Jump to content
IGNORED

Winter LRFs


shuggee

Recommended Posts

Posted
  • Location: Upper Tweeddale, Scottish Borders 240m ASL
  • Location: Upper Tweeddale, Scottish Borders 240m ASL

As requested, and like last year - this thread will contain pasted copies of all Winter LRFs.

To have yours included, please PM a member of the nw team. If you want to comment on the forecast, please find the original relevant thread below.

To kick off - here's Roger J Smith's Forecast :whistling:

Long-range winter forecast

by Roger Smith

Following is a somewhat more detailed version of the long-range forecast which I have already mentioned in summary form in the past few weeks here on NW.

Overall, I expect the UK and Ireland winter pattern to begin milder than average through late November and December, then turn colder than average in January and at least the first half of February. This colder regime, when it arrives, may turn out to be some of the coldest weather seen in the British Isles since 1987.

As you may know, I base the forecasts in part on research on the solar system magnetic fields that the earth ploughs through on its orbit around the Sun. I'll leave the more complex explanations in the "advanced area" of the learning forum, but the general idea is this -- the Sun would be emitting a more or less uniform flow of heat and charged particles if it happened to exist without a planetary system, but since there are a variety of planets present (and mostly accounted for), there are subtle variations in the sector values of this outflux. Although I believe these variations are in the order of 1%, they appear to be significant enough to have effects on the environment near the top of our atmoshere, where the earth's magnetic field is generated by interactions with the larger solar system magnetic field. These variations are translated down to the surface layers in what the research shows to be somewhat predictable ways, and therefore some general trends in the long-range forecast can be inferred.

At the same time, I don't discount the importance of the other types of index values that other workers use to formulate their LRFs, and I try to stay on top of those trends to shape the forecast -- for example, if my research shows a higher than average index for high-latitude blocking, as it does this winter, then (as last winter demonstrated somewhat in hindsight) it makes quite a difference what's going on in other parts of the nearby climate environment. Last winter, the persistence of a ridge just to the west of Ireland kept interacting with the persistent strong high over the Baltic regions, and the result was a rather unsatisfying mega-ridge which certainly delivered on cold from time to time, but not very much on snowfall as there were simply not very many opportunities for frontal contrast, strong sea effect, or even half-decent troughs, unless you lived in Wales, that is.

So having said all that (probably for no good reason), here are some of the factors that I identified as relevant to the long-range forecast scenario:

-- higher than normal index values from research for strong zonal flow NOV-DEC, and blocking high pressure JAN-FEB, with the secondary feature that spoiled last year's party (the 10W ridge) not indicated as a factor this season.

-- many indications that a weak El Nino pattern will be fighting for dominance against a strong arctic vortex over eastern North America, not the 1997-98 or 1982-83 type coast-to-coast mild regime but something perhaps more like 1976-77 or 1977-78, in other words, a very active jet from central North America extending presumably well into the Atlantic if not right across Europe. This factor should be dominant especially in the first half of the winter and allow the long-lived above normal temperature regime to maintain itself through later November, once this temporary cold spell fades out, and probably through December into the first few days of January.

-- another aspect of the research, lunar interactions with the magnetic field, indicates a good index value for strong high pressure development and deep low pressure generation, in other words, a more volatile pressure oscillation associated with a strong storm track.

-- warm SST anomalies are likely to persist, so that if a large-scale cold outbreak does develop, snowfalls could be quite potent, but marginal events would likely be damped out by the warming of surface layers. In other words, for snowfall it is admittedly a rather dicey situation, all or nothing if the winds do turn easterly for a prolonged time as I think they will.

----------

Having reviewed those factors, here are the general indications for each month, assuming that November will be fairly bland until mid-month, then more active and quite mild later in the month with a strong SW flow developing.

DECEMBER may be quite mild relative to normal values. A CET of 5.5 or 6.0 is indicated with the flow being WSW and a steady progression of Atlantic systems occasionally interrupted by one or two day northerly type incursions. The Christmas-New Year period looks likely to remain mild, cloudy and at least a little wet and foggy. Strong windstorms may develop around the 4th-5th and 19th-20th, as well as other occasions on about a 4 to 5 day cycle.

JANUARY looks promising for some real winter weather, if that's what you like (and I know you do). This winter, a strong Siberian high should retrogress earlier into Russia than it did last winter, and may form quite a massive block over Scandinavia as early as around New Years. When this reaches a point where it starts to interact with the still-strong zonal flow and jet stream at about 53-55 N, the pattern should become quite stormy, starting with the "full moon northern max" event on 3-4 January, which should play out as a turn to more NW flow and a sea effect snow streamer situation favouring Wales, western Scotland and parts of western England. Some time later, perhaps a week or so, the flow should turn more easterly and involve some of the really cold air from central Sweden in the British Isles weather pattern. At this time, if it's possible to have major snowfalls in this day and age, perhaps this will be the awaited scenario with good peaks of energy indicated around the 15th to 20th of the month. At any rate, I think this battleground will be the theme of the month, whether it delivers or does another 2006 and just teases, but I think the chances of actual real winter weather are higher this time. The CET could be anywhere from -1 to +3.5 in such a tight gradient as I foresee here, so let's say around 1.5 as an official guess, but with the potential of a subzero month.

FEBRUARY will then be a case of the retrograde high-latitude block slowly edging past the UK towards Iceland and Greenland, with occasional attacks of the still-fairly-strong jet stream that is by now depressed towards about 47-49 N. Seems like a good scenario for some additional snowfall events and depending on the persistence of snow cover, prolonged periods of cold. There is some indication of a mid to late month reversal to much warmer weather so with that in mind I am predicting a CET of about 3.5, but it could run colder for most of the month.

So, keep your fingers crossed, if you're hoping to see some old-fashioned winter in the new-fangled climate.

Link to comment
Share on other sites

  • Replies 11
  • Created
  • Last Reply
Posted
  • Location: Upper Tweeddale, Scottish Borders 240m ASL
  • Location: Upper Tweeddale, Scottish Borders 240m ASL

Evo's asked me to pop his forecast in here. If anyone else wants theirs pinned at the top for the season - get in touch with a Team Member ;)

Dec:

A fairly mixed bag of wet and windy zonal conditions with occasional outbreaks of cold from the North. These outbreaks will be more prolonged towards Christmas. The cold interludes will tend to have a Westerly component to them so coming from the NW to NNW and obviously favouring Western areas. The zonal conditions will keep things a little too mild for anything memerable. Christmas will be crisp and dry for most, with some Western areas from the Mersey Northwards possibly seeing some light snow showers. CET: Average to average + 1

Jan:

Initially a poor start for cold fans. Winds mainly zonal and generally mild and wet. Towards the end of the month HP will build around the UK and a potent cold blast will be shot into the continent. The UK will be largely unaffected by this initially. After a brief zonal spell of only a couple of days, this pattern will reload and repeat at the end of the month and into February. CET: Above Average (<3c above)

Feb:

Initially another cold plunge into the continent. HP dominated start with dry, bright and crisp days. Around the 10th to the 15th the atlantic will be quiet, the HP will retrogress and an Easterly pattern will set in. Winds will tend to have a Southerly component to them with areas in the South East most at risk of showers. Initially the pattern will bring little in terms of decent snowfall but the pattern will persist for quite some time. Eventually a front will push in from the atlantic and it's gradient will allow for quite a prolonged and heavy snow event. Quite where the battleground will be is uncertain but it will be probably east of a line from the Isle of Wight through Birmingham. CET: below average

Link to comment
Share on other sites

Posted
  • Location: Upper Tweeddale, Scottish Borders 240m ASL
  • Location: Upper Tweeddale, Scottish Borders 240m ASL

And here is Snowmaiden's Winter LRF:

To start, I C&P below the original late Sept forecast

In producing this I have split the observations into areas so as to theorise on local differences and the prevalent conditions and I intend to keep it simple rather then overcomplicate what is not exactly rocket science.

From Scotland we have reports of early migration of Geese and thicker onion skins (the thicker, the colder the winter to come), the same migration of geese is reported in the North of the country, however there are no avian reports from elsewhere.

The East sees an abundance of acorns this year, both indicative of a hard winter to follow, although the excess of berries reported in the West has not been repeated in the east which is actually (form personal observation) not very impressive on the berry front this year.

The south has also reported large store of acorns.

In terms of general lore, a warm 21 Sept is an indicator of a warm December to follow, I would class the 21st just passed as warm. Conversely a thundery Autumn is an indicator of a cold winter. The autumn so far would appear to be somewhat thundery, certainly we have had more rumblings here than I might expect at this stage. A 'cold' August is an indicator of a hard and dry winter to follow, however despite the amazing drop in temperature between July and August, August was not 'cold' it was cold relative to July (and therefore perhaps winter might be expected to be cold relative to recent winters rather than generically cold). September will be a very warm month, this is thought to herald a warmer winter.

