Winter Model Discussion 18Z 19/1/13 onwards.

[NorthernRab]

To me, the spread on the ensembles isn't quite considerable enough to rule out a slight warm up, but HL blocking is tricky to forecast. The Scandinavian ridge will probably hold I think, not dissimilar to the way shown here:

Edited January 19, 2013 by shuggee

[Jason M]

Ensemble watch then

At 120 hours lots of very good ensembles

At 180 a still some great charts but a clear split occurs.

Option 1, we stay very cold

Option 2, UK is destroyed by GFS superstorm

I kid you not, it really is that bizzare !

Jason

[bradymk]

Math is what makes the models, however there an infinite of solutions from what the chaotic weather will be like in 2 weeks, and one out of the Fi charts will be right but its finding which one is the question. Its like trying to know what you will be doing at this exact time in 2 weeks time, there are infinite of solutions!

FI is pretty useless regarding any detail and very rarely do charts verify. I do however when viewing the models look for key trends out in FI which it can be useful for to help try to find out what the pattern will be 10+ days time. For me, good guides to seeing the pattern within 10+ days in FI is using GFS, ECM and CPC anomaly charts. Although not good for detail, they are the best tool to try help predict the overall pattern out in FI. Anyway, GFS 18z sees the block putting up more of a fight with only a brief milder period but it does look like eventually the atlantic will make inroads into much of the country with less cold conditions but coldest in the north and east. When this happens is still up for discussion, but all models do show a less cold period beginning the end of next week atm. Whether the cold is extended a few more days in my opinion is still very much an option and the changes to the UKMO model in the faxes was encouraging. All this is even if the models are right in a breakdown but for now, a very cold week to come, with more snow opportunities followed by less cold from the weekend but for how long? not too long i reckon.

CFS showing this well. Week 1 staying cold with low heights to the south and higher heights to our north and north east. Week 2 shows the less cold period with lower heights and a trough to our west bringing up milder air. This backed up by CPC anomaly charts also. Charts week 3 and 4 show the potential for the cold returning with heights to our NW and lower to our south once again.

[TEITS]

If you want a classic example of how uncertain the outlook is then look below.

Latest Fax is nothing like the UKMO model.

Joined this forum in 2004 which is when I started viewing the models and I have never seen this occur before. I have seen slight modification but never to this extent.

[nick sussex]

The UKMO 120hrs fax chart shows alot of modification from the raw output:

Good to see the UKMO don't think much of their raw output as it was game over for the cold.

We still need to see the raw output change tomorrow morning but good to see these changes which suggests MOGREPS is more bullish for keeping the cold a while longer.

[Bonjangle]

If you want a classic example of how uncertain the outlook is then look below.

http://www.meteociel...x120s.gif?19-12

Latest Fax is nothing like the UKMO model.

Joined this forum in 2004 which is when I started viewing the models and I have never seen this occur before. I have seen slight modification but never to this extent.

Still on a learning path here .

Do this mean lots of rain and wind .

[Panayiotis]

The UKMO 120hrs fax chart shows alot of modification from the raw output:

Good to see the UKMO don't think much of their raw output as it was game over for the cold.

We still need to see the raw output change tomorrow morning but good to see these changes which suggests MOGREPS is more bullish for keeping the cold a while longer.

Weird none of the ensembles showing anything like what the UKMO are suggesting are they hiding something from us or will they be wrong?

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=120

Still on a learning path here .

Do this mean lots of rain and wind .

Nope actually quite the opposite the H to the NE shows high pressure which means there will be settle conditions across the UK, however it will feel cold with a light SE wind bringing cold uppers from mainland Europe. Edited January 19, 2013 by Panayiotis

[Paul T]

Just for the record, with regard to the Mega low everyone has picked up around 144hrs;

There is currently a 948mb Low sat in the Atlantic, and its doing sod all in terms of removing the cold.

I still dont buy a SW'rly breakdown next Thursday, I said it earlier and was accused at clutching at straws, but the 18z has indicated a little more potential for cold prelonging.

