Winter Forecast - 2011/2012

[Glacier Point]

Indeed, I think we've gained a lot of valuable know-how with cold vortex events, this one running beautifully along the lines set out by Baldwin and Dunkerton.

Compare the first plot which shows height anomalies throughout the atmosphere over the winter across the Arctic with the profile produced by Baldwin and Dunkerton, and note the state of the Arctic Oscillation at the bottom. The periodicity of the event was almost to the day from mid November through mid January.

[TEITS]

For Feb 1st, there was a solid and strong -NAO signal, manifested in the low heights and temperatures over Europe whereas the CPC index implies a neutral NAO !

Am I right in saying though that the LP was centred towards Italy with 1025mb around the Azores on the 1st Feb. Obviously the pressure, temp across Europe has no impact on the NAO because its measured from the Azores to Iceland.

Going back to the rainfall and I must admit im concerned and I know the farmers in E Anglia are especially concerned. I seem to recall your forecast said above average rainfall in the S but this is unlikely to rectify the drought conditions. Like I said we have only recorded 70mm so far this winter so its looking very doubtful we're going to reach above average values.

I suppose what im saying is many members judge the forecast based on cold and snow but would a farmer in E Anglia say the same. If a forecast predicts above average rainfall but the reverse is true, can the forecast being synoptically correct?

[Glacier Point]

Am I right in saying though that the LP was centred towards Italy with 1025mb around the Azores on the 1st Feb. Obviously the pressure, temp across Europe has no impact on the NAO because its measured from the Azores to Iceland.

The plot shows a height anomaly of around 50m for the Atlantic sector around the Azores and around 150m for Icelandic region. Roughly, that equates to a NAO value of around -3 allowing for the loading pattern.

The temperature profile across NW Europe is strongly correlated to the NAO, especially during the winter months January and February. What we experienced in late jan / early Feb was a direct result of the pressure patterns associated with a strongly negative phase of both the NAO and AO. Pictured here is the linear correlation for 850hPa temperatures with the NAO. This inidcates a positive correlation of around 0.7, which allowing for the 'white noise' within the atmosphere, is a pretty strong correlation so when the NAO is negative, temperatures across Europe are well below average.

W/r/t to your point about farming, this is a very specialised forecast which needs to take account of soil moisture deficits in addition to temperature and precipitation. Had we issued a specific forecast for a company in this sector, this would have also been factored in. For East Anglia, the guidance would have been something along the lines of "net increase in soil moisture deficits and average ppn signal" (note the guidance anlaogue for rainfall was for southern counties of England).

There is another point here in how people use seasonal range forecasts. They can at this stage not be used on a localised basis. Parts of the south-west have received above average rainfall whilst East Anglia will probably end up slightly below - the two areas are only 150 - 200 miles apart and for a seasonal range, that detail could not be resolved. You need really to look at the eficacy of seasonal forecasts on a European basis as a minimum.

Edited February 14, 2012 by Glacier Point

[karyo]

_{I think overall, GP has made a pretty good winter forecast. It would be more interesting to talk about what the rest of February and March holds than argue on how accurate or not a forecast has been.}

_Karyo

[Isolated Frost]

I'd like to applaud GP's forecast, again.

The use of composites have proved invaluable again, and the general pattern matching has been superb- the prediction of the NAO and AO, along with stratosphere, with help from MJO and GWO predictions and the timing of these transitions is a real indication of how weather forecasting from those who look at the teleconnections and wider oscillations has advanced- these predictions have been invaluable and really well done to Ed and Stewart amongst others on the site.

GP's signature is something maybe all of us should take in hand.

Not every winter will deliver prolonged cold for all of the UK- the fact that there was a seismic change in the hemispherical pattern during January really does highlight the efficiency of your work GP and others of course.

A great forecast and I must ask- do you plan to do a Spring one in such detail? That would be really useful- however AFAIK predicting Spring and Summer is so much harder due to the less mobile and active pattern in the N-Hemisphere.

[BLAST FROM THE PAST]

GPs forecast progressed nicely but it has now broken down and is heading very much in the wrong direction. Remember, unless I'm mistaken the northern blocking is supposed to be further solidifying as Feb progresses? it isn't and has rapidly declined so something has changed/overriden his teleconnection composite signals.....as it does seem to to do to all others. Further assessment at end of forecast...at one point it was looking good, this breakdown and lowering heights are somewhat attacking this and I don't think the pressure pattern forecast and observed in Jan was that close? I hope indeed the reload GP spoke of comes soon....a very good effort thus far though.

