Model Output Discussion 25/11/2012 12Z onwards

[kold weather]

I am being cautious. The GFS op run is brilliant but there are so many other outcomes on the ensembles at such a short time frame they can't be used for guidance to any great extent.

Also my "concern" on the UKMO is that the block to the west looks like it's not going to hold after 144hrs.

http://www.meteociel...44-21.GIF?25-17

Too much energy south of GL.

Don't worry about it, as long as higher heights are to our north over Greenland, anything that does get through is heading SE. At worst, it'll end up over us, at best and it just helps strengthen our cold flow.

The ensembles are a mess, the ops are leading this as they have better resolution, the ensembles are just not handling the upper blocking at all, the runs that destroy the northern blocking before 144hrs aren't worth a penny.

[johnholmes]

When is a short wave a short wave and not a low pressure system?

If I knew that answer I would explain. The term short wave is used far too often, troughs, low pressure systems within the major trough ridge system is a less 'smart' expression but to me personally is a better way of describing what we often see. But each to their own.It might also help if some reasonable geographical position was given to the term when using it?

[Eskimo]

I always thought a shortwave was a small kink in the isobars, neither an established trough and definitely not a low pressure system.

[SMU]

Hi I am a new member of the forum, I hope all are well.

A question for Steve Murr are we looking at a NE/E winds towards the weekend or more of a Northerly, here in SE Scotland in the central belt we need more of a NE feed for showers to come inland?

The GFS so far is the most extreme with Northerly winds- alough with embedded troughs- UKMO has more NE winds with a trough-

Your Win win

S

[BurwellWeatherWatch]

When is a short wave a short wave and not a low pressure system?

i think it's one of those overused catch-all terms that is used too often without much clarity! We tend to have a word-of-the-year that dominates the model output. Faux cold was order-of-the-day a few years ago. Shortwaves was the obsession last year. Kamchatkan ridge looked like taking over the place a couple of weeks ago.

[NickR]

I always thought a shortwave was a small kink in the isobars, neither an established trough and definitely not a low pressure system.

That was my understanding. I was confused by the image showing lows as shortwaves.

[lorenzo]

Hi I am a new member of the forum, I hope all are well.

A question for Steve Murr are we looking at a NE/E winds towards the weekend or more of a Northerly, here in SE Scotland in the central belt we need more of a NE feed for showers to come inland?

Welcome to Net Wx Penicuik Blizzard, have a look on the Scottish Regional Thread our resident snow guru Lomond Snowstorm has got everything all worked out for you.

In relation to the 12z - what an effort from the UKMO. Stunning.

Edit : Short Waves

Edited November 25, 2012 by lorenzo

[Buriedundersnow]

Hi I am a new member of the forum, I hope all are well.

A question for Steve Murr are we looking at a NE/E winds towards the weekend or more of a Northerly, here in SE Scotland in the central belt we need more of a NE feed for showers to come inland?

i stay in falkirk and we really need a north easterly or an easterly a northerly doesnt really give anything as the highlands being in hte way dont know how that helps u dont know how far from me u are

just noticed your name lol. u might be ok with a northerly aswell aslong as it wasnt slightly northwesterly as then the highlands would be in the way but more northeasterly the better.

Edited November 25, 2012 by Buriedundersnow

[johnholmes]

Just a quick post from me before I drop into a bath following my hike in the Peak today and the promise of a detailed look at how things look in the 6-15 day time scale perhaps a touch further.

I've tried to quickly trawl through the model thread since I left it around 0730 this morning.

Quite funny really I see that the 06z was well favoured-most unusual.

Some concerns being expressed about various ifs and buts on the 3 runs from GFS today. There is NO sign of any break in the predicted cold weather in the next 10-12 days probably longer once it gets going as this week progresses.

Snow-who knows at T+ beyond 24 hours. How accurately did any model predict the rainfall amount for you in the last 24 hours more than 48 hours ahead? There are 7 other variables in predicting snow so I hope that gives an idea of how reliable snow forecasting is, other than in very general terms, remaining cold, frosts at night and further wintry showers with snow mostly over high ground' type thing. There is a reason why the professional are very wary of warning of apolyptic amounts well in advance!

Edited November 25, 2012 by johnholmes

[Tom Quintavalle]

I am being cautious. The GFS op run is brilliant but there are so many other outcomes on the ensembles at such a short time frame they can't be used for guidance to any great extent.

