December 2012

The cliffs east of Sidmouth, basking in December sunshine.
The cliffs east of Sidmouth, basking in December sunshine.

Summary for  December 2012
Mean Max: 9.8C (+0.5C)
Mean Min: 3.8C (+0.5C)
Mean: 6.8C (+0.5C)
     
High Max: 13.4C 22nd 
Low Max: 4.7C 11th
High Min: 9.3C 23rd 
Low Min: -2.9C 11th
Mean Grass Min: 0.5C  
Grass Min: -5.3C 11th
     
Rain Total (gauge): 171.5 mm (191%)
Rain Total (tipping bucket): 168.3 mm (187%)
Rain Days >0.2 mm: 23 Days  
Rain Days >1.0 mm: 21 Days  
Max 24 hrs: 29.3 mm 22nd 
Days without any rain: 8  
     
Air Frost: 5 Days  
Grass Frost: 16 Days  
Snow Falling: 0 Days  
Snow (50%) @ 9am: 0 Days  
Ice Days: 0 Days  
Thunder Heard: 1 Day  
Hail <5 mm: 1 Day  
Hail >5 mm: 0 Days  
Fog @ 9am: 0 Days  
     
Total Monthly Sunshine: 82.6 Hours (141%)
Most Sunshine in a Day: 7.5 Hours 8th
Average Daily Sunshine: 2.7 Hours  
Sunless Days: 9 Days  
Cloudless Days: 4 Days  
Total Possible Sunshine: 249.6 Hours  
Percentage of Total Sun: 33%  
Maximum UV Index: 0.9 8th
Time of Max UV:   12:00
     
Mean Soil Temp @ 30 cm: 7.7C  
Min Soil Temp @ 30 cm: 5.7C 12th
Max Soil Temp @ 30 cm: 9.3C 24th
Mean Soil Temp @ 100 cm: 9.9C  
Min Soil Temp @ 100 cm: 9.2C 20th
Max Soil Temp @ 100 cm: 11.3C 1st
     
Mean 10 Min Wind >39 mph: 0.01 Days  
N: 4.05 Days  
NE: 0.47 Days  
E: 2.11 Days  
SE: 2.08 Days  
S: 6.56 Days  
SW: 5.95 Days  
W: 1.29 Days  
NW: 4.66 Days  
Calm: 3.83 Days  
Wind Chill Low: -4.2C 11th
Mean Wind: 3.6 mph  
Max Gust: 40 mph 29th
  ys  
Mean Cloud Cover: 70%  
Mean RH @ 9am: 94%  
Rain Duration >0.1mm/hour: 96.8 Hours  
Frost Duration: 47.5 Hours  
Max Frost Duration in a Day: 14.8 Hours 11th
     
Mean Sea Temperature: 10.2C (+0.4C)
Normal for Month: 9.8C  
Max Sea Temperature: 11.2C 1st
Min Sea Temperature: 9.4C 16th
     
Mean Pressure @ 9am: 1008.7 hPa (-5.9 hPa)
Mean Pressure: 1009.1 hPa (-5.5 hPa)
Max Pressure: 1031.8 hPa 11th
Min Pressure: 974.3 hPa 14th
Max Change in 24 hours: 23.6 hPa 14th
   
Radiation Daily Mean: 2.6 MJ/m  
Max Daily Value: 5.8 MJ/m 1st
Min Daily Value: 0.5 MJ/m 31st
Number of Days with Data: 31 Days  
1-Hour Maximum: 363 W/m 25th
Starting Time of the Hour:   12:00
     
Max Dewpoint: 12.9C 22nd 
Min Dewpoint: -3.9C 11th
Mean Dewpoint: 5.0C  
     
Max Humidity: 100% 21st
Min Humidity: 66% 5th
Mean Humidity: 90% (+3)

 

A generally mild (especially by day) and very wet month, though there were a few sharp frosts at first. No air frosts since the 11th and extremely mild both day and night from the 22nd onwards.

Temperatures were a little below normal until the 14th, but then things turned much warmer and the frosts disappeared. Very mild nights for the last 10 days of the month.

