The Seasonal Forecast Thread

[ZONE 51]

The Atlantic has been held back or squeezed for quite sometime, this has enabled a lot of energy to build up which is going to get released as a stormy spell. I expect things to settle down towards late Dec and very cold to widely return.

Edited December 12, 2012 by ElectricSnowStorm

[damianslaw]

The Atlantic has been held back or squeezed for quite sometime, this has enabled a lot of energy to build up which is going to get released as a stormy spell. I expect things to settle down towards late Dec and very cold to widely return.

The atlantic has in the main part been very weak all year, and has rarely got into third gear.. however, neither have we seen any lengthy dry settled high pressure period, instead 2012 has been the year of the stuck trough - taking up permanent residence over the country thanks to a southerly tracking jet and lots of northern blocking. There is no suggestion of the polar vortex setting up shop over Greenland anytime soon or indeed during the rest of the winter and therefore I don't foresee any atlantic steam trainof succesive low - but we once again are likely to have to endure a shortlived spell of thr trough languishing over the country - waiting for some amplification and eventual height rises to our north, suspect we will start to see this again around christmas with a very much colder pattern of weather setting in thereafter.

[Bristawl Si]

Yes, my hunch is defo a BUST!! LOL!!

That's why i rely on 30-second hunches and not LRFs - because i ain't got a scooby!

So, moving on - maybe we'll get to a 78/79 situ! End of year/turn of year 2013 to cold and blizzards?! Well, maybe not....!

After viewing latest output over last hour or so who knows?!

[keithlucky]

With the jet stream south of UK we should surely see North winds start to dominate UK weather

[Roger J Smith]

My updated look at index values suggests another brief shot of sub-freezing temperatures around 4-7 Jan then very mild at times in mid to late Jan, turning colder for a longer period in February lasting into early March. This continues to mimic the winter of 1946-47 and conditions are broadly similar across North America at this early stage of the season (over here, the concept of "climatological winter" is perhaps less dominant than in Europe, our experience tends to be winter fitting the astronomical season better, so in the psychology of the weather crowd the season hasn't really started yet, certainly the weather in eastern U.S. hasn't offered any signs of winter to date).

I would not want to say a repeat of 1947 but the season is taking on that sort of rhythm so if you could imagine a 50% intensity version of that epic winter, maybe that would be closer to what's possibly going to take place. On the other hand, after Dec 2010 there's no sound reason to believe that past records can't be at least equalled in modern times (CET within 0.1 of 1890 record).

[BLAST FROM THE PAST]

Hi Roger

That more or less answers my PM

BFTP

[AWD]

Don't think there will be anybody left by February.

http://en.m.wikipedia.org/wiki/Winter_of_1946–1947_in_the_United_Kingdom#section_2

Edited December 16, 2012 by AWD

[SnowObsessor90]

After viewing latest output over last hour or so who knows?!

And according to the 12z's it's off again, some of the posts in the MOD thread alone should tell you that Edited December 16, 2012 by Anonymous21

[damianslaw]

My updated look at index values suggests another brief shot of sub-freezing temperatures around 4-7 Jan then very mild at times in mid to late Jan, turning colder for a longer period in February lasting into early March. This continues to mimic the winter of 1946-47 and conditions are broadly similar across North America at this early stage of the season (over here, the concept of "climatological winter" is perhaps less dominant than in Europe, our experience tends to be winter fitting the astronomical season better, so in the psychology of the weather crowd the season hasn't really started yet, certainly the weather in eastern U.S. hasn't offered any signs of winter to date).

I would not want to say a repeat of 1947 but the season is taking on that sort of rhythm so if you could imagine a 50% intensity version of that epic winter, maybe that would be closer to what's possibly going to take place. On the other hand, after Dec 2010 there's no sound reason to believe that past records can't be at least equalled in modern times (CET within 0.1 of 1890 record).

This winter feels like 08/09 so far, which saw a cold end to November and cold first half to Dec, followed by a mild interlude before christmas, then a colder period end Dec and into January, before a more average spell of weather second half of Jan, then a cold period first half of Feb and then mild - a real topsy turvy winter.

However, if we were to see something akin to 1946/47 not saying we will, then it would beat Dec 2010 hands down in terms of the amount of upheaval it would bring.