This time tomorrow im hoping to read poeple saying the that ''The models had a wobble yesterday, but it seems the cold is here to stay''

[nick sussex]

Weird none of the ensembles showing anything like what the UKMO are suggesting are they hiding something from us or will they be wrong?

http://www.meteociel...&mode=1&ech=120

Nope actually quite the opposite the H to the NE shows high pressure which means there will be settle conditions across the UK, however it will feel cold with a light SE wind bringing cold uppers from mainland Europe.

Yes that 120hrs is a very cold chart with that continental flow. The UKMO haven't just modified their raw output they've ditched it completely.

But we're not out of the woods yet as for some reason that raw output came out with a very progressive run and we need that to backtrack tomorrow morning.

Overall still alot of uncertainty as to when the cold spell will come to an end.

[chionomaniac]

If you want a classic example of how uncertain the outlook is then look below.

http://www.meteociel...x120s.gif?19-12

Latest Fax is nothing like the UKMO model.

Joined this forum in 2004 which is when I started viewing the models and I have never seen this occur before. I have seen slight modification but never to this extent.

Blimey - that is quite a difference and worth putting the charts side by side.

A delay to the cold leaving if that occurs - makes you wonder what the UKMO ensembles show!

[Racing Green]

Just for the record, with regard to the Mega low everyone has picked up around 144hrs;

There is currently a 948mb Low sat in the Atlantic, and its doing sod all in terms of removing the cold.

I still dont buy a SW'rly breakdown next Thursday, I said it earlier and was accused at clutching at straws, but the 18z has indicated a little more potential for cold prelonging.

This time tomorrow im hoping to read poeple saying the that ''The models had a wobble yesterday, but it seems the cold is here to stay''

Exactly, there's enough in the models to suggest as much. Mother Nature hasn't even decided if the cold is here to stay yet, but some on here have already made their mind up.

[Carlrg]

People making their minds up and just stating what they see in the models are totaly different. Please don't confuse the 2.

[bradymk]

Blimey - that is quite a difference and worth putting the charts side by side.

A delay to the cold leaving if that occurs - makes you wonder what the UKMO ensembles show!

Backed up by the 6-15 dayer which says less cold and unsettled weather not arriving until the beginning of next week. The potential is certaintly there in the models for the cold spell to extend a few days more, only model not to show this potential was UKMO which has clearly been ditched looking at the difference there! ECM with a few tweaks could be very different at 168. We will see what the 00z bring. But this looks like it could be another period where we won't have a good idea until under t+96.

[Jason M]

Blimey - that is quite a difference and worth putting the charts side by side.

A delay to the cold leaving if that occurs - makes you wonder what the UKMO ensembles show!

If they are similar to the GFS ones some will be pretty tasty :-)

[Catacol]

From the last thread:

"Catacol,

I'm confused by your Phase 8 composite. I thought the best MJO phases for Greenland blocking were sectors 8 and 1?

Surely if the MJO moves into a highish amplitude phase 8 then the chances of proper Greenland heights increase?"

I'm an out and out coldie, so hope I'm wrong... but some of the GFS MJO plots have the MJO entering phase 8 before the month's end (though a minority admittedly) and the Jan phase 8 composite here:

does rather mirror some of the current output and cpc anomaly data with a signal for low pressure out west and SW winds as a result.

However phase 8 for February is very good indeed:

so I'm probably worrying over nothing. I think I'm just grumpy because it is so damn cold and yet I'm looking at about 2 lumps of ice and a few bits of white on the odd tree branch. The snow fell in earnest about 15 miles north of here, but I fell on the wrong side of the proper snow line by a hair's breadth, and exactly the same happened last February. If it warms up before it snows down here in the SW I will spit.

[Thundery wintry showers]

I feel that a change to milder and moist weather from the south-west is likely at some stage during the second half of January, but it may well only be temporary. The breakdown shown by the ECMWF operational run and the GFS 18Z is far from convincing now- indeed the GFS 18Z has most of Scotland and northern England in cold continental air right through until the end of next weekend.