Another extremely wet month, keeping the trend of wetter than average months going that started in June. The Otter Valley did not receive as much rainfall as other parts of Devon & Cornwall, probably due to the rainfall shadow effect of Dartmoor in a SW airstream.
December often sees a few air frosts and this year was no exception. Though from the 11th onwards the nights remained mild and frost-free. The cold air that affected many parts of England did not reach here and hence no snow was seen falling or lying. There was a thunderstorm with hail at midday on the 16th. Unusually for December, there were no foggy mornings.
Sunshine amounts were above average despite a high amount of cloud during the 2nd half of the month. This was due to a run of very sunny days during the first and second weeks with sunshine levels attaining up to 70% of the total possible for this time.
Soil temperatures slowly declined through to mid-month but then rose again. 30 cm soil temperatures actually peaked during the 4th week of the month.
Overall this was quite a breezy month but that is not unusual for December. There were no high wind speeds though overnight on the 29th, gusts did reach 40 mph (60 kph). Winds were dominant from the south and south-westerly directions.
The rainfall duration of 97 hours and reflects the high amount of rainfall that actually fell during this month.
Sea surface temperatures fell sharply during the cold nights of the first and second weeks, but then rose again with the warmer conditions from the 11th onwards.
Mean pressure was rather below the average for December and indicative of the very unsettled conditions that dominated this month.
A new sensor has been added that measures solar irradiance in watts per square metre falling on a horizontal surface.
Dewpoints were above the average.
Relative humidity was a little above normal.
Weather Data for Otter Valley, Devon.  December 2012  
  Temp oC Grass Hum (%) Soil oC DP (oC) Wind (mph) Rain Air (hPa) W/m UV Sun  
  Min Max Min Min Max 30 100 Min Max Max Ave Run mm Min Max Max Max Hours Observations
1 -1.1 9.6 -3.3 79 99 8.1 11.3 -1.9 6.5 16 1.3 30 0.0 1015 1018 342 0.8 6.4 Sunny all day
2 -1.2 7.4 -3.4 87 99 7.7 11.1 -2.0 6.9 9 0.5 12 3.8 1015 1019 315 0.8 3.4 Sunny ints am, cloudy pm
3 7.3 10.7 -0.2 80 99 7.9 10.9 2.4 10.6 17 2.0 48 1.8 1007 1015 190 0.7 2.3 Sunny intervals all day
4 3.4 7.4 -1.6 82 98 8.2 10.7 0.0 5.0 15 1.5 36 7.8 1005 1009 324 0.7 2.2 Sun and showers all day
5 1.4 7.1 -3.2 66 99 7.8 10.5 -1.3 4.1 16 1.8 43 2.3 1003 1018 335 0.7 6.3 Sunny intervals all day
6 -2.4 6.3 -4.5 85 99 7.2 10.4 -3.3 4.4 18 1.0 23 0.0 1006 1019 106 0.5 0.0 Cloudy all day
7 4.2 8.7 0.3 75 94 7.0 10.2 2.0 6.2 22 5.3 127 6.0 1001 1016 296 0.7 3.8 Sunny intervals all day
