Model Output Discussion:

[Guest Quantumsnow]

I've done some drawings this morning on the ECM charts to show members what they need to look out for in futher model runs.

Morning. Hope you do't mind me posting, I know it's off topic but wanted to say thanks for this, as a new member who is trying to learn what to look for in the maze of the charts posts like this are very helpful indeed. Thank you sir! sorry mods

[chionomaniac]

I've done some drawings this morning on the ECM charts to show members what they need to look out for in futher model runs.

Here is the +96 ECM chart.

I have highlighted the area you need to look out for. What we have here is called trough disruption although I tend to refer to this as a splitting LP. As you can see this shortwave starts tracking SE.

Moving onto +144. Look at (A) this is the SW that tracked SE at +96. Now B is the LP you see centred over Wales at +120. This also moves SE and because of this the HP C to our N is allowed to ridge S. The knock on effect of this beyond +144 is further SW track SE and the Atlantic trough (D) begins to back W.

As myself and Nick said the other day its either a mild SW,ly or a cold E,ly with no inbetween. Simply put the SW have to track SE rather than NE. If this occurs as the ECM shows then what happens beyond +144 is perfectly plausible.

A good post this, Dave. One of the reasons that we are seeing such variance at T+144 range is because of the variance in the models of forecasting the negative mean zonal wind propagation from the stratosphere. The forecasts are all over the place at the moment. I spotted this trend yesterday of increased energy in the southern arm of the jet stream but it was only very slight, but it was noticeable how the pressure rise from the azores was flattened out quickly with a lowering of pressure in the Med region. BFTP was saying look NW for pressure rises but the equal and opposite signal can be found to the SE!!!

[MR EXTREMES]

I've done some drawings this morning on the ECM charts to show members what they need to look out for in futher model runs.

Morning. Hope you do't mind me posting, I know it's off topic but wanted to say thanks for this, as a new member who is trying to learn what to look for in the maze of the charts posts like this are very helpful indeed. Thank you sir! sorry mods

hes a nice fella is our eye always helpfull and polite others to are very helpfull welcome anyway.

so make to the models sw tracking southeast would be great for building heights,

whats even better is a south tracking jet stream which is another plus.

im still not convinced about the strength of the alantic and them low pressure systems they look rather over cooked to me even to the point of bbq lol.

[TEITS]

Now the ECM ensembles are trending back towards colder weather. The 0Z ECM OP was bang on the mean for the entire run.

http://www.knmi.nl/exp/pluim/vijftiendaagse/Data/15DAAGSE_06260_NWT.png

However as we can see there is a large split between these. My advice is follow the operationals at the moment. Remember ensembles have the intial data tweeked and the only purpose of ensembles is to check how reliable the operational actually is.

[BLAST FROM THE PAST]

A good post this, Dave. One of the reasons that we are seeing such variance at T+144 range is because of the variance in the models of forecasting the negative mean zonal wind propagation from the stratosphere. The forecasts are all over the place at the moment. I spotted this trend yesterday of increased energy in the southern arm of the jet stream but it was only very slight, but it was noticeable how the pressure rise from the azores was flattened out quickly with a lowering of pressure in the Med region. BFTP was saying look NW for pressure rises but the equal and opposite signal can be found to the SE!!!

Hi C

The signal in my method is for the energy to go south and that models will pick up on this 11th hour as it were. Today and tomorrow are 11th hour, yesterday I went on and on about FI being T96 because the adjustment to the SW going SE and shown being too far NE. First step made by ECM, although fax output yesterday showed adjustments. Shortwave going SE due to preessure building to our N and NW and ridging down.

BFTP

Edited February 1, 2010 by BLAST FROM THE PAST

[MR EXTREMES]

Hi C

The signal in my method is for the energy to go south and that models will pick up on this 11th hour as it were. Today and tomorrow are 11th hour, yesterday I went on and on about FI being T96 because the adjustment to the SW going SE and shown being too far NE. First step made by ECM, although fax output yesterday showed adjustments. Shortwave going SE due to preessure building to our N and NW and ridging down.