Also my "concern" on the UKMO is that the block to the west looks like it's not going to hold after 144hrs.

http://www.meteociel...44-21.GIF?25-17

Too much energy south of GL.

Tbh Eagle,

I actually think the synoptic profile around S.Greenland on the 144 UKMO chart is slightly better than the GFS 12z, and that went on to produce a very good run.

http://www.meteociel...&nh=1&archive=0

http://www.meteociel...&mode=0&carte=1

Block a little stronger and low near southern tip of Greenland further west with slightly better WAA running north through W.Greenland, on the UKMO 12z.

Regards,

Tom

Edited November 25, 2012 by TomSE20

[Penicuikblizzard]

Thanks for the replys folks, will get used to the charts in time!

[Methuselah]

Hi I am a new member of the forum, I hope all are well.

A question for Steve Murr are we looking at a NE/E winds towards the weekend or more of a Northerly, here in SE Scotland in the central belt we need more of a NE feed for showers to come inland?

Welcome PB...

[Mike Storm]

wow 7 pages in a few hours.... and Steve Murr back and posting away... it can only mean one thing... SNOW!!!!!!!!!!!!

[Backtrack]

I always thought a shortwave was a small kink in the isobars, neither an established trough and definitely not a low pressure system.

This is exactly what I was about to post. I thought a shortwave was a kind of buckle in the flow, as PS says here, a kink in the isobars.

Is this incorrect?

[NickR]

This is exactly what I was about to post. I thought a shortwave was a kind of buckle in the flow, as PS says here, a kink in the isobars.

Is this incorrect?

Given how much they are being mentioned, would it not be a good idea to get a definition? This is exactly how I've always understood them. For that reason I think the chart posted earlier was wrong and misleading... unless the definition has changed in recent weeks???

[IDO]

I always thought a shortwave was a small kink in the isobars, neither an established trough and definitely not a low pressure system.

This is the link I use for refreshers on short waves:

http://www.theweathe.../habyhints/131/

http://www.theweatherprediction.com/charts/700/13.jpg

Edited November 25, 2012 by i'm dreaming of...

[EML Network]

I always thought a shortwave was a small kink in the isobars, neither an established trough and definitely not a low pressure system.

Yup I thought the same.

Whilst were on the subject..when does a Low pressure system become a 'trough' ?? does it depend on it's orientation and shape ??

Edit * never mind, just seen the link above

Edited November 25, 2012 by EML Network

[Eskimo]

Excuse me Mods whilst I post this, might prove educational to some users.

Here is the difference between a trough and a shortwave. A shortwave is a kink in the isobars and ironically looks like a wave. A trough on the other hand is a shallow low and doesn't really have a defined pressure centre like a proper system.

In fact on the Trough Image you can see the difference between the trough circled and a Low pressure system just below it with the tightly packed isobars.

Edited November 25, 2012 by PerfectStorm

[Bobby]

I'm going to nail my colours to the mast and say I am not buying this cold spell until there's decent ensemble and NAEFS agreement whatever the OP runs show. Hopefully it comes soon but personally I'm waiting til or if we get that.

Edited November 25, 2012 by Barb-

[I remember Atlantic 252]

Shortwave I think was what gave my unexpected snow 0n 5th Jan 1998, I thought it was another word for a small low, but not a proper low

[AWD]

As expected, the GFS Operational was a cold outlier in its extended output;

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=306&y=141&ville=Londres

But focusing purely on the next week or so, agreement is beginning to emerge.

[Weathizard]

Big outlier by the gfs in Fi, downgrades the uppers for my area for next weekend, all part of the ride though would still much prefer the UKMO. Hope ECM improves this evening from the dirge of this mornings 0z

[cooling climate]

Just before the 12z ECM run comes out it should be mentioned that the ECM model has

been really struggling the last few days with this pattern change and this might still be the

case especially in the mid range output.

Just saying thats all.

[Jonan92]

More reasons to worry, BOM following what GEM and NOGAPS showed before

Edited November 25, 2012 by Jonan92

[Ian Brown]

There are now 3 minor models opposing the GFS and UKMO position. If the ECM backs the BOM, GEM and NOGAPS, then this could be over before it's begun - such is the finely balanced nature of the synoptics.

Further to this, a number of the GFS ensemble members look the same way as the 3 above, we have to think every possibility that ECM will go the same way.

Edited November 25, 2012 by Terry Michael Wood