Therefore, the indicators and initial forecast is as follows

Given the weight of cold indicators versus warm indicators, the winter period is likely to be below average for temperature, many of the reports coming from the north and western parts of the UK (particularly Scotland and Wales), therefore this could be seen as indicative of a northerly and northwesterly dominated winter, Greenland blocking coming into play and returning polar maritime air. The east 'cold' indicators would support the northerly aspect but the conflicting data perhaps suggesting the main action will be further north and west.

Mainline indicators are around even at this stage so the temperature is likely across the board to be only slightly below the average, with the colder weather north and west and the south and east experiencing colder 'snaps' from northerlies and milder interludes between.

Rainfall gives no clear message as yet, perhaps a hint of lower than average precipitation.

Temps - slightly below avergae

Rainfall - slightly below average

Places to be for snow - Scotland and the North West, North Wales

To add to this, I can confirm that roses were blooming in my garden util this week and flowers generally are staying late this year, this is 'a sure sign of a bad winter to come'. The nut harvest was very high this year and I have seen a lot of squirrel activity.

Onion skins are thicker than some years but not excessively so although my reports on this are sporadic and from various family members (many of whom catch whale sized fish whilst fishing), again another sign of something colder.

In terms of generic lore

A Thundery autumn is said to lead to a colder winter. The September and October period from memory was quite thundery, without perhaps being a thunder-fest.

'Ice in November to bear a duck, the rest of winter be slush and muck'

A frosty start but a generally cold November now looks unlikely, will be close to the GW-modified average, hence no indictaion of a wet and mild winter from here.

A warm October leads to a cold winter - this speaks for itself although I am going to mitigate this by saying the October warmth was more a nightime phenomena and hence not as strong an indicator than it might appear from raw CET input.

When the leaves turn, if they shrivel and hang on the trees then the winter will be snowy - some evidence of this seen locally and from (I believe) Tugmistress earlier in the Old Wive's thread.

Finally 'As September, so the following March'

Incorporating this into my initial thoughts I propose no major changes to what was said initially, I think the winter will end abruptly towards the end of February and March will be a very mild month this coming year. As cold indicators have come in for the South and East rather late on in the Autumn (onions, the onging nut harvest and the reblooming of my roses) I would go for any Easterly incursions being the domain of February. Very uncertain on that and I still favour a generally Northerly dominated winter - this would be mainly NW and N but does not preclude some NE'ly activity which would appear to be where the 'Eastern' indicators come from.

To summarise

I think temperatures wil fall below the long term average as cold indicators now outweigh mild indicators, this wil not be dramatically below, up to a degree below the 71-00 as a guide. The winter will be relatively snowy but slightly drier than average.

Snowfall will be most prevaent over Scotland, the NW and Wales with the Eastern Coasts, East Anglia and Kent seeing slightly higher than average snowcover/snowy incursions. Snow will occur in Central and SW areas but will be far more sporadic, although these areas may see an abundance of frosts.

Temps - slightly below avergae

Rainfall - slightly below average

Places to be for snow - Scotland and the North West, North Wales. Later in the winter, Scotland, The NE, East Anglia, Kent.

Coldest periods - December and Late Jan-Early Feb

Link to comment
Share on other sites

Posted
  • Location: Upper Tweeddale, Scottish Borders 240m ASL
  • Location: Upper Tweeddale, Scottish Borders 240m ASL

The controversial Rick Leming Forecast:

Hello everyone, I am Richard and I have recently been browsing through this forum and thought that it was the most appropriate place to post an very important message that I am about to write.

I am a highly experienced forecaster who has a special and unique method of forecasting which I make using a variation of synoptic analyses, variables in meteorological equations, synoptic matching and global factors. I have an Msc in Applied Meteorology and Climatology and currently hold two occupations, one as an accountant, another as a worker of a very small, secret weather organisation in North London, which at the moment I am not obliged to name. It is a new company, which was opened this year and has enjoyed a very high level of accuracy. Due to this accuracy, this organisation will soon be employing more workers and will become openly available to the public next year with a new website and various data sources. My own recent personal forecasting accomplishments include successfully predicting the hottest calendar month on record this year, a September which was warmer than August, the hottest May-Oct period on record and the coldest November to March period for 10 years in southern England last winter.

In the last few winters I have been successful in predicting fairly mild temperatures, with a prediction for a more average winter last year, which was particularly accurate in terms of monthly forecasts.

Now I am sure most of you would be expecting a continuation of the exceptional warmth that we have seen in the last few months with a mild November and December. However, I have been revising the pressure patterns for each month of 2006 and during many occasions there has been extensive blocking, which has frequently occurred to the north of the UK. Along with numerous other factors, which I can't go into detail, I have come to the conclusion that I must warn you all that next month is going to be bitterly cold with a great deal of snow. December 2006 will be characterised by extensive and prolonged northern blocking, a high frequency of easterly and northerly airstreams over western Europe and a notably severe spell of wintry weather, which I predict will occur between Christmas and the New Year. I predict it will be the coldest month since at least January 1987. It is likely to be the coldest December since 1981, perhaps even 1890.

I am more certain about next month than I have ever been about any of the forecasts that I have issued before. The continuous warmth since late April will simply burn itself out into a very dramatic and extremely cold and wintry end to 2006.

The extensive northern blocking is already beginning to take shape; you will have noticed in the charts a distinctively large area of high pressure over northwestern Russia. This will become predominant for several weeks and will begin to influence our weather by about November 25th, when I expect the prolonged cold spell to set in for December. I would have posted this message sooner if I had found this site any quicker.

Temperatures will be cold or very cold in all areas throughout the month, with several nights falling below –10c in many inland destinations across England, Wales, Scotland and Ireland. Snow will also be widespread across the country, with many places seeing snow cover for much of the month, again with the worst of the wintry weather occurring towards the end of the month. I find it quite probable that many lakes and slow moving rivers will freeze up as I expect an extensive amount of ice days in most regions during the month.

Overall temperatures may be as much as 3 or 4c below average and any mild or even average temperatures will be very brief and minimal .To put it simplistically I expect a repeating pattern of high pressure to the north, moving south over the UK giving way to Arctic northerlies, then high pressure rebuilding to the north and the pattern continuing. I expect substantial blocking over Greenland and/or Scandinavia which temporarily relocates over the UK, maintaining the cold theme. Essentially this pressure pattern diverts the jet stream 500-100 miles north of its usual track, or 500-1000 miles south, also blocking Atlantic lows from entering the UK or diverts their tracking to the south of us, which of course creates major potential for snowfall.

The chances of a White Christmas look promising as a result of this forecast, however due to the definition from the Met Office, it does have to snow on Christmas Day itself for it to be an official White Christmas – we'll have to see if that happens or not!

Be prepared for next month, make sure you buy a sledge if you don't have one, also make sure you have some gloves with you as it really is going to be a freezing December.

I am contacting the Meteorological Office and other weather organisations who I will be working for from the start of next Spring. Please spread the message to everyone else. I am extremely worried about next month as I fear that transport could be seriously affected by the severe weather, especially after many years of generally mild winters and it is vital that an early warning is given.

A brief precursor to January and February is that I do not expect a winter on the level of 1962-1963 and I do not expect January and February to be as cold as next month. However, it is difficult at this range to predict further than six weeks.

It is not in the best interests of anyone to be given a weather forecast which is not made without at least a reasonable level of confidence, therefore I must stress that I have very high confidence in this prediction and can assure you that I have made every effort possible to make sure this forecast is not in any way misleading.

Don't expect the models to be reliable in the next few weeks, as this is an extremely difficult situation for any of the forecasting models to predict. However, I am hopeful that this post has got your attention and has shed some light on what to expect next month.

post-1217-1164834336.gif

Link to comment
Share on other sites

Posted
  • Location: Upper Tweeddale, Scottish Borders 240m ASL
  • Location: Upper Tweeddale, Scottish Borders 240m ASL

And here's Chilly Milly's Forecast :)

Believe it or not I've worked really hard to come up with a forecast, and so far I've only done December. I've read lots of posts and peoples different perspectives on the way things will go, and my forecast has really been as a result of reading everyone elses take on things.

I'd expect December to start cold, wintery and snowy. The winds will be from the North, and people will become very excited about the prospects ahead. I believe the first two weeks of December will bring a lot of hope and expectation and the CET will start below average. However, the second two weeks will see the winds shift to a more s/w flow as a Bartlett or some other such weapon comes to destroy the cold. The days will be warmer than average and it will be dry and sunny. Therefore Christmas will be dry and mild.

