The Seasonal Forecast Thread

[BornFromTheVoid]

A quick look at May, using recent values and trends in the AO, NAO, PDO, AMO, MEI, Snow Cover, Solar Activity and the QBO.

 

The 8 criteria used to compare with recent years are

 

AO: Years with the 6 months from October to March averaging between 0 and 1.2, with moderate to high month to month variability.

NAO:Years with the 6 months from October to March averaging between 0 and 1, with moderate month to month variability

PDO: April and May average of greater than 0.5

AMO:Years with the 6 months from October to March averaging between -0.15 and 0.35

MEI: March to May average of between 0 and 1.5

Snow Cover: Negative Eurasian snow cover anomaly and Eurasian -ve anomaly larger than North American -ve anomaly (if NA anomaly is -ve)

Solar Activity: Years with an average monthly sun spot count between 30 and 90

QBO: Years with the 6 months from October to March averaging greater than 5 and greater than the April value

 

Below are the best matching years

 

Year: Matches

2012: 5

2007: 5

2004: 5

2002: 5

1997: 6

1995: 5

1993: 6

1991: 5

1984: 5

1983: 5

 

From the above years, the 5 matches added once and 6 matches added twice, the following charts were created using the NCEP/NCAR reanalysis data

 

 

500hPa GPH Anomaly .................. ...................  Precipitation .............. .............. Surface Temperature

 

 

So, a strong signal for a deep trough just to our south with some blocking about, particularly to our west and north west. This pattern suggests an increased chance of unsettled weather to towards the south and east, with things improving a little to the north west.

 

The precipitation chart indicates that the south will have above average rainfall, with close to average more likely elsewhere, which makes sense given the trough to the south.

 

Temperatures look likely to be close to average generally, but a greater chance of slightly below average temps in the east and south.

 

My CET estimate is 11.6C.

[BornFromTheVoid]

I've my summer forecast almost complete and will be posting it up in the next few days.

 

I think a pattern similar to the next week or 2 may be common during the first half of the season.

[summer blizzard]

Summer forecast. 

 

june: 13.5 to 15.3 (12, 09, 09, 04, 97, 95)

 

 

july: 15.5 to 16.1 (12, 09, 04)

 

 

august: 16.6 to 18.9 (12, 12, 09, 04, 03, 97)

 

Won't upload but shows a picture similar to this week with a trough to the south west and pressure north and east over the UK.

 

September: 14.2 to 14.3 (09, 09, 03)

 

 

...

 

In summary, an awful start but gets better.

 

Summer forecast. 

 

june: 13.5 to 15.3 (12, 09, 09, 04, 97, 95)

 

 

july: 15.5 to 16.1 (12, 09, 04)

 

 

august: 16.6 to 18.9 (12, 12, 09, 04, 03, 97)

 

Won't upload but shows a picture similar to this week with a trough to the south west and pressure north and east over the UK.

 

September: 14.2 to 14.3 (09, 09, 03)

 

 

...

 

In summary, an awful start but gets better.

 

[Alex]

Summer forecast. 

 

june: 13.5 to 15.3 (12, 09, 09, 04, 97, 95)

 

1.png

 

july: 15.5 to 16.1 (12, 09, 04)

 

2.png

 

august: 16.6 to 18.9 (12, 12, 09, 04, 03, 97)

 

Won't upload but shows a picture similar to this week with a trough to the south west and pressure north and east over the UK.

 

September: 14.2 to 14.3 (09, 09, 03)

 

4.png

 

...

 

In summary, an awful start but gets better.

 

Summer forecast. 

 

june: 13.5 to 15.3 (12, 09, 09, 04, 97, 95)

 

1.png

 

july: 15.5 to 16.1 (12, 09, 04)

 

2.png

 

august: 16.6 to 18.9 (12, 12, 09, 04, 03, 97)

 

Won't upload but shows a picture similar to this week with a trough to the south west and pressure north and east over the UK.

 

September: 14.2 to 14.3 (09, 09, 03)

 

4.png

 

...

 

In summary, an awful start but gets better.

How did you get the analogue years SB? 2009 and 2012 are already different as we now have a +PDO.

With the way things are going 1997 may not be a bad base though.

