General Model Output Discussion

[Neilsouth]

mm of rain. A rough guide is that 1mm of rain will give 1cm of snow, as lying snow is ~90% air!

Great fax charts tonight which are virtual carbon copies of the NAE output:

http://www.meteociel.com/ukmo/fax/fax24s.gif

http://www.meteociel.com/ukmo/fax/fax36s.gif

I'd bet these will be different come tomorrow , so i'll save both to the hard drive and compare in the morning and night

[Altohumorous]

mm of rain. A rough guide is that 1mm of rain will give 1cm of snow, as lying snow is ~90% air!

Great fax charts tonight which are virtual carbon copies of the NAE output:

http://www.meteociel.com/ukmo/fax/fax24s.gif

http://www.meteociel.com/ukmo/fax/fax36s.gif

Are these charts showing a likely influx of too much marginal "North Sea-influenced" air/ not enough Arctic influx in the system(s) tomorrow?

[Duane S.]

Awful charts tonight. It's going to be dry or be raining everywhere

Yesterday I said this was the first time since being on NW (4 years?) that I could see a chance of a good dumping of snow for me within the reliable timeframe, then came tonight's charts. !!!!!

Taking into account plenty of IMBYism and for the next 48 hours I would say...

METO:- Excellent

GFS:- Awesome

NAE and FAX There is no superlative that I can conjure up, maybe 'perfect'?

And if there were two models I would like to see saying a big 'game on' for me it would obviously have to be these two.

I will no doubt be consoling myself in 3 days time that 'at least I saw snow in the reliable timeframe. on the charts

I have been gabbling on for a while about the instability involved here and the chance a small trough could form just beneath the Dorset coast, it hasn't yet of course but maybe it really could? And if it deepens then OMG, bullseye for some!

Edited January 4, 2010 by s4lancia

[kold weather]

The low is something that is going to be a pig for the models, esp as its effectivly a complex low which means there are several centers trying to become to the dominant one. The last few runs had the North Sea low beocming dominant, but the 12z today have swung it nback towards the Channel low....big practical differences.

Later on (FI) some big synoptic differences tonight with regards to the ensembles, a lot are willing to erase the pattern around the 14th but where have we seen it try that before?

[The PIT]

Well the cold spell here for the reliable time frame. In deep FI GFS shows the atlantic coming through which fits in the progressive nature of the 12oz GFS. We have too see what the ECM thinks of things in Deep FI later and see if they agree.

[casparjack]

My assumption was based on the operational charts, which are, as I said above, every so slightly warmer than the mean, and mostly warmer than the rest - so, hopefully, for all concerned, this pushes everyone (possibly not those in the west) to below the magic 2C.

Still it all seems a little close (doesn't it always!) so I'd advise caution and nowcasting!

This is the latest plotted chart that I can find, for 17:00 hrs.

Shows some CuNim, might indicate a bit of activity, heavy snow showers into Lerwick and sub zero, the front is definitely running into cold air, so we will have to hope that as per the earlier FAX chart the 'warmer' air gets mixed out and pushed West into the Atlantic.

I did read the replies above...

[Radiosonde]

Well the cold spell here for the reliable time frame. In deep FI GFS shows the atlantic coming through which fits in the progressive nature of the 12oz GFS. We have too see what the ECM thinks of things in Deep FI later and see if they agree.

Operational was big FI outlier.

GFS Ensembles London 12z

Edited January 4, 2010 by Radiosonde

[Snowaddict]

GEM 12Z Evolution also follows that of the 12Z UKMO to a large extent, with a renewed Easterly/Northeasterly flow. Pressure built well to the north out to T+144.

Excellent run again.

SA

[Coast]

This is the latest plotted chart that I can find, for 17:00 hrs.

Earlier, but gives projections for 24.00hrs:

[MR EXTREMES]

GEM 12Z Evolution also follows that of the 12Z UKMO to a large extent, with a renewed Easterly/Northeasterly flow. Pressure built well to the north out to T+144.

Excellent run again.

SA

if i remember rightly gp mentioned the gem and pressure built well to the north,

he also feels mid month is when more fun and games is expected.

i think the deep low is a little dramatic.

[Snowyowl9]

Well the cold spell here for the reliable time frame. In deep FI GFS shows the atlantic coming through which fits in the progressive nature of the 12oz GFS. We have too see what the ECM thinks of things in Deep FI later and see if they agree.

UKMO shows a scandi high then back to greenland high,GFS doesn`t know what to do.

http://www.wzkarten.de/pics/Rukm1201.gif

http://www.wzkarten.de/pics/Rukm1441.gif

In the short term GFS is excellent for snow and stronger winds now.

http://www.wzkarten.de/pics/Rtavn421.png

http://www2.wetter3.de/Animation_12_UTC/42_35.gif

[Joneseye]

I have been an avid model follower and fairly infrequent poster on this thread for a number of years. After looking at the 12Z GFS I felt compelled to post.

Maximum respect to any forecaster out there if they get their forecast spot on based on the models.. this winter has proved what a nightmare it is for the models to accurately model cold weather on the mesoscale level. Fair play to the experienced and cool heads on this thread that talk about getting the cold synoptics first!

'All of a sudden' the GFS develops a low pressure slap bang over the middle of England and the threat of a lot more precipitation at T36! The other models forecast along 'similar' lines but with slightly different locations for the main core of the precipitation and all the in the reliable time-frame. I bet the met office and highways agencies are tearing their hair out trying top get this right!

