Ice Days - long runs and singularities

[damianslaw]

An apt day to start a thread about 'Ice Days', given quite a few places in East of England had one today.

Officially I think an Ice Day is when the temperature stays at or below 0 degrees for 24 hours, reading between 9am and 9am? Correct me if I'm wrong. So a day when you might have 23 hours at 0 degrees or below, but then it creeps up to 0.5 degrees is not classed as an Ice Day.

Ice Days in recent years have been rare for the majority. Indeed I think our last Ice Day was either 2 March 2018 or possibly 17 March 2018. 

Conditions conducive to Ice Days vary, at this time of year with minima solar heating, you don't necessarily need very cold uppers as today has proven, a cold stagnant pool of air at the surface can produce one. Often such days happen when there are light winds, high pressure or a slack pressure pattern overhead. Days of freezing fog also produce the goods. 

Obviously if there are very cold uppers overhead, at least -8 degrees, preferably -10 degrees then an Ice Day is much more likely, snow cover can help as well, more so the later in the season we are say from mid Feb onwards.

We had a mini run of ice days tail end Feb 2018 and start to March 2018 possibly 4. Prior to then, last time we had a lengthy run of ice days was in December 2010, there were 10 between 17 and 26 December - impressive! Also a shorter run of possibly 5 or 6 from 28 November, even more impressive being so early in the season.

Early January 2010 also produced a lengthy run of ice days, possibly 6 or 7.

We had about 8 days end December 1995.

Please share any memories of long runs of Ice Days. Any stats on long runs of yesteryear would be good to know.

 

 

Edited January 9, 2021 by damianslaw

[hillbilly]

I dont have any figures but for where i used to live at 340metres in the Pennines the longest by a country mile that i have witnessed would be that of 1986.It was subzero from the last few days of January until March 4th with i think the exception of a day or so which just went above freezing.I think Co Durham had somewhere that had 32 days subzero.I believe Terminal Moraine has some good figures for this date and he is similar altitude to my old address.No doubt 1947 would have been even longer than that.

[damianslaw]

4 hours ago, hillbilly said:

I dont have any figures but for where i used to live at 340metres in the Pennines the longest by a country mile that i have witnessed would be that of 1986.It was subzero from the last few days of January until March 4th with i think the exception of a day or so which just went above freezing.I think Co Durham had somewhere that had 32 days subzero.I believe Terminal Moraine has some good figures for this date and he is similar altitude to my old address.No doubt 1947 would have been even longer than that.

Jan and Feb 63 probably returned longest run last century for most. Jan to Mar 47 a close second. Yes Feb 86 brought mean temp below 0 degrees for many and there was no let up from the cold all month.

[BornFromTheVoid]

Here are the ice days for the CET, with the 10 year average in red. I actually thought the downward trend would be more stark.

[damianslaw]

2 hours ago, BornFromTheVoid said:

Here are the ice days for the CET, with the 10 year average in red. I actually thought the downward trend would be more stark.

Thanks are the figures for each winter or each year. Surprised how low 2009 is if this is the case. Also 1984 looks very high, whilst cold at times more so in the north, didn't think there were many CET means days below 0 degrees, is it not 1985?

[Summer of 95]

I think the year is the year the Nov/Dec fell in, so 1984 would be 1984/5 etc. 

I'm not surprised the nadir was the late 90s through mid-2000s, but even so I thought 2000/1 and 2001/2 might have had one or two (they certainly both had ice days here). The late 1900s until the late 1920s really does look like a poor period for winters, with the notable exception of 1916/17. 

The freezing fog/inversion setup is the one that produces ice days in mild or non-snowy winters, hence the ice days in 1991/2 and 1992/3 (which hardly had a flake of snow here between them); they both had notable spells of that type of cold. There were also some ice days here (but not by the CET) from that setup in 1994/5 and 2006/7 which were both mild though not snowless. The really poor winters are the ones that have next to no snow but also can't even produce that kind of cold; 2013/14, 15/16, 19/20 and those at the end of the 90s.

