Model output discussion - 21st Jan Onwards

[knocker]

3 hours ago, EastAnglian said:

May be a stupid question and please feel free to move mods if inappropriate. But as there is the possibility of wintry/snow showers in the next week or so is it possible to calculate the lapse rate (change of temperature with altitude) from the model output and if so is there a beginners guide on the forum?

Hi EA

Yes it's possible but it's very rough and ready and not really of much use IMO. For example you could calculate a rough LR surface to 850mb taking the height and temp at 850mb from the output, the difference between that temp and the surface and calculate the LR in deg. C per K. You could also adopt the same method for intermediate layers but this time taking the difference in heights. But none of this would indicate changes of LR as one ascends. There is really no substitute for a sounding for identifying lapse rates so better looking for a sounding near you or one in the relevant air mass

There is a Simple Guide To Understanding Skew-T Diagrams which may be useful in this respect on NW written by JH which you may find useful

https://forum.netweather.tv/topic/16002-a-simple-guide-to-understanding-skew-t-diagrams/

Edited January 26, 2016 by knocker

[Nouska]

@EastAnglian

On Meteociel, the shorter range ARPEGE model offers cuts or soundings (coupes or sondages ) for the whole of the UK. It works on the same basis as the ensembles - click on the map and a new window opens with a range of timings and parameters in drop down menu.

http://www.meteociel.com/modeles/coupes_arpege.php?region=uk&ech=3&mode=2

http://www.meteociel.com/modeles/sondage_arpege.php?region=uk&ech=3&mode=2&wrf=0

The fact it is only up to four days should not matter as anything beyond that point subject to detail change.

[mb018538]

1 hour ago, MP-R said:

The following chart from the ECM 06Z can be described as 'effing shortwave'.

Not far off a northerly at all from that. I'm wondering if our cold anomaly in the north Atlantic is partly behind lows forming/intensifying so readily in that area?

The main driver behind that cold pool was the relentless cold being poured into that region all winter last year! It was almost non stop! According to NOAA there were 900 minimum temperature records broken in that winter. Pretty phenomenal stuff and certainly having a big cooling effect on the Atlantic region.

[Ravelin]

1 hour ago, chris55 said:

1 hour ago, MP-R said:

The following chart from the ECM 06Z can be described as 'effing shortwave'.

Am I missing something everyone else can see?

1 hour ago, chris55 said:

Im liking the last two frames of this mornings ECM, watch how the low just to the north of the UK dives EAST to WEST and rapidly strengthens, riding what must be a strong jet pulse coming straight out of the Acrtic.

I though that at first too, but I'm not convinced that system really is going East to West. I think the deep low to the West of the UK on the last frame could be a rapid deepening of the less than obvious low in front of the trough in the mid Atlantic on the previous frame. Difficult to tell in 24hr jumps and it'd certainly be far more interesting if you are correct and I'm wrong.

 

 

Edited January 26, 2016 by Ravelin

[Nouska]

1 minute ago, Ravelin said:

though that at first too, but I'm not convinced that system really is going East to West. I think the deep low to the West of the UK on the last frame could be a rapid deepening coming off the trough in the mid Atlantic on the previous frame. Difficult to tell in 24hr jumps and it'd certainly be far more interesting if you are correct and I'm wrong.

Just made a wee gif to have a look at this on the six hourly IMO charts.

[EastAnglian]

Thanks Knocker, now I know why we just used to use a rule of thumb, convective day 3-4 degrees per 1000 feet approx that seemed good enough back in my days walking over the Kittenish Weald and the Cumbrian fells on holiday. I will look at the reference you provided but learning new things now is slow 60+ years of satellite images and environmental and mathematical modelling and software Analysis has slowed the old grey matter down. 

 

I was carious because we live at 238m in a well known National Park and just wanted to get an idea of the temperature at the tops locally between 2000 and 2500 feet. I really enjoy weather watching and I wish I could interpret the models with half the competence of some on here, still good fun trying and thanks again for replying.

[EastAnglian]

Thanks Nouska I will enjoy looking at the links you provided.