[summer blizzard]

How did you get the analogue years SB? 2009 and 2012 are already different as we now have a +PDO.With the way things are going 1997 may not be a bad base though.

 

I used MEI, QBO, PDO and GLAAM and rolled forward to the probable state during the summer. MEI and QBO were both good matches for 2009 and 2012, PDO got 2003 and 2004 and GLAAM got 1995 and 1997 (may have mixed up GLAAM and PDO).

[BornFromTheVoid]

Here's the summer forecast, using recent values, trends and some projections of different variables.

 

The variables and criteria used to find the most analogous years to this one are listed below

 

AO: Years with the 6 months from November to April averaging between 0.2 and 1.4, with moderate to high month to month variability.

(matching years, 1967, 1973, 1982, 1991, 1992, 1993, 1994, 1995, 1997, 2000, 2002, 2007, 2012)

 

NAO:Years with the 6 months from November to April averaging between 0.2 and 1.3, with low to moderate month to month variability

(1954, 1967, 1972, 1973, 1976, 1980, 1991, 1992, 2000, 2002, 2004, 2008, 2012)

 

PDO: January to May average of greater than 0.4

(1958, 1970, 1977, 1978, 1980, 1981, 1983, 1984, 1985, 1986, 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 2003, 2004, 2005, 2006, 2010)

 

AMO:Years with the 6 months from November to April averaging between -0.17 and +0.23

(1951, 1952, 1954, 1955, 1956, 1957, 1958, 1959, 1960, 1961, 1962, 1963, 1964, 1965, 1966, 1967, 1969, 1970, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1988, 1990, 1991, 1992, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013)

 

MEI: March to July average of between 0.1 and 1.5

(1953, 1957, 1958, 1959, 1965, 1966, 1969, 1972, 1977, 1979, 1980, 1981, 1982, 1986, 1990, 1991, 1993, 1994, 1995, 1997, 2002, 2003, 2004, 2005, 2009, 2010, 2012)

 

Snow Cover: Negative Eurasian snow cover anomaly, Eurasian -ve anomaly larger than North American -ve anomaly (if NA anomaly is -ve), and a -ve northern hemisphere anomaly.

(1968, 1990, 1991, 1992, 1993, 2007, 2008, 2012)

 

Solar Activity: Years with an average monthly sun spot count between 30 and 90

(1951, 1952, 1955, 1961, 1962, 1966, 1971, 1972, 1973, 1974, 1983, 1984, 1993, 1998, 2003, 2004, 2011, 2012, 2013)

 

QBO: Years with the 6 months from November to April averaging greater than 5 and greater than the April value

(1958, 1960, 1962, 1967, 1972, 1981, 1986, 1988, 2000, 2007, 2009)

 

So out of the 8 criteria, these were the best matching years

 

2012 with 6 matches

2004, 1993, 1992 and 1991 with 5 matches.

 

With those years, lets have a look at the summer composites and forecasts.

 

JUNE

 

It looks most likely that lower than normal pressure will dominate over the British Isles, stretching from Newfoundland into Scandinavia. This could lead to an increase in northerly orientated winds, bring some cooler weather to all areas, with an increase in precipitation also.

With a strong signal for lower pressure to our south west, and average pressure over Iberia, the opportunity for warm southerlies will still remain.

 

UK Precipitation: Chances of below, close to and above average values are 20%, 35%, 45%

UK Temperature:Chances of below, close to and above average values are 35%, 35%, 30%

 

 

JULY

 

 

A very similar pattern to June, but with some important differences. Lower pressure still looks most likely, but with higher pressure just to our south, the chances of a north/south split are increased. As it is though, an increased likelihood of northerly orientated winds and lower pressure will likely result in periods of below average temperatures and increased rainfall.

 

UK Precipitation: Chances of below, close to and above average values are 25%, 35%, 40%

UK Temperature:Chances of below, close to and above average values are 40%, 30%, 30%

 

 

AUGUST

 

 

August show another slight shift in pattern, with low to our west and higher pressure to the east. This opens the door for mild/warm southerlies, but also the potential for some very wet weather, especially further west. In this situation, eastern areas will likely do best for warmth and dry weather. Daytime warmth may well be dictated by breaks from the cloud the influence of higher pressure over the continent pushing west. Where rain and cloud remain, temperature may remain suppressed, especially during the day.

