Winter 2005/6 Forecast Review

[Thundery wintry showers]

A pretty good and objective summary there IMO. I still think that on the whole, these seasonal forecasts are holding up pretty well even though this specific winter one was overshadowed by the success of the MetO's.

[johnholmes]

interesting comments their Ian, and thank you for your data showing how the 2005/06 winter developed.

As to 2006/7, we have to wait and see if the factors you quote are more in place, all at the right time, later this year and early in 2007.

John

[Nick F]

I echo TWS and John's comments on a good analysis Ian. Certainly we have seen a turning point away from the dominance of mild Westerlies in winter which have been common each winter since 1988, and it'll be interesting to see if 2006/7 winter continues this theme. It'll be interesting to find out that the dominant wind direction has been this winter in the UK, as it certainly hasn't been the prevailing direction of SW'erlies meaning that it has been on the cool side this winter - but could have been colder if the Pacific jet and consequently the N'ern arm of the Atlantic jet weren't so strong earlier on. January certainly seems to be the stumbling block when it comes to getting an average or below average CET, and has Jan has been consistently mild in recent 'modern' winters. Though Dec and Feb are showing signs of bucking the above average CET trend. November was a nice suprise after a v. mild Sept and Oct aswell.

[Osbourne One-Nil]

I think I preferred the past ten winters to tell you the truth.

[pottyprof]

I think I preferred the past ten winters to tell you the truth.

and you sold how much of the white stuff on ebay??? in bottles?? or am i thinking of somebody else?? LOL :unsure:

i think ians forcast was pretty close to the mark regarding the patterns so well done you!!!!!!!!!!!!!!!!!

'By now, the seasonal forecast had gone wrong'.. no it didnt.. the patterns were there ian.. and at that range from the forcast.. you did a great job.. thanks for all your work.. this year has given us something that we wernt expecting given the last 10 years.. and you had it pretty much spot on for 2 months.. i dont see that as being something to be downtone about mate.. great forcast.. nice conclusion.. a1 ebayer.. a++++++++++++.. sorry.. wrong site.. :unsure:

[BLAST FROM THE PAST]

The winter was notable for it's lack of double figure maxima days. This was largely a result of the continuous blocking at mid and occasionally high latitudes. The classic mild set-up of a strong northerly jet and Bartlett High was almost completely absent.

I think that is quite possible that this winter could be a marker for winters over the next four or five years, with blocking patterns often prevailing.

[BLAST FROM THE PAST]

I think that your forecast Ian was very good and you are being a bit hard on yourself by saying it went wrong. Just correctly calling for a synoptically different winter is achievement enough against the total dross of so many past years. Your timing of particular events was not bad either really.

Lots to learn to take forward for next winter.

BFTP - it is very early as you rightly suggest - but what makes you think next winter will be mild? I presume you are hinting at Bartlett blocking for next winter in your references? It is far too early to know either way of course -but you have up to now supported the idea of pattern/synoptic change post Feb 2005. Or do you now think differently?

:blink:

Tamara

Tamara

No not Bartlett scenario we can have negative NAO and still be not cold as blocks may not be conducive to cold UK, and that was an early overall winter assessment (note Dec is of interest). I was looking at the MetO experimental LRF for the globe for next 6 months and they project Russia/Eurasia average to colder than average and the USA warmer bar Alaska. If that proves correct and continues then I think it is signalling/supporting the cyclical change I have mentioned as it has been the other way round overall now for over a decade or so. So clearly no I don't think differently

[JJB McCabe-deluxe edition]

I think I preferred the past ten winters to tell you the truth.

So have I, January in particular was a depressing miserable month with barely a hint of of sunshine or any kind of weather really! It just seemed to be a month of continuous grey gloom.

[The PIT]

This Winter was also remarkable for the lack of Gales. One of the calmest Winters for many a year.

[summer blizzard]

I believe that your long range forecast was just as good if not better than most other peoples and i say congratulations to that.

In regards to my own forecast for the winter, while my forecast based on sea surface temperatures was totally wrong, my forecasts based on teleconnection patterns were close to the mark with January and February being forecast a CET of 4.7C and 3.7C respectively with the real figures at 4.3C and 3.9C respectively, my March forecast is also looking to be close to the mark with a predicted CET of 5.4C and the real figure looking to be near 5C.

[mcweather]

Thanks for your hard work Ian and a fair forecast I think.

