Winter Model Discussion - The Hunt For Cold -18z 17/12/12

[TEITS]

Exactly what peter gibbs thinks, but what do you mean by most of us? does that mean you think it will be cold somewhere in the uk on christmas day?

Have to be honest im not sure how you can base a forecast for xmas at the moment using the anomaly charts. As I posted earlier at +144 the placement of the LP is massively different on every model at +144 and of course xmas day begins at +168. If the LP is situation to the W or NW of the UK then obviously the outlook is mild SW,lys. However if the LP tracks E i.e GFS then you would pull in colder N/NW,lys around xmas day on the backside of the LP.

Those anomaly charts are useful when it comes to the overall pattern but you cannot use them to predict our weather on the surface of our tiny island.

ECM ensembles continue to show massive scatter very early on.

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

Edited December 18, 2012 by THE EYE IN THE SKY

[bobbydog]

forget the models, it's going to snow. i saw 3 fallow deer in a field this morning, one of them was completely white!! an omen......

[Gowon]

I think some members need to read JH's post again, especially his last sentence.

[Southender]

Have to be honest im not sure how you can base a forecast for xmas at the moment using the anomaly charts. As I posted earlier at +144 the placement of the LP is massively different on every model at +144 and of course xmas day begins at +168. If the LP is situation to the W or NW of the UK then obviously the outlook is mild SW,lys. However if the LP tracks E i.e GFS then you would pull in colder N/NW,lys around xmas day on the backside of the LP.

Those anomaly charts are useful when it comes to the overall pattern but you cannot use them to predict our weather on the surface of our tiny island.

ECM ensembles continue to show massive scatter very early on.

http://www.knmi.nl/e...E_06260_NWT.png

Indeed. Good to see a very cold cluster from just 3 days out.

All to play for.

[johnholmes]

I think some members need to read JH's post again, especially his last sentence.

yes it is rare that folk read anything carefully and completely on here I am afraid but thanks

[TEITS]

yes it is rare that folk read anything carefully and completely on here I am afraid but thanks

I read all of it but I disagree.

My main point is I don't know why you are posting anomaly charts. At the moment these are pretty useless in the same way as using the ensembles are. Even at +48 we are seeing differences in the modelling of the shortwaves, especially the 2nd one developing underneath the main low. The track and depth of these could impact what happens afterwards We then have the massive difference at +144 and the positioning and track of the LP could mean the difference between +10 temps on xmas day or struggling to get above freezing.

The best way of forecasting is to just look at the +0 to +144 and then using some instinct as to which model is most likely to be correct. As you will agree back in the olden day when we couldn't rely on computer models then forecasters used their forecasting experience. These days we have far too much reliance on computer models.

A good example is Oldmanmet who suggested what the GFS is showing this morning a few days ago by using his forecasting experience and instinct.

Edited December 18, 2012 by THE EYE IN THE SKY

[Rollo]

The major problem as I see it is that in situations like the one we have at the present whan very few miles can make a huge difference to our tiny country,we end up (or some do) taking each run as gospel and it has become quite a trying experience. No such problems tend to occur when the weather is moving east/west which is the norm but what we have is unusual in that in occurs infrequently and the super computors just cannot really handle the small areas we are interested in. If for instance the Russian high bugs you and as a lot of members now say then give the charts a rest for a few days.

[Summer Sun]

ECM has plenty of potential this morning with northern blocking in place

Maybe a white and cold New year

[TEITS]

NAE at +48 is quiet different.

http://expert-images.weatheronline.co.uk/daten/proficharts/en/nae/2012/12/18/basis06/euro/pslv/12122006_1806.gif

Again the track of these SW is key. Look at the one in the Atlantic underneath the LP. Now if this is deeper and further S then this impacts the Iberian ridge. This impact can then affect the track of the LP as we see two LP systems phasing together.

So it isn't anomaly charts or ensembles means that you should be looking at but a much closer timeframe and these tiny, yet relevant details.

[johnholmes]

Those anomaly charts are useful when it comes to the overall pattern but you cannot use them to predict our weather on the surface of our tiny island.

well at least I have made some progress as for a long time you would not even accept that.

I wonder how you think the surface chart on the Fax is prepared?

Do you think there is use of any upper air data including possibly anomaly charts be they at 500mb or any other level?

[Summer Sun]

A white Christmas is back on for some according to the 00z

[Shunter]

06z Op further south again at T108. Looks like the Trough is gonna slide under the Eastern block.

[swfc]

Well at 120hrs the atlantic low is really winding up and not stretched!!!hmmm im thinking it will now go north east?

Edited December 18, 2012 by swfc

[TEITS]

well at least I have made some progress as for a long time you would not even accept that.

