Daily Report for 20th December 2019

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 5.8 °C (+2.8) 21:57 3.8 °C (+0.5) 9.4 °C (+6.4), 2015 -7.2 °C (-10.2), 2010
Maximum Temperature 9.8 °C (+2.3) 00:01 9.2 °C (+1.1) 14.6 °C (+7.1), 2015 0.3 °C (-7.2), 2010
Mean Temperature 8.2 °C (+2.5) 6.7 °C (+0.8) 12.2 °C, 2015 -3.2 °C, 2010
Minimum Humidity 85% 14:16 77% 96%, 2012 62%, 2014
Maximum Humidity 96% 09:09 93% 98%, 2012 80%, 2016
Mean Humidity 92% 87% 98%, 2012 75%, 2014
Minimum Pressure 977 hPa 08:20 999 hPa 1034 hPa, 2017 977 hPa, 2019
Maximum Pressure 988 hPa 00:00 1012 hPa 1036 hPa, 2017 988 hPa, 2019
Mean Pressure 982 hPa 1006 hPa 1035 hPa, 2017 982 hPa, 2019
Mean Wind Speed 5.0 mph (-0.1) 6.1 mph (+1.0) 8.1 mph, 2015 2.6 mph, 2016
Maximum Wind Speed 16.2 mph 16:01 15.6 mph 20.1 mph, 2013 8.6 mph, 2017
Maximum Gust 26.5 mph 16:00 25.3 mph 30.8 mph, 2013 11.5 mph, 2017
Mean Wind Direction SSW
Rainfall 15.2 mm 76.7 mm (216%) 21.7 mm, 2012
Maximum Hourly Rain 3.1 mm 05:32 4.1 mm, 2012
Maximum 10-min Rain 0.9 mm 05:21 1.2 mm, 2012
Maximum Rain Rate 7 mm/h 05:21 9 mm/h, 2012
Minimum Dew Point 4.4 °C 21:57 1.9 °C 6.5 °C, 2015 -9.3 °C, 2010
Maximum Dew Point 8.8 °C 10:04 7.1 °C 9.7 °C, 2017 -0.4 °C, 2010
Mean Dew Point 7.0 °C 4.6 °C 8.4 °C, 2017 -4.7 °C, 2010
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) * 8.5 °C * 04:44 4.6 °C 12.3 °C, 2015 -7.2 °C, 2010
Day Maximum (09-21) * 9.7 °C * 14:05 9.1 °C 13.0 °C, 2015 0.3 °C, 2010
Max 10m Temp Rise 0.2 °C 08:33 0.3 °C 0.7 °C, 2009 0.2 °C, 2012
Max 1hr Temp Rise 0.5 °C 08:47 1.2 °C 2.1 °C, 2009 0.5 °C, 2015
Max 1hr Hum Rise 4% 02:38 5% 8%, 2018 1%, 2012
Max 10m Temp Fall 0.3 °C 14:48 0.4 °C 0.5 °C, 2009 0.1 °C, 2017
Max 1hr Temp Fall 1.3 °C 17:01 1.3 °C 1.7 °C, 2015 0.1 °C, 2017
Max 1hr Hum Fall 5% 13:59 6% 9%, 2013 2%, 2012
Max 10m Wind Speed 11.5 mph 10:39 11.7 mph 15.5 mph, 2013 6.2 mph, 2010
Minimum Feels-like 2.3 °C 20:56 -0.4 °C 5.7 °C, 2015 -10.2 °C, 2010
Maximum Feels-like 9.5 °C 02:24 9.0 °C 15.5 °C, 2015 0.3 °C, 2010
Mean Feels-like 6.3 °C 4.7 °C 12.5 °C, 2015 -5.0 °C, 2010
Air-frost Hrs 0 hrs 0 hrs 17 hrs, 2010 0 hrs, 2011
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 4.0 °C (-0.5) 5.4 °C (+0.6) 7.9 °C (+3.4), 2013 2.3 °C (-2.2), 2016
Humidity Range 11% 16% 29%, 2011 2%, 2012
Pressure Range 11 hPa 13 hPa 13 hPa, 2012 2 hPa, 2010
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 0.3 [4%]51 hrs (139%) [36%] 7 [100%], 2009 0 [0%], 2012
Wet Hours 12
[Mean rain rate: 1.3 mm/h]
82 hrs (205%) [17%] 16, 2012 0, 2013
Cloud Cover Overcast transitioned to Mostly Cloudy
Events None
Comments am rn then shs pm
Extra Comments
Issues None known
Observer Absent? Yes - observations may be unreliable
Pond Temperature (Heath) 5.0 °C
Notes
Times of extremes are computed using the midpoint of the longest continuous period at that extreme value.
Cumulative anomalies are reported according to the expected value for the month-to-date rather than month-end.
Sun hrs are initially pulled from the official weather station at Heathrow, and later adjusted by hand to reflect local conditions based on webcam observations. Wet hrs are dervied algorithmically from rainfall data, though may be adjusted manually. Cloud cover and Events are manually reported, often with multi-week delays.
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Daily Graph of Conditions

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Webcam Summary of Cloud Conditions

daycamsumFull resolution individual images at up-to 5 minute intervals

Wind rose