was better if you're in the cold camp, this then ran ne and back sw towards Denmark, this cut back in the jet is what you want to see:

 

gfsnh-5-180.png

 

Its always this part of trying to get to an easterly that's very difficult because without that cutback any cold is pushed se, the shortwave that you see on the pressure charts is what would usher in the colder uppers.

 

Question Nick

 

I see what you are saying but is not that jet cutting off access to the colder air?

Charts courtesy WxBell

Edited November 17, 2014 by knocker

[nick sussex]

Question Nick

 

I see what you are saying but is not that jet cutting off access to the colder air?

Charts courtesy WxBell

No because you need a way to transport some colder uppers into the flow. Generally in the set up that we've seen you've got a warm high that's been sitting around for quite a while so to get some colder uppers you need a shortwave to do that. Now of course had Scandi been colder as that shortwave heads sw it would have even deeper cold.

 

The shortwave also acts though to support the block and force the positive anomalies further north if you get the jet cut back, to be honest the outputs a dogs dinner because you can't even get agreement on the shortwave at T120hrs.

 

One of the most difficult set ups for the models to get right is that cutback in the jet and trigger shortwave for that reason even if the models all go for that tonight it would be firmly in my Red warning category!

Edited November 17, 2014 by nick sussex

[Paul]

NCEP are saying that the 12z GFS parallel will be delayed for around 2 hours today..

[fergieweather]

For info: I understand that the 12z GFS-P may be delayed today by up to 2hrs.

Whoops - parallel suite; parallel comments....!! Apols for duplication.

[nick sussex]

Here comes the shortwave drama! T96hrs, more amplified upstream than the earlier GFS 06hrs run, we need that energy exiting the USA to dig as far south as possible.

[knocker]

No because you need a way to transport some colder uppers into the flow. Generally in the set up that we've seen you've got a warm high that's been sitting around for quite a while so to get some colder uppers you need a shortwave to do that. Now of course had Scandi been colder as that shortwave heads sw it would have even deeper cold.

 

The shortwave also acts though to support the block and force the positive anomalies further north if you get the jet cut back, to be honest the outputs a dogs dinner because you can't even get agreement on the shortwave at T120hrs.

 

One of the most difficult set ups for the models to get right is that cutback in the jet and trigger shortwave for that reason even if the models all go for that tonight it would be firmly in my Red warning category!

 

Thanks Nick I can see that but then I suppose you need a mechanism advect the cold air west which seems unlikely at the moment particularly if the main arm of the jet moves a tad north which is one scenario. Mind the jet is a bit of a mess at the moment which reflects the whole pattern

[shaky]

This run is way different compared to the 06z run at just 96 hours!! More of an attempt from the low pressure in the atlantic to dig further south!!

[MR EXTREMES]

Odd that this subject came up the other day but I readily admit this is new to me.

 

Ryan Maue â€@RyanMaue 5h5 hours ago

Explosive cyclone --> Warm seclusion + tropopause fold in Labrador Sea w/downstream Rossby wave thinning into Azores

So what does this mean ?

[johnholmes]

Here comes the shortwave drama! T96hrs, more amplified upstream than the earlier GFS 06hrs run, we need that energy exiting the USA to dig as far south as possible.

looking at the meteorology of this Nick, how likely do you think it is for this shallow low to move se or ESE?

[nick sussex]

The GFS doesn't develop the jet cut back here but the UKMO looks more interesting than its earlier 00hrs run. I think the juries still out here because the UKMO does cut the shortwave south:

 

 

If you get more kick north in the jet then the high will go further ne.

 

 

[IDO]

D7 on the GFS and back to square one: 

 

Lots of posters saying they don't want the Atlantic to burst through, in the hope the repeating Atlantic/Sceuro block eventually develops into cold, however weeks are passing by and we are still in deadlock. Get the low heights through and after 5-7 days there will be a chance for maybe a Atlantic/Greenland ridge? Of course the WAA to Scandi will help maintain the bottom up warming so I probably shouldn't grumble too much.

 

GFS still promising 2-3 warm days at the end of the week:

 

 

 

And by D10 on the GFS:  D13: 

 

This could go on and on...

Edited November 17, 2014 by i'm dreaming of...

[Joe Levy]

Look at that southerly flow at 300 hours on the GFS 12z, drawing right up to the Arctic!

[frosty ground]

D7 on the GFS and back to square one: gfs-0-174-2.png

 

Lots of posters saying they don't want the Atlantic to burst through, in the hope the repeating Atlantic/Sceuro block eventually develops into cold, however weeks are passing by and we are still in deadlock. Get the low heights through and after 5-7 days there will be a chance for maybe a Atlantic/Greenland ridge? Of course the WAA to Scandi will help maintain the bottom up warming so I probably shouldn't grumble too much.

 

GFS still promising 2-3 warm days at the end of the week:

 

 gfs-9-120.pnggfs-9-144-2.png

 

And by D10 on the GFS: gfs-0-240-4.png D13: gfs-0-300-2.png

 

This could go on and on...

I have never seen this pattern break down to anything other than a Zonal westerly flow....... The chances of an Atlantic / Greenland ridge would be zero as the pattern supporting this block across the globe will be lost.

It's a simple case of waiting for the cold air to be dragged around the southern flank of the high like http://www.wetterzentrale.de/pics/Rtavn3841.gif

Of course by the time that happens the conditions for blocking upstream may be lost.

 

Edited November 17, 2014 by frosty ground

[weirpig]

For me the Gfs  run was a bit of a snore fest   i kind of agree with ido   this pattern could certainly persist for  a while  however with such volatilty in the models at short range  alot of options still on the table.