[knocker]

1 hour ago, Nouska said:

@EastAnglian

On Meteociel, the shorter range ARPEGE model offers cuts or soundings (coupes or sondages ) for the whole of the UK. It works on the same basis as the ensembles - click on the map and a new window opens with a range of timings and parameters in drop down menu.

http://www.meteociel.com/modeles/coupes_arpege.php?region=uk&ech=3&mode=2

http://www.meteociel.com/modeles/sondage_arpege.php?region=uk&ech=3&mode=2&wrf=0

The fact it is only up to four days should not matter as anything beyond that point subject to detail change.

That's quite nifty Nouska. A useful addition to the woodshed library. Now where's the way out!

Edited January 26, 2016 by knocker

[nick sussex]

Given the comments from Ian F and the suggestion of the MJO being in a favourable phase in early February then this would suggest the GEFS cannot be viewed with much confidence.

The MJO divergence which was apparent during December is also the same now with the GEFS reluctant to go anywhere fast with the MJO.

The GEFS going on the latest update spends its next 15 days in phase 4. The divergence during December started off with the UKMO keen to go into phase 5 whilst the GEFS in particular didn't want to know, the UKMO was proven correct.

The GEFS were a complete failure and only picked up the MJO signal very late.

Looking at the outputs there does seem a strong signal to have the main PV towards Scandi stretching ne/sw. I think the issue for any colder conditions is the left over PV lobe in ne Canada. This makes any ridging in the mid Atlantic hard going.

I think we'll need to see any lobes located further nw to have a better chance.

 

Edited January 26, 2016 by nick sussex

[IDO]

9 minutes ago, nick sussex said:

Given the comments from Ian F and the suggestion of the MJO being in a favourable phase in early February then this would suggest the GEFS cannot be viewed with much confidence.

The MJO divergence which was apparent during December is also the same now with the GEFS reluctant to go anywhere fast with the MJO.

The GEFS going on the latest update spends its next 15 days in phase 4. The divergence during December started off with the UKMO keen to go into phase 5 whilst the GEFS in particular didn't want to know, the UKMO was proven correct.

The GEFS were a complete failure and only picked up the MJO signal very late.

 

 

 

 

^^^A couple of comments on the MJO signals. The latest MJO from NOAA also doesn't see much  "robust eastwards propagation". Early days to make a definitive argument either way but we have to remember the last one was (more than) helped by Storm Frank, so no repeat pattern banked even with a sustained wave; with other background signals blurring the picture.

 

[knocker]

38 minutes ago, EastAnglian said:

Thanks Knocker, now I know why we just used to use a rule of thumb, convective day 3-4 degrees per 1000 feet approx that seemed good enough back in my days walking over the Kittenish Weald and the Cumbrian fells on holiday. I will look at the reference you provided but learning new things now is slow 60+ years of satellite images and environmental and mathematical modelling and software Analysis has slowed the old grey matter down. 

 

I was carious because we live at 238m in a well known National Park and just wanted to get an idea of the temperature at the tops locally between 2000 and 2500 feet. I really enjoy weather watching and I wish I could interpret the models with half the competence of some on here, still good fun trying and thanks again for replying.

That's not a bad rule of thumb EA as it's assuming the DALR (dry adiabatic lapse rate) which is 3C/1,000 feet.

Edited January 26, 2016 by knocker

[nick sussex]

3 minutes ago, IDO said:

 

 

 

^^^A couple of comments on the MJO signals. The latest MJO from NOAA also doesn't see much  "robust eastwards propagation". Early days to make a definitive argument either way but we have to remember the last one was (more than) helped by Storm Frank, so no repeat pattern banked even with a sustained wave; with other background signals blurring the picture.

 

The colder spell during January was helped by the MJO. No disrespect to Michael Ventrice but he said the same thing about the last time the MJO was on the move saying it wasn't a proper signal and was being confused with Kelvin waves.

The NCEP update I read last night said that they expected an increase in amplitude of the MJO signal which at least takes it out of the COD.

The issue of course is whether MOGREPS is too bullish with this in terms of moving through the phases.

If we're going on recent events re which model got the initial movement correct it was the UKMO, the GEFS was useless and the normal 15 day ECM ensembles were slightly less useless.

[phil nw.]

Meanwhile out to T144hrs on both UK and gfs and a real squeeze on the isobars showing a vigorous westerly pattern.

Strong winds and gales are likely to feature over the next week or so as much as rain.Brief polar shots so Scottish highlands prone to some blizzard conditions in this pattern quite possibly.