[damianslaw]

Still surprised to see such low results for winter 09-10 our coldest since 78-79. Also 78-79 saw few returns as well. Jan 10 must have produced at least three or four such days.

 

[danm]

Genuine ice days here in London are fairly rare. I live in zone 5, near the border with Essex, so out here it may be a little more common than in central London, however if we go by the records from Heathrow airport then it’s pretty clear how rare they are. 

There have been single ice days scattered about here and there, but the last time Heathrow seemed to record multiple ice days in one spell was in the late December 96/early Jan 97 easterly. 31st Dec recorded a high of -0.1c, 1st Jan -1.7c, 2nd Jan 0.5c (not an ice day) and 3rd Jan -0.8c. Even during the Feb/March 2018 BFTE, Heathrow only had one genuine ice day (to my surprise), however I do know a local weather station here in Chingford, NE London had 3 consecutive ice days in that spell. 

Before 96/97, Feb ‘91 had four consecutive ice days (very rare for London) between the 6th and the 9th: 0c, -3.7c, -2c, -2.5c.

Jan 1987 also had four consecutive ice days between the 11th and 14th: -3c, -6c, -3c, -2c. It was also -0.5c on the 17th. 

Jan 1985 had five ice days in the calendar month: two consecutive on the 7th and 8th: -1.7c, -1c and three consecutive again between the 15th and 17th: -0.6, -4c, -1c. 

Feb 1985 had this run between the 10th and 15th: -0.9c, -0.5c, 0.3c, -1c, 2c, 0c - four ice days out of six. 

Feb 1986 had three ice days scattered through the month, although that spell was more notorious for the length rather than depth of cold. 

Looking back to 81/82 there were a couple of ice days in Dec ‘81 and three consecutive ice days in Jan ‘82. 78/79 also had a few.

 

The above shows how much rarer consecutive ice days have become in London. Could be a combo of some climate change and the urban heat island effect playing a part. 

Edited January 12, 2021 by danm

[BornFromTheVoid]

11 hours ago, damianslaw said:

Thanks are the figures for each winter or each year. Surprised how low 2009 is if this is the case. Also 1984 looks very high, whilst cold at times more so in the north, didn't think there were many CET means days below 0 degrees, is it not 1985?

They are for the winter periods, so they cross over years. So 2020 is just November and December so far.
So there, 1984/85 had 11, 1985/86 had 7, and 1986/87 had 6.

[A Face like Thunder]

'Looking back to 81/82 there were a couple of ice days in Dec ‘81 and three consecutive ice days in Jan ‘82' (danm). 

I am a bit surprised that there were only two ice days in December 1981. I was living and working in South London at the time, and whilst I accept that this was not Central London, I would have thought the widespread snow and cold of that month would have resulted in more than two ice days in the capital. 

[reef]

There have been a total of 34 ice days in this area since 1980:

The longest run without was from Dec 1995 - Dec 2005. January went without one from 1987-2013 (26 years). December had the most in the 40 year period (14 days) but that was heavily skewed by Dec 2010 which saw 7 days alone - the most of any single calendar month. Outside of the winter months, just November 1993 saw a single ice day. March has never managed it, though 2018 came close with a max of 0.3C on the 1st.

They are definitely becoming less common here, present in only 5 years out of the last 25 compared to 9 of the previous 15 years.

[Thundery wintry showers]

When I was taking weather records up in Cleadon in Tyne and Wear we didn't get long runs of ice days due to the moderation from the North Sea, but there was one on 23 November 1993, there were a few at the end of December 1995 (26th to 28th), and I recall one on 2 January 2002 during a bright frosty spell with snow cover left over from snow showers at the end of December 2001.  

On 29 December 2005 the temperature only got to -1.2C during the day, though it rose to 0.9C the following morning, meaning that it wasn't an ice day under the 0900-0900 system, but would qualify under an 0000-0000 or 0900-2100 system.  7 January and 27 November 2010 were ice days (27 November got to -0.1C), and there were scattered ice days through December 2010, the coldest being the 20th at -3.3C max.  A north-easterly off the North Sea brought maxima of 1 to 2C on the 22nd and 23rd and prevented a long run of sub-zero maxima, but with the comparative warmth came snow showers which topped up the snow cover.