 

UK Precipitation: Chances of below, close to and above average values are 20%, 30%, 50% (wettest further west)

UK Temperature:Chances of below, close to and above average values are 33.3%, 33.3%, 33.3% (coolest further west)

 

 

OVERALL

 

Unfortunately, this method of forecasting shows a wet summer is most likely, with average or slightly below average temperatures favoured. August shows the most potential for warmth, but also for some very heavy precip totals.

 

I'll update this once each month, as the latest data becomes available. Any suggestions, constructive criticisms and/or error spotting is welcomed!

[Zenarcher]

My June forecast can be found here http://forum.netweather.tv/blog/227/entry-4758-june-2014-forecast/

[Roger J Smith]

My summer outlook remains about the same as in my preliminary forecast ...

 

JUNE likely to be a rather cloudy, wet month (130-160% normal rainfalls for most of Britain and Ireland) trending to near normal rain in Scotland and temperatures that resemble the May regime, a bit above normal but mainly because of cloud cover at night. CET around 14.8 C. Could see one significant heat wave near end of June.

 

JULY expected to bring near normal temperatures and rainfall to most regions, possibly a bit on the cloudy side of normal, but improving from first to second half. It may become hot at times in late July. CET around 16.5.

 

AUGUST (and SEPT) expected to be generally warm and dry with significant hot (and humid) spells but more so than in 2013 the heat may lead to widespread severe thunderstorms so that "dry" may verify on a large scale statistical basis but some locations might easily see 50-100 per cent extra rainfall. Of course it would be difficult to pinpoint where these heavier storms might hit but in the circulation pattern I am foreseeing, would speculate inland south, east-central Midlands, south Yorkshire and inland East Anglia. Some places may miss the storms and come in quite dry. CET around 18.2, so a warmer August than we've seen for a while, and September around 15.0.

 

General consensus is for a weak North Atlantic hurricane season, due to the developing El Nino. I am going to be a bit contrarian and say more like a normal season with 13/8/2 the final count.

 

See you in September at the post-mortem. Whatever comes, enjoy your summer.

[johnholmes]

thanks Roger, as you say, wait until September before making any judgements

 

and not all that different to the one produced by BFTV?

[Don]

My summer outlook remains about the same as in my preliminary forecast ...

 

JUNE likely to be a rather cloudy, wet month (130-160% normal rainfalls for most of Britain and Ireland) trending to near normal rain in Scotland and temperatures that resemble the May regime, a bit above normal but mainly because of cloud cover at night. CET around 14.8 C. Could see one significant heat wave near end of June.

 

JULY expected to bring near normal temperatures and rainfall to most regions, possibly a bit on the cloudy side of normal, but improving from first to second half. It may become hot at times in late July. CET around 16.5.

 

AUGUST (and SEPT) expected to be generally warm and dry with significant hot (and humid) spells but more so than in 2013 the heat may lead to widespread severe thunderstorms so that "dry" may verify on a large scale statistical basis but some locations might easily see 50-100 per cent extra rainfall. Of course it would be difficult to pinpoint where these heavier storms might hit but in the circulation pattern I am foreseeing, would speculate inland south, east-central Midlands, south Yorkshire and inland East Anglia. Some places may miss the storms and come in quite dry. CET around 18.2, so a warmer August than we've seen for a while, and September around 15.0.

 

General consensus is for a weak North Atlantic hurricane season, due to the developing El Nino. I am going to be a bit contrarian and say more like a normal season with 13/8/2 the final count.

 

See you in September at the post-mortem. Whatever comes, enjoy your summer.

 

 

Thanks Roger, the only part of the forecast I'm not so keen on is the later part for September.  Sounds typical of many early Autumns of the late 90's through to the mid 00's.  You know what I'm getting at!  Anyway, that's all a long way off, so lets concentrate on Summer for now.

[Supercell 89]

Was going to post this the other day but been busy with revision for my exam and popping out again now so will make it quick but here's my final summer thoughts;

 

I haven't changed my view since April and the factors i was looking for this summer seem to be slowly coming together. We've seen a continuation and strengthening of the positive PDO the last month as well as a shift towards weak El Nino conditions in the pacific and also we are in the midst of transiting towards the -QBO phase.

