Winter Model Discussion - Cold Hunting 08/01/13 00z Onwards

[Hammer]

Tonights 12z from ECM seems like it will give either further confidence in a more milder outlook, although perhaps mild is the wrong word, less cold. Or give renewed thoughts to a colder outlook. As I think others have said the period 15th January onwards looks very interesting indeed.

How did the ECM do the last time there was a SSW event similar to this?

[EML Network]

Might be worth keeping your eyes on this over the coming days...the Met Office LR Probability charts should be getting updated any day now

http://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/gpc-outlooks/glob-seas-prob

[Troubleatmill]

mmmm yes 06z ensembles not quite as good as the 00z with the mean in the mid to mid/long stage being less cold with the operational being one of if not the coldest. But defo not on its own.

the 12th to the 13th Jan is where FI starts ATM looking at these, As always........more runs needed lol!!!!

Edited January 8, 2013 by Nick JB

[Weather Boy]

In summary, UKMO latest goes for brief block; mostly dry & cold next week, followed into 10-15d period by increasing mobility with some rain-snow events from W, with heavy rain becoming more prevalent in SW as Atlantic comes more to the fore. However - and this is CRITICAL point - they stress Shannon entropy has now broken all previous records!! GFS solutions not mentioned in any analysis. Take from that they're leaning to EC but I do stress they acknowledge high state of model volatility, so it's a real poison chalice to be tasked with preparing any outlook summary so far ahead. Thus, major health warning on potential outcomes.

Could you (or someone else) be explain the term 'Shannon entropy' which I have not heard before today and what it breaking records therefore means in terms of a forecast? I'm guessing the word 'entropy' implies huge uncertainty compared to normal?

[Southender]

Could you (or someone else) be explain the term 'Shannon entropy' which I have not heard before today and what it breaking records therefore means in terms of a forecast? I'm guessing the word 'entropy' implies huge uncertainty compared to normal?

http://en.wikipedia.org/wiki/Entropy_(information_theory)

In short. The unpredictability of the unpredictable is unpredictable. Hope that helps!!

Edited January 8, 2013 by Shrimper

[Iceaxecrampon]

[

I do agree, its amazing chart for cold and snow showers or streamers into the east but do believe 2010 brought widespread snow....heck even i got some from a brief northwest incursion during it,

Saying that it is still an amazing chart and would take it anyday for pure cold lol! for me last nights 18z was the perfect winter chart for all, but hey its saying something about the outputs at the moment if we are even talking like this haha!!

And you are lucky where you are good buddy, i was up Catstye Cam a few weeks back and up to my knees in fresh powder snow

Catstycam NW Ridge then up Swirral - it's safer!

Yes 2010 did happen for the Lancastrians what a December! - this weekend the 06Z has an attack from the NW and the E when it is in the reliable I do not know surely one will deliver?

Ian

Edited January 8, 2013 by Iceaxecrampon

[mcweather]

In summary, UKMO latest goes for brief block; mostly dry & cold next week, followed into 10-15d period by increasing mobility with some rain-snow events from W, with heavy rain becoming more prevalent in SW as Atlantic comes more to the fore. However - and this is CRITICAL point - they stress Shannon entropy has now broken all previous records!! GFS solutions not mentioned in any analysis. Take from that they're leaning to EC but I do stress they acknowledge high state of model volatility, so it's a real poison chalice to be tasked with preparing any outlook summary so far ahead. Thus, major health warning on potential outcomes.

Obviously things are very fluid and volatile at the moment when essentially what Ian is saying that the METO don't even have much faith in their own outlook let alone anyone elses. The fact that this guidance has change so much from what they were saying at midnight last night tells us all we need to know.

[fergieweather]

EC suspect as mild outlier. Remember ensemble means will always tend to default to more energetic solution, hence more mobile. Current suspicion is a messy story next week followed by block re-established; critical thereafter is where we sit on side of jet as meridional pattern dominates. Noteworthy how EC temps for S Midlands remain at 2-4C max from weekend into foreseeable. Battleground events considered highly likely outcome in what will become an awkward forecasting mix next week onwards.

Edited January 8, 2013 by fergieweather

[ITSY]

Brief alternative update for those who witnessed the conversation last about the CFS ouput (giving even the middle east masses of snow which I said was ridiculous).

Israeli and Palestinian friends telling me snow is starting to fall with upto 6 inches expected even to lower Jerusalem levels by tomorrow night.

Maybe lets not rule CFS out completely then.

[The PIT]

Well for any mildies out there the ECM is a winner. Deep FI mild rubbish. Little support for it on the assemblies though.

[bluearmy]

given ian's comments re the massive uncertainty in the model output, i advise it isnt worth disecting the current output too much. just be entertained and wait for a pattern to come to the fore. looking at the london ecm ens temps, i suspect the se may be rather different to the majority of the uk if this mobility does become more prevalent.

[Robbie Garrett]

The further outlook doesn't get updated till 1600z, unless there are any major changes.