The term nowcasting is very much the name of the game at the moment and I shall be glued to the radar as well as the latest model runs.

[SMU]

507 DAM in the SE !!!!!!!!!!!!!

ITS BACK ON-- :o :o

UKMO & ECM especially back the heavy snow WIDESPREAD-

S

Edited January 4, 2010 by Steve Murr

[bluearmy]

ITS BACK ON-- :o :o

UKMO & ECM especially back the heavy snow WIDESPREAD-

S

but the metmen are going with the NAE steve which keeps the most precip around the shortwave near the IOW/central southern england towards bristol.

by the way, i always end up 4 dam out from your meteociel calcs - one of us is wrong reading the scale!!

Edited January 4, 2010 by bluearmy

[DEYS(Kent)]

That's for Fri, Blue

[TEITS]

A couple of things I want to say to anyone who is either excited or disappointed at tomorrows prospects.

First of all we do not have much agreement in the models for tomorrow. The UKMO suggests the main focus of snow will be in E Anglia. The NAE suggests S/Central/W England. The GFS is rather inbetween the UKMO/NAE. This is why based on the models I could see 1cm of snow or 30cm.

Im pretty certain this will change even into tomorrow morning. Probably best to assume areas of snow will affect much of England with the most favoured location being the S Midlands.

Even if E areas miss out they won't if the ECM is right!!

[scotto]

What has happened in the models to change the forecast of heavy snow in the north of england moving south in the afternoon on the BBC, to having hardly any over us and maybe 20-25 cm in the south. Weird how much differnce there can be in the space of a few hours.

[MR EXTREMES]

but the metmen are going with the NAE steve which keeps the most precip around the shortwave near the IOW/central southern england towards bristol.

by the way, i always end up 4 dam out from your meteociel calcs - one of us is wrong reading the scale!!

id say bigger swathe than that anywhere south of the midlands both east and west which makes a change,

but i say this without being downbeat i think location is not totally nailed,

and as people are saying its a nowcast situation.

so really anywhere within the southern england zone could get a real dumping either east south or west but either way its intresting and very exciting indeed.:lol:

i would say marginal is unlikely.

Edited January 4, 2010 by badboy657

[Barometric]

Great to see the 12z ECM on board along with the stunning 12z UKM. GFS doing its normal backtrack up to around 120. I'll be just sticking to these 2 Europeans from now on during this spell.

UKM had been in a word....SOLID!

James

[TEITS]

but the metmen are going with the NAE steve which keeps the most precip around the shortwave near the IOW/central southern england towards bristol.

by the way, i always end up 4 dam out from your meteociel calcs - one of us is wrong reading the scale!!

ECM at +72.

Fax at +72

http://www.meteociel.fr/ukmo/fax/fax72s.gif

Identical.

[Bristawl Si]

http://www.meteociel...CM1-96.GIF?04-0

507 DAM in the SE !!!!!!!!!!!!!

ITS BACK ON--

UKMO & ECM especially back the heavy snow WIDESPREAD-

S

Steve - what's your take on tom eve and Wednesday - has it become a nowcast event? Latest charts suggest South Midlands, Central S.England and into the S.W. I suppose by this time tomorrow it could've shifted back east. A nightmare for the UK weather forecasters, i'd imagine.

[kold weather]

but the metmen are going with the NAE steve which keeps the most precip around the shortwave near the IOW/central southern england towards bristol.

by the way, i always end up 4 dam out from your meteociel calcs - one of us is wrong reading the scale!!

Interestingly the NAE is a outlier with regards to what the other models show, the GME, GFS and the UKMO all focus the precip core further east...however the NAE has a better resolution so that balances that out very nicely indeed...therefore gotta be 50-50.

Anyway the ECM is a stonker of a run for Friday+Saturday, bitter cold with the perfect flow for driving the showers far inland...

GFS on its own with regards to the easterly tonight...

[TEITS]

Whilst everyone is saying the +36 fax is like the NAE but its very much like the 12Z GFS.

http://www.wetterzentrale.de/pics/Rmgfs361.gif

http://www.meteociel.fr/ukmo/fax/fax36s.gif

Watch what happens to the band of precip during Tues night.

http://www.wetterzentrale.de/pics/Rmgfs363.gif

http://www.wetterzentrale.de/pics/Rmgfs393.gif

http://www.wetterzentrale.de/pics/Rmgfs423.gif

Im not yet convinced tomorrow/Wed is going to be a W event. If the 18Z is similiar then come tomorrow I can see this risk being further E.

[cooling climate]

Excellent European models tonight with the ECM and the UKMO in sync with each other out to

t144.

I have just read the Meto extended forcast which suggests further heavy snowfall for the east

and south for the following week, incredible stuff.

Some areas from the Midlands south are going to get plastered tomorrow with 30+cm easily

within reach I think.

[nick sussex]

The gfs operational run continues to go it alone towards the bargain bin! more nonsense from this model tonight, it was slated this morning and i expect when NOAA do their evening update that it won't be used again.

Notice how as soon as a Scandi high is projected it's output goes AWOL, stick to the ecm and ukmo who are much more reliable with european blocking patterns.

Edited January 4, 2010 by nick sussex