BFTP

Edited February 14, 2012 by BLAST FROM THE PAST

[karyo]

I hope indeed the reload GP spoke of comes soon....

BFTP

This is looking very unlikely now. However, GPs winter forecast came closer to what actually happened compared to any other I have seen.

Some people were predicting a bitterly cold January...

Karyo

[jethro]

As a non model reading numpty I cannot comment on specifics but there have been many times throughout the winter when the daily models have thrown out solutions which haven't actually happened. There have also been many times when the models have suggested one thing and folk have been quick to despair, GP amongst others have said ignore the daily micro detail and look to the wider, hemispherical patterns - they've been right, the daily doodles have not shown an accurate, long-term picture, and there's no reason to presume they have suddenly become more accurate.

Personally speaking, I think GP has been incredibly accurate with his forecast. If the last couple of weeks of Winter prove not to be what he predicted then I'll happily say "so what"; a forecast made in November for weather in February deserves a bit of leeway, more so when the rest of the Winter was so accurately forecast.

[BLAST FROM THE PAST]

As a non model reading numpty I cannot comment on specifics but there have been many times throughout the winter when the daily models have thrown out solutions which haven't actually happened. There have also been many times when the models have suggested one thing and folk have been quick to despair, GP amongst others have said ignore the daily micro detail and look to the wider, hemispherical patterns - they've been right, the daily doodles have not shown an accurate, long-term picture, and there's no reason to presume they have suddenly become more accurate.

Personally speaking, I think GP has been incredibly accurate with his forecast. If the last couple of weeks of Winter prove not to be what he predicted then I'll happily say "so what"; a forecast made in November for weather in February deserves a bit of leeway, more so when the rest of the Winter was so accurately forecast.

I'm sure he will, however, transient is an expression I feel will best describe the rest of Feb. There is nothing to suggest on 500mb graphs, models or indeed my method for prolonged northern blocking until say end of month at earliest. With some luck we could still get some nice cold shots for some.

BFTP

Edited February 14, 2012 by BLAST FROM THE PAST

[jethro]

I'm sure he will

BFTP

?????

[jethro]

Blast - when you edit your posts to answer subsequent questions, it all gets a bit messy and confusing. It reads much better for everyone if you respond with a separate answer, otherwise the questions I, or other people ask are left hanging in mid-air.

[TEITS]

Rather than using graphs to look at the NAO i've taken the old fashioned approach of looking at the actual recorded SLP over Lisbon & Reykjavic.

Recorded SLP in Lisbon on the 1st Feb was 1019mb. Recorded SLP in Reykjavic on the 1st Feb was 1014mb. Although very little difference with pressure, due to being slightly higher over Lisbon suggests to me the NAO was neutral. At no stage during Feb so far has pressure ever been higher across Iceland compared to Lisbon.

Here are a few more interesting stats from these areas.

Across reyjavic this winter the SLP has often been around or below 1000mb with the exception of a few days recently when the pressure rose to 1025mb. See diagram below.

Across Lisbon the SLP has often been around 1025mb with the highest recording being 1036mb and the lowest at 1017mb. See diagram below.

If you live in NW England, SW England, Scotland, Ireland, Wales and you're wondering why this winter has been such a disappointment then your answer lies above!

Edited February 14, 2012 by THE EYE IN THE SKY

[Bristawl Si]

A bit early yet to pass judgement on GP's winter forecast in my view, as Winter hasn't finished.

Seems to be pretty accurate so far - December and January pretty much spot on - February good start, but looking shaky for remainder.

I think, generally, even though i believe it wasn't 'officially' published, the MetO has been pretty good as well.

Winter '11/'12 hasn't delivered in terms of 'wants' in these parts though - in fact poor from a snow perspective - come to think of it v poor!

Question for the more knowledgeable on NW - whatever has happened to those Channel Low events the South West used to see in many a winter? - sometimes only 1 or 2 each winter (and not every winter i know) but they weren't uncommon 25+ years ago. I've seen archive news stuff that documents these events as quite common from the 19th century and up to the 1980s.

