Daily Report for 10th December 2017

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 0.2 °C (-3.2) 08:58 3.4 °C (-0.1) 9.5 °C (+6.1), 2015 0.2 °C (-3.2), 2017
Maximum Temperature 2.6 °C (-5.7) 03:24 7.2 °C (-1.4) 13.7 °C (+5.4), 2016 2.6 °C (-5.7), 2017
Mean Temperature 0.9 °C (-4.4) 5.4 °C (-0.7) 12.0 °C, 2016 0.9 °C, 2017
Minimum Humidity 74% 02:41 75% 85%, 2020 53%, 2014
Maximum Humidity 96% 22:26 90% 98%, 2013 79%, 2016
Mean Humidity 92% 84% 92%, 2017 71%, 2014
Minimum Pressure 972 hPa 12:24 1014 hPa 1030 hPa, 2013 972 hPa, 2017
Maximum Pressure 1004 hPa 00:00 1025 hPa 1033 hPa, 2009 1003 hPa, 2020
Mean Pressure 982 hPa 1019 hPa 1031 hPa, 2013 982 hPa, 2017
Mean Wind Speed 3.4 mph (-1.7) 5.2 mph (+0.2) 9.2 mph, 2015 2.6 mph, 2013
Maximum Wind Speed 12.6 mph 03:27 12.8 mph 23.0 mph, 2014 8.7 mph, 2011
Maximum Gust 17.3 mph 06:44 20.6 mph 33.7 mph, 2014 12.8 mph, 2011
Mean Wind Direction NE
Rainfall / Snow-melt approx. 20.5 mm 24.4 mm (138%) 20.5 mm, 2017
Maximum Hourly Rain 5.1 mm 06:55 5.1 mm, 2017
Maximum 10-min Rain 1.1 mm 06:41 2.0 mm, 2019
Maximum Rain Rate 13 mm/h 06:34 40 mm/h, 2019
Minimum Dew Point -2.2 °C 02:11 0.8 °C 6.0 °C, 2015 -2.5 °C, 2011
Maximum Dew Point 1.4 °C 06:11 4.9 °C 10.4 °C, 2014 0.6 °C, 2011
Mean Dew Point -0.2 °C 2.8 °C 8.3 °C, 2016 -1.0 °C, 2011
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) 0.2 °C 08:49 4.0 °C 11.2 °C, 2016 0.2 °C, 2017
Day Maximum (09-21) * 1.0 °C * 18:29 7.0 °C 13.7 °C, 2016 1.0 °C, 2017
Max 10m Temp Rise 0.7 °C 02:28 0.3 °C 0.7 °C, 2017 0.2 °C, 2012
Max 1hr Temp Rise 1.8 °C 02:42 1.1 °C 2.3 °C, 2013 0.4 °C, 2016
Max 1hr Hum Rise 11% 04:12 6% 11%, 2017 2%, 2016
Max 10m Temp Fall 0.4 °C 08:12 0.4 °C 0.7 °C, 2013 0.2 °C, 2010
Max 1hr Temp Fall 1.4 °C 08:19 1.1 °C 2.5 °C, 2016 0.3 °C, 2020
Max 1hr Hum Fall 12% 02:37 6% 24%, 2014 3%, 2012
Max 10m Wind Speed 9.1 mph 07:29 9.8 mph 17.6 mph, 2014 6.8 mph, 2011
Minimum Feels-like -4.8 °C 08:46 -1.2 °C 6.6 °C, 2015 -5.0 °C, 2019
Maximum Feels-like 2.3 °C 02:37 6.9 °C 14.8 °C, 2016 2.3 °C, 2017
Mean Feels-like -1.5 °C 2.9 °C 12.4 °C, 2016 -1.5 °C, 2017
Air-frost Hrs 0 hrs 0.7 hrs 0 hrs, 2009 0 hrs, 2009
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 2.4 °C (-2.5) 3.8 °C (-1.3) 9.5 °C (+4.6), 2019 2.2 °C (-2.7), 2020
Humidity Range 22% 16% 39%, 2014 4%, 2016
Pressure Range 32 hPa 11 hPa 32 hPa, 2017 1 hPa, 2013
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 0 [0%]16 hrs (86%) [22%] 6.5 [92%], 2011 0 [0%], 2010
Wet Hours 12
[Mean rain rate: 1.7 mm/h]		16 hrs (82%) [6.8%] 12, 2017 0, 2010
Cloud Cover Overcast
Events Snowfall: ~6 cm
Lying Snow (at 09z): ~4 cm
Comments 03-08 Rain -> 08-15 Snow, mostly settling
Extra Comments
Issues None known
Observer Absent? Yes - observations may be unreliable
Pond Temperature (Heath) 0.0 °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

day graph

Webcam Summary of Cloud Conditions

daycamsumLarge resolution version

Wind rose