Winter 2010/2011 Part 3

[Thundery wintry showers]

This winter shouldn't come as that large a surprise, there is no physical reason why we cannot have an exceptionally cold snowy December followed by exceptionally snowless weather for the rest of the winter and/or a notably warm February. It requires a dramatic synoptic shift but in view of the strong La Nina there was always a strong likelihood of this.

[AderynCoch]

From a stats geek point of view, it's very disappointing to not get another sub-3C winter after such a cold start.

On the other hand, I suppose one might say that we're lucky to get a sub-zero month in a winter above 3C.

[Weather-history]

From a stats geek point of view, it's very disappointing to not get another sub-3C winter after such a cold start.

On the other hand, I suppose one might say that we're lucky to get a sub-zero month in a winter above 3C.

We did have a November to January period that was sub 3C (2.7C) and is the 2nd coldest such period in over 100 years, the other was 1962-63. So it was very unusual.

Also interestingly, the winter just gone was colder than any winter of the 1960s except 1962-63. The last two winters (2009-10 and 2010-2011) both surpass the winters of the 1960s with the exception of 1962-63

[greybing]

Manchester Winter Indices

1978-79: 262

2009-10: 197

1985-86: 159

1981-82: 149

1976-77: 141

1984-85: 140

1995-96: 135

1990-91: 126

2010-11: 119

2008-09: 105

1986-87: 100

1977-78: 90

1980-81: 90

1982-83: 85

1983-84: 82

1993-94: 78

2000-01: 77

1996-97: 72

1979-80: 66

2005-06: 59

2001-02: 50

2003-04: 50

1998-99: 47

2004-05: 47

1994-95: 45

2002-03: 44

1992-93: 43

1999-00: 42

1975-76: 41

1991-92: 40

1987-88: 37

2007-08: 37

1973-74: 30

1974-75: 26

1989-90: 26

2006-07: 21

1988-89: 20

I am sure you have explained this before but could you please for my sake explain how these indices are worked out,thankyou.

[Weather-history]

I am sure you have explained this before but could you please for my sake explain how these indices are worked out,thankyou.

10 x [(number of days with lying snow at 9am)+(number of days with falling sleet/snow) + (number of occasions temperatures were at or below zero)] divided by the mean winter maximum temperature.

[AderynCoch]

We did have a November to January period that was sub 3C (2.7C) and is the 2nd coldest such period in over 100 years, the other was 1962-63. So it was very unusual.

That's certainly an impressive achievement, and it's quite notable that November was 1.2C colder than February: the last time this happened was 1965-66, when the gap was also 1.2C (Nov=4.5C, Feb=5.7C), and I believe you have to go back to 1925-26 to find the last time the gap was larger (November at 3.6C being a whopping 3.2C colder than the 6.8C February that followed). The last time February was warmer than the preceding November at all was 1996-97 (Nov=5.9C, Feb=6.7C).

Shift Nov/Dec/Jan forward to Dec/Jan/Feb and you have a much more classical cold winter quarter, though the 3.7C would probably have to be a bit lower (say 2-3C maximum). It truly has been an early winter.

[Optimus Prime]

A CET of 6.4c for February isn't all that exceptional really, only 28th warmest on record. A pretty much carbon copy of 1985/1986 really but December and February in the wrong order.

[North-Easterly Blast]

We did have a November to January period that was sub 3C (2.7C) and is the 2nd coldest such period in over 100 years, the other was 1962-63. So it was very unusual.

Also interestingly, the winter just gone was colder than any winter of the 1960s except 1962-63. The last two winters (2009-10 and 2010-2011) both surpass the winters of the 1960s with the exception of 1962-63

The winter CET is not always a clear picture of what the winter was like, unless it is very cold (ie sub 2*C), or very mild (5.5 - 6C or more) Winter 1986-87 is an example of a winter having a notable cold spell whereby the rest of the winter was not special. Take out of the equation the two week period January 7th to 20th, and the winter of 1986-87 would have had a CET of 4.6, not the 3.5 that it ended up, so in other words that winter was basically average overall with a two week notable cold spell, and the winter was by no means cold overall.

The winter CET of 2010-11 is another example that doesen't give a clear picture of what the winter was like, and on the face of the CET alone it doesen't describe how pear shaped a winter it was. This winter just ended is not an example of a winter that is cold overall, it is plainly an example of a winter that started with an exceptional cold spell that deteriorated into nothing by the turn of Xmas, and then the rest of the winter was certainly nothing special and February was very mild. Take out of the equation the period 1st - 27th December, and winter 2010-11 has a CET of 5.0, not the 3.1 that it ended up, so excluding the pre Xmas period, winter 2010-11 was more typical of the modern 1990s / 2000s type winter, and a large part of winter 2010-11 was still milder than many winters in the 1960s.