[UV-RAY]

IMO GP got December, January, and the first half of this month spot on, although the cold certainly wasn't as widespread as forecast. On a separate note the Strat thread has been a revelation this winter, and certainly highlights the importance of having stratospheric warmings earlier in the season.

[Glacier Point]

So here's the really interesting analysis so far.

The forecast was premised on the 2nd half of the winter being different to the first in terms of pressure and temperature anomalies, the first half forecast to be relatively mild with south westerly winds and lower pressure to the north, higher pressure to the south.

The second half was forecast to be colder with pressure higher to the north than normal and lower than normal (remember wind flow is relative between pressure differences) to the south with winds from the east.

So here we go.

1st half temperature and pressure anomalies

2nd half temperature and pressure anomalies

Striking don't you think ? The key question will be how much these will get eroded in the next two weeks. I would suggest that given the magnitude of both, they'll still be present by months end. Indeed, the current temperature anomaly for the UK suggests the southern half to be 5C below average.

It's interesting that during the December of 2010 there was some criticism that even though December was singled out as the month where below average temperatures were forecast, this failed to identify a huge negative anomaly. This February, I'm currently too warm against the -5C anomaly. So ironically a slighter mild period will do just the ticket. If February comes in below average (suggest more than 0.5C below average), with a pressure anomaly with high pressure over Scandinavia and lower pressure over southern Europe, that is all that will be required for the forecast for Feb to verify. Also note where the original forecast analogues suggested the cold air to come from and the difference across the UK north-west to south east.

Rather than using graphs to look at the NAO i've taken the old fashioned approach of looking at the actual recorded SLP over Lisbon & Reykjavic.

Recorded SLP in Lisbon on the 1st Feb was 1019mb. Recorded SLP in Reykjavic on the 1st Feb was 1014mb. Although very little difference with pressure, due to being slightly higher over Lisbon suggests to me the NAO was neutral. At no stage during Feb so far has pressure ever been higher across Iceland compared to Lisbon.

Here are a few more interesting stats from these areas.

Across reyjavic this winter the SLP has often been around or below 1000mb with the exception of a few days recently when the pressure rose to 1025mb. See diagram below.

Across Lisbon the SLP has often been around 1025mb with the highest recording being 1036mb and the lowest at 1017mb. See diagram below.

If you live in NW England, SW England, Scotland, Ireland, Wales and you're wondering why this winter has been such a disappointment then your answer lies above!

Dave - you need to supplement your analysis with the mean pressure for each area and then the standard deviation for both data sets to work out the real value of the NAO, after all, pressure and wind flow is relative to areas of high and low pressure.

[Isolated Frost]

Good analysis there GP.

Btw for further reference do you have a link to that normalised GPH anomaly 65N-90N chart? Thanks.

[chionomaniac]

Stewart, I think that you have correctly predicted the pattern of winter so far and do not think that you need to spend so much time reasoning and providing a retrospective analysis whilst winter has not finished yet. If I remember rightly there are a lot of other forecasts that were well out before December was two weeks old.

[damianslaw]

Good analysis from GP - will we be treated to a spring forecast as well in the coming days?

[feb1991blizzard]

The main point here is that what ever little holes that can be picked in the forecast (which you are always going to be able to do with any seasonal forecast), it has been the most accurate out of all the ones for this winter that i have seen, added to the fact that last winters was also very good, and the fact that the MO refuse to publish a seasonal forecast anymore, which with all the money and resources at their disposal must suggest that seasonal forcasting is still very difficult and in its infancy, then i have to say hats off to GP, quite a staggering effort really, especially to predict exactly where and when blocking would occur (backed up by sound reasoning), the fact that it didnt end up the dream Easterly from an IMBY perspective doesnt detract from how good a winter forecast it was, and as you say GP, its ironic that a spell of mild muck now will mean that your temperature anomaly prediction will be even more accurate than it would of otherwise of been, many thanks for sharing your knowledge of teleconnections and the stratosphere and same goes for chionomaniac.

[BLAST FROM THE PAST]

Blast - when you edit your posts to answer subsequent questions, it all gets a bit messy and confusing. It reads much better for everyone if you respond with a separate answer, otherwise the questions I, or other people ask are left hanging in mid-air.