Interesting thoughts. Would the mild/very mild second half of Jan be thanks to high pressure to our east and low to our west feeding in a mild southerly with the trough over the country, only then for either heights to quickly build to the NW behind a trigger low, or heights to the east retrogressing NW...

[Mark Bayley]

Here is my own thoughts for the rest of December, don't normally make forecast for the long range as im not that good but thought it might be fun to have a go!

Initial forecast summary

Overall im finding it rather difficult to produce a forecast, but then isn’t it always! What’s apparent is the PV shall remain disrupted and disorganised as we progress through December. I am generally supportive of height rises to the NE given the latest runs, although feel that these will transfer nearer Greenland as we progress through the month when we see further wave breaking disrupting the vortex and leading to more movement of the PV segments. This would also be supported by the GFS MJO outlook, and ensemble forecasts for the NAO from both the ECM and GFS. The CFS could also be included. Weatherwise a cold and unsettled start, with the potential for height rises to out NE, and some sort of easterly flow during the first third. As we progress into midmonth and beyond I feel higher pressure would transfer closer to Greenland, bringing a more N/NE’rly flow.

Review so far

The month started on a cold and unsettled note, while expected height rises to the north east materialised. Unfortunately we did not see the easterly flow that i expected, with low pressure from the west taking control, introducing unsettled weather with temperatures close to the average. Despite this the PV has remained disrupted, with a -AO and -NAO which has prevented us from experiencing something from winters past (i.e. Bartlett type weather). It’s apparent that my forecast of midmonth height rises over Greenland via retrogression from scandi will not materialise, and thus a north/north east flow.

Update and initial January thoughts

The following update and forecast is based on the latest stratospheric output, MJO, CFS, AO and NAO ensemble means, as well as 500hpa and 850hpa means.

Stratospheric outlook

Stratospheric temperatures at the 10hpa and 30hpa level are running just below the average, and have done since a small warming event at the beginning of the month. They are forecast to remain just below average for the next 10 days, with temperatures rising at 30hpa by day 10 (as shown on the ECM temperature charts). Note i have used the graphs for simplicity.

Although not as apparent on the temperature graph, a major warming at the 10hpa level is forecast from day ten onwards (Siberian sector), this is shown on the ECM 10hpa geopotential height charts at day ten, and the GFS strat charts.

The most significant warming is still out of range for the above charts, however the GFS 12z strat charts show this nicely, and have done for some time (and are not pushing back)

I suspect this will lead to major disruption of the PV, or the killer blow seen as its not exactly rampant at present. This would be expected as we progress into January. For the rest of December, I expect the continuation of the relatively weak PV, centred towards the Siberian sector, which opens up potential for further height rises over Greenland.

Zonal winds have risen slightly since a drop at the beginning of December, and are forecast to decrease again. Given their current and predicated strength I would expect the continuation of a weak(ish) PV.

Further wave breaking is forecast by day ten, most notable wave one. This should displace the PV, and further stress it. It is also noted that wave two activity shows signs of increasing, which would place even greater stress on an already strained PV.

MJO outlook

There seems consensus to progress the MJO into phase two, although not of high amplitude.

The UKMO is interesting in that wants to progress the MJO through higher amplitude phase one beforehand, which would give the following composite which has height rises over Greenland and a trough over the UK (although bear in mind these are to be used as guides).

The composite for phase two MJO is the following

A trough with the core of lower heights situated over the UK (i.e. unsettled)

CFS charts

Weeks one and two show a trough situated in the Atlantic, unfavourably for us, leading to unsettled and probably mild (at times), weather. Looking at all forecasts from Sunday 9^th there seems a trend for height anomalies to continue above the norm around Greenland as progress past xmas day and into new year, with the core of lower heights transferring from the Atlantic into Europe. This would open the door to something a little more seasonal (e.g. northerly airstream).

AO and NAO Ensembles

The ensembles support the continuation of a –AO, although trending towards positive as we move towards months end and then negative again.

Further to this there is support for the continuation of a mostly –NAO, although trending towards positive for months end.

Mean height ensembles

The ECM ensemble mean supports the continuation of higher pressure to the north (Greenland area) and the core of lower heights in the Atlantic, with the continuation of unsettled weather.