I expect the CET to end up above average around 6C or7C due to the extremely mild second half of the month.

I'll have a go at January tomorrow as I'm worn out coming to that conclusion.

(Chilly Milly @ 16 Nov 2006, 12:59 PM) post_snapback.gif

For want of anything better to do, I've had a go at January. Following on from December I expect the winds to move from a SW direction to a NW direction, bringing sleet and snow to NW England, Wales, Scotland and Ireland. I don't think the weather will be as bad as early December but snow will be sporadic. I'm undecided on the second half of January, possibly continuing with a NW feed and bringing in further snow showers or reverting back to SW and turning wet and warmer. CET to be around average 5C.

For February

I think this will be the first month that we have a chance of an Easterly. However, I don't think it will deliver much. If we get an easterly it will be in the early part of February, and its possible it won't arrive at all leaving us with a southerly feed and lots of disappointment.

Second half of February will return to North Westerlies/Westerlies. With snow for North West England, Scotland and Wales, filtering through the pennines to tantalise those in the Midlands but not quite making it.

CET to be above average at 5C due to warmer temps down south.

Stratos Ferric's winter prediction:

I don't normally indulge, for the obvious reasons that if the experts and professionals can't manage to nail more than 5 days out, who am I to suppose that I can nail 90; however, I offer some general thoughts.

There's no doubt that the weather recently has been, if not so much less dominated by the Atlantic, certainly dominated by it in a different way to the norm. The traditional autumn has a more stable jet with a more sustained feed of surface LP; at present we are in a phase where the storm track is slightly further north on average, allowing more HP influence at the surface in the environs of the UK.

In addition SSTs remain well up, the NH generally is well up, and looking at the latest SSTs the Atlantic is generally well up and to cap it all there's what looks like a big El Nino kicking in. One "however" is that the NE Pacific is starting to look very cold; this could push the jet here further south, and with a very warm tropic accelerate the jet, forcing a big northward arc across the US (not dissimilar to the latest GFS prog for later next week), and potentially a downstream wave in the Atlantic, bringing surface systems slightly further south at times.

Finally, a general pattern in recent winters: cold around late December is something of a feature, particularly given the general scarcity of cold in recent years; also, cold in mid-Feb through mid-March is also a feature. I have given a hypothesis for this elsewhere, and there is no reason to vary from that pattern this year.

On the face of it therefore we have the following:

- potential for more HP influence than typical in the early part of winter, depending on location this may provide anything from very mild, to calm and cool, to cold polar feed;

- some potential for occasional movement S of the PFJ, giving cool zonality;

- potential for modification of cool / cold air from the W/NW; and

- likely settled, cooler weather later in the winter.

Assigning this to the calendar is essentially fairly random; however, for those of you who haven't yet lost the will to live, or given up because this outlook hasn't yet mentioned snow, here goes:

December - changeable; mix of cool zonal, perhaps a polar burst, but more settled as we approach Christmas. Slightly drier than normal, temps around average.

January - potential for a '78 like month; cool zonality with one or two days of threatening cold, best in the N ( a bit like the last day or so); doubtless much squawking on N-W about "near-misses" and "the cold weather trying" etc. Probably one extended spell of HP dominated mild. Overall, about average rainfall, and a smidge warmer than normal.

Feb - hard not to go with the recent pattern; warm start, dominated by Azores HP, giving way to a cooler finish; perhaps another "wandering high", as we had last year. Overall temps average to slightly above.

March - changeable, certainly no repeat of 2006.

Link to comment
Share on other sites

Posted
  • Location: Upper Tweeddale, Scottish Borders 240m ASL
  • Location: Upper Tweeddale, Scottish Borders 240m ASL

JoeShmoe's Forecast:

Sorry but I dont see how anyone can think El Nino wont have an effect on our winter. Its the dominant teleconnection signal in the NH bar NONE and will affect all other signals and centres of influence upstream. Even a weak signal overrides the other teleconnectors IMO

Its no coincidence IMHO that this Nov/Dec is looking like being potentially the wettest and stormiest since 1997

I expect Dec to be wet and mild with possibly one or even 2 short lived northerly spells as the warm aid feeds the Scandi ridge enough to split it west and form the mid atlantic block. The pattern would then reload with Icelandic LP taking over again

Jan, more of the same if we avoid the Bartlett / Euro High scenario which I think we will because of the energy pumped into the ST jet

Feb, quieter for a time as HP builds and maybe colder end of the month and into March but nothing major

Link to comment
Share on other sites

Posted
  • Location: Upper Tweeddale, Scottish Borders 240m ASL
  • Location: Upper Tweeddale, Scottish Borders 240m ASL

Here's Conor123's effort:

My forecast:

December: A mild, zonal start with a bartlett situation keeping temps

between 8-14c across the UK. This will be followed by a brief cold

spell giving snow in the north but as it starts to affect all parts

milder air sweeps in from the west. This will last till the middle

of the month, then high pressure will built sweeping in colder

air for all parts with severe frost in places. As christmas draws in

a warm front shifts the high out the way for the 21st, this will

be followed by a spell of very mild and wet weather until christmas

eve. Then on christmas day a northerly arrives similar to xmas 04

giving snow for many, this gradually turns to an easterly giving ice

days for some with highs of -2c in the midlands 28-30th. The year

will end with a breakdown giving blizzards for all.

January: A rather cool and blustery first few days, 5-9c with

lots of showers (some wintry) this will then be followed by

gloom as a high moves in off the atlantic, this continues

until mid month then a brief but potent NW cold blast dragging

very cold air from greenland giving snow for many as well.

The 18-26th will then see persistant mild or very mild air

over us giving loads of rain and flooding. The 27-31st will

then see cooler air from the west/north west giving snow

over hills.

February: A rather settled start with high pressure but rather cold,

this will be followed by a south easterly giving snow especially

in England & Wales. However another high will move in from the east,

by the middle of the month as mild air arrives expect a snowy breakdown. Then 17-20th will be very mild with lots of rain. The 21st-

28th will then see the usual cold spell with snow for all, some frontal,

some as snow showers temps -1c - 3c.

Link to comment
Share on other sites

Posted
  • Location: Upper Tweeddale, Scottish Borders 240m ASL
  • Location: Upper Tweeddale, Scottish Borders 240m ASL

Kold Weather's:

My forecast would go something like this:

Dec--- 4.5C, the temps hover above average for much of the month until the last week when we get a much colder spell that pushes the CEt below average. This continues into Jan. Quite above average rainfall.

Jan---1.1C, Very cold first half of the month with the CEt averaging just around around -1C. Not quite sure exactly what the source would be but very cold air indeed. Third week stays cool but air moderates somewhat, nighttime mins though keep CET low. Final week warms up even more with first signs of a real warm-up with some quite above average temps indeed. Rainfall well below average.

Feb---6.1C, Starts out slightly above average but the jet really kicks into action this month with a strong Bartlett by the second week giving some very above average temps. Bartelt tis replaced by Euro high which keeps the mild theme going but not quite as mild and the last week sees an average set-up wth some cold zonality in the north possibly. rainfall probably below average in Se, above in NW.

That would be my punt right now, outside the coldest period could be pretty mild overall but I think the 2-3 week very cold period will make this winter one of the better ones in the last 20 years, even if outside of it will be very fustrating for cold lovers dominiated by weak northerly topplers then euro/Bartletts filling into Europe in the wake. Still I think that if tyhe 3 weeks do pull off then it wil lbe a memorable winter indeed.

And Tamara G's LRF:
OK - sorted out my uncertanties and this is a stab at what I think may happen.

Irrespective of whether El Nino does strengthen I don't think it will have any effect on at least the first 70% of the winter and spoil some good winter excitement.

I agree with others that this winter brings a real chance for us to go a step further than last winter and have a real polar continental blast at a much more favourable time. I think that the underlying -NAO trend prevalent through the autumn will nicely 'default' our winter, with much more favourable conditions than last year for Greenland High pressure to back cold pooling to our east westwards over us and a southerly tracking jet feauturing during January. All these will finally deilver some cheer in the main part of the winter - followed by a milder end to the winter this time - in contrast to the last couple of years.