8 0.3 9.6 -2.7 72 98 7.1 10.1 -1.0 5.1 16 1.4 34 0.0 1016 1028 323 0.9 7.5 Sunny all day
9 0.4 9.1 -2.3 86 99 6.8 10.0 -1.1 7.2 16 2.7 65 0.0 1020 1028 91 0.6 0.0 Cloudy all day
10 -0.4 7.9 -3.4 71 99 7.0 9.8 -1.4 5.0 12 1.3 32 0.0 1020 1029 329 0.9 7.5 Sunny all day
11 -2.9 4.7 -5.3 79 98 6.3 9.8 -3.9 1.9 6 1.0 24 0.0 1028 1032 245 0.7 7.4 Sunny all day
12 2.2 6.3 -2.8 67 93 5.7 9.5 -1.6 2.0 21 3.4 82 0.0 1012 1028 237 0.7 2.0 Sunny intervals all day
13 2.7 5.9 -0.2 77 92 5.8 9.4 0.0 3.4 12 2.2 53 0.0 998 1011 280 0.7 2.1 Sunny ints am, cloudy pm
14 7.2 11.2 3.6 88 98 6.3 9.2 3.8 10.7 28 6.8 163 17.5 974 998 49 0.0 0.0 Rain am, showers pm
15 7.2 10.8 1.9 87 97 7.0 9.2 5.0 9.2 20 4.8 115 3.3 983 997 317 0.6 3.3 Sun and showers all day
16 1.2 9.7 -0.7 90 99 7.0 9.2 0.8 8.8 16 0.9 23 4.5 997 1002 313 0.7 3.3 Sun & showers.
17 2.4 10.2 -0.3 79 99 6.9 9.2 1.8 7.1 15 2.5 60 5.8 999 1007 328 0.8 4.0 Sunny intervals all day
18 2.0 9.4 -0.7 84 99 6.9 9.2 1.3 7.8 19 1.4 33 0.8 1006 1019 286 0.8 4.0 Sunny intervals all day
19 5.9 11.3 1.6 88 99 6.9 9.2 2.7 11.1 23 5.5 131 16.5 1007 1018 68 0.0 0.0 Rain and drizzle all day
20 6.5 11.7 2.8 95 99 8.1 9.2 6.0 11.5 27 4.3 111 21.8 996 1007 80 0.5 0.0 Rain and drizzle all day
21 1.6 9.1 -0.3 97 100 8.2 9.3 1.2 9.1 15 0.3 8 2.3 1004 1015 205 0.7 3.6 Sunny ints, rain evening.
22 7.3 13.4 6.8 94 100 8.2 9.4 8.0 12.9 22 6.7 160 29.3 1002 1014 75 0.5 0.0 Rain, intermittent all day
23 9.3 13.4 7.4 84 97 9.0 9.4 7.3 12.4 24 4.1 98 0.8 1002 1007 117 0.5 0.5 Sunny ints am, cloudy pm
24 8.3 12.1 7.1 87 99 9.3 9.6 7.7 11.5 32 4.6 101 10.0 994 1007 224 0.7 1.3 Rain am, sunny intervals pm
25 6.8 11.6 2.2 74 98 9.3 9.8 4.9 8.2 25 4.1 97 3.0 990 1003 363 0.8 5.0 Sunny intervals all day
26 4.7 11.2 0.6 82 98 8.9 9.9 3.8 10.3 23 4.1 98 7.3 1002 1010 76 0.0 0.0 Cloudy am, rain pm
27 6.8 10.1 1.6 77 96 8.7 10.0 4.4 7.9 28 4.7 112 6.8 999 1020 335 0.8 4.8 Showers am, sunny ints pm
28 5.3 12.4 3.9 89 99 8.7 10.0 4.3 11.2 29 6.6 158 2.5 1012 1021 73 0.6 0.0 Drizzle am, cloudy pm
29 7.4 12.4 3.3 83 98 9.2 10.0 4.2 10.8 40 11.7 281 11.8 999 1012 115 0.5 0.8 Rain am, sunny intervals pm
30 4.3 10.9 0.7 81 96 9.2 10.1 3.3 9.1 22 5.2 124 3.3 1005 1015 288 0.7 1.3 Showers am, sunny ints pm
31 9.2 11.4 5.6 87 97 9.2 10.2 7.2 10.5 30 9.0 219 10.0 999 1014 36 0.0 0.0 Rain am, cloudy pm
3.8 9.8 0.5 82 98 8 9.9 2.1 8.0 20 3.6 2699 168.3 1004 1015 218 0.6 83  

Graphs for December 2012

Figure 1. Temperature and Rainfall for December 2012.
Figure 2. Sunshine, UV Index and solar irradiance for December 2012.
Figure 3. Wind direction for December 2012.
Figure 4. Soil & Sea surface temperature for December 2012.
Figure 5. Mean wind speed, calm hours and air pressure for December 2012.