Analysis of the 850hpa anomalies would indicate that temperatures should remain close to average, despite being unsettled.

The GFS is similar, although perhaps more interesting by day ten to fifteen, with the core of lower heights into Europe and indication that UK might experience something a little more seasonal (i.e. some sort of northerly) past xmas day.

This is also supported by the NAEFS

Overall

I expect the continuation of unsettled conditions, with on average temperatures remaining close to the norm. Given the expected continuation of a –NAO, and –AO I would not bet against colder interludes, in the form of brief northerlys, as we progress through the xmas period (something which has shown around xmas day on the latest model runs). I do not see great support for something prolonged this side of New Year. Given developments in the stratosphere I think the first half January, probably past week one, is when it could potentially come very interesting..!

Edited December 16, 2012 by Mark Bayley

[TwisterGirl81]

I agree Keith Lucky, the Jet Stream has been to the south of the UK which in my mind would bring cold and snow and we havent seen any in South Devon

Edited December 17, 2012 by TwisterGirl81

[Sean19]

If this is what winter has in store for me I really hope there is some kind of turn around. Once this mild weather clears off I can see colder conditions returning, hopefully.... This is my 10 day forecast, not the most appealing to anyone I would say (Unless your a duck):

[BLAST FROM THE PAST]

As its very nice and quiet, this episode IMO is a non starter for prolonged cold, we'll see some pressure build as per models over France with trough extension from west elongating over UK, but the general theme will see a gradual tilt/development for trough over Scandi to form on or around Xmas as presuure build develops/transfers to NW. Cool to blustery cold NW'ly flow and a biting northerly as we approach NYE. I think the model's are getting it right.....no resurgence of easterly set up. An up and down month which will be below average but not greatly so. There is a chance of the blocked theme really getting put on back burner here.

Battle of Britain to rage in January - and from say week two [anything from 7th onwards] cold to increasingly win as the jetstream shifts south and severe cold in place to our NE advances with GHP extension SE towardsUK/Irealnd/ North Sea developing. Pressure to S and SE lowers, trough over Scandi. Prolonged and deep cold to takie hold as we deepen into January as the trough in Scandi becomes extension of HP from Greenland and a pronounced NE [generally] feed takes hold. The active pattern early Jan will be there but with deep cold knocking on doorstep it could get messy and much colder and snowier earlier than anticipated in LRF. 8-10 Jan......dates GP mentions, dates to watc another to watch 16-22 could be a large winter storm and a memorable part of winter. Are we seeing very early signs from GFS FI of what the hemispheric pattern is trying to achieve but not quite getting there yet?

I had a poor start to my LRF but looking like a reasonablet call for Xmas period which is increasing confidence of events ahead as the pattern evolving is anticipated. January I will add looks a a ding dong month.

BFTP

Edited December 21, 2012 by BLAST FROM THE PAST

[johnholmes]

If this is what winter has in store for me I really hope there is some kind of turn around. Once this mild weather clears off I can see colder conditions returning, hopefully.... This is my 10 day forecast, not the most appealing to anyone I would say (Unless your a duck):

not very helpful to the rest of us Sean as we need your nearest town in your avatar please? - thanks

[BLAST FROM THE PAST]

Much quieter in here. Merry Christmas all, I go to a non internet zone tomorrow until the 27th. Have a great one and see you in 5-6 days when hopefully we'll be seeing signs of winter ARMAGGEDDON. But on serious note I hope the flood alerts do not come to fruition.

regards

BFTP

[Weather-history]

I agree its far too early to judge but I can't help feeling a little bit cynical here that since the easterly threat disappeared, GP, hasn't given his thoughts on the latest outputs. It gives the impression that things aren't going according to plan.

It would be interesting to hear Glacier Point's latest thoughts as it looks as though the December part of the forecast seems to have gone a bit awry.

Edited December 24, 2012 by Weather-history

[Bristawl Si]

Seems like Roger's is the one LRF on track, at this stage. He indicated a small cold blip after New Year i think, but not prolonged, so even if that doesn't happen it would only be a micro part of his 3-month forecast.

His main call was for a cold spell towards end January/early February with not much else before that in way of cold/snow. That's a long way off yet but at mo he seems pretty much on track.