I would not be surprised to see a taster of things to come by second half of December with north or north easterly winds bringing the first proper cold spell of the winter to us, albeit brief. I think at first favoured northern and eastern parts will see snow showers and accumulations esp over higher ground with most other areas clear, sunny and cold by day and very frosty at night but then as high pressure slips in from the north west and the wind takes on a more easterly component in southern parts these snow showers will affect more south eastern parts of England for a time before high pressure takes over everywhere. A frosty high may therefore be in evidence in time for xmas for a couple of days or so straddling the festive period followed by a breakdown from the west at the end of the month with snow possible for western parts, including Ireland and spreading east before milder atlantic air comes in.

The start of January may well continue this milder interlude as the atlantic edges in against a cold block to the east (which will remain close by throughout). By mid-Jan the main cold spell of the winter comes in from the north east as the jet dives south and high pressure really asserts itself over Russia/Scandinavia westwards to Iceland/Greenland with some real cold everywhere and decent snowfall for many. This may well give a decent lasting spell through the main spine of January :nonono: .

A southerly tracking jet may bring the threat of some very heavy snowfall in this period to some southern and western parts, including Ireland. This threat may extend slowly northwards with time and blizzard conditions in the north and Scotland whilst milder air reaches southern and western parts by months end.

Thereafter into February it is possible that in contrast to the last couple of years we may see the opposite trend occur with it being dominated by low pressure from the atlantic with higher temps. However, in terms of what preceeded it, this much more forgettable part of the winter may well be made more tolerable.

:lol:

Tamara

Link to comment
Share on other sites

Posted
  • Location: Upper Tweeddale, Scottish Borders 240m ASL
  • Location: Upper Tweeddale, Scottish Borders 240m ASL

Snow-man2006's little ditty:

Below is an updated (17/NOV) brief Winter Preview. My real forecast is avaliable on 31st of NOVEMBER so stay tuned...

Week 1 December:

Cool weather looking likely to persist from November. Settled at times but bands of rain not to uncommon. However i do expect some highland snow and possibly down to lower levels at times.

Week 2 December:

Fairly Settled. Jet heading north but with th eGreenland high already starting to form a block it looks cold with sunny spells.

Week 3 December:

We see the jet diving south then north bring a spell of particularly mild spell of weather with presistantrain at times.

Week 4 December:

Low pressure that i have seen to be devloping over Scandinavia may head south introducing Northerly Winds for a time as the jet gets stuck with this block once again, from greenland.

January

Just as we see some snow from the last week i do how ever expect this cold spell to end quite readily as we see the jet heading north allowing low pressure ot influence our weather in the first halve of the month. During the second halve however i expect the low to merge with the scandi low allowing NW winds to devlop for a time.

February

Very Difficult to predict at this stage as the Sun will begin to warm again as the Earths tilt increases so I reckon (at this point) that with a Negative-Neutral NAO in place and A deep area of low pressure of Scandinavia and a southerly Tracking Jet that February will turn out to be very snowy indeed as we see NE winds break out.

March

Negative NAO but unfortunately at this time of year temperatures will be on the up so I predict a fairly wet march with some snow to begin.

SM06

And Summer Blizzard:

Today, i am going to post my teleconnections winter forecast, my anologue based forecast will be released on the 20th all being well in this thread.

Firstly, i would just like to show my success rate to you all based on effectively using 2006 as an anologue.

Janauary: Predicted 4.7C: Actual 4.3C: Difference 0.3C: Successful forecast

February: Predicted 3.7C: Actaual 3.7C: Difference 0C: Successful forecast

March: Predicted 5.3C: Actaul 4.9C: Difference 0.4C: Successful forecast

April: Predicted 10.6C: Actual 8.6C: Difference 2C

May: Predicted 11.8C: Actual 12.3C: Difference 0.5C: Successful forecast

June: Predicted 12.6C: Actual 15.9C: Difference 3.3C

July: Predicted 20C: Actual 19.7C: Difference 0.3C: Successful forecast

August: Predicted 15.2C: Actual 16.1C: Difference 0.9C

September: Predicted 15.2C: Actual 16.8C: Difference 1.6C

October: Predicted 10.4C: Actual 13C: Difference 2.6C

November: Predicted 3.9C

December: Predicted 5.6C

50% success rate so far this year.

http://www.metoffice.com/research/hadleyce.../HadCET_act.txt

Here is my teleconnections forecast...

December

Here is the raw data for December...

December week 1 - NEGATIVE NAO - POSITIVE AO - NEGATIVE PNA

December week 2 - POSITIVE NAO - POSITIVE AO - POSITIVE PNA

December week 3 - NEGATIVE NAO - POSITIVE AO - POSITIVE PNA

December week 4 - NEGATIVE NAO - POSITIVE AO - POSITIVE PNA

December Week 1 - The Jet stream will come out of the United States of America on a notherly track due to a negative PNA however due to a positive AO, there will be a downstream trough over Greenland however due to a European Trough, the NAO will be negative and the Azores High will not ridge into Europe, resulting in the mean wind direction being north westerly.

December Week 2 - The Jet Stream will come out of the United States on a southerly track due to a positive PNA however due to a positive AO the Jet Stream will rise northward forcing the Azores High will ridge into Europe forcing a positive NAO and resulting in the mean wind direction being southerly.

December Week 3 - The Jet Stream will come out of the United States Of America on a southerly track due to a positive PNA, however due to a strong Azores High, the Jet Stream will rise northward in association with a positive AO however a ridge to the east of Greenland will force the Jet Stream to stay around the lattitude of the British Isles in association with a negative NAO, the mean wind direction will be westerly.

December Week 4 - The Jet Stream will come out of the United States Of America on a southerly track due to a positive PNA, however due to a strong Azores High, the Jet Stream will rise northward in association with a positive AO however a ridge to the east of Greenland will force the Jet Stream to stay around the lattitude of the British Isles in association with a negative NAO, the mean wind direction will be westerly.

CET - 5.6C - 0.5C above average - Warmest since 2002

Rainfall - 75%

Sunshine - 125%

January

January week 1 - NEGATIVE NAO - NEGATIVE AO - NEGATIVE PNA

January week 2 - POSITIVE NAO - NEGATIVE AO - POSITIVE PNA

January week 3 - NEGATIVE NAO - NEGATIVE AO - NEGATIVE PNA

January week 4 - NEGATIVE NAO - NEGATIVE AO - NEGATIVE PNA

January Week 1 - The Jet Stream will come out of the United States Of America on a northerly track due to a negative PNA however due to a negative AO, the Jet Stream will be forced over the top of the Greenland High and into Scandinavia resulting in a sustained northerly and a negative NAO with the mean wind direction being northerly.

January Week 2 - The Jet Stream will come out of the United States Of America on a southerly track due to a positive PNA and stay on a southerly track due to a negative PNA due to a negative AO, however due to a displaced Azores High over Europe, the Jet Stream will rise northwards resulting in a positive NAO and the mean wind direction being south westerly.

January Week 3 - The Jet Stream will come out of the United States Of America on a northerly track due to a negative PNA however due to a negative AO, the Jet Stream will be forced over the top of the Greenland High and into Scandinavia resulting in a sustained northerly and a negative NAO with the mean wind direction being northerly.

January Week 4 - The Jet Stream will come out of the United States Of America on a northerly track due to a negative PNA however due to a negative AO, the Jet Stream will be forced over the top of the Greenland High and into Scandinavia resulting in a sustained northerly and a negative NAO with the mean wind direction being northerly.

CET - 1.7C - 2.5C below average - Coldest Since 1987

Rainfall - 50%

Sunshine - 150%

February

February week 1 - NEGATIVE NAO - POSITIVE AO - NEGATIVE PNA

February week 2 - POSITIVE NAO - POSITIVE AO - NEGATIVE PNA

February week 3 - NEGATIVE NAO - NEGATIVE AO - NEGATIVE PNA

February week 4 - NEGATIVE NAO - NEGATIVE AO - NEGATIVE PNA

February Week 1 - The Jet stream will come out of the United States of America on a notherly track due to a negative PNA however due to a positive AO, there will be a downstream trough over Greenland however due to a European Trough, the NAO will be negative and the Azores High will not ridge into Europe, resulting in the mean wind direction being north westerly.

February Week 2 - The Jet Stream will come out of the United States Of America on a northerly track due to a negative PNA with a downstream trough over Greenland due to a positive AO and as result, the Azores High will be displaced over Europe, the Jet Stream will rise northwards resulting in a positive NAO and the mean wind direction will be southerly.

February Week 3 - The Jet Stream will come out of the United States Of America on a northerly track due to a negative PNA however due to a negative AO, the Jet Stream will be forced over the top of the Greenland High and into Scandinavia resulting in a sustained northerly and a negative NAO with the mean wind direction being northerly.

February Week 4 - The Jet Stream will come out of the United States Of America on a northerly track due to a negative PNA however due to a negative AO, the Jet Stream will be forced over the top of the Greenland High and into Scandinavia resulting in a sustained northerly and a negative NAO with the mean wind direction being northerly.

