By Roger Brugge
“Persistent low cloud, spells of fog, minimal amounts of sunshine and night-time temperatures more suited to September.” Such a description of the weather of the past ten days or so had me reaching for the records to try to place the recent weather conditions into a historical context.
Temperature
Daytime temperatures of 16.8 °C and 16.7 °C on the 6th and 7th at the University’s climatological weather station are not that unusual for early November; 16.8 °C was reached in November 2014 with 18.1 °C in November 2010 – the latter has only been surpassed in November by 20.4 °C on 5 November1938, 18.7 °C on 5 November 1946 and 18.2 °C on 4 November 1946 (figures taken from One hundred years of Reading weather). Even more unusual, the minimum temperature of 13.3 °C on Saturday 7th in 2015 has only been bettered on five nights at the University in the past century, and in fact some nights this month so far have seen higher temperatures than might be expected by day – see Figure 1.
Figure 1. Daily maximum and minimum temperatures during 1-10 November 2015. Updated daily at http://www.met.reading.ac.uk/Data/EPHEMERAL/0temperature.png
However, not only is it in Reading that the temperatures at the start of November 2015 have been unusual. Trawscoed in mid-Wales broke the UK’s November temperature record on Sunday 1st, with 22.4 °C being reached. The previous November record was also in Wales, when temperatures reached 21.7 °C at Prestatyn in 1946. On Monday 2nd this year Trawscoed reached 22.3 °C, while the Eskdalemuir observatory in Dumfries and Galloway had its highest November temperature on record at 16.3 °C. It is hardly surprising then, that average temperatures so far this month have been typically 3-5 degC above the average for November (admittedly this is the average for the whole of November, but nevertheless…) – see Figure 2. In Reading the average temperature of 11.9 °C over the first nine days of November amounted to the mildest such spell on these dates since 1982 when the average temperature was 12.0 °C – no other November in the 1908-2015 station record has started as warm as these two.
Figure 2. Mean temperature anomaly (with respect to 1981-2015) for November 2015 (up to 0600 GMT/10th) over the British Isles with respect to the monthly mean for the whole month. This image (and other illustrating the current status of the month) are updated three times each day at http://www.met.reading.ac.uk/~brugge/uksummary.html
Sunshine
Just 30 minutes of bright sunshine has been recorded during the first nine days of November 2015 at the University. This dull spell is one of the dullest on record at this time of year – not a record but certainly worth a mention as this list of the lowest 8-day (or longer) sunshine totals at the University involving at least 7 November days shows:
17-29 Nov 1958 nil sunshine (13 days)
1-9 Nov 2015 0.5 h (9 days)
20 Nov – 1 Dec 1963 0.4 h (12 days)
29 Oct – 7 Nov 1982 0.3 h (10 days)
31 Oct – 7 Nov 1972 0.1 h (8 days)
Again, these dull conditions have been widespread across the British Isles this month – initially due to high pressure and fog/low cloud and then to cloud-bearing areas of low pressure; sunshine totals as of 0600 GMT on the 10th include (values in parentheses are the percentage of the total for the whole of November recorded so far):
Leeming, North Yorkshire 3.8 h (6%)
Hawarden, Clwyd 3.7 h
Shobdon, Herefordshire 3.0 h
Shoeburyness, Essex 1.3 h
Odiham, Hampshire 2.1 h (3%)
Charlwood, Surrey 2.5 h (3%)
These are in contrast to parts of northern Scotland where the sunshine total so far amounts to over 40% of the average for the whole of November. While there are still a lot of November days to come yet in 2015, it is worth noting that three dullest Novembers at the University have been those of 1962 (32.6 h), 1994 (34.6 h) and 2014 (38.2 h) – so maybe the present month might be the second successive dull November in Reading?
Mean sea level air pressure so far this November has been slightly above average – and this has helped to give persistent low cloud and poor visibility. Reading has had two days with fog (visibility below 1000 metres) at 0900 GMT – November 2014 had 5 days with fog and there were 8 days with fog at this time of day in 2011 – so the total so far in November 2015 is not that unusual. But many mornings this month have also been quite misty and ‘grey’.
So, with no air frost so far this autumn many will be wondering when it will turn cold. Statistically, the median (i.e. middle) date for the first air frost of the autumn/winter during the period 1925-2014 at the University was 3 November; only in 10 per cent of the years did the first air frost occur after 24 November.
Time will tell …
This blog was originally posted on 10 November 2015. It was reposted on 4 December following computer system issues.