 

I can't seem to get the links to work but when matching the composites for this summer the common theme that kept popping up with a -QBO and +PDO pattern is a trough in the mid-atlantic and high pressure towards scandinavia, very much like we've had this month and i can see this continuing but i think the high pressure will become more influential as summer wears on.

 

Summary: Very warm summer with rainfalls totals generally around average. Wetter early summer, drier late summer. 

 

June:  Very Warm. More changeable first half of the month with some cooler and unsettled periods alternating with brief warm/very warm periods, with the risk of some thundery episodes. Moving into the second half of June things gradually turning more warmer and drier as high pressure ridges in and becoming largely settled for the remainder of the month with the risk of it becoming quite hot. 

 

CET: 16.0c - A near average first half but i think the second half of June could see some very persistent warmth so sticking my neck out a bit with this one. 

 

July: I'm not quite sure how this month will pan out. 

 

Warm but Changeable. Very warm early with a slow breakdown of June's settled spell. Remaining warm and changeable during the middle part of the month before turning drier late in the month. Breakdowns likely to come in the from the south not the west, with the risk again of some thundery episodes.

 

CET: 17.6c

 

August: Very Warm & Dry, especially for the South-East. 

 

August along with late June i think will be when we see summer peak. High pressure building over the UK and to our north east. Frequent south-easterly winds but very dry especially for the South-East. More unsettled at times further west with more near average rainfall totals. 

 

CET: 18.4c

 

Overall I think we may well have the warmest summer since 2003 and could even challenge 2003 for fourth place if i was to be so bold, providing the PDO stays strongly positive. One thing I think could be of interest this summer is the heat intensity at times and humidity. With low pressure in the mid Atlantic and high pressure to our east there is a chance for some very hot plume events this summer along with some thundery spells.

[Isolated Frost]

Lazy Sunday afternoon's, ey?

 

With July looking to move slightly positive, I'm going to see whether, using more concise use of the AO index, I can match anything up; this time around.

[BLAST FROM THE PAST]

Getting my winter head on even this early  sorry I know there's autumn first   .  Early pointers I'm looking at ENSO neutral not Nino, if nino then weak at best as its just not taking off], -ve QBO, Jetstream south and very meridional, sun in continued slumber.  Very interesting early signs.

 

 

BFTP

[Lettucing Gutted]

That's music to my ears BFTP  

Edited August 24, 2014 by Craig Evans

[whiskers]

Yay,I also have my winter head on early,must be this unseasonal cold evenings,soo excited it just feels right this year,well can't be worse than last year! And so it begins...!

[Severe Siberian icy blast]

Yea I have to admit given that August has over the recent years been a wash out , it's normally around the time when I start looking for the first signals . As BFTP says , a weak El Niño , and an easterly QBO , already gives us a better start to last year , even my wife this year is looking forward to winter , we were only talking about this last night . If we can see the sun start to really quieten off , then that would help I feel , and during sept but more particularly October see the SSI (Siberian snow index) take off then that would really help to lock Europe in the freezer. Another 4 wks or so then we can really look in more depth .

[stewfox]

JUNE

 

 

It looks most likely that lower than normal pressure will dominate over the British Isles, stretching from Newfoundland into Scandinavia. This could lead to an increase in northerly orientated winds, bring some cooler weather to all areas, with an increase in precipitation also.

With a strong signal for lower pressure to our south west, and average pressure over Iberia, the opportunity for warm southerlies will still remain.

 

UK Precipitation: Chances of below, close to and above average values are 20%, 35%, 45%

UK Temperature:Chances of below, close to and above average values are 35%, 35%, 30%

 

JULY

 

A very similar pattern to June, but with some important differences. Lower pressure still looks most likely, but with higher pressure just to our south, the chances of a north/south split are increased. As it is though, an increased likelihood of northerly orientated winds and lower pressure will likely result in periods of below average temperatures and increased rainfall.

 

UK Precipitation: Chances of below, close to and above average values are 25%, 35%, 40%

UK Temperature:Chances of below, close to and above average values are 40%, 30%, 30%

 

AUGUST

 

August show another slight shift in pattern, with low to our west and higher pressure to the east. This opens the door for mild/warm southerlies, but also the potential for some very wet weather, especially further west. In this situation, eastern areas will likely do best for warmth and dry weather. Daytime warmth may well be dictated by breaks from the cloud the influence of higher pressure over the continent pushing west. Where rain and cloud remain, temperature may remain suppressed, especially during the day.