Looking at the 1960s, winter 1968-69 had a similar CET to 2010-11, although the cold spells were more spread through the winter and it was only for most of January that it was largely mild, either side of this there were good cold spells, so I would call winter 1968-69 as relatively cold overall. It certainly wasn't pear shaped like 2010-11.

I know that the severe spell in Jan 1987 has led many forum users to looking at the 1986-87 winter through rose coloured spectacles, largely as that spell is remembered by many but many forget what the rest of that winter was like, and often wrongly remember that winter for being severe overall. My question now is, will the Dec 2010 severe spell in years to come lead many into looking through rose coloured spectacles at winter 2010-11, or will it be more remembered rightly as the winter that started off severe but quickly deteriorated into nothing once Xmas arrived?

[North-Easterly Blast]

This winter shouldn't come as that large a surprise, there is no physical reason why we cannot have an exceptionally cold snowy December followed by exceptionally snowless weather for the rest of the winter and/or a notably warm February. It requires a dramatic synoptic shift but in view of the strong La Nina there was always a strong likelihood of this.

Although apart from Dec 1950 which had a moderate La Nina, all other Decembers in moderate to strong La Nina winters up to this winter have not been anything other than average to mild, and not much different to the following Jan / Feb, so you certainly cannot say that there was ever any likelihood of the severe December that we had. Look here:

Dec 07 4.9, Dec 99 5.0, Dec 98 5.5, Dec 88 7.5, Dec 75 5.3, Dec 73 4.9, Dec 70 4.3, Dec 55 5.4, Dec 49 5.8; so of all the La Ninas below -1*C there was not one December that could be described as cool let alone cold.

To get such an extreme pre Xmas period like 2010 only to disappear completely over Xmas never to return certainly makes history as a pear shaped winter, which seems just as extreme in the pear shaped winter category as an overall severe winter like 1962-63, 1684 etc.

Certainly winter 2010-11 has for a large part been disappointing for most, and it was over far too soon before Christmas was even out of the way, and it was back to the typical modern 1990s / 2000s winter after Xmas. I would certainly prefer something like 2009-10 or 1995-96 any day. Even winter 2008-09 was better than this year, not especially cold but at least the cold was more spread through the winter and there was some decent cold and snow up to mid-Feb. I certainly wouldn't want a repeat of 2010-11, I would much prefer something more spread out even if not especially cold a la 2008-09. Certainly if I had to choose winters in order of preference since 1988 then 1990-91, 1995-96, 2008-09 and 2009-10 would be far more a first choice than 2010-11.

A CET of 6.4c for February isn't all that exceptional really, only 28th warmest on record. A pretty much carbon copy of 1985/1986 really but December and February in the wrong order.

December 1985 may have been a mild month but the mild spell ended on Dec 25th / 26th and it turned very cold. It was then cold for two weeks with some snow in early January, then there was then a mild spell until the 23rd, when it turned cold again, which became the feature of February. Certainly once you had got to Xmas in 1985 then the rest of the winter was by and large cold. On top of this, Nov 1985 was also a cold month too, so excluding the first three weeks of Dec 1985, which was the only mild spell of note between October and in fact, after April 1986, the whole extended winter of 1985-86 was a pretty classical cold season overall.

[stewfox]

The winter CET of 2010-11 is another example that doesen't give a clear picture of what the winter was like, and on the face of the CET alone it doesen't describe how pear shaped a winter it was. This winter just ended is not an example of a winter that is cold overall, it is plainly an example of a winter that started with an exceptional cold spell that deteriorated into nothing by the turn of Xmas, and then the rest of the winter was certainly nothing special and February was very mild. Take out of the equation the period 1st - 27th December, and winter 2010-11 has a CET of 5.0, not the 3.1 that it ended up, so excluding the pre Xmas period, winter 2010-11 was more typical of the modern 1990s / 2000s type winter, and a large part of winter 2010-11 was still milder than many winters in the 1960s.

Yes take out 27 days of December , given Jan CET was below average take that out as well, forget November and March potential and the winter was disappointing

Did I have a foot of snow and max -4c or -5c on christmas day or boxing day in the typical winters of the 1990s. No I had sleet mid March under a lamp post at 4am. How soon we forget.

If we take 40 days out of most winters (coldest days) it will make winters milder.