BFTP

BFTP so it possible that high pressure could setup over us to start or not lol?

and if pressure builds from the southeast is that not a bad thing?

Edited February 1, 2010 by badboy657

[Cecil Hogmanay Melchett]

I really don't know whether to laugh or cry at the model output although im not actually that surprised if you read my post late last night.

The difference in the models this morning is they transfer some of the energy from the Atlantic trough SE rather thsn NE and this allows the block to the N to influence our weather. We then see the trough on the ECM back W but we also see further LP tracking SE. The UKMO might not be as promising as the ECM but even this is backtracking wrt to energy moving SE rather than NE.

I tell you what at the moment the outlook is very uncertain and whether you prefer cold or mild nobody can say either way at the moment. Ignore the ensembles because the operationals will show the way upto +144.

I will add that often the models are reluctant to show SW tracking SE until they enter the +72 timeframe. Why this is could be due to models always underestimating the blocking to the NE.

Well mate i know im classed as a doom merchant but i posted yesterday morning to say this is not over and i had a feeling something didnt ring correct.

We may see fronts pushing in through the week but if the block can divery enough energy SE then ANYTHING can happen.

The models have been very inconsistent lately,even ukmo has a different setup this morning with the main trough held well west of what it was yesterday.

fingers crossed for more upgrades and keep an eye on the 15 dayer dave.

[Frosty.]

Very nice ECM....now who said that beyond T96 is sorted. This ECM change is NOT a surprise to me...interesting to see where the models go from here. Remember, southerly jet to dominate, look N and NW for blocking developments..those are the signals I have and placed on my monthly update..T96 IS FI and the model output is certainly bearing this out. Patiently waiting for 12z and now 00z tonight.

BFTP

Hi Fred,

The ECM 00z is one of the coldest ensemble solutions I think and the gfs 00z will probably be nearer the mark in that it pushes milder air north across the whole of the uk before the cold air possibly starts fighting back during next week, the ecm fast tracks the return to cold conditions but I would say the gfs evolution is more realistic although I would love the ecm outcome. Also, the ukmo only seems to want to bring milder air with no return to cold unless I have misread the output. :unsure:

[Cecil Hogmanay Melchett]

Hi Fred,

The ECM 00z is one of the coldest ensemble solutions I think and the gfs 00z will probably be nearer the mark in that it pushes milder air north across the whole of the uk before the cold air possibly starts fighting back during next week, the ecm fast tracks the return to cold conditions but I would say the gfs evolution is more realistic although I would love the ecm outcome. Also, the ukmo only seems to want to bring milder air with no return to cold unless I have misread the output. :unsure:

I feel ukmo is fine at 144h frosty.Maybe im reading it wrong but id say there is a decent chance of blocking becoming the dominant player down the line as the trough fills against the block.

Definetly a flip back to colder posibilities this morning.

[chionomaniac]

Hi C

The signal in my method is for the energy to go south and that models will pick up on this 11th hour as it were. Today and tomorrow are 11th hour, yesterday I went on and on about FI being T96 because the adjustment to the SW going SE and shown being too far NE. First step made by ECM, although fax output yesterday showed adjustments. Shortwave going SE due to preessure building to our N and NW and ridging down.

BFTP

Morning Fred,

The signs were there yesterday it was just such a turnaround that some weren't looking for them (not you of course!). That is not to say that after a short mild interlude that we are definitely heading back to cold, but to write this avenue off could be foolish. After all the background signals of stratospheric warming (not an MMW by the way), MJO phase, deep eurasion snowcover etc have not disappeared overnight and therefore neither have medium term cold prospects. The displaced stratospheric vortex which is unfavourably positioned presently may have an important part to play in determining whether any northern blocking will bear fruits for us, but with the downwelling forecasts so volatile we may not know until it is almost upon us.

c

Edit - there are signs that the vortex positioning may be becoming more favourably positioned. If this is true then I would expect to signs of heights rises around Svalbard region.