Hmmm, latest METO outlook not exactly brilliant. Seems they are leaning towards the Atlantic encroaching a bit further than the likes of the GFS suggest.

EDIT: Just seen Ian F's post. Massive uncertainty still. But perhaps the GFS is barking up the wrong tree at present.

[whitestuff]

Anybody know what the Shannon Entropy is and what it's effects are?

[Bobby]

In case anyone missed it earlier, from the GEM

A foot of snow across the South this Saturday anyone? Not without support in the GFS ensembles either.

Depending on how this front angles itself there is potential for a significant snow event across much of the country on the weekend as the GFS ensembles show. Something to keep an eye on at least.

Edited January 8, 2013 by Bobby

[ITSY]

Anybody know what the Shannon Entropy is and what it's effects are?

It means chaos and its effect is chaos

[ghrud]

Shannon entropy is the average unpredictability in a random variable.

Sorry just noticed others have already answered this.

Edited January 8, 2013 by ghrud

[ITSY]

In case anyone missed it earlier, from the GEM

A foot of snow across the South this Saturday anyone? Not without support in the GFS ensembles either.

Depending on how this front angles itself and where it falls, there is potential for a significant snow event across much of the country on the weekend, as the GFS ensembles show.

MO updates seem to suggest its unlikely, but worth keeping an eye on.

[NorthYorksWeather]

Also worth noting on the GEFS ensembles, both control and operational are above the mean 850hpa temp line at day 5 with most other member dipping towards -10, so some possible upgrades to come in terms of "how cold" for the weekend.

[Southender]

The further outlook doesn't get updated till 1600z, unless there are any major changes.

UK Outlook for Sunday 13 Jan 2013 to Tuesday 22 Jan 2013:

Current indications are for mainly dry, settled and cold conditions in most places on Sunday and Monday, with overnight frosts and perhaps some freezing fog patches, which could linger through the day in places. There may be showers in the east, turning increasingly wintry, with snow possible over hills. The far north and northwest may be cloudier, with rain or snow possible here later. Through next week, it is most likely to remain cold with further wintry showers, especially in northern, central and eastern parts, but also a good deal of dry and sunny weather, with overnight frost and fog. Towards the end of the period more unsettled spells of weather may spread from the west at times, with outbreaks of rain and milder temperatures possible.

Updated: 1139 on Tue 8 Jan 2013

http://www.metoffice...st_weather.html

Edited January 8, 2013 by Shrimper

[Dave Kightley]

Wouldn't it make sense that the GFS/ GEM would have a better handle of the jet coming out of the USA and around South of Greenland??? Considering there US models? The Signal is so strong on the models with SSW to.. Just doesn't add up.

[Met4Cast]

UK Outlook for Sunday 13 Jan 2013 to Tuesday 22 Jan 2013:

Current indications are for mainly dry, settled and cold conditions in most places on Sunday and Monday, with overnight frosts and perhaps some freezing fog patches, which could linger through the day in places. There may be showers in the east, turning increasingly wintry, with snow possible over hills. The far north and northwest may be cloudier, with rain or snow possible here later. Through next week, it is most likely to remain cold with further wintry showers, especially in northern, central and eastern parts, but also a good deal of dry and sunny weather, with overnight frost and fog. Towards the end of the period more unsettled spells of weather may spread from the west at times, with outbreaks of rain and milder temperatures possible.

Updated: 1139 on Tue 8 Jan 2013

http://www.metoffice...st_weather.html

Seems reasonable. Given the ECM stand on things and that there's more milder ensemble members in the mix on this mornings GFS I'd go with that outlook too. That's not to say it's all over though, we've seen many a time when ensembles finally "get" the pattern and they all suddenly switch to show a much colder outcome. I really hope todays ECM moves over towards the GFS, if it doesn't then that'll be three runs showing milder weather, then i'll start to get a bit worried

[Mark Bayley]

Theres certainly support for Greenland height rises in the last 3rd of the month, with a forecast strong amplitude MJO (phase 7), the GWO which seems to be on the move again and the continued effects of the SWW.

Which gives the following composite. The GWO is also on the move again, towards phase 4/5 which the composites show is associated with below normal uk temps

Edited January 8, 2013 by Mark Bayley

[UV-RAY]

Wouldn't it make sense that the GFS/ GEM would have a better handle of the jet coming out of the USA and around South of Greenland??? Considering there US models? The Signal is so strong on the models with SSW to.. Just doesn't add up.

Indeed it does, whereas the ECM is better at handling blocks to our East and NE.

[Snowman31]

given ian's comments re the massive uncertainty in the model output, i advise it isnt worth disecting the current output too much. just be entertained and wait for a pattern to come to the fore. looking at the london ecm ens temps, i suspect the se may be rather different to the majority of the uk if this mobility does become more prevalent.

Hi BA, what do you mean by different for the SE?

Danny

[Southender]

Hi BA, what do you mean by different for the SE?

Danny

I believe he is suggesting the SE of the UK may hold on to the colder conditions longer.

But it really is anyones guess at present.