Model Output Discussion

[BLAST FROM THE PAST]

The trend is certainly for things to back east over the coming days.

The residual energy(shortwave )that hangs to the west of Svalbard

could very well disappear or move south with the rest of the trough

over subsequent runs which would lead to a much colder run than is

presently being shown.

Plenty to watch over the coming days.

Nope, only the GFS shows that at present. BUT as TEITS says in these set ups everything does get shunted east nearer the time.

BFTP

[Thundery wintry showers]

Still don't agree.

Locations that have seen their most widespread snowfall from NE/E,lys are NE Scotland/NE England/E Anglia/SE/E Midlands. The locations that are exempt from this are mainly NW/SW England/Wales who have seen frontal snowfall.

The amount of snow I have seen from the N measures 0cm so far this winter!!

Although the most widespread snowfalls in NE England came from NE winds, with the sole exception of the 17th/18th December, the cold air came down from the north, i.e. a NE'ly with a "northerly" source so that doesn't invalidate Mr_Data's point. Also, the above is missing the convective snowfalls that hit much of western Scotland, Ireland, and NW England between the 20th and 23rd December, primarily from westerly winds which brought cold air sourced from the north. There were then heavy snowfalls in the Tyne and Wear area overnight 29th/30th January from another northerly.

Similarly, in Norwich, there were snowfalls from an E'ly on 17/18 December, but other than that, the biggest snowfalls- 6 to 8 January and 29/30 January- were sourced from the north. When the winds came across from the east, as on 9-14 January, the result was warmer air and dull sleety stuff.

A northerly being shunted east allowing a NE'ly over south-eastern areas would be good for snow in Peterborough but not necessarily for areas away from eastern England, especially if HP is close by to the NW. Widespread snow from a NE'ly would preferably involve a fair amount of LP to the SE.

[Iceberg]

ECM has moved east already from yesterday (by approx 300 miles) for the cold after the retrogression, however looking at the 00Z EPS for London today, it shows that ECM was at the top of the max temps range from the 16th onwards, probably showing that it was too progressive in it's retrogression.

The 12Z ECM will have shifted approx 300 miles again more easwards IMO.

Sorry just to add the 06Z ops keeps the cold around now until maybe the 23rd, the ENS 06Z to the 21st or so.

[TEITS]

Although the most widespread snowfalls in NE England came from NE winds, with the sole exception of the 17th/18th December, the cold air came down from the north, i.e. a NE'ly with a "northerly" source so that doesn't invalidate Mr_Data's point. Also, the above is missing the convective snowfalls that hit much of western Scotland, Ireland, and NW England between the 20th and 23rd December, primarily from westerly winds which brought cold air sourced from the north. There were then heavy snowfalls in the Tyne and Wear area overnight 29th/30th January from another northerly.

Similarly, in Norwich, there were snowfalls from an E'ly on 17/18 December, but other than that, the biggest snowfalls- 6 to 8 January and 29/30 January- were sourced from the north. When the winds came across from the east, as on 9-14 January, the result was warmer air and dull sleety stuff.

A northerly being shunted east allowing a NE'ly over south-eastern areas would be good for snow in Peterborough but not necessarily for areas away from eastern England, especially if HP is close by to the NW. Widespread snow from a NE'ly would preferably involve a fair amount of LP to the SE.

Yes but Norwich differs hugely compared to Peterborough because often Norwich does rather well from a N,ly. Still im already tired of this debate and disagree with you and Mr D.

As for your last comment I did say "from a selfish point of view".

A LP centred over the UK could bring snowfalls. However this would be marginal in some locations with the risk of becoming less cold thereafter. What I described i.e pattern further E would not only bring colder temps but prolong the cold spell.

Impressive ensembles with the mean never rising above -7C until distant F.I.

http://charts.netweather.tv/ensimages/ens.20100209/06/t850Cambridgeshire.png

[Neilsouth]

I keep seeing members saying " SLACK WINDS " , however go onto the coast and things are much different. It's gusty and it takes your breath away at times ! , so it's still boding well for midweek onwards according the models. Sure it's looking less so than previously thought but the trend is still there for us kentish folk

[Cecil Hogmanay Melchett]

I keep seeing members saying " SLACK WINDS " , however go onto the coast and things are much different. It's gusty and it takes your breath away at times ! , so it's still boding well for midweek onwards according the models. Sure it's looking less so than previously thought but the trend is still there for us kentish folk

Hopefully neil although the NAE model has it pretty dry for most until Thur inc Kent.Fingers crossed Thurpm/fri for

you guts although im far from convinced.

[karyo]

Sorry just to add the 06Z ops keeps the cold around now until maybe the 23rd, the ENS 06Z to the 21st or so.

Yes, impressive 6z ensembles, prolonging the cold spell. http://www.netweather.tv/index.cgi?action=ensviewer;sess=

An upgrade from the 18z and 0z ensembles! The 18z ensembles for London were keeping the -5 uppers till the 19th, so a nice extension there!

Let's hope the 12Z ECM will start shifting the block to the east, but until I see it I am rather cautious! Also, not good that the GEM has gone with the ECM.