Edited February 1, 2010 by chionomaniac

[BLOWERS]

I doubt pressure will rise from the S if we do see SW tracking S. If anything is the HP pressure to our N become influencial.

The period in question i.e +96/+144 really is impossible to forecast at the moment. However if the 12Zs go the same way as the 0Z ECM then the cold E,ly is back on.

TEITS, I think I know roughly what an SW is (part of a LP system?), but could you clarify/define for me, please?! I've looked everywhere in NW Forums, and Googled, all to no avail. Apologies for thickness (or should that be temperature?!)...

[cooling climate]

I've done some drawings this morning on the ECM charts to show members what they need to look out for in futher model runs.

Here is the +96 ECM chart.

I have highlighted the area you need to look out for. What we have here is called trough disruption although I tend to refer to this as a splitting LP. As you can see this shortwave starts tracking SE.

Moving onto +144. Look at (A) this is the SW that tracked SE at +96. Now B is the LP you see centred over Wales at +120. This also moves SE and because of this the HP C to our N is allowed to ridge S. The knock on effect of this beyond +144 is further SW track SE and the Atlantic trough (D) begins to back W.

As myself and Nick said the other day its either a mild SW,ly or a cold E,ly with no inbetween. Simply put the SW have to track SE rather than NE. If this occurs as the ECM shows then what happens beyond +144 is perfectly plausible.

Great post and well explained. I very much doubt the ECM is far off the mark at t120- t144 and who knows

we could have model agreement by this evening,with a very cold pattern becoming established by this

evening.

[Paul]

TEITS, I think I know roughly what an SW is (part of a LP system?), but could you clarify/define for me, please?! I've looked everywhere in NW Forums, and Googled, all to no avail. Apologies for thickness (or should that be temperature?!)...

This is a good site to bookmark for answers to questions such as the above :unsure:

http://www.theweatherprediction.com/habyhints/131/

[Southender]

Looks like big changes on the 06z so far...

[cooling climate]

This is a good site to bookmark for answers to questions such as the above

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

Quite agree, I have learned a great deal from this site.

Very, very good.

[Tom D]

February is potentially the most exciting part of winter (wrt snow potential). In the last few years (and in many of the 'classic' winter events), February has been the month where it's happened. Those people who were writing off winter (it was hard not to I'll admit ) after the milder runs came out (especially on the GFS) had no reason to do as it isn't unknown for winter to last well into March. We've had a brilliant winter so far and there's potential for cold conditions to last a while longer yet.

The posts today by TEITS are probably the best I've read on this thread! Thanks for those diagrams and posts, they're excellent and you clearly know your stuff better than most.

Interesting model watching ahead later today and for the next few days.

Edited February 1, 2010 by Tommyd1258

[BLOWERS]

This is a good site to bookmark for answers to questions such as the above

http://www.theweatherprediction.com/habyhints/131/

Brilliant! Many thanks. Sorry if I posted in wrong forum...

[Duane S.]

I feel ukmo is fine at 144h frosty.Maybe im reading it wrong but id say there is a decent chance of blocking becoming the dominant player down the line as the trough fills against the block.

Definetly a flip back to colder posibilities this morning.

I'd agree with that HD. The METO was the first 00z I looked at (my morning quickly improved as my next port of call was the ECMWF!)) and I was very pleased with the +144. There is a window of opportunity there for sure and is certainly an improvement on some showings from the METO charts of late.

[Rollo]

I wold agree signs of hope but other than the ECm the GEM is not good and GFS is not great at the moment-this is a situation that will go down to the wire(seems to be a lot of that this winter) and it really is a case of wait and see. Just to say how much I enjoy "Eyes" optimism.

[cooling climate]

There are big enough changes on the 06 run out to t150 to think that the 0z ECM

run is on the money and we could have some excellent charts to look at this evening.

[TEITS]

Clear to see the 06Z isn't going to be like the ECM.

The model output is so volatile at the moment its incredible. I normally prefer the ECM between +120/+168 due to its consistency as this timeframe is outside the fax charts. However the sheer contrast between yesterdays ECM runs and the 0Z is the greatest I have ever seen in 6yrs!

