December 2021:
The average temperature of 8.3°C was 2.2°C
warmer than the 30 year average for the month and was the largest positive
monthly anomaly of 2021.
The average minimum temperature for December was, at 6.2°C was higher than
the November minimum temperature of 5.7°C.
Rainfall at 78.4 mm was 77% of the 30 year average for the month. It was the
driest December since 2016 when only 30.3 mm was recorded.
It was the dullest December with 17.4% of the maximum possible solar
radiation since 2015. Rainfall at 110.3 mm was 114.7% of the 30 year
average.
The average temperature of 7.3C was 1.4°C above the 30 year average for the
month.
The highest daily
minimum temperature of 13.1°C on the 31st was the highest since this data
started for Bristol in 1960.
The highest daily mean temperature of 13.9°C on the 31st was the joint
highest, with 2015, since this data started in 1993.
The lowest minimum temperature of -0.7°C for the month on the 27th was the
highest since 4.9°C was recorded on 25th December 2015.
Autumn 2021 With
respect to the autumn season September - November the mean temperature was
13.2°C. This makes 2021 the 4th warmest autumn in 131 years
of data for Bristol. The 30 year average for the season in Bristol is
12.0°C. The warmest was in 2011 with an average temperature of 13.7°C
With rainfall high in October and very low in November the autumn rainfall
of 223.2 mm was 35 mm below the 30 year average.
Annual 2021:
In 131 complete years of Bristol's average temperatures in 2021 it was the
joint 10th warmest with (with 1999 & 2015) with an average temperature of
11.9°C. The 2nd warmest month, after July, was September.
The annual rainfall of 891.1 mm for 2021 was 97.5% of the 30 year average
(1991-2020) for the city of 913.8 mm. The wettest month was October with
145.6 mm (145.6%) of rainfall whilst the driest was November with only 14.1
mm (14.0%) of rain.
In 2021 the predominate wind direction was from the SW or WSW accounting for
42.7% of all the wind directions. The annual average pressure of 1017 mb
was the equal 3rd highest in 27 years of data at this site. It was the least
windy year since data began in 2005 with regard to the average wind speed.
There were no wind gusts over 50 mph for the 1st time in 4 years. Thunder
was only heard on 1 occasion. In 2021 there were only 4 occasions when
snowfall was observed to fall and only 1 had any snow lying at 09:00 hours.
To
view a full report of the Bristol Annual Weather 2020 and a discussion of trends
etc click here. This is a Word created .doc document
which is produced annually for a couple of Bristol Naturalist Society
publications. Please acknowledge the source if quoting any of the contents.
Thank you.
The
2021 Annual summary is here:
http://www.bristolweather.org/weather2021annual.htm
For the full monthly summary please go here:
http://www.bristolweather.org/weather2021
December.htm
The
Meteorological site is situated in an urban housing area approximately one
mile to the south of the Centre of Bristol.
This area is in a district called Totterdown.
Statistical correlations with the Bristol
Meteorological Office site, that was
less than two miles to the North and was
situated on top of a City Centre office block, were generally good with
rainfall and barometric data particularly close.
The site of the station is approximately 34 metres above sea level with the
manual instruments mounted in a Stevenson screen. The screen is sited
centrally in a small concreted garden area. A Snowdon
rain gauge is mounted correctly in the ground but does not have the full open
space required around it. A Davis
Vantage Pro2 Plus automatic weather station (AWS) was
added in May 2005 and this is mounted 4 feet above a concrete shelter. The
wind data is gathered automatically from a Davis Vantage Pro2 Plus anemometer which is
sited 3.3 metres (10 feet) above the house top.
Manual observations are still taken at approximately 09:00 hours GMT every
day for rainfall and cloud cover. Rainfall manually recorded in the Snowdon rain gauge is entered for the previous day. The
wind data is constantly logged and automatically reset at 24:00 hours GMT
every day (in the summer BST -1 hour. The Davis rainfall tipping bucket was recalibrated in November 2005 and is now
consistently under 3% under recording (an improvement from installation in
May 2005 when 10% was more
typically the norm).
Since the arrival of the Davis
Vantage Pro2 Plus equipment in May 2005 temperatures, humidity and barometric
pressure are recorded from the new equipment. These figures will be more
accurate and will be taken at exactly 09:00 GMT (in the summer BST -1 hour)
as the data is now logged to a computer.
By default the Davis
equipment records every parameter for the 24 hour period 00:00 to 23:59 BST
or GMT. Data analysis will enable manual data extraction of temperatures and
rainfall to 09:00 GMT (adjusted in the summer). Due to the 0.2 mm (tipping
bucket) measurements of precipitation recorded by the Davis equipment the
Snowdon rain gauge will still be used due to its greater accuracy (see
above).