Karyo

[Thundery wintry showers]

I would recommend not taking the GFS Precipitation at face value in these situations. Today we're progged to have just very light precipitation across much of the country (the kind of output that, in a westerly or anticyclonic type, often translates to dull with the odd bit of drizzle) and convective precipitation is progged to be very limited. Instead, we have some pretty widespread showers across central and eastern parts.

None of the models seem particularly good at handling convection over the North Sea.

[Craigers]

I would recommend not taking the GFS Precipitation at face value in these situations. Today we're progged to have just very light precipitation across much of the country (the kind of output that, in a westerly or anticyclonic type, often translates to dull with the odd bit of drizzle) and convective precipitation is progged to be very limited. Instead, we have some pretty widespread showers across central and eastern parts.

None of the models seem particularly good at handling convection over the North Sea.

i can back you up with this as the showers here are looking active now and no way they are light ppn ones!!! got to say if this high pressure keeps trending northwards then westwards then we could be looking at the proper last blast of the winter

[LochGarman]

Hi Folks..this is my first post here so please excuse me if i happen to put my foot in my mouth.

A number of you have mentioned (teits and bftp i think) that fronts have a tendency to be pushed East over time...e.g. the low pressure system coming from the North may be pushed east.

Why is this?...is it the high pressure system or pressure from the lows in the Atlantic that cause this?

Most of you are hoping the low pressure system (thats shown on the models moving from the north at the weekend) moves more East on the ECMWF?

is this from a purely a snow event point of view or is there something else you are looking at like colder winds?

Cheers.

[Frosty.]

A much better Northerly next week from the GFS 06z, a direct hit instead of the ecm and gem which have most of the energy too far west so we end up with a cold sw'ly instead! it would still be cold and unsettled next week but the coldest air would soon get mixed out and snow would become restricted to northern hills. The 6z will hopefully be the trend on future runs, would bring a lot of heavy snow showers southwards together with severe frosts.

[mickpips]

Hi Folks..this is my first post here so please excuse me if i happen to put my foot in my mouth.

A number of you have mentioned (teits and bftp i think) that fronts have a tendency to be pushed East over time...e.g. the low pressure system coming from the North may be pushed east.

Why is this?...is it the high pressure system or pressure from the lows in the Atlantic that cause this?

Most of you are hoping the low pressure system (thats shown on the models moving from the north at the weekend) moves more East on the ECMWF?

is this from a purely a snow event point of view or is there something else you are looking at like colder winds?

Cheers.

I think you may have misunderstood ... its not that they move East , but the modelling tends to forecast many to be too far west ... I have seen this on countless occasions over the years and as some have pointed out , its usually when we are foecast for a huge northerly blast etc , for it then to pan out to move through the North Sea. On this occasion everything is out west so fingers crossed it all shifts East a tad

[swilliam]

I would recommend not taking the GFS Precipitation at face value in these situations. Today we're progged to have just very light precipitation across much of the country (the kind of output that, in a westerly or anticyclonic type, often translates to dull with the odd bit of drizzle) and convective precipitation is progged to be very limited. Instead, we have some pretty widespread showers across central and eastern parts.

None of the models seem particularly good at handling convection over the North Sea.

It also seems the showers are starting and growing over inland due to insolation. I would have thought the models would have handled this better

[Thundery wintry showers]

It also seems the showers are starting and growing over inland due to insolation. I would have thought the models would have handled this better

Yes, this aspect of the shower activity has surprised me this early in the month, but I've known it happen in northerly/north-easterly regimes in February before, e.g. 27/28 February 1993, 23/24 February 2001, 25-27 February 2004, 13 February 2005. The sun is getting higher and stronger which means not only higher daytime temps but also more convection.

[karyo]

I am not so keen on the Met Office update! It seems to go with the ECM & GEM scenario, as they expect rain or sleet with hill snow for next week. Snow at times at low levels only in the north. If the update was supporting the GFS scenario, there would be snow across the UK and not just the high ground!

Karyo

[karyo]

<br /><br /><br />Oh dear I had high hopes next week, for us in the NW. Still maybe the GFS is the one to be right this time.

It is worrying but things can change for the better! In this case, shift east.

It's funny but none of the gefs ensembles go with the ECM/GEM scenario. The 12z's will be interesting!

Karyo

[Iceberg]

Yes, this aspect of the shower activity has surprised me this early in the month, but I've known it happen in northerly/north-easterly regimes in February before, e.g. 27/28 February 1993, 23/24 February 2001, 25-27 February 2004, 13 February 2005. The sun is getting higher and stronger which means not only higher daytime temps but also more convection.

Yep, I think to be fair the UKMET realise that their global models and even the NAE are not good enough for shower activity like this, hence why they don't use these models at 24 hrs, they instead use the UKV, Somebody (sorry I can't remember who it was) put up a PDF of how much better the newer models at the MET are.