It's even rarer down here near the English Riviera in south Devon, though I think Exeter just managed an ice day on 1 March 2018 (the day when there was 17cm level snow and drifts about a foot deep) and again December 2010 had quite a few ice days in this part of the country - going by Wunderground's readings from Exeter Airport there may have been four from the 21st-24th.

I believe Southern England had long runs of ice days in February 1947 and January 1963.

Edited January 12, 2021 by Thundery wintry showers

[damianslaw]

9 hours ago, reef said:

There have been a total of 34 ice days in this area since 1980:

The longest run without was from Dec 1995 - Dec 2005. January went without one from 1987-2013 (26 years). December had the most in the 40 year period (14 days) but that was heavily skewed by Dec 2010 which saw 7 days alone - the most of any single calendar month. Outside of the winter months, just November 1993 saw a single ice day. March has never managed it, though 2018 came close with a max of 0.3C on the 1st.

They are definitely becoming less common here, present in only 5 years out of the last 25 compared to 9 of the previous 15 years.

Surprised there were no ice days in Jan 2009 and Jan 2010, especially the latter. Did March 2013 not produce one. We had one on 11 March 2013, probably latest date in a long time.. didn't quite manage any later that month.

[reef]

46 minutes ago, damianslaw said:

Surprised there were no ice days in Jan 2009 and Jan 2010, especially the latter. Did March 2013 not produce one. We had one on 11 March 2013, probably latest date in a long time.. didn't quite manage any later that month.

Its quite difficult for us to achieve ice days due to our proximity to the North Sea (7 miles)  as winds will usually be onshore to some extent in a cold spell. It requires calmer conditions or deep cold and even then, once the sun gets stronger its very difficult (only happened twice after mid-Feb in the 40 year period). 

[Weather-history]

On 11/01/2021 at 23:41, damianslaw said:

Still surprised to see such low results for winter 09-10 our coldest since 78-79. Also 78-79 saw few returns as well. Jan 10 must have produced at least three or four such days.

 

That's because ice days are actually pretty rare, I mentioned sometime back even a winter like 1962-63 didn't have many CET days below zero for the maximum. The CET maximum for January 1963 is 0.6C

Its the minima that is the  main contributor to a month being sub zero, an example being December 2010, the minima really pulled down the mean for that month, another is February 1895.

[A Face like Thunder]

According to Philip Eden, February 1956 was one of the coldest months in the twentieth century. Temperatures remained well below zero from 31st Jan to 3rd Feb and from 18th to 25th Feb inclusive. J H Brazell - in his book on London weather - reported that the mean temperature (F) in the capital was 31.9 (-8.0 different to average), and the maximum temperature on 1st was 24.3 (8 below zero). I vaguely remember this cold spell, and in particular the disastrous consequences as a 6-year old of not being able to use the one school loo because it had frozen over!

Eden reports that in early 1963, temperatures remained below zero 'for long periods, particularly in central, southern and eastern parts of England'. Mean temperature in Jan 1963 in London (Brazell) was 29.7F (2.3 below zero and 9.8 below average), with a maximum temperature on the 24th of 27.0 (5 below zero). 

1947 - and Eden reports that the temperature remained below zero continuously from 11th to 23rd Feb in large parts of the UK. Mean temperature in Feb was 30.0  and maximum on the 17th was 27.7.

1940 - another 'ice age' winter and the temperature remained below zero for lengthy periods, with a mean of 31.4 in January and a maximum temperature of 27.7 on the 20th Jan.  

[danm]

23 hours ago, A Face like Thunder said:

'Looking back to 81/82 there were a couple of ice days in Dec ‘81 and three consecutive ice days in Jan ‘82' (danm). 

I am a bit surprised that there were only two ice days in December 1981. I was living and working in South London at the time, and whilst I accept that this was not Central London, I would have thought the widespread snow and cold of that month would have resulted in more than two ice days in the capital. 

The records for Heathrow in December '81 show three ice days (-1c on the 10th and 12th and 0c on the 23rd). There were plenty of other days with maxes of 1c, 2c or 3c so the month was still cold. 