 

UK Precipitation: Chances of below, close to and above average values are 20%, 30%, 50% (wettest further west)

UK Temperature:Chances of below, close to and above average values are 33.3%, 33.3%, 33.3% (coolest further west)

 

 

OVERALL

 

Unfortunately, this method of forecasting shows a wet summer is most likely, with average or slightly below average temperatures favoured. August shows the most potential for warmth, but also for some very heavy precip totals.

 

I'll update this once each month, as the latest data becomes available. Any suggestions, constructive criticisms and/or error spotting is welcomed!

 

 

Interesting forecast how do you think you did ?

 

Wasn't as wet and the northerly winds didn't really show in June/July but came along a bit later.

 

Fairly good over all

Edited August 27, 2014 by stewfox

[EML Network]

Interesting forecast how do you think you did ?

 

Wasn't as wet and the northerly winds didn't really show in June/July but came along a bit later.

 

Fairly good over all

 

I think due to the fact you have highlited the areas where BFTP was wrong about this summer that you have already made your mind up about his summer thoughts. 

In fairness my summer forecasts are always wrong, but my winter forecasts have been absolutely spot on every year now for the past 3 years in a row. 

 

I wont bother putting out a summer forecast next year, I care not what happens in summer, it has to be endured as far as im concerned. 

 

So don't judge BFTP's winter forecast or thoughts by his summer one. 

And just for the record, my own winter thoughts ??...I'd say there's much more chance of it being closer to average than last Winter.

[BLAST FROM THE PAST]

Hi EML, its BFTV who provided summer forecast not me :-)

 

A little very early taster for folks on my idea ahead.  I've mentioned QBO and solar slumber.  Jetstream more south and meridional.  I think there's a connection with North Pacific SSTs and will give more detail when I do my LRF but if correct this winter will be quite interesting....so at the moment jetsream to be generally on NW/SE tilt, increasing chances of arctic incursions but also in turn more direct hits from Atlantic storms.  Cold and snowy early, stormy mixed bag middle, a pronounced and prolonged late cold spell....Spring to be delayed.  I'm mentioning it now as recent research I've done showed similar outcomes in past analogues...but situation was quite unique so not many analogues to go on.

 

regards

 

BFTP

[Frank Trough]

I think due to the fact you have highlited the areas where BFTP was wrong about this summer that you have already made your mind up about his summer thoughts. 

In fairness my summer forecasts are always wrong, but my winter forecasts have been absolutely spot on every year now for the past 3 years in a row. 

 

I wont bother putting out a summer forecast next year, I care not what happens in summer, it has to be endured as far as im concerned. 

 

So don't judge BFTP's winter forecast or thoughts by his summer one. 

And just for the record, my own winter thoughts ??...I'd say there's much more chance of it being closer to average than last Winter.

 

I would have thought that is almost a statistical certainty isn't it? I'd be amazed if it was milder and wetter than last winter. 

[Roger J Smith]

Just before I get into any forecasting reviews or views, one comment on the EML review above, the reference to "BFTP" should be "BFTV" as it is Born From The Void whose forecast is being reviewed there, I think.

 

In my own case, August turned a lot cooler than expected around the 10th or so, and that part of the forecast was definitely a bust. I think that conditions before that were fairly close to what was foreseen, the overall result therefore was mixed. I'm looking over these results to see what can be learned but too early to say anything there yet.

 

From research and just the subjective feel of things at present, would say that the autumn looks likely to be generally settled and a bit warmer than average at least. Even so, one or two windy spells could develop as the storm track looks set to run just north of Ireland and Scotland on average. This could lead to November being like last year with some brief mild spells and significant cold spells that dominate the pattern.

 

As to the winter 2014-15, have not done much work on it, the research model output looks rather variable but near long-term averages overall. Will be turning my attention to that in the next few weeks.