[bluearmy]

Re the propensity for the models to shove everything east as we approach verification:

doesnt that depend what the 'zonality' situation is. next week we will likley have neg zonality to our north so that would imply the models may shunt everything west as verification approaches. for my tuppeny bit, i think this is casuing headaches for the nwp and we may be getting too hung up on it at a range which isnt manageable for the models at present.

[SnowBallz]

Yep, I think to be fair the UKMET realise that their global models and even the NAE are not good enough for shower activity like this, hence why they don't use these models at 24 hrs, they instead use the UKV, Somebody (sorry I can't remember who it was) put up a PDF of how much better the newer models at the MET are.

Met Office

Provisional Model Upgrade

Timetable 2010

• January 2010

• Global model to 25km
• Upgrade Global ensemble to N216 (~60km) / L70
• Upgrade regional ensemble to 18km/L70
• Replace the stochastic kinetic energy backscatter (SKEB1) and
  stochastic convective vorticity (SCV) schemes with the SKEB2
  scheme (MOGREPS-G).
• Revised screen T diagnostic
• New soil ancillaries and van Genuchten soil hydraulics

• Spring 2010

• Physics upgrade including new PC2 cloud scheme

Edited February 9, 2010 by SnowBallz

[chionomaniac]

Re the propensity for the models to shove everything east as we approach verification:

doesnt that depend what the 'zonality' situation is. next week we will likley have neg zonality to our north so that would imply the models may shunt everything west as verification approaches. for my tuppeny bit, i think this is casuing headaches for the nwp and we may be getting too hung up on it at a range which isnt manageable for the models at present.

I would think that is a very sensible approach ba. When one considers that propagation of any waves of negative zonal wind anomalies are often poorly modeled it is better to wait and see. For the record the forecast suggests a stronger pulse of propagated easterlies at the T+5/6 days. For me the positioning of these I feel will help with the formation of an Arctic high more than anything. Another thing to be aware of is that the net zonal mean winds at the 100 hPa level are forecast to be negative at 60ºN for the next 5-6 days as well before returning to positive and this is likely to give easterly inertia at this latitude from the off.

Edited February 9, 2010 by chionomaniac

[bluearmy]

Met Office

Provisional Model Upgrade

Timetable 2010

• January 2010

• Global model to 25km
• Upgrade Global ensemble to N216 (~60km) / L70
• Upgrade regional ensemble to 18km/L70
• Replace the stochastic kinetic energy backscatter (SKEB1) and
  stochastic convective vorticity (SCV) schemes with the SKEB2
  scheme (MOGREPS-G).
• Revised screen T diagnostic
• New soil ancillaries and van Genuchten soil hydraulics

• Spring 2010

• Physics upgrade including new PC2 cloud scheme

thanks for that though typically for a uk govt organisation, it doesnt go into details as to if and when these changes are going to go live (unlike the ecm and GFS upgrades on which we were well informed)

[pinball wizard]

thanks for that though typically for a uk govt organisation, it doesnt go into details as to if and when these changes are going to go live (unlike the ecm and GFS upgrades on which we were well informed)

There is a good reason for that bluearmy, its because these things need to undergo extensive testing and if they find anomolous results they have to go through more testing/development. Whats the point in naming a date when they cant guarantee it will be ready, if you do that then you end up having people complain that its either not working or not on time. We all know models are complex things and i'd have thought developing them is a very complex task.

[The Weather Dragon]

Met Office update as expected after discussing this with my contact yesterday. We seem to have missed the opportunity to get hold of some cold uppers this weekend. The bulk of the cold is slipping into France as illustrated in the latest model runs. It looks likely that there will be milder air mixed up with next weeks Northerly - snow only for higher elevations. We are definately going to have a cold spell - however it is going to be a fairly mundane affair for most with a wintry mix of precipitation the best we can hope for together with some frost. By the way it's a lovely day out here today clear blue skys and an increasingley warmer sun

[karyo]

Met Office update as expected after discussing this with my contact yesterday. We seem to have missed the opportunity to get hold of some cold uppers this weekend. The bulk of the cold is slipping into France as illustrated in the latest model runs. It looks likely that there will be milder air mixed up with next weeks Northerly - snow only for higher elevations. We are definately going to have a cold spell - however it is going to be a fairly mundane affair for most with a wintry mix of precipitation the best we can hope for together with some frost. By the way it's a lovely day out here today clear blue skys and an increasingley warmer sun

This is certainly a risk if things turn out as the ECM suggests. If it however takes the block a bit further east, it could be snoiwfest for most!

The MJO is well and trully in phase 8 now http://cawcr.gov.au/bmrc/clfor/cfstaff/matw/maproom/RMM/phase.Last40days.gif

and we need it to stall there rathen than progress further.

Karyo

[kold weather]

If there is one VERY good bit of information, the ECM can sometimes have a wild west bias when it comes to developing upper highs in more northern locations, indeed pretty much all models have a western bias, the GFS suffers quite often with these in toppler type airflows, the ECM is usually better but it too can be way too far west at times as well...so thats something to really remember IMO...and I'd call it now and say we will see the eventual set-up somewhat closer to the 06z then the 0z ECM...however the 0z ECM is the eventual evolution, its just way too quick in shunting it all westwards...