CET - 2.7C - 1.5C below average - Coldest Since 1996

Rainfall - 50%

Sunshine - 175%

Here are some December to February statistics...

CET - 3.3C - 1.2C below average - Coldest Since 1996

Rainfall - 100%

Sunshine - 150%

Please allow a 0.5C margin of error for all CET predictions.

Link to comment
Share on other sites

Posted
  • Location: Upper Tweeddale, Scottish Borders 240m ASL
  • Location: Upper Tweeddale, Scottish Borders 240m ASL

Here's the much awaited West is Best winter forecast :D

"My attempt ...

The past 18 months have been dominated by a -ve NAO and frequent euro blocking. SST signals and increasing El Nino suggest to me a much stronger jet pattern than the one we have been used to of late and I am reasonably confident that we are moving into a +ve NAO phase which will last virtually the whole winter (confidence on that 80%).

For the most part winter will be dominated by zonality with occasional north-westerly incursions and some limited blocking. There will be no easterly. The jet pattern will track north of the UK, and a Bartlett high will dominate mid December onwards for 4 to 6 weeks. However, occasional fronts will track more southerly than this, and these will give snow to northern areas and Scotland for a time. There will be occasional storms, some of them very severe especially for the far north.

Overall the winter will be between 0.5C and 1.5C above average, possibly more. One of the three months will break the record for the respective month (confidence on this claim very low!). Rainfall will be above average. Contrary to what most forecasters have suggested, the winter will buck the recent trend and mid-February will see the start of occasional warm days and the rapid end of winter.

So in summary: a mostly mild, wet and at times stormy winter in store."

Link to comment
Share on other sites

Posted
  • Location: Upper Tweeddale, Scottish Borders 240m ASL
  • Location: Upper Tweeddale, Scottish Borders 240m ASL

SNOW-MAN2006 winter forecast:

"December Forecast

My views may change by the time my monthly forecast is produced–

Well below are the SSTA’s below from the past few days are showing that our seas are very warm for the time of year. My forecast this year is proving very difficult as the charts are starting to show up a return to a positive NAO in the next few weeks. This will mean a warmer spell of weather but lets not wait any further discussing the problems and lets get on with the December Forecast-

First Week

As we enter the first week of December I expect that the Greenland high will be non-existent. However an increasing in size Siberian high is forcing our jet on a southerly track once it reaches the UK. So what does this mean? Well, if the conditions are correct then we can expect a northerly plunge from a low-pressure system that is squashed between the Bartlett high and the Siberian high. So I suspect NW winds can be expected during this week with temperatures below average. Snow may be constricted to high ground but it is still a possibility it could get down to lower levels in the north at times.

Second Week

This Bartlett high experienced in the First week to our SW may well be able to move north for a time as we see the Greenland high come back into place. I suspect this will make a Neutral NAO? So this will form a block preventing any low pressure from entering our area. This will then allow my nicely placed Siberian high to move into Scandinavia and produce possible easterly/South-Easterly winds. This will not be felt as a threat until the third week I feel as easterly winds take a while to cool things down so I suspect some cool conditions in the east at times with persistent fog likely as these seas begin to cool with drizzle likely. But the west can expect some glorious sunshine at times

And even here it will be cooler but it will feel pleasant with light winds the other side of the Pennines.

Third Week

Well, with my easterly winds now in full momentum I expect snow to begin its trek towards the UK. The first snow possible down to lower elevations, even sea level, as temperatures drop very low. Ice day’s possible inland as we approach Christmas. Now I am not talking loads of snow but a fair few inches (upto 10inches on higher elevations) could be likely especially as a smaller low pressure systems moves north from France. Even Western Areas can expect snow but not much and quite isolated. As the week progresses I feel very little change may be in-order.

Fourth and Xmas Week

Depending on whether the block can manage to hold on I think this week may be decisive over the entire rest of winter. If the block breaks then the west is likely to see some frontal snow before we see milder weather for Xmas. If the block holds then settled weather is likely to persist with some isolated snow showers. In my opinion I suspect the block may break allowing a much milder interlude of weather to develop. Wet and windy weather will make inbounds for the UK as we see a positive NAO develop. The Greenland high will shrink and I suspect it will be a while before any colder weather develops once more.

January

I feel that this month our jet will keep on heading straight for the UK. This will bring low pressure across the country for the start of the month and with the Scandinavian high moving away I suspect low pressure will make its way into Scandinavia. This is a situation many westerners may love because as the low pulls away it is revolving anti-clockwise meaning Winds will plough down the north or northwest so I suspect some snow could be very likely by the second week after a wet and milder first week. Into the third week and I think it is likely that the Greenland high comes into play again but this time it sends low pressure southeast allowing our little low pressure over Scandinavia to move back over the uk and even better it may head south east to as the Siberian high makes its presence felt once more. This means a possible NE out break may happen bringing severe cold to the east with plenty of snow. Into the fourth week I suspect that high pressure will be forced up from the south introducing a settled spell of weather but still not particularly warm but atleast it will be settled.

Temperature- Below average 2.3

Precipitation- Above average 120%

Sunshine- Average 100%

February

Well I do suspect February too much warmer In comparison to January. High pressure will be anchored in place over the UK introducing SE winds. These winds will originate from Spain so not particularly cold but clear spells over night allowing frosts to form. As we head through the month high pressure slowly will slip away to our South and the Atlantic will return with vengeance with the middle of the month proving very unsettled by well above average temperatures that possibly will reach mid-teens for the first time since November. However by the last week I think winter will have one last gasp and bring low pressure to our east once more allowing northerly winds to prevail bring snow and ice. A few ice days maybe with plenty of snow along coastal regions.

Temperature- 4.0

Precipitation- Average 100%

Sunshine- Average 100%

March

Negative NAO - I think a cold and possibly snowy start but soon giving way to much stormier weather as spring approaches.

Temprature-6.0

Precipitation- Well above average 200%

Sunshine- well below average 20%

Meaning a late start to spring is in order.

So overall I suspect this winter to be very cold, I have moved away from my earlier views of a colder second halve to winter. I have considered many peoples views but I suspect January to be the coldest month unlike many other peoples views that February will. My C.E.T prediction for December is withheld due to my forecast being released for December in a week (27th) so please be patient for that. So I hope we all have a cold winter so that may have fuelled my ambition for a colder than average winter :D . So a continued thanks to other members for their forecasts and I look forwards to seeing your views on my forecast.

Many Thanks and best Wishes

SNOW-MAN2006"

And Thundery Wintry Showers LRF:
December- Mild and wet, but with some brief cold snaps from northerly winds. CET 5.8

January- Average temperatures and dry, with frequent high pressure over Scandinavia, but too far east to deliver anything of consequence. CET 4.1

February- Dry start, a cold easterly spell in the middle with some snowfalls for the east, milder end with south-westerlies. CET 3.2

The winter quarter overall: slightly milder than last winter over the south, slightly colder in Scotland. It's highly likely to be wetter, and probably snowier, than last winter.

Link to comment
Share on other sites

  • 2 weeks later...
Posted
  • Location: Upper Tweeddale, Scottish Borders 240m ASL
  • Location: Upper Tweeddale, Scottish Borders 240m ASL

Glacier Point's mega-forecast ;)

Winter Forecast 2006/7

You might want to take some time out here to read this...

Forecast Summary

It's been twenty long years since we last experienced a prolonged wintry outbreak during January, the month when we in the UK are most likely to see snow. Whether this is related to global warming, warmer seas or multi-decadal cycles is open to debate. We can debate snow events in December, February and March but for much of lowland Britain, winter is January. Crack January, and the forecast will more than likely be accurate.

The Winter of 2005/6 proved to some degree that a consistent upward warming trend was no barrier to experiencing a colder than average season although January once again ended up the warm side of average care of a strong residual jet stream. Like last year, many of the key ingredients are already in place to deliver sustained periods of cold, and, in contrast to many Winters of the 1990s and early 2000s, these factors stand a reasonable chance of bringing about cold when it matters most, during January.

There are however some very mixed signals in the Pacific and across the North Pole which will characterise a highly variable pattern which switches rapidly from mild to cold with the potential for widespread snow as a result. Overall the Winter will be influenced most by three main features:

the Arctic Oscillation (AO);

North Atlantic Oscillation (NAO);

El Nino,

whilst the Madden Julian Oscillation (a tropical wave influencing weather patterns around the globe) will have a significant impact in terms of influencing rapidly swinging weather patterns, particularly during late December and February.