[danm]

49 minutes ago, A Face like Thunder said:

According to Philip Eden, February 1956 was one of the coldest months in the twentieth century. Temperatures remained well below zero from 31st Jan to 3rd Feb and from 18th to 25th Feb inclusive. J H Brazell - in his book on London weather - reported that the mean temperature (F) in the capital was 31.9 (-8.0 different to average), and the maximum temperature on 1st was 24.3 (8 below zero). I vaguely remember this cold spell, and in particular the disastrous consequences as a 6-year old of not being able to use the one school loo because it had frozen over!

Eden reports that in early 1963, temperatures remained below zero 'for long periods, particularly in central, southern and eastern parts of England'. Mean temperature in Jan 1963 in London (Brazell) was 29.7F (2.3 below zero and 9.8 below average), with a maximum temperature on the 24th of 27.0 (5 below zero). 

1947 - and Eden reports that the temperature remained below zero continuously from 11th to 23rd Feb in large parts of the UK. Mean temperature in Feb was 30.0  and maximum on the 17th was 27.7.

1940 - another 'ice age' winter and the temperature remained below zero for lengthy periods, with a mean of 31.4 in January and a maximum temperature of 27.7 on the 20th Jan.  

Seven ice days at Heathrow in Feb 1956 looking back at the records. That is a lot for down here! Added to that, there were 4 other days when the daytime max was between 0c and 1c. 

[Chesil View]

The exceptional spell of cold spell of Nov/Dec 2010 saw 16 ice days at my weather station in Winfrith  Newburgh just a couple of miles from the Channel coast in south Dorset.  2 of those ice days were in November, totally without precedent at that location for that month.

There was also a run of 9 consecutive ice days from 18th to the 26th December.

These included the coldest christmas day on record in Dorset  min -10.2c max minus 3.4c

and a new record min for my weather station of minus 13c on tje morning of the 26th.

Not bad bad for the south coast of England in a globally warmed world.

Edited January 13, 2021 by Broadmayne blizzard

[damianslaw]

1 hour ago, Broadmayne blizzard said:

The exceptional spell of cold spell of Nov/Dec 2010 saw 16 ice days at my weather station in Winfrith  Newburgh just a couple of miles from the Channel coast in south Dorset.  2 of those ice days were in November, totally without precedent at that location for that month.

There was also a run of 9 consecutive ice days from 18th to the 26th December.

These included the coldest christmas day on record in Dorset  min -10.2c max minus 3.4c

and a new record min for my weather station of minus 13c on tje morning of the 26th.

Not bad bad for the south coast of England in a globally warmed world.

Wow really 16 days! Its possible the cold lasted from about 25th Nov until 9 Dec, which is 15 days..

We had quite a few ice days during that period, possibly 5 in a row from 28th Nov until 2 Dec, then a slight rise 3-5 Dec, possibly 2 or 3 more 6-8 Dec. 

[Chesil View]

I think your memory might be playing tricks the The cold in December 2010 lasted from the 25th Nov to the 27th December.

[Weather-history]

6 minutes ago, Broadmayne blizzard said:

I think your memory might be playing tricks the The cold in December 2010 lasted from the 25th Nov to the 27th December.

I distinctly remember a less cold period between the 9th and 17th December 

[Chesil View]

Just now, Weather-history said:

I distinctly remember a less cold period between the 9th and 17th December 

There was an easing of the extreme cold in that period but only one daye exceded 4 c at my station at Winfrith between 26th nov  and. The 27th Dec.  . In Dorset Dec 2010 was colder than Dec 1990.

[Chesil View]

That should read colder than Dec 1890.

[hillbilly]

2 hours ago, Broadmayne blizzard said:

That should read colder than Dec 1890.

Yes that is a good stretch of ice days for Dorset but here in the Pennines December 1981 was colder than 2010 and had far more snow with huge drifts.I dont however have a record of ice days  but usually at the 340 metres we lived it is 3 degrees cooler there than in the valley bottom[sea level] at any time of the year.