[nick sussex]

So far the GFS 12hrs run looks similar to the earlier 06hrs run. Its a bit slower to split the PV over Greenland.

The UKMO is a bit different at T120hrs with a more amplified pattern over the central USA. It seems to take a shortwave at T96hrs and develop this into a runner low which crosses the UK, unfortunately we don't have the 6hr steps but if theres enough cold air for it to engage then chances of some snow on the northern flank of this.

You can see this feature here, on the T96hrs note the shortwave circled red:

This develops and runs eastwards and you can see this at T120hrs at the base of the troughing in Poland:

These features are difficult to pin down at this timeframe, it may not appear on the next UKMO run but something to keep an eye on in case its still there tomorrow.

Just done a quick check on the approx  850's for what that low might engage on the UKMO around -6. I think its current track would take the low across the Midlands, so northern flank of that around northern England.

This track might change and of course might just disappear in future outputs! As is the way with these sorts of set ups but anyway we'll see over the next few UKMO runs.

Edited January 26, 2016 by nick sussex

[BarnetBlizzard]

Is it me or are the charts slowly improving and the general model output not actually that bad. 

Yes- there will be cold rain, and wind, and yes there is no snowy easterly. 

However, these lows, usually tracking just to the North of the UK, are bringing shots of colder air across the UK, particularly the Northern half and there is no reason quite a few of you won't see some snow showers every now and again. 

For me the 12z GFS is better- heights in Europe less pronounced eventually and the start of an Atlantic ridge appearing. 

there is by no means a guaranteed cold spell on the way- but Meto and bbc did suggest something on the way in around 15 days time- lets hope!

[Rocheydub]

And in the realms of LaLa land in GFS, they produce a short lived cold northerly, would produce some low level snow up north and north west.

[nick sussex]

Its at times like this that I wish the UKMO went out to T168hrs.

The overall pattern it shows compared to the GFS at T144hrs suggests a stronger more amplified ridge could develop in the Atlantic and downstream could pull some colder air into the UK.

Edited January 26, 2016 by nick sussex

[Frosty.]

9 minutes ago, nick sussex said:

Its at times like this that I wish the UKMO went out to T168hrs.

The overall pattern it shows compared to the GFS at T144hrs suggests a stronger more amplified ridge could develop in the Atlantic and downstream could pull some colder air into the UK.

 

9 minutes ago, nick sussex said:

Its at times like this that I wish the UKMO went out to T168hrs.

The overall pattern it shows compared to the GFS at T144hrs suggests a stronger more amplified ridge could develop in the Atlantic and downstream could pull some colder air into the UK.

Yes I like the T+144 ukmo 12z too, would love to see the next frame if there was one..significant wintry potential once the trough to the north of scotland pushes further to the east. 

[northwestsnow]

Gfs flat as a witches !!

No suprise there from my pov- its cannon fodder material.

UKMO much more interesting at 144

[mountain shadow]

1 minute ago, Frosty. said:

 

Yes I like the T+144 ukmo 12z too, would love to see the next frame if there was one..significant wintry potential once the trough to the north of scotland pushes further to the east. 

Also,  why has the missing data area to the NW never been corrected?

[Frosty.]

4 minutes ago, mountain shadow said:

Also,  why has the missing data area to the NW never been corrected?

That's a really good question but I don't know the answer

 

 

[stratty]

 does this help?  

[northwestsnow]

The meteociel 144 ukmo shows how finely balanced it is, need to see that pain the backside euro high vanish off the stage then we really are in the game for upgrades !!

[chris55]

As we head into next week cold prospects with some snow are a possibility. UKMO has potential at 144. And although different at 144 GFS has a following short-wave on Wednesday, though at this range its pretty academic in terms of detail, still shows that the pattern is improving.

Channel Low! Snow a possibility on the northern edge of PPN.

 

Will be interesting to see where ECM sits tonight.

Edited January 26, 2016 by chris55

[Yarmy]

18 minutes ago, northwestsnow said:

Gfs flat as a witches !!

No suprise there from my pov- its cannon fodder material.

UKMO much more interesting at 144

The GFS is currently second only to the Euro at T144 with the UKMO in 3rd. 

The parallel is slightly better still (which is what you would hope).