A weak to moderate El Nino is likely to feed mild SW'ly winds into western Europe. However, this Winter will see a largely negative North Atlantic Oscillation which will push the Atlantic winds further south bringing the UK under more easterly influence at times tipping the balance marginally in favour of cold, especially so during late December and January.

Due to the proximity of warm air off the Atlantic and weak ridging from warm seas around the Canaries, I am not forecasting a 1963 type winter. Temperatures will end up marginally below average - typically in the range 0.5C below CET for southern Britain and closer to average for Northern Britain but this will mask considerable monthly variations with December and January favoured as the below average months and February as the above average month.

There is a small risk of much colder temperatures developing if climatic variables shift in the next few weeks and cold weather takes root at the turn of the year. I would not hesitate to forecast a very cold Winter if it were not for a rather mixed signal from the Pacific where no key influence on the pressure patterns can be identified and the increased probability of a mild February.

Precipitation will be below average due to the influence of northern blocking and residual anticyclones (from northerly incursions) sat close to the UK.

Beyond the Winter, and perhaps the strongest signal of all, is for a very much below average start to March 2007 as the impacts of the breakdown of the polar vortex, blocking and cold air are felt.

Detailed factors

This is my second winter outlook for the UK and western Europe which pulls together the lessons from last year and observations since the summer based on:

The likely leading mode of the Arctic Oscillation (AO);

The likely leading mode of the North Atlantic Oscillation (NAO);

The impact of a weak to moderate strength El Nino;

Sea surface temperatures of the Pacific and Atlantic;

Madden Julian Oscillation (MJO);

Analogues;

Long range model outputs.

Before developing the forecast further, it should be borne in mind that long range forecasts are highly experimental and cannot claim a high degree of accuracy at this stage comparable to shorter term forecasts.

In developing these forecasts, we need to be able to experiment, to develop ideas and learn from mistakes. Please feel free to comment on any particular aspects of the forecast which you agree or disagree with, but please also enter into the spirit of the forecast and refrain from general comments about the efficacy of long range weather forecasting which have been stated on many occasions elsewhere.

The Arctic Oscillation (AO)

Learning:

http://jisao.washington.edu/ao/

http://www.arctic.noaa.gov/detect/climate-ao.shtml

The Arctic Oscillation (AO) is a key indicator of mean pressure between the North Pole and the sub-tropics. When the AO is negative, colder air is allowed to escape from the Pole to mid-latitudes whilst when the AO is positive, the cold air is bottled up over the Pole. The AO index is a useful measure of how much blocking there is over the mid and higher latitudes and, for western Europe, this is the primary influence on our weather patterns. Any successful Winter forecast will have to have a good handle on the AO.

Over the last few months, the AO seems to have acquired an even greater significance in influencing our weather. Remember the record breaking June and July period ? That followed the second most positive Summer AO index in the last 56 years. I would attribute this to the warm surface of the North Atlantic and colder seas around the Azores which helped to rapidly shift tropical air northwards when the AO was in a favourable 'mode' to this.

During the 1950 - 1970 period there was a marked tendency or regime for negative AO winters whilst in the 1990s there was a shift towards much more positive AO winters.

The recent historical trend shows a downward trend for the AO, in other words, it is trending negative with more blocked conditions over the Pole and colder air displaced to mid-latitudes such as western Europe. My own analysis of the AO taking rolling averages for months with a negative sign suggests that we are on a par with the 1960s and 1980s in terms of decadal comparisons.

post-2478-1164736419_thumb.jpg

Statistically, the winter months are most likely to witness a negative AO due to seasonal weather patterns - snow and ice cover in particular. However, we must factor in a secondary consideration here, that of the influence of the Quasi Biennial Oscillation (QBO).

Learning:

http://ugamp.nerc.ac.uk/hot/ajh/qbo.htm

http://jisao.washington.edu/data_sets/qbo/

The QBO is a high altitude wind over the equator which has two phases (west or east), each lasting between 8 and 18 months in response to solar cycles. The QBO is regarded as a key influence on the strength and positioning of the jet streams, the global heat exchange processes and indeed the Arctic Oscillation which makes it an invaluable seasonal forecasting tool.

A positive or westerly phase QBO is thought more likely to influence positive AO conditions (less blocking) and conversely, a negative or easterly phase QBO is likely to influence more negative AO conditions.

We are currently in a westerly (+ve) phase of the QBO which started in April and reached an index value of +10.86 in October. Typically these westerly phases last (a little shorter than the easterly phases) between 8 and 11 months which places the switch over to an easterly phase sometime early next year - most likely late February into April. Interesting to note that on just one occasion has the QBO been positive in December and not been positive in February - in other words, going into December with a positive QBO makes it likely that it will stay that way all Winter.

The science behind how the QBO and AO are related is complicated and not fully understood but it is potentially related to gravity waves and their narrowing of the Arctic air masses allied to increased upper level cooling by the generation of aerosols and Ozone. The reanalysis below shows this relationship between polar air temperatures and the QBO quite nicely:

post-2478-1164736634_thumb.jpg

Remember this is a correlation reanalysis so these are not actual temperature anomalies but degrees of relationship with the QBO. Blues and purples denote an inverse relationship (+ve QBO = colder air). Colder air around the Pole at upper layer drives a faster polar vortex which helps to sustain negative height anomalies and higher pressure around the mid-latitudes (mild SW'lys for the UK and western Europe). This reanalysis also suggests positive QBOs to have well defined layers of cold and warm air and an intact polar vortex.

There has never been an early breakdown of the polar vortex under a westerly QBO regime making it unlikely that all three winter months will see a negative AO. Combining the effects of the QBO on the AO gives the following trends:-

During December a neutral - negative AO is favoured most (63% of 24 sample months);

During January a neutral - positive AO is marginally favoured although the split between all three states is pretty much equal chance;

During February a neutral - negative AO is favoured most (61% of 23 sample months) but with a -ve AO most likely of all three states.

There have been only 2 years where the QBO was positive and the AO negative throughout DJF. As such, I cannot have such a low-probability factor on my side so the Winter is unlikely to be highly blocked throughout, in other words, there will be mild, wet and windy phases of weather for western Europe at times - therefore no wall to wall cold.

The profile of the polar air mass has however varied considerably during October featuring a significant amount of warmer air and blocking compared to November which has reversed the trend with a more familiar profile of colder air associated with the westerly QBO.

post-2478-1164736958_thumb.jpg

This poses something of a forecast dilemma. October or November as the best guide ? I'm inclined to side with October in this case as it captures the start of the seasonal cooling trend rather than November which could be something of a bounce-back factor.

Overall I would consider a neutral - negative bias for the winter in terms of the AO, particularly given the October trend but this masking considerable inter-month variations such as that witnessed in November.

North Atlantic Oscillation (NAO)

Learning:

http://www.ldeo.columbia.edu/NAO/

http://www.cru.uea.ac.uk/cru/info/nao/

http://jisao.washington.edu/data_sets/nao/

The North Atlantic Oscillation means many things to many people. As a pure index it measures anomalies in sea level pressure across the Azores to Iceland driven by a range of factors such as snow and ice cover, sea surface temperatures in the North Atlantic, sun spot activity and influence of its 'big brother' - the Arctic Oscillation which together form the primary influences on Atlantic weather patterns.

The NAO may also be defined as a long term climatic variable with positive and negative phases spanning decades - much as the Pacific Decadal Oscillation does. In this form, the NAO could actually lead pressures anomalies rather than be influenced by them.

Over the last Century there have been notable positive and negative phases. The 1990s experienced a prolonged period of positive NAO whilst the last few years have seen a possible resurgence of negative phases although this is a long way from being conclusive - the signs are tentative at best.

However, consider the long term trend:

post-2478-1164736701_thumb.jpg

This year, the period August - October experienced 3 consecutive negative months and the most negative on record. If we look at the sea surface temperature anomalies (SSTAs) in the North Atlantic, we can see a specific arrangement of warm-cold-warm bands. Although not convincingly obvious, this is indicative of a negative North Atlantic Oscillation.

post-2478-1164736461_thumb.jpg

http://weather.unisys.com/surface/sst_anom.html

There has been a tendency for this pattern of anomalies to actually intensify in the last few weeks:

post-2478-1164736974_thumb.jpg

Over the last 6 weeks, there have been anomalously strong high altitude zonal (west to east) winds over the Azores and Greenland allied to weaker ones over the North Atlantic. This is a classic match for a negative NAO which has also helped to maintain cooler air and stormy weather around the Azores. This has manifested itself in lower sea level pressure over this region which is likely to be self-sustaining within a feedback loop.

post-2478-1164736890_thumb.jpg

We are also at the low point of the solar cycle with decreased sun spot activity which is a feature of negative NAO years. The 2006 hurricane season was memorable not only for the shortfall of predicted storms making landfall but also recurvature of them into the mid-Atlantic which is also thought to be indicative of a negative NAO phase.

