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xmetman

The coldest night of the year?

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Hi
 
So what is statistically the coldest night of the year?
 
Well the only data I have to work on to find that out here in the UK is the daily Central England Temperature series that started with listing daily maxima and minima in 1878. I did blog about something very similar last year in an article that I entitled “13/14 February frostiest night of the year“,  but since then I’ve done a bit of extra work and tagged another graph onto the collection. I posted that originally on Blogger, and then imported it into WordPress and in the process the graphics got shrunk, so I can now remedy that as well!
 
What prompted this blog or re-blog if you like, was a post to UK Science Weather this week about what the coldest day of the year was likely to be in London, so I revisited the code and hence this blog.
 
The frost year starts as far as the CET series at the beginning of October and ends in mid-May. I’m afraid that I still find that the night of the 13/14th of February to be statistically the coldest night of the year if you calculate daily mean minimums from 1878, with a value of around 1.8°C. It also ends up being the frostiest night of the year with a 41% chance of an air frost.
 
Not surprisingly the trend since 1878 is progressively less frost days, surprisingly at a quick glance 2010 had more frosts than 1947, 1963 and 1978, and looks like the frostiest since 1917. Of course I may have screwed up with the figures, and if I have post me a comment.
 
Bruce.
 
The following graphs are in my blog:
 
(1) Frequency of frost and ice days in the Daily CET series (1 October - 31 May)
(2) Daily CET mean minimum (1 October - 31 May)
(3) Annual total frost & ice days in the Daily CET series (1878-2013)
 
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It makes sense that mid Feb has the coldest nights when you consider that the Atlantic is usually quiet and settled conditions typically prevail at this time of year. It's also still in the colder half of Winter and although the nights are getting shorter there is very little latent heat left in either the ground or seas around the UK.I suspect that January would record colder nights than Feb under the exact same Synoptics but the reason Feb "wins" is because January often experiences Atlantic influences, making difficult conditions for an air frost.It's interesting to see early - mid March looking as frosty as any other time of year. March is kinda like a slightly moderated Feb, expected given the losing battle to the sun.

 

*Edit*

 

I've just remembered this thread I created over a year ago: http://forum.netweather.tv/topic/74747-average-record-minimaan-unscientific-study/

 

Just dug up some figures on the lowest minima of the year for each year since 1910 (I think). Interestingly, December 30th is the date that has seen the coldest temperature of the year - occurring in 6 years. This is followed by...wait for it...February 14th, with 5! Actually, March 3rd has also recorded the lowest temp of the year 5 times, too.

Edited by March Blizzard

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Amazing what statistics can show. The frequency of both 13/14 February and 30 December in such a long time scale does suggest a scientific/meteorological reason for this. Much as you both have suggested.

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Amazing what statistics can show. The frequency of both 13/14 February and 30 December in such a long time scale does suggest a scientific/meteorological reason for this. Much as you both have suggested.

There is a strong cluster around late December to about 10th Jan and another in mid Feb. There is another one in early March around the 3rd.January has 39 in total, December 31 and Feb 30. March has 16. There is some overlap where two different dates record the same temperature in the same year.My crude study points to the first half of Jan as the prime time of year to see record low minima, not necessarily when the coldest night of the year will fall in any given year.

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