[Timmytour]

Based on my highly amateur statistical analysis of the past 315 years, I'm going for an autumn/winter of mixed but mainly wet mild and windy weather with occasional brief cold interludes..nothing out of the ordinary, until we approach the last few days of January which will see it trend colder and lead into a cold February with some falls of snow in favoured areas (not widespread). Only in the last few days of February will the first shoots of Spring start to appear

Edited October 6, 2014 by Timmytour

[Roger J Smith]

These are preliminary ideas for my winter forecast, will have a final and more detailed outlook around Wed 22nd.

As always, this is entirely based on my own research and while I take note of other approaches, I assume that they will be at least partly incorporated into my methodology which uses the index values of past data considered to have predictive value for this season. In other words, I would expect these other approaches to be buried in that data analysis rather than something different from my methods.

The overview would be highly variable trends that include some very cold weather at times as well as some very mild weather at other times. The most likely times for the very cold weather appear to be mid-November, early December, mid-January and late February into early March. The very mild conditions would occur between those periods, notably Christmas to New Years as well as late January into early February.

With that much variability in the forecast, timing cannot be considered overly reliable. I am just relaying to you what my raw data show, and if the train of high-amplitude ridges and troughs is even a little off in timing, the schedule could shift.

This sort of pattern is more likely to induce northerly than easterly cold spells. This may actually favour some parts of Britain (and Ireland) to see snowfall, notably northern and higher elevations of Scotland and northwest England, Wales, southwest England, and in Ireland, Connacht and west Ulster as well as west Munster, but there is probably enough variability to suggest brief spells of northeast winds favouring eastern and central England as well as eastern Ireland for snow.

The overall trend here is for spells of quite contrasting weather so that if snow does materialize, it would probably not persist on the ground for more than a week before melting away in milder weather.

I don't foresee long spells of stormy weather with a parade of deep lows as we saw last winter, but there could be one or two notably stormy spells involved in this rapidly changing scenario. It appears likely to me that there could be one or two weeks during the winter with a fast westerly type of flow bringing intense windstorms with SW to W gales, and one or two outbreaks of strong northerly flow that might induce strong gusts from NW to N associated with "polar low" type circulations.

At the same time, there could also be one or two weeks of very placid weather under high pressure of Atlantic origins similar to what happened early in Jan 2012.

That's the mixture that I foresee and within that I would think there might be two, three or possibly four interesting wintry periods for Britain and Ireland with about equal chances of them falling in any of the next five months. I don't think there's much chance of a cold-dominated sort of winter like 2009-10 but I would say there's more chance of that than a mild-dominated winter such as 2006-07. The variable signal appears strong in the preferred analogue set which includes 1968-69 and a much older case, 1866-67 which established a high-water mark for variability of temperature trends.

With this much variability expected, I am more concerned that this aspect would verify than precise timing, in other words, a difficult forecast in my estimation and therefore counting on the variability to be the main "performance" criterion.

Will update this in somewhat more expanded form next week.

[BLAST FROM THE PAST]

Hi Roger

Quite detailed and I for one see the variability ahead hence the basic cold early and cold return late theme call overall...I think in between 'generally mild and active middle' BUT not exclusively so .....no real 'domination'. The Jetstream is very 'meridional' in nature and it is/will be very difficult to pin down.....but the theme I like/ like is wrong as more hoped/pleased is appropriate. I Look forward to your final thoughts

Glad you see a late Feb into march cold idea.....

BFTP

Edited October 16, 2014 by BLAST FROM THE PAST

[Roger J Smith]

Detailed version -- highly variable winter pattern expected

 

 

As promised, here are some more detailed predictions based on my research. I have tried to assess all the information offered in various other sources that I find credible, and to some extent I note a general overlap of conclusions made from different approaches, which inspires a bit of confidence. At the same time, I feel subjectively that almost anything could happen this winter as things seem to be in somewhat of a fine balance between a mild zonal set-up and the onset of high-variability stationary if not necessarily retrograde type blocking patterns.

 

There is bound to be some similarity to 2013-14 around the hemisphere if only because some of the large-scale drivers have not changed all that much, and early indications suggest that the North Atlantic may persist in being active. Very cold air seems poised to invade North America about where it did last winter, and Siberian blocking is primed by early snow cover and the position of ridge and trough features over the northwest Pacific sector.

 

So I should begin by saying that winter 2014-15 may not seem entirely different from last winter to many, and there could be rather frequent wind storm events in Britain and Ireland. What's different is perhaps that they won't come almost non-stop after a certain point (last winter it was 26 Dec IIRC) but in occasional bursts separated by blocking sequences and less stormy northerly flow (although active enough).