I wonder how you think the surface chart on the Fax is prepared?

Do you think there is use of any upper air data including possibly anomaly charts be they at 500mb or any other level?

I've always accepted the anomaly charts but its how I use them that seems to differ.

I tend to look at the anomaly charts for the medium range and only then as a general guide to the overall pattern. I certainly don't use them for the +0 to +7 day period. The same applies to the AO/NAO forecasts, ensemble means because at the end of the day they are all based on the same model data i.e ECM, GFS etc.

My own instinct is telling me the GFS is right here with regards to the LP because a few days ago I said pretty much the same as oldmanmet with regards to this LP. The movement E synoptically makes more sense and I wouldn't be surprised to see the 06Z go the same way as the 0Z. A white xmas for some remains a strong possibility.

[LomondSnowstorm]

Exactly what peter gibbs thinks, but what do you mean by most of us? does that mean you think it will be cold somewhere in the uk on christmas day?

I would imagine there will be at least some snow on the ground somewhere unless it gets incredibly mild, I mean we do have 4000 feet high mountains which are often snow capped throughout the years. There's still that outside shot of some kind of colder flow for Christmas and the GFS control does follow the op so I wouldn't rule some more widespread snow out.

[latitude]

ECM has plenty of potential this morning with northern blocking in place

Maybe a white and cold New year

Wheres the Northern Blocking? Cant see any over Greenland if thats what you mean?

[kold weather]

Really worrying looking 06z GFS, and I'm not talking about cold.

Its the amount of rain, especially for some western parts that is reall concerning. We are pretty much in a battleground set-up but by in the large the wrong side. Two highs to the north and south means any forntal zopne will have to slide westwards through the gap so to speak, but the main upper low is anchored in place, which means everything is going to be aimed right at us for 3-4 day period.

I'm fully expecting flooding to be a major isse come Sunday-Monday.

[Gavin Hannah]

The GFS 00z pulled the dreaded Euro High out it's hat post Xmas. Nooooooooooooo.!!!

Unfortunately, I've haven't seen any improvement in the output from last week. With yet again, only FI hinting at cold and a change in pattern.

One would think that after such a good year for being British, we may have got a bumper winter from the Jolly Fat man, not a lump of coal?!

[TEITS]

So the 06Z continues from the 0Z in taking the LP E.

http://www.wetterzentrale.de/pics/Rtavn1621.png

The difference what happens on Xmas day and beyond really is significantly different on the GFS compared to the ECM/UKMO.

[Schmalex]

One would think that after such a good year for being British, we may have got a bumper winter from the Jolly Fat man, not a lump of coal?!

To be fair, we are only 18 days into winter, with 2 1/2 months to go and Jan and Feb are, traditionally, the UK's best chances of cold and snow. I wouldn't be writing winter off yet by a long way.

Edited December 18, 2012 by Schmalex

[seabreeze86]

I think people need to look at the trend we have developing. Just to highlight the GFS we have consistently seen push the Azores high further south and become less of a player around the start of the xmas period. This is allowing the low to move east instead of north east. The exact track of the low and the shortwaves that develop with it will not be decided for a few days yet.

All in all great model watching.

[LomondSnowstorm]

Interesting to note the shift in short term output: the BBC forecast yesterday had the band of rain moving into northeastern Scotland by tomorrow evening, and now it doesn't even make it across the Forth before 6am on Thursday on the NAE.

Edited December 18, 2012 by LomondSnowstorm

[Dampdorset82]

I think people need to look at the trend we have developing. Just to highlight the GFS we have consistently seen push the Azores high further south and become less of a player around the start of the xmas period. This is allowing the low to move east instead of north east. The exact track of the low and the shortwaves that develop with it will not be decided for a few days yet.

All in all great model watching.

Exactly, the pattern change over the Xmas period has changed alot. The upgrades for the reliable are good the AH is moving south as you say to allow the low pressure to move east. I wouldnt be suprised by the time the 18z roles out there will be a few suprises for Xmas day!

[johnholmes]

when you are looking at rainfall outputs do remember that in order of difficulty

1=rainfall

2=temperature

3=upper air pattern

and that is true for any time scale be it 12 hours or 12 days or even further out.

[No Balls Like Snow Balls]

Exactly, the pattern change over the Xmas period has changed alot. The upgrades for the reliable are good the AH is moving south as you say to allow the low pressure to move east. I wouldnt be suprised by the time the 18z roles out there will be a few suprises for Xmas day!

Do you mean we will find out it wasn't santa drinking the sherry and eating the mince pies after all

Edited December 18, 2012 by No balls like Snow Balls