I also concur with your thoughts regards possible pattern set ups for next winter.

In the meantime for Winter lovers everywhere I recommend Paul R Browns excellent article in this months Journal of Meterology in which he looks at and describes the synoptic set ups during the winter of 1963.

Beware though, some of the charts are practically pornographic if snow is your thing

Thanks again Ian heres to next winter

[Thundery wintry showers]

Personally, I would say it was easily the second most accurate seasonal forecast available for the winter- the Met Office got theirs spot on this time around, but I haven't seen any seasonal forecast from another organisation that correctly identified as many of the trends for December and January as Ian Brown's did.

He wasn't the only one to go for a cold easterly in late January; in my monthly discussion issued at the beginning of January I also went for the easterly. Furthermore, it very nearly came off, but unfortunately when it didn't, it threw February off-line.

I think Ian did very well to correctly identify the trends, and indeed individual synoptic patterns, that featured during December and January- most of them were even correctly timed as well.

[BLAST FROM THE PAST]

Personally, I would say it was easily the second most accurate seasonal forecast available for the winter- the Met Office got theirs spot on this time around, but I haven't seen any seasonal forecast from another organisation that correctly identified as many of the trends for December and January as Ian Brown's did.

He wasn't the only one to go for a cold easterly in late January; in my monthly discussion issued at the beginning of January I also went for the easterly. Furthermore, it very nearly came off, but unfortunately when it didn't, it threw February off-line.

I think Ian did very well to correctly identify the trends, and indeed individual synoptic patterns, that featured during December and January- most of them were even correctly timed as well.

Careful TWS you'll make Ian blush. It did pick up trends and had good points but in fairness came across problems a few of us had. I would point out that Roger J SMITH was very very good and for me had more 'hits' than most. I also think that forecasts using 'other'methods stood up...but the main feature was the pattern change and 'some' predicted this from some time out, not through guesswork either. So well done to trend spotters

BFTP

[The Enforcer]

Good work Ian.

Unfortunately, snowy weather has now become obsolete in these parts. When winter is not mild it is replaced by 'raw' which consists of either dull and overcast, sunny and frosty or cold rain.

[acbrixton]

Ian thanks for your work and your objectivity: a pretty good effort I think.

What interests me is how the MO managed to get so much detail right even though their reasoning (based upon a negative NAO) was, in the event quite wrong?

It would be useful if we could have a similar post-mortem on Roger's forecast using quite different methods...

Regards

ACB

[Methuselah]

Well done Ian!

As TWS has aleady pointed out, the 2nd most accurate winter forecast after the Met Office. Also, your post-mortem is perfectly fair and objective. And, IMO, such objectivity is a rare commodity these days...

For my own efforts: my interpretation of the Met office forecast was spot-on, so the winter has not really disappointed me at all; my own thoughts, however (For a milder than average winter!), were way off-the-mark...

[kold weather]

Yes well done Ian.

What has pricked my ears over the last few weeks is the actual Jet stream diving to our south for a sustained length of time. This all fits very nicely into us entering the cold cycle, with Feb 05 being the first major cold hit from the east, then Feb-mid March 06 being the next major hit with this time a southerly tracking jet as well.

From looking at past transtions there is often 2-3 teaser winters before a severe winter so I feel there is a shot at a very cold winter in the next 2-3 years, whether it'll come off depends on things going our way but I think its possible considering how similar this period is to the late 70's before the big one came in 78/79.

[Glacier Point]

Thanks for your LRF review Ian. Although it had its downsides, the winter of 2005/6 went some way to re-define the even larger teapot and gave us some cause for optimism in the future.

Here is my review of the Long Range Forecast I made back in November (link here: http://www.net-weather.co.uk/forum/index.p...ndpost&p=487441) which draws out the main pluses and negative points, and which provides some possible pointers for next winter.

Overall I would draw a large positive from the trend away from the string of above average winters experienced over the last decade, a call made by my and many other LRFs. Whilst it might seem quite obvious now, the LRFs that called a below average winter were bold in the face of month after month, year after year of above average temperatures. Also positives of the LRF were the increased duration of the winter, dryness, strong Pacific Jet, displaced polar vortex and the CET for December and February called for.

Winter Summary

500 hPa anomaly MSLP anomaly surface temp. anomaly

As a major negative, I was totally wrong with January and the fact remains that this month IS the winter month for many where we see our best chance of widespread snow and once again it failed to materialise. Other negatives were the importance attached to the Madden Julien Oscillation (a forecasting error as you cant have a strong easterly phase Pacific Jet with this), and indeed the Quasi-Biennial Oscillation's (QBO) exclusion of blocking over Greenland.