The uncertainity is likely to continue but if the 12Z ECM continues with the same trend then I feel the others may follow. However the models need to resolve the extent of the blocking and also the atlantic trough. These two features are causing the models severe headaches including myself!

Worth mentioning that Feb 7th to 14th is also known as one of the Buchan spells. I think the next one is during April.

[D KARLSON]

Very nice ECM....now who said that beyond T96 is sorted. This ECM change is NOT a surprise to me...interesting to see where the models go from here. Remember, southerly jet to dominate, look N and NW for blocking developments..those are the signals I have and placed on my monthly update..T96 IS FI and the model output is certainly bearing this out. Patiently waiting for 12z and now 00z tonight.

BFTP

I think if the UKMO went out to 168 it would be similar to the ECMF at 168 but obviously UKMO arent as daft as to predict that far out.

If we start with the big picture the deep cold pool over Europe starts pushing east and this meets and this is the important bit ,the very cold pool of air over Russia amd that starts moving west once again ,this will be the trigger or mechanism which will spill the cold air once again to our shores,

As is typical in this kind of cold winter cold air is never far away and only ever recedes to come back at a later date.

Keep man eye on UKMO tonight it should continue with the theme of cold air returning and if it does were quids in for another cold outbreak ,i would say it looks as good as 60% to 70% at the moment and as i said earlier this is a common theme during cold winters so bias is always toward cold .

Another thing to add is; how cold will this possible cold spell be,well theres a fair a chance of it being severe and february does have a habit of this and would not be surprised at all if the cold continued well into March

[TEITS]

I know this chops and changes by the week, and going by the models and posts on here, this will prob be well out of date by the next set of runs but anyone else seen the latest BBC monthly outlook updated 10am today:-

http://news.bbc.co.uk/weather/forecast/10209

Seems confident of 'milder this week then v v cold'

Shame this weeks update wasnt done by Rob M

Thanks for posting this because it relates to what I was about to post.

Yesterday I was very surprised at the Met O 6-15 day outlook because it was far colder than any of the models/ensembles suggested. Now i've always maintained than the trick of forecasting with the models is knowing when they are right or wrong and that you have to use your instinct. After reading the above and yesterdays 6-15 forecast it appears neither the BBC/Met O ever believed the very mild SW,ly model outputs. Very rare to see forecasters going against the model output but this seems to be the case at the moment.

I will add that I don't want anyone thinking im assuming the cold E,lys will definitely arrive. What I am saying is the 12Z ECM/UKMO could show either a mild SW,ly or a bitter E,ly and it really is that uncertain.

[nick sussex]

Well another day and another model drama looks like beginning! The ECM is of course the pick of todays models and the UKMO is looking okay, as for the GFS 00hrs run in future I've decided this model only takes a supporting role, I have lost all faith in its output as it swings from one scenario to another, notice how once it dropped the easterly it went to the other extreme with the most zonal set up.

The models generally agree on a trough to the west but disagree how far east this is and how long it will take to fill and disrupt, the ECM is the quickest to do this and sends a shortwave east to the south of the UK which is the trigger to the change to colder weather however given the UKMO has been the one model with the right trend over the last few days, although it was a little too progressive then we should view this as a decent middle ground solution for the timebeing between the ECM and the GFS.

The effects of the current reverse zonal winds are causing alot of uncertainty and we're still not sure where the PV will go and for this reason we're likely to see continued volatility. IMO for the timebeing the one thing to keep an eye on is the Atlantic trough, the further west and south this is the much better chance of a quicker return to colder weather as the signal remains for blocking to the north and ne.

So overall some positives this morning but given the last week i think we need to be cautious about getting too excited just yet.

[Wayneywoo]

First time in a while we've seen mean height agreements between ECM/GFS...

http://www.meteo.psu.edu/~gadomski/ECMWF_0z/hgtcomp.html

Ooooo.......don't you just love the thrill of it all