[UV-RAY]

Seems like Roger's is the one LRF on track, at this stage. He indicated a small cold blip after New Year i think, but not prolonged, so even if that doesn't happen it would only be a micro part of his 3-month forecast.

His main call was for a cold spell towards end January/early February with not much else before that in way of cold/snow. That's a long way off yet but at mo he seems pretty much on track.

Indeed Bb, all other winter forecasts should be consigned to the bin IMO due to them being totally incorrect.

[Weather-history]

Indeed Bb, all other winter forecasts should be consigned to the bin IMO due to them being totally incorrect.

Hey up, here's my December forecast.

"I think December will be fairly wet and unsettled but not specially mild, a bit like December 1993. The further north, you are the more wintry potential, there will be."

[UV-RAY]

Hey up, here's my December forecast.

"I think December will be fairly wet and unsettled but not specially mild, a bit like December 1993. The further north, you are the more wintry potential, there will be."

Ha ha, apologies dear sir your forecast is indeed still valid.

[Ice BIast]

GP's Dec forecast looks OK to me, his forecast for 500HPa heights fits the actual anomaly for December so far...

http://www.esrl.noaa.gov/psd/tmp/composites/compday.90.201.160.178.358.2.18.32.gif

[UV-RAY]

GP's Dec forecast looks OK to me, his forecast for 500HPa heights fits the actual anomaly for December so far...

http://www.esrl.noaa.gov/psd/tmp/composites/compday.90.201.160.178.358.2.18.32.gif

His forecasts for the UK is bust and that essentially what his winter forecast is, for the UK.

[Ian Brown]

His forecasts for the UK is bust and that essentially what his winter forecast is, for the UK.

I don't think it's been a bad forecast in terms of overall pattern - he did point to a cold spell in mid-December, it's just been rather unlucky in the way things have played out for a small island like ourselves in the position we are in.

Soon crunch time for the forecast as a whole though, as he did go for a significant mid-Jan cold spell, low pressure over Europe and talk of a 'locked in' negative AO/NAO for the second half of the winter. We are going to be in the reverse of those situations by early Jan, so let's see what unfolds.

[Weather-history]

GP's Dec forecast looks OK to me, his forecast for 500HPa heights fits the actual anomaly for December so far...

http://www.esrl.noaa.gov/psd/tmp/composites/compday.90.201.160.178.358.2.18.32.gif

Doesn't that highlight the problem of trying to use macro techniques at the micro level?

[Barry12]

Barry's January & February Forecast

A similar theme of Atlantic dominated weather will continue into January, temperatures in the south will be between 8-11C, while in the north temperatures will be between 6-9C. Rainfall will widely be above average, causing more flooding in places, especially in the south west.

Into the middle of January, temperatures will be slightly below average as air comes from a more Northerly direction, in the south temperatures will range from 5-7C and 2-5C in the north. Rainfall will be around average if not below. There will be hill snow in the North, mostly rain at low levels in the North, but occasional wintery showers will fall, especially to the North-East of the UK.

As we approach the last week of January, temperatures will be well below average as the wind comes from a more North-Easterly direction. In the south, temperatures will range from 1-3C and 0-2C in the North. Rainfall will be below average during this period. Wintery showers and some snow will fall in the south, especially in the East. Some sleet but mainly snow will fall in the North, especially to higher ground and to the East. Western parts of the country will still see some rain but mainly wintery showers, a few cm's of snow will fall here though.

As we approach the 1st week of February, a similar theme will continue, temperatures in the south will range from 1-2C and struggle to get above freezing in the North. Rainfall will continue to be below average. Sleet/Snow will continue in the south, mainly snow in the North for most parts even down to lower levels, western coasts may be the exception getting rain/sleet.

As we approach the 2nd week of February, temperatures will recover to around average in the south, while still being slightly below in the North. Rainfall will also return to more normal levels. Snow will be restricted to NE Scotland and higher ground in the North.

From mid February onwards confidence is low, but temperatures will probably be slightly above average, as Atlantic dominated weather returns. Temperatures in the south will be around 9-11C and 7-10C in the North. Rainfall will be around average or slightly above.

In conclusion, a cold spell during the last week of January and 1st week of February will bring snow to most of the UK, heaviest in Eastern parts of the country. During the 2nd week of February the snow will thaw and temperatures will recover to average/above for the rest of Winter.