Summer warmth - winter cold

One of the key factors influencing my winter forecast was the approaching solar minima. Many had argued that this was irrelevant and that the overall warming trend experienced over the last decade was the key determinant for our winter. A sizeable pool of cold air did however develop over the Arctic Ocean, Siberia and Greenland. This cold made its presence felt as far south as Iberia as well as much of Europe and this must be regarded as a near miss as far as the south of England is concerned. Notably the cold air over continental North America was lacking.

I would cite this distribution (if you push a balloon it distorts elsewhere) and reduced incoming radiation as the key causes - something which augers well for next year - the low point of the solar cycle. There will have developed a sizeable cold pool next winter - but we must note that the distribution of cold air must once again favour the eastern hemisphere.

Back in November I identified a combination of an active hurricane season (increased tropical Atlantic convection), neutral El Nino Southern Oscillation (ENSO) conditions allied to a warm September as possible signals of an impending reversal in the monthly warming trend. I think the dramatic shift in patterns during November which took an above average first half of the month to a below average second half of the month in some way may be attributed to this, as can in part the following December pattern.

So if we arrive in October with ENSO neutral (as they may well be) conditions, and a warm September behind us, take the tip, the cold will not be far away. The shift to weak La Nina conditions may however have promoted alterations in the Pacific and jet patterns over North America this time around.

The NAO

Many LRFs were predicated on a -ve North Atlantic Oscillation (NAO), mine included. Whilst neutral or -ve conditions were observed through a good part of the winter, they were no where near as negative as they needed to be in order to sustain prolonged cold.

This depends somewhat on your measure but I use the CDC (Sea Surface Temperature Anomaly) (SSTA) definition.

http://www.cdc.noaa.gov/Correlation/nao.data

http://www.cdc.noaa.gov/people/gary.bates/tele/nao.gif

Only during late February did we see prolonged -ve phase develop and sure enough it did what it says on the tin delivering a well below average end of February and start to March.

The direct cause of a lack of a prolonged -ve NAO during the core of the winter (January had a recorded value in excess of +1) was for me the SSTAs in the North Atlantic. Whilst many forecasts predicted the warm pooling to move northwards during December and January (thereby bring about the necessary conditions for a -ve NAO), it took its time and largely stayed put NE of Newfoundland:

http://weather.unisys.com/archive/sst/sst_anom-051218.gif

Finally when it did move north with the corresponding development of a cold SSTA in the sub-topical Atlantic, the jet finally displaced southwards and we were treated to a true Greenland High on the back of an easterly.

http://weather.unisys.com/archive/sst/sst_anom-060205.gif

http://weather.unisys.com/archive/sst/sst_anom-060219.gif

http://weather.unisys.com/archive/sst/sst_anom-060312.gif

This for me was clear evidence that given the right SSTA, a warm Atlantic can deliver a cold pattern.

The QBO and Pacific Jet

Make no mistake, the reason in my book why we did not get a severe winter is the QBO.

http://www.cdc.noaa.gov/Correlation/qbo.data

This very high altitude zonal wind is regarded by many metreologists as a key measure of the likely strength and positioning of the Pacific Jet. Throughout the key part of the winter, the QBO was in a deeply -ve (easterly) phase with record November and very high December values experienced.

This was highly predictable and my LRF did acknowledge this. However, I made the mistake of assuming that a strongly -ve QBO and -ve NAO were not mutually exclusive as there was some evidence from reanalysis charts and analogue years such as 1962/3 suggested that the two could occur together. I won't be making that mistake again. Basically a strong Pacific Jet (especially the -ve phase) prevents pressure from building over Greenland, in other words it works against the -ve NAO and as the Pacific is twice the size of the Atlantic, the odds were stacked against the NAO developing.

I also suspect that the strong Pacific Jet was a factor in preventing the SSTA in the Atlantic from moving as anticipated. It wasn't until the QBO relented in February that the Pacific North America pattern entered a -ve state which allowed the jet stream to pump storms over the Newfoundland area disrupting the sea surface and unshackling the warm anomaly and allowing the -ve NAO pattern to take over.

For next winter we are most unlikely to have a -ve QBO, rather a neutral or developing +ve (westerly) phase based on the evidence of the cycle.