You cannot compare 2010-11 with the 1990s or pre 2008 not IMBY anyway

Edited March 1, 2011 by stewfox

[Kentish Kiwi]

Yes take out 27 days of December , given Jan CET was below average take that out as well, forget November and March potential and the winter was disappointing

Did I have a foot of snow and max -4c or -5c on christmas day or boxing day in the typical winters of the 1990s. No I had sleet mid March under a lamp post at 4am. How soon we forget.

If we take 40 days out of most winters (coldest days) it will make winters milder.

You cannot compare 2010-11 with the 1990s or pre 2008 not IMBY anyway

Absolutely agree with you there, was thinking the exact same thing. It seems to me as though North-Easterly Blast has developed sone sort of personal vendetta or grudge against the winter of 2010/11 and has gone out of his way to portray it in a negative light (probably without even realising it). Though I do agree with him to an extent in regards to the 'pear-shapedness' of the winter.

Personally this winter has been FAR from a 'disappointment' and will certainly be looked back on fondly, it definitely doesn't compare with the mild winters experienced between 1988-2007.

I get the feeling that there would be far less complaining, negativity and dissapointment in regards to the winter as a whole if the months had been flipped and we saw a classically mild December and a below average yet largely snow-free January, followed by a severe and very snowy sub-zero February (even though it would be statistically less significant than the November/December spell), simply because of the physiological effect of the cold and snow being fresh in the memory and 'saving' what many would probably be labelling a potentially disastrous winter. This even though such severe and persistent cold and snow is much harder to achieve so early in the season than in February. I personally would prefer a spell of severe wintry weather in December than a comparable one in February - less solar influence and therefore less day-time thawing, with sharper overnight (and day) frosts as a result. Plus the added bonus of warmer SSTs provideing more instability and therefore convection for easterlies, just as we experienced.

Anyway, just an alternative way, to that which NEB has been repeatedly championing, of looking at the unarguably memorable winter we have just experienced.

[Weather-history]

Interestingly, if you take out the last 7 days of February and replace them with the last 7 days of November ie 24th November-22nd February instead of 1st December-28th February, the CET for that period I come up is about 2.5C

The coldest 90 day period seldom coincides with the meteorological winter (also a 90 day period)

Winter 2009-10 had a CET of 2.4C but 11th December-10th March had a CET of 2.0C

For winter 2010-2011 had a CET of 3.1 but 24th November-21st February CET had a CET of 2.5C

Maybe worth comparing that period with past such periods.

Lets face, we were overdue a significantly milder than average winter month, I don't think anyone just 4 years would believe anyone would be making such a comment.

Edited March 2, 2011 by Mr_Data

[North-Easterly Blast]

Interestingly, if you take out the last 7 days of February and replace them with the last 7 days of November ie 24th November-22nd February instead of 1st December-28th February, the CET for that period I come up is about 2.5C

The coldest 90 day period seldom coincides with the meteorological winter (also a 90 day period)

Winter 2009-10 had a CET of 2.4C but 11th December-10th March had a CET of 2.0C

For winter 2010-2011 had a CET of 3.1 but 24th November-21st February CET had a CET of 2.5C

Maybe worth comparing that period with past such periods.

Lets face, we were overdue a significantly milder than average winter month, I don't think anyone just 4 years would believe anyone would be making such a comment.

Yes very true, there have not been many runs of eight where no Dec, Jan, or Feb recorded a CET of 4.2 or greater. I believe the last such occasion was back in the late 1800s.

Although no-one can deny that winter 2010-11, rather than being a classic cold winter overall, it was a case of an exceptional early freeze up deteriorating into nothing over Xmas and the rest of the winter was then certainly nothing special and February was very mild - it certainly wasn't anything like 1995-96 for example which had cold spells spread through the season. 2009-10 still had cold spells spread from 11th Dec to mid March. 2008-09 still had cold spells spread from late Nov to mid Feb. I would certainly like a winter that has cold spells spread through the winter and not concentrated at one end and then next to nothing for the most part of it like this year.

[greybing]

10 x [(number of days with lying snow at 9am)+(number of days with falling sleet/snow) + (number of occasions temperatures were at or below zero)] divided by the mean winter maximum temperature.

thankyou

[Summer of 95]

The only thing about that winter index is that I feel by giving such weight to days of *falling* snow, it over-rates winters that were full of marginal events where snow fell (often as sleet) but never stuck, or stuck only for short periods. I'd actually say that January 2011, with one day of snow falling snowcover, over a dozen air frosts and lots of crisp, cold weather was a more wintry month than February 2010 when it was just dull and sleety all the time, snow or sleet fell on ten days that month but only 2 had snow lying- and one of those was snow left over from Jan 31st.

