May 2021:
It was a cooler and much wetter than average
month. Only in the last few days of the month did the temperatures rise and
the rain ease off.
The total rainfall for the month was 132.2mm which is 212% of the 30 year
average for the month. By way of contrast May's 2021 rainfall was less than
10% of the average. It was the 6th wettest May since continuous records
began in 1881. The wettest was 1932 with 164.3 mm.
Temperatures were below the 30 year average in 2021. At 11.9°C average
temperature this is -1.8°C lower than the 1991-2020 average of 13.7°C.
Minimum temperatures were as cool as 2013 at 7.9°C and maximum temperatures
at 15.8°C in 2021 were lower than any May since 1994.
Also in contrast to May 2020 which had a very high percentage of sunshine,
May 2021 was slightly below the average for the month and approximately 20%
less than last year.
It was the windiest May since 2015. The average air pressure of 1020 mb was
the equal 3rd highest since this data started in 1994. The lowest daily
minimum temperature of 2.2°C on the 2nd was the lowest for May since 2003
when 1.9°C was recorded.
Spring 2021 It
was cooler season than the recent 30 year average. With a mean temperature
9.7°C for the three months it was -1.0°C cooler. It was the below average
minimum temperatures that accounted for most of the cooling being -1.3°C
below the 30 year average.
Even with May's high rainfall the total spring rainfall placed the season
only at 47th wettest out of 140 years of data for Bristol.
Annual 2020:
In 130 complete years of Bristol's annual average temperatures in 2020 it
was the 2nd warmest with an average temperature of 12.4°C. The warmest was
in 2014 at 12.5°C.
The annual rainfall of 1090.2 mm for 2020 was 123% of the 30 year average
for the city of 889.9 mm. As the next 30 year average is prepared
(1991-2020) 1090.2 mm represents 117% of the new average rainfall as this is
increasing.
The average annual 24 hour maximum rainfall of 21.0 mm in 2020 was the
highest since 23.1 mm in 2012 which was the wettest year on record for
Bristol.
In 2020 48% of all the wind directions were from the SW or WSW. With much
less frequencies Southerlies and North Easterlies were next.
Annual average pressure of 1014 mb, equal with last year, was lowest since
1012 mb in 2014.
2020 was the sunniest complete year of data, at 42.5% of the maximum, with
regard to Wm2, since this parameter started in 2006.
In 2020 there were only 1 day when snowfall was observed to fall and none
had any snow lying at 09:00 hours.
There were 10 days when thunder was heard and there were 7 days when a
temperature of below 0.0°C was recorded in 2020.
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
2020 Annual summary is here:
http://www.bristolweather.org/weather2020annual.htm
For the full monthly summary please go here:
http://www.bristolweather.org/weather2021March.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).