Find of the winter must be the East Pacific Oscillation (EPO) and I must thank Steve Murr for pointing in the direction of EPO as I believe has been an excellent pointer this winter for the Pacific to relent and the North Atlantic to take over. All of our cold snaps more or less correlate to neutral / negative phases of the EPO.

http://www.cdc.noaa.gov/people/gary.bates/tele/epo.gif

The long range models

Hats off the UKMET for their seasonal forecast, and indeed some of the other long range outputs for correctly punting a cold but not excessively cold and dry winter. We should note however that the numerical models generally got the beginning (cold November/December) wrong and the (cold dry) end right. Just a note on the UKMET - their method used the NAO statistical inference rather than numerical models. The NAO was just within the forecasts margin for error whilst the original forecast actually resembled their numerical model output - I think they hedged their bets.

If next winter the numerical models and any other statistical forecast go for greater cold or warmth, we should make full use of them.

Whilst on the subject of modelling, the shorter range stuff has been pretty dire with dramatic changes occurring in the t72 range across all models. Clearly the models struggle with displaced jet flows where short wave errors can have dramatic impacts in the near time scale. I'm loathe to single out one model as being particularly poor, but the operational GFS was throughout the post Christmas period and it clearly doesn't handle blocking over Greenland at all well. The ECMWF whilst poor at times was for me the model of the winter, and it can put the award on its mantle piece next to the Summer award.

A post even larger teapot ?

Perhaps by far the intriguing aspect of the winter was the exceptionally warm pole.

I believe that this is a direct result of the last 25 or so years of forced anthropogenic warming, perhaps coinciding with a natural warming cycle. The planetary thermal balance is maintained through heat exchange to the poles where it is eventually lost to space. Lots of warming will eventually mean warm poles and I think we are beginning to see this trend emerging.

Warm air in the troposphere will warm the stratosphere at the tropopause. Continued warming will I think lead to a warmed lower stratosphere and upper troposphere which because of the degree of warming will be long lived. Warm air aloft at high latitude leads to above average geopotential height anomalies, in effect high latitude blocking. This is therefore likely to be manifested in a -ve Arctic Oscillation for winters to come, providing much of the key ingredients for cold to develop at mid latitudes, especially with a solar minima. The almost unprecedented warming should however make the use of analogues less meaningful however.

So as we leave this Winter and look forward to some welcome Summer warmth, we anticpate the QBO and Pacific as being less likely to interfer next time round,

the AO to be -ve and with even less incoming radiation, the prospects for the Winter of 2006/7 look at this stage to be even better. Much however can and will change but we look forward having achieved much and with so much more to come..

GP

Edited March 26, 2006 by Glacier Point

[John Cox]

Hi GP/ Ian/Steve Murray,

Great sysnopsis of your LRW GP.

I dont understand it all but do watch and appreciate all the effort you put in.

I will watch with interest all your(s) forecast for the coming winter

[summer blizzard]

Glacier Point, will you be releasing a spring/summer long range forecast?????????????

[Glacier Point]

Glacier Point, will you be releasing a spring/summer long range forecast?????????????

I haven't got the time for a thorough Spring forecast although with only two months left and a -ve NAO / neutral pacific signal 'in the bank' for until at least early May, I'd punt a below average Spring on this basis alone, similar to 1996.

As for the Summer, I'd like to give it a go time permitting as the Summer presents different forecasting challenges - you need to look south as well as north.

[summer blizzard]

Summer presents different forecasting challenges

Yes, i was looking into sea surface temperatures and there effect on telleconnection patterns and found that in winter there were 11 factors to consider but in summer there were 17 factors to consider.

[johnholmes]

what a superb post GP. Lots to ponder on in there.

many thanks

John

[acbrixton]

GP thanks for the objective and scholarly summary. Look forward to the summer and 2006-7 winter forecasts.

Regards

ACB

[The Enforcer]

As it happened, we never got the 'dream' set-up for the South where Lows bump into the cold air and spin off, but the point is that it could have happened.

I tend to think of it as a missed opportunity. Most seasonal winter for ten years and it blew it.

That allowed cold pooling to develop to our East in the 'normal' way, and as I said in my review, although there were frequent brief easterly spells, the coldest air never made it our way at the coldest time of the year.

This is a big hurdle. Winter 05-06 hasn't shown me that its possible to clear it.

Edited March 28, 2006 by The Enforcer