1998/99 and 1999/00 score surprisingly high to me; the January and February (98-9) and December (99-0) were full of marginal snow events where hardly anything settled at low levels; for lying snow these two were far worse than 2006-7 where although there was only one major snow event, it brought a decent covering to a wide area. I don't remember a frosty spell like that just before Christmas 2006 in either of those two winters either.

[Weather-history]

The only thing about that winter index is that I feel by giving such weight to days of *falling* snow, it over-rates winters that were full of marginal events where snow fell (often as sleet) but never stuck, or stuck only for short periods. I'd actually say that January 2011, with one day of snow falling snowcover, over a dozen air frosts and lots of crisp, cold weather was a more wintry month than February 2010 when it was just dull and sleety all the time, snow or sleet fell on ten days that month but only 2 had snow lying- and one of those was snow left over from Jan 31st.

1998/99 and 1999/00 score surprisingly high to me; the January and February (98-9) and December (99-0) were full of marginal snow events where hardly anything settled at low levels; for lying snow these two were far worse than 2006-7 where although there was only one major snow event, it brought a decent covering to a wide area. I don't remember a frosty spell like that just before Christmas 2006 in either of those two winters either.

I point out the winter index is a local one and not a national one. You are trying to apply what happened in your locality with what happened in my locality. You can't really do that and here's why. For instance, 2006-07 snow event didn't really effect my area. The snow didn't begin until about 8am and we didn't have a covering. It was nothing compared to further south. Compared to what happened in London etc, it was a non-event.

You mentioned pre-Christmas 2006 frosty spell, only recorded 3 frosts in the entire month. At the moment,its more frosty outside now -4.8C currently then it was at any time during that month. It got down to -8C during December 1999 and -6C during December 1998.

Also saw two days of lying snow during that winter of 1998-99.

It maybe worth using that index for your own data. I remember a few years ago, on another site some member from the SE commenting that they thought winter 2002-03 was a better winter than 2003-04 was and I thought the other way around, so I applied the index to his location and lo and behold it turned out that the index confirmed his point as 2002-03 had a higher value then 2003-04, whilst for me, 2003-04 had the higher value.

Its not full proof but I find it is adequate.

Edited March 3, 2011 by Mr_Data

[Thundery wintry showers]

I've remembered that I have an Excel file which includes the Cleadon winter index figures (derived using the same formula as the Manchester one), and added 2010/11 to the list. The current figures stand as follows:

1992/93: 44

1993/94: 92

1994/95: 40

1995/96: 117

1996/97: 64

1997/98: 17

1998/99: 50

1999/00: 41

2000/01: 85

2001/02: 60

2002/03: 61

2003/04: 71

2004/05: 41

2005/06: 48

2006/07: 30

2007/08: 33

2008/09: 76

2009/10: 215

2010/11: 116

Those stats show up how exceptional the winter of 2009/10 was near the Tyne and Wear coast. 2010/11 came out about level with 1995/96 in the end, which seems about right when you offset the January & February against the December. The index stood at a whopping 193 at the end of December 2010 though!

[reef]

Winter Index for Hedon 1987-2011:

1987/88: 35

1988/89: 8

1989/90: 11

1990/91: 107

1991/92: 46

1992/93: 46

1993/94: 80

1994/95: 38

1995/96: 144

1996/97: 48

1997/98: 20

1998/99: 52

1999/00: 33

2000/01: 79

2001/02: 43

2002/03: 52

2003/04: 59

2004/05: 42

2005/06: 53

2006/07: 18

2007/08: 17

2008/09: 50

2009/10: 197

2010/11: 121

So a good winter overall.

[damianslaw]

Despite the very poor February in terms of cold and snow, I will class this winter as a good one overall for wintriness. A superb cold snowy December following a very cold snowy last week of November and then a fairly cold January with many frosts and one or two ice days. The period between 25 Nov and 1 Feb saw at most about 10 mild days these incidentally coinciding with wet periods i.e. 28-31 Dec and 10-16 Jan.

However, it doesn't compare with winters 95/96 and 09/10 which saw generall cold weather persist throughout most of the winter period, in 95/96 only the first two weeks or so of Jan were particularly mild and nothing exceptional and last winter apart from the first 2 weeks of Dec was remarkable for persistant cold with hardly any mild weather - the cold persisting through till mid March.

I do hope the cold weather next winter is more evenly spread and that Feb in particular delivers some cold snowy weather.