 

This set-up should mean that winter 2014-15 will not be generally as mild as last winter in Britain and Ireland, but on average around the long-term mean with approximately equal mixture of cold and mild spells. And the difference between them may be quite large, giving rise to a forecast of notable variability, a statistic that can be measured and compared to other winters. History buffs may recall the complete turnaround from late Dec 1986 into mid Jan 1987, or the contrast between 23-29 Jan and 30 Jan-5 Feb in 1969. That sort of high variability could be on tap this winter.

 

The colder portions of the winter, from my index value research, would appear to be roughly once every month, but more specifically, mid-November, early December, early part of mid-January and possibly a longer cold spell near end of February into March -- these are favoured to be the cold spells and any one of them could generate a snowfall event or two. That snowfall is not likely to hang around very long in a highly variable regime, which may introduce snowmelt flooding into the mix of possible events.

 

The milder spells which you can gather from the above timing will be at various points in early and late November, late December, second half of January and possibly first half of February, may contain some windy and stormy outbreaks, but some (the late Dec and late Jan portions) may involve southerly flow around blocking highs to the east and southeast, and those periods could be quite inactive.

 

What we have in total is a menu of almost all possible winter weather types that I believe will mount up a campaign of noticeable variety giving the impression of a winter with no dominant theme or as people might say, "it just can't make up its mind" but if the late cold is a strong easterly outbreak (the earlier ones are more likely to be northerlies) then it may become the biggest theme of the season, at least as broadly defined, many believe that March is a spring month of course (despite 2013).

 

Everyone always wants to know about the Christmas-New Years period in particular, and there I would say that the chances are fairly good that there might be a little active stormy weather just before Christmas, not particularly cold, followed by mildish settled weather and ending up stormy again near New Years with the risk of it turning a lot colder soon afterwards.

 

Some heavy snowfalls could develop in November and early December in regions that are exposed to northerly flows off the Atlantic Ocean, Irish Sea or North Sea. There may also be top up snowfalls in brief northeasterly flows then. That part of the winter, depending on how severe it is, may give rise to talk about "here comes a really brutal winter" but keep in mind that the pattern should be variable enough to melt that snow and end the dominance of the cold air masses for the time being.

 

A particularly interesting part of the winter is likely to come around 4-6 January, which is about when I would expect the most severe storms of the winter. These might be mostly wind and rain at first but could end up with heavy snow.

 

For North America, I am expecting a similar wild ride with high variability. Some exceptionally mild weather is likely given the state of the Pacific (a raging hothouse at the moment, the current monthly anomaly value at Seattle WA is +3.4 C and this has been the case all through spring, summer and autumn 2014). The arctic is looking active enough too, for this early stage of the developing winter season, so I expect continual battles for domination of the eastern and central regions between much above and much below normal air masses. This often leads to one or two massive east coast storms when deeper troughs become available to harness the potential energy in such a situation (and really this is almost the default climate anyway). The western Atlantic may be under intermittent ridge and even cut off blocking high regimes, but these may be either too weak or too distant from Britain and Ireland to allow for a dominant cyclonic pattern further east, there may be a mean shallow trough partially linked to cut off low pressure near the Azores. This will just contribute to the general variability as a pattern like that can alternatively pump in mild air and storms, or collapse to allow for northerly outbreaks.

 

Eastern Asia may have another of their increasingly frequent (in recent years) severe winters with heavy snowfall. That may in fact become the main story of the winter globally.

 

In such a variable pattern, I am rather reluctant to put too much emphasis on CET values but for later testing, here's what I would expect: NOV 5.0, DEC 4.4, JAN 4.5, FEB 3.3, MAR 4.5. It can be seen there that March is the coldest month relative to normal and February the coldest in absolute terms. Some 30-day period in later Feb and early March could average as low as 2.5. Some other 30-day period in midwinter could be as mild as 6.0. I would expect precip to be generally above normal in the range of 125-150 per cent of normal values with little variation regionally as different regimes produce different outcomes. Everyone will get their share of the surplus rain and snow. And at least one windstorm event is likely to qualify as exceptionally severe.