Of significance is the tonedown of the milder 850hPa temperatures. Here was the GFS 06Z projection for 12Z on Tuesday:

http://cdn.nwstatic..../h850t850eu.png

...and now tonight's 18Z:

http://cdn.nwstatic..../h850t850eu.png

Although the UKMO/ECMWF have shown some movement towards this morning's GFS runs, it seems to me that the GFS has shown more movement vice-versa. This is important because it means that, on the evidence of current runs, most inland parts of the UK should have frontal snow tomorrow night followed by snow flurries for eastern areas late on Monday and into Tuesday, with sleet/rain largely confined to the far south of England and eastern coastal counties. This could mean a spell of raw sleety weather and gradually thawing slush/ice in the latter areas- the sort of weather that our media infuriatingly calls "a vast improvement/welcome respite", but at present none of the major models are forecasting those conditions to affect more than a limited slice of the UK.

Another frontal system is forecast to move eastwards on Thursday followed by more fronts straddling the country on Friday. These will turn conditions more marginal for snow the further south you are, but inland areas on the northern and eastern flank of the systems have potential to see yet more snow from them.

Edited January 20, 2013 by Thundery wintry showers

[LomondSnowstorm]

Quite a stunning example of the need for human judgement in weather forecasting:

00Z +96:

+120 FAX:

A very nice run in the short term, good cold pool across the UK for the entire +72 period and the -8C isotherm gets no further north than the central belt.

Quite where we go from here will remain open to debate but there's certainly a greater chance of a further prolonging the cold than there was 24 hours ago:

[ukpaul]

NAE bringing snow from the Northern flank of the channel traversing system on Monday to the South East.

Uppers -5/6, DP 0/-1, Temps 0. All very marginal but with 48 hours to go it could go any way.

Edited January 20, 2013 by ukpaul

[Cecil Hogmanay Melchett]

pretty poor 0z runs so far today,the profile to the North west has been absolutely awful since about November and SSW or not it continues to look awful.

Maybe my fixation with Greenland height rises is related to my location,its the best for the north west as we saw in 2009 and 2010,the trouble is i dont think ive seen a Greeny high since then.(oh hang on yes i have,i see great big whopping ones every june and july).

What a sodden climate we have here,not.

Edited January 20, 2013 by happy days

[snow drift]

Much can change but this looks like being an interesting 48 hrs or so.

[dingdong]

Much can change but this looks like being an interesting 48 hrs or so.

For the north east maybe, that chart does not show any more snow over the bulk of the country as what is does at +0z

[snow drift]

For the north east maybe, that chart does not show any more snow over the bulk of the country as what is does at +0z

Sussex, Kent, Hampshire etc

Edited January 20, 2013 by snow drift

[IDO]

GFS op last night was a cold option compared to the ensemble mean whilst the 0z today is a milder variance:

18z: 0z:

Breakdown looking the favourite still, but precise details are still to be pinned down, and it may be a case of a north/south split as to this change. UKMO seemingly now leading the models for an early breakdown. ECM also on board for late next week with a v.poor FI:

Similar to December; a Russian High and the UK on the end of the zonal train. Not much sign of the results of the SSW here with a strong PV remaining to our W/NW. That could take some shifting, so early Feb not looking promising with a chart like that. GFS similar at T240:

A week later the GFS has poor blocking to our north:

I assumed the propagation would start to show by the 5th Feb so either it isn't going to happen by then or GFS are wrong (more likely bearing in mind what the experts are saying). Though it is worrying GFS are churning out poor FI runs when a major trop event is about to happen.

[bluearmy]

Well the gem sits isolated this morning. Although it can often pick a pattern change, methinks holding onto the current one and introducing something akin to 79/80 is probably barking up the wrong tree. Shame.

[Gustywind]

Yes looks fairly nailed on now that the cold spell ends by Friday. Longer term the lack of high level blocking is the key worry in terms of a quick return to cold. The latter ECM frames show a strengthening vortex around east Canada into Greenland. Looking at the northern hemisphere maps, the lack of blocking is a real surprise given all the noise around strat warming, favourable mjo etc. it seems despite all these positive signals the nao will remain neutral at best. What is it going to take to get pressure to rise over Greenland? Can one of the experts give a view as to what is causing this?