Editing is needed sometimes, depends what computer set up one is at. I too think GP doesn't need to explain too much at present....although it isn't as accurate as some are proclaiming as for me Jan anomalies according to GP's post seem a wee bit different and are worth looking at again as its interesting how it didn't fall into line...why?. Most accurate thus far? Could very well be/probably.....top effort

BFTP

Edited February 14, 2012 by BLAST FROM THE PAST

[johnholmes]

I too think GP doesn't need to explain too much at present....although it isn't as accurate as some are proclaiming. Most accurate thus far? Could very well be.....top effort

BFTP

have a look at my quick summary of the lrf issues last autumn BFTP-you will see GP is way ahead of anyone else even if the 2nd half of February turns out not as his forecast suggested

[BLAST FROM THE PAST]

have a look at my quick summary of the lrf issues last autumn BFTP-you will see GP is way ahead of anyone else even if the 2nd half of February turns out not as his forecast suggested

Indeed John, I'm clearly not disputing that GP's forecast is about the best, but its going very wrong now and Jan isn't synoptically as forecast? Why?...and why has the warming in the stratos NOT provided the blocking anticipated. Reasonable non confrontational questions...even the best has / is failing /breaking down. Let's see if these can be answered over time

BFTP

[Osbourne One-Nil]

The things I like about GP's forecasts are that they're clear, concise and unambiguous. I also like how he lets the forecasts stand on their own feet, doesn't spin them to his advantage, and doesn't gloat when he gets things right.

[TEITS]

Stewart, I think that you have correctly predicted the pattern of winter so far and do not think that you need to spend so much time reasoning and providing a retrospective analysis whilst winter has not finished yet. If I remember rightly there are a lot of other forecasts that were well out before December was two weeks old.

I do agree GPs forecast has been the most accurate out of all the LRFs I have read. However whilst Dec, Jan and the 1st week of Feb appear spot on, the model output at the moment for the medium range appears to spoil GPs forecast.

Sorry if im coming across as argumentative but im a little frustrated at the moment and I shall explain why. I will add my post is on topic because im discussing the rest of Feb which is related to GPs winter forecast.

Only recently I was accused of being biased due to my negativity of the model output because some suggested I was only referring to my region. Here is a selection of posts and my response.

Our ridge to the west is replaced with a trough and heights build somewhat over NW Europe. Note that the anomalouse ridge over NW Russia is persistent (this has been an omnipresent feature this winter) and shifts its position west. That is a good signal for easterly winds to re-establish over Europe.

The next move for angular momentum looks downward, and we should see the models start to play catchup in building heights to our NE and possibly north towards Iceland, particularly as AO and NAO variables look to be near average values.

Trouble is though GP any NW,ly looks to be brief before being replaced by a W,ly flow. Im not sure even below average conditions would occur because upper temps during this NW,ly phase appear to be only around -5 to -7C and due to the time of year I would expect max temps to still reach between 4-7C.

I think what we should all try to do, regardless of our geographic position in the UK, in this thread is try NOT to view life out of our own window, there are regional threads where discussions of the model outputs and how it may affect our area san be had. Surely the model thread is for UK wide; fine to comment on specific aspects but its not fair to do a summary from a local point of view.

My area has had one of the coldest starts to a February in a long time, better than a few years ago, and I have had a snow cover for 8 consecutive days(7 mornings). Folk further north and west have not.

So a less biased view folks if possible please?

IF the models are correct then obviously northern areas will do better than southern areas but its a case of swings and r-a-bouts in my view.

Certainly the 6-15 day 500mb charts show absolutely no sign of any mobile Atlantic weather which suggests blocking thus further cold shots seem probable.

I disagree with John because blocking doesn't look likely. When I refer to blocking I mean either a GH or a Scandi HP and neither are these suggested. If you have an Atlantic HP bringing NW,lys then with low heights across Greenland this cold is unlikely to be maintained.

Now considering the amount of flak I recieved and what the models are now showing you can see why im rather annoyed from a forecasting perspective. Like I say I take my forecasting seriously but it appears some are more impressed with technical posts rather than accuracy!

Edited February 14, 2012 by THE EYE IN THE SKY

[Methuselah]

Editing is needed sometimes, depends what computer set up one is at. I too think GP doesn't need to explain too much at present....although it isn't as accurate as some are proclaiming as for me Jan anomalies according to GP's post seem a wee bit different and are worth looking at again as its interesting how it didn't fall into line...why?. Most accurate thus far? Could very well be/probably.....top effort

BFTP

Because it's based on science, rather than wishful thinking?