Edited March 3, 2011 by damianslaw

[Thundery wintry showers]

I remember that back in January I said that as far as Cleadon was concerned, I would almost certainly place 2010/11 ahead of 2009/10. I noted that the remarkable spell of 24 November-26 December exceeded that of 17 December 2009-9 January 2010, and that February 2010, though cold and relatively snowy, was a relatively boring month with temperature homogeneity and an emphasis on wet snowfalls that didn't settle, so it would require February 2011 to combine mildness with boredom to put 2010/11 behind 2009/10.

Unfortunately, February 2011 emphatically fulfilled that requirement, and so my perception of 2010/11 has thus ended up roughly where the winter index values are placing it- one of the top winters of recent years but some way behind 2009/10 (and as mentioned in another thread, in Norwich it ranks as distinctly poor- the dullest in East Anglia since 1972 and not particularly snowy).

[Summer of 95]

I point out the winter index is a local one and not a national one. You are trying to apply what happened in your locality with what happened in my locality. You can't really do that and here's why. For instance, 2006-07 snow event didn't really effect my area. The snow didn't begin until about 8am and we didn't have a covering. It was nothing compared to further south. Compared to what happened in London etc, it was a non-event.

You mentioned pre-Christmas 2006 frosty spell, only recorded 3 frosts in the entire month. At the moment,its more frosty outside now -4.8C currently then it was at any time during that month. It got down to -8C during December 1999 and -6C during December 1998.

Also saw two days of lying snow during that winter of 1998-99.

It maybe worth using that index for your own data. I remember a few years ago, on another site some member from the SE commenting that they thought winter 2002-03 was a better winter than 2003-04 was and I thought the other way around, so I applied the index to his location and lo and behold it turned out that the index confirmed his point as 2002-03 had a higher value then 2003-04, whilst for me, 2003-04 had the higher value.

Its not full proof but I find it is adequate.

Yes I agree it only works for the area concerned, but my point was about the "falling snow" statistics being such an integral part of it; IMHO that gives too high a score to months like Feb 2010.

I often think that the ratio of snow lying to snow falling gives a good indication of a winter's severity; 2010-11 so far has a ratio of 1.625 (26 days lying to 16 falling). The only other one since 1988 to have a ratio greater than 1 is the great winter of... 2001-02. (7 days lying, 5 falling; 1.4). 2009-10 has a paltry 0.54 (18 to 33).

[Weather-history]

I often think that the ratio of snow lying to snow falling gives a good indication of a winter's severity; 2010-11 so far has a ratio of 1.625 (26 days lying to 16 falling). The only other one since 1988 to have a ratio greater than 1 is the great winter of... 2001-02. (7 days lying, 5 falling; 1.4). 2009-10 has a paltry 0.54 (18 to 33).

I think the flaw in using that type of system can be seen clearly.

1 day of falling snow and 2 days of lying snow would have a ratio of 2. That would have a higher ratio than some of the great winters and all based on just 2 days of lying snow!

Look at 2001-02 and look at 2009-10.

2001-02: 7 days of lying snow and 5 days falling.

2009-10: 18 days of lying snow and 33 days falling.

So 2009-10 has 11 days more lying snow, 28 more days of falling sleet/snow and was a worse (less severe) winter than 2001-02 using that system? The ratio may say paltry but the bare numbers say otherwise.

I also think a lot of people are fickle, I think they would rather have had January 2011, one degree warmer with more marginal snow events than the other way around. I think people's complaints for that January were more based on the lack of snow because it certainly wasn't the temperatures as it wasn't mild overall.

Edited March 10, 2011 by Mr_Data

[Thundery wintry showers]

I certainly agree with you re. January 2011.

One thing that I found particularly interesting was the comparison between February 2010 and February 2011. I remember seeing February 2010 as a disappointment and quite a tedious month for its homogeneity, as did many others- but comparing it to February 2011 makes it look like it was somewhat exciting!

[reef]

I certainly agree with you re. January 2011.

One thing that I found particularly interesting was the comparison between February 2010 and February 2011. I remember seeing February 2010 as a disappointment and quite a tedious month for its homogeneity, as did many others- but comparing it to February 2011 makes it look like it was somewhat exciting!

Curiously February 2010 and 2011 were very close to each other in the sunshine and rainfall stakes here. They were a mere 10mm or so apart on rainfall (both very wet) and only 2 hours apart in the sunshine stakes (and very dull). They were also pretty similar for lying snowfall (1 day vs none). However on falling snow (11 days vs 1 day) and mean temperature (2.5C vs 6.6C) they were remarkably different.

If anything it shows how very different synoptics can often produce very similar 'weather' in the UK and how mild doesnt always equal better!