All of these factors strongly imply that we are heading for a winter heavily influenced towards a negative NAO. A negative NAO winter looks like this for western Europe favouring cold conditions, typically 2-3C below average. These reanalysis depict the pressure anomaly pattern and associated temperature deviations with higher pressure over Iceland and lower pressure over central southern Europe driving easterly and north-easterly winds across Europe.

post-2478-1164736720_thumb.jpg

El Nino Southern Oscillation (ENSO)

Learning:

http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/eln/home.rxml

http://www.atmos.washington.edu/gcg/RTN/rtnt.html

El Nino is a well known phenomena of the Pacific Ocean involving warming of the equatorial seas resulting in global impacts on weather patterns. Since the late Summer we have observed El Nino conditions developing and they continue to do so.

There are several measures of El Nino but my favoured one is the Multi variant El Nino Southern Oscillation Index (MEI) which as the name suggests measures a range of factors. During October the MEI was recorded at 1.027 and this places it in the weak to moderate category. The consensus of global forecast models is that this El Nino will peak in the early part of the Winter and decrease in intensity thereafter. Whilst this is a forecast and there is a large spread of predicted strength, there is also a reasonably strong agreement from models that this will stay within the moderate range up to an index value of 1.5.

http://iri.columbia.edu/climate/ENSO/currentinfo/SST_table.html#figure

The ECMWF modelling for this is one I would consider the best and I quite happy to accept that this will not develop into a full blown strong El Nino event. To do this, November's MEI would have to be at least 1.4 and continue upwards. Whilst we could conceivably achieve a higher value by the Spring, the values for the Winter look to be in the 1 to 1.5 range, particularly given the impact of sea surface temperatures in the Pacific which are resisting a basin-wide ENSO event.

Weak to moderate El Ninos have a very specific pressure anomaly pattern in terms of high altitude zonal winds, vector winds (at the level where most of our weather is influenced), pressure at higher level and sea level pressure.

The key points are: the stronger Pacific and Sub tropical jet streams; the southwards displaced polar jet in the Atlantic; the positive height anomalies over Greenland and Iceland indicative of blocking; and, the cyclonic (clockwise) circulation in the central Atlantic indicative of lower pressure.

Whilst the observed November pattern has deviated from this a little (most probably related to the polar airmass and not El Nino), October was a perfect match for a weak to moderate El Nino in terms of the Atlantic circulation - although the negative NAO was obviously an important factor.

In terms of the Pacific, El Nino has not really shown itself and here we are faced with a dilemma. The surface waters of the Pacific continue to show a negative Pacific Decadal Oscillation (PDO) signature which if anything has intensified of late. This is completely at odds with El Nino and the story of the Autumn has been of a weak strength PDO dominating the pressure patterns.

post-2478-1164736937_thumb.jpg

This is another reason suggesting that El Nino will not gain in strength as it is having to fight the PDO, indeed, this has never really happened before over anything more than one winter month and could be a recipe for a highly unstable weather pattern.

This could also be significant in terms of reducing and convoluting the amount flow jet flow across the Pacific as well as shifting the polar 'envelope' towards the eastern hemisphere making it more likely for cold over Europe.

However, the Atlantic could be conducive for a more stronger and much milder El Nino response and other factors will be key in determining the overall potential for this to happen.

The trends shown by weak to moderate El Nino winters are for notable inter-month variability. Decembers vary but tend to fall as slightly above average. Januarys show notable cold encroaching from the east whilst February's show a marked preference for above average conditions for western Europe and the UK.

It's worth noting that weak to moderate El Nino's strongly favour the development of deep cold in central and eastern Europe which is to be expected given the dominance of a strong sub-tropical jet allowing cold air to seep south and west from the Siberian rim.

Note also a trend for El Ninos to deliver generally southerly winds to the SW of the UK and easterly winds to the north. This battle between warm and cold sources essentially explains why El Ninos tend to be quite varied over the three winter months - it is the placement of the easterlies and deflection southwards that is crucial.

Atlantic Sea Surface Temperature Anomalies (SSTAs)

For my last two seasonal forecasts, I have based my outlook on a 1 month lag. Both forecasts have verified best at the end of the outlook period and as a result I am basing my assessment of Sea Surface Temperature Anomalies (SSTAs) on a much earlier August to November reanalysis.

If we look at the North Atlantic SSTA for this period, we see the following:

post-2478-1164736461_thumb.jpg

1) A subtle difference in anomalies north to south with the northern band from the UK across to Newfoundland warmer than that to the south from Portugal to Florida which is a dipole in favour of a negative NAO.

2) The area of weaker positive and neutral SSTAs coincides with the same area favoured for cyclonic pressure sustained by the El Nino event.

3) The dynamic changes in the anomaly pattern may also be important with a reinforcement of the Atlantic Tripole over the period August through November to date:

During September a large pole of anomalously warm water moved from Newfoundland northwards into the Davis Straights. This peaked around the 28th October and has continued to present which has massive implications in terms of blocking (forcing of the jet northwards into Greenland) and helping to 'tank' a negative NAO from late December onwards.

http://weather.unisys.com/archive/sst/sst_anom-060903.gif

http://weather.unisys.com/archive/sst/sst_anom-061008.gif

http://weather.unisys.com/archive/sst/sst_anom-061029.gif

http://weather.unisys.com/archive/sst/sst_anom-061119.gif

Taken together these point strongly towards a negative NAO with low pressure to the central Atlantic and higher pressure to the north for a sustained period of time although the warm anomalies across the Mediterranean and around the Canaries are likely to favour weak ridging and winds from the south west (picked up by the analysis of zonal wind flow).

Pacific (SSTAs)

post-2478-1164736444_thumb.jpg

Looking at the Pacific SSTA, we can see the following:

1) A warm western Pacific which is indicative of a negative Pacific Decadal Oscillation pattern.

2) A warm pool over a smaller cold pool in the central Pacific. This is a powerful arrangement or couplet likely to displace the Pacific High northwards towards the Aleutians.

3) A developing band of cold water to the NE Pacific and a smaller cold pool to the south which are likely to support troughing into the eastern Pacific, sometimes extensively so when in combination with El Nino (note how the circulation associated with El Nino and SSTAs are overlapping as in the Atlantic).

Taken together these factors point towards a quite variable flow pattern in the Pacific with a very definite trend towards split jet and often amplified flow across North America.

Analogues

Analogues used to compare previous weather patterns with similar circumstances to try to predict the outcome. I wouldn't advocate an approach which tries to match all variables but ones with similar profiles are useful to benchmark against. The key factors for analogue selection this winter are:

1) Weak to moderate El Nino with MEI 0.5 to 1.5

2) Negative NAO

3) QBO westerly (+ve)

4) Similar SSTA for Aug-Nov period for verification

This produces just 3 (low sample caution!) analogues of 1957/8, 1963/4 and 1977/8 and none of these are perfect although they are good in terms of October temperature and November patterns so far. I was sorely tempted to add 1969/70 on the basis that it has verified extremely well from the Summer and although not an El Nino event, it had an Atlantic SSTA which mimicked the effect of El Nino. These 3 analogues have however thrown out a strong tendency for positive height anomalies to our north but with an overall winter at or just below average.

post-2478-1164736542_thumb.jpgpost-2478-1164736502_thumb.jpgpost-2478-1164736479_thumb.jpgpost-2478-1164736525_thumb.jpg

Tellingly, the constructed analogue for the polar thermal structure is very different to what would be expected with a marked preference for the polar vortex over Siberia - a recipe for deep cold to develop in the Russian interior and high probability of blocking over Canada and Greenland. During October and early November, these patterns were beginning to show up although they have fallen back a little of late.

post-2478-1164736617_thumb.jpg

The SSTA verification for these analogues which show important warmth to the North Atlantic, cold to the SW Atlantic and Pacific similarities.

post-2478-1164736659_thumb.jpg

Madden Julian Oscillation

Learning:

http://www-das.uwyo.edu/~geerts/cwx/notes/chap12/mjo.html

http://www.bom.gov.au/silo/products/iso.shtml

The Madden Julian Oscillation is a Kelvin Wave generated in the equatorial Pacific and Indian Oceans which is propagated around the planet. Its effects are only now being understood and modelled although this remains very much an emerging area of seasonal forecasting.

Conditions in the Pacific, Indian and Atlantic Oceans remain favourable for the development of waves which tend to last 45 - 60 days. There is also a relationship between El Nino, the MJO and QBO with the AO also possibly influenced indicating the potential importance of this oscillation on global pressure patterns extending far beyond the equator.

During September and October there was a moderate strength wave event. The next Wave has just begun following a brief lull in the Indian Ocean. There are 8 phases to each wave, each with a specific pressure anomaly pattern. Although not thought likely to bring about these patterns by itself, the MJO is believed to pep up or dampen particular pressure anomaly patterns such as that associated with El Nino or NAO.

These associated pressure anomalies become more pronounced the stronger the wave. This year, we have already experienced 1 moderate strength wave with every chance of one or more similar or greater magnitude events to follow. Make no mistake, there is considerable potential for the MJO to be a leading player this Winter.

Of the 8 wave phases, December and January are associated with more favourable set-ups for northern blocking, especially within phases 1, 7 and 8 although phases 2 and 3 would also be considered favourable for height rises during January. February is noted for a lack of phases associated with cold weather.

http://www.bom.gov.au/bmrc/clfor/cfstaff/m....Last40days.gif

Current assessment of the wave and projections for the Winter suggest December to run through phases 4 - 8, a new wave to begin sometime in late January with phases 1 to 6 falling across Jan and February. March is likely to experience phase 7 and 8 phases on current projections although these timings will only be confirmed nearer the time. Crucially, much of January looks to be timed with a neutral 'between wave' period which should allow the Winter 'default' pattern to establish.

Long range model outputs

http://www.cpc.ncep.noaa.gov/products/people/wwang/cfs_fcst/images/glbT2mSea.gif

http://www.met-office.gov.uk/research/seasonal/monthly_forecasts/single_terce2.html

http://iri.columbia.edu/climate/forecast/net_asmt/2006/oct2006/DJF07_World_temp.html

http://ecpc.ucsd.edu/projects/GSM_home_data/latest/TMP2.latest.ano_global.gif

http://www.climaprog.de/website1006004.htm

http://www.climaprog.de/website1006005.htm

http://www.climaprog.de/website1006006.htm

http://www.cdc.noaa.gov/seasonalfcsts/

http://www.cdc.noaa.gov/cgi-bin/seasonal/nmethod.pl?method=6&initial=71&units=%2Ffcst&Submit=Create+Plot

A real dichotomy of outputs with IRI, UKMET, ECPC suggesting mild with any cold shunted far east, the CFS which suggests building cold into the later stages (UKMET also hint this) and German Climaprog going for a much colder synoptic.

Over the Pacific, there is some agreement for a Gulf of Alaska low and highly amplified pattern across the US with a strong sub-tropical jet in evidence consistent with El Nino (although UKMET and ECPC look to have modelled this differently with more of a widespread cold across the southern US). Much of this variability is I suspect related to differences in each model's interpretation of the El Nino strength (e.g. UKMET go the strongest El Nino and a mild outcome for the UK).

Forecast Discussion

This Winter will be one of large fluctuations in temperature and pattern. The likely variability of the Arctic Oscillation (AO), the underlying negative North Atlantic Oscillation (NAO) allied to the residual summer warmth, Madden Julian Oscillation (MJO) and contradictory PDO / El Nino signal will confer a high degree of instability across the Northern Hemisphere. With the solar minima now upon us and cold air on tap, this promises to be a very dynamic and potentially high impact Winter.

Average temperature values will be less meaningful given the variability, primarily influenced by the Arctic and North Atlantic Oscillations which I see as the key factors this winter overlapping the El Nino signal. With no breakdown of the polar vortex likely until late February at the earliest, and the influence of the westerly Quasi Biennial Oscillation (QBO), it is likely that the polar vortex will be characterised by alternate periods of activity resulting in big swings in the Arctic Oscillation.

Recent increases in snow-cover, the anomalous profile of the polar troposphere, observed Autumn trends and the impact of El Nino / NAO suggest however a high degree of blocking and this will impact on the displacement of the polar jet stream to the south of the UK for large periods of time, even under more mobile Atlantic flow pattern.

For me the single the key long term feature of the winter forecast has to be the NAO. Sea Surface Temperature Anomalies (SSTAs), historical evidence, October pressure analysis and the reinforcing effects of El Nino have, and will continue to, set up feedback loops in the atmosphere ensuring that we stand a high chance (65%+) of experiencing at least 2 months with a negative NAO.

Reanalysis of negative NAO and El Nino conditions suggests strongly a cold pool of air to develop deep into Siberia during December and for this to extend westwards during January reaching a peak at the end of this month. The forecast is for temperatures of central and eastern Europe and Scandinavia to be substantially below average with lower than normal amounts of precipitation associated with negative NAO conditions.

The key question is whether all this cold air will be able to make its way towards the UK and on time ? The answer to this is not clear cut. When the AO / NAO combo is favourably negative, this will make the cold's journey westwards that bit easier. However, this not guaranteed all winter so we also need to look at the upstream Pacific and Atlantic Jet streams and the impact of the Madden Julian Oscillation (MJO).

Many long range forecasts are suggesting a positive Pacific Decadal Oscillation (PDO) to be a sure thing. A positive PDO is related to a positive Pacific North American Pattern (PNA) which would be good for delivering cold shots to the UK. However, I do not agree that the PDO will recover from Summer / Autumn negative values quite so quickly - the lag effect of the SSTAs (particularly that cold over warm pool in central Pacific) will engender something of a confused Pacific Jet alternating high and low pressure across the Aleutian Island Chain in the central northern Pacific.

This is slightly different to a classic positive PDO / PNA and potentially it could really enhance any cold shots for western Europe through its downstream impacts on the Polar Jet by deflecting it way southwards or even over the top of Greenland helping to maintain positive heights and blocking there alternated with more flatter trajectory jet over the northern 'States. It should be noted however that there will be phases when the jet flow is much less amplified across the USA and these intervals can be expected to produce much milder interludes for the UK as pressure rises in the west Atlantic and sustains a more southerly flow to the UK.

The most likely time for conditions in the Pacific favouring easterly winds is towards the end of January when the jet will be at its weakest.

Also of likely influence is the MJO. Current projections suggest the more favourable phases of the MJO for cold weather and blocking to fall at the end of December into January, the end of January and early March. They strongly suggest that February will be associated with a cold start but rapidly moving to milder patterns for western Europe (a potentially snowy breakdown or battleground scenario the like of which we have not seen since the 1980s) - which is also supported by the analogues and the warm seas around the Canaries.

There is some doubt about the timing of MJO phases in January and at present I favour the MJO to be between Waves during this time which will allow the 'Winter default' to emerge as the dominant monthly pattern. This could be devastatingly crucial as it is likely to coincide with the lag effect of that warm pool of water moving northwards into the Davis Straights sustaining a prolonged and 'tanked' phase of the NAO and AO with intense blocking over Greenland allowing cold air to penetrate the UK from Europe and the Arctic.

Although there is low sample of analogues, these have verified extremely well in terms of the October and early November period and I am prepared to follow their lead in suggesting an average or slightly below average Winter for the UK and colder still for much of mainland Europe - in spite of the rather different November signal for mild.

The key aspect of the forecast is just how much of a negative NAO there will be to force the generally mild Atlantic flow southwards being replaced with colder air from the north and east.

On the premise of the 65% plus chance of at least 2 months seeing negative NAO conditions allied to the MJO favouring cold shots in December, January, the beginning of February and the Autumnal movement of warm pools of water, I favour marginally colder than average Winter for the UK, typically in the range 0.5C departure from the Central England Temperature but less so for Northern Britain. In terms of precipitation, the amount of blocking will lead to a drier than normal Winter leading to continued water shortages next Summer.

post-2478-1164736681_thumb.jpg

There is a risk that the forecast cold could be greater if the QBO weakens rapidly into December which would allow for more prolonged blocking phases. A strengthening El Nino on the other hand could completely derail any NAO / AO conditions making it a milder winter more likely.

Finally, we should consider the implications of widespread heavy snow which is a realistic prospect borne out of a highly variable but cold pattern. It has probably been over sixteen years since we experienced a similar snow event. Since then, pressures on the transport infrastructure have increased dramatically whilst few people have experience of driving in snow. Consider also that the very localised snow events of recent years have paralysed parts of the road and rail network and a widespread snow this Winter has the potential to cause significant disruption.

Looking further ahead, March could witness the breakdown of the Polar Vortex and coupled with a hemisphere coming out of an anomalously cold winter and a favourable MJO phase pattern, this could present an explosive combination for Winter to be extended and end with a final snowy crescendo.

